Cardiothoracic Manual for Perioperative Practitioners 1905539487, 9781905539482

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Cardiothoracic Manual for Perioperative Practitioners

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Cardiothoracic Manual for Perioperative Practitioners

Editor: Dr Bhuvaneswari Krishnamoorthy Sub-editors: Mrs Jean Hinton and Professor Nizar Yonan

All profits from this book will be donated to support the widening of educational opportunities for low-income students.

Cardiothoracic Manual for Perioperative Practitioners Dr Bhuvaneswari Krishnamoorthy ISBN: 978-1-905539-48-2 First published 2020 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior permission of the publishers or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency, 90 Tottenham Court Road, London, W1T 4LP. Permissions may be sought directly from M&K Publishing, phone: 01768 773030, fax: 01768 781099 or email: [email protected] Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages.

British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Notice Clinical practice and medical knowledge constantly evolve. Standard safety precautions must be followed, but, as knowledge is broadened by research, changes in practice, treatment and drug therapy may become necessary or appropriate. Readers must check the most current product information provided by the manufacturer of each drug to be administered and verify the dosages and correct administration, as well as contraindications. It is the responsibility of the practitioner, utilising the experience and knowledge of the patient, to determine dosages and the best treatment for each individual patient. Any brands mentioned in this book are as examples only and are not endorsed by the publisher. Neither the publisher nor the authors assume any liability for any injury and/or damage to persons or property arising from this publication.

To contact M&K Publishing write to: M&K Update Ltd · The Old Bakery · St. John’s Street Keswick · Cumbria CA12 5AS Tel: 01768 773030 · Fax: 01768 781099 [email protected] www.mkupdate.co.uk Designed and typeset by Mary Blood Printed in Scotland by Bell & Bain, Glasgow

Contents Foreword vii Preface ix Acknowledgements x Contributors xi Abbreviations xv 1 Healthcare professional roles within the operating room 1 Mrs Jean Hinton 2 Legal and ethical implications in the perioperative area 29 Mr Richard Thompson and Dr Bhuvaneswari Krishnamoorthy 3 Operating theatre preparation for cardiothoracic surgical procedures 43 Mrs Teresa Hardcastle and Mr Bibleraj Gnanasekaran 4 Cardiac and thoracic anatomy 57 Mr Andrew Brazier and Mrs Charlene Tennyson 5 Preoperative assessment in cardiothoracic surgery 87 Mr Mohamed Ahmed Ghazi Suliman and Mr Roberto Mosca 6 Coronary artery disease 105 Mr Vipin Mehta, Mrs AnneMarie Brunswicker and Dr. Bhuvaneswari Krishnamoorthy 7 Aortic valve disease and aortic valve surgery 127 Mr Marcus Taylor and Mr Rajamiyer Venkateswaran 8 Mitral valve disease and mitral valve surgery 141 Mr James Barnard 9 Cardiopulmonary bypass 159 Dr Rob Bennett, Mr Simon Colah, Mrs Lindsay Mclean and Mr Andrew Wallhead 10 Surgery for aortic root disease 193 Miss Caroline Toolan, Mr Omar Nawaytou and Professor Aung Oo 11 Thoracic surgery 217 Mr Asghar Nawaz, Mr Piotr Krysiak, Mr Rajesh Shah and Dr Bhuvaneswari Krishnamoorthy

12 Cardiothoracic critical unit postoperative care 239 Dr Alan Ashworth and Dr Fiona Wallace 13 Responsibilities of the post anaesthetic care unit practitioners and enhanced recovery 273 Mrs Denise Walker 14 Overview of advanced practice in cardiothoracic surgery 307 Mrs Linda Nesbitt 15 Congenital cardiac surgical procedures 333 Dr Georgios Kalarouziotis 16 Step by step cardiac surgical procedure with instrumentation 387 Dr Bhuvaneswari Krishnamoorthy and Mr Janesh Nair 17 Transcatheter aortic valve implantation 419 Dr. Anthony D Pisaniello 18 Transcatheter mitral valve implantation 443 Dr Mamta Buch

Index 455

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Foreword This book is aimed at theatre practitioners, surgical first assistants, recovery practitioners, operating department practitioners, surgical care practitioners, advanced nurse practitioners and perfusionists, all of whom are vital members of the cardiothoracic multidisciplinary team. The book lays down the foundations of underpinning knowledge required for the different cardiothoracic perioperative practitioners’ roles. It also enables students and junior staff to explore the different roles and responsibilities available to them in the field of cardiothoracic surgery. Theatre staff used to be given a graduated training in the theatre environment in order to meet the needs of surgeons and the different surgical procedures. Traditionally, students and junior staff began with minor and intermediate surgical procedures, and then progressed to major surgery to develop their skills appropriately. However, due to current pressures on healthcare services, junior staff can now sometimes find themselves assisting with major and complex cases. This can be challenging but training and education are key to alleviating their anxieties. In addition, active participation increases surgical interest and gives junior staff more confidence in acting as the patient’s advocate. This book provides an excellent introduction to the ways in which healthcare professionals can influence the perioperative environment and ensure it is fit for purpose. The relevant aspects of anatomy, physiology and pathophysiology are included to support the reader in understanding the context of certain surgical procedures. The book also gives the perioperative practitioner an understanding of the development strategies and career opportunities available to them within cardiothoracic surgery. By navigating through the key aspects of the patient’s journey (from preoperative assessment to postoperative recovery in intensive care and the ward, through to discharge), the book adds value for the reader. It promotes the concept of holistic care, and highlights the importance of multidisciplinary team working, at every stage of the patient’s journey. This book is a valuable resource for the cardiothoracic community, encompassing all the perioperative roles and informing the reader of the context and knowledge required to deliver high-quality patient care. Patients remain at the forefront of our clinical practice. The content of this book reflects the achievements of the last 25 years for the cardiothoracic multidisciplinary surgical team. It is a marker of where we stand in 2020 on that journey. Mr Simon Kendall President Elect SCTS GB&I Mrs Tara Bartley OBE, Ex AHP lead for SCTS GB&I Simon Kendall completed his medical training at the Middlesex Hospital Medical School in 1984 and trained in cardiothoracic surgery in Leeds, Manchester, Papworth and Oxford. In 1993 he was appointed as a consultant at South Tees and has been one of the most productive UK cardiac surgeons, treating over 6,500 patients. He has enjoyed a career focused on multi-professional training, and has also served as the regional Training Programme Director and on the national

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Specialist Advisory Committee for Cardiothoracic Surgery. His commitment to the profession was recognised in 2012 when he became the first UK surgeon to be presented with the European Da Vinci Award for excellence in training. Since 2009, he has been an examiner for the Intercollegiate Specialty Examination. Tara Bartley is currently Corporate Advanced Clinical Practice Lead and Lead Advanced Nurse Practitioner Cardiac Surgery, Brighton and Sussex University Hospitals NHS Trust and Western Hospitals Foundation Trust. She also works as the Lead Advanced Nurse Practitioner, Cardiac Surgery, at Queen Elizabeth Hospital, Birmingham. Tara received a Fellowship of the Royal College of Nursing in 2011 and was made an Officer of the Order of the British Empire in the New Year’s Honours List of 2014.

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Preface Cardiothoracic surgery is constantly evolving and there are many textbooks available that help to highlight new evidence and practice. However, most of these books are written for surgeons and anaesthetists and many of them tend to omit important areas of surgical practice. This book is aimed at all perioperative practitioners, including surgical care practitioners, surgical cardiothoracic trainees, anaesthetic trainees, anaesthetic practitioners, recovery practitioners, ward advanced nurse practitioners and perfusionists. The contributors acknowledge that it is vital for any perioperative practitioner who wants to start a career in cardiothoracic surgery to understand surgical procedures step by step. This book therefore aims to cover all aspects of cardiothoracic surgery, with an emphasis on the individual role played by each member of the theatre team. Details will be provided throughout, including the initial theatre set-up and surgical instrumentation selection. A step-by-step walkthrough of routine surgical procedures, cardiopulmonary bypass guidance, investigations undertaken during the intraoperative period and detailed surgical anatomy background will be included. The book will also look at the recovery of the patient, as well as common pitfalls in surgery and recovery and how these can be avoided. The structure and organisation of the theatre environment, ethical and legal issues, preventive and protective measures and the importance of swab counts will all be explained succinctly and systematically by experts in the field, giving the reader reliable and complete guidance and preparing them to work efficiently and effectively in the theatre environment. All the chapters are written by experienced practising surgeons, anaesthetists and surgical theatre practitioners, and the entire book is fully supported by references for further reading and greater in-depth study.

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Acknowledgements I am grateful to the contributors who have taken the time to write chapters in this book. Their knowledge and experience add value to their contributions. I would also like to thank the subeditors who have expended time and effort going through all the chapters, checking them for consistency and content. I would like to thank medical illustrator Mrs Helen Carruthers who drew some of the images in Chapters 10 and 12. I would also like to thank Mrs Sameera Naz-Thomas (for the case study in Chapter 13), Mrs Maxine Read (who proof-read Chapter 2) and Mrs Tara Bartley (who proof-read Chapter 14). This book is dedicated to the educational charity at Edge Hill University. All the money will be donated to charity and none of the editors or authors will receive any payment. Finally, I would like to thank M&K Publishing for their patience and hard work during the period leading up to the publication of this book for perioperative practitioners.

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Contributors Editor Dr Bhuvaneswari Krishnamoorthy BSc (Hons), DNDM, PGDip RCS, NMP, MPhil, PhD, SFHEA, PFHEA, FFPCEd Dr Bhuvaneswari Krishnamoorthy is a Lead SCP in cardiothoracic surgery with 19 years’ experience, Programme Director for MSc in surgical practice, NIHR research fellow and President of Association of Cardiothoracic SCP. She runs a variety of cardiothoracic surgical courses for surgical trainees and qualified health professionals to keep their continuous professional development up to date. Her approach is based on structured training, in a peaceful, learningconducive environment, and she strongly believes in ‘Better training, better care for the future’. Her aim in writing this book is to support surgical trainees, surgical care practitioners, nurses and other allied health professionals who are undergoing training in cardiothoracic surgery.

Subeditors Mrs Jean Hinton RGN, Dip Management, BA (Hons), PGCE, MA Mrs Jean Hinton was employed by Edge Hill University in 2002, initially as a Senior Lecturer and then as a Programme Leader on the Pre-registration Operating Department Practice programmes and the Continuing Professional Development Perioperative modules. In 2014, Jean worked with the Royal College of Surgeons and other colleagues to develop the new national curriculum for Surgical Care Practitioners (SCPs), which she used to plan and develop the SCP Masters’ degree. Jean retired from full-time work as Programme Leader in January 2016. Since then, she has worked as an associate tutor for the SCP programmes. Professor Nizar Yonan MBChB, FRCS (CTh), MD Professor Nizar Yonan was a retired Cardiac Research Lead at the Manchester Foundation Trust and a Consultant Cardiothoracic and Transplant Surgeon before retiring in 2017. He was also the director of the Manchester Cardiothoracic Transplant Programme and the co-director of the Transplant Research Laboratory. He was a member of the editorial board for the Journal of Cardiac Surgery and an examiner for the Royal College of Surgeons of Edinburgh, as well as a member of the cardiac and pulmonary councils for the International Society for Heart and Lung Transplantation and an invited adviser for the Department of Health and UK Transplant.

Authors Dr Alan Ashworth MBChB, FRCA, FFICM Dr Alan Ashworth is a Consultant Anaesthetist in Cardiac Anaesthesia & ITU at Wythenshawe Hospital. Mr James Barnard BSc, MBChB, MD, FRCS (CTh) Mr Barnard is a Consultant Cardiac and Cardiothoracic Transplant Surgeon who works at South Manchester University Hospital NHS Trust. He performs the full range of adult cardiac surgery

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procedures and his areas of specialist interest are mitral valve repair surgery, major aortic surgery, heart transplantation and lung transplant surgery. Dr Rob Bennett BSc (Hons), PhD, CCP Dr Rob Bennett is a Senior Clinical Perfusion Scientist at Castle Hill Hospital and he is also an Honorary Research Fellow at Hull York Medical School in Hull. Mr Andrew Brazier BSc (Hons), MBChB, MRCS Andy completed a combined medical degree through the universities of St Andrews and Manchester in 2010. He has been working in cardiothoracic surgery since 2012 and currently works as a Senior Clinical Fellow at Wythenshawe Hospital in Manchester, UK. Mrs Annemarie Brunswicker Medicine from Germany, MD, MRCS Annemarie Brunswicker completed her medical training in Bochum, Germany, following Core Surgical Training at the Norfolk and Norwich University Hospital and the Royal Papworth Hospital. She is currently a Specialty Trainee in Cardiothoracic Surgery in the North-West. Dr Mamta Buch MBChB, PhD, FRCP Dr Mamta H Buch (MBChB, PhD, FRCP) is a Consultant Interventional Cardiologist, Structural and Coronary, at Manchester University NHS Foundation Trust (MFT). She is clinical lead of transcatheter heart valve services at Wythenshawe Hospital, MFT. She is a member of the British Cardiovascular Intervention Society Structural Heart Working Group, British Heart Valve Society Council and British Cardiovascular Society Guidelines & Practice committee. She is involved in policy development and producing service delivery recommendations for heart valve disease management. Mr Simon Colah MSc Simon trained at St George’s Hospital, Tooting. After qualifying as a perfusionist, he spent 9 years in the USA and became a Certified Clinical Perfusionist (CCP). On his return to the UK, Simon took a post with CPS at Papworth Hospital, where he focused on short-term ventricular assist devices (VADS), extracorporeal membrane oxygenation (ECMO) and transplantation. He has co-written chapters in books on heart surgery and co-authored multiple articles in academic journals. Mr Bibleraj Gnanasekaran BSc (Hons), Dip ODP Raj works at Manchester Royal Infirmary (MRI) as an Operating Department Practitioner, where he assists in ICD extractions, pacemakers, SICD, Tavistock and other adult congenital heart disease procedures with 30 years’ experience. His detailed knowledge of cardiothoracic surgery is highlighted in his chapter on cardiothoracic theatre set-up. Mrs Teresa Hardcastle RGN, RSCN, OND, MA, SFA Teresa became Programme Leader for both the Pre-registration BSc (Hons) Operating Department Practice programme and MSc Surgical Care Practice at Edge Hill University in 2016. She retired from full-time work as a Programme Lead in 2018 but has continued to work as an associate tutor for the MSc SCP programme and SFA modules. She is particularly interested in the recognition, future training and regulation of all advanced practitioners. Dr Georgios Kalavrouziotis MD, PhD Georgios is a Senior Consultant (2016 to date) at the Department of Paediatric Cardiothoracic Surgery at ‘AGHIA SOPHIA’ Children’s Hospital in Athens. He has published 20 papers in peerreviewed international journals and presented 70 abstracts in international medical meetings. He has also given 40 invited talks on national and international medical activities.

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Mr Piotr Krysiak FRCS (Ed) Piotr is a full-time Thoracic Surgeon in Manchester performing general thoracic surgery (mainly lung cancer surgery and lung transplantation). He has developed an interest in difficult airway management and has been involved with introducing new techniques in thoracic surgery and transplantation. He is also involved with postgraduate teaching and acts as a regional tutor for the Royal College of Surgeons in England and Ireland. Mrs. Lindsay Mclean CertEd, ACP Mrs. Lindsay Mclean is Chief Clinical Perfusion Scientist at Castle Hill Hospital. Mr Vipin Mehta MD Vipin Mehta is a locum Consultant Cardiac and Aortic Surgeon at Liverpool Heart and Chest Hospital. His areas of interest are coronary surgery, aortic surgery (including aortic valve surgery, arch, root and thoracoabdominal aneurysms), heart failure and transplantation. Dr Roberto Mosca MD Dr Mosca is Consultant Anaesthetist in Wythenshawe Hospital for 10 years. He is the Lead for Transplantation, Thoracic Surgery, Intraoperative TOE and Anaesthetic Equipment. Mr Janesh Nair DNDM, BSc, PGDip RCS, NMP Janesh Nair is a Senior Surgical Care Practitioner at Wythenshawe Hospital, Manchester, UK. He has 21 years’ experience’ in a cardiothoracic surgery department and ten years as a Surgical Care Practitioner. He has previously worked at the Amrita Institute of Medical Sciences in India. Mr Omar Nawaytou MBChB, FRCS Omar is a consultant Cardiac and Aortic Surgeon in the Liverpool Heart and Chest Hospital. He was HRUK Fellow in Aortic Surgery and an LHCH Ethicon Fellow in Valve Repair. He has worked at St Luc Hospital in Brussels and NTN CTS Wales/West Midlands Hospital. Mr Asghar Nawaz MRCS, FCPS, FRCS (CTh) Mr Asghar Nawaz is a Senior Specialist Registrar (ST8 NTN) in Cardiothoracic Surgery in the North West, with a special interest in minimally invasive and robotic surgery. He recently travelled to Shanghai to learn uniportal surgical techniques. Asghar has presented his work at various national and international meetings, including SCTS, ASCVTS, ISMICS and AATS. Mrs Linda Nesbitt RGN, BSc, SPQ, MSc, NMP Linda Nesbitt is currently Lead for Advanced Practice and Non-Medical Prescribing at the Golden Jubilee National Hospital in Glasgow. She is currently a representative on the national group reviewing and transforming Advanced Practice roles in Scotland and co-chair of the Scottish National Non-Medical Prescribing Leads Group. Professor Aung Ye Oo MBBS, MD, FRCS (CTh) Professor Aung Ye Oo was appointed Clinical Lead for Aortovascular Surgery at Bart’s Heart Centre, St Bartholomew’s Hospital, and Professor of Cardiovascular Surgery at William Harvey Research Institute at Queen Mary University of London in 2017. He has published many times in world-renowned journals and contributed to books related to aortic surgery. He is also committed to regular charity missions operating and training in cardiac and aortic surgery in Myanmar, Vietnam and India. Dr Anthony D. Pisaniello MBBS FRACP PhD Dr Anthony Pisaniello is an academic interventional cardiologist who trained in Australia. He has expertise in transcatheter aortic valve implantation (TAVI), which is the focus of his clinical and

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research interests. He is based at Manchester Royal Infirmary, UK. Mr Rajesh Shah MBBS, MS, FRCS (Ed), FRCS (Glasgow), FRCS (C/Th), FECTS (European Board) Rajesh is a Consultant Thoracic and Transplant Surgeon at the Department of Cardiothoracic Surgery, Wythenshawe Hospital. He has been Clinical Director for Cardiothoracic Surgery and Academic Lead for Thoracic Surgery since 2013. He has developed an interest in surgical education and was appointed as a Specialty Advisory Committee (SAC) Chair while working as an Education Secretary for the SCTS. He is an examiner for both the national and international FRCS (C/TH) exams. Dr Mohamed Ahmed Ghazi Suliman BMedSci (Hons), BMBS, DTM&H, MRCP, FRCA Dr Suliman is an Advanced Fellow in cardiothoracic anaesthesia and intensive care. His interests are in congenital cardiac anaesthesia, extracorporeal membrane oxygenation (ECMO) and acute care echocardiography. Mr Marcus Taylor MBChB, MRCS, MSc Mr Marcus Taylor is a Speciality Trainee in Cardiothoracic Surgery in Manchester, UK. He has published and presented nationally and internationally on a range of topics and maintains an interest in both undergraduate and postgraduate teaching. Mr Richard Thompson BSc (Hons), PGDip RCS, ALS Mr Richard Thompson is a qualified nurse, Surgical Care Practitioner (SCP) and Cardiac Chair for the Association of Cardiothoracic SCPs. For the last 10 years, Richard has worked as a practitioner in theatres, assisting in adult cardiothoracic surgery. Prior to this, Richard worked as an intensive care nurse, spending a total of 27 years in nursing. He has experienced all levels in nursing, from auxiliary to matron. Miss Caroline Toolan MBChB, FRCS Caroline is ST7 Cardiothoracic Surgery Trainee in North West Deanery. She has a huge involvement in the Society of Cardiothoracic Surgery (SCTS). Mr Rajamiyer Venkateswaran MS, MD, FRCS (CTh) Mr R.V. Venkateswaran is a Consultant Cardiac and Cardiothoracic Transplant Surgeon who works at the Manchester Foundation Trust, UK. He performs the full range of adult cardiac surgery procedures and his areas of specialist interest are mini aortic valve surgery, mitral valve surgery, heart and lung transplant surgery and mechanical circulatory support. Mrs Denise Walker RN, BA, PGCTHE Denise has 30 years’ clinical experience in the field of anaesthetics, recovery and intensive care. In 2013, She joined the perioperative teaching team at Edge Hill University, as a senior lecturer, teaching both pre-registration operating department practitioners and post-registration nurses undertaking the anaesthetic and recovery modules. Dr Fiona Wallace MBChB, FRCA, FFICM Fiona Wallace is a Consultant in Intensive Care Medicine and Anaesthesia at Salford Royal Foundation Trust. She trained in cardiothoracic critical care at the University Hospital of South Manchester, UK. Her interests include neuro and trauma critical care, focused echocardiography and wellbeing. Mr. Andrew Wallhead BSc (Hons), PGDip, ACP Mr. Andrew Wallhead is Senior Clinical Perfusion Scientist at Castle Hill Hospital.

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Abbreviations AAGBI Association of Anaesthetists of Great Britain and Ireland ABCDE Airway, Breathing, Circulation, Disability, Exposure Assessment AC aortic cannula ACCF American College of Cardiology Foundation ACCP advanced critical care practitioner ACE angiotensin-converting enzyme ACORN Australian College of Operating Room Nurses ACS acute coronary syndrome ACT activated clotting time AF atrial fibrillation AHA American Heart Association AHRF acute hypercapnic respiratory failure ANA American Nurses Association ANP advanced nurse practitioner ANT antiseptic non-touch technique APB arterial blood pressure ARDS acute respiratory distress syndrome AS aortic stenosis AscAo ascending aortic (aorta) ASD atrial septal defect ATP assistant theatre practitioner AV atrioventricular AVA aortic valve area AVR aortic valve repair BAV balloon aortic valvuloplasty BAVD bicuspid aortic valve disease BP blood pressure BSA body surface area BTS British Thoracic Society BTS1 Blalock-Taussig Shunt CABG coronary artery bypass grafting CAD coronary artery disease CALS cardiac advanced life support CC cardioplegia catheter CHD congenital heart disease CHF congestive heart failure CMR cardiac magnetic resonance CNA Canadian National ANP COA coarctation of the aorta

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CO2 carbon dioxide COPD chronic obstructive pulmonary disease COAPT Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Trial CPAP continuous positive airway pressure CPB cardiopulmonary bypass CPR cardiopulmonary resuscitation CRM crew resource management CRNA certified registered nurse anaesthetist CRP C-reactive protein CRT cardiac resynchronisation therapy CS coronary sinus CSFA certified surgical first assistant CT computed tomography CVA cerebrovascular accident CVP central venous pressure CXR chest X-ray DCA Department of Constitutional Affairs DescAo descending aorta DH Department of Health DHCA deep hypothermic circulatory arrest DLCO capacity of the lungs for carbon monoxide DMR degenerative mitral regurgitation ECG electrocardiogram ECLS extracorporeal life support ECMO extracorporeal membrane oxygenation ESC European Society of Cardiology ETCO2 partial pressure of carbon dioxide at the end of an exhaled breath ETT endotracheal tube EuroSCORE European system for cardiac operative risk evaluation FEV forced expiratory volume FG French gauge fraction of oxygen FiO2 FMR functional mitral regurgitation FRACS Fellow of the Royal Australasian College of Surgeons FREEDOM Future Revascularisation Evaluation in Patients with Diabetes Mellitus – Optimal Management of Multivessel Disease GDMT guideline-directed medical therapy GI gastrointestinal GMC General Medical Council

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GSV greater saphenous vein HCA health care assistant HCPC Health and Care Professionals Council HCT haematocrit HDU high dependency unit HF heart failure HLM heart lung machine HVT heart valve team IABP intra-aortic balloon pump IBM International Business Machines Corporation ICN International Council for Nurses ICS intercostal space ICU intensive care unit IMA internal mammary artery InV innominate vein IV Intravenous IVC inferior vena cava IVS intact ventricular septum LAD left anterior descending artery LCA left coronary artery LDL low-density lipoprotein LIMA left internal mammary artery LMA laryngeal mask airway LPA left pulmonary artery LSA left subclavian artery LSV left subclavian vein LV left ventricular LVEF left ventricular ejection fraction LVOT left ventricular outflow tract MAP mean arterial pressure MBTS modified Blalock-Taussig shunt MCAT The Medical College Admissions Test MCNZ Medical Council of New Zealand MDT multidisciplinary team MDCT multidetector computed tomography MITRA-FR Multicentre Study of Percutaneous Mitral Valve Repair MitraClip Device in Patients with Severe Secondary Mitral Regurgitation MPA main pulmonary artery MR magnetic resonance MR2 mitral regurgitation

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MRI MRSA MS MSSA MV MVD MVR NCF NES NHS NICE NIRS NIV NMC NPSA NOACs NRLS NSTEMI NYHA ODP OPCAB PCC PA PACU PaO2 PAOP PAP PAPVR PARTNER PBA PBMV PCA PCI pCO2 PDA PDA1 PEEP PET PFO PFT

magnetic resonance imaging methicillin-resistant staphylococcus aureus mitral stenosis methicillin-sensitive staphylococcus aureus mitral valve mitral valve disease mitral valve replacement National Critical Care Framework NHS Education for Scotland National Health Service National Institute for Health and Care Excellence near-infrared spectroscopy non-invasive ventilation Nursing and Midwifery Council National Patient Safety Agency non-vitamin K antagonist oral anticoagulants National Reporting and Learning System non-ST segment elevation myocardial infarction New York Heart Association operating department practitioner off pump coronary artery bypass perioperative care collaborative physician assistant post-anaesthetic care unit partial pressure of oxygen in arterial blood. pulmonary artery and occlusion pressures pulmonary artery pressure partial anomalous pulmonary venous return Placement of AoRTic TraNscathetER Valve Trial pulmonary artery banding percutaneous balloon mitral valvotomy patient-controlled analgesia percutaneous coronary intervention partial pressure of carbon dioxide posterior descending artery patent ductus arteriosus positive end-expiratory pressure positron emission tomography patent foramen ovale pulmonary function test

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pH a figure expressing the acidity or alkalinity of a solution PICC pulse contour cardiac output PO2 partial pressure of oxygen POCD postoperative cognitive dysfunction PpoFEV predicted postoperative forced expiratory volume PpoVO2 predicted postoperative oxygen uptake PQR complex represents the depolarisation (activation) of the ventricles PTFE polytetrafluoroethylene PVC polyvinyl chloride PV pulmonary vein PV1 pulmonary valve PVR pulmonary valve replacement RA right atrium RA-IVC inferior vena cava cannula via the RA RBBB right bundle branch block RCA right coronary artery RCN Royal College of Nursing RCOA Royal College of Anaesthetists RCS Royal College of Surgeons RCSEd Royal College of Surgeons of Edinburgh RCSEng Royal College of Surgeons, England RCSI Royal College of Surgeons in Ireland RCT randomised control trial RCUK Resuscitation Council UK RMBTS right modified Blalock-Taussig shunt RN registered nurse ROTEM rotational thromboelastometry RPA right pulmonary artery rSO2 regional oxygen saturation RV right ventricle or ventricular RVOT right ventricular overflow tract SA sinoatrial SAVR surgical aortic valve replacement SBAR Situation, Background, Assessment and Recommendations SCA subclavian artery SCP surgical care practitioner SCPC superior cavo-pulmonary connection SCTS Society for Cardiothoracic Surgery in Great Britain and Ireland SFA surgical first assistant SHOT serious hazards of transfusion

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SIRS systemic inflammatory response syndrome SpO2 blood oxygen saturation STEMI ST segment elevation myocardial infarction SVC superior vena cava TAVI transcatheter aortic valve implantation TAVR transcatheter aortic valve replacement TEG thromboelastography TGA transposition of the great arteries TMVI transcatheter mitral valve implantation TMVR transcatheter mitral valve replacement TNR Transforming Nursing Roles TOE transoesophageal echocardiogram TOF tetralogy of Fallot TV tricuspid valve TTE transthoracic echocardiogram TV tricuspid valve UK United Kingdom USA United States of America VA veno-arterial VAD ventricular assist device VAP ventilator-associated pneumonia VATS video-assisted thoracoscopic surgery VCO2 carbon dioxide production ViMAC valve-in-mitral annular calcification ViR valve-in-ring ViV valve-in-valve VO2 oxygen uptake VO2 Max maximum oxygen uptake VSD ventricular septal defect VV veno-venous WHO World Health Organisation

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1 Healthcare professional roles within the operating room Jean Hinton

Introduction This chapter focuses on the individual roles and professions that make up the perioperative multidisciplinary team (MDT) working in cardiothoracic theatres nationally and internationally. This chapter covers training and education in the UK, the USA, Australia and New Zealand for each of the different roles within the MDT. European countries have slightly different requirements in terms of level and standard of training. However, although titles and roles may differ from one country to another, there are many similarities in training, and the skills and knowledge required are comparable.

Background One of the main aims of perioperative team work is to develop and maintain a culture of safe, good-quality care in order to reduce any potential patient harm within the perioperative environment and beyond. To ensure the maximum safety of surgical patients within the perioperative environment, multidisciplinary teamwork is key in delivering best practice and optimum patient care. Teamwork has been recognised as a vital aspect of healthcare practice. In the UK, prior to the establishment of the National Health Service (NHS) and as early as 1920, the Dawson Report suggested that working together as a team was the most productive way forward for primary care (Colin-Thormé et al. 2016). A report issued by the International Association of Physicians in Aids Care (IAPAC 2011) describes the MDT as ‘a partnership among healthcare workers of different disciplines inside and outside the health sector and the community with the goal of providing quality continuous, comprehensive and efficient health services’. In addition, according to Tang and Hsiao (2013, p.1) ‘Multidisciplinary collaboration means a team consisting of members with different professional backgrounds and skills that can compensate each other and work together toward the same direction to achieve the same goals’. Working as a team is important in all aspects of primary, clinical and emergency care. However, the operating theatre is unique among healthcare settings in that it requires all members of

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Cardiothoracic Manual for Perioperative Practitioners

the multidisciplinary team to be present at the same time, working together to treat patients requiring anaesthetic and surgical interventions. No single discipline can work in isolation within the perioperative environment; they all rely on each other’s expertise and knowledge to deliver successful patient outcomes. In the current global healthcare climate, with increasing technical innovations, financial constraints and the challenges of caring for aging populations, healthcare services are under unprecedented pressure. Protecting patients from avoidable harm is a paramount goal internationally and the World Health Organisation’s Surgical Checklist is an example of a global initiative for emergency and essential surgical care. It promotes safer surgery and is made up of different phases, corresponding to specific stages in the perioperative process. This checklist is used internationally. Whilst there are local, regional, national variances and additions, the original version included three main areas (WHO 2009): 1. ‘Sign in’ before the induction of anaesthesia 2. ‘Time out’ before the incision of the skin 3. ‘Sign out’ before the patient leaves the operating room. As a result of feedback following the implementation of the WHO Surgical Checklist, the Five Steps to Safer Surgery were introduced in 2010 (WHO 2016). Two phases were added to the original checklist: the team brief (held at the beginning of the operating list) and the debrief (held at the end of each operation). At the end of each phase the designated leader signs off and confirms that all the listed tasks (such as correct identification of site of operation, prior to commencing the incision) have been completed (WHO 2016). The WHO Surgical Checklist is one of the methods introduced to reduce the incidence of ‘adverse events’ or ‘never event’ reporting. ‘Never event’ is the term used in the UK and defined by NHS Improvement (2018, p. 4): Never Events are defined as Serious Incidents that are wholly preventable because guidance or safety recommendations that provide strong systemic protective barriers are available at a national level and should have been implemented by all healthcare providers. It is therefore the MDT’s responsibility, through training and education, to ensure that these ‘never events’ are kept to a minimum and, where possible, eradicated.

The non-medical surgical team Operating room personnel are key to the outcomes of all patients undergoing surgical procedures. They mainly spend their time working within the perioperative area, preparing the environment and instrumentation, and caring for the patients before, during and after their surgical procedures. The roles and responsibilities of operating room personnel are highlighted below. Together with non-medical specialists and medical staff, operating room personnel make up the MDT, who collectively ensure the best practice is followed and the safety of surgical patients remains paramount.

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Healthcare professional roles within the operating room

The operating room personnel: ●●

Provide effective management of the operating theatres/suites

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Communicate with all departments and staff via the MDT

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Maintain and update staff training, and education as needed for their role

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Maintain and provide appropriate operating theatre resources

Maintain and provide all operating theatre equipment and instrumentation, maintaining sterility as required.

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Anaesthetic practitioner In the UK, the anaesthetic practitioner can be either a qualified theatre nurse or a qualified operating department practitioner (ODP). The Association of Anaesthetists of Great Britain and Ireland (2010, p. 3) states that ‘Anaesthetists must have dedicated qualified assistance wherever anaesthesia is administered, whether in the operating department, the obstetric unit or any other area.’ The anaesthetic theatre nurse (or ODP) assists the anaesthetist in all aspects of the planning, delivery and maintenance of the cardiothoracic patient’s anaesthetic care. This care begins when the patient is admitted to the theatre area. There is then a handover of care from the ward nurse directly to the anaesthetic practitioner, or from the forward waiting team who have already accepted the patient from the ward. The anaesthetic care continues from the anaesthetic room, where the patient is anaesthetised, to the theatre, when they are transferred for the surgical procedure. The anaesthetic practitioner’s main responsibilities are to ensure the smooth running of the list from an anaesthetic perspective. This includes checking the availability of all equipment that may be needed, including emergency anaesthetic equipment, and performing the required preoperative checks thoroughly in both the anaesthetic room and the operating theatre before starting the list. During the anaesthetic phase, the anaesthetic practitioner assists the anaesthetist to maintain the patient’s airway, while constantly observing and monitoring the patient’s physical and physiological responses to the anaesthetic and surgery. This requires a high level of skill, underpinning knowledge and experience when caring for cardiothoracic patients who are undergoing a variety of procedures. These procedures will extend over a wide range of patient dependency and they could be major or minor procedures, and range from dire emergencies to elective surgery, covering all age groups. The anaesthetic practitioner usually holds the drug cupboard keys for their anaesthetic room and theatre, which means they are responsible for checking, recording and signing for controlled drugs, such as morphine and fentanyl. The anaesthetic practitioner will also organise and prepare any intravenous fluids prescribed by the anaesthetist and set up specialist monitoring equipment (such as arterial lines and central venous pressure lines) which is frequently used in major surgical cases. After surgery, the anaesthetic theatre nurse or ODP will hand care over to a recovery practitioner in the recovery room, a nurse on a high dependency unit, or a nurse on the intensive care unit, depending on the severity of the cardiac procedure and/or the patient’s state of health.

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Cardiothoracic Manual for Perioperative Practitioners

Some examples of the anaesthetic practitioner’s responsibilities include: ●●

Anaesthetic machines/ventilators Checking the anaesthetic machines and ventilators in both the anaesthetic room and theatre before commencing every theatre list.

●●

Modern anaesthetic machines have sophisticated, computerised controls incorporating a few modifications that enable the treatment of patients with complex and adverse anaesthetic issues.

●●

A fault occurring perioperatively with the anaesthetic machine or ventilator can be potentially life-threatening for the patient.

●●

●●

Airway management/intubation aids and items Airway management is crucial in ensuring a safe outcome for any patient undergoing general anaesthesia.

●●

●●

All equipment must be collected and checked prior to starting the list.

The anaesthetic practitioner has to anticipate any potential problems and have relevant supplementary/emergency equipment checked and present in the theatre should it be required.

●●

●●

Monitoring equipment Various types of monitoring equipment may be required during cardiothoracic surgery. The anaesthetic practitioner has to ensure that all monitoring equipment is cleaned, regularly calibrated and maintained in working order.

●●

Basic monitoring includes checks on blood pressure (non-invasive), temperature, respiratory rate, oxygen saturation and capnography (this measures the amount of CO2 the patient exhales).

●●

Depending on the type, length or comorbidities of a patient undergoing cardiothoracic surgery, the anaesthetic practitioner may have to prepare equipment to measure arterial blood pressure, central venous pressure and/or oesophageal Doppler ultrasonography to measure the cardiac output.

●●

In the USA, there is no equivalent to the anaesthetic support available in the UK. Instead, the registered nurse provides nursing care, assisting the anaesthesiologist during the delivery and with the maintenance of anaesthesia, the positioning of the patient, and all the documentation required for the surgical procedure. In Australia and New Zealand, the anaesthetic technician’s role is like that of an ODP or anaesthetic nurse. However, they are not currently registered, and the training is not uniform throughout these countries. In Europe, this role is carried out by the registered nurse and is not always considered a separate role. In some European countries, an anaesthetic nurse delivers the anaesthetic with an anaesthetist in the vicinity, but not under direct supervision.

Scrub practitioner The scrub practitioner can be a qualified theatre nurse, a qualified operating department practitioner or a theatre assistant practitioner.

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Healthcare professional roles within the operating room

The role of the scrub practitioner is predominantly to: ●●

Maintain and update their skills and knowledge

Check all the surgical equipment prior to starting the list, and ensure that all equipment is in working order and present in the operating theatre

●●

Maintain a strict scrubbing up regime, wearing surgical masks, goggles, sterile gowns and gloves appropriately

●●

Check for any patient allergies, gain consent for the operation and undertake the WHO Surgery Checklist (WHO 2016) before surgery commences

●●

Complete all counts with the circulating practitioner before the start of surgery, during the surgery as necessary and prior to final skin closure

●●

Manage the instruments and supplementary equipment required for the surgical team to perform the required cardiothoracic procedure in order to keep both the patient and the MDT team safe

●●

Maintain and monitor the sterile field and ensure the sterility of all instruments used (e.g. check that the sterile instruments sets have no obvious holes in their wrapping to avoid the risk of using unsterile or contaminated instruments during the procedure)

●●

Managing and account for all instruments, swabs, needles and sundries used in the surgical procedure

●●

Have a good understanding of the operative procedure in order to anticipate the needs of the surgical team as they progress through the surgical procedure

●●

Monitor and manage the circulating team, giving clear instructions and requests in a timely manner so as not to delay the surgical operating team

●●

Save and pass out to the circulating team any specimens needed, clearly and accurately identifying the specimen(s) for documentation purposes, and checking accuracy with the operating surgeon before the specimen(s) are documented and sent out of theatre

●●

Anticipate any potential complications and have equipment available, close at hand, should it be required.

●●

An important responsibility of a scrub practitioner is to ensure that all relevant information pertaining to a patient is accurately recorded on the relevant documentation within the patient’s notes. This is necessary for the safety of the patient and for legal purposes. In the USA, the registered nurse (RN) is responsible for providing safe and effective care for patients undergoing surgical procedures. This includes preoperative investigations, such as electrocardiogram, blood for cross matching and checking haemoglobin, urea and electrolytes to ensure the patients are fit and ready for surgery. The RN is responsible for ensuring the surgical theatre has everything necessary for the procedure (such as the appropriate instrumentation and surgical implants) and providing support to the surgical team by opening additional items as required during the surgical procedure.

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Cardiothoracic Manual for Perioperative Practitioners

In Australia, the practitioner undertaking the scrub role is referred to as the scrub nurse or instrument nurse. The role predominantly focuses on the sterility of the instruments, and accounting for the instruments, swabs and sharps provided for the surgical team. They scrub nurse must have a good working knowledge of each procedure in order to pass and retrieve instruments safely while managing the introduction and disposal of items in a timely manner.

Post-anaesthetic care unit or recovery practitioner In the UK, the recovery practitioner can be either a qualified nurse or a qualified operating department practitioner. The role of the recovery practitioner involves caring for patients individually, on a one-to- one basis. In cardiothoracic surgery this can include adults, children and patients with learning difficulties or other special needs. Smedley (2009) highlights the complexity and responsibility of the role and recognises the constantly changing priorities for the practitioner, requiring a high level of flexibility, knowledge and skill. The responsibilities of the recovery practitioner are varied and demanding. There are some similarities with the responsibilities of the intensive care unit (ICU) and high dependency unit (HDU) nurse, especially where the recovery practitioner is allocated to the resuscitation bay(s) found in some recovery areas. However, the ICU and HDU nurses are usually allocated one or two patient(s) for the whole shift, whereas the recovery practitioner is allocated many patients during their shift, who may have widely differing conditions, requiring the recovery practitioner’s knowledge, skills and competence. One of the recovery practitioner’s most important responsibilities is to check that all areas are fully equipped and clean before the patient arrives in the post-anaesthetic care unit (PACU) following their surgery. The main priority is to maintain the patient’s airway, as most patients (having received a general anaesthetic with muscle relaxants) will still be unable to maintain their own airway safely. This maintenance is required until the patient has fully reversed from the anaesthetic and is fully conscious. Some examples of the recovery practitioner’s responsibilities include: ●●

Monitoring Initially, five-minute checks on the patient’s respiratory rate, pulse rate, oxygen saturation, blood pressure and patient responses are crucial. The recovery practitioner needs to be vigilant in recognising any potential problems swiftly, as some can be life-threatening.

●●

●●

Pain management Constant monitoring of the patient’s pain threshold is required, and the recovery practitioner must manage the patient’s pain relief before they can go back to the ward.

●●

This means dealing with controlled drugs, knowing the contra-indications and how to manage adverse situations that could result from administering pain relief to a variety of patients.

●●

●●

Fluid maintenance Monitoring all fluid loss and intake throughout the recovery period, including urinary catheters, wounds and wound drains to ensure the patient is adequately hydrated.

●●

6

Healthcare professional roles within the operating room

●● ●●

Nausea and vomiting may occur postoperatively and must also be managed.

Mobility and perfusion The patient needs to be observed and monitored to ensure that they are gradually regaining their preoperative mobility and that their circulatory system is accurately perfusing their body, especially following cardiothoracic surgery.

●●

●●

Record-keeping Maintaining records of the care and treatment delivered to the patient during their recovery period.

●●

This is essential in order to carry out a comprehensive handover to the ward nurse, which ensures continuity of care.

●●

●●

Reassurance ●●

Patients are often distressed and disorientated when emerging from a general anaesthetic.

The recovery practitioner’s skill and calm manner can reassure the patient and provide a smoother, less stressful recovery experience.

●●

Assistant theatre practitioner (ATP) According to Skills for Health (2011, p.4): An Assistant Practitioner is defined as a worker who competently delivers health and social care to and for people. They have a required level of knowledge and skill beyond that of the traditional healthcare assistant or support worker. The concept of role expansion for healthcare assistants (HCAs) was first discussed in 2004 as a result of the NHS Changing Workforce Programme (DH 2000, 2001, 2002). Initially there was strong resistance to this concept; and the introduction of these roles in the operating theatre is still spasmodic, with some areas embracing the concept and others still resistant. The Perioperative Care Collaborative (2015) position statement has clearly identified the different roles from which ATPs are recruited, such as support worker, healthcare assistant and auxiliary nurse, in their caveat at the beginning of the document. The Perioperative Care Collaborative defines a healthcare support worker ‘as a non-registered staff member of the perioperative team’ (PCC 2015, p. 1). There is some confusion with HCAs, who have undergone a two-year foundation degree at a university, regarding their accountability and responsibilities within the perioperative team. However, as ATPs are non-registered staff, they are always expected to be supervised by a registered individual and certain checks must be undertaken with a registered professional. For example, an ATP cannot check swabs or instruments with another HCA; this task has to be performed with a registered practitioner (PCC 2015). The ATP’s role is therefore limited and must be practised within strict parameters. While some staff equate ATPs with State Enrolled Nurses, the key difference is that State Enrolled Nurses are registered nurses and their role therefore has a much wider remit than that of ATPs. When delegating tasks to ATPs or any unregistered healthcare worker, it is crucial that registered practitioners are aware and understand that they are still professionally accountable

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Cardiothoracic Manual for Perioperative Practitioners

for the appropriateness of the delegation of care. This requirement is explicit in both the Nursing and Midwifery Council (2015) Code of Professional Conduct: Standards of Conduct, Performance and Ethics and the Health and Care Professionals Council (2016) Standards of Conduct, Performance and Ethics. The PCC (2015, p. 2) position statement also highlights the fact that registered practitioners should understand that ATPs ‘are responsible in civil, criminal and contract law for their actions and thus are accountable to the patient and the employer’. All swab, instrument and needle counts must be conducted with a registered practitioner who is a member of the scrub team.

●●

The supervising registered practitioner should be present in the operating theatre for the duration of the operative procedure as part of the scrub team.

●●

A registered practitioner must ensure that the patient care record and other documentation have been completed satisfactorily by the ATP. Good practice would be for the registered practitioner to countersign all records completed by the ATP. ●●

The PCC (2015) emphasises that no support worker, HCA or auxiliary nurse should undertake any of these tasks unless they have undertaken training in line with the Perioperative Care Support and the Perioperative Care Surgical Support units of the National Occupational Standards for Perioperative Care and have been assessed via National Qualification Frameworks. In the USA, surgical technicians manage the surgical instruments during the procedure to assist the surgeon. This includes making sure that all necessary instruments and implants are present prior to the surgical procedure as well as preparing the operating room. In Australia, the operating room technician or technologist carries out similar duties to those of the surgical technician in the USA and the ATP in the UK.

Healthcare assistant Healthcare assistants (HCAs) work in all hospital departments, providing assistance to qualified healthcare practitioners, including nurses, ODPs, doctors and the wider multidisciplinary team (National Health Service Careers 2018a). In cardiothoracic theatres, the HCAs assist in providing safe and effective patient care and contribute to the smooth running of the operating list in a variety of ways. Their work is always supervised by qualified, registered staff who can delegate tasks to the HCAs, providing they have had adequate training and are competent to undertake any delegated task safely and efficiently. A negative factor that is often raised regarding HCAs is that they are untrained and unregistered. Although all HCAs should be able to access the Skills for Health competencies and be assessed as competent in carrying out any delegated skills, some managers do not provide access to this training for their workforce, or other factors prevent them accessing it. This can lead to a workforce with little or no standardisation of knowledge and skills, especially recognisable transferable skills. Nevertheless, HCAs remain an integral part of the perioperative multiprofessional team and their main duty is circulating for the surgical team. Without the skilled and efficient support of the circulating team, the effectiveness of the scrub team is undermined, which could detract

8

Healthcare professional roles within the operating room

from optimum patient care and safety. All members of the scrub team also undertake circulating duties. This is because it is imperative that a scrub practitioner knows where everything that could possibly be required for a full operating list, is located. There is also a theatre saying that ‘A good scrub practitioner is only as good as his/her circulating team/person’. Some examples of the perioperative HCA’s responsibilities include: ●●

●●

Chaperoning female patients in the anaesthetic room with a male anaesthetic team ●●

Patients arriving in a theatre department can be extremely nervous.

●●

Female patients may feel vulnerable when they find themselves with a male anaesthetic team.

●●

A female HCA can provide support both for the patient and the anaesthetic team.

Theatre checks The HCA will assist in the cleaning (damp dusting if carried out) and setting up of the theatre at the start of the list.

●●

This will include making sure that the theatre prep rooms are fully stocked and everything is ready and available for the list.

●●

●●

Circulating duties Helping set up for the scrub team by opening instrument trays, arranging drapes and sundry equipment, needles, swabs, blades and prep solutions.

●●

Assisting with the transfer of the patient from the trolley onto the operating table – if the transfer is not performed in the anaesthetic room.

●●

●●

Assisting in placing pressure-relieving devices.

Using the theatre computer to log the patient into theatre and help to complete patient documentation where appropriate. (Note: a registered, qualified practitioner must countersign all documentation.)

●●

●●

Always contributing to maintaining the sterile field.

Accepting specimens and labelling them correctly under the direction of the scrub practitioner or operating surgeon.

●●

Handling contaminated instruments, sundries and specimens correctly, following local policies and protocols.

●●

●●

Cleaning the theatre area thoroughly between patients.

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Cardiothoracic Manual for Perioperative Practitioners

Table 1.1: The education and training requirements of the non-medical surgical team Designation

United Kingdom

Anaesthetic practitioner

Nursing diploma or degree with additional study, post-qualification in anaesthetic perioperative practice OR An Operating Department Practitioner diploma or degree

Scrub practitioner Nursing diploma or degree with additional study, post-qualification in surgical perioperative practice OR An Operating Department Practitioner diploma or degree

United States of America

Europe

Australia

New Zealand

Associate of Science in Nursing; Associate of Applied Science in Nursing; Associate Degree in Nursing. Successful completion of any of these qualifications enables the candidate to sit the National Council Licensure Examination for registered nurses OR Bachelor Degree in Nursing. Once qualified, additional training (from 6 to 12 months internship in the operating room) is required to practise in the operating room.

Each European country has its own unique type of nonphysician anaesthesia team member and the roles adopted by these staff members vary substantially.

A nursing degree or diploma, plus specialised perioperative training or a two-year Diploma in Paramedical Science (Anaesthesia), leading to a qualification as an Anaesthetic Assistant.

A nursing degree or diploma, plus specialised perioperative training or a two-year Diploma in Paramedical Science (Anaesthesia) leading to a qualification as an Anaesthetic Assistant.

Associate of Science in Nursing; Associate of Applied Science in Nursing; Associate Degree in Nursing. Successful completion of any of these qualifications enables the candidate to sit the National Council Licensure Examination for registered nurses OR Bachelor Degree in Nursing. Once qualified, additional training (from 6 to 12 months internship in operating room) is required to practise in the operating room

A Bachelor’s Degree in Nursing with a postgraduate programme – for example, based on the European Operating Room Nurses Association (2012) Common Core Curriculum for Perioperative Nursing

A Bachelor’s Degree or Diploma in Nursing; some states (such as New South Wales) only accept a nursing degree. Throughout Australia and New Zealand there are various programmes offering perioperative training courses. The Australian College of Operating Room Nurses offers an opportunity for organisations that provide programmes relating to education and training for perioperative personnel to seek accreditation of the programmes from the College (ACORN 2015)

A Bachelor’s Degree or Diploma in nursing; some states (such as New South Wales) only accept a nursing degree. Throughout Australia and New Zealand there are various programmes offering perioperative training courses. The Australian College of Operating Room Nurses offers an opportunity for organisations that provide programmes relating to education and training for perioperative personnel to seek accreditation of the programmes from the College (ACORN 2015)

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Healthcare professional roles within the operating room

Post-anaesthetic care or recovery practitioner

A nursing diploma or degree or an ODP diploma or degree; a nurse will also have to undertake further study to be qualified to work as a post-anaesthetic or recovery practitioner

Associate of Science in Nursing; Associate of Applied Science in Nursing; Associate Degree in Nursing. Successful completion of any of these qualifications enables the candidate to sit the National Council Licensure Examination for registered nurses OR Bachelor’s Degree in Nursing. Once qualified, additional training (from 6 to 12 months internship in operating room) is required to practise in the operating room

A Bachelor’s Degree in Nursing with a postgraduate programme – for example, based on the European Operating Room Nurses Association (2012) Common Core Curriculum for Perioperative Nursing

A Bachelor’s Degree or Diploma in Nursing, plus a specialised course in postanaesthesia care

Assistant theatre practitioner

A two-year foundation degree; ATPs are nonregistered staff

A one-year surgical technology certified programme

No equivalent

Large hospitals offer training programmes quite often. Training lasts for 1 or 2 years, and sometimes includes other aspects of medical technology

Healthcare assistant

Either a National Vocational Qualification assessed in-house or local inhouse training or no qualifications; HCAs are non-registered staff

For Operating Room Attendants, High School and on the job training or the Operating Room Assistant Training

No information found In some states, a Level 4 Health Support Assistant certificate may be required. In others, no official qualifications are required. However, previous experience is often requested, with sound written and oral communication skills, plus an ability to work as part of a team

A Bachelor’s Degree or Diploma in Nursing, plus a specialised course in postanaesthesia care

In some states, a Level 4 Health Support Assistant certificate may be required. In others no official qualifications are required. However, previous experience is often requested, with sound written and oral communication skills, plus an ability to work as part of a team

Non-medical advanced surgical team Introduction Due to a range of political, economic, technological and sociological drivers impacting upon contemporary healthcare services, there is a continuing requirement for service evolution and workforce redesign that includes the development of advanced clinical roles within nursing and allied health professions. This has led to the development of a plethora of advanced roles for non-medical practitioners. The Royal College of Surgeons (RCS) of England (2016, p. 1) states:

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Cardiothoracic Manual for Perioperative Practitioners

Non-medical practitioners, who do not regularly rotate through different organisations and who often build up significant expertise in their areas of work, can improve the coordination of patient care as they can provide a link between patients, consultants and trainees. There are also benefits to having highly experienced and trained non-medical practitioners on hand to answer questions and provide support. They provide a familiar face, help establish good relationships, and are key to developing trust between patients and staff. The challenges in developing these advanced roles include a lack of standardisation and regulation across the UK. Health Education England and the RCSEng are working to standardise these roles and their responsibilities. This section briefly introduces some of the non-medical roles that may be included in cardiothoracic surgical teams to aid the delivery of safe and effective care to the patients.

Surgical first assistant (formerly advanced scrub practitioner) Surgical first assistants are defined by the PCC (2018, p.1) as: The role undertaken by the registered practitioner who provides continuous, competent and dedicated surgical assistance to the operating surgeon throughout the surgery; Surgical First Assistants practice as part of the surgical team, under the direct supervision of the operating surgeon. Scrub practitioners traditionally covered elements of the SFA role, particularly as junior doctor numbers diminished, and they could no longer support theatre lists. This has led to confusion about the legalities, accountabilities and responsibilities of the SFA role. Recommendations from the PCC (2018) position statement state that any perioperative practitioner undertaking a surgical first assistant role must have the necessary skills and underpinning knowledge gained via a nationally recognised programme of study, which has been benchmarked against national standards. In addition, surgical needs for a surgical first assistant should be highlighted in time to allow an extra relevant qualified practitioner to be rostered into the theatre. All SFAs should have appropriate job descriptions that clearly describe their role and all skills should be risk-assessed and covered by appropriate policies and procedures. Dual role (whereby the scrub practitioner acts as both the scrub practitioner and the surgical first assistant) should not be undertaken except when agreed within the Trust and where strict parameters are heeded and only for relatively minor procedures. The PCC (2018, p. 1) states: In the event that an employer considers that a dual role is required in minor surgery, then this must only be undertaken by a registered practitioner and the decision should be endorsed by a policy that fully supports this practice and should also be based on a risk assessment of each situation to ensure patient safety. Some examples of SFA responsibilities: ●●

Preoperative and postoperative visiting Whenever possible to facilitate, preoperative and postoperative visiting enhances communication links between the patient, theatre and ward.

●●

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Healthcare professional roles within the operating room

●●

Positioning Being able to position the patient with knowledge of optimum safe positioning to give the surgeon best access for the procedure.

●●

Being aware of nerves, blood vessels that could be potentially damaged through mal- positioning.

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●● ●●

Male and female catheterisation ●●

●●

Knowing the surgeon’s operation technique and preferences to aid optimum positioning. This is a core skill undertaken by all trained SFAs.

Prepping and draping The SFA must have knowledge of the operative technique, the surgeon’s approach and preferences in order to prep and drape appropriately to enhance the safety of the patient.

●●

●●

Skin and tissue retraction ●●

The surgeon retains responsibility for placing all retractors as required.

It is the SFA’s responsibility to know how much pressure to exert in order to avoid damage to the patient.

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●●

Assisting with haemostasis, including indirect diathermy Having knowledge of wound healing, clotting factors and the different methods of maintaining haemostasis within surgery.

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●●

Camera holding in minimal invasive surgery Being able to safely and knowledgeably maintain an optimum operative visual field during laparoscopic surgery.

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Cutting of sutures and ties Safely cutting sutures and ties to the optimum length and having an in-depth knowledge of suture materials.

●●

Some SFAs are required by their Trusts to extend their skills and knowledge by undertaking further study. This may include the advanced skills of suturing skin, administering local anaesthetic and sewing in drains. However, it is imperative that practitioners stay within the boundaries of these roles and only undertake skills that are within their job description, risk assessed and for which there are written policies and procedures. In the USA, when the RN is also performing the scrub role, they will often participate in the surgical procedure, both by assisting the surgeon as well as managing the sterile instruments during surgery. This is in contrast to the UK, where such a dual role would only be carried out under strict guidelines. However, in Australia and New Zealand the perioperative nurse surgeon’s assistant role is very similar to that of the UK’s surgical first assistant.

Surgical care practitioner (SCP) According to the Royal College of Surgeons of England (2014, p. 13) National Curriculum definition, a surgical care practitioner is:

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Cardiothoracic Manual for Perioperative Practitioners

A registered non-medical practitioner who has completed a Royal College of Surgeons accredited programme (or other previously recognised course), working in clinical practice as a member of the extended surgical team, who performs surgical interventions, preoperative and postoperative care under the direction and supervision of a consultant surgeon. SCPs tend to be employed as members of the extended surgical team, responsible to the consultant surgeon. The role provides patient care within the perioperative environment, on the wards, in clinics and departments within a specific surgical pathway, e.g. cardiothoracic. SCPs are registered healthcare professionals and abide by their registering body’s Code of Conduct (NMC 2015, HCPC 2016). Their scope of practice includes any areas that have been covered by training and education, as detailed in the Royal College of Surgeons of England (RCSEng 2014) national curriculum, clinical experience and the successful assessment of competency. SCPs are described by Jones, Arshad and Nolan (2012, p. 19) as ‘[working] within a consultant led extended surgical team, [who] work alongside a variety of healthcare practitioners to provide safe patient care, meet service demand and educate the future surgical workforce’. Some examples of SCP responsibilities (RCSEng 2014) include: ●●

Clinics Seeing patients in clinic, listing them for surgery and taking consent where agreed within their surgical team, while working in line with local policies and guidelines.

●●

●●

Preoperative assessment Undertaking clinical examinations and diagnostic procedures, adhering to enhanced recovery protocols as directed by the surgical team.

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●●

Investigations (both preoperative and postoperative) Arranging appropriate investigations to enhance patient safety across all stages in the patient journey.

●●

●●

Consent process Gaining informed consent from patients, adhering to the General Medical Council, Local Trust or healthcare provider guidelines.

●●

●●

Liaison with the Multidisciplinary Team Supporting patient-centred care, the smooth running of the theatre lists and preoperative and postoperative care.

●●

●●

World Health Organisation Checklist Participating in or leading the briefings for the Five Steps to Safer Surgery Checklist (WHO 2009).

●●

●●

Preparation of patients for surgery ●●

Carrying out venepuncture and catheterisation.

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Healthcare professional roles within the operating room

●●

Surgical interventions Assisting the surgical team, e.g. harvesting a vein and/or performing some technical or operative procedures autonomously. Writing up operation and/or ward round notes.

●●

●●

Postoperative patient care Recognising a deteriorating patient and knowing about the National Early Warning Score (NHS Improvement 2018) wound assessment, treatment and knowledge of discharge procedures and follow-up care.

●●

●●

Supporting junior members of the surgical team As consistent members of the team, SCPs can support junior doctors by facilitating training sessions or carrying out duties so that the juniors can be released to attend training sessions.

●●

In the USA, the physician assistant (PA) assists in the preoperative evaluation of patients and during surgery; they also follow up patients after surgery. They are the surgeon’s ‘right hand’, often writing the orders, medications and medical interventions that nurses use to care for hospital patients. The PA is often ‘on call’ with the surgeon and responsible for taking phone calls from patients in the postoperative period as well as assisting with emergency care for patients at night and at weekends.

Perfusionist One of the most important roles on this team is the perfusionist (National Health Service Careers 2018b). Due to the nature of cardiac surgery, certain procedures require a heart that is not beating. It is therefore necessary to temporarily suspend a patient’s normal circulatory and respiratory functions. The perfusionist must use alternative means to maintain the function of the heart and lungs during the operative procedure. According to Explore Healthcare Careers (2018, p. 1), the perfusionist’s role is to: Operate a heart-lung machine, which is an artificial blood pump, which propels oxygenated blood to the patient’s tissues while the surgeon operates on the heart. The perfusionist manages the physiological and metabolic demands of the patient while the cardiac surgeon operates on the heart. It is also the perfusionist’s responsibility to deliver the drug that stops the heart. As the perfusionist is responsible for diverting blood away from the heart and lungs during cardiothoracic procedures, they must ensure that oxygen is added to the blood and carbon dioxide is removed. They are responsible for maintaining the patient’s blood volume during the procedure to maintain perfusion of tissues and cells throughout the body. In addition, they constantly measure physiological changes during the procedure. With the agreement of the surgeon and anaesthetist, they may also administer medications via the cardiopulmonary bypass machine should the need arise. In order to successfully undertake their role, a perfusionist must be able to communicate at all levels, from simple to complex, in addition to being a good team player. Like all other

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Cardiothoracic Manual for Perioperative Practitioners

professionals, perfusionists rely on other members of the multidisciplinary team to be able to fulfil their role, especially within the perioperative environment. Another characteristic of a good perfusionist is their ability to work with, and understand, complex technical machinery and troubleshoot any problems that may occur. Some examples of a perfusionist’s responsibilities include: ●●

Liaising with the surgeon and team Close communication is vital, between the surgeon, the anaesthetist and the perfusionist, to ensure optimum pharmacology and blood transfusion intervention during the surgery.

●●

●● ●●

The perfusionist will also keep the theatre team apprised of the patient’s condition.

Cardiopulmonary equipment and techniques The perfusionist must be knowledgeable about all the equipment utilised in bypass. After consultation with the surgeon, the perfusionist is responsible for selecting all appropriate equipment for the planned procedure.

●●

●●

Managing the patient’s physiological state The perfusionist will measure and interpret blood and other parameters to decide on the thermal, mechanical and pharmacological manipulation required to maintain the patient’s physiological state.

●●

It is essential for the perfusionist to have detailed knowledge of the patient’s medical history.

●●

Table 1.2: A brief overview of the education and training requirements for the non-medical advanced surgical team Designation

United Kingdom

United States of America

Europe

Australia

New Zealand

Surgical First Assistant

A nursing diploma or degree or an ODP diploma or degree. Now incorporated into a three-year ODP preregistration degree or a continuing professional development. module.

A Certified First Assistant (also called a Certified Surgical First Assistant), is a non-medical professional who assists surgeons during operations. Accredited CSFA education programmes are available at the certificate and associate degree levels that satisfy the training and eligibility requirements to sit for the requisite certification exam. Since this is an upperlevel position, applicants to CSFA programmes must typically already work in the health field, as licensed surgical technologists, nurses or in a similar position.

In 2012 the European Operating Room Nurses Association published the ‘Common Core Curriculum for Perioperative Nursing’, which incorporates the role of the Surgical First Assistant. However, it will depend on each individual European State/Country.

A Bachelor’s Degree or Diploma in Nursing, plus a specialised postgraduate course.

A Bachelor’s Degree or Diploma in Nursing, plus a specialised postgraduate course.

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Healthcare professional roles within the operating room

Surgical Care Practitioner

Current training is a two-year Master’s pathway specific degree gained at an institution accredited by the Royal College of Surgeons. Only open to qualified nurses, ODPs or holders of another relevant healthcare degree such as physiotherapy.

No equivalent Master’s degree from a physician assistant programme. They do not usually have a healthcare background but are expected to apply with a science degree.

Perfusionist

A Postgraduate Diploma or MSc in Clinical Perfusion Science. The College of Clinical Perfusion Scientists of Great Britain and Ireland holds the register of accredited practitioners.

Perfusionists are required to complete perfusion training programmes, which take a minimum of four years. Many perfusionists choose to pursue a certificate programme, first completing a four-year Bachelor’s degree and then applying to the Perfusion Certificate Programme. Most perfusion education programmes require candidates to fulfil prerequisite courses in college-level science and math, and prefer candidates with majors in biology, chemistry, anatomy or physiology. Other programmes prefer candidates to have a background in medical technology, respiratory therapy or nursing.

On the job training in Croatia, France, Greece, Germany and Switzerland. Basic degree in Italy and Germany. Post-graduate training in Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Malta, Netherlands, Norway, Poland, Portugal, Spain, Sweden and Switzerland.

Advanced Nurse Practitioners and Physician’s Assistants are taking on more work traditionally undertaken by doctors.

Advanced Nurse Practitioners and Physician’s Assistants are taking on more work traditionally undertaken by doctors.

The current three-year diploma course was launched in 2012. Entry to the course is restricted to non-certified perfusionists or trainee perfusionists employed by hospitals or private perfusion groups in Australia, New Zealand and Singapore who have a Bachelor’s degree in Science, Applied Science or Nursing.

The current three-year diploma course was launched in 2012. Entry to the course is restricted to non-certified perfusionists or trainee perfusionists employed by hospitals or private perfusion groups in Australia, New Zealand and Singapore who have a Bachelor’s degree in Science, Applied Science or Nursing.

Medical surgical team The medical surgical team consists of doctors and surgeons with varying degrees of experience and responsibility, as well as consultant anaesthetists and their juniors. In this section, there are brief descriptions of the roles and responsibilities of all grades of surgeons and anaesthetists, each of whom plays a key part in delivering safe and effective patient care. The list below (RCSEng 2018) shows the seven training stages that would typically take a surgeon from medical degree to consultant: 1. Obtain medical degree from the university 2. F1 (Foundation Year 1) 3. F2 (Foundation Year 2)

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4. Core Training (CT1 and CT2) 5. Specialist surgical registrar (SpR) 6. Associate specialist surgeon 7. Speciality surgical registrar (StR) 8. Speciality/Staff/Grade surgeons 9. Consultant surgeon.

Surgical team Consultant cardiothoracic surgeon Consultant cardiothoracic surgeons are doctors who have specialised in cardiothoracic surgery. They will have gone through a lengthy educational process (both theoretical and practical) to gain the knowledge and experience needed to become consultant surgeons. Their scope of practice covers a variety of conditions and surgical procedures, ranging from a coronary artery bypass to a heart and lung transplant. In the UK, to become consultants in the NHS, their names must be on the specialist register of the General Medical Council. According to the Royal College of Surgeons in Ireland (RCSI 2018), the training to become a cardiothoracic surgeon is one of the longest of all the specialisms, taking approximately six years between the grades of ST3 and ST8. To become a consultant, the individual is expected to spend time in the various specialities and sub-specialities of cardiothoracic surgical practice. For example, ‘at a minimum Specialist Trainees will spend three years doing adult cardiac surgery, six months doing thoracic surgery and six months in Paediatric cardiothoracic surgery’ (RCSI 2018, p. 1). A consultant surgeon must have manual dexterity, in addition to an excellent understanding of biology, physiology and other sciences. They also need to remain calm in stressful situations and be able to concentrate, even in adverse situations. Consultant surgeons must pay attention to detail and be able to cope with trauma and death. They also need to have physical and mental stamina, leadership qualities, and be up to date with evidence-based practices and apply them in their work. The RCSEng (2009, p. 2) states that a consultant-led service must ensure best-quality care for patients: In a consultant-delivered service the consultant surgeon is clinically responsible for the care the patient receives during the treatment. The consultant will either deliver or closely supervise in the clinical setting all aspects of the care the patient receives. Care may be delivered by other members of the surgical team but only under the supervision of the consultant who is always alert to the needs of the patient being treated. The consultant cardiothoracic surgeon’s responsibilities can include: Treating patients using excellent levels of clinical judgement which complement a first-rate knowledge of cardiovascular, physiological and respiratory anatomy.

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Healthcare professional roles within the operating room

Leading a surgical team and overseeing the training and assessment of junior members of the team.

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Consultant surgeons are responsible for training sufficient numbers of trainee surgeons to enable future workforce planning, as well as analysing and maintaining patient records.

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Physical examinations and diagnostics testing to include x-rays, magnetic resonance imaging, computed tomography scans and positron emission tomography scans

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Undertaking various surgical procedures, from minor to major surgery

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Postoperative care and treatment

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Managing patient expectations ●●

Consultant surgeons must be directly involved in all their designated patients’ care.

This is believed to aid treatment decisions, maximise resources and ensure best practice for patients.

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Research responsibilities Consultants are responsible for their own professional development and are at the forefront of service development based on the best clinical practice.

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On-call commitments

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Transplant surgery, i.e. heart and lungs

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Attention to detail and excellent hand eye co-ordination are essential.

Trainee specialist registrar in surgery A specialist registrar in cardiothoracic surgery is accountable to, and works under the supervision of, a consultant cardiothoracic surgeon. According to the General Medical Council (GMC 2014, p.13) training syllabus, this specialist registrar level equips the registrar to work to a high standard, demonstrating ‘knowledge, skills and professional behaviours’. Cardiothoracic registrars should be developing competencies in managing both elective and emergency situations and finalising their professional competencies in all aspects of cardiothoracic surgery (GMC, 2014). Although specialist registrars do not have financial or budgetary controls, they should have an appreciation of how clinical requirements affect departmental resources and how costing is crucial. In addition to financial issues the registrars will be committed to observing safe working practices to protect their own and others’ health and safety. Another aspect of this role is to provide leadership and support for junior members of the team and to assist the consultant in ensuring that junior medical members of the team receive appropriate performance management, professional training and development opportunities. A surgical trainee specialist registrar’s main responsibilities can include: Providing safe and high-quality person-centred care including patient assessment and management in consultation with the treating consultant

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Having good communication skills to aid extensive interaction within the multidisciplinary team

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Cardiothoracic Manual for Perioperative Practitioners

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Ensuring coordination of care for patients in the department

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Ensuring timely and clear clinical communication including clinical handover

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Ensuring timely escalation of care-related issues to the consultant when required

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Demonstrating commitment to quality and safety

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Teaching, supporting and supervising junior staff

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Providing clinical leadership to the multidisciplinary team

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Complying with all relevant health policies and procedures

Demonstrating good self-management skills, such as time management and completing intercollegiate requirements.

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Core/Surgical trainees (junior doctors) Junior surgeons work directly under the supervision of the consultant, whose patients they are managing. Junior surgeons share responsibility with other team members for preoperative assessment, preparation, surgical care and postoperative care of all cardiothoracic surgery patients. This includes attendance at outpatient clinics, ward rounds and elective and emergency operating sessions. An important aspect of the role is to be able to communicate with both junior and senior medical colleagues, with ward and intensive care nurses, theatre nurses, ODPs, perfusionists and nurse practitioners, in addition to other relevant members of the multidisciplinary team. A core/surgical trainee or junior doctor’s main responsibilities can include: Assisting the consultant or specialist registrar in treating patients presenting with a range of symptoms and elective conditions as specified in the core syllabus for the specialty of cardiothoracic surgery

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Gaining competence in a broad range of skills, including: ●●

Interpretation of both echocardiograms and cardiac catheterisation studies

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Insertion of temporary cardiac pacemakers

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Exercise testing

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Insertion of Swan-Ganz catheters

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Management of a broad range of cardiac cases, both acute and elective.

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Assisting the consultants and operating surgeons in the operating theatre

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Performing operative procedures under supervision as appropriate

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Postoperative follow-up of patients in the outpatient clinic

Recording both written and electronic clinical data as outlined in the principles of Good Medical Practice described by the GMC

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Participating in postgraduate education activities

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Teaching and supporting medical students and junior members of the multidisciplinary team

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Managing own workload and study

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Complying with relevant policies and procedures.

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Healthcare professional roles within the operating room

In the USA, during their final year in medical school, the student will begin applying for a general residency programme. The Accreditation Council for Graduate Medical Education is the accrediting body of the Residency Review Committee for each specialty. The Residency Review Committee determines the rules and regulations under which the training programmes operate, and they maintain the overall quality of the accredited programmes. After general residency training, the doctor undertakes specialist cardiothoracic training. On completion of training, the resident is eligible to become certified by both the American Board of Surgery and the American Board of Thoracic Surgery. In addition, some institutions now offer an integrated six-year clinical programme that will match medical students directly with a cardiothoracic pathway. It is anticipated that more six-year integrated programmes will emerge in the near future (Society of Thoracic Surgeons 2015, p. 2). In both Australia and New Zealand, independent standards bodies oversee medical education and training. The Australian Medical Council assesses and, if appropriate, accredits the medical courses offered by Australian university medical schools. It also assesses and, where appropriate, accredits postgraduate medical specialist training programmes and continuing professional development programmes. The Australian Medical Council collaborates with the Medical Council of New Zealand in the assessment and accreditation of specialist training programmes and continuing professional development programmes that involve medical practitioners or trainees from both countries. Among their responsibilities, the Australian Medical Council and MCNZ accredit the work of the Royal Australasian College of Surgeons in Australia and New Zealand (Royal Australasian College of Surgeons 2015). In Europe admission to medical schools varies from country to country. Some, such as Belgium, Finland, Greece, Italy, Poland, Portugal, Romania, and Spain (Martinho 2012, p. 984), exclusively use academic criteria to allow admission to university programmes. This is mainly carried over to residency programmes. Other countries (such as Denmark) place most students on academic ability but do reserve a small proportion of places for students where other characteristics are considered. In Germany and the Czech Republic medical training admissions combine academic ability with other characteristics decided by individual universities (Martinho 2012).

Anaesthetic team Consultant anaesthetist A consultant anaesthetist is a medical specialist who looks after a patient before, during and after surgery (NHS Careers 2018d). This is a demanding speciality which requires excellent knowledge of anatomy, physiology and pharmacology to ensure that patients remain asleep during the surgery and for as long after as required. The consultant anaesthetist also needs to work very closely with the surgical team, the perfusionist and the wider multidisciplinary healthcare professionals in caring for cardiothoracic patients. The Royal College of Anaesthetists (2018a, p. 1) states: Anaesthetists form the largest single hospital medical specialty and their skills are used in all aspects of patient care. While the perioperative anaesthetic care of the surgical patient

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is the core of specialty work (and this includes all types of surgery from simple body surface surgery in adults to the most complex surgery in patients of all ages, including the premature new-born) many anaesthetists have a much wider scope of practice. The characteristics of a good consultant anaesthetist are varied and wide-ranging, including the ability to communicate in a variety of ways with people who have differing abilities and needs. In addition, being aware of patient concerns and anxieties can allow the anaesthetist to help patients understand their options better. A consultant anaesthetist needs to be able to work both independently and as part of a team, and to be able to make difficult clinical decisions promptly and confidently. Like all medical consultants, they will need to concentrate for long periods of time while maintaining strict attention to detail, especially during the perioperative phase of a patient’s journey. All consultant anaesthetists have a responsibility to actively teach junior anaesthetists and other healthcare professionals. A consultant anaesthetist’s main responsibilities can include: ●●

Having overall responsibility for patients under their care

Being involved in clinical governance, risk management and clinical audit – overseeing and maintaining systems or processes to ensure the continuation of optimum, safe patient care

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Taking responsibility for the professional supervision and development of trainee doctors within the specialty

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Providing a consultation service and advisory service to other clinical colleagues in other specialties within the Trust and primary care

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Participating in the development of the anaesthesia and critical care treatment protocols and guidelines

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Ensuring that their practice is current and evidence-based

Cardiothoracic anaesthetists also have responsibilities in intensive care units, high dependency units, ward areas and other specialist areas (such as intraoperative transoesophageal echocardiography services) as required.

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Trainee specialist registrar in anaesthetics A specialist registrar in anaesthetics works under the supervision of a consultant anaesthetist. A specialist registrar describes their experiences (Royal College of Anaesthetists 2018b, p. 1): Anaesthetics is a very varied speciality. You never know what each day is going to hold – relieving pain on a labour ward, resuscitating a sick patient in ITU or participating in an elective theatre list or chronic pain clinic. There is something for everyone. Outside the operating theatres, specialist registrars would work with cardiac and thoracic patients in departments such as radiology and radiotherapy, using different types of anaesthetic such as: ●●

Local anaesthetic – for minor operations, working on a specific localised area of the body

Regional anaesthetic – for example, an epidural anaesthetic to numb a larger surface area of the body (this is sometimes used when a general anaesthetic would be more dangerous for the patients because of their clinical condition)

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General anaesthetic – rendering the patient unconscious (used for operations where local and regional anaesthetics are not suitable).

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An anaesthetics trainee registrar’s main responsibilities can include: ●●

Preoperative preparation of surgical patients

Provision of sedation and anaesthesia for patients undergoing various cardiothoracic procedures

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Resuscitation and stabilisation of patients in the emergency department or in a stabilisation bay in a recovery area

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Administration of pain relief and monitoring its effects ●●

In obstetrics

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In postoperative pain relief

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In acute pain management

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In chronic and cancer pain management.

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Transporting acutely ill patients between departments and/or hospitals

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Pre-hospital emergency care

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Intensive care medicine

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Teaching junior medical and other healthcare professional staff

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Working closely with other MDT members, such as the perfusionist and the surgeon.

Core/anaesthetic trainee (junior anaesthetist) Junior anaesthetists work full time under the direction of the various consultant anaesthetists on the team. The junior anaesthetist will be granted study leave to help them achieve higher examinations and is usually allowed to sit one examination every six months to try and minimise disruption to the department and their staffing levels. A change in the training of anaesthetists now often means that instead of entering the speciality two or three years following their postgraduate training, they now enter immediately after their foundation programmes. According to The Group of Anaesthetists in Training (GAT) (2016, p. 32): Advanced training is vital to any trainee wishing to pursue a career in cardiothoracic anaesthesia and it is essential that trainees gain a wide and varied clinical experience but also build a CV for consultant appointment. A junior anaesthetist’s main responsibilities can include: ●●

Allocation of patients to the intensive therapy unit (ITU)

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Assisting with the management of ITU patients

Attending day-time emergencies and other out-of-hours’ emergencies with a consultant anaesthetist (can include on-call responsibilities, once a level of competence has been established)

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Allocation of patients to theatre sessions under the supervision of a more senior anaesthetist

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Assisting other departmental staff to maintain services – for example, working with the pain team.

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Cardiothoracic Manual for Perioperative Practitioners

In the USA anaesthesiologists are board-certified by a specialty medical board – either the American Board of Anaesthesiology or the American Osteopathic Board of Anaesthesiology. The American Board of Anaesthesiology is a member of the American Board of Medical Specialties, while the American Osteopathic Board of Anaesthesiology falls under the auspices of the American Osteopathic Association. Both boards are recognised by the major American insurance underwriters. In the USA, approximately 60% of anaesthetics are provided by certified registered nurse anaesthetists (CRNAs). The CRNAs have similar responsibilities to anaesthesiologists and they provide safe anaesthetics for patients undergoing surgical procedures with oversight from an anaesthesiologist. This means there may be one anaesthesiologist responsible for providing support to a group of surgical rooms, each with a CRNA providing care to the patient. In Australia and New Zealand, anaesthetists are physicians who are represented by the Australian Society of Anaesthetists and the New Zealand Society of Anaesthetists. Training is overseen by the Australian and New Zealand College of Anaesthetists. In Europe anaesthetists are all physicians who, after medical school, undertake periods of specialised accredited anaesthetic training of between 4 and 5 years.

Table 1.3: A brief overview of education and training requirements for the surgical team. Designation

United Kingdom

United States of America

Europe

Consultant Surgeon

Medical degree, 5 years

The Medical College Admissions Test

Varies between European countries

Foundation Programme, 2 years

4 years of Medical School

Core/Surgical Trainee, 5 years of residency training minimum of 2 years Cardiothoracic speciality training Certificate of Completion of Training and becomes a Fellow of one of the Royal Colleges, up to a further 6 years of training

In the 4th year decides on speciality training, between 2 and 3 years Successfully completes accredited programme

Australia

Completion of a medical degree at an Australian university, Basic medical degree, 4–6 years 4–6 years Internship, 1 year Internship, minimum including rotations in 1 year surgery, medicine and emergency care Has to take test to access the residency Surgical Registrar programmes, which speciality training, up vary (cardiovascular to 6 years surgery is 6 years and thoracic surgery is 5 Fellowship – optional, e.g. research years)

Apply to the American Boards to be able to practice

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Fellow of the Royal Australasian College of Surgeons (FRACS) – Consultant Surgeon

New Zealand Completion of a medical degree at a New Zealand university, 5 years Prevocational medical training, lasts 2 years Complete postgraduate registrar training within a speciality i.e. cardiology, 6 years Fellow of Royal Australasian College of Surgeons (FRACS) examination to become a Consultant Surgeon

Healthcare professional roles within the operating room

Consultant Anaesthetist

Medical degree, 5 years

Varies between Advanced science classes in high school European countries

Medical degree, 5 to 6 years

Medical degree, 5 to 6 years

Trainee Foundation Course, 2 years

Pre-med college course leading to a Bachelor’s degree, 4 years

Example of the Scandinavia model

Completion of 5 years’ training in accredited training position in a hospital

Completion of 5 years’ training in accredited training position in a hospital

Completion of the Primary Examination

Completion of the Primary Examination

Completion of the Final Examination

Completion of the Final Examination.

Completion of all specialised study units, including areas such as neuro-anaesthesia, cardiac anaesthesia, paediatrics and obstetrics

Completion of all specialised study units, including areas such as neuro-anaesthesia, cardiac anaesthesia, paediatrics and obstetrics

Postgraduate Anaesthesia Programme, 7 years or 8 years with the Acute Care Common Stem Programme or an option of completing a dual qualification with intensive care medicine which takes approximately 8.5 years If training and exams are successfully completed, will be awarded a Certificate of Completion of Training which allows them to apply for consultant posts Specialist Registrar Surgery

Medical School, 4 years

Internship, 1 year

Anaesthesiology residency, 4 years Option of a further 1-year Fellowship in a specific area of anaesthesiology such as critical care medicine, pain medicine, research or education

Medical degree, 5 years

The Medical College Admissions Test

Foundation Programme, 2 years

Medical School, 4 years

Core/Surgical Trainee, Residency training, 5 years minimum of 2 years In the fourth year, Undertaking the speciality decided cardiothoracic speciality training, up Speciality training, to 6 years 2–3 years

Specialist Registrar Anaesthetist

Medical School, 6 years

Residency Programme, 5 years includes training in intensive care, paediatric anaesthesia and intensive care, advanced pain medicine, critical care medicine, advanced obstetric anaesthesia

Completion of a medical degree at an Australian university, Basic Medical Degree, 4–6 years 4–6 years. Internship, 1 year Internship, minimum including rotations in 1 year. surgery, medicine and emergency care Has to take test to access the residency Residency, minimum programmes of 1 year Varies between European countries

Undertaking residency Surgical Registrar programmes: speciality training, up cardiovascular to 6 years surgery is 6 years and thoracic surgery is 5 years

Completion of a medical degree at a New Zealand university, 5 years Prevocational medical training, 2 years Complete postgraduate registrar training within a speciality, i.e. cardiology, 6 years

Medical degree, 5 years

Varies between Advanced science classes in high school European countries

Medical degree, 5 to 6 years

Medical degree, 5 to 6 years

Trainee Foundation Course, 2 years

Pre-med college course leading to a Bachelor’s degree, 4 years.

Example of the Scandinavia model

Completion of 5 years’ training in accredited training position in a hospital

Completion of 5 years’ training in accredited training position in a hospital

Completion of the Primary Examination

Completion of the Primary Examination

Postgraduate Anaesthesia Programme, 7–8.5 years

Medical School, 4 years Anaesthesiology residency, 4 years

Medical School, 6 years Internship, 1 year Residency Programme, 5 years

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Cardiothoracic Manual for Perioperative Practitioners

Core Surgical Trainee

Core Anaesthetist Trainee

Medical degree, 5 years

The Medical College Admissions Test

Varies between European countries

Foundation Programme, 2 years

Medical School, 4 years

Basic medical degree 4–6 years

Core/Surgical Trainee, minimum of 2 years

Residency training, 5 years

Internship, minimum 1 year Has to take test to access the residency programmes

Completion of a medical degree at an Australian university, 4–6 years

Completion of a medical degree at a New Zealand university, 5 years

Prevocational medical Internship, 1 year including rotations in training lasts 2 years surgery, medicine and emergency care Residency, minimum of 1 year

Medical degree, 5 years

Varies between Advanced science classes in high school European countries

Medical degree, 5 to 6 years

Medical degree, 5 to 6 years

Trainee Foundation Course, 2 years

Pre-med college course leading to a Bachelor’s Degree, 4 years

Example of the Scandinavia model

Completion of 5 years’ training in accredited training position in a hospital

Completion of 5 years’ training in accredited training position in a hospital

Medical School, 6 years

Medical School, Internship, 1 year 4 years; start of Residency Programme

Conclusion The roles described in this chapter are constantly changing, developing and adapting, due to the many factors that affect the global healthcare environment. All over the world there is an ageing population, requiring more treatments, drugs and innovations in surgical techniques. The standardisation of roles is constantly being evaluated and, where possible, implemented as described in this chapter. The physician assistant (PA) role is gradually being introduced into the UK, although PAs do not currently work in cardiothoracic theatres. As described in this chapter, surgical care practitioners currently undertake that role in the UK. Physician assistants in anaesthesia are currently used in some hospitals, where they deliver anaesthetics and maintenance throughout the surgical episode with a consultant anaesthetist nearby (playing a similar role to an anaesthesia nurse in the USA). Effective MDTs rely on good teamwork, excellent communication between all the staff and departments, and appropriate and relevant training and education. The MDT involved in delivering safe and effective patient care in cardiothoracic surgery is complex, diverse, knowledgeable and trained to react to any adverse situation that may occur during the cardiothoracic perioperative patient journey.

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2 Legal and ethical implications in the perioperative area Richard Thompson and Bhuvaneswari Krishnamoorthy

Introduction This chapter will discuss the legal and ethical considerations that govern and guide us in our practice in the cardiothoracic surgical environment. In all our practice the overriding objective must be to ‘do no harm’ (Brazier & Cave 2016) not only during surgical intervention but also in the preoperative planning and postoperative stage of the patient’s journey. We are governed by the legal system in the United Kingdom which guides us on matters relating to criminal and civil law. There are many laws relating to professional work in healthcare. There are also professional codes that govern and regulate practice, such those of the Nursing and Midwifery Council (NMC 2015) and the Health and Care Professions Council (HCPC 2016). All professional frameworks are of course underpinned by an ethical code. However, the subject of ethics will now be considered in much broader terms, illustrating how ethical theories and principles are used to support and guide our decision-making processes. We know that surgical care has been part of healthcare worldwide for over a century (WHO 2008). Surgical intervention is intended to save lives, alleviate symptoms and improve quality of life. Unfortunately, there can be complications during the surgical journey, a point that is highlighted by the WHO initiative Safe Surgery Saves Lives (WHO 2008) which cited a complication rate for inpatient surgery of ‘up to 25%’. As practitioners there are some key factors that we adopt to try to reduce these complications to a minimum. These key factors apply not only in the operating room but throughout the patient’s perioperative journey. Some are set out by our statutory bodies (HCPC, NMC, General Medical Council), and some by Acts of Parliament; many are established by locally agreed protocols and National Health Service Local Trust guidance. There are some international initiatives (such as WHO, Safe Surgery Saves Lives) and in the UK we are also guided by the National Institute for Health and Care Excellence (2015). However, many of our decisions are governed by our personal principles and what we feel we ought to do, utilising our own ethical code that has been developed throughout our private and professional life.

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Involvement of the multidisciplinary team These ethical decisions start long before the patient arrives at the operating theatre. The surgeon and the multidisciplinary team first need to decide if it is possible to operate, and if so, if surgery is the correct treatment for the patient? There are guidelines to help us evaluate the evidence, so the MDT can make an informed decision, one example being the 2014 European Society of Cardiology and the European Association for Cardiothoracic Surgery (Windecker et al. 2013) guidelines on myocardial revascularisation. These guidelines cover the risk stratification and scoring systems that are relevant to the decision either to operate (coronary artery bypass grafting) or to perform a percutaneous coronary intervention. Fortunately, major clinical decisions (such as whether to offer a patient surgery) are not left to one individual – there is a team approach. The ‘heart team’, a multidisciplinary group that is utilised for decision making, not only on who to operate on but also when and by whom, offers a balanced decision-making process (Head et al. 2013). The team can follow guidelines and evaluate the current evidence relating to individual patients and this can help reduce the incidence of inappropriate treatments. However, just because the patient’s case has been discussed and the most appropriate treatment agreed by the heart team, this does not mean that we automatically go ahead and take this course of action. There still needs to be clear discussion with the patient to inform them of the options available for treating their condition. This discussion will also form part of the process of obtaining informed consent, which is both a legal requirement and also an opportunity for the patient to be involved in considering not only the proposed procedure but also any other related factors.

Ethical values in perioperative practice Ethics is an enormous subject, and a detailed discussion of all the available theories is largely beyond the scope of this chapter. Instead the aim here will be to highlight certain ethical theories and principles and relate them to our everyday practice and the perioperative journey taken by cardiothoracic surgery patients. As professionals we must seek to practise ethically, which means that we must understand and balance the relevant ethical considerations, legal requirements and professional values. We need to apply all these requirements to our decision-making in order to reach a solution that is caring, compassionate and of high quality. A range of ethical theories exist and can be applied in different situations to guide our decision-making. For instance, utilitarian ethics is concerned with obtaining the greatest good for the greatest number. The commissioning bodies in the NHS, which have to decide on which treatments will be funded and which will not, tend to use this approach. To help them in their decisions, they may use formulas such as Quality-Adjusted Life Years to produce data to help them consider the cost: benefit ratio, in relation to a particular population demographic. Examples of utilitarianism in this sense include certain decisions on cancer drug funding implications by NICE (Johnston & Slowther 2004). Likewise, NHS England (2016) recently considered the evidence for robotic assisted lung resection and decided that this treatment would not currently be funded.

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In contrast, virtue ethics emphasise an individual’s moral character and this approach is seen in the codes produced by the regulatory bodies of healthcare professionals such as the Nursing and Midwifery Council (NMC), the Health and Care Professions Council (HCPC) and the General Medical Council (GMC). Another ethical framework is Beauchamp and Childress’ principlism approach (Beauchamp & Childress 2013) which cites the following four principles: autonomy, beneficence, non-maleficence and justice. Autonomy, enabling individuals to make informed choices, will be considered under the topic of ‘Informed consent’ (below). Beneficence is concerned with balancing the potential benefits (of a treatment) against the risks and costs, whereas non-maleficence is concerned with doing no harm, or at least ensuring that the harm done (e.g. surgery will necessarily entail a wound of some sort) is outweighed by the benefit received. Finally, the principle of justice is concerned with the questions such as: Is it fair? Is it legal? Does it protect human rights? This chapter aims to follow the patient’s journey and highlight the underpinning legal and ethical principles throughout.

Professional values The National Health Service Constitution for England (DH 2015) sets out the values on which the NHS is based. Its stated aim is to put compassion and care, respect and dignity at the heart of how both patients and staff are treated. It seeks to provide care that is transparent and accountable, promotes equality and respects human rights. The Constitution echoes the values published by the regulatory bodies of healthcare professionals: Standards of conduct, performance and ethics (HCPC 2016), Standards of conduct, performance and ethics for nurses and midwives (NMC 2015) and Good Medical Practice (GMC 2013). Healthcare may be ever-changing but the human values which underpin that care should remain constant. In 2012, the GMC and NMC published a Joint Statement of Professional Values (NMC 2012) which stressed that compassion and kindness in our dealings with patients and each other are as important as our knowledge and skills.

Informed consent Before any procedure can be performed upon a patient, their consent to that action must be obtained. If a patient is operated on without their consent, the surgeon would be guilty of assault (except in cases of emergency) (Lord Scarman 1985). Obtaining consent is therefore a legal obligation as well as an ethical obligation. An important aspect of the doctor–patient relationship is the need for mutual trust and respect, and this is incorporated into the process of obtaining informed consent. Ethically, the need for consent comes under the principle of patient autonomy (Beauchamp & Childress 2013), where the patient has full rights over their own body to decide what should and should not happen to it. The patient’s doctor can advise and facilitate the patient’s decision-making but cannot coerce the patient to decide in a certain way. The previous paragraph raises some interesting questions which will be discussed in more detail. These include (Care Quality Commission 2017): ●●

What precisely is informed consent?

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●●

How much information does a patient need to be given?

●●

How can we define ‘capacity to give consent’?

●●

What about the role of advance statements in end of life care?

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What about the moral conflict that arises when a patient’s decision is detrimental to the welfare?

What is informed consent? The requirements for valid consent are that it is given voluntarily, that the patient has capacity and that the patient has had enough information offered to them to enable them to understand the nature of the treatment and the consequences of both accepting and declining it. The Department of Health has produced standardised consent forms for use in practice although there is no legal requirement that consent should be written or in a particular form. Proper documentation of consent in written form would seem to be prudent and is certainly in line with most, if not all, local NHS policies on the subject. In surgery, checking that the patient has completed a consent form is also part of the World Health Organisation Surgical Safety Checklist (WHO 2009) that was implemented to ensure safer surgery protocols worldwide and has been incorporated into NHS practice via National Safety Standards for Invasive Procedures and subsequent local policies (NHS England 2015). The amount of information given to a patient to obtain their consent will necessarily vary from one patient to another, and according to individual circumstances. A doctor must judge the level of information that will be understood by a patient and modify their communication accordingly. Some patients may wish to know about every aspect of their surgery while others may say that they do not want to know anything about it. However, doctors are required to inform the patient of the risks of a particular procedure or they themselves could be accused of being negligent. There are examples of case law where doctors have been found negligent because they have not informed patients of the risk when they have been specifically asked about it, when the risk carries a serious consequence or if the risk is greater than 1% (e.g. Chatterton v Gerson 1981). It should be noted that the patient can revoke their consent at any time: consent is a process, rather than a one-off decision, as circumstances can change.

Capacity to give consent Ethically, it would seem that it is a basic human right to be able to either give or withhold consent to a treatment on oneself. However, in England and Wales the Mental Capacity Act 2005 (Care Quality Commission 2017), which applies only to individuals over 16 years old, sets out specific criteria to establish whether an individual has the capacity to give or withhold their consent. If these criteria are not met, that individual will be unable to formally consent to a treatment and different procedures will then be followed. To have capacity to give consent, an individual must be able to understand the information that is given to them, must be able to retain the information long enough to consider it and make a choice, and must finally be able to communicate their decision. If a patient does not have capacity to give consent, their surgical team will follow local policy to obtain consent to a treatment that is deemed to be in their ‘best interests’ – if that treatment is thought to be required before it is expected that their capacity will return.

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Advance decisions Under the Mental Capacity Act 2005 (Care Quality Commission 2017), advance decisions are a legally binding expression of an individual’s wishes concerning their end of life care and specifically which treatments they wish to accept or decline, e.g. being placed on ventilatory support or receiving cardiopulmonary resuscitation. The decisions are written into a formal document at the time that the patient is deemed to have capacity – in expectation of a time when they will not have the capacity to express their wishes. The advance decision should be in written format and be signed by the patient and then signed by a witness. An advance decision document is a way for a patient to express their right to autonomy although it may also bring up a moral conflict for the healthcare practitioners who care for them at the end of their life, who may believe that different treatments would be beneficial.

Moral conflict A competent adult has the right to refuse treatment, even against the advice of their surgical team. This is the case with any treatment, even that which could be considered life-sustaining. This is often a difficult area for healthcare professionals who may believe that the patient is choosing a wrong course of action that will be detrimental to their welfare. In practice it has occasionally been seen that a patient’s capacity will only be questioned if their wishes are in opposition to that of their surgical team; this behaviour illustrates the difficulty experienced by professionals seeking to balance the desire to promote the welfare of the patient while also respecting the patient’s right to make a free choice.

Safer surgery globally Once the legal obligation of consenting the patient has been performed and documented, it is the whole team’s responsibility, both legally and ethically, to ensure that the surgery is carried out in the safest manner possible. We are guided in this by local protocols but also by national and global initiatives. Safe surgery saves lives (WHO 2008) was the second global patient safety challenge; the first concentrated on healthcare-associated infections. Through the World Alliance on Patient Safety Working Group, WHO reached a consensus on four areas where there could be a dramatic improvement in patient safety (WHO 2008): surgical site infection prevention, safe anaesthesia, safe surgical teams and measurement of surgical services. Ten essential objectives, to reduce the complications of surgery, were then identified. These objectives come under the ethical heading of non-maleficence, and they should all be observed by the surgical team.

Ten essential objectives for safe surgery (WHO 2008) 1. The team will operate on the correct patient at the correct site. 2. The team will use methods to prevent harm from anaesthetic administration. 3. The team will recognise and effectively prepare for life-threatening loss of airway or respiratory function. 4. The team will recognise and effectively prepare for risk of high blood loss.

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5. The team will avoid allergic or adverse drug reaction known to be a significant risk to the patient. 6. The team will consistently use methods known to minimise risk of surgical site infection. 7. The team will prevent inadvertent retention of sponges or instruments in surgical wounds. 8. The team will securely and accurately identify all surgical specimens. 9. The team will effectively communicate and exchange critical patient’s information for the safe conduct of the operation. 10. Hospitals and public health systems will establish routine surveillance of surgical capacity volume and results.

WHO Surgical Safety Checklist In fact, the ten key objectives shown above largely reflect what was already happening in theatre – before, during and after surgery. However, they also provide a useful template for the whole team to work to. The main message is the importance of safe practice. The practical implementation of the objective is through a checklist, and the best one to follow is of course the WHO Surgical Safety Checklist (WHO 2009). There are three main sections in this checklist (sign in, time out and sign out) and these three sections are guided by three principles: simplicity, wide applicability and measurability (WHO 2008). The checklist has been adapted by the National Patient Safety Agency (NPSA 2009) – see example in Figure 2.1.

Figure 2.1: The WHO Surgical Safety Checklist The Surgical Safety Checklist has been implemented in England and Wales by the National Patient Safety Agency (2009). The NPSA specified that organisations must take action on the Checklist within a period of four months and ensure completion in a year.

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WHO Checklist recommendations (NPSA 2009) 1. Ensure an executive and a clinical lead are identified in order to implement the Surgical Safety Checklist within the organisation. 2. Ensure the Checklist is completed for every patient undergoing a surgical procedure. 3. Ensure the use of the Checklist is entered in the clinical notes or electronic record by a registered member of the team. Before the Checklist was introduced, a trial was carried out. Between 2007 and 2008, data was collected on over 3000 patients prior to its introduction, and again data was collected on over 3000 patients after its introduction. The rate of death was 1.5% before the Checklist was introduced and it declined to 0.8% afterwards (P = 0.003). Inpatient complications occurred in 11.0% of patients before, and in 7.0% after introduction of the Checklist (Haynes et al. 2009). Further studies have confirmed the Checklist’s effectiveness at reducing rates of death and complications (Bergs et al. 2014). The Checklist therefore seems to improve the management of the patients under our care in the preoperative environment. However, the results also depend on compliance. It may be mandatory to introduce the Checklist into all surgical departments, but it also needs to be followed up to assess whether it is being used as intended. Compliance with the Checklist was examined by Pickering et al. in 2013. They concluded that certain elements were poorly performed (especially the ‘sign out’ section), and there was wide variation between individual hospitals. Interestingly, Pickering et al. (2013) also suggested that there was a need to ‘address organisational culture issues’. An omission in following the Checklist could constitute an omission in our duty of care as practitioners, and Hind (2005, p. 9) states that ‘a duty of care exists between a practitioner and those who could be affected by their actions or omissions’.

Duty of care The duty of care for the practitioner working on the surgical perioperative management of the patient can be categorised in three areas: employment, legal and professional (Pirie 2012). Professionally, ‘do no harm’ (Brazier & Cave 2016) must be seen as our overriding goal when treating patients. If reasonable care is not taken to avoid injury, the practitioner could be seen as not upholding their duty of care and could inadvertently cause harm to the patient. This duty therefore underpins all our professional codes of conduct (GMC 2013, NMC 2015, HCPC 2016). The legal aspect of the duty of care can also be thought of as the duty we have to avoid harm coming to the patient. The defining case in law was back in 1932 (Donoghue v. Stevenson) when a woman drank a ginger beer and, while drinking, found a decomposing snail at the bottom of the bottle. Lord Atkin found that the ginger beer producers had been negligent in failing to ensure the woman’s safety in the production of the drink, and that even though the woman in question had not bought the product she had a right to compensation (Chapman 2010). Finally, an example of the employment area of duty of care could be the duty to ensure safe staffing levels in an area to ensure that patients can be safely cared for (RCN 2018).

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Cost to the NHS due to negligence When the duty of care is breached, the practitioner may be classed as negligent and a claim may be made by the patient and/or their family. Negligence claims against the NHS are not uncommon. In 2016/17, legal costs incurred in connection with such claims were £429,052,074 (NHS Resolution 2017). The number of claims is far higher in surgery than in any other speciality. Between April 2005 and March 2017, a total of 50,432 claims were made in surgery (compared with 23,899 in medicine). For a claimant to succeed in a claim of negligence, a three-stage test must be established (Bryden & Storey 2011) beyond reasonable doubt in a criminal prosecution, and on the balance of probabilities in a civil suit. The three stages are: ●●

A person is owed a duty of care

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A breach of that duty of care is established

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As a direct result of that breach, legally recognised harm has been caused

(Bryden & Storey 2011).

If we take the example of a swab left in a patient once the operation has finished, this is obvious negligence. The patient should not have swabs, or any other unplanned foreign objects, left inside them at the end of the procedure. A breach in the duty of care has therefore been established. As a direct result of the swab, there has been harm to the patient; at the very least, the patient will have to be re-opened to remove it. This could result in significant cost to the NHS and unexpected damage to the health of the patient. Because there is such fear of this happening in the operating theatre, there are locally agreed protocols which involve highly trained staff counting and bagging the swabs. In the rare event that a swab is missing at the end of the case, before closing the skin incision, the patient is x-rayed to establish if it is still inside. In such a situation, an incident form should be completed (whether or not the swab is found), as this will help the team with future protocols.

Incident reporting The reporting of incidents in healthcare has dramatically increased in the last ten years. In 2005 there were fewer than 200,000 reported incidents each quarter; and this figure has more than doubled, with more than 400,000 incidents reported between January and March 2016 (NHS Improvement 2017). Back in 2005, all NHS organisations were able to report on the system, but it was not mandatory. However, in 2010 it became mandatory and since then all NHS organisations have had to report to the Care Quality Commission on all incidents that have resulted in severe harm or death. The incidents reported to the National Reporting and Learning System (NRLS) that resulted in severe harm or death are ‘individually reviewed by NHS improvement clinicians’ (NHS Improvement 2017). Fortunately, in the NHS, the number of incidents classified as ‘severe harm or death’ is low, at just 0.53% for January to March 2017; whereas the ‘no harm’ percentage (which describes most reported incidents) is much higher, at 72.8%.

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Therefore, most incidents can be investigated locally by the head of the department. For example, in theatre if an incident occurs that results in no harm it is normally fine for the sister or charge nurse to investigate and make recommendations to prevent a ‘no harm incident’ happening again. When the incident is more serious, and there is harm, there is a requirement not only to report but to commence an investigation. It is not necessarily the patient outcome that determines the seriousness of an incident, as in some cases the outcome may not have changed because of the incident. For example, perhaps the patient was expected to die due to the underlying illness. In cardiothoracic surgery, an incident tends to be classified as serious if the consequences to patients or the organisation are so significant there needs to be a thorough investigation into the cause and what can be done to prevent it happening again in the future. The Serious Incident Framework (NHS Improvement 2015) states that these incidents may include: ●●

Unexpected or avoidable death and injury of one or more people

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Actual or alleged abuse

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A never event

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An incident that prevents an organisation’s ability to deliver acceptable quality of healthcare.

It would be an omission if we did not discuss ‘never events’ relating to the perioperative practitioner. The list for 2015/16 includes 14 incidents that should never have happened (NHS England 2016) and unfortunately, despite the name ‘never’, they are not that uncommon. Between 1st April and 30th September 2017, there were 218 serious incidents in the NHS that fitted the definition of ‘never event’ (NHS improvement 2018). Despite the mandatory inclusion of the WHO Surgical Safety Checklist (described earlier), there were 179 never events directly related to the surgical environment in this six-month period. There were 84 cases of wrong-sided surgery, 62 retained foreign object post-surgery (10 of which were surgical swabs) and 33 wrong implants/prostheses (NHS Improvement 2018). In our experience, never events are followed by a local investigation by a different health group and the incident is, of course, reported to the CQC and NHS Improvement. It is a stressful time for all involved. It is felt that there has been an omission in the ethical duty of care towards the patient. The character of the staff member/s involved may also be questioned (virtue ethics) The reason for the never event must be investigated without bias, and with the focus being on preventing the incident happening again; the individual’s omission or duty of care has to be investigated separately. Reporting a never event should not be done lightly – and care should be taken to gain possession of the full facts. For instance, the author has experience of a practitioner contacting senior management regarding a retained swab as a ‘never event’, when the patient’s chest had in fact been deliberately packed with swabs due to a coagulopathy and were in place to assist patient stability. This caused confusion and detracted from the care that the patient was receiving. However, we all have a professional responsibility to highlight potentially unsafe practice and should be educated (rather than criticised) when we do so incorrectly.

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Whistleblowing We not only have a professional responsibility to report incidents; we must also highlight any areas of concern. In our work as practitioners in perioperative practice, we follow codes of practice (NMC 2015) and standards of conduct (HCPC 2016) to perform our duties safely and effectively. In both these working documents, we are requested to preserve safety. The HCPC asks its members not only to report safety concerns but also to ‘follow up on concerns that have been reported to you’ (HCPC 2016, p. 8) and the NMC (2015, p. 11) code instructs us to ‘act immediately to put right the situation if someone has suffered actual harm for any reason or an incident has happened which had the potential for harm’. There have been many times in the past when ‘whistle-blowers’ have been subjected to unacceptable treatment. For example, Kim Holt was working at Great Ormond Street Hospital in 2007 as a consultant paediatrician when she was suspended by the hospital for three years after raising concerns about staffing levels in the aftermath of the ‘Baby P’ case. ‘Baby P’ had attended the hospital and was seen by a locum consultant who had failed to spot the signs of physical abuse from which Baby P was later to die. Holt reported that she was offered money by the hospital to sign an agreement with a gagging clause which would have prevented her speaking out further. It was nearly four years later that she was eventually able to return to work. Cases like this act as a very visible disincentive for healthcare professionals to voice their concerns, which is very detrimental to efforts to improve patient safety and the quality of care provided. In response to these fears, NHS England published ‘Freedom to speak up – a review of whistleblowing in the NHS’ (Francis 2015). The current policy aims to incorporate the recommendations of the Francis review into whistleblowing in the NHS (Francis 2015) and thereby encourage the raising of concerns. For the policy to work effectively, it would seem that there needs to be a change of culture within healthcare services. We need to move from a culture of fear of reprisals and blame to an acceptance of responsibility, provision of support and a corporate ability to learn from mistakes. A potential resource to help those of us working in the perioperative environment to voice any concerns over safety that we have comes from the aviation industry and is known as Crew Resource Management (CRM). Aviation and surgery are both environments where human error can have a devastating effect, and potentially dangerous and time-critical decisions must be made. CRM focuses on skills such as situational awareness, communication, leadership and decisionmaking and emphasises the need for all team members to be able to question decisions being made and actions being taken. McCulloch et al. (2009) reported their experience of applying CRM in operating theatres and noted that even modest improvements in the non-technical skills of CRM led to large decreases in technical error rates, additionally noting that a flatter hierarchy enables freer communication. Raising concerns should not result in the practitioner being at risk of ‘losing their job or suffering any form of reprisal’ (NHS Improvement 2017); even if it turns out that the member of staff is mistaken, we are encouraged not to wait for proof. This makes sense if the concern is not raised as part of an individual grievance (NHS Improvement 2017). Initially the concern should

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be raised with our line managers. However, if the concern is related to the same line manager, or it is not thought to be appropriate to do this, there are many other routes we can use – such as speaking to a Freedom to Speak Up Guardian or a director with responsibility for whistleblowing, as they have training in this area. The concern can also be raised externally, depending on the type of concern, via Speak Up (Social Enterprise Direct Ltd 2019). When raising a concern, we should adhere to the NHS confidentiality policy (NHS, England 2018) and any information should follow the Caldicott principles (Department of Health and Social Care 2015) when deciding if any patient details should be included.

New techniques Although, as mentioned earlier, we have a duty to ‘do no harm’, to report and assist in the investigation of incidents and be actively involved in safe practice, our codes/standards of conduct also instruct us to keep up to date with current practice (NMC 2015, HCPC 2016). We do this by attending mandatory training, and by involving ourselves in continuing professional development, and this is a requirement of revalidation (NMC 2017). If we want to improve a service by introducing a new technique, this must be implemented in a safe manner. Long gone are the days of a surgeon learning or devising a technique and trying it out on patients without fear of reprisal. We now have a process that must be followed, and this applies to any NICE guidance implementation. The process, although different in each Trust, takes a common form, in that the introduction of nationally agreed guidance (for example, from NICE) should be evaluated by a clinical effectiveness/practice development committee. The teams and other appropriate members of the trust follow implementation guidelines (NICE 2015), which include: ●●

Determining if the guide is applicable

●●

Identifying a clinical lead

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Carrying out baseline assessments

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Formulating an action plan and assessing cost implications

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Reviewing and monitoring.

In practice, the formal procedure to introduce new techniques can be long, frustrating and complex. One example is the introduction of endoscopic vein harvesting. The procedure is now acceptable, with NICE (2014, p. 2) stating that it is ‘adequate to support the use of this procedure provided that normal arrangements are in place for clinical governance’. However, this required a lengthy process. There had to be a presentation to the clinical effectiveness committee, and to attend the committee there had to be a sign-off from the clinical director. This sign-off required an evaluation of implementation cost and the development of a business plan. Once we could prove that the introduction would be cost neutral, we presented and gained permission to introduce the technique, provided the correct audit procedures were followed, for the loan period of the equipment only. Trusts clearly have to follow the correct procedure and evaluate the ethical benefits of every new technique. However, this takes time, which is frustrating for the practitioner who is

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keen to offer the best for their patients as quickly as possible. As practitioners, we see the needs of individual patients. However, the Trust must look at such cases from a utilitarian perspective (asking what will do the most good for the most people) and based on the principle of beneficence (weighing up the benefits as opposed to the potential risks and costs).

Conclusion In the modern healthcare system, the legal and ethical implications are vast; we must follow local, national and global instructions in our quest to treat an ever-larger number of higher-risk patients. The overriding principle of ‘doing no harm’ helps us choose the correct procedure for the individual patient’s illness, operating in a safe manner, while maintaining our core professional values. Despite the introduction of Safe Surgery Saves Lives (WHO 2008), the number of reported incidents continues to rise, although this increase could be partly due to a more open approach to reporting. These events also place a large financial burden on the NHS, through legal cases relating to duty of care and negligence. The pressure on Trusts to perform and meet national targets has in the past led to unsafe practices. We, as professional practitioners, have a duty to highlight these and voice our concerns, and we should not be penalised for doing so. Following the Francis (2015) report, we now have an NHS whistleblowing policy. It is the responsibility of the individual practitioner to keep up to date with practice, using all available resources. There is no place any more for professional staff to ‘cruise’ to retirement. We have to revalidate regularly and it is hoped that new innovations and techniques will be welcomed, as long as ethical principles and guidelines are adhered to.

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References Beauchamp, T. & Childress, J. (2013). Principles of Biomedical Ethics. 7th edn. New York: Oxford University Press. Bergs, J., Hellings, J., Cleemput, I., Zurel, O., De Troyer, V., Van Hiel, M., Demeere, J.L., Claeys, D. & Vandijck, D. (2014). Systematic review and meta-analysis of the effect of the World Health Organization surgical safety checklist on postoperative complications. British Journal of Surgery. 101(3), 150–58. Brazier, M. & Cave, E. (2016). Medicine, Patients and the Law. 6th edn. Manchester: Manchester University Press. Bryden, D. & Storey, I. (2011). Duty of care and medical negligence. Continuing Education in Anaesthesia Critical Care and Pain. 11(4), 124–27. Care Quality Commission (CQC) (2017). Mental Capacity Act and Deprivation of Liberty Safeguards. https://www.cqc.org. uk/guidance-providers/all-services/mental-capacity-act-deprivation-liberty-safeguards (Last accessed 22.2.2019). Chapman, M. (2010). ‘The Snail and the Ginger Beer: The Singular Case of Donoghue v Stevenson’ (Law Report Annual Lecture, 07 July 2010) https//www.lawteacher.net/cases/Donoghue-v-stevenson.php (Last accessed 16.3.2019). Chatterton v Gerson (1981). 1 All ER 257. http://www.ukcen.net/ethical_issues/consent/legal_considerations1 (Last accessed 22.2.2019). Department of Health and Social Care (DHSC) (2015). Guidance – The National Health Service Constitution for England. London: HMSO. https://www.gov.uk/government/publications/the-nhs-constitution-for-england/the-nhs-constitution-forengland (Last accessed 22.2.2019). Francis, R. (2015). Whistleblowing in the NHS: independent review. https://www.gov.uk/government/groups/ whistleblowing-in-the-nhs-independent-review (Last accessed 22.2.2019). General Medical Council (GMC) (2013). Good Medical Practice – Working with doctors Working for patients. https://www. gmc-uk.org/-/media/documents/good-medical-practice---english-1215_pdf-51527435.pdf (Last accessed 22.2.2019). Haynes, A.B., Weiser, T.G., Berry, W.R., Lipsitz, S.R., Breizat, A.S., Dellinger, E.P., Herbosa, T., Joseph, S., Kibatala, P.L., Lapitan, M.C.M., Merry, A.F., et al., for the Safe Surgery Saves Lives study group. (2009). A surgical safety checklist to reduce morbidity and mortality in a global population. The New England Journal of Medicine. 360, 491–99. Head, S.J., Kaul, S., Mack, M.J., Serruys, P.W., Taggart, D.P., Holmes, D.R., Jr. Leon, M.B., Marco, J., Boger, A.J. & Kappetein, A.P. (2013). The rationale for Heart Team decision-making for patients with stable, complex coronary artery disease. European Heart Journal. 34(32), 2510–18. Johnston, C. & Slowther, A. (2004): Introduction Ethical Considerations – UK Clinical Ethics Network. https://www.ukcen. net/uploads/docs/ethical_issues/resources (Last accessed 16.03.2019). Health and Care Professions Council (HCPC) (2016). Standards of conduct, performance and ethics. https://www.hcpc-uk. org/aboutregistration/standards/standardsofconductperformanceandethics/ (Last accessed 22.2.2019). Hind, M. (2005). ‘Accountability and professional practice’ in: K. Woodhead & P. Wicker (eds) A textbook of perioperative care. 1st edn. Edinburgh: Elsevier, Churchill Livingstone. Lord Scarman (1985). Sidaway v Board of Governors of the Bethlem Royal Hospital and the Maudsley Hospital. 1. All ER 643, 649. https://swarb.co.uk/sidaway-v-board-of-governors-of-the-bethlem-royal-hospital-and-the-maudsley-hospital-hl21-feb-1985/ (Last accessed 22.2.2019). McCulloch, P., Mishra, A., Handa, A., Dale, T., Hirst, G. & Catchpole, K. (2009). The effects of aviation-style non-technical skills training on technical performance and outcome in the operating theatre. Quality and Safety Healthcare. 18(2), 109–15. National Health Service (NHS) England (2015). National Safety Standards for Invasive Procedures (NatSSIPs). NHS England: [ref.03974]. https://www.england.nhs.uk/wp-content/uploads/2015/09/natssips-safety-standards.pdf (Last accessed 22.2.2019). National Health Service (NHS) England (2016). Clinical Commissioning Policy: Robotic assisted lung resection for primary lung cancer. NHS England:16024/P. https://www.england.nhs.uk/wp-content/uploads/2018/07/Robotic-assisted-lungresection-for-primary-lung-cancer.pdf (Last accessed 22.2.2019). National Health Service (NHS) England (2018). Raising a concern with NHS England. https://www.england.nhs.uk/ ourwork/whistleblowing/raising-a-concern/ (Last accessed 22.2.2019).

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National Health Service (NHS) Improvement (2015). Serious Incident framework – Supporting learning to prevent recurrence of harm. [ref.03198]. https://improvement.nhs.uk/resources/serious-incident-framework/ (Last accessed 22.2.2019). National Health Service (NHS) Improvement (2017). Guidance notes on National Reporting and Learning System official statistics publications. https://nhsicorporatesite.blob.core.windows.net/green/uploads/documents/Guidance_notes_on_ NRLS_officia_statistics_Sept_2017.pdf (Last accessed 22.2.2019). National Health Service (NHS) Resolution (2017). Annual report and accounts 2016/17. [HC 172]. https://resolution.nhs.uk/ wp-content/uploads/2017/07/NHS-Resolution-Annual-report-and-accounts-2016_17.pdf (Last accessed 22.2.2019). National Health Service (NHS) Improvement (2018). Never Events reported as occurring between 1 April 2016 and 31 March 2017- final update. https://improvement.nhs.uk/documents/2347/Never_Events_1_April_2016_-_31_March_2017_ FINAL_v2.pdf (Last accessed 22.2.2019). National Institute for Health and Care Excellence (NICE) (2014). Endoscopic saphenous vein harvest for coronary artery bypass grafting. Interventional procedures guidance [IPG494]. https://www.nice.org.uk/guidance/ipg494 (Last accessed 22.2.2019). National Institute for Health and Care Excellence (NICE) (2015). Practical steps to improving the quality of care and services using NICE guidance. Into practice guide/guidance and guidelines/NICE [PMG30]. https://intopractice.nice.org.uk/ practical-steps-improving-quality-of-care-services-using-nice-guidance/index.html (Last accessed 22.2.2019). National Patient Safety Agency (NPSA) (2009). Recommendations from the National Patient Safety Agency alerts that remain relevant to the Never Events list 2018. London: NPSA; Patient Safety Alert. https://improvement.nhs.uk/ documents/2267/Recommendations_from_NPSA_alerts_that_remain_relevant_to_NEs_FINAL.pdf (Last accessed 22.2.2019). Nursing and Midwifery Council (NMC) (2012). NMC and GMC release joint statement on professional values. https://www.nmc.org.uk/news/news-and-updates/nmc-and-gmc-release-joint-statement-on-professional-values/ (Last accessed 22.2.2019). Nursing and Midwifery Council (NMC) (2015). The Code: Standards of conduct, performance and ethics for nurses and midwives. London, NMC. Nursing and Midwifery Council (NMC) (2017). Revalidation/Resources: Guidance and Information. http://revalidation.nmc. org.uk/download-resources/guidance-and-information (Last accessed 22.2.2019). Pickering, S.P., Robertson, E.R., Griffin, D., Hadi, M., Morgan, L.J., Catchpole, K.C., New, S., Collins, G. & McCulloch, P. (2013). Compliance and use of the World Health Organization checklist in U.K. operating theatres. The British Journal of Surgery. 100(12), 1664–70. Pirie, S. (2012). Legal and professional issues for the perioperative practitioner. Journal of Perioperative Practice. 22(2), 57–62. Royal College of Nursing (RCN) (2018). Staffing for Safe and Effective Care: Nursing on the Brink. London: RCN. Social Enterprise Direct Ltd (2019) Speak Up. https://speakup.direct/ (Last accessed 8.5.2019). World Health Organisation (WHO) (2008). The second global patient safety challenge: Safe Surgery Saves Lives. World Alliance for Patient Safety. http://www.who.int/patientsafety/safesurgery/knowledge_base/SSSL_Brochure_finalJun08.pdf (Last accessed 22.2.2019). World Health Organisation (WHO) (2009). WHO Surgical Safety Checklist. http://www.who.int/patientsafety/safesurgery/ checklist/en/ (Last accessed 22.2.2019). Windecker, S., Stortecky, S., Stefanini, G.G., da Costa, B.R,, Rutjes, A.W., Di Nisio, M., Silletta, M.G., Maione, A., Alfonso, F., Clemmensen, P.M., Collet, J.P., Cremer, J., Falk, V., Filippatos, G., Hamm, C., Head, S., Kappetein, A.P., Kastrati, A., Knuuti, J., Landmesser, U., Laufer, G., Neumann, F.J., Richter, D., Schauerte, P., Sousa Uva, M., Taggart, D.P., Torracca, L., Valgimigli, M., Wijns, W., Witkowski, A., Kolh, P. & Jüni, P. (2013). Revascularisation versus medical treatment in patients with stable coronary artery disease: network meta-analysis. British Medical Journal (Clinical research education). 23(348), 3859.

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3 Operating theatre preparation for cardiothoracic surgical procedures Teresa Hardcastle and Bibleraj Gnanasekaran

Introduction Most cardiothoracic operating theatres worldwide commence surgery at around 7.30am, due to the length and complexity of the surgical procedures required. All equipment should be checked and ready to use (prior to the patient arriving in the anaesthetic room and the operating theatre) by the anaesthetic practitioner and the scrub team. Before starting the operating list, all members of the team who will be present for the procedures meet to discuss each patient in depth. The team includes anaesthetists, surgeons, registrars, surgical care practitioners, the anaesthetic practitioner, the scrub team, perfusionists and students. This meeting is known as the team brief and it is part of the ‘Five Steps to Safer Surgery’ and has been mandatory in all operating theatre departments in the United Kingdom since 2010 (WHO 2009). The aim of this briefing is for each member of staff to introduce themselves and their role and most importantly to discuss each patient individually, their comorbidities, and the anaesthetic and surgical equipment requirements for each procedure. This briefing has been shown to improve team working, communication and patient safety (Hardcastle 2013). Most operating theatres in the UK are built with an anaesthetic room, where the patient is anaesthetised and prepared for surgery before entering the operating theatre. One of the fundamental responsibilities of the anaesthetic practitioner is to prepare the anaesthetic room and operating theatre for surgery, while the scrub team prepare the appropriate instrumentation and equipment required for the surgical procedures. This involves: ●●

Ensuring that the operating theatre temperature and humidity are set within normal limits

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Ensuring that the operating theatre ventilation is working

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Checking the operating theatre lights

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Checking the anaesthetic machines

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Preparing airway equipment and adjuncts

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Preparing patient monitoring equipment

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Preparing intravenous, arterial and central venous monitoring equipment

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Checking and making available a variety of drugs required by the anaesthetist

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Checking the operating theatre table and preparing specialist patient positioning equipment

Checking and preparing specialist equipment such as transoesophageal probe, machine, and heart and lung machine.

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Temperature and humidity The operating theatre temperature and humidity are both controlled by the air conditioning system. The normal temperature of the operating theatre is ideally set at 20–23° Centigrade or Celsius (Phillips 2016, p. 183). The environment should be comfortable for staff to work in but also needs to take into consideration the requirements of the patient. The humidity should be controlled, between 50 and 60%, to inhibit the growth of micro-organisms (Al-Benna 2012, p. 320). A high level of humidity creates an uncomfortable environment for staff to work in, whereas humidity that is too low can increase the risk of an explosion due to a static charge of electricity.

Ventilation The ventilation system delivers filtered air under positive pressure. This can be visually checked on a central control panel within the operating theatre. The ventilation system is one important factor in reducing the incidence of surgical site infection. The air flow should be delivered in a downward directional flow towards floor and exhaust panels (Spry 2015). There are two types of ventilation system available: plenum and laminar. Plenum ventilation produces, on average, 20 air changes every hour (Humphreys 2012, p.71). Laminar ventilation, also known as ‘Ultra Clean’, is commonly used in modern operating theatres, especially orthopaedic theatres. Laminar ventilation delivers highly filtered positive air using special filters (known as high-efficiency particulate air filters) that remove airborne particles. Air changes can range from 400 to 600 every hour (Kotcher-Fuller 2013, p. 58).

Lighting The operating theatre has various lighting sources. These range from ceiling fixtures to the overhead, ceiling-mounted main surgical light. The operating theatre light should be ‘shadow less, produce the blue-white colour of daylight, produce minimum heat and be freely adjustable to any position or angle with either a vertical or horizontal range of motion’ (Phillips 2017, p.188). Good operating lighting is essential for good surgical access. The operating lights must therefore be checked prior to use. They need to be in good condition and all in working order. If any lights fail, this should be reported immediately to the medical engineering department of the local trust or organisation.

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Anaesthetic machine As patients are commonly anaesthetised in an anaesthetic room, anaesthetic machines can be found both in the anaesthetic room and the operating theatre. It is one of the anaesthetic practitioner’s roles to check both machines prior to their use and at the start of each operating list, following the safety guidelines (AAGBI 2012). This is a joint responsibility with the anaesthetist. The anaesthetist is also responsible for checking the anaesthetic machine prior to its use (AAGBI 2012). These checks ensure that all aspects of the anaesthetic machine are functioning safely, including: ●●

Medical gas supply and delivery

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Breathing systems

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Vaporisers

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Ventilators

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Suction apparatus

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Scavenging system to collect waste gases.

The appropriate volumes must also be set on ventilators and all audible alarm systems on the anaesthetic machines must be tested. A record of these checks is then kept with each anaesthetic machine. These vital checks help ensure the safety of patients when they are at their most vulnerable during anaesthesia (see Figure 3.1).

Figure 3.1: The anaesthetic machine in the theatre setting

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Airway equipment and adjuncts A full range of standard airway equipment should be checked and made available at the start of every operating list (Royal College of Anaesthetists 2018). The anaesthetic practitioner will therefore prepare the following: A selection of different size face masks (see Figure 3.2) to ensure a close fit to the face and prevent gas leak.

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Oropharyngeal airways size 2, 3 and 4. When inserted lies over the tongue to prevent it from covering the epiglottis (see Figure 3.2).

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A variety of laryngoscopes with appropriately sized blades to aid visualisation of the vocal cords on direct laryngoscopy. Popular are the Macintosh, Miller and the McCoy blade which has a hinged tip to lift the epiglottis to improve the view of the larynx. Choice of laryngoscope blade used is usually the anaesthetist’s preference (see Figure 3.2).

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Supraglottic airway devices, Laryngeal Mask Airways size 3 to 5 (see Figure 3.3). The LMA was first developed by Archie Brain in 1981 and was used for spontaneous breathing as an alternative to bag, mask ventilation. They are designed to sit over the opening in the larynx. They have subsequently been used for Positive Pressure Ventilation (Gwinnutt & Gwinnutt, 2017). Modifications have been made to the original design, for example the development of the proseal and igel® LMAs. They were first manufactured as reusable but now are available as disposable items. The choice of LMA will depend on anaesthetist’s preference, and availability. It is not routine for an LMA to be used in cardiac or thoracic anaesthesia. However, LMAs are a valuable airway adjunct in the case of a difficult airway or in an emergency situation (Difficult Airway Society 2015). ●●

The size of the required LMA will depend on gender and weight of the patient.

Endotracheal tubes size 7.0 to 9.0mm with an inflatable cuff will also need to be readily available (see Figure 3.4).

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These sizes are available in 0.5mm ranges – for example, 7.5mm.

The actual size of tube required for the patient will depend on gender and weight. Commonly 7.5–8mm for a female and 8.5–9mm for a male.

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The length of the ETT will require cutting depending on the gender and weight of the patient. Commonly 21cm for a female and 22cm for a male.

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For thoracic surgery, double lumen endotracheal tubes to facilitate one lung ventilation. The lung to be ventilated will depend on the site of operation and they are available in a variety of sizes.

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Equipment for the management of anticipated or unexpected airway difficulties such as bougies and stylets.

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Other equipment that should also be checked in accordance with departmental policies and made available in the ‘difficult airway trolley’. The trolley will contain a range of airway devices

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– for example, flexible intubating laryngoscopes, intubating LMAs, Aintree catheters and surgical cricothyroidotomy kits to use in the event of an anticipated or unanticipated airway difficulty (see Figure 3.5). The resuscitation equipment and defibrillator must also be available and checked, in accordance with departmental policies, in the event of an emergency (AAGBI 2015).

Face masks ET tubes Airways

Catheter mount

Laryngeal blades

Eye pads

Figure 3.2: Different sizes of face masks, laryngeal blades, airways and eye pads

Figure 3.3: Different sizes of laryngeal mask airways

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Figure 3.4: Different sizes of endotracheal tube

Figure 3.5: The disposable laryngoscope with monitor for difficult airway intubation

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Operating theatre preparation for cardiothoracic surgical procedures

Basic patient monitoring During any surgical procedure the anaesthetist must closely monitor the patient’s physiological condition and level of anaesthesia – and act immediately on any variance that occurs. Monitoring is therefore an essential component in the safe conduct of anaesthesia (Checketts et al. 2016, p. 85). As a minimal standard of monitoring, the Association of Anaesthetists of Great Britain and Ireland (2015) recommends: An ECG, which provides information on heart rate and rhythm. This will normally be a 5-lead ECG rather than the standard 3-lead ECG. By applying the 5-lead ECG as standard, the anaesthetist can monitor the myocardium for ischaemia.

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Pulse oximetry, obtained via a probe (which is placed either on a finger or earlobe) containing a light-emitting diode and a photodetector. This will determine peripheral arterial oxygenation by the amount of light that is absorbed by the blood.

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Non-invasive blood pressure measurement (NIBP), taken at intervals via a pneumatic cuff ‘commonly placed around the arm over the brachial artery’ (Gwinutt & Gwinutt 2017, p. 38)

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Capnometry, which is a a non-invasive measurement of exhaled carbon dioxide used routinely during induction and maintenance of anaesthesia. This indicates that the ET tube is correctly placed in the trachea and provides information concerning the efficiency of alveolar ventilation (Gwinutt & Gwinutt 2017). Capnometry will display an alarm if there is an anaesthetic tubing disconnection and will also indicate when the patient begins to rebreathe. Temperature monitoring: during anaesthesia a patient’s temperature will drop and should be monitored, according to the National Institute for Health and Care Excellence (NICE 2016). This is particularly important in cardiac surgery because the patient will be on bypass and the patient’s temperature will be cooled down to protect the organs. A core or nasal temperature probe should therefore be inserted to monitor the patient’s temperature during the procedure. This is recorded in the patients’ anaesthetic chart and on the electronic data monitoring equipment.

The anaesthetic practitioner must ensure that all this equipment is prepared and functioning. This includes checking the availability of different sized NIPB cuffs, ECG electrodes, pulse oximeter probe, capnometry analyser and temperature probe. However, due to the complexity of cardiothoracic procedures, the anaesthetist requires more accurate invasive continuous haemodynamic monitoring, to detect and treat any vital changes in the patient’s condition early. ●●



Invasive arterial blood pressure (IABP) monitoring is achieved by inserting a cannula (see Figures 3.6 and 3.7) into a peripheral artery, such as the radial artery, following antiseptic non-touch technique (ANTT) guidelines. A suture may be used to secure the arterial cannula and a dressing is applied. The cannula is then connected to a sterile fluid-filled system which contains 0.9% normal saline, with or without heparin, within a pressure bag. The pressure bag should be pressurised to 300mgHg. A transducer is connected, which converts the

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pulsatile pressure into a waveform, providing systolic, diastolic and mean arterial blood pressure measurements. The arterial cannula also offers a means of providing an arterial sample for vital blood gas analysis periodically throughout the procedure. ●●



Central venous pressure (CVP) monitoring measures the pressure in the right atrium of the heart and is a means of reflecting the circulating blood volume (Scales & Fernandes 2010). The anaesthetist measures it by inserting a CVP catheter (using strict ANTT) into the right atrium or superior vena cava via the internal jugular vein, subclavian vein or femoral vein. The femoral vein has the highest risk of infection but it may be used if other veins cannot be used – for example, in patients who have had previous carotid surgery (Gallagher & Poovathoor 2010). To reduce complications when inserting the CVP catheter, the anaesthetic practitioner should have available a two-dimensional ultrasound (NICE 2002). By using the ultrasound scan, the anaesthetist can locate the correct vein prior to insertion. The catheters used can have multiple lumens to facilitate continuous CVP monitoring but also provide access for infusions. The anaesthetist will then suture the CVP catheter in place and apply a dressing. The catheter is connected to a sterile fluid-filled system which contains 0.9% normal saline in a pressure bag. The pressure bag should also be pressurised to 300mgHg. Another transducer is connected and provides a waveform pressure measurement. The normal range of CVP is 0–8cm H2O.

The anaesthetic practitioner will need to provide and prepare this equipment, ensuring that the principles of ANTT have been adhered to, according to local departmental policies (see Figures 3.8 and 3.9). Practitioners should make sure that there are no air bubbles in the transducer kits or on the pressure monitoring lines. If there are any microbubbles in either the arterial or CVP transducer kits this will lead to damp tracing while monitoring the patient pressures and will not measure the accurate patient pressures.

Intravenous cannulas (IV) and IV fluids Different sizes of IV cannulas will be required by the anaesthetist for intravenous access. The size of the cannula used will depend on the size of the vein (see Figure 3.10). All IV cannulas should be secured correctly with the appropriate IV dressing because, once the arms are positioned and covered under the sterile drape, it will be impossible to see the cannula or any bleeding. During the surgical procedure the anaesthetist will need to replace any fluids lost during surgery intravenously and maintain the patient’s homeostasis. The ‘three types of fluids administered are crystalloids, colloids and if necessary, blood and its components’ (Gwinutt & Gwinutt 2017, p. 61). IV administration sets will therefore need to be prepared by the anaesthetic practitioner prior to the commencement of anaesthesia, using strict ANTT as per local policies and procedures. Infusion devices, which deliver accurate and constant levels of fluids and drugs, will also need to be made available to the anaesthetist. Hypovolaemia during surgery is a potential risk, which would require the circulating blood volume to be restored quickly to maintain normal haemostasis. The anaesthetic practitioner will therefore need to check and prepare a rapid infusion pump. In an emergency, the pump will deliver large amounts of IV fluids at rapid flow rates to the patient.

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Operating theatre preparation for cardiothoracic surgical procedures

Hand support roll

Plaster

Dressings

Different sizes of arterial cannula

Blood gas syringe

Extension line

IV drip set

Arterial and transducer set

Figure 3.6 and 3.7: The items required for arterial cannula insertion, used to monitor the arterial blood pressure

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Three way stopcocks

CPV set

Swab Dressings

Syringe Suture and blade Chlorohexadine cleaning stick

Figure 3.8: The items required for the CVP line insertion Guide wire

Central line

Dressing

Three way stopcocks

Sterile sheet

Figure 3.9: The set-up of the CVP line according to ANTT protocols

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Operating theatre preparation for cardiothoracic surgical procedures

Swabs

Dressings

Cleaning sticks

Different sizes of cannula 22D 20G 18G 16G

14G

Figure 3.10: The items required for IV-line insertion

Drugs As part of the normal preparation for the operating list, the anaesthetic practitioner will need to check and ensure that a range of drugs are made available for the anaesthetist. These will include basic anaesthetic drugs: ●●

Induction agents

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Muscle relaxants

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Opioids

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Antiemetics

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Antibiotics

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Vasopressors

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Common emergency drugs such as suxamethonium chloride, atropine and epinephrine

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Other specialist drugs required – for example, anticoagulants.

Operating table and specialist positioning equipment The operating table should be checked to ensure that it is in good working condition, can be tilted if necessary and is charged ready for use. Most operating tables are electrically controlled and require charging overnight when not in use. If a patient scheduled for a procedure has a high body mass index (BMI), then a bariatric operating table may be required to accommodate a larger patient safely.

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The aim of positioning patients for surgical procedures is to ensure optimal exposure for the surgeon and enable the anaesthetist to maintain the patient’s airway and have easy access to any fluid and monitoring lines (Watson 2011). The surgical positioning should of course avoid any injury to the patient and should not compromise any physiological functions (Phillips 2016). For thoracic procedures, it is necessary to position the patient laterally. Therefore, table attachments are required to position the patient safely. The table attachments should be checked, and risk assessed, prior to use. With any cardiothoracic procedure, care must be taken to ensure that pressure areas are protected with the use of pressure-relieving devices.

Specialist equipment Other specialist equipment may need to be prepared, depending on the surgical procedure being undertaken.

Bronchoscope In thoracic surgery, a flexible bronchoscope (see Figure 3.11) is often used in the anaesthetic room after the insertion of a double lumen ET tube for single lung ventilation. This enables the anaesthetist to confirm the correct placement of the ET tube. The surgeon also uses it for diagnostic purposes and to confirm the abnormal findings before continuing with the surgery.

Biopsy port

Control section

Flexible part

Suction Universal cord

Lens and CCD chip

Figure 3.11: The flexible bronchoscope used for diagnostic bronchoscopy before the surgery

Trans oesophageal echocardiography (TOE) In cardiac surgery, TOE (see Figure 3.12) is used and provides real-time information, assessing cardiac anatomy and physiology during surgery. TOE (see Figure 3.13) can indicate many problems such as tamponade and poor ventricular function. It contains an ultrasonic transducer which is inserted into the patient’s oesophagus. It works by ‘measuring sound waves which via a transducer creates a visual image’ of the heart’s movements (Siefert 2015, p. 940).

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Operating theatre preparation for cardiothoracic surgical procedures

Probe shaft Probe tip

Plug socket Probe control Probe handle Protecting sheath cover

Figure 3.12: The transoesophageal probe

Display monitor

Control board Ultrasound gel

Control unit

Probe socket

Figure 3.13: The TOE machine

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References Al-Benna, S. (2012). Infection Control in Operating Theatres. Journal of Perioperative Practice. 22(10), 318–22. Association of Anaesthetists of Great Britain and Ireland (AAGBI) (2012). Safety Guideline. Checking of Anaesthetic Equipment. London: AAGBI. Association of Anaesthetists of Great Britain and Ireland (AAGBI) (2015). Recommendations for monitoring during anaesthesia and recovery. London: AAGBI. Checketts, M.R., Alladi, R., Ferguson, K., Gemmell, L., Handy, J.M., Klein, A.A., Love, N.J., Misra, U., Morris, C., Nathanson, M.H., Rodney, G.E., Verma, R. & Pandit, J.J. (2016). Recommendations for standards of monitoring during anaesthesia and recovery 2015: Association of Anaesthetists of Great Britain and Ireland. Anaesthesia. 71(1), 85–93. Difficult Airway Society (DAS) (2015). DAS guidelines for management of unanticipated difficult intubation in adults 2015. https://www.das.uk.com/guidelines/das_intubation_guidelines (Last accessed 24.2.2019). Gallagher, C.J. & Poovathoor, S. (2010). ‘Vascular access procedures’ in: A. Jeremias & D.L. Brown (eds) Cardiac Intensive Care. Philadelphia: Elsevier. 545–57. Gwinutt, M. & Gwinutt, C. (2017). Clinical Anaesthesia. Lecture Notes. 5th edn. Chichester: Wiley Blackwell. Hardcastle, T. (2013). WHO safe surgery: how well are we doing? Journal of Operating Department Practitioners. 1(1), 36–39. Humphreys, D. (2012). Surgical site infection, ultraclean ventilated operating theatres and prosthetic surgery: where are we now? Journal of Hospital Infection 81 (2), 71–72. Kotcher-Fuller, J. (2013). Surgical Technology. Principles and Practice. 6th edn. Philadelphia: Saunders. National Health Service (NHS) Improvement. (2018). Learning from patient safety incidents. https://improvement.nhs.uk/ resources/learning-from-patient-safety-incidents/ (Last accessed 24.2.2019). National Institute for Care and Health Excellence (NICE) (2002). Guidance on the use of ultrasound locating devices for placing central venous catheters. https://www.nice.org.uk/guidance/ta49 (Last accessed 24.2.2019). National Institute for Care and Health Excellence (NICE) (2016). Hypothermia: prevention and management in adults having surgery. https://www.nice.org.uk/guidance/cg65 (Last accessed 24.2.2019). Phillips, N. (2016). Berry & Kohn’s Operating Room Technique. 13th edn. Missouri: Elsevier. Royal College of Anaesthetists (RCOA) (2018). Preparing your basic anaesthetic equipment. https://www.e-lfh.org.uk/elearning-sessions/rcoa-novice/content/started/theatre.html (Last accessed 24.2.2019). Scales, K. & Fernandes, T. (2010). Central venous pressure monitoring in clinical practice. Nursing Standard. 24(29), 49–55. Siefert, P.C. (2015). ‘Cardiac Surgery’ in: J. Rothrock (ed.) Alexander’s Care of the Patient in Surgery. 15th edn. St Louis: Elsevier. 931–1007. Spry, C. (2015). ‘Infection Prevention and Control’ in: J. Rothrock (ed.) Alexander’s Care of the Patient in Surgery. 15th edn. St Louis: Elsevier. 69–123. Watson, D. (2011). Interoperative Positioning: Risk Reduction Strategies. Mansfield: Covidien. www.medtronic.com/ content/dam/covidien/library/us/en/product/patient-positioning-products/H6861%20Positioning%20Bookletr%20 rev%2011_14.pdf (Last accessed 24.2.2019). World Health Organisation (WHO) (2009). WHO Surgical Safety Checklist. http://www.who.int/patientsafety/safesurgery/ checklist/en/ (Last accessed 19.2.2019).

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4 Cardiac and thoracic anatomy Andrew Brazier and Charlene Tennyson

Cardiac anatomy Introduction The heart is the major organ of the mediastinum and is contained within the middle mediastinum, enclosed by the pericardium (Figure 4.1). It is a dual muscular pump, forcing blood around the pulmonary and systemic circulations. The heart can be split into a right side and left side that act simultaneously but on separate circulatory systems. The heart can also be divided into four chambers: two on the right and two on the left. These chambers all have a valve at their exit to prevent back flow of blood. Both sides have an atrium, which receives blood from the venous system; and a ventricle, which propels blood around the associated circulatory system. The right side pumps blood to the lungs around the pulmonary circulation, while the left side pumps blood around the rest of the body via the systemic circulatory system. The two systems have different lengths and pressures and the two sides of the heart therefore have slightly different morphologies to accommodate this (Moorjani, Viola & Ohri 2011b, Anderson & Cook 2014, Drake, Vogl & Mitchell 2015). Although the heart can be described as ‘left and right’ or as’ four chambers’, it is all one organ formed by a continuous network of specialised muscle fibres – the myocardium. Within the myocardium runs the conduction system, and the connective tissue of the cardiac skeleton. The muscle fibres and the path of the cardiac conducting system are oriented so that contraction of the muscle is synchronised to efficiently expel blood from the heart (Drake, Vogl & Mitchell 2015).

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A

B C

D E

F G

Figure 4.1: Anterior view of the human heart with parts labelled. A: Sternal retractor B: Pericardium C: Right Atrium D: SVC E: Aorta F: Right ventricle G: Pulmonary artery

Pericardium The fibrous pericardium (the outermost layer of the pericardium) forms the boundary of the middle mediastinum. The cavity within the fibrous pericardium, which houses the heart, is lined by serous pericardium. The serous pericardium can be further subdivided into the parietal and visceral layers; the parietal layer is attached to the inner surface of the fibrous pericardium and the visceral layer, known as the epicardium, is closely attached to the heart (Sinnatamby 2011). The parietal and visceral layers are continuous with each other at the sites where blood vessels penetrate the pericardium and along folds of pericardium, between these vessels, posterior to the heart, that tether it in position. These folds create two pockets within the pericardium: the oblique sinus, posterior to the left atrium and bounded by the inferior vena cava, the four pulmonary veins and the folds of pericardium connecting them; and the transverse sinus, a smaller pocket lying posterior to the aorta and pulmonary trunk, bound by the superior vena cava, the two superior pulmonary veins and the fold of pericardium connecting them (Moorjani, Viola & Ohri 2011b). The space between the two layers of serous pericardium, including the two sinuses, is called the pericardial space. This space is usually very small, containing approximately 5–10ml fluid, which is continuously secreted and absorbed by the mesothelial cells that line the serous pericardium (Moorjani, Viola & Ohri 2011b). The fibrous pericardium is inelastic and maintains a fixed volume. This means that, in the event of a build-up of fluid within the pericardium, such as a bleed into the pericardial space or an inflammation causing a pericardial effusion, the heart is compressed and its function restricted (Okum & DeAnda Jr 2014).

Chambers of the heart The heart is composed of four chambers: two atria (left and right) and two ventricles (left and right). Atria are collecting chambers, receiving blood that is returned to the heart. Ventricles are pumping chambers,

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with thick muscular walls that contract to eject blood at high pressure. The right-sided chambers collect blood from the systemic circulation and pump it around the pulmonary circulation. The left-sided chambers collect blood from the pulmonary circulation and pump it around the systemic circulation. The different demands of each system, and the different embryological origin and requirements of each chamber, influence their structure (Sinnatamby 2011, Anderson & Cook 2014).

Right atrium The right atrium is a deformed vertical tube at the right border of the heart. Posteriorly, its inner surface is smooth and continuous from the inferior vena cava (IVC) inferiorly to the superior vena cava (SVC) superiorly. Anteriorly, there is a triangular pouch (the right atrial appendage or auricle) which curves medially to slightly overlie the aortic root. The interior surface of the anterior wall is trabeculated by ridges of pectinate muscle. The margin between these distinct interior surfaces is delineated by a smooth ridge of muscle, running on the lateral wall from the anterior edge of the SVC orifice above to the anterior edge of the IVC orifice below, called the crista terminalis. At the inferior end of the right atrium, just medial to the opening of the IVC, is the opening of the coronary sinus. Where these two orifices come together, each is guarded by a small thin fold of fibrous tissue: the eustachian valve guarding the IVC, and the thebesian valve guarding the coronary sinus. They join at a common fibrous ridge on the posterior atrial wall, the tendon of Todaro. The medial surface of the right atrium has the right atrioventricular valve, the tricuspid valve, which separates the right atrium from the right ventricle. The septum between the right atrium and the left forms its posterior wall. A small oval-shaped depression, called the fossa ovalis, is visible in the septum. The tissue within this oval makes up the septum primum. The pronounced superior border of this oval, called the limbus, marks the extent of a deep infolding of intra-atrial wall that provides a double layer septum between the right and left atria, the septum secundum. From outside the heart, these two layers can be separated to allow the surgeon access to the left atrium without entering the right. If the septa primum and secundum are not properly fused, they may overlie each other but permit a pathway between the right and left atrium, a persistent foramen ovale. In this instance, the way the septum secundum overlies the septum primum forms a one-way valve between the atria, with the higher pressure in the left atrium holding it shut. This is therefore usually a benign asymptomatic condition but it can have implications if the haemodynamics change (Moorjani, Viola & Ohri 2011b, Sinnatamby 2011, Anderson & Cook 2014).

Right ventricle The right ventricle lies to the left and slightly anterior to the right atrium. Its anterior free wall constitutes the major component of the anterior surface of the heart. In cross-section, it is crescent-shaped, as the interventricular septum bulges slightly into the right ventricle. This reflects the lower pressure in the pulmonary circulation, and the reduced radial force that right ventricular walls are required to produce to eject blood. It is helpful to consider the structure of ventricles in three parts: the inlet, the apical trabecular and the outlet components. Blood travels in through the inlet, and is directed down towards the apex, where it makes a sharp turn and is directed superiorly into the outflow

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tract. The inlet from the right atrium is guarded by the tricuspid valve. The apical trabecular component is so named because its inner surface is notable for the multiple ridges and bridges of muscle, called trabeculae, that cover it. In the right ventricle, the trabeculae are large and distinct – coarse trabeculae. The pattern of these trabeculae is mostly variable but there is some commonality found between patients. The most consistent trabeculae have distinct names and functions. Papillary muscles are portions of muscle that protrude from the inner surface of the ventricle, with their origin in the ventricular wall and their insertion into the chordae that suspend the tricuspid. The right ventricle has up to three papillary muscles: The anterior papillary muscle, the largest and most consistent papillary muscle, on the anterior wall, supporting the anterior leaflet and commissure between the anterior and posterior leaflets

●●

The medial papillary muscle, attached to the interventricular septum and inserting into the chordae of the septal leaflet and zone of apposition between the septal and anterior leaflets

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The posterior papillary muscle, which arises from the posterior wall and anchors the chordae of the posterior leaflet and septal-posterior commissure.

●●

Another consistent trabecula is the septomarginal trabecula. This arises from the septum at the base of the medial papillary muscle, courses towards the apex and bridges the ventricle, to attach to the anterior wall at the anterior papillary muscle. The bridging portion of this trabecula is called the ‘moderator band’ and the portion on the septum the ‘septal band’. The parietal band is a ridge of muscle separating the tricuspid valve from the outflow tract. It is continuous with the septomarginal trabecula on the interventricular septum. The outlet of the right ventricle is a smooth-walled muscular sleeve known as the infundibulum (Moorjani, Viola & Ohri 2011b; Sinnatamby 2011; Anderson & Cook 2014; Harington, Mora & Wu 2014; Drake, Vogl & Mitchell 2015).

Left atrium A simpler structure than the right atrium, the left atrium is a smaller, flatter chamber, corresponding to the posterior surface of the heart. Its posterior wall is smooth and it has two venous orifices on each side where the right and left superior and inferior pulmonary veins drain. To the right, its anterior wall forms the inter-atrial septum, with a corresponding depression at the site of the fossa ovalis. To the left, there is a pocket of trabecular muscle, which wraps around the right ventricular outflow tract: the left atrial appendage. The left atrial appendage can take various shapes. One study categorised these shapes into ‘chicken wing’, ‘cactus’, ‘wind sock’ and ‘cauliflower’. It is often indicated as a site for clot formation in atrial fibrillation – a cause of stroke. The ‘cauliflower’ morphology is thought to be associated with the highest risk; ‘chicken wing’ the least. The appendage can be surgically excluded in an attempt to attenuate stroke risk. On the anterior wall of the left atrium is the opening into the left ventricle, occupied by the left atrioventricular valve, known as the mitral valve (Moorjani, Viola & Ohri 2011b; Sinnatamby 2011; Di Biase et al. 2012; Anderson & Cook 2014; Harington, Mora & Wu 2014).

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Left ventricle The mitral valve occupies the inlet of the left ventricle, with the apical trabecular component anchoring it via chordae and two papillary muscles (the anterolateral and the posteromedial papillary muscles), lying in the anatomical positions described by their names. Both muscles have chordae to both mitral valve leaflets but the anterolateral muscle supplies more to the anterior leaflet, and the posteromedial more to the posterior leaflet. The trabeculae are finer in the left ventricle than the right and the chamber is slightly bigger. The outlet of the left ventricle (the aortic antrum) is smooth walled and runs vertically, posterior to the infundibulum. Medially, the thin-walled membranous septum separates the left ventricle from the right atrium, just below the aortic valve. Posteriorly, between the anterior leaflet of the mitral valve and the aortic valve, is a non-muscular, fibrous area forming the aorto-mitral curtain. In cross-section, through the trabecular zone, the left ventricle is circular, with thick walls and a muscular septum. This allows maximum radial force to expel blood (Moorjani, Viola and Ohri 2011b; Sinnatamby 2011; Anderson & Cook 2014; Harington, Mora and Wu 2014; Drake, Vogl & Mitchell 2015).

Arterial blood supply The blood supply to the myocardium is derived from the coronary arteries, which are the first branches of the ascending aorta. The word coronary comes from the Latin corona, which means ‘crown’ and describes how the arteries appear to encircle the heart.
There are two main arteries, the left coronary artery and the right coronary artery, which arise from the left and right coronary sinuses respectively, just superior to the aortic valve. It is important to be aware that there are variations in the coronary anatomy. The coronary arteries are often visible on the surface of the heart, covered just by epicardium. They may, however, be covered by epicardial fat, or have a deeper intramuscular course (Moorjani, Viola & Ohri 2011b).

Left coronary artery

LMS

OM branch

Septal branches

The left coronary artery begins at the left coronary ostium on the posterior surface of the aorta as the left main stem (see Figure 4.2).

Diagonal branch

LAD

Figure 4.2: The coronary angiogram of the left coronary artery, with its branches

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It takes a course between 10 and 40mm in length, posterior to the pulmonary trunk, between the pulmonary trunk and the left atrial appendage in the atrioventricular groove. Once it appears from behind the pulmonary trunk, it bifurcates into two main branches: the left anterior descending (LAD) artery and the circumflex artery. Occasionally a third branch arises, off the left main stem, and this is known as the ramus intermedius (intermediate) coronary artery (Moorjani, Viola & Ohri 2011b; Rushing & Yuh 2014).

Left anterior descending artery The LAD courses towards the apex of the heart anteriorly and inferiorly in the anterior interventricular groove, overlying the interventricular septum. It gives rise to diagonal and septal branches. The diagonal branches travel laterally to the left to supply the anterolateral wall of the left ventricle (usually 2–6 diagonal branches) and the septal branches (between 3 and 5) penetrate deep into the muscle to supply the anterior two-thirds of the interventricular septum. The LAD can be further divided into thirds. The proximal third begins after the left main stem and terminates at the first septal branch. The middle third arises from the first septal to the start of the last diagonal branch; and finally the distal third is found between the last diagonal and where the LAD terminates at the apex. Occasionally the LAD will also give right ventricular branches, which travel medially to supply the anterior surface of the right ventricle (Moorjani, Viola & Ohri 2011b; Sinnatamby 2011).

Circumflex artery The circumflex artery runs along the atrioventricular groove and passes laterally to the left to the posterior surface of the heart supplying the left atrium and left ventricle.
The main branches are the obtuse marginal arteries which travel anteriorly to supply the lateral wall of the left ventricle and the anterolateral papillary muscle of the mitral valve. There are smaller left atrial branches that travel posteriorly to supply the left atrium. In 40% of patients the circumflex artery will also give a branch to supply the sinoatrial node, and in 10 to 15% of patients it gives a branch to supply the atrioventricular node (Moorjani, Viola & Ohri 2011b).

Right coronary artery The right coronary artery (RCA) begins at the right coronary sinus and courses anteriorly and laterally (see Figure 4.3). In 60% of individuals it gives a branch near its origin which ascends to the sinoatrial node. It descends along the right atrioventricular groove giving off an acute (or right) marginal branch which runs anteriorly along the antero-inferior margin of the right ventricle, supplying the right ventricle and apex. The RCA then courses posteriorly giving off the Atrio-Ventricular Nodal branch in 85–90% of patients at the crux of the heart (junction where septa and walls of the four chambers meet). The RCA continues as the posterior left ventricular artery (supplying the posterior left ventricular wall) (Ellis 2006, Moorjani, Viola & Ohri 2011b; Sinnatamby 2011; Drake, Vogl & Mitchell 2015).

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RCA Proximal RCA

Mid RCA Distal RCA CRUX Posterior left ventricular branch

Posterior descending artery

Figure 4.3: This image illustrates the right coronary artery with its branches.

Posterior descending artery In 85–90% of individuals the posterior descending artery (PDA) arises from the RCA on the inferior surface of the heart as it crosses the crux. In 10–15% of individuals the circumflex system is more developed and the PDA arises at the same point as it is crossed by the circumflex artery. In approximately 5% of cases both the RCA and the circumflex are well developed and both give a supply to the PDA. The PDA runs along the posterior interventricular groove towards the apex of the heart and gives off septal perforators deep into the interventricular septum, which supply its posterior third. It also provides the only blood supply to the posteromedial papillary muscle of the mitral valve (Moorjani, Viola & Ohri 2011b).

Dominance Dominance of the coronary arteries is determined by which artery gives rise to the posterior descending artery. Around 80–85% of individuals are right dominant, 10–15% left dominant and 5% co-dominant. Left dominance is slightly more frequent in men and is associated with bicuspid aortic valves (Moorjani, Viola & Ohri 2011a, 2011b).

Collateralisation In some areas, it is possible that small branches from one cardiac artery can anastomose from the branches of another. This allows for collateral flow of blood to supply the dependent myocardium of a vessel if it is blocked proximally. These anastomoses may be congenital or may be formed by angiogenesis in the presence of chronic myocardial ischaemia (Moorjani, Viola & Ohri 2011b; Meier et al. 2013).

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Venous drainage The venous drainage of the heart is through cardiac veins that mainly accompany the arteries. These veins drain into the right atrium via the coronary sinus: a large valveless vein that runs in the posterior atrioventricular groove. The great cardiac vein accompanies the LAD, then the circumflex artery and drains end to end into the coronary sinus in the atrioventricular groove. The transition point is marked by the valve of Vieussens. The middle cardiac vein accompanies the PDA and drains into the coronary sinus near its opening into the right atrium. The small cardiac vein runs around the right border of the heart in the right atrioventricular groove with the RCA and acute marginal artery. It drains into the coronary sinus near its opening. The posterior vein of the left ventricle and oblique vein of the left atrium drain into the coronary sinus towards its transition to the great cardiac vein. The posterior vein of the left ventricle drains the posterior wall of the left ventricle, and the oblique vein of the left atrium descends across the posterior wall of the left atrium. The anterior cardiac veins drain the anterior surface of the right ventricle and drain directly into the right atrium. Thebesian veins (also known as the smallest cardiac veins or venae cordis minimae) drain directly into the chambers of the heart. They are most frequently found in the walls of the right atrium and the right ventricle, then the left atrium and, rarely, the left ventricle (Ellis 2006; Moorjani, Viola & Ohri 2011b; Sinnatamby 2011).

Conducting system of the heart The cardiac cycle is co-ordinated by the conducting system of the heart. This consists of a group of specialised cardiomyocytes, namely the sinoatrial and atrioventricular nodes, which could generate spontaneous action potentials. These cardiomyocytes and the conducting fibres allow coordinated contraction between the atria and ventricles. All cardiac muscle transmits a current from cell to cell while contracting. To coordinate this contraction, the atria are insulated from the ventricles by the cardiac skeleton; and current is directed around the ventricles, down fastresponse conducting fibres so that they contract in a manner that ejects blood from the apex, then out through the outflow tracts.

Sinoatrial node The sinoatrial (SA) node is the primary pacemaker of the heart. This node is located deep to the epicardium, anterolaterally at the junction of the superior vena cava and the roof of the right atrium, near the superior end of the sulcus terminalis. The SA node generates a signal which spreads around the right atrium, via the anterior, middle and posterior intermodal tracts, and arrives at the atrioventricular node. The cells spontaneously depolarise at approximately 100 beats per minute and the rate is regulated by the autonomic nervous system. The signal also travels from the right to the left atrium, via Bachmann’s bundle, causing both atria to contract almost simultaneously. The conduction pathways within the atria are not made from specialised conduction tissue, like the Purkinje fibres found in the ventricular walls, but from cardiac muscle bundles.

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Atrioventricular node The atrioventricular (AV) node is the secondary pacemaker and discharges electrical impulses (without any stimulation) at a rate of 40–60 beats per minute. It is in the posterior-inferior region of the interatrial septum. The AV node conducts the signal from the SA node to the ventricles via the AV bundle (bundle of His), which acts as a bridge between the atrial and the ventricular myocardium. The AV node is ‘slow response’, meaning that it takes longer to transmit the signal than other cardiac tissue. This delay allows the atria to fully contract and eject blood into the ventricles before the ventricles begin to contract. The bundle of His conducts the signal through the insulating fibrous skeleton of the heart, along the membranous part of the interventricular septum, dividing into the right and left bundle branches at the junction of the membranous and muscular septum. These branches proceed downwards along the septum, towards the apex, and branch into the walls of the right and left ventricle as Purkinje fibres (sub-endocardial branches).
 The right bundle branch deploys many fibres into the sub-endocardial layer of the right ventricle at the base of the medial papillary muscle of the tricuspid valve. They run within the moderator band (septomarginal trabeculation) and direct current to the anterior papillary muscle and the rest of the right ventricular wall via Purkinje fibres. The left bundle branch splits first into the anterior and posterior fascicles before these go on to direct current towards the papillary muscles and walls of the left ventricle via Purkinje fibres.

Location of the atrioventricular node within the Triangle of Koch The location of the AV node can be triangulated by identifying landmarks within the right atrium. These three landmarks form the edges of an imaginary triangle known as the triangle of Koch, at the apex of which lies the AV node. The three boundaries are formed by: 1. The base of the septal leaflet of the tricuspid valve 2. The coronary sinus
 3. The tendon of Todaro – a ridge of tissue formed at the common insertion of the Eustachian and Thebesian valves. The AV node is found where the tendon of Todaro meets the septal leaflet of the tricuspid valve. The bundle of His can be located at the membranous septum, just superior to the triangle of Koch, where it penetrates the muscular septum (Moorjani, Viola & Ohri 2011b; Anderson & Cook 2014).

Fibrous skeleton of the heart The fibrous skeleton of the heart consists of four rings, each encircling a valve.
It acts as an electrical insulator to both the atria and ventricles, permitting impulses through specialised conduction tissue only. It also provides attachments for valve leaflets and cusps. The orientation of the valves within the heart is such that, although they are in different chambers, their circumferences almost touch.

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At the coming together of the aortic, mitral and tricuspid valves there is a dense area of collagenous insulating connective tissue called the ‘central fibrous body of the heart’. Through this runs the only normal conducting pathway between the atria and ventricles. The area that forms the angle between the mitral and aortic valves is the right fibrous trigone; and opposite this, where the mitral and aortic valve annuluses come apart again, is the left fibrous trigone (Anderson & Cook 2014; Drake, Vogl & Mitchell 2015).

Heart valves At the inlet and outlet of each ventricle there is a valve. The inlet valves lie between the atria and ventricles and are called atrioventricular valves. The outflow valves lie between the ventricles and the great arteries and are called arterial valves. Each valve has its own name, related to its appearance or location, but in the congenitally malformed or corrected heart, these names can be misleading or redundant (Anderson & Cook 2014). The valves at the inlet must be large enough to transmit blood from the atria quickly, at the relatively low atrial systolic pressure, but robust enough to prevent high pressure blood regurgitating into the atria during ventricular systole. The valves must also be able to open and close quickly and remain competent, despite their annulus distorting as the muscle of the ventricular wall contracts. The valves at the ventricular outflow must allow smooth blood flow and not exert the shearing forces on blood cells seen in turbulent flow. The valves must then close quickly and withstand the pressure produced by elastic recoil of the great vessels. The differing morphologies of these valves reflect the different demands placed upon them (Moorjani, Viola & Ohri 2011b; Anderson & Cook 2014; Drake, Vogl & Mitchell 2015).

Tricuspid valve The right atrioventricular valve typically has three leaflets or ‘cusps’. This distinguishes it from the left atrioventricular valve, which has only two cusps. It is therefore given the common name – the tricuspid valve. The three cusps are the anterior, posterior and septal leaflets. The attachment of each leaflet determines the name it is given (with the anterior leaflet attaching to the anterior free wall etc.). Where the leaflets attach to the wall, the tissue is the more fibrous, insulating tissue of the cardiac skeleton. The points at which each leaflet meet on the annulus are called commissures. The free margins of the leaflets are serrated and held curved inward towards the apex of the ventricle by the chordae tendineae and their attachments to the papillary muscles. This curve means that the line of apposition between leaflets is not at the free margin, but on the atrial surface of each leaflet that they coapt. When the papillary muscles contract, the chordae tether the leaflets and prevent them from everting and leaking during ventricular systole. When approaching surgical repair of the tricuspid valve, it is important to consider the surrounding structures. At the commissure between the anterior and septal leaflet, and halfway around the septal annulus, lies the atrioventricular node and bundle of His. From midway round the septal annulus to midway round the posterior annulus runs the coronary sinus, and from the commissure between the septal and posterior leaflets to midway round the anterior leaflet annulus,

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the right coronary artery runs in close proximity. The remainder of the anterior leaflet annulus is near the non-coronary cusp of the aortic valve. If the right ventricle dilates, as in right-sided heart failure, the tricuspid annulus can dilate. As the leaflets remain the same size, the coaptation areas move towards the free margin of the leaflet and, if it dilates too far, the valve leaks (Sinnatamby 2011; Anderson & Cook 2014; Harington, Mora & Wu 2014; Drake, Vogl & Mitchell 2015).

Pulmonary valve The right arterial valve, in the normal arrangement, lies at the origin of the pulmonary trunk (main pulmonary artery). For this reason, it is called the pulmonary valve, and, in congenital malformation such as transposition of the great vessels (where the aorta arises from the right ventricle and the pulmonary trunk from the left), the name ‘pulmonary valve’ is retained by the valve at the origin of the pulmonary trunk. The valve is a semilunar valve; it is composed of three cusps that each occupy approximately one-third of the cross-sectional area of the pulmonary trunk. The attachment of each cusp to the arterial wall is curved so that each end of the cusp is more distal in the artery and the middle of the valve forms a nadir. This curved attachment of each leaflet makes the valve annulus a crown-like structure, rising up towards the commissures and dipping down towards the basal attachment of each cusp. At the level of the commissures a ridge is visible on the inner surface of the artery; the sinotubular junction. The areas of the artery wall demarcated by the attachment of the leaflets and the sinotubular junction bulge outwards ever so slightly to form three pouches; the pulmonary sinuses. Viewed anteriorly, there is a left, right and anterior sinus. When the valve is closed there are three zones of apposition with a central point where all three leaflets meet; thus, from above or below, the closed valve looks like a Mercedes Benz sign. The free edges of the cusps are slightly thickened, forming the ‘lenules’, and the central portion where all three cusps meet is thickened further, forming the nodule of the semilunar cusp or ‘nodule of Arantius’. The zones of apposition, when the valve is closed, fall on the plane of the sinotubular junction so that each cusp, along with its associated sinus, forms a little cup. It is the pressure of the blood filling this cup, rising above that of the ventricle, that forces the valve closed in ventricular diastole. The opening and closing of the semilunar valves is entirely passive (Moorjani, Viola & Ohri 2011b; Sinnatamby 2011; Anderson & Cook 2014; Harington, Mora & Wu 2014; Drake, Vogl & Mitchell 2015).

Mitral valve The left atrioventricular valve has two leaflets: the anterior (or aortic) leaflet and the posterior (or mural) leaflet. The annulus of the valve is kidney-shaped, with the anterior leaflet occupying the inner curve (approximately one-third of the annular circumference) and the posterior leaflet, the outer curve (approximately two-thirds of the annular circumference). The two leaflets have approximately the same surface area, as the anterior leaflet is longer and crosses about two-thirds of the orifice diameter before meeting the posterior leaflet. This gives the coaptation area a curved appearance from which the ‘mitral valve’ derives its name, as it is said to resemble a bishop’s mitre.

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It functions in a similar manner to the tricuspid valve, with the leaflets curving towards the apex at their edges to coapt on their atrial surface, and prolapse being prevented by the chordae and papillary muscles. When looking at the valve from the left atrium (as the surgeon would), the curve of the coaptation area is like a smile, turned up at the anterolateral commissure on the left, heading down towards its nadir in the middle of the valve, before turning up again towards the posteromedial commissure on the right. The posterior leaflet, rather than appearing as a single sheet, is usually divided into three ‘scallops’. These scallops are like miniature leaflets within the leaflet and are useful functional segments to consider when approaching surgical repair. From the anterolateral to the posteromedial commissure, they are labelled P1, P2 and P3. The anterior leaflet is a single sheet, but the corresponding coapting regions are named A1, A2 and A3. The annulus is again composed of fibrous insulating tissue but has a different variety of structures to be aware of when surgery is contemplated. The orientation of the valve is such that the anterior leaflet has its annular base just beneath the left and non-coronary cusps of the aortic valve. From the anterolateral commissure round to the nadir of the posterior annulus runs the circumflex coronary artery, and from the nadir to the posteromedial commissure runs the coronary sinus. At the posteromedial commissure is the right fibrous trigone, where the atrioventricular node and conducting bundles run in close proximity. When the left ventricle becomes dilated (as with myocardial infarction), the papillary muscles pull away from the mitral valve towards the apex. This can prevent the valve from closing, allowing regurgitation of blood into the left atrium during ventricular systole. If the papillary muscles themselves become infarcted, they can rupture, leaving a flail segment prolapsing into the left atrium. A similar, though less dramatic, situation can arise with snapped chordae (Moorjani, Viola & Ohri 2011b; Sinnatamby 2011; Anderson & Cook 2014; Harington, Mora & Wu 2014; Timek and Fann 2014).

Aortic valve The left arterial valve, in the normal arrangement, lies within the origin of the aorta. It is similar in structure to the pulmonary valve, with a similar mechanism of operation and similar surrounding structures and crown-shaped annulus. As with the pulmonary valve, it is named for the vessel in which it lies – the aorta. The three sinuses of the aortic valve are the left coronary sinus, the right coronary sinus and the non-coronary sinus. They are named for the coronary artery that arises from them (with, typically, no vessel arising from the non-coronary sinus). When viewed from an anterior perspective, the left coronary sinus lies posteriorly, the right coronary sinus lies anteriorly to the right, and the non-coronary sinus lies anteriorly to the left (Moorjani, Viola & Ohri 2011a, 2011b; Anderson & Cook 2014; Harington, Mora & Wu 2014; Drake, Vogl & Mitchell 2015).

The great vessels The two arteries arising from the ventricles and bounded by arterial valves are called ‘the great arteries’ and the veins that drain into the heart are called ‘the great veins’. They have typical paths and relationships to surrounding structures that are important to know about when operating.

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Superior vena cava The superior vena cava (SVC) drains into the superior aspect of the right atrium. It is the rightmost of the vascular structures connected superiorly to the heart (leftmost when viewed from the front). Descending vertically into the heart, it is formed by the confluence of the right and left brachiocephalic (or innominate) veins, at the level of the first costal cartilage, and it enters the pericardium just before it connects to the heart. The left innominate vein crosses from the left anterior to the other superior great vessels and their branches. It is at risk of injury when identifying the superior extent of the pericardium to expose the aorta. It receives a tributary in the form of the azygous vein on its right lateral border immediately before entering the pericardium. Within the pericardium, it is covered anteriorly by serous pericardium but posteriorly it is bare and helps form the border of the pericardial sinuses (Ellis 2006; Moorjani, Viola & Ohri 2011b; Drake, Vogl & Mitchell 2015).

Inferior vena cava The inferior vena cava (IVC) enters the pericardium immediately after penetrating the diaphragm at the level of T8. It has a very short intra-pericardial length, where it is covered anteriorly by serous pericardium, before joining the right atrium (Drake, Vogl & Mitchell 2015).

Pulmonary veins The right and left paired superior and inferior pulmonary veins enter the posterior lateral walls of the fibrous pericardium before entering the left atrium. They are covered anteriorly by serous pericardium but posteriorly they are continuous with the parietal pericardium and, along with the SVC, IVC and the fold of serous pericardium connecting them, help form the borders of the oblique and transverse sinuses ( Moorjani, Viola & Ohri 2011b; Drake, Vogl & Mitchell 2015).

Aorta The aorta arises from the left ventricle, between the SVC and pulmonary trunk. It travels vertically for a few centimetres before exiting the pericardium and arching backwards and to the left, at the level of T4, to travel inferiorly within the left hemithorax. Within the pericardium it is covered, together with the pulmonary trunk, in a sheath of serous pericardium. On the arch, it typically gives off three branches: first the brachiocephalic trunk (innominate artery); then the left common carotid; then the left subclavian arteries. The brachiocephalic trunk splits into the right subclavian and common carotid arteries (Ellis 2006; Moorjani, Viola & Ohri 2011b; Drake, Vogl & Mitchell 2015).

Pulmonary trunk The pulmonary trunk arises from the right ventricle to the left of the aorta. To do so, the right ventricular outflow tract passes anterior to the left ventricular outflow tract. The pulmonary trunk is therefore pointing slightly posteriorly as it arises and travels backwards, before splitting into the left and right pulmonary arteries, beneath the arch of the aorta, that come off in the horizontal plane at almost 180 degrees from each other. They exit the pericardium superior to the pulmonary veins (Moorjani, Viola & Ohri 2011b; Sinnatamby 2011).

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Conduits used for coronary bypass grafting surgery Internal mammary artery Also known as the internal thoracic artery, the internal mammary artery (IMA) arises from the subclavian artery. Many patients have their left internal mammary artery harvested as a conduit. However, in young patients, where total arterial revascularisation is planned, both right and left internal mammary arteries may be used. In older patient with diabetes with an osteoporotic sternum, bilateral internal mammary artery harvesting may increase the risk of sternal wound infections or dehiscence. This artery passes inferiorly and lateral to the sternum, dividing into the superior epigastric and musculophrenic arteries. The artery supplies the anterior intercostal arteries to intercostal spaces one to six. It can be a source of major haemorrhage in chest trauma if it is punctured by a fractured rib.

Radial artery The radial artery courses inferolaterally and is covered by the brachioradialis muscle. The artery is visible when this muscle is pulled laterally. In the distal forearm the artery lies on the anterior surface of the radius where it is covered by skin and fascia only. The strong pulsations can be felt just lateral to the tendon of flexor carpi radialis. An Allen’s test needs to be carried out on every patient prior to harvesting the radial artery. This is essential to confirm if the patient has an intact palmar arch blood flow between the ulnar and radial artery which will prevent ischaemia in the limb (Moorjani, Viola & Ohri 2011b).

Greater saphenous vein The greater saphenous vein is a superficial vein that courses anterior to the medial malleolus, ascending on the medial aspect of the lower limb. It can be found a hand’s breadth posterior to the patella and empties into the deep femoral vein. The superficial circumflex iliac, superficial epigastric and external pudendal veins also drain into the greater saphenous vein near its termination in the groin. Note: This vein is readily accessible for coronary artery bypass grafting. It is reversed when removed so that the valves inside the vein do not obstruct coronary blood flow. The saphenous nerve also accompanies the vein, and injury to this nerve may cause pain or numbness and a tingling sensation along the medial border of the foot.

Short saphenous vein The short saphenous vein is harvested when there is little choice of conduits for bypass and it is more technically challenging to harvest. It may be necessary to use this conduit when a patient has no suitable radial arteries or if they have varicosities in the greater saphenous vein distribution. The short saphenous vein arises laterally on the foot and ascends posterior to the lateral malleolus, emptying into the popliteal vein in the popliteal fossa (Moorjani, Viola & Ohri 2011b).

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Thoracic anatomy Introduction The thorax describes the uppermost portion of the body’s trunk, which encloses the thoracic cavity (see Figure 4.4). It is bounded superiorly by an open bony ring formed by the superior borders of the 1st ribs and manubrium, known as the ‘thoracic inlet’ or ‘superior thoracic aperture’. Inferiorly, the inferior borders of the 11th and 12th ribs, along with the combined costal cartilages of 7th to 10th ribs and xiphisternum, make up a larger ring, closed off by the diaphragm, known as the ‘inferior thoracic aperture’ (Ellis 2006; Drake, Vogl & Mitchell 2015; Moorjani, Viola & Walker 2016).

Clavicle Sternum Ribs

Cartilages

Figure 4.4: The thoracic cage, viewed from the front. The vertebral column has been removed and the right and left clavicles added The diaphragm is a sharply concave sheet of muscle that plateaus at right and left domes (with the right slightly higher than the left) within the thoracic cage, reducing the apparent volume of the thoracic cavity. The wall of the thorax is made up of the thoracic cage and intercostal muscles. These are overlain by, and provide attachments for, skeletal muscles involved in the movement of the head, neck and upper limbs, as well as skin, the breasts and subcutaneous tissue (Sinnatamby 2011). Within the thoracic cavity lie the heart, the great vessels, the lungs, major airways, the oesophagus and the thoracic duct. These organs are contained within one of three subcompartments: the paired left and right pleural cavities (lined by parietal pleura) and the central mediastinum. Many organs of the abdomen (such as the liver, stomach and kidneys) are also encased by the thoracic cage but lie beneath the domes of the diaphragm, and so, within the abdominal cavity (Sinnatamby 2011; Drake, Vogl & Mitchell 2015).

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It is vital to understand the anatomy of the thorax for everyday thoracic procedures. A structured anatomical approach will enable safe systematic surgery. In cancer resection, tumours can distort the appearances of normal tissues and make the identification of vital structures challenging. Following major trauma, a patient may be bleeding internally from a large vessel in the thorax. With this in mind, it is important to know where to start your incision for optimal access. An emergency anterolateral thoracotomy can often provide the best exposure in such instances. When operating on patients with large pneumothoraces or pleural effusion requiring drainage, knowledge of the surface landmarks for safe chest drain insertion is crucial (Koenig Jr & Efron 2014; Moorjani, Viola & Walker 2016).

Surface anatomy There are many palpable and visible landmarks on the thorax that can be used to identify the position of underlying structures in the healthy individual, though certain disease processes may alter the relationship between them. Identification of these landmarks can aid a clinician in diagnosis and performing clinical and surgical procedures. The ‘Angle of Louis’, also known as the sternal angle, refers to the manubriosternal junction, and is readily palpable on the anterior chest wall. The inferior border of the T4 vertebrae is located at this level and the imaginary horizontal plane passing through these two points is known as the ‘Thoracic Plane’ (Moorjani, Viola & Walker 2016). It marks the inferior border of the superior mediastinum and the division between the arch of the aorta and the ascending and descending portions. This is also the level of the Carina: the bifurcation of the trachea into left and right main bronchi. Importantly, the manubriosternal junction articulates with the second costal cartilage and is a useful landmark for counting ribs. The nipple should lie over the 4th intercostal space in males (the position is more variable in females) (Ellis 2006; Moorjani, Viola & Walker 2016). Other palpable structures are: ●●

The C7 vertebrae, which is the first palpable spinous process

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The suprasternal notch, which corresponds to the level of the T2/T3 vertebrae

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The spine of the scapula, which corresponds to the level of the T3 vertebrae

The inferior angle of the scapula, which approximates with the level of T8. It overlies the 7th rib in the neutral position and the 6th rib in full protraction. It is an important anatomical landmark for thoracotomy incision.

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The body of the sternum, which lies between T5 and T8 and terminates in the xiphisternum.

All the ribs excluding the 1st, which are covered by the clavicles and neck muscles, are palpable at some point. By palpating the above landmarks, it is possible to count the ribs and identify the borders of underlying structures.

Boundaries of the pleura The parietal pleura composing the boundaries of the pleural cavities is named for the structures related to its outer surface (see Figure 4.5). The costal part is that associated with the thoracic

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cage; the mediastinal part is that associated with the mediastinum; and the diaphragmatic part overlies the diaphragm. At the thoracic inlet, the left and right pleurae form two convex domes, known as the left and right pleural cupola. The pleural cavities bilaterally have their apex 2–3cm above the clavicle and lie outside the thorax. Both pleurae then extend inferiorly and outwards, becoming intimately related to the inner surface of the ribs and intercostal muscles (costal pleura). The medial (mediastinal) surfaces of the two pleurae are concave and envelop the mediastinum between them, but the margins between the costal and mediastinal parts of the pleura meet anteriorly from the height of the 2nd to the 4th costal cartilages. At this point the right pleura continues vertically down but the left pleural margin deviates laterally and continues its descent lateral to the left border of the sternum. At the level of the 6th costal cartilage, the two pleural margins diverge and spiral around the chest wall so that they cross the 8th rib in the mid-clavicular line, the 10th rib in the midaxillary line and the 12th rib at the lateral border of the erector spinae muscles. Posteriorly, the margin extends vertically from T1 to the inferior border of T12, just lateral to the vertebral bodies. Due to the concavity of the diaphragm, the diaphragmatic part of the pleura is also concave and moves with respiration. At full expiration, with the diaphragm at maximum elevation, the right diaphragmatic part can lie as high as the 4th intercostal space and the left at the 5th (Ellis 2006, Sinnatamby 2011).

Clavicle

Ribs

Left pleural margin

Right pleural margin

Figure 4.5: The boundaries of the left and right pleurae. The superior extension of the diaphragm has been marked on in full inspiration; the posterior aspect of the pleura is darker and the diaphragm rising above the inferior border is demonstrated.

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Boundaries of the heart The position of the heart within the chest is roughly described by the irregular rectangle with its vertices at the 2nd left costal cartilage, the 5th left intercostal space in the mid-clavicular line, the 6th right costal cartilage and the 3rd right costal cartilage (see Figure 4.6).

Clinical importance ●●

Landmarks for safe insertion of a chest drain or aspiration of pleural collections

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Landmarks for a thoracotomy

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Indicator of possible visceral injuries with penetrating trauma.

(Koenig Jr & Efron 2014; Moorjani, Viola & Walker 2016)

Boundaries of the heart

Left pleural margin

Right pleural margin

Figure 4.6: The boundaries of the heart. The way the pleurae overlap and wrap around the heart anteriorly is demonstrated

Thoracic cage The thoracic cage is the skeletal frame of the thorax. It is formed by the thoracic vertebrae, ribs and sternum.

Thoracic vertebrae There are 12 thoracic vertebrae, characterised by their association with the ribs. They are numbered from 1 to 12 superiorly to inferiorly. Thoracic vertebrae 1 to 9 (T1 to T9) have two paired superior and inferior demifacets on the lateral surfaces of their bodies which each articulate with a rib. The left and right superior demifacets of T1 are in fact complete facets that articulate with the heads of the left and right 1st ribs.

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From here down to T10, the associated ribs of each vertebra articulate with its superior demifacets and the inferior demifacets of the vertebra above. T10 has no inferior demifacets, as ribs 11 and 12 articulate only with their associated vertebrae which have a single complete facet on each side. T1 to T10 articulate a second time with their associated ribs by means of a transverse facet on their transverse processes. Each vertebra articulates with the one above and below by means of intervertebral discs and overlapping superior and inferior articular processes (Drake, Vogl & Mitchell 2015; Moorjani, Viola & Walker 2016).

Thoracic ribs There are 12 pairs of ribs, numbered 1 to 12, superior to inferior. At the posterior end, each rib has a head, for articulating with associated vertebrae, a neck, and a tubercle, for articulating with a transverse process. As ribs 11 and 12 do not articulate with transverse processes, they lack both tubercles and necks. The main body of the rib, or shaft, is a curved flattened structure, thicker superiorly than inferiorly, giving a comma shape in cross-section. The inner curvature of this comma is known as the ‘subcostal groove’. Anteriorly, every rib has a costal cartilage which it joins to via a primary cartilaginous ‘costochondral’ joint. The first (superior) seven costal cartilages then attach anteriorly to the sternum – the first with a primary cartilaginous joint and the next six via synovial ‘sternocostal’ joints. They are known as ‘true ribs’. The remaining ribs are known as ‘false ribs’. The costal cartilages of ribs 8 to 10 form synovial ‘interchondral’ joints with the costal cartilage of the rib above. The costal cartilages of ribs 11 and 12 are free anteriorly (floating ribs) and do not articulate with the sternum (Sinnatamby 2011).

The sternum The sternum lies centrally on the anterior wall of the thorax. It is composed of three parts: the manubrium, the body (gladiolus) and the xiphoid process. The manubrium is the most superior part of the sternum. It articulates with the clavicles, the 1st and 2nd costal cartilages and the body of the sternum. The superior border of the manubrium has a palpable notch, accentuated by the medial end of the clavicle, which articulates with it laterally on the superior surface. This notch, known as the ‘supra-sternal’ or ‘jugular’ notch, is an important landmark in surface anatomy as it is easily palpable. Another important landmark, the ‘Angle of Louis’, is formed by the manubriosternal joint between the inferior border of manubrium and the body of the sternum. The first costal cartilages attach superiorly on the lateral borders of the manubrium, and the second costal cartilages articulate with both the manubrium and body of the sternum at either end of the manubriosternal joint. The body of the sternum is a long flat plate of bone which has the manubriosternal joint at its superior border, the xiphisternal joint at its inferior tip and joints for the 2nd to 7th costal cartilages along either side. Like the joint of 2nd costal cartilage, the 7th articulates partly with the body of the sternum and partly with the adjoining bone. In this case, the xiphoid process. The xiphoid, or ‘xiphisternum’, is a small bone that can remain cartilaginous well into adulthood. It has a variable

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shape which may be pointed or bifid. It articulates above with the body of the sternum and with the lower portions of the 7th costal cartilages. It provides an attachment for muscles of the anterior abdominal wall (Ellis 2006; Sinnatamby 2011; Moorjani, Viola & Walker 2016).

Thoracic muscles Intercostal muscles True muscles of the thoracic wall, the intercostal muscles are 11 paired bands of muscle that lie between each set of ribs. They are divided into the external, internal and innermost intercostals. The external intercostal muscles attach to the inferior border of the rib above and travel anteroinferiorly to the superior border of the rib below. Deep to this, the internal intercostal muscles attach to the costal groove and travel along the interior surface of the rib postero-inferiorly to the superior border of the rib below. Deeper still, and superficial to the parietal pleura, the innermost intercostal muscles form a thin layer that attaches to the inner surfaces of the ribs and runs in the same orientation as the internal intercostals (see Figure 4.7).

Cross section of rib Intercostal artery

Intercostal muscles

Intercostal vein

Figure 4.7: The intercostal muscles and bundle: a section across the ribs and intercostal muscles showing the position of the intercostal bundle (nerve, artery and vein) between the layers

Intercostal nerve

Clinical note The neurovascular bundles containing the intercostal vein, artery and nerve lie on the internal inferior surface of the rib in the subcostal groove. They lie in the muscle layer between the internal and innermost intercostal muscles. These vessels can cause significant haemorrhage if injured. Any intervention requiring entry into the thoracic cavity should therefore be approached above and never below a rib (Ellis 2006; Drake, Vogl & Mitchell 2015).

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Upper limb muscles overlying the thorax Several of the muscles involved in movement of the spine, upper limb and neck overlie the thoracic cage. Although they are anatomically and functionally not a part of the thorax, some of these muscles give rise to some important landmarks when performing thoracic procedures.

Latissimus dorsi The latissimus dorsi muscle is a muscle of the upper limb that partly originates on the thoracic wall and overlies the thorax. It originates from the spinous processes of T6–L5, the lumbar fascia and posterior iliac crest, and inserts onto the bicipital groove of the humerus. It is innervated by the thoracodorsal nerve and receives its blood supply from the thoracodorsal artery. Its function is to adduct, medially rotate and extend the arm at the shoulder. The inferolateral border of this muscle, along with a small portion of terres major laterally, creates the posterior axillary fold. This landmark provides the most posterior border of the ‘triangle of safety’: the region in which it is safest to insert a chest drain. The latissimus dorsi muscle is the boundary used to differentiate between a posterolateral and anterolateral thoracotomy. If the latissimus dorsi is cut, the incision is posterolateral. If it is preserved, it is anterolateral.

Serratus anterior Another muscle of the upper limb, serratus anterior, originates from the external and superior surfaces of ribs 1–8 and inserts onto the medial border of the scapula (costal margin). It protracts and rotates the scapula, while keeping it from pulling away from the thoracic wall. It is innervated by the long thoracic nerve and receives its blood supply from the lateral thoracic and thoracodorsal arteries. When performing a posterolateral thoracotomy, the serratus anterior muscle overlies the 5th rib space and can be retracted to preserve it. When closing the thoracotomy, it will then help partially cover and support the site where the thorax is entered.

Pectoralis major Pectoralis major is also a muscle of the upper limb. It originates from the sternum, 1st to 6th costal cartilages and the clavicle and inserts onto the bicipital groove of the humerus. It adducts, medially rotates and flexes the humerus at the shoulder. It is innervated by the medial and lateral pectoral nerves and receives its blood supply from the pectoral branch of the thoracoacromial artery. The inferolateral border of this muscle creates the anterior axillary fold: the most anterior border of the ‘triangle of safety’ (Sinnatamby 2011; Drake, Vogl & Mitchell 2015; Moorjani, Viola & Walker 2016).

Tracheal anatomy The trachea begins at the inferior border of the cricoid cartilage (C6) and bifurcates at the angle of Louis (T4/5) into the right and left main bronchi. It is a tubular structure, approximately 2.5cm wide and 11.5cm long. The trachea is composed of a fibro-muscular tube held open by a series of U-shaped cartilages which are deficient posteriorly. The posterior wall is completed by fibrous tissue and the trachealis muscle. It can stretch and deform during respiration, then recoil to

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its original position, due to elastic fibres within its wall. It is lined by pseudo-stratified nonkeratinised epithelium containing goblet cells. When the trachea divides into the left and right main bronchi, the cartilaginous rings continue down each bronchus. The ridge at this bifurcation is also supported by a cartilaginous skeleton and is called the carina. The right main bronchus is wider and slightly more vertical than the left, which means that inhaled foreign bodies are more likely to follow this route (Ellis 2006; Drevet, Conti & Deslauriers 2016).

Bronchial tree The left and right main bronchi divide further into lobar and then segmental bronchi, then a series of smaller sub-segmental bronchi and finally bronchioles. Bronchioles differ from bronchi, as they do not contain cartilaginous rings within their walls. Finally, the airway ends in terminal bronchioles, which give rise to alveolar ducts and the alveoli. From the trachea to the terminal bronchioles, there are 23 progressively smaller iterations. These can be divided into conducting zones (generation 1–16), and respiratory zones (generations 17–23) where gas transfer can occur. The divisions within the airway are usually predictable and correspond to a similar vascular supply. This allows surgeons to perform anatomical lung resections, removing one or more specific bronchopulmonary segments while preserving the remaining lung parenchyma. The right main bronchus is approximately 2.5cm long. At its distal end, it has a secondary carina where it bifurcates into the right upper lobe bronchus and the bronchus intermedius. This happens within the lung root before the hilum. The right upper lobe bronchus trifurcates into the segmental bronchi once it is within the lung parenchyma. The bronchus intermedius continues for a further 2cm before dividing again into the middle lobe bronchus and the bronchus to the right lower lobe at the hilum. The right lower lobe bronchus branches immediately to give off the bronchus to the apical segment of the right lower lobe at the same level or just distal to the middle lobe bronchus. It then continues and quadrifurcates into the basal segmental bronchi. The middle lobe bronchus bifurcates into the segmental bronchi of the middle lobe. The left main bronchus is approximately 5cm in length and terminates in a secondary carina between the left upper and lower lobe bronchi at the hilum of the left lung. The short left upper lobe bronchus bifurcates into a lingular bronchus and the bronchus to the left upper lobe proper. These then divide into their individual segmental bronchi. The left lower lobe bronchus, like the right, gives off a bronchus to the apical segment of the left lower lobe then splits into the basal segmental bronchi (Ellis 2006; Sinnatamby 2011; Drevet, Conti & Deslauriers 2016; Moorjani, Viola & Walker 2016).

The lungs The lungs lie in the cavities on the left and right of the thorax. They are divided into lobes that radiate out from the hilum on the medial surface of the lung. The lobes are separated by planes that penetrate the lung, to a greater or lesser degree, towards the hilum. The right lung has three lobes: upper, middle and lower. The left lung is slightly smaller, due to the space in the left hemithorax taken up by the heart. It is divided into two lobes: the upper lobe and the lower lobe.

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Each lobe of the lung can be further divided into functional units called segments. A segment is the smallest unit of lung parenchyma supplied by a single named bronchus and pulmonary artery. They are considered as the basic units of a functioning lung. While the demarcation between lobes is clear, segments are not visibly separated. The right lung has 10 segments: three in the upper lobe; two in the middle lobe; and five in the lower lobe. There is some discrepancy in the description of the segments of the left lung with sources stating between eight and ten segments in total. This is because in the left upper lobe the apical and posterior segments are sometimes considered fused as an ‘apicoposterior’ segment; and in the left lower lobe the anterior basal and medial basal segments may be considered fused as an ‘anteromedial’ segment. When assessing postoperative lung function after lobectomy, the number of segments resected is used to calculate lung function. For this calculation, the British Thoracic Society considers the left upper lobe to have five segments (three in the upper lobe proper and two in the lingular) and the left lower lobe to have four. This reflects the reduced volume of the left lower lobe when compared to the right, due to the space occupied by the heart. The lungs are covered by a layer of visceral pleura. The visceral pleura is fixed firmly to the lung and provides a smooth, non-adherent surface, allowing the lungs to slide against the parietal pleura during respiration. The space between the two layers of pleura is the true pleural cavity and is filled with a small volume of pleural fluid. While the lungs are fully inflated, the pleural cavity only has a small volume but in the event of a collapsed lung there is a large potential space. Between the lobes of the lungs, the pleura divides into the lung, creating the fissures that separate the lobes and allow them to move smoothly over each other. These fissures are of variable depth, a greater or lesser degree of cross-fissure ventilation is often seen. On the medial surface of each lung several structures enter the lung parenchyma. These structures are bundled together in a sheath of parietal pleura and form the root of the lung. Inferior to the root of the lung, the lung is tethered to the mediastinum by a double fold of parietal pleura extending down from the root known as the pulmonary ligament. Where the root and the pulmonary ligament meet the lung, the parietal pleura becomes the visceral pleura, continuing over the surface, while the structures inside penetrate the lung. This area is known as the lung hilum. The structures within the root are the bronchi, arteries and veins (Ellis 2006; Sinnatamby 2011; Moorjani, Viola & Walker 2016).

Borders and fissures For the most part, the lungs follow the borders of the pleura. Inferiorly, the parietal pleura extends further than the lung on the chest wall, giving rise to the anterior and posterior costodiaphragmatic recesses. The apex of the lung extends superiorly to the 1st rib at the sternal end within and closely related to the cupola of the parietal pleura. Note: There is a risk of pneumothorax here during central line insertion into the internal jugular vein. The inferior border of the lung spirals around the chest wall in a similar fashion to the pleura, approximately two ribs higher. It crosses the midclavicular line at the level of the 6th rib, and the mid-axillary line at the level of the 8th rib, and then meets the 10th rib next to the vertebral column posteriorly. Like the pleura, there is a discrepancy between left and right (with the left lung having a cardiac notch to account for

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the space taken up by the heart), and there is variation in the depth of the inferior border with respiration. The inferior surface of the lung is concave where it is indented by the diaphragm. The fissure between the upper and lower lobes on both sides is called the oblique fissure (or the diagonal or major fissure). On both sides, it runs through the plane of an imaginary line drawn around the chest from 2.5cm lateral to the spinous process of T5 to the costal cartilage of the 6th rib. It roughly follows the line of the 5th rib around the chest, but at a slightly steeper angle, and the medial border of the scapular when the arm is fully abducted above the head. Anteriorly on the right, the upper lobe gives way to the middle lobe, and the oblique fissure separates the middle and lower lobe. The middle and upper lobe are separated by the horizontal fissure (also known as the transverse or minor fissure). As the name implies, this runs horizontally at the level of the 4th intercostal cartilage until it meets the oblique fissure under the 5th rib in the mid-axillary line (Ellis 2006; Sinnatamby 2011).

The diaphragm The diaphragm is a dome-like musculotendinous aponeurosis which separates the thoracic and abdominal cavities at the thoracic outlet. It is composed of a costal part, a thin peripheral muscle that causes downward depression of the diaphragm for respiration, and the crura: two (left and right) thicker musculotendinous bands posteriorly that support the heart. These parts blend together to form the sheet-like aponeurosis. The muscle fibres of the costal part have their origins as a ring from the xyphoid process, the costal margin and the tips of the 11th and 12th ribs. At the costal margin, these fibres interdigitate with the muscle fibres of transverse abdominal muscle. The crura have long vertical origins on the bodies of the lumbar vertebrae and intervertebral discs (merging with the anterior longitudinal ligament) as they travel superiorly. The right crux attaches to L1–L3 on the right of the midline, and the left crux (L1–L2) on the left. There are gaps in diaphragmatic attachment on either side, between the 12th ribs and the lumbar vertebrae, which are bridged by the origin of the costal part to a pair of arched ligaments (two on each side) that pass over the surface of quadratus lumborum (the lateral arcuate ligament) and psoas major (the medial arcuate ligament). These ligaments are formed by a thickening of the thoracolumbar fascia. The lateral arcuate ligament attaches to the 12th rib and arches over quadratus lumborum to attach to the L1 transverse process. The medial arcuate ligament then arches from the L1 transverse process to the muscular attachment of the diaphragm on the lumbar vertebral bodies. All muscular parts of the diaphragm travel superiorly and arch inwards to converge on a tendinous sheet called the ‘central tendon’, which lies on a plane passing through the xiphisternal joint and T8 vertebra. This is continuous with the fibrous pericardium. The central tendon is slightly lower than the highest points of the diaphragm on the right and left, creating left and right domes of the diaphragm, one within each hemithorax. There are three primary openings in the diaphragm to permit the passage of structures between the thoracic and abdominal cavity (and vice versa) (Sinnatamby 2011; Predina & Singhal 2014; Drake, Vogl & Mitchell 2015).

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1. The first opening, the caval hiatus, is within the central tendon at the level of T8, to the right of the midline, and allows the passage of the inferior vena cava and right phrenic nerve. 2.

The next opening, the oesophageal hiatus, is more posterior and inferior at the level of T10, just to the left of the midline. This opening is encircled by fibres of the right crux as it curves over to the left to insert on the central tendon. Through this opening pass the oesophagus, vagal plexus (confluence of left and right vagal nerves upon the oesophagus) and branches of the left gastric artery, veins and lymphatics.

3.

The final opening, the aortic hiatus, is the most posterior and inferior. It lies in the midline between the two crura with the T12 vertebra forming its posterior boundary. Anteriorly, fibres from the left and right crura loop around and converge to form the median arcuate ligament. The aorta and thoracic duct pass through this opening (Sinnatamby 2011; Moorjani, Viola & Walker 2016).

Other structures which penetrate the diaphragm but do not have openings with defined margins are: The azygous and hemi-azygous veins, which may pass through the aortic hiatus or penetrate the crura directly on left and right

●●

●●

The left phrenic nerve, which penetrates the left dome of the diaphragm

Greater, lesser and least splanchnic nerves bilaterally, which penetrate the left and right crura directly.

●●

Clinical importance: ●●

Paralysis following phrenic nerve injury

●●

Diaphragmatic hernia (congenital, acquired and traumatic)

●●

Congenital: ●●

Bochdalek hernia (>95%) is a posterolateral defect in the diaphragm mostly left sided

●●

Morgagni hernia is a rare anterior defect of the diaphragm.

(Sinnatamby 2011; Predina & Singhal 2014).

The mediastinum The mediastinum lies centrally in the thoracic cavity and contains all organs except the lungs. It is bordered by the sternum anteriorly, the pleura laterally and the vertebral column posteriorly. It extends from the thoracic inlet to the diaphragm. There are several models which can be used to subdivide the mediastinum. There is a four-compartment model and Felson’s and Shield’s three-compartment models (Moorjani, Viola & Walker 2016). In the four-compartment model there is a superior and an inferior compartment, which are separated by the thoracic plane (the plane running between T4 and the ‘angle of Louis’). The inferior compartment is then further subdivided into the anterior, middle and posterior mediastinum.

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Four-compartment model 1. Superior mediastinum The superior mediastinum is bounded by the manubrium anteriorly and, posteriorly, the thoracic vertebrae T1–T4. Important structures within the superior mediastinum include: the trachea, oesophagus, thymus, great vessels, thoracic duct, vagus nerves, left recurrent laryngeal and phrenic nerves. 2. Inferior mediastinum ●●

Anterior – in front of the fibrous pericardium

●●

Middle – consists of the fibrous pericardium and its contents plus the carina and main bronchi

●●

Posterior – between the pericardium and thoracic vertebrae (T4–T12).

Felson’s three-compartment model Anterior – from the thoracic inlet to the diaphragm, bounded anteriorly by the sternum and costal cartilages. Posteriorly bounded by the posterior wall of the trachea superiorly, then the anterior pericardium.

●●

Middle – limited superiorly by the pericardial reflection and inferiorly by the diaphragm. It is bounded anteriorly and laterally by the fibrous pericardium and posteriorly by the posterior wall of the trachea and posterior pericardium.

●●

●●

Posterior – that which lies between the posterior wall of the trachea and the thoracic wall.

Shield’s three-compartment model Prevascular – bounded posteriorly by the anterior pericardium and great vessels and anteriorly by the sternum

●●

●●

Visceral – posteriorly bounded by the anterior surface of the vertebral bodies

Paravertebral – split into two sulci either side of the vertebral column, bounded posteriorly by the chest wall.

●●

Clinical importance: ●●

Potential sites for tumour invasion (metastases and primary tumours)

●●

Identifying source of injury in penetrating thoracic trauma.

(Moorjani, Viola & Walker 2016).

Intrathoracic structures Nerves 1. The phrenic nerves arise bilaterally from the anterior rami of C3, 4 and 5 nerve roots. There is a right and a left phrenic nerve. This is the primary motor nerve to the diaphragm and its division results in paralysis of the corresponding hemi-diaphragm. Both the right and left phrenic enter the thorax posterior to the subclavian veins and anterior to the subclavian arteries,

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where they pick up their accompanying artery. The right phrenic traverses over the capula and travels along with the brachiocephalic vein and then on the lateral surface of the superior vena cava. It then continues along the lateral border of the pericardium, just anterior to the hilum, and penetrates the diaphragm along the inferior vena cava to supply it from its inferior surface. The left phrenic descends with the left common carotid and passes over the left subclavian artery where it picks up the left phrenic artery. It travels on the pericardium, lateral to the ascending aorta and anterior to the left hilum. It pierces the diaphragm directly to the left of the pericardium to innervate it from below (Sinnatamby 2011; Moorjani, Viola & Walker 2016). Clinical note: It is most at risk of injury during pericardiectomy and during harvesting of the internal mammary artery. 2. The thoracic sympathetic trunk crosses the neck of the first rib, the heads of ribs 2–10 and the vertebral bodies of T1–T12 bilaterally. These autonomic neural pathways can be interrupted surgically for treatment of excessive upper limb hyperhidrosis and facial flushing. Clinical note: Care should be taken not to divide the sympathetic chain above the level of the 2nd rib as injury here can lead to Horner’s syndrome (Ellis 2006). 3. The vagus nerves are the tenth cranial nerves. They give off the recurrent laryngeal nerves, which supply all the intrinsic muscles of the larynx except cricothyroid. The right vagus enters the thorax medial to the phrenic, between the right subclavian and right common carotid arteries. It travels inferiorly and posteriorly across the trachea, behind the subclavian and azygous veins. It travels behind the hilum of the right lung, giving branches to the pulmonary plexus, before joining up with the left vagus nerve to form the oesophageal plexus. The left vagus nerve, similar to the right, passes between the subclavian and common carotid arteries, medial to the left phrenic nerve. It travels over the arch of the aorta, then posterior to the left hilum to form the oesophageal plexus with the right vagus nerve. The right recurrent laryngeal nerve splits from the right vagus and loops under the right subclavian artery before travelling superiorly, parallel to the trachea. The left loops under the aortic arch before travelling in the groove between the trachea and oesophagus. Clinical note: The left recurrent laryngeal nerve is at risk of injury during aortic dissection repair and nodal dissection in the aortopulmonary window. The patient will have a hoarse voice if the nerve is damaged, as it supplies the muscles of the vocal cords. The posterior cricoarytenoid is the only muscle to open the vocal cords.

●●

●●

Both the recurrent laryngeal nerve and phrenic nerves are at risk of injury from thymoma resection.

(Drake, Vogl & Mitchell 2015; Sinnatamby 2011; Moorjani, Viola & Walker 2016).

Thoracic duct The thoracic duct is the largest lymphatic vessel in the body, it is a continuation of the cisterna chyli and ascends through the aortic hiatus in the diaphragm to enter the posterior mediastinum. It continues in the right hemithorax and is situated between the descending thoracic aorta and

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the azygos vein. At the level of T5 it crosses into the left hemithorax and passes behind the oesophagus to continue up on its left side. The duct then passes anterior to the left subclavian artery and empties into the venous circulation at the level of the junction of the left internal and left subclavian vein (Moorjani, Viola & Walker 2016).

The oesophagus The oesophagus is a four-layer muscular tube. The outer adventitia is composed of loose connective tissue. The next layer, the muscular layer, has outer longitudinal muscles, then inner circular muscles. Deeper still is the submucosal layer, holding blood vessels, nerves and mucous glands. The lining of the oesophagus is stratified non-keratinised squamous epithelium overlying folds of lamina propria and muscularis mucosae. The oesophagus enters the thorax between the vertebral column and trachea in the midline. At the carina, it continues inferiorly to pierce the diaphragm at the oesophageal hiatus at the level of T10 (Sinnatamby 2011; Moorjani, Viola & Walker 2016).

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References Anderson, R.H. & Cook, A.C. (2014). ‘The Anatomy of Congenital Cardiac Malformations’ in: D. Yuh, L. Vricella, S. Yang & J. Doty (eds). Johns Hopkins Textbook of Cardiothoracic Surgery. 2nd edn. New York: McGraw Hill Education/Medical, 955–72. Di Biase, L. et al. (2012). Does the left atrial appendage morphology correlate with the risk of stroke in patients with atrial fibrillation? Results from a multicentre study. Journal of the American College of Cardiology. Elsevier Inc. 60(6), 531–38. Drake, R.L., Vogl, A.W. & Mitchell, A.W. (2015). ‘Thorax’ in Gray’s Anatomy for Students, 3rd edn. Philadelphia: Churchill Livingstone, 141–240. Drevet, G., Conti, M. & Deslauriers, J. (2016). Surgical Anatomy of the Tracheobronchial Tree, Journal of Thoracic Disease. 8(2), S121–S129. Ellis, H. (2006). ‘The Thorax’ in: M. Sugden & M. Misina (eds). Clinical Anatomy, 11th edn. Massachusetts: Blackwell, 1–52. Harington, C., Mora, S. & Wu, K.C. (2014). ‘Echocardiography in Cardiac Surgery’ in: D. Yuh, L. Vricella, S. Yang & J. Doty (eds). Johns Hopkins Textbook of Cardiothoracic Surgery. 2nd edn. New York: McGraw Hill Education/Medical, 893–920. Koenig Jr, G. & Efron, D. (2014). ‘Thoracic Trauma’ in: D. Yuh, L. Vricella, S. Yang & J. Doty (eds). Johns Hopkins Textbook of Cardiothoracic Surgery. New York: McGraw Hill Education/Medical, 9–24. Meier, P., Schirmer, S.H., Lansky, A.J., Timmis, A., Pitt, B. & Seiler, C. (2013). The collateral circulation of the heart. BMC medicine. 11(10), 143. Moorjani, N., Viola, N. & Ohri, S. (2011a). ‘Aortic Valve Disease’ in: N. Bramhill (ed.). Key Questions in Cardiac Surgery. 1st edn. Shrewsbury: tfm Publishing, 255–82. Moorjani, N., Viola, N. & Ohri, S. (2011b). ‘Cardiac Anatomy’ in: N. Bramhill (ed.). Key Questions in Cardiac Surgery. 1st edn. Shrewsbury: tfm Publishing, 1–32. Moorjani, N., Viola, N. & Walker, W.S. (2016). ‘Thoracic Anatomy’ in: N. Bramhill (ed.). Key Questions in Thoracic Surgery. 1st edn. Shrewsbury: tfm Publishing, 1–48. Okum, E.J. & DeAnda, A. Jr, (2014). ‘Pericardial Disease’ in: D. Yuh, L. Vricella, S. Yang & J. Doty (eds). Johns Hopkins Textbook of Cardiothoracic Surgery. 2nd edn. New York: McGraw Hill Education/Medical, 741–52. Predina, J. & Singhal, S. (2014). ‘Diaphragmatic Disorders’ in: D. Yuh, L. Vricella, S. Yang & J. Doty (eds). Johns Hopkins Textbook of Cardiothoracic Surgery. 2nd edn. New York: McGraw Hill Education/Medical, 309–21. Rushing, G.D. & Yuh, D.D. (2014). ‘Primary Coronary Artery Bypass Surgery’ in: D. Yuh, L. Vricella, S. Yang & J. Doty (eds). Johns Hopkins Textbook of Cardiothoracic Surgery. 2nd edn. New York: McGraw Hill Education/Medical, 387–406. Sinnatamby, C. (2011). ‘Thorax’, in: T. Horne & H. Kenner (eds). Last’s Anatomy: Regional and Applied. 12th edn. Edinburgh: Churchill Livingstone. 179–217. Timek, T.A. & Fann, J.I. (2014). ‘Mitral Valve Pathophysiology’ in: D. Yuh, L. Vricella, S. Yang & J. Doty (eds). Johns Hopkins Textbook of Cardiothoracic Surgery. 2nd edn. New York: McGraw Hill Education/Medical, 539–50.

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5 Preoperative assessment in cardiothoracic surgery Mohammed Suliman and Roberto Mosca

Introduction Recent advances in anaesthetic and surgical techniques, as well as continued improvements in perioperative care, have resulted in improved outcomes among patients undergoing cardiothoracic surgery. Decreased perioperative morbidity and mortality have been achieved despite the increasingly complex nature of patient cohorts. Timely and effective preoperative assessment of these patients has undoubtedly played a major part in recent progress (Weisberg et al. 2009). Patients presenting for cardiothoracic surgery pose several challenges for healthcare staff and require a nuanced approach to perioperative care. They are usually referred to the clinic by their surgeon or via their general practitioner. The preoperative assessment clinic acts as a crucial stop (in most cases the last one prior to surgery) where anaesthetists can assess, risk stratify, and highlight complex patients who are at a high risk of experiencing perioperative complications. This process includes identification and optimisation of patient comorbidities that may increase the risk of perioperative complications, a more thorough discussion with the patient regarding the expected perioperative journey, and better resource allocation and planning of strategies aimed at reducing perioperative risk. These developments have improved the quality of care, have minimised expenses and unnecessary tests, and improved healthcare delivery (Weisberg et al. 2009).

History and evolution of the preoperative assessment clinic The concept of preoperative assessment clinics dates back to 1949, when Dr Alfred Lee, a British anaesthetist, first realised that ‘the anaesthetist is frequently confronted with a patient, admitted from the waiting list, who is not in the best possible state for operation’ (Lee 1949, p. 169). Lee saw the need to medically optimise patients and address major health issues preoperatively, and thus recognised that it was ‘inadequate for the anaesthetist to see the patient the evening before operation,

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or even two or three days before…’. He proposed the very earliest version of the preoperative assessment clinic and went on to implement it in his local hospital in Southend-on-Sea. Lee’s idea did not spread and was not re-established until the early 1990s, when Fischer and his colleagues created a comprehensive preoperative assessment clinic at Stanford University (Fischer 1996), bringing to fruition the concepts initially proposed by Lee. The preoperative assessment clinic’s goals were to increase efficiency by coordinating the contributions of various specialty consultants, integrating laboratory services and diagnostic testing, and streamlining medical record retrieval. The clinic was successful in reducing unnecessary preoperative consultations, reducing diagnostic studies by 55%, and reducing day-of-surgery cancellations by 88%. The preoperative assessment clinic centralised all aspects of preoperative patient care and clearly improved the efficiency of patient preparation and raised patient satisfaction. However, Badner et al. (1998) recognised that many surgical candidates were relatively healthy and did not require the full preoperative assessment clinic assessment. Badner et al. (1998) described a hybrid system utilising a preoperative questionnaire to determine and screen a patient’s health status. The objective was to alleviate the strain on preoperative assessment clinic resources created by relatively healthy patients. Patients with positive questionnaires were referred to consultant anaesthetists, who then coordinated any additional assessments or tests that might be required. This led on to the use of preoperative screening questionnaires to stratify patients as ‘fit’ or ‘unfit for surgery’. Vaghadia & Fowler (1999) used a model that utilised a questionnaire to identify patients who might require further medical assessment. Their nurse-based model for screening patients had an accuracy of 81%, a specificity of 86%, and a negative predictive value of 93% when compared with anaesthesiologists’ recommendations. Van Klei et al. (2004) further quantified the effectiveness of utilising nurses to screen patients and found that, although nurses required 80% more time than physicians to complete an assessment, the nurses and anaesthesiologists disagreed on their subsequent assessments only 1.3% of the time. Successive modifications to the preoperative assessment clinic involved contacting patients by telephone to review their medical history, enabling them to avoid making a separate trip to the hospital for a preoperative assessment. Digner found that this system liberated resources, allowing preoperative assessment clinics ‘…to assess a greater number of patients with more complex medical and social care needs’ (Digner 2007, p. 298).

Benefits of the preoperative assessment clinic The Australian Incident Monitoring Study found that 3.1% of adverse events resulted from inadequate or incorrect preoperative assessment (Kluger et al. 2000). By optimising patients’ health preoperatively, patient morbidity and mortality are diminished, as is the rate of operating room cancellations or delays in a variety of countries. Ferschl et al. (2005, p. 859) reported that a preoperative assessment clinic reduced operating room cancellations and delays, with resultant savings of ‘$1430–1700 per operating room’. Any estimate of the savings generated by a preoperative assessment clinic should also of course include the emotional and social costs (in terms of missed work and productivity) of cancellations to patients and their families.

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Reducing the number of unnecessary laboratory or other tests performed preoperatively may also reduce perioperative costs and improve patient care. A study carried out at Toronto Western Hospital found that ‘…marked disparities in the practices of preoperative testing…’ existed among anaesthesiologists (Yuan et al. 2005, p. 675). The authors found that physicians often differed on exact criteria for ordering preoperative tests, such as Chest X-ray and ECGs in a healthy patient having low-risk surgery (knee arthroscopy, cataract removal, lens replacement and similar type surgeries). (Yuan et al. 2005). In fact, recent American College of Cardiology/ American Heart Association guidelines advise that ‘… “routine” preoperative ECG in asymptomatic patients undergoing low-risk operative procedures is not useful’ (Fleischer et al. 2014, p. e95). This confirms the fact that preoperative testing may not always be benign. In fact it could potentially expose patients to unnecessary tests, each with its own inherent risks. The obvious question is whether eliminating or reducing preoperative testing negatively affects patient outcomes. Ferrando et al. (2005) found that the application of preoperative guidelines decreased the number of preoperative tests ordered without affecting quality of care. In fact, ‘the evidence suggests that 60–70% of preoperative testing is unnecessary when a proper history and physical are done’. Chung et al. (2009, p. 467) found that routine preoperative testing for patients scheduled for ambulatory surgery, excluding those patients with significant medical illnesses (as defined by the study’s exclusion criteria), demonstrated ‘no significant differences in the rates of perioperative adverse events’.

Prospects for the preoperative assessment clinic The nature and set-up of pre-assessment clinics may vary between different institutions, e.g. the criteria or method used to identify which patients should be referred to the clinic, the type of provider (medical or nursing) that evaluates patients, and the design and physical location of the preoperative assessment clinic (on site at hospital, off site, or telephone- or Internet-based preoperative assessment systems). Future investigations into standardisation of preoperative testing may lead to a reduction in variation in preoperative testing practices. There is scope for greater expansion in telephone- and internet-based preoperative assessment systems – by creating specialty centres that cover entire geographic regions, allowing savings through integration of services and economies of scale. These savings, currently unattainable due to disjointed, non-standardised preoperative assessment schemes, could then be reinvested in the healthcare system. Additionally, the prospect of integrating the preoperative assessment system with the electronic medical record may help to streamline the preoperative assessment process.

Preoperative assessment and same day admissions in cardiothoracic surgery Historically, patients presenting for cardiothoracic surgery were usually admitted several days before the operation to allow time for the necessary preoperative assessments and investigations.

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In most cases, this led to unnecessary acute bed occupancy, long waiting times, time limits for evaluation, and ultimately decreased patient satisfaction. The development of, and continued improvement in, preoperative assessment programmes have naturally led some institutions to establish same day admissions in cardiothoracic surgery, with great success. This approach may not have been possible without robust outpatient preoperative evaluation (Silvay et al. 2016).

Preoperative assessment in cardiac surgery Introduction Patients presenting for cardiac surgery pose several challenges for healthcare staff and require a nuanced approach to perioperative care. As well as their primary cardiac disease, these patients commonly have several other comorbidities. A thorough preoperative evaluation remains an essential part of the perioperative care of this group. It allows identification of those at high risk of perioperative complications and promotes development of individualised care plans to mitigate these risks.

Pre-admission clinics Pre-admission clinics have now become a well-established feature of most units around the country, where elective patients are assessed several weeks prior to surgery. The exact timing varies between different institutions and according to local guidelines. There are well-established benefits to this approach. Relevant investigations and imaging can be requested and reviewed with ample time before surgery; problems can be highlighted, support services alerted (e.g. transfusion), and action plans put in place to facilitate a smooth perioperative pathway and minimise delays or cancellations. It also allows an opportunity for adequate patient counselling to take place.

History and examination In elective cases, the diagnosis is generally established by the time the patients present for their preoperative assessment. An assessment of current disease symptoms (such as angina, dyspnoea, orthopnoea, exercise tolerance and syncope) will assist in the process of perioperative risk stratification. The severity of these symptoms can also be measured against validated scores, such as the Canadian Cardiovascular Society Angina Score (Canadian Cardiovascular Society 2018) (see Table 5.1) and the New York Heart Association Classification for Functional Capacity (New York Heart Association 2017) (see Table 5.2). This can be followed by a brief systems enquiry to exclude gastrointestinal, renal, hepatic, neurological, metabolic or haematological disease. A history of gastroesophageal reflux, hiatus hernia or swallowing problems will be especially important in airway management and risks around transoesophageal echo probe insertion. Comorbidities (such as respiratory disease, peripheral vascular disease, hypertension, diabetes mellitus, renal impairment and neurological disease) are associated with increased perioperative mortality and morbidity. Therefore, it is important to elicit details about the severity and management of these conditions. Records of previous surgery should be scrutinised, including any adverse events or anaesthetic difficulties. Permanent pacemakers or implanted defibrillator devices should be

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evaluated, and a perioperative plan put in place, in cooperation with cardiac technologists. Furthermore, the patient’s religious beliefs or cultural views should be explored, as these may have major implications for perioperative care (as in the case of Jehovah’s witnesses).

Table 5.1: This table summarises the grading of angina pectoris. (adapted from the Canadian Cardiovascular Society 2018) Canadian Cardiovascular Society (CCS) Grading of Angina Pectoris Class I

No limitation of usual physical activities. Angina only during strenuous or prolonged physical activity.

Class II

Slight limitation of ordinary physical activities.

Class III

Marked limitation of ordinary physical activities.

Class IV

Inability to perform any physical activities without angina, or, angina at rest.



Table 5.2: This table summarises the functional classification of breathlessness. (adapted from the New York Heart Association 2017) New York Heart Association Functional Classification (NYHA) Class I

Asymptomatic cardiac disease, with no limitation in ordinary physical activity.

Class II

Mild symptoms (mild shortness of breath and/or angina) and slight limitation during ordinary physical activities.

Class III

Marked limitation in physical activity due to symptoms. Comfortable only at rest.

Class IV

Severe limitation in physical activity. Symptomatic even at rest.



Medications A review of the drugs and medications list will yield information about the management of comorbidities. It is important to highlight any drugs that may interfere with coagulation (e.g. aspirin, clopidogrel, glycoprotein IIb/IIIa antagonists, thrombolytics, heparin and warfarin) and the interval since their cessation. For antiplatelet drugs, such as aspirin and clopidogrel, the usual advice is to stop taking them 7 days before surgery. This may be unwise in some circumstances, due to the pattern and severity of the coronary artery disease, in which case antiplatelets should be continued and platelet inhibition assays performed perioperatively to guide management and transfusion therapy. It is advisable to liaise directly with a specialist haematologist in such circumstances. Current guidelines state that aspirin and clopidogrel should be continued up to the day of surgery in patients who require surgery within 6 months of insertion of a bare metal intracoronary stent, or within 12 months of drug-eluting stent. Anticoagulants such as warfarin should be stopped 3–5 days prior to surgery to allow the prothrombin time to normalise. In some circumstances, where it is critical that preoperative anticoagulation is maintained, e.g. in the presence of a mechanical valve, the patient should be admitted to hospital and therapeutic low molecular weight heparin or unfractionated intravenous heparin should be given instead. In

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patients with chronic atrial fibrillation, low molecular weight heparin can be provided for selfadministration at home. In emergency situations, it may be helpful to liaise with a haematologist to ensure appropriate blood products and factor concentrates are available. Newer anticoagulants such as Dabigatran (a direct thrombin inhibitor) are now being used more widely. However, these drugs can pose particular difficulties, as patients are at significant risk of perioperative bleeding and clinicians are less familiar with their use and their clinical effects. Furthermore, until recently, a reversal agent was not available. However, at the time of writing, UK authorities had approved the use of Idarucizumab as the first agent to be licensed for the reversal of the anticoagulant effect of a non-vitamin K antagonist oral anticoagulant (NICE 2016). Its action is specific against the NOAC Dabigatran. Idarucizumab is effective within minutes and can be used in an emergency. In elective surgery, NOACs are normally stopped 2–3 days before surgery (Sunkara et al. 2016). Most other cardiac drugs, such as beta blockers, nitrates and statins, should be continued up to the day of surgery. In our institution, angiotensin converting enzyme inhibitors and angiotensin receptor blockers are stopped 1–2 days prior to surgery. However, the author recognises the controversy regarding their cessation.

Physical examination Physical examination should focus on the cardiovascular and respiratory systems, including measurement of heart rate, arterial blood pressure and respiratory rate; characterisation of heart rhythm; palpation of carotid, femoral and peripheral pulses; and auscultation of the precordium, carotid arteries and lung fields. Assessment of dentition and oral hygiene, mouth opening, and neck movement is useful in anticipating difficulties with airway management. Furthermore, in patients with neurological disease, it is important to document the extent and severity of neurological deficits preoperatively, to act as a baseline for postoperative assessment.

Blood tests A full blood count, coagulation studies, blood group determination, measurement of serum electrolytes, urea, creatinine and hepatic enzymes are regarded as routine in virtually all patients. The full blood count will exclude any anaemia, platelet or leucocyte quantitative abnormalities. The estimated glomerular filtration rate (eGFR) can provide more accurate assessment of renal function than creatinine levels alone. The normal eGFR in a healthy adult is 90–120ml/ minute/1.73m2. Levels lower than 60 suggest at least moderate renal impairment. Chronic diuretic therapy may cause total-body sodium or potassium depletion and uraemia. Thromboelastography is quickly superseding basic laboratory coagulation tests as the investigation of choice in many institutions, as it represents a more holistic overview of the clotting cascade. Platelet assays are especially useful for assessing platelet function or indeed dysfunction in patients on antiplatelet drugs near the time of surgery.

Electrocardiogram A preoperative baseline ECG may be abnormal in a significant proportion of patients. It may indicate previous myocardial infarction, conduction defects, cardiac arrhythmias, etc., and will be

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helpful in detecting any postoperative changes. Evidence of previous myocardial infarction may necessitate echocardiographic investigation to assess ventricular function prior to surgery. Some conduction defects may require temporary pacing, which can be converted into permanent pacing postoperatively. Some preoperative arrhythmias (such as atrial fibrillation) will benefit from medical optimisation in the run-up to surgery.

Chest X-ray A plain chest X-ray provides information about the heart size, lung fields, pulmonary vasculature and bony anatomy of the chest. It is essential when assessing patients with chronic lung disease. It also provides a baseline against which to compare in the event of postoperative pulmonary complications. Furthermore, it can pick up incidental findings (such as lung masses), which may have significant implications for perioperative planning.

Exercise tolerance test Exercise testing is occasionally used as a screening test before coronary angiography. Patients suspected of having ischaemic heart disease will undergo a standardised protocol (e.g. modified Bruce protocol) of increasing physical exercise (usually on a treadmill) with continuous ECG and blood pressure monitoring to detect signs of ischaemia and cardiac compromise. Each patient will be set a predetermined age-specific maximum heart rate. A positive test is defined by the onset of chest pain or diagnostic ECG changes, the development of hyper/hypotension, fatigue, dyspnoea, or any arrhythmias, which may indicate cardiac decompensation. The test is then terminated. Alternatively, if the patient achieves this predetermined heart rate without the onset of any of the above, the test is declared negative. However, the test has its limitations: it cannot be performed on patients who are unable to exercise (for instance, due to musculoskeletal problems or disability); it is also difficult to interpret in patients taking beta blockers, with pacemakers, or with known left bundle branch block.

Cardiac catheterisation and coronary angiography Cardiac catheterisation provides information regarding coronary disease, ventricular function, trans-valvular pressure gradients, pulmonary vascular resistance, and a range of intra-cardiac pressures from both right and left heart chambers. The injection of radio-opaque dye into the coronary arteries displays their anatomy and the presence and severity of disease. Direct measurement of left ventricular end-diastolic pressure provides an indirect assessment of left ventricular function. Right heart catheterisation allows measurement of pulmonary artery pressures, cardiac output, trans-pulmonary gradient and pulmonary vascular resistance.

Echocardiography Echocardiography is helpful in assessing cardiac structure and function. It allows detailed measurement of chamber dimensions, systolic and diastolic function, valvular pathology and pressure gradients. Transthoracic echo provides a non-invasive modality useful in monitoring disease progression and assisting in determining the timing and type of surgical intervention. On the other hand, transoesophageal echo (TOE) generally provides better-quality images due

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to the relative proximity of the heart to the TOE probe within the oesophagus. Therefore, it is particularly useful in assessing mitral valve disease, for looking for vegetations in endocarditis, and for detecting intramural thrombi. Three-dimensional echo is now also available, potentially allowing for superior studies.

Pharmacological stress testing In patients who are unable to exercise (e.g. due to mobility restrictions or disability), drugs such as dobutamine can be used to stress the heart while being imaged echocardiographically (stress echo). These drugs increase the metabolic demands of the heart (for example, by inducing a tachycardia), which in turn reveals regional wall motion abnormalities, indicating areas of compromised perfusion due to coronary artery disease. An alternative approach is injecting a radionuclear substance (such as thallium or technetium) prior to stressing the heart (either conventionally through exercise or pharmacologically). The distribution of myocardial perfusion is then assessed using a gamma ray camera. Perfusion defects on images detected by the camera will correspond to territories with poor blood supply. The scan is repeated 3 hours later to check for delayed radionuclide accumulation in the ischaemic areas. This helps distinguish between reversible and non-reversible ischaemia, thus differentiating between viable myocardium and non-viable scar tissue. Stress echocardiography is being increasingly utilised in the preoperative period in the process of risk stratification. It helps to emulate the physiological challenges to the heart brought about by surgery and can therefore reveal the true functional capacity of the heart in such conditions, as opposed to providing a snapshot assessment at rest.

Cardiac computed tomography High-resolution cardiac CT and CT angiography can be used to provide detailed three-dimensional images of the heart, coronary arteries and the great vessels. CT angiography can also offer an alternative to coronary angiography in imaging coronary anatomy.

Cardiac magnetic resonance imaging Cardiac anatomy, function, perfusion and tissue viability can all be examined with a high degree of accuracy using magnetic resonance imaging (MRI) without the use of ionising radiation. Intravenous dobutamine can be used to produce a stress cardiac MRI study to detect ischaemic areas, while a gadolinium contrast cardiac MRI can distinguish between viable and non-viable tissue. Furthermore, MRI angiography provides a detailed three-dimensional assessment of vessel architecture and blood flow in the cardiovascular system.

Pulmonary function tests A considerable number of patients presenting for cardiac surgery suffer from chronic lung disease. These patients are at increased risk of developing postoperative pulmonary complications. Preoperative pulmonary function testing should therefore be carried out in all patients to assess the severity of lung disease and to anticipate difficulties in the postoperative period (Najafi, Sheikhvatan & Mortazavi 2015).

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Tests performed include arterial blood gas analysis, pulse oximetry, spirometry, lung volume assessment and gas transfer. Tests are repeated following administration of inhaled bronchodilators to assess disease reversibility. A forced expiratory volume (FEV) in 1 second of less than 2 litres, or less than 50% of the predicted value, is associated with a significantly increased risk of postoperative pulmonary complications. Furthermore, a FEV1 of less than 1 litre is associated with difficulty with sputum clearance postoperatively and probable need of additional ventilator support. In addition, the diffusing capacity of the lungs for carbon monoxide provides information on the ability to transport gases from the alveoli to the capillaries. A DLCO of less than 70% of predicted capacity is associated with an increased risk of clinically important postoperative pulmonary complications.

Carotid doppler scans Cerebrovascular injury is a recognised and devastating complication of cardiac surgery. Elderly patients are at particular risk and therefore carotid doppler studies are routinely performed, prior to cardiac surgery, on all patients over 65 years to rule out significant carotid atheromatous disease. In addition, carotid dopplers are performed on all patients with a history of previous stroke, transient ischaemic attacks or carotid bruits noted on physical examination. Greater than 50% stenosis is considered as significant carotid disease (da Rosa et al. 2013). Decision-making regarding the timing of cardiac vs carotid surgery then follows a multidisciplinary approach based on risk stratification, clinical context and symptomatology.

Cardiopulmonary exercise testing Cardiopulmonary exercise testing represents an objective measurement of functional capacity. It measures the integrated response of cardiac, pulmonary and muscular systems to a progressively increasing workload. The patient exercises on a bicycle ergometer or treadmill. They are connected to an ECG and have their inspired and expired gases (oxygen uptake and carbon dioxide production) continuously measured. As exercise progresses, the patient’s energy requirements will eventually outstrip that provided by aerobic respiration and thus anaerobic respiration ensues. This results in an increase in VCO2. This point is described as the ‘anaerobic threshold’. Further increase in exercise will yield a point of maximal oxygen uptake and utilisation, the VO2 max. These parameters (anaerobic threshold and VO2 max) have been shown to have prognostic value in non-cardiac surgery (Smith et al. 2009).

Risk assessment The production of large databases has facilitated the development of risk stratification models. Models range from very simple additive models that can be used at the bedside, to sophisticated systems involving the application of complex algorithms. The Parsonnet score and the European System for Cardiac Operative Risk Evaluation are the most widely used and have both been well validated. The latter has been further refined, and in 2011 EuroSCORE II was published (EuroSCORE Study Group 2011). However, some determinants of surgical outcomes were not incorporated in these scores, such as the surgeon’s competence, institutional expertise in handling

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emergencies, and financial affordability. Caution must therefore be exercised in applying these scores, especially in the context of developing countries, where the above factors vary widely between different institutions (Malik et al. 2010). Regardless of which risk stratification model is used, higher scores tend to be associated with increased postoperative complications, increased length of stay and increased perioperative mortality.

Emergency cardiac patient preoperative assessment Emergency cardiac surgery presents a series of unique challenges. Important information and documentation may not be available regarding the patient’s current illness and past medical history, especially if the patient is unable to provide such information. The patient may be on, or recently exposed to, anticoagulant, antiplatelet or thrombolytic drugs. They may have been transferred from a separate hospital and colonised with a resistant strain of bacteria. All the above may be in the context of cardiovascular instability or compromise, necessitating urgent surgical intervention. In this situation, a prioritised but nonetheless structured approach to history taking, physical examination and investigations cannot be emphasised enough, so as not to miss anything of significance. Good effective communication is necessary between members of the multidisciplinary team, including cardiac surgeons, cardiologists, anaesthetists, perfusionists, theatre staff and ward staff. Adhering to published guidelines, local protocols, and perioperative checklists mitigates risk and enhances safety and the quality of care (Treadwell, Lucas & Tsou 2014).

Preoperative assessment in lung surgery Introduction Preoperative assessment in lung surgery is a cornerstone of the perioperative management of patients presenting for lung surgery. Preoperative assessment and optimisation of respiratory function can help minimise the incidence of postoperative pulmonary complications, a leading cause of perioperative morbidity and mortality in lung surgery (Nagarajan et al. 2011). Major respiratory complications include atelectasis, pneumonia and particularly respiratory failure requiring prolonged mechanical ventilation. The extent of lung resection is also strongly associated with mortality, with pneumonectomy demonstrating 2–3 times higher mortality, compared to lobectomy (Ferguson et al. 2014). The Thoracic Surgery Scoring System (Thoracoscore) (Falcoz et al. 2007) (see Table 5.3) is a well-validated tool that has proven its utility in the preoperative risk prediction for perioperative mortality. Sadly, no single test can accurately predict outcomes following lung resection surgery.

Age There is no cut-off age at which patients are no longer eligible for lung resection. However, it is recognised that the incidence of respiratory and cardiac complications rises with age (Liu et al.

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2013). The mortality rate following pneumonectomies, especially right-sided surgery, remains high (22% in patients >70 years). This is presumably due to the increased right-heart strain caused by resection of the proportionally larger vascular bed of the right lung (Spaggiari & Scanagatta 2007).

Table 5.3: This table lists the Thoracoscore factors which predict the in-hospital mortality of thoracic surgery patients Thoracoscore factors for predicting in-hospital mortality for patients requiring thoracic surgery Age (65 years) Sex ASA classification (≤2, ≥3) Performance status according to Zubrod scale (≤2, ≥3) Severity of dyspnoea according to Medical Research Council Scale (≤2, ≥3) Priority of surgery (elective, urgent/emergency) Extent of resection (pneumonectomy, other) Diagnosis (malignant, benign) Comorbidity score ASA, American Society of Anaesthesiologists

Chronic obstructive pulmonary disease The most common concurrent illness in the thoracic surgical population is chronic obstructive pulmonary disease (COPD). Severity is usually classified on the basis of the FEV1 percentage, based on predicted values. The American Thoracic Society currently categorises Stage I >50% predicted, Stage II as 35–50%, and Stage III 50%

Effective regurgitant orifice area

>0.3cm2

Jet width (LVOT diameter)

>65%

Indications for surgery According to the 2017 ESC/EACTS Guidelines for the management of valvular heart disease, there is evidence for intervention for aortic valve disease in the following scenarios (Baumgartner et al. 2017). In aortic stenosis: ●●

Symptomatic patients with severe aortic stenosis (class I)

Asymptomatic patients with severe aortic stenosis and left ventricular ejection fraction 5.5m/s

●●

Peak velocity progression >0.3m/s/year in the presence of severe valve calcification

●●

Markedly elevated BNP levels (>3 times corrected normal range)

●●

Severe pulmonary hypertension (systolic pulmonary artery pressure >60mmHg).

In aortic regurgitation: ●●

Symptomatic patients with severe aortic regurgitation (class I)

Asymptomatic patients with severe aortic regurgitation and left ventricular ejection fraction (LVEF) 50% with severe LV dilatation (left ventricular end-diastolic diameter >70mm or left ventricular end-systolic diameters >50mm) (class IIa).

●●

Surgical approaches and considerations Selection of prosthetic valve Most aortic valve surgery currently undertaken in the United Kingdom is replacement of the aortic valve. A small number of centres perform aortic valve repair surgery, which avoids the need for any form of prosthetic valve but this is a specialised technique only suitable in cases where both the anatomy and pathology of the aortic valve disease are favourable. Hence aortic valve repair is reserved for cases where the surgeon is confident that a durable and high-quality repair can be performed. Early failure of aortic valve repair often leads to redo cardiac surgery, negating any initial benefit. Prior to aortic valve surgery, the surgeon and patient should engage in shared decisionmaking regarding the most appropriate type of prosthetic valve. The main factors when considering valve choice are the durability of the prosthesis and the need for anticoagulation. The two main types of valve currently available are bioprosthetic (tissue) or mechanical.

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Bioprosthetic or biological valves are derived from animal tissues, such as porcine (pig), bovine (cow) and equine (horse) models, and then fixed in a preserving solution that may be mounted on a flexible frame to assist in deployment during surgery (Harris, Croce & Cao 2015a). A bioprosthetic valve has leaflets constructed from bovine pericardium or porcine aortic valves. Porcine valves are made of pig aortic valves that have been treated in a preservation liquid and mounted on flexible frames. The frame is designed to be flexible at the opening as well as where the leaflets come together, thus replicating the native aortic valve. The main advantage of bioprosthetic valves is that there is no need for anticoagulation therapy to reduce the risk of clot formation. However, they have limited durability and their lifespan does not normally exceed 15–20 years. For all these reasons, a bioprosthetic valve is the valve of choice for most patients over the age of 65, with excellent long-term outcomes (Jaffer & Whitlock 2016). A mechanical valve has a much longer lifespan and can therefore be implanted into younger patients with minimal risk of additional surgery being required later in life. However, to minimise the risk of significant clot formation on the leaflets of the valve, lifelong anticoagulation therapy is required. Poor compliance with this anticoagulation therapy can lead to greater risks of thrombosis or haemorrhage. Lifestyle is affected by anticoagulation therapy, due to the need to abstain from contact sports and avoid certain foodstuffs and excessive alcohol intake. Anticoagulants are also teratogenic. This means that women of childbearing age who wish to become pregnant cannot safely be given a mechanical valve. They must either opt for a bioprosthesis (accepting the need for redo surgery) or receive a mechanical valve and agree to comply with anticoagulation, accepting that they will no longer be able to conceive a child (Jaffer & Whitlock 2016; Vause et al. 2016).

Operative techniques Traditional aortic valve surgery is performed through a median sternotomy. Once the pericardium has been incised and total body heparin has been given, the heart is cannulated, and cardiopulmonary bypass is commenced. Cardioplegia cannulas are then inserted so that the heart can be adequately arrested and protected once the cross-clamp has been applied. Cardioplegia strategy depends on surgeon preference, anatomy, surgical access and the specific pathology of the individual patient’s aortic valve disease. Following application of the cross-clamp, initial cardioplegia is delivered through the antegrade cannula into the aortic root. If the predominant pathology of the aortic valve is regurgitation, a significant proportion of the cardioplegia will regurgitate into the heart, causing LV distension. The amount of cardioplegia directed down the coronary ostia will therefore also be reduced. To adequately arrest and protect the heart in this situation, retrograde cardioplegia can be given, delivered through a cannula inserted into the coronary sinus. Alternatively, an aortotomy can be performed, allowing for direct cannulation of the individual coronary ostia and selective delivery of cardioplegia down the left and right ostia as required. The insertion of a vent is also performed in certain cases, again depending on surgical access and surgeon preference. This is an additional cannula, inserted into the heart to reduce the amount of blood in the left ventricle, thus ensuring a totally bloodless field and non-distended

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ventricle. Common sites of insertion for the LV vent include the right superior pulmonary vein and the pulmonary artery. Once the heart is adequately arrested, protected and vented, the aortic valve can be properly exposed, usually by using stay sutures and hand-held retractors as required. The native valve is excised, and the annulus thoroughly decalcified. The surgeon is then able to estimate the size of the annulus using specific valve sizers. Having settled on the correct size, the prosthetic valve can be opened and prepared by the scrub practitioner. Sutures will then be taken through the annulus. While this can be a semi-continuous suture, especially if the annulus is of particularly good quality, the usual choice is multiple interrupted sutures (see Figure 7.1). Surgeon preference and the quality of the annulus will determine whether any, some or all the sutures are pledgeted. Once they have been passed through the annulus, the sutures are also passed through the valve, which is then deployed down into position within the aorta (see Figure 7.2). While taking sutures through the aortic annulus, particular care must be taken to avoid causing damage to any of the surrounding structures. After the sutures are tied and cut, and the valve is fixed in place, it is important to ensure that both coronary ostia have been visualised and have not been occluded or obstructed by the presence of the prosthetic valve (see Figure 7.3). The aortotomy is then closed as the patient is rewarmed. De-airing manoeuvres are then performed and the cross-clamp removed. Ventricular and atrial epicardial pacing wires are attached in order to overcome any significant rhythm disturbances. Once the patient has been weaned from cardiopulmonary bypass, intra-operative transoesophageal echo (TOE) is used to assess the valve to ensure that there is no significant paravalvular leak. The TOE is also used to check for any residual air within the chambers of the heart. Once appearances are satisfactory, the heparin is reversed with protamine, haemostasis secured and the patient closed in layers, with stainless steel wires used for approximation of the sternum.

Minimal access aortic valve surgery More recently, some aortic valve surgery has been performed using a minimal access approach, either completely or partially avoiding division of the sternum. In select cases the approach can be via a right anterior thoracotomy, but more usually a minimal access aortic valve replacement is performed via mini sternotomy. This is where the sternum is only partially divided, usually up to the level of the 3rd or 4th intercostal space, with either an inverted T- or J-shaped incision in order to allow the sternum to be spread. The visible pericardium is then divided in the usual fashion in order to gain access to the aorta. While access to the aorta is preserved, it can be more difficult to access other structures within the chest and so the operative technique must be modified. Aortic cannulation is performed as normal but direct cannulation of the right atrium is often very difficult and hence insertion of a peripheral venous cannula through the common femoral vein is frequently used as an alternative. Additional venous cannulation techniques include direct superior vena cava (SVC) cannulation. Due to the limited space, it is not possible to insert a retrograde cardioplegia cannula so cardioplegia is delivered through the root or directly down the coronary ostia. During delivery of the initial dose of cardioplegia it is important to ensure that the anaesthetist is using the TOE

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to assess for evidence of ventricular distension. Excision of the native valve and implantation of the prosthetic valve is performed in the same way as for traditional aortic valve replacement, but the use of specialised minimal access instruments may be required, due to the restricted access.

A

B

C

D

Figure 7.1: The mechanical valve in-situ with interrupted sutures A: Interrupted valve sutures B: Prolene stay suture C: Exposed aorta with stay sutures D: Mechanical aortic valve in situ

A

B

Figure 7.2: The final check inside the left ventricle to make sure that all the valve sutures are in place and the valve is in the correct position A: Interrupted valve sutures B: Mechanical valve leaflet in open position

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A

B C D

E

F

Figure 7.3: The valve in position, showing that the coronary ostia is not obstructed A: Venous cannula B: Retrograde cardioplegia cannula C: Redo Aortic thickened wall D: Coronary ostia E: Mechanical valve in situ F: Antegrade cardioplegia cannula

Postoperative management Initial postoperative management is in the critical care environment, prior to transfer to the ward. Patients with aortic valve disease, particularly those with chronic pathology, tend to have hypertrophic, dilated and poorly compliant ventricles. Their ability to compensate when any factors affecting cardiac output are compromised is therefore significantly reduced. Haemodynamic control is paramount. While adequate fluid maintenance in order to maintain preload is important, postoperative hypertension must be avoided in order to protect the aortic suture line. Moreover, in the presence of a poorly compliant ventricle, the atrial contribution to cardiac output becomes particularly important, as these patients tolerate postoperative atrial fibrillation poorly. All patients undergoing aortic valve replacement should have both atrial and ventricular pacing, and postoperative atrial fibrillation should be treated aggressively, with a low threshold for both chemical and mechanical cardioversion as required. Due to the manipulation of tissue in the area of the conduction system, postoperative heart block can sometimes be seen. This is often transient, and due to oedema of the surrounding tissues, but if persistent, iatrogenic damage to the conduction system is a possibility, and insertion of a permanent pacemaker should be considered. Prompt initiation of anticoagulants should occur in patients who have received a mechanical prosthesis. If the international normalised ratio is not therapeutic by the third or fourth postoperative day, bridging (in the form of therapeutic-dose heparin) should be considered. Other postoperative complications, such as stroke and mortality, are infrequent, with an incidence of around 1% in uncomplicated aortic valve replacement.

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Clinical scenario 1 A 65-year-old male underwent an uneventful elective tissue aortic valve replacement and was transferred to the cardiac intensive care unit. Eight hours after surgery he remained persistently hypotensive and had increasing inotropic requirements. An urgent transoesophageal echocardiogram did not demonstrate any evidence of cardiac tamponade. Biventricular systolic function remained good, but the heart appeared to be underfilled.

Discussion Patients who have had progressively worsening aortic stenosis for many years will often develop left ventricular hypertrophy. This is a coping mechanism employed by the left ventricle due to the increased pressure required by the ventricle to pump blood through the increasingly narrowed valve orifice area of the aortic valve. However, this also worsens the compliance of the ventricle, causing a ‘stiff’ ventricle which is unable to react adequately to changing physiological parameters in order to preserve cardiac output and is therefore dependent on high filling pressures. Patients who have undergone aortic valve replacement often require much more aggressive fluid replacement in order to maximise preload and hence improve cardiac output by increasing stroke volume. The degree of filling required can be assessed by haemodynamic parameters (including CVP and PA catheter measurements) and also by direct visualisation of the ventricle on transoesophageal echocardiography.

Clinical scenario 2 A 73-year-old female underwent an uneventful, elective tissue aortic valve replacement and was transferred to the cardiac intensive care unit. She was successfully extubated and was making an excellent postoperative recovery. On the second postoperative day, she developed fast atrial fibrillation and became haemodynamically unstable, requiring urgent cardioversion.

Discussion Atrial fibrillation following cardiac surgery is a frequently encountered complication. It is often well tolerated by patients and can be treated with pharmacological agents such as oral beta blockers and/or intravenous amiodarone. A small number of patients will develop such significant haemodynamic instability as a result of the dysrhythmia that urgent restoration of sinus rhythm with electrical cardioversion is required. It is well recognised that effective atrial contraction (the so-called ‘atrial kick’) can increase cardiac output by up to 30% due to its important contribution to the ventricular end diastolic volume. Hence adequate or inadequate atrial function can have a significant impact on stroke volume and cardiac output. As previously discussed, the stiff and poorly compliant ventricle often encountered in patients with aortic stenosis due to chronic left ventricular hypertrophy means that these patients are dependent on good filling pressures to preserve cardiac output and are acutely sensitive to any changes in preload. In this situation, the abrupt reduction in atrial contribution to ventricular enddiastolic volume due to lack of coordinated atrial contraction as a result of the atrial fibrillation

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has caused a sudden and unexpected drop in cardiac output, which has manifested clinically as significant hypotension. This represents a clinical emergency, requiring emergency electrical cardioversion in order to restore sinus rhythm and improve haemodynamics.

Conclusion The aim of this chapter has been to provide the reader with a broad overview and understanding of aortic valve disease. Beginning with a review of the anatomy and physiology of the aortic valve, before proceeding to the pathophysiology and aetiology of aortic valve disease, both aortic regurgitation and aortic stenosis have been explored. Surgical aortic valve replacement has been discussed, with consideration given to some of the newer, pioneering techniques such as the minimal access approach.

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References Baumgartner, H., Falk, V., Bax, J.J., De Bonis, M., Hamm, C., Holm, P.J., Lung, B., Lancellotti, P., Lansac, E., Muñoz, D.R., Rosenhek, R., Sjögren, J., Tornos, P., Vahanian, M.A., Walther, T., Wendler, O., Windecker, S., Zamorano, J.L. & ESC Scientific Document Group (2017). ESC/EACTS Guidelines for the management of valvular heart disease. European Heart Journal. 38(36), 2739–91. Drake, R.L., Vogl, A.W. & Mitchell, A.W. (2015). ‘Thorax’ in: Gray’s Anatomy for Students, 3rd edn. Philadelphia: Churchill Livingstone, 141–240. Harris, C., Croce, B. & Cao, C. (2015a). Tissue and mechanical heart valves. Annals of Cardiothoracic Surgery. 4(4), 399. Hinton, R.B. & Yutzey, K.E. (2011). Heart valve structure and function in development and disease. Annual Review of Physiology. 73, 29–46. Jaffer, I.H. & Whitlock, R.P. (2016). A mechanical heart valve is the best choice. Heart Asia. 8(1), 62–64. Lung, B. & Vahanian, A. (2014). Epidemiology of acquired valvular heart disease. The Canadian Journal of Cardiology. 30(9), 962–70. Maurer, G. (2006). Aortic regurgitation. Heart. 92(7), 994–1000. Moorjani, N. Viola, N. & Ohri, S. (2011). ‘Aortic Valve Disease’ in: N. Bramhill (ed.) Key Questions in Cardiac Surgery, 1st edn. Shrewsbury: tfm Publishing. 255–82. Olszowska, M. (2011). Pathogenesis and pathophysiology of aortic valve stenosis in adults. Polskie Archiwum Medycyny Wewnetrznej. 121(11), 409–13. Roberts, W.C. (1970). The congenitally bicuspid aortic valve. A study of 85 autopsy cases. The American Journal of Cardiology. 26(1), 72–83. Roberts, W.C. (1992). Morphologic aspects of cardiac valve dysfunction. American Heart Journal. 123(6), 1610–32. Robicsek, F., Thurbrikar, M.J., Cook, J.W. & Fowler, B. (2004). The congenitally bicuspid aortic valve: how does it function? Why does it fail? The Annals of Thoracic Surgery. 77(1), 177–85. Shabana, A. (2014). Bicuspid aortic valve. European Society of Cardiology. 13(2). https://www.escardio.org/Journals/EJournal-of-Cardiology-Practice/Volume-13/Bicuspid-aortic-valve (Last accessed 12.3.2019). Taniguchi, Y., Morimoto, T., Shiomi, H., Ando, K., Kanamori, N., Murata, K., Kitai, T., Kawase, Y., Izumi, C., Kato, T., Ishii, K., Nagao, K., Nakagawa, Y., Toyofuku, M., Saito, N., Minatoya, K., Kimura, T. & the CURRENT AS Registry Investigators (2018). Sudden death in patients with severe aortic stenosis: Observations from the CURRENT AS Registry. Journal of the American Heart Association. 7(11), e008397. Thaden, J.J., Nkomo, V. & Enriquez-Sarano, M. (2014). The global burden of aortic stenosis. Progress in Cardiovascular Diseases. 56(6), 565–71. Vause, S., Clarke, B., Tower, C., Hay, C. & Knight, M. (2016). Pregnancy outcomes in women with artificial heart valves. https://www.npeu.ox.ac.uk/ukoss/current-surveillance/ahv (Last accessed 12.3.2019).

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Mitral valve disease and mitral valve surgery James Barnard

Introduction Operations on the mitral valve are technically very satisfying for the surgeon and they offer significant benefits for patients, in terms of treating symptoms of heart failure and prolonging quality of life. There are various operative techniques for repair of the valve, for replacement and for minimally invasive intervention. There is also much ongoing research looking into the benefits of new treatment modalities. This chapter describes the anatomical structure of the mitral valve, the pathophysiology, the aetiology of mitral valve disease and the symptoms and signs that patients present with. It then goes on to describe the surgical treatments that are currently available.

Anatomical structure of the mitral valve The function of the mitral valve is to maintain forward flow of blood between the left atrium and the left ventricle. It has anterior and posterior leaflets. It is an asymmetrical oval in shape, with one side flattened slightly where the valve is in contact with the aortic valve and with the anterior leaflet occupying most of the cross-sectional area of the valve when it is closed. The one-way mechanism of the mitral valve is facilitated by string-like structures called chordae tendineae, which originate from the papillary muscle and attach to different areas on the ventricular surface of the mitral valve leaflet. These chords are classified as primary, secondary and tertiary, depending on their area of attachment to the mitral valve leaflet (McCarthy, Ring & Rana 2010). Each leaflet is divided into three scallops: P1, P2 and P3 of the posterior leaflet, starting from anterolateral to posteromedial commissure; and the corresponding area on the anterior leaflet, divided into A1, A2 and A3. The mitral annulus is saddle-shaped and is divided into the anterior and posterior annulus according to the leaflet attachment. The mitral annulus is an anatomical border between the ventricle and the atrium. The anterior leaflet of the valve attaches to the fibrous

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skeleton of the heart. There are two more prominent and fibrous areas, called the right and left trigones, which are located above the anterolateral and posteromedial commissures. There is an absence of any well-defined structure where the posterior leaflet attaches to the annulus. The intertrigonal distance and the height of the anterior leaflet are the two important clinical landmarks used when sizing annuloplasty rings in mitral valve repair procedures (Ender et al. 2011). There are two main papillary muscles, the anterolateral and the posteromedial, which give a secure foundation for the chordae tendineae that attach to both anterior and posterior leaflets. The anterolateral papillary muscle is large and usually has a single head, whereas the posteromedial papillary muscle is flat with two or more heads. The blood supply to the anterolateral papillary muscle is usually from the left anterior descending coronary artery and the circumflex coronary arteries, whereas the blood supply to the posteromedial papillary muscle is from a single source. This single vessel blood supply explains why this papillary muscle may rupture if there is a myocardial infarction involving the posterior descending coronary artery (Jain et al. 2013).

Pathophysiology The two main haemodynamic consequences of pathology affecting the mitral valve are mitral regurgitation and mitral stenosis.

Mitral regurgitation MR results in a backflow of blood into the left atrium through an incompetent valve, causing a volume overload. Over time, this results in an eccentric hypertrophy of the left ventricle and ultimately a reduction of left ventricular contractile function. There is also a gradual increase in left ventricular end-systolic volume and left atrial and pulmonary venous pressures, which eventually lead to congestive heart failure (McCarthy, Ring & Rana 2010). Mitral regurgitation (MR) can be caused by a variety of aetiologies. But before discussing its causes, it may be useful to look at Carpentier’s classification of mitral regurgitation (see Figure 8.1), which helps in formulating a management plan according to the underlying pathology (Carpentier 1983). Type 1 Normal leaflet motion ● Dilated cardiomyopathy, infective endocarditis Type 2 Excess leaflet motion ● Degenerative chordal rupture, myxomatous degeneration, papillary muscle rupture Type 3 Restricted leaflet motion » a.O Opening restricted – Rheumatic fever » a.C Closure restricted – Ischaemic cardiomyopathy

Figure 8.1: Pathological examples of Carpentier’s Classification (adapted from Carpentier 1983)

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MR can be acute or chronic. Acute MR is characterised by acute volume overload. It differs from the chronic volume overload of chronic MR in which atrial and ventricular enlargement, together with ventricular wall hypertrophy, can maintain cardiac output. Acute MR is not tolerated very well and it can cause haemodynamic compromise and acute pulmonary oedema, whereas chronic MR is well tolerated and patients generally present with symptoms before severe heart failure manifests (Mokadam, Stout & Verrier 2011). Common causes of acute MR include papillary muscle rupture (post myocardial infarction), infective endocarditis and chordal rupture. Common causes of chronic MR include rheumatic fever, myxomatous degeneration and secondary MR. MR may also be classified according to whether the leak across the mitral valve is a result of primary leaflet pathology or due to pathology that is not related to the leaflet (i.e. secondary MR). Secondary MR can be further divided into MR that is due to ischaemic heart disease and MR that is due to other causes, which can be termed functional MR. Functional MR is the result of gradual dilatation of the annular-ventricular apparatus with alterations in the left ventricular geometry that result in MR (Yamauchi et al. 2013).

Mitral stenosis Mitral stenosis is characterised by a restriction in flow from the left atrium to the left ventricle. This results in an increase in pressure in the left atrium and an increase in pulmonary vascular pressure, which eventually leads to pulmonary hypertension and right ventricular failure. The progress of mitral stenosis is slow and it usually takes a couple of decades before the patient becomes symptomatic (Mokadam, Stout & Verrier 2011). The most common cause of MS is rheumatic heart disease. Other causes include calcification of the mitral valve leaflets, mitral annular calcification, congenital MS, endomyocardial fibroelastosis, malignant carcinoid syndrome, systemic lupus erythematosus and Whipple disease, Fabry disease (rare genetic lysosomal disease) and rheumatoid arthritis (Shah & Sharma 2018). The pathological effects of rheumatic fever can take several decades to produce symptoms and signs of heart disease as a result of valve damage. Usually contracted at a young age, only around 50% of patients progress to rheumatic fever, which is more common in women than men (Carapetis et al. 2018). The pathophysiology of mitral stenosis may also manifest in some circumstances with an anatomically normal mitral valve but with a left atrial myxoma, cor triatum or a significant stenosis of a pulmonary vein. Mitral stenosis caused by an atrial myxoma can be hazardous, as the patient may have complete, or near complete, dynamic obstruction of the mitral valve orifice with severe haemodynamic compromise.

Signs and symptoms of mitral valve disease Patients with mitral valve disease can be asymptomatic initially, especially with mitral stenosis which has a latent period of many years. But some patients may develop symptoms of dyspnoea, palpitations, fatigue or weakness, orthopnoea and paroxysmal nocturnal dyspnoea. If left untreated, patients may develop pulmonary hypertension and subsequently right heart failure. Increased volume and pressure overload cause left atrial dilatation and atrial fibrillation, which

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may give rise to thrombus formation in the left atrial appendage and a risk of thromboembolism. Rarely, an enormously enlarged left atrium may cause pressure symptoms like dysphagia, hoarseness (Ortner’s syndrome) and left lung collapse (Sarin & Bhardwaj 2016).

Signs of mitral regurgitation Signs associated with MR are apical thrill, displaced apex beat, and a pansystolic or holosystolic murmur. This murmur is best heard over the mitral area, in expiration, in a lateral decubitus position, with the diaphragm of the stethoscope. The murmur may radiate to the left axilla. It is also worth knowing that the intensity of the murmur is a poor predictor of severity of mitral regurgitation. Further signs may be present if there is pulmonary hypertension, including a third heart sound, a diastolic flow murmur and evidence of a right ventricular heave on palpation of the chest (Bhattacharya & Sharma 2018).

Signs of mitral stenosis Various signs are present in mitral stenosis patients, such as low volume pulse (decreased filling of left ventricle), tapping but non-displaced apex beat in contrast to displaced apex beat in MR, and irregularly irregular pulse (atrial fibrillation). One of the most prominent signs may be the loud mitral component (M1) of the first heart sound (S1) which is made by the mitral and tricuspid valves closing. The sound is louder because of the increased force closing the mitral valve. Other signs include an opening snap (high-pitched additional sound heard after the A2 [aortic] component of the second heart sound [S2], which correlates to the forceful opening of the mitral valve). Back pressure through the left atrium and the pulmonary vasculature may result in pulmonary hypertension, and this can potentially result in a loud second heart sound (S2), due to the closure of the pulmonary valve under force. Classically, a mid-diastolic low-pitched rumbling murmur with presystolic accentuation is described after the opening snap is heard. The murmur is detected optimally at the apical area on the chest wall and is listened for with the bell of the stethoscope, with the patient tilted towards their left side. Advanced mitral stenosis may result in signs of right-sided heart failure such as raised jugular venous pressure, parasternal heave, hepatomegaly, ascites and (as previously mentioned) pulmonary hypertension. A further systemic sign includes a malar flush in the patient’s face that is the result of back pressure and a build-up of carbon dioxide resulting in vasodilatation (Chandrashekhar, Westaby & Narula 2009).

Investigations Radiographic signs that may be present in patients with mitral stenosis include a double atrial shadow and splaying of the carina secondary to a severely enlarged left atrium.

Echocardiography Echocardiography is the gold standard for diagnosing mitral valve pathology. It is performed using either the trans-thoracic echo or trans-oesophageal echo approach (Biswas & Yassin 2015). It is important not only to make the diagnosis of mitral valve disease, but also to assess the nature of the pathology and the magnitude of the problem. Vital information required to assess the

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severity of MR includes the regurgitant volume, the regurgitant fraction, the jet area percentage, the size of the vena contracta and the effective orifice area (see Table 8.1) (Baumgartner et al. 2009; Zoghbi et al. 2017). The criteria for ischaemic MR to be classified as severe, moderate or mild are different from those of degenerative MR (Vahanian et al. 2012). Important parameters to measure or assess mitral stenosis severity include effective orifice area, gradient across the valve and the degree of pulmonary hypertension (see Table 8.1) (Baumgartner et al., 2009; Zoghbi 2017).

Table 8.1: Assessing the severity of mitral regurgitation Parameters

Mild

Moderate

Severe

Regurgitant volume (ml)

60

Regurgitant fraction (%)

50

Jet area (% of LA*)

40%

Vena contracta

0.7

EROA* (cm2)

0.4

*LA – left atrium, EROA – effective regurgitant orifice area; table obtained from EAE/ASE guidelines (based on Baumgartner et al. 2009).

Table 8.2: Assessing the severity of mitral stenosis Parameters

Mild

Moderate

Severe

Mitral valve area (cm2)

>1.5

1.0–1.5

30%, who are undergoing CABG, have a Class IC indication for surgery. Recent data suggest comparable or even better results with replacement of the mitral valve by preserving the subvalvular apparatus in ischaemic mitral regurgitation patients (Acker et al. 2014). Moreover, mitral valve replacement is preferred in cases of acute severe MR, secondary to papillary muscle rupture. Although in expert hands repair can be performed there is little evidence regarding robust long-term durability.

Indications for surgery in mitral stenosis Percutaneous balloon mitral valvotomy (PBMV) is the first-line treatment for patients with symptomatic moderate to severe mitral stenosis if the valvular morphology is favourable, which can be determined by Abascal or Wilkins echocardiographic score (Wilkins et al. 1988). This scoring system was first described in 1990 to predict the morphological suitability of rheumatic mitral stenosis for PBMV. Surgery is recommended for scores >8–9. The scoring system has four main components which look at: (1) leaflet mobility; (2) leaflet thickening; (3) subvalvular thickening; and (4) leaflet calcification. PBMV is contraindicated in the presence of moderate mitral regurgitation and thrombus in left atrial appendage, and surgery is recommended for these patients.

Mitral valve endocarditis Endocarditis vegetations may affect valve motion and lead to MR. Vegetations more commonly embolise from the mitral than the aortic valve and may cause significant damage to their destination. Stroke is the most commonly observed clinical manifestation of embolisation. Vegetation growth on a leaflet may also cause leaflet perforation or can cause the rupture of one of the chordae tendineae (see Figure 8.2). Infective endocarditis on a prosthetic valve usually begins on the sewing cuff and generally tracks outside of the valvular apparatus leading to dehiscence of the sewing ring (Pham et al. 2012).

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A

B

C D

Figure 8.2: The infective endocarditis mitral valve A: Retrograde cardioplegia cannula B: Metal mitral retractor C: Mitral valve leaflets D: Left atrium

Surgical therapy Soon after the advent of cardiopulmonary bypass (CPB), the first female cardiac surgeon, Nina Starr Braunwald, performed the first mitral valve replacement in 1960 (Braunwald 1989), using a valve made of polyurethane with Teflon chordae tendineae. Since that time a wide range of approaches, techniques and strategies have developed.

Set-up for mitral valve surgery via median sternotomy The patient is anaesthetised and a central line and arterial line are inserted. A transoesophageal echocardiography (TOE) probe is placed and intra-operative assessment of the valve is performed by an experienced anaesthetist or specialised cardiologist. The patient is placed in a supine position and, following a median sternotomy, the pericardium is opened. Some surgeons’ preference is to ‘hitch up’ the right side of the pericardium in order to rotate the heart to the left and improve the view into the left atrium to see the valve. Systemic heparin is administered and the ascending aorta and both cavae are cannulated (bicaval venous cannulation). Antegrade and retrograde cardioplegia cannulae are placed in the ascending aorta and coronary sinus respectively. Retrograde cardioplegia is useful in this operation, as the retraction of the left atrium often pushes against the aortic root, making the aortic valve incompetent and rendering antegrade cardioplegia ineffective. The operating field is insufflated with CO2 to minimise air embolism at the end of the procedure.

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The patient is commonly cooled on bypass to a temperature of 32°C and ventilation can be switched off while on full cardiopulmonary bypass. The superior vena cava and inferior vena cava can be encircled with surgical tape and snared to achieve efficient venous drainage and reduce the risk of air being entrained from any intra-cardiac defect. The ascending aorta is crossclamped and the heart is arrested with cold/warm blood cardioplegia. The left atrium can be approached via Sondergaard’s groove or through the right atrium and the inter-atrial septum. The mitral valve is exposed with the help of a special mitral valve retractor. The specific mitral retractor (such as Cosgrove, Denver-Wells, Carpentier or Finochietto) can be chosen according to the surgeon’s preference. It is assessed for a suitable repair or replacement technique, depending on the pathology. Injecting saline into the left ventricle after the repair is completed can check mitral valve competency and this is known as static testing. The left atrium is closed with 3/0 or 4/0 prolene in a single or a double layer. De-airing is performed in a synchronised fashion by filling and massaging the heart while a valsalva manoeuvre raises intrapleural pressure and fills the left atrium with blood from the pulmonary veins. The aortic root vent is kept in place to siphon off air bubbles and the patient can be tilted, head down, to reduce the risk of cerebral air emboli. After de-airing, the left atrium incision is completely closed and the cross-clamp is removed. Filling the heart and sucking on the aortic root vent while the heart regains electrical activity or is paced achieves further de-airing. Normal ventilation is resumed and, after a period of reperfusion, the mitral valve repair or replacement is checked with TOE. The patient is weaned from CPB in the standard way. Decannulation is performed and protamine is administered. Haemostasis is secured and standard drainage tubes are placed. It is advisable to close the pericardium, especially in younger patients, to avoid resternotomy injuries in the future.

Surgical approaches to the mitral valve There are four main approaches to mitral valve surgery (Glower 2012): 1. Left atrial incision after developing Sondergaard’s groove, starting anterior and medial to the left superior pulmonary vein and extending inferiorly; this is the most commonly used approach 2. Trans-septal incision (bi-atrial approach) 3. Superior roof incision 4. Dubost incision (bi-atrial approach).

Mitral valve repair Mitral valve repair surgery is advantageous, as a repair is generally more durable than a tissue valve replacement and avoids the need for long-term anticoagulation. Surgeons have various options for set-up and approach. Reproducibility and durability of repair are crucial considerations for the patient, and cosmetic considerations are being considered more commonly in the modern era. However, equivalence to standard approaches is not proven in terms of standard of repair fashioned or long-term durability. Research still needs to be done to ascertain whether these procedures are equivalent to standard techniques or superior to a tissue valve replacement.

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The repair technique chosen will depend on information obtained from echocardiography and from the valve analysis performed by the surgeon intra-operatively once the valve has been exposed. Most valve repairs are carried out because the patient has a leaking mitral valve. The most successful and reliably fixable defect is a posterior leaflet prolapse. Anterior and bi-leaflet defects are less reliably repairable. In general terms, surgical strategies can be categorised as ‘respect’ or ‘resect’. Respect involves respecting the tissues and conserving the leaflet tissue, effecting the repair with the use of 5/0 Gore-Tex® (expanded polytetrafluoroethylene) artificial neochordae to reconstruct the broken or elongated chordae (see Figure 8.3). Resect involves excising leaflet tissue relating to the leak. This is, perhaps, reasonable where there is a relative excess area of tissue. Excess leaflet tissue billows like the spinnaker sail on a ship and it makes sense in this context to reduce the size of the ‘sail’ in order to reduce the strain on the chordae which are preventing future prolapse. Methods of refashioning the posterior leaflet include: a triangular resection, a quadrangular resection or a sliding plasty. Similar methods can be used to repair the anterior leaflet, by implanting an annuloplasty ring. This restores the annulus to a size that is appropriate to the size of the anterior leaflet. It makes sense that the annulus will have dilated over time when one considers that with mitral regurgitation there is a volume overload of the left ventricle that will have stretched the annulus. The annuloplasty ring is sized according to the height of the anterior leaflet or according to the inter-trigonal distance.

A

A B

Figure 8.3: The artificial neochordae with 5/0 Gore-Tex® stitch in situ, with placement of the annular sutures around the mitral annulus A: Neochordae 5/0 Gore-Tex® in situ B: Mitral valve leaflet

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Specific mitral valve repair techniques Annuloplasty Where the mitral valve annulus has dilated over time, as a result of volume overload of the left atrium, an annuloplasty band can be used to restore the optimal size of the annulus. In some instances of type 1 mitral regurgitation, this technique alone will be sufficient to restore competence of the mitral valve. Annuloplasty bands can be complete rings (such as the Edwards Physio ring) or incomplete rings (such as the Cosgrove band). The incomplete ring has a benefit in patients with a high risk of systolic anterior motion of the anterior leaflet of the mitral valve. There is also a benefit in patients having synchronous aortic valve surgery because this type of ring reduces the tension between the mitral and the aortic annulus having prosthetic material on both sides of the aorto-mitral curtain, which can contribute to mitral annuloplasty ring dehiscence.

Posterior leaflet prolapse The most common cause of posterior leaflet prolapse of the mitral valve is rupture of the chordae tendineae to the P2 component of the posterior leaflet. These chordae can be replaced with 5/0 Gore-Tex® or, if there is excess tissue present, a triangular resection can be performed in which a section of the posterior leaflet is excised as a triangular wedge with a competent leaflet area preserved (see Figure 8.4).

C

A

B

F

D

E

Figure 8.4: Mitral valve repair with a triangular resection of the posterior leaflet and the use of a Physio II annuloplasty ring and placement of vortex neochordae A: Mitral valve B: Sutures are in situ C: Triangular repair D: Mitral ring in situ E. Ring deployed in situ F: Sutures are knotted

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Additional Gore-Tex® neochordae can be implanted to further support the repair. The aim should be to have enough leaflet contact between the anterior and posterior leaflets when they close to have 8mm of coaptation. With excess posterior leaflet tissue and sizing the annuloplasty ring to the height of the anterior leaflet, this can involve pulling the posterior leaflet down into the left ventricle so that the coaptation point does not move anteriorly into the left ventricular outflow tract during systole, resulting in systolic anterior motion (SAM).

Anterior leaflet prolapse Efficacious and durable anterior leaflet prolapse repair is harder to achieve than repair of posterior leaflet prolapses. The mechanism is usually chordal rupture, and the ruptured chord is usually replaced with 5/0 Gore-Tex® neochordae. The height of the anterior leaflet at closure should be at the height of the annuloplasty ring. It is also possible, in some instances, to perform a triangular resection of the anterior leaflet. However, this procedure is not commonly undertaken.

Leaflet perforation In some cases of leaflet perforation, it is possible to patch the leaflet with a pericardial patch with the use of 5/0 prolene. Sometimes a perforation can also be closed primarily if there is sufficient healthy residual leaflet tissue.

Ischaemic mitral regurgitation Ischaemic MR is usually caused by an akinetic area of the base of the heart because of a myocardial infarction. As the ventricular wall remodels, the dimensions of the left ventricle enlarge and the relative distance between the posteromedial papillary muscle and the postero-lateral annulus (P2 to P3 area of the annulus) increases. The papillary muscle and the chordae generally stay the same length and this causes tethering of the posterior leaflet in the P2/P3 area. To correct this distortion, an ischaemic mitral regurgitation ring is used. This decreases the anterior-posterior dimensions of the annulus and downsizes the annulus in order to fashion a competent valve. Care must be taken to avoid mitral stenosis when downsizing the annulus. Recent papers have warned against the use of ischaemic mitral regurgitation rings, due to their disappointing durability by 12 months from the date of repair (Mick, Keshavamurthy & Gillinov 2015). As a result of this data, many surgeons would now consider valve replacement a superior technique to repair in this scenario.

Mitral valve replacement Mitral valve replacement is indicated when a durable repair cannot be fashioned. Options for valve replacement include mechanical and tissue valves. With the left atrium opened and on cardiopulmonary bypass, the cardiotomy suckers are positioned to return the drainage from the pulmonary veins. Some surgeons like to use an LV vent placed through the LV apex. However, this is not mandatory and runs the risk of LV bleeding at the end of the case, especially in older patients. It can be useful to place a retraction stitch in the anterior leaflet. This can be used to pull the anterior leaflet downwards and bring into view the annulus of the anterior leaflet to assist in positioning stitches. Pledgeted interrupted mattress sutures are favoured, as the tissue around the mitral annulus is relatively fragile.

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It is possible to position the sutures either with the pledget inside the ventricle so that the valve is supra-annular, or on the atrial side so that the valve is intra-annular. Surgeons commonly favour the intra-annular position for mechanical valves so that the valve leaflets are not restricted by tissue or the pledgets below the valve. The anterior leaflet is removed and the subvalvular apparatus is re-implanted into the annulus. There are various methods that can be used to re-implant the papillary muscles. Caution should be exercised to avoid narrowing the left ventricular outflow tract by overzealous reimplantation and drawing the papillary muscles too close to the annulus. The posterior leaflet should be preserved and is plicated up towards the annulus. Only where there is gross calcification and the valve ring cannot be seated securely to the annulus should any attempt be made to decalcify the posterior annulus. This is a hazardous undertaking and is one of the mechanisms of a posterior disruption of the mitral annulus, which carries a high risk of mortality. In the case of a mechanical valve replacement, the orientation can be anatomical or nonanatomical. Some types of mechanical valve can have their orientation altered after the valve ring has been implanted to optimise the position according to potential subvalvular structures that could obstruct the full opening of the valve. Some surgeons advocate orientating the leaflets in the non-anatomical position to avoid the influence of a venturi effect in the left ventricular outflow tract affecting leaflet opening and closing. Tissue valve orientation is planned to avoid a valve strut projecting into the left ventricular outflow tract and causing an obstruction. It is also important not to position a strut in such a way that it may project into the free wall of the ventricle and cause a free wall rupture. De-airing the heart thoroughly is crucial at the end of a mitral valve replacement.

Minimal access mitral valve surgery The patient is positioned supine, with the right arm out and the right chest elevated using supporting cushions. The 4th and 5th intercostal spaces are marked as well as the sternal notch and xiphoid process. Both groins are exposed and it is useful to mark the femoral arteries. Cardiopulmonary bypass is achieved with venous cannulae placed through the common femoral vein and the right internal jugular vein. Return to the aorta may be accomplished by femoral or subclavian cannulation. Cardioplegia can be administered through a specially designed endoballoon, which occludes the ascending aorta and allows cardioplegia to be administered. Alternatively, an endoclamp can be used and cardioplegia can be administered through the ascending aorta by careful direct cannulation. Cannulae are placed in the femoral artery and vein under TOE guidance. A cardioplegia delivery system (endoballoon) is placed in the ascending aorta through femoral arteries under TOE guidance. Cardiopulmonary bypass is initiated and ventilation is switched off. A thoracoscopic (8mm) camera is inserted into the right chest through a separate camera port. Under video-assisted vision, the pericardium is incised anterior to the phrenic nerve and retracted. The left atrium is visualised and the tissue plane is developed between the left atrium and right atrium medial and anterior to pulmonary veins. After confirming good position of the endoballoon, it is inflated and cardioplegia is delivered to achieve diastolic cardiac arrest. The left atrial incision is

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fashioned and the edges are retracted to visualise the mitral valve. Regurgitant cardioplegia through the aortic valve is easily delivered back to CPB with the help of cardiotomy suction tubes.

Ongoing developments in mitral valve intervention MitraClip MitraClip (Abbott Vascular™) is a transcatheter mitral valve repair technology based on the Alfieri stitch (edge to edge technique) in which the middle scallops of the posterior and anterior leaflets are sutured together to create a double orifice mitral valve. MitraClip has been compared with surgery in the EVEREST II trial. The results showed that freedom from combined outcome of death, mitral valve surgery, and MR severity greater than 2+ at 12 months was greater with surgery (73%) than with MitraClip (55%; p=0.0007) (Magruder et al. 2016). The trial failed to demonstrate efficacy equivalent to surgery for a diverse group of patients. Trials investigating the role of MitraClip in high-risk candidates with functional and ischaemic MR are ongoing.

NeoChord NeoChord is a transapically inserted instrument that is designed to attach a PTFE artificial chord to the defective leaflet and anchor the base of the chord to the apical muscle with a pledgeted suture. The device has been trialled in a small number of patients: 50% got to five years without requiring conventional surgery with variable degrees of residual MR (Kiefer et al. 2018).

Clinical scenario 1 A 30-year-old nulliparous lady underwent elective mitral valve surgery for severe mixed mitral disease. The preoperative transoesophageal echocardiogram indicated a strong likelihood of the valve being repairable. Intra-operatively the repair proved to be more difficult than anticipated. Despite three attempts at repairing the valve, moderate mitral regurgitation was still demonstrated on the intra-operative transoesophageal echocardiogram when attempting to wean the patient from cardiopulmonary bypass. Consequently, the decision was taken to proceed to mitral valve replacement. This was performed successfully, and the patient was discharged, having suffered no significant postoperative complications.

Discussion Patients listed to undergo mitral valve repair must be made aware that there is always a chance that the valve will not be amenable to repair. In such cases, in order to successfully treat the diseased valve, replacement of the valve with a prosthesis will be required. It is well recognised that mitral valve repair offers significant benefits over mitral valve replacement in terms of greater freedom from risk of mortality (both peri-operative and long-term), re-operation, endocarditis and left ventricular dysfunction. However, this is only true in the case of an effective and durable repair which achieves satisfactory resolution of the primary pathology (regurgitation/stenosis/ mixed pathology).

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The complicating factor in this case is the fact that the patient is a young female with no children. Usually at this age (30), most patients would be counselled to opt for mechanical prosthesis, due to the long-term durability of a mechanical valve and the increased likelihood of freedom from the need for repeat operation (in comparison to a tissue prosthesis). However, a mechanical prosthesis requires lifelong anticoagulation in the form of warfarin therapy, which is teratogenic and hence not suitable for a female patient who has not yet completed her family. In this situation, the patient may therefore opt for a tissue prosthesis in order to avoid the issue of anticoagulation. Unfortunately, a tissue prosthesis in the mitral position has a relatively short lifespan and the patient is likely to need a repeat valve replacement in approximately 10 years. The repeat procedure could then replace the tissue prosthesis with a mechanical prosthesis if the patient is satisfied that she has completed her family. All these issues must be carefully addressed in the preoperative period when initially discussing surgery, and they should be subsequently re-explored when undertaking the consent process immediately prior to surgery.

Clinical scenario 2 A 73-year-old male underwent an uneventful elective mitral valve repair for severe mitral regurgitation and was transferred to the cardiac intensive care unit where he demonstrated increasingly poor haemodynamics with evidence of persistent hypotension and a mildly elevated heart rate. The clinical picture did not improve with increasing doses of inotropes. An urgent transoesophageal echocardiogram revealed the presence of systolic anterior motion of the mitral valve. Once this issue had been identified, it was managed appropriately, and the patient made an uneventful postoperative recovery.

Discussion Systolic anterior motion of the mitral valve is a well-recognised phenomenon following mitral valve repair surgery. It occurs when the leaflets of the mitral valve are pulled anteriorly towards the interventricular septum and the left ventricular outflow tract. It is a dynamic problem, mainly occurring in systole and causing transient left ventricular outflow tract obstruction and mitral regurgitation. Conversely, in diastole, the leaflets resume their normal anatomical position and the diameter of the left ventricular outflow tract remains unaffected. When the degree of LV outflow tract and mitral regurgitation are severe enough, this will manifest clinically as haemodynamic instability secondary to decreased cardiac output. There are recognised anatomical factors, such as a small and hypertrophied left ventricle or the presence of excessive mitral valve tissue, which increase the likelihood of postoperative systolic anterior motion. In extreme cases, the severity of systolic anterior motion will warrant further surgical intervention. In the majority of patients, optimising important postoperative parameters (i.e. conservative management) is all that is required to sufficiently improve the haemodynamics. The mainstay of medical treatment of systolic anterior motion is adequate fluid resuscitation in order to maintain filling pressures, discontinuation of inotropic support, and reduction in the heart rate with the use of beta blockers. Haemodynamic instability following

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mitral valve repair surgery can be due to a number of causes, of which systolic anterior motion is just one. Assessment of physiological parameters (such as cardiac output studies), in conjunction with early transoesophageal echocardiogram, is vital in establishing the correct diagnosis and implementing an appropriate treatment plan.

Conclusion The mitral valve is a marvel of evolution – elegant in simplicity and function. Surgeons are privileged, in the current era, to be able to repair the common failings of the valve and (when necessary) replace it with a biological or mechanical valve. New technologies will add to the diversity of the repair approaches that can be employed. The number of patients eligible for treatment of the valve may increase as innovations remove some of the barriers created by the stress of conventional open-heart surgery for frail patients or those with significant comorbidities. Maintaining the health of the mitral valve is a key factor in reducing the prevalence of heart failure in patients with mitral valve disease.

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References Acker, M.A., Parides, M.K., Perrault, L.P., Moskowitz, A.J., Gelijns, A.C., Voisine, P., Smith, P.K., Hung, J.W., Blackstone, E.H., Puskas, J.D., Argenziano, M., Gammie, J.S., Mack, M., Ascheim, D.D., Bagiella, E., Moquete, E.G., Ferguson, T.B., Horvath, K.A., Geller, N.L., Miller, M.A., Woo, Y.J., D’Alessandro, D.A., Ailawadi, G., Dagenais, F., Gardner, T.J., O’Gara, P.T., Michler, R.E., Kron, I.L. & CTSN (2014). Mitral-valve repair versus replacement for severe ischemic mitral regurgitation. New England Journal of Medicine. 370(1), 23–32. Asano, R., Kajimoto, K., Oka, T., Sugiura, R., Okada, H., Kamishima, K., Hirata, T. & Sato, N.: investigators of the Acute Decompensated Heart Failure Syndromes (ATTEND) registry (2017). Association of New York Heart Association functional class IV symptoms at admission and clinical features with outcomes in patients hospitalized for acute heart failure syndromes. International Journal of Cardiology. https://www.ncbi.nlm.nih.gov/pubmed/28057363 (Last accessed 19.3.2019). Baumgartner, H., Hung, J., Bermejo, J., Chambers, J.B., Evangelista, A., Griffin, B.P., Lung, B., Otto, C.M., Pellikka, P.A. & Quiñones, M.; American Society of Echocardiography and The European Association of Echocardiography (2009). Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. Journal of the American Society of Echocardiography. 22(1), 1–23; quiz 101–102. Bhattacharya, P.T. & Sharma, S. (2018). Right Ventricular Hypertrophy. https://www.ncbi.nlm.nih.gov/books/NBK499876/ (Last accessed 19.3.2019). Biswas, A. & Yassin, M.H. (2015). Comparison between transthoracic and transesophageal echocardiogram in the diagnosis of endocarditis: A retrospective analysis. International Journal of Critical Illness and Injury Science. 5(2), 130–31. Braunwald, N.S. (1989). It will work: the first successful mitral valve replacement. Annals of Thoracic Surgery. 48(3), S1–3. Carapetis, J.R., Beaton, A., Cunningham, M.W., Guilherme, L., Karthikeyan, G., Mayosi, B.M., Sable, C., Steer, A., Wilson, N., Wyber, R. & Zühlke, L. (2018). Acute rheumatic fever and rheumatic heart disease. Nature Reviews Disease Primers. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5810582/pdf/nihms940295.pdf (Last accessed 19.3.2019). Carpentier, A. (1983). Cardiac valve surgery – the French correction. Journal of Thoracic Cardiovascular Surgery. 86(3), 323–37. Cavalcante, J.L., Lalude, O.O., Schoenhagen, P. & Lerakis, S. (2016). Cardiovascular magnetic resonance imaging for structural and valvular heart disease interventions. Journal of the American College of Cardiology: Cardiovascular Interventions. 9 (5), 399–425. Chandrashekhar, Y., Westaby, S. & Narula, J. (2009). Mitral stenosis. Lancet. 374 (9697), 1271–83. Ender, J., Eibel, S., Mukherjee, C., Mathioudakis, D., Borger, M.A., Jacobs, S., Mohr, F.W. & Falk, V. (2011). Prediction of the annuloplasty ring size in patients undergoing mitral valve repair using real-time three-dimensional transoesophageal echocardiography. European Heart Journal: Cardiac Imaging. 12(6), 445–53. Glower, D.D. (2012). Surgical approaches to mitral regurgitation. Journal of the American College of Cardiology. 60(15), 1315–22. Jain, S.K.A., Larsen, T.R., Darda, S., Saba, S. & David, S. (2013). A forgotten devil; Rupture of mitral valve papillary muscle. The American Journal of Case Reports. 14, 38–42. Kiefer, P., Meier, S., Noack, T., Borger, M.A., Ender, J., Hoyer, A., Mohr, F.W. & Seeburger, J. (2018). Good five-year durability of transapical beating heart off-pump mitral valve repair with neochordae. Annals of Thoracic Surgery. 106(2), 440–45. Magruder, J.T., Crawford, T.C., Grimm, J.C., Fredi, J.L. & Shah, A.S. (2016). Managing mitral regurgitation: focus on the MitraClip device. Medical Devices (Auckland). 9, 53–60. McCarthy, K.P., Ring, L. & Rana, B.S. (2010). Anatomy of the mitral valve: understanding the mitral valve complex in mitral regurgitation. European Heart Journal. 11 (10), https://academic.oup.com/ehjcimaging/article/11/10/i3/2397001 (Last accessed 19.3.2019). Mick, S.L., Keshavamurthy, S. & Gillinov, A.M. (2015). Mitral valve repair versus replacement. Annals of Cardiothoracic Surgery. 4(3), 230–37. Mokadam, N.A., Stout, K.K. & Verrier, E.D. (2011). Management of acute regurgitation in left-sided cardiac valves. Texas Heart Institute Journal. 38(1), 9–19.

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Pham, N., Zaitoun, H., Mohammed, T.L., DeLaPena-Almaguer, E., Martinez, F., Novaro, G.M. & Kirsch, J. (2012). Complications of aortic valve surgery: manifestations at CT and MR imaging. Radiographics. 32, 1873–92. Ramlawi, B. & Gammie, J.S. (2016). Mitral valve surgery: current minimally invasive and transcatheter options. Methodist DeBakey Cardiovascular Journal. 12(1), 20–26. Sarin, V. & Bhardwaj, B. (2016). Ortner’s syndrome – a rare cause of hoarseness: its importance to an otorhinolaryngologist. Iranian Journal of Otorhinolaryngology. 28(85), 163–67. Shah, SN. & Sharma, S. (2018). Mitral Stenosis. National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/books/NBK430742 (Last accessed 19.3.2019). Vahanian, A., Alfieri, O., Andreotti, F., Antunes, M.J., Barón-Esquivias, G., Baumgartner, H., Borger, M.A., Carrel, T.P., De Bonis, M., Evangelista, A., Falk, V., Lung, B., Lancellotti, P., Pierard, L., Price, S., Schäfers, H.J., Schuler, G., Stepinska, J., Swedberg, K., Takkenberg, J., Von Oppell, U.O., Windecker, S., Zamorano, J.L. & Zembala, M.; ESC Committee for Practice Guidelines (CPG); Joint Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology and The European Association for Cardiothoracic Surgery (EACTS) (2012). Guidelines on the management of valvular heart disease (version 2012): The Joint Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology (ESC) and the European Association for Cardiothoracic Surgery (EACTS). European Journal Cardiothoracic Surgery. 42(4), S1–44. Wilkins, G.T., Weyman, A.E., Abascal, V.M., Block, P.C. & Palacios, I.F. (1988) Percutaneous balloon dilatation of the mitral valve: an analysis of echocardiographic variables related to outcome and the mechanism of dilatation. British Heart Journal. 60(4), 299–308. Yamauchi, H., Feins, E.N., Vasilyev, N.V., Shimada, S., Zurakowski, D. & del Nido, P.J. (2013). Creation of nonischemic functional mitral regurgitation by annular dilation and nonplanar modification in a chronic in vivo swine model. Circulation. 128(11), 1–16. Zoghbi, W.A., Adams, D., Bonow, R.O., Enriquez-Sarano, M., Foster, E., Grayburn, P.A., Hahn, R.T., Han, Y., Hung, J., Lang, R.M., Little, S.H., Shah, D.J., Shernan, S., Thavendiranathan, P., Thomas, J.D. & Weissman, N.J. (2017). Recommendations for noninvasive evaluation of native valvular regurgitation: A report from the American Society of Echocardiography developed in collaboration with the Society for Cardiovascular Magnetic Resonance. Journal of the American Society of Echocardiography. 30(4), 303–71.

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9 Cardiopulmonary bypass Rob Bennett, Simon Colah, Lindsay Mclean and Andrew Wallhead

Introduction Cardiopulmonary bypass (CPB) is used to take over the function of the heart and lungs during cardiac surgery. CPB is achieved by diverting blood away from the right side of the heart to a heart lung machine (HLM) where the blood is oxygenated and processed before being returned to the patient. Bypassing the circulation to the heart and lungs provides a still, bloodless surgical field for the surgeon to operate on the heart. The heart lung machine is operated by a perfusionist, who uses the HLM and its components to regulate the patient’s blood pressure and temperature to optimise perfusion and oxygenation of the patient’s body during CPB. It is nearly 70 years since the first successful use of cardiopulmonary bypass. Surgical techniques may have fallen by the wayside, lost in the whirlwind development of cardiac surgery, nevertheless, the names of the innovators will live on in the history of heart surgery. Vision, knowledge and cooperation foster ideas that promote design, planning and financial backing. Innovative heart surgery is no different in its conception. A team of surgeons, anaesthetists, perfusionists and nursing staff will work together to develop a plan that is ideally rehearsed during a research phase. Each member of the team meticulously noting every minute step; each stitch, knot, infusion and cannula chosen explicitly.

History of cardiopulmonary bypass In 1812, while Napoleon’s army was caught up in one of the most disastrous campaigns in military history, Julien Jean César Legallois was developing innovative approaches to organ preservation with oxygenated blood. He correctly prophesied that the human body could be kept alive using artificial extracorporeal blood perfusion methods (Bruce Fye 1995) and these ideas gradually evolved over the next one hundred years. Toward the end of the 19th century, German physiologists experimented and progressed with early perfusion concepts. The first bubble oxygenator was produced by Von Schroeder in

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1882, while in 1885 in Leipzig, Dr Von Frey and Dr Gruber developed a closed perfusion circuit with a rotating screen oxygenator, heater and artificial pump, along with aortic and venous cannulation in a canine model (Von Frey & Gruber 1985). Cardiac surgery took a significant step on 9 September 1896. Dr Ludwig Rehn performed the first successful heart operation on a young man who had been almost fatally wounded by a stab wound to the right ventricle. Rehn performed the operation via the 4th intercostal space, placing the stitches during diastole (Werner et al. 2012). As the 20th century dawned, vascular suturing techniques were advanced by Alexis Carell and Matieu Jaboulay, leading to the first animal renal transplant in 1902 (Barker & Markmann 2013). In 1916 a young medical student, Jay Maclean, accidentally discovered the anticoagulant heparin while working with William J. Howell at Johns Hopkins Hospital in Baltimore USA, while experimenting with pro-coagulant compounds. However, heparin had many untoward side effects and it was not until the 1950s that it was synthesised in a form that was safe to be used during surgery (Shore-Lesserson & Gravelee 2000). Heart surgery was nevertheless regarded as off-limits by the surgical hierarchy in the early 20th century although there are reports of successful procedures during the First World War (Ashcroft 2014). The 1920s saw experimentation in early mitral commissurotomy by the surgeon Henry Souttar. In the 1930s John Gibbon and Carell published their separate ideas on the development of an extracorporeal device, but war slowed this development. Nevertheless, the Second World War provided an opportunity for new surgical heart procedures to be attempted. Between 1944 and 1945, Dr Dwight Harken performed 139 operations on the heart and great vessels to remove bullets and shrapnel. Thirteen of these operations were intra-cardiac; yet there was no mortality. This constituted a huge leap in the progress of heart surgery. Harken developed suturing and clamping techniques and aroused interest in the potential future of heart surgery. After the war, and a fellowship with Mr Tudor Edwards at the Brompton Hospital, he returned to Boston, where he developed the mitral valvotomy operation. There he found himself competing with Dr Charles P. Bailey in Philadelphia, who was trying to develop the mitral commissurotomy at the same time. Both procedures came under the umbrella of ‘closed heart surgery’ as they were performed without visualising the defects, but by inserting a finger or scalpel into the heart to open a stenosed mitral valve. An extracorporeal circulation was now needed to bypass the heart and lungs and provide oxygenated blood to the systemic circulation, to obtain a bloodless surgical field, to allow cardiac surgery to advance. After the war the race to develop a heart lung machine recommenced. On 5 April 1951, at the University of Minnesota, Dr Clarence Dennis used a heart lung machine and disc oxygenator for the first time in medical history to attempt to repair an atrial septal defect (ASD) in a six-year-old girl. The procedure was unsuccessful (The United States National Library of Medicine 1927–2003). On 3 July 1952, Dr Forrest Dodrill bypassed the left ventricle using ‘The Mechanical Heart’ Ventricular Assist Device (also known as the ‘Michigan Heart’) to perform the first mechanically

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assisted successful mitral valve repair on a 41-year-old male patient. The Dodrill-GMR heart project was a collaborative effort with General Motors Research Laboratory at Harper Hospital in Detroit, Michigan (The National Museum of American History 2018). Dr Bill Bigelow suggested immersing patients in an ice bath to protect the body during periods of cardiac arrest while operating. This reduced oxygen demand and increased the time available to repair cardiac defects. Early operations were thus performed with inflow occlusion and hypothermia without cardiopulmonary bypass (Rimmer, Fok & Bashir 2014). On 2 September 1952, at the University of Minnesota, Dr John Lewis repaired an ASD on a five-year-old girl using inflow occlusion under profound hypothermia. It took 2 hours and ten minutes to get the patient’s rectal temperature down to 28°C and 5.5 minutes to repair the ASD. She was rewarmed in a bath with water at 45°C for 35 minutes, by which time her temperature had risen to 36°C (Got 2005).

Cross circulation Dr Lewis’s friend and competitor at the University of Minnesota during this period was Dr Walton Lillehei. He expanded the new era in heart surgery to repair VSDs and TOF and other anomalies in 1954 using cross circulation (Taha & Shehatha 2014) (see Figure 9.1). Critics of the procedure noted that this was the first time in the history of surgery that a procedure could carry a 200% mortality (Got 2005).

Sigmamotor pump

Patient

Donor

Defect

Figure 9.1 Controlled cross circulation, developed by C.W. Lillehei, used on 26 March 1954

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After decades of work and research to develop a heart lung machine, Dr John Gibbon (with the help of IBM) successfully used total cardiopulmonary bypass (CPB) to repair an ASD on 6 May 1953 with a ‘Bypass time’ of 45 minutes. The device consisted of amongst other things, a roller pump and screen oxygenator. The patient, 18-year-old Celia Bavolek, lived for many years. Dr Gibbon’s wife Mary became the first perfusionist to operate the heart lung machine to bypass the heart and lungs to support a patient through a successful cardiac procedure. Unfortunately, Dr Gibbon never repeated this success and eventually gave up on the idea of heart surgery with CPB, while his peers continued successfully with the inflow occlusion method (Braile & de Godoy 2012). Gibbon’s heart lung machine (see Figure 9.2) was built with the support of IBM. It was a screen oxygenator in which venous blood was spread thinly over wire-supported screens in a reservoir with a high oxygen gas flow. Oxygenated blood would pool at the bottom of the reservoir and be pumped into the patient. It was not an efficient way of oxygenating blood.

Figure 9.2: The Mayo Gibbon heart lung machine. Further improvements to Gibbon’s machine were developed in the Kay and Cross machine (see Figure 9.3) (Cleveland Clinic) and Crafoord and Senning used a rotating disc oxygenator that provided less streaming and reduced the boundary layer but increased foaming and haemolysis (Stoney 2009). Modern heart surgery really took off with developments by Richard DeWall and Dr Walter Lillehei at the University of Minnesota, where the first clinically viable bubble oxygenator was produced. On 13 May 1955 Dr Lillehei began routine heart surgery using the new device. This changed the course of heart surgery and perfusion as we know it. The device was efficient, cheap, sterilisable and easy to assemble and, when combined with new developments in plastics, it became possible to mass-produce it (DeWall 2003). Interestingly, the main competition was between two of the great hospitals at this early stage in the history of CPB. The University of Minnesota Hospital and the Mayo Clinic were the only two hospitals in the world to use CPB. Competition became fierce as visitors from all over the world came to learn about heart surgery and the new bypass techniques. At the Mayo Clinic John Kirklin used the upgraded Mayo-Gibbon Machine, which was difficult to use and maintain. However, Kirklin’s success (with 9 out of 10 patients surviving) inspired teams from all over the world to start using CPB to support the circulation during heart surgery (Šušak et al. 2016).

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In 1955 Denis Melrose, at The Hammersmith, experimented with cardioplegia, a high potassium (K+) solution to stop and protect the heart. His mixture was unfortunately hyperosmolar and toxic. It took nearly 20 years for cardioplegia to gain popularity – when, in 1973, Gay and Ebert showed the protective effects of using potassium chloride cardioplegia to produce asystole to operate rather than ventricular fibrillation (Cordell 1995).

The Rygg bag Developments in bubble oxygenators by many manufacturers led to devices that were easy to use and disposable. The Rygg bag was one such device that was mainly used in Europe, with great success for many years. Bubble oxygenators eventually won the day (Hessel 2014). By 1976 it was estimated that 90% of cardiac surgery worldwide incorporated the use of a bubble oxygenator. There were many configurations of this type of oxygenator (Lim 2006).

Blood pumps Gibbon and Lillehei first used Sigmamotor peristaltic pumps to propel blood in the bypass circuit. The roller pump, which is common today, soon superseded these pumps.

Figure 9.3: The centrifugal blood pump, In 1973, the Biomedicus model 600 became the first disposable centrifugal pump for clinical use. The spinning cones create a negative pressure to draw blood into the inlet, creating a vortex. Centrifugal force imparts kinetic energy to the blood as the pump spins at 2000– 4000rpm, spinning the three inner cones (see Figure 9.3). The energy produced in the cone creates pressure and blood is forced out of the outlet. It is preload- and afterload-dependent, with an inverse relationship between flow and resistance at a constant rpm (Safi et al. 2005).

Haemodilution Bubble oxygenators and disc oxygenators were both used in the 1960s. However, until 1960, CPB circuit prime was composed of whole blood. At the time, this was thought to be the best thing. However, the use of whole blood proved to be a strain on blood banks and this led to haemodilution with crystalloid solutions. Remarkably, mortality rates dropped significantly. Blood usage and haemolysis were also reduced, improving capillary perfusion by the drop in viscosity.

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Advent of the membrane oxygenator It was noticed that membranes used for dialysis turned venous blood bright red so the search started for a highly permeable membrane material that could transfer oxygen and remove carbon dioxide. In 1956, Clowes et al. performed the first operation using a multi-layered ethyl-cellulose flat sheet membrane lung and later a Teflon membrane, which had hydrophobic properties to avoid the wettingout phenomenon seen after blood protein leaks into the micropores of the membrane material. However, CO2 removal was difficult due to the hydrophobic nature of the material. Problems with boundary layers and laminar flow caused oxygenation difficulties. Many designs were incorporated into the membranes to reduce the boundary layer and improve mixing by adding shims and cones to the blood path. Silicone was the next compound to be explored as a diffusion membrane material, but it was not until 1968 that the silicone membrane was developed by Kolobow and used primarily in long-term support. Its gas permeability properties were far better than Teflon, though early trials produced pinhole leaks. This problem was overcome by Burns et al. at the Hammersmith Hospital in 1969. In 1983 the Terumo Corporation produced the first microporous hollow-fibre membrane made from polypropylene (Lim 2006).

Landmark innovations since 1960 In 1960 Starr performed the first aortic valve replacement with a prosthetic valve; and later the same year D. Harken performed the first mitral prosthetic valve replacement (Russo et al. 2017).

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The age of heart transplantation was approaching. In the early 1960s Norman Shumway at Stanford in California established the technique for transplantation as it is performed today.

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In 1966 De Bakey implanted the first mechanical left ventricle assist device – left atrial to axillary artery. On the tenth day the device was explanted. The patient survived for more than five years.

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In 1967 the first successful heart transplant was performed by Christiaan Barnard in Cape Town, South Africa. Barnard had spent years working with, and learning from, the great heart surgeons in the USA. They were not happy that he received all the press and fame. However, within a year 100 transplants had been performed worldwide.

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Adrian Kantrowitz (famous for his work on developing the intra-aortic balloon pump) performed the second heart transplant in New York. The patient died within 24 hours.

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By 1968 most units had abandoned heart transplantation because of the problems of rejection, but Shumway, Reitz and colleagues persisted at Stanford

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In 1969 Denton Cooley, one of De Bakey’s brightest students, implanted a totally artificial heart into Haskell Karp, a 47-year-old man in severe LV failure. He was on the urgent transplant list but without a suitable donor. Cooley implanted the device, which lasted three days until Mr Karp was transplanted. Unfortunately, Mr Karp died the next day from multiple organ failure.

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In 1969 CABG surgery took a step forward with Favalaro at the Cleveland Clinic and Dudley Johnson in Milwaukee both advocating saphenous vein grafting using CPB. CPB allows improved vision by reducing the quantity of blood in the operating field.

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In 1972 Hill et al. performed the first successful extracorporeal membrane oxygenation (ECMO) in San Francisco on a motorcycle accident victim.

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Use of auto-transfusion devices developed during the Vietnam War.

The first reported successful use of ECMO in a case of neonatal respiratory failure took place in 1976.

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Blood cardioplegia became popular after the work done by Follette and Buckberg in 1978.

In 1981 Shumway and his team, including John Wallwork, developed the heart and lung transplantation operation using a combination of cyclosporine and azothioprine. (Sir Roy Calne at Cambridge had done much of the ground work with cyclosporine A in 1977.) Their first patient was successfully transplanted and survived for more than five years.

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In 1982, in Louisville, Kentucky, William De Vries implanted the Jarvik 7 into Barney Clark, a 61-year-old dentist. Robert Jarvik had worked with De Bakey in Texas but had his own ideas on a totally artificial heart. Barney Clark survived for 112 days.

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In 1983 Terumo produce the first microporous hollow-fibre membrane made from polypropylene. The Cobe membrane lung used the z- shaped sheet membrane configuration.

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In 1986 John Wallwork and Sir Roy Calne performed a triple heart-lung-liver bypass in a 35-year-old woman.

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The first domino transplant was performed in 1987 in Baltimore, USA.

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In 1991, in Houston, Texas, the first TCI Heartmate was implanted.

Landmark innovations in the 21st century Membrane oxygenators have now become standard in CPB, as many studies have shown the adverse effects of bubble oxygenators.

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The adverse effects of CPB were addressed in the 1990s, and perfusion technique has improved with:

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Better in-line blood gas monitoring

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Heparin bonded circuits that reduce complement activation and preserve platelets

Leukocyte filtration that is incorporated into the arterial filter as research into oxygen-free radicals has shown that they are generated from activated neutrophils

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Wide use of Trasylol as a tool to preserve platelets and reduce the inflammatory response to CPB

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The development of a new membrane material polymethylpentane that is used in ECMO

The development of the pulmonary thrombo-embolectomy operation using deep hypothermic circulatory arrest with cerebral perfusion

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The development of the Transmedics Organ Care System that enables transport of the heart ex vivo for human transplantation

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The manufacture of mini-bypass systems that reduce blood product use and haemodilution

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The use of portable mini-bypass circuits during the first donation after circulatory death heart retrievals, to restore and assess cardiac function, before organ transportation and transplantation at Papworth Hospital, Cambridge, UK.

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The use of bypass has been incorporated in other areas of surgery, including: ●●

Delivery of limb and hepatic anti-cancer agents

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Neurosurgery, to bypass and repair cerebral aneurysms

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Hyperthermia, in the treatment of human immunodeficiency virus

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Support during liver transplantation

Repair of aortic aneurysms and dissections. Looking ahead, cardiopulmonary bypass will continue to be an important tool in the advancement of heart surgery, transplantation and mechanical assist devices. The development of gene modification and stem cell engineering may change the treatment of heart disease, and transplanting bioengineered hearts may become commonplace. However, whatever the future holds, cardiopulmonary bypass, and the unsung skills of the perfusionists who operate them, will definitely be needed for many years to come.

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The heart and lung machine Gas and vacuum lines Patient monitoring Gas blender

Venous (cardiotomy) reservoir

Vaporiser In-line monitoring

Oxygenator

Heater-cooler

Heat exchanger Vents, suction and cardioplegia pumps Figure 9.4: A heart lung machine with a basic CPB circuit mounted and heater-cooler connected

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Cardiopulmonary bypass is used to divert blood away from the heart and lungs during cardiac surgery. CPB is achieved by connecting the patient to a disposable circuit consisting of polyvinyl chloride tubing, a reservoir, a heat exchanger and an oxygenator. The CPB circuit is mounted on a heart lung machine (HLM), which is a mobile base unit with several pumps in various configurations (see Figure 9.4).

Basic circuits A basic cardiopulmonary bypass system is shown in Figure 9.5. A venous cannula is placed at the inflow tract to the right atrium and an arterial cannula inserted into the aorta or femoral artery. The cannula is then connected to the CPB circuit which has been primed with fluid to remove all air from the circuit. Blood is diverted away from the right side of the heart into a venous cardiotomy reservoir. From the venous cardiotomy reservoir blood is pumped through a heat exchanger, for regulation of blood temperature, and oxygenator, where the blood is oxygenated and carbon dioxide removed, before being returned to the patient via the arterial cannula.

Tubing circuit The PVC tubing is used to connect the components of the CPB circuit. The internal diameter of the tubing used is determined by the required flow and pressure at different points in the circuit. The PVC tubing is often surface-coated with various materials, depending on the commercial supplier, to make the tubing more biocompatible to reduce the systemic inflammatory response caused by exposure of the blood to foreign surfaces. vent

suction device

cardioplegia cannula

venous cannula

aortic cannula

venous line arterial line arterial filter

hemoconcentrator

air

02

cardioplegia heat exchanger

oxygenator gas blender

HLM main pump

suction pump

vent pump

cardioplegia pump

Figure 9.5: Schematic of a basic cardiopulmonary bypass circuit.

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Venous cannulation For the majority of cardiac surgical procedures, a two- or three-stage venous cannula is used. The cannula is inserted through an incision in the right atrium and positioned so that the hole at the tip of the cannula drains blood from the inferior vena cava (IVC) and the remaining holes drain blood from the right atrium and the superior vena cava (SVC). For procedures that require the chambers of the heart to be opened, bicaval venous cannulation is used where separate single stage cannulas are placed in the SVC and IVC. Femoral venous cannulation can also be achieved by extending a long venous cannula from the femoral vein to the venae cavae. The size of cannula used depends on the size of the patient and the required flow rate.

Arterial cannulation The arterial cannula is connected to the CPB circuit to return oxygenated blood back to the patient. For routine cardiac surgery, the normal site for arterial cannulation is the ascending aorta. The size and type of arterial cannula used depends on the height and weight of the patient and the required flow rate.

Cardiotomy reservoir Venous blood from the patient drains into the cardiotomy reservoir, either by gravity or with the assistance of a vacuum applied to the reservoir. The cardiotomy reservoir can be either an open hard-shell reservoir or a closed soft-shell reservoir. Hard-shell reservoirs contain a polyester depth filter and a polyurethane de-foamer for the removal of debris and de-foaming of the blood. Suction blood and vent blood from the surgical field passes through the reservoir filters before being returned to the circulation. Some hard-shell reservoirs have two separate chambers, which allow the separation of activated suction blood. The level of fluid in the reservoir is maintained at a safe level during CPB to prevent accidental delivery of air to the patient. The cardiotomy reservoir is the point of access to the circuit where fluids and drugs can easily be added to the circulation.

Main pump head The main pump head pumps blood from the cardiotomy reservoir to the oxygenator and back to the patient, effectively taking over the function of the heart in the CPB circuit. The main pump head is either a roller (peristaltic) pump or a centrifugal pump, depending on local practice.

Oxygenator The oxygenator takes over the function of the lungs in the CPB circuit. Modern membrane oxygenators are made from bundles of microporous polypropylene hollow fibres. The gas phase is on the inside of the fibres and the blood flows through the bundle of fibres. Gas exchange (oxygen delivery and carbon dioxide removal) occurs through the micropores in the membrane. When blood comes into contact with the microporous membrane, a layer of serum proteins covers the micropores, forming a membrane and preventing a direct blood-gas interface. The surface area for gas exchange in artificial lungs is considerably smaller than that of the natural lung; 1.4–2.2m2 compared with an alveolar surface area of about 70–100m2 for the

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average adult human. The relative efficiency of the artificial lung, compared to a mammalian lung, is achieved by the continuous flow of gas across the gas exchange surface (similar in function to a bird lung or dinosaur lung) which allows for larger concentration gradients for oxygen (O2) and CO2 between the blood and gas phase. Also, the configuration of the hollowfibre bundle is designed to optimise the proximity of the blood to the gas exchange surface. After protracted use (>6 hours), plasma leakage can occur through the hollow-fibre micropores, causing a progressive reduction in gas exchange efficiency and eventually making it necessary to change the oxygenator. The gas supply to the membrane oxygenator is provided through a gas blender and flow meter which is connected to piped oxygen and air. The perfusionist optimises oxygenation and CO2 removal by regulating the fraction of oxygen in the gas mixture and flow rate (l/min) of the gas across the oxygenator membrane. An oxygen analyser is used to continuously measure the oxygen concentration in the gas supply line and alert the perfusionist in the event of an interruption in oxygen supply. A vaporiser can be incorporated into the gas supply to administer volatile anaesthetics, and waste gases can be scavenged from the oxygenator outlet port.

Heat exchanger The heat exchanger in the CPB circuit is used to regulate the patient’s body temperature. In most circuits the heat exchanger is integrated into the oxygenator unit and is connected to an external heater-cooler which pumps temperature-controlled water through the heat exchanger. Blood and water in the heat exchanger are separated by a polypropylene or stainless-steel surface which facilitates efficient heat transfer between the blood and water. The temperature of the water from the heater-cooler is precisely controlled, which allows careful regulation of the patient’s blood and body temperature.

Arterial line filter Arterial line filters are usually 40μM screen filters inserted in the arterial line, or integrated with the oxygenator/heat exchanger, to remove particulate micro-emboli and air emboli before the blood is returned to the patient.

Suckers and vents Suction pumps are used to salvage blood from the surgical field and return it to the circulation. Suction blood can either be returned directly to the circulation via the venous reservoir or collected in a separate reservoir and processed by a cell saver before being returned to the patient. Suction pumps are also used to actively vent excess blood from the heart and lungs during CPB.

Blood cardioplegia devices Cardioplegia solutions are used to stop the heart during cardiac surgery. This enables the surgeon to operate on a motionless heart and also reduces the metabolic demands of the heart. Most cardioplegia solutions contain a high concentration of potassium (to stop the heart) and are mixed with blood. Blood cardioplegia devices are used to mix the cardioplegia solution with blood from the CPB circuit, which is then warmed or cooled before being delivered to the heart.

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Electronic safety devices Numerous safety devices are connected to the bypass circuit to protect the patient and facilitate the smooth running of the CPB. The safety devices are interfaced with the control system of the heart lung machine and will either provide an audible alarm to alert the perfusionist or, if critical, will regulate the pump flow or stop the bypass. Bypass is terminated either by stopping the main pump head, when using a roller pump, or by applying an automatic servo-driven clamp to the arterial line when using a centrifugal pump.

Positive and negative pressures Pressures are measured at various critical points in the circuit. Excessive negative or positive pressures will either regulate or stop pump flow in the pump, generating the measured pressure.

Bubble sensors Bubble sensors are connected to tubing in the circuit and they detect bubble activity in the blood flowing through. Bubble sensors can alert the perfusionist to increased microbubble activity or they will stop the associated pump if a bubble of critical size is detected. An active bubble sensor should always be positioned on the arterial line to protect the patient from air embolus.

Level sensors Level sensors are applied to external surfaces in the CPB circuit and they detect the presence or absence of a fluid behind them. A level sensor on the cardiotomy reservoir is essential and will stop the bypass if the level in the reservoir falls below the set point.

Temperature alarms Temperature probes are used to measure patient blood temperature and will alert the perfusionist when set limits are exceeded.

Gas line monitoring An oxygen analyser is used to continuously measure the oxygen concentration in the gas supply line to the oxygenator and will alert the perfusionist in the event of an interruption in oxygen supply.

Monitoring during cardiopulmonary bypass Patient parameters (arterial blood pressure, central venous pressure, electrocardiogram and temperature are continuously monitored) and should be visible to the perfusionist during CPB. Urine output is also recorded at regular intervals.

Blood gas analysis Regular blood samples are taken during CPB and sent for blood gas and electrolyte analysis using a blood gas analyser. Various in-line monitoring systems are available, which can provide continuous blood gas and electrolyte measurement during CPB. The accuracy and range of in-line parameters measured varies by device, and the choice of system used in different departments is largely driven by cost.

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Anaesthetic gas monitoring The exhaust from the oxygenator can be connected to an anaesthetic monitor to provide an estimate of volatile anaesthetic gas delivery.

Cerebral saturation monitoring Regional oxygen saturation can be measured in the brain using near-infrared spectroscopy (NIRS). NIRS measures changes in oxygen supply and demand in the brain and a falling rSO2 index provides early warning of potential cerebral ischaemia. Measuring cerebral saturation during CPB is particularly useful when cerebral perfusion is compromised and it can also provide a surrogate indication of systemic perfusion quality.

Management of bypass Clinical perfusion practice can vary quite significantly between surgical units and individual perfusionists and is largely determined by the experience and knowledge of the perfusionist and local protocols. This section provides an overview of the basic principles common to the management of routine cardiopulmonary bypass and is not intended to provide a detailed discussion of individual perfusion practice.

Heart and lung machine preparation and circuit priming The heart lung machine (HLM) is thoroughly checked by the perfusionist before setting up the bypass circuit. The configuration of the bypass circuit used will depend on the type of surgical procedure, the height and weight of the patient and local protocols. Other factors (such as the patient having a metal allergy) could also influence the selection of various components within the circuit. When the bypass circuit has been mounted on the HLM, the integrity of the water to blood barrier in the circuit heat exchangers is checked – either by applying a pressure to the heat exchanger compartment and checking for a fall in pressure or by connecting the water from the heater-cooler and checking for water leaks. The CPB circuit is then primed with fluid, which is recirculated through the circuit, and all air is meticulously removed from the tubing and components by the perfusionist. The optimum solution for priming the CPB circuit remains a matter for debate but it is usually best to use a pure crystalloid solution, or a mixture of crystalloid and colloid solutions, depending on local protocol. Heparin is added to the prime solution, which is thought to bind to the charged surfaces of the CPB circuit and provide protection from thrombus formation when blood enters the system. Having primed and de-aired the circuit, the perfusionist sets the optimum occlusion of the roller pumps (main pump head, vent and suction pumps). Finally, the perfusionist checks that the gas supply is connected and that all safety devices (bubble detectors, pressure transducers, level sensors, temperature probes and gas line monitoring) are functioning and correctly allocated to the control system of the heart lung machine.

Pre-bypass check list The use of a pre-bypass checklist is advocated by the European Board of Cardiovascular Perfusion and the

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American Society of Extracorporeal Technology. Most perfusion departments use a tick-box checklist to ensure that all necessary preparation of the CPB system has been completed correctly and that back-up equipment is available if needed. An example of a pre-bypass checklist is shown in Figure 9.6. Pre Bypass Checklist Weight in kg:

Date weight recorded: Height (cm):

Name:

BSA (m2):

Address:

NHS No:

OXYGENATOR: Serial No:

Unit No:

DOB:

HEY No:

ARTERIAL FILTER: Serial No:

PRIME SOLUTION

TUBING CIRCUIT: Serial No:

HARTMANS 1000ml + HEPARIN 5000 units OR Specify

ARTERIAL CANNULA: Serial No: VENOUS CANNULA: Serial No: CORONARY CANNULA: Serial No: VENT CANNULA

VENT LEVEL SENSOR

APC BUBBLE SENSOR Prime Volume Administered

BCD SYSTEM: COMPANY/MODEL

Serial No:

SUCKER OCCLUSIONS: BLUE: YES / NO GREEN: YES / NO VENT / RED: YES / NO

Are all the pumps set to clockwise rotation? YES / NO CO2 FLUSH: YES / NO

VACUUM (IF USED): YES / NO

IABP SIZE:

WET TEST: YES / NO

ARTERIAL PUMP OCCLUSION: YES / NO

GAS SUPPLY: YES / NO

BCD PUMP OCCLUSION: YES / NO

PRIMED CIRCUIT: YES / NO

PUMP HEATER / COOLER CELL SAVER

BCD BUBBLE SENSOR: YES / NO

OXYGENATOR BUBBLE SENSOR: YES / NO

TIME ON:

EQUIPMENT RECORD

HEAT EXCHANGER: YES / NO

ISOFLURANE LEVEL (Adequate for case): YES / NO

OXYGENATOR / VENT LEVEL SENSOR: YES / NO

FR:

TIE TAGS to tubing YES / NO

TROLLEY

PACEMAKERS: YES / NO

CHECKED BY:

SOFTWARE / HARDWARE CONVERSION: YES / NO

ID Number:

PERFUSIONIST

Figure 9.6: Example of a pre-bypass checklist

Perfusion clinical record The perfusionist records all relevant information pertaining to a given CPB procedure in a clinical record document. The document should include a list of all disposable equipment used, with serial numbers and expiry dates, identification of hardware used, the pre-bypass checklist and a record of all events occurring during CPB; patient parameters (pressures, temperatures), perfusion parameters (flow rate, FiO2, gas flow), a record of fluid and drug administration and blood gas analysis results. Most perfusionists in the UK are non-prescribers and perfusion clinical records now incorporate a list of fluids and drugs commonly given during CPB, which a doctor can prescribe for the perfusionist to administer during CPB. Data acquisition systems are currently being introduced, which record data from the perfusion and patient monitoring systems to provide a comprehensive and accurate record of each CPB procedure.

Patient information Before bypass, the perfusionist reviews the patient’s notes and records any information that may be relevant to the conduct of the bypass. The perfusionist records the patient’s height and weight and calculates the patient’s body surface area (BSA). From the patient’s BSA, the perfusionist calculates the pump flows required to achieve an adequate flow index (equivalent to cardiac index) (l/minute/m2) to achieve adequate oxygen delivery to the patient at different temperatures. The calculated flow rates allow the perfusionist to select the size of venous and arterial cannulas needed to achieve adequate flows and act as a starting point for the pump flow required when first initiating CPB.

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Anticoagulation Blood contact with the large foreign surface area of the CPB circuit leads to the rapid activation of the coagulation cascade and the formation of clots. Adequate anticoagulation of the patient is therefore essential before CPB can be safely initiated. The most commonly used anticoagulant in cardiac surgery is heparin. Heparin works by binding to and activating antithrombin III (AT-III), which in turn inactivates thrombin and other proteases involved in blood clotting. The anticoagulant efficacy of heparin is measured by monitoring the activated clotting time (ACT) and an ACT between 400 and 480 seconds is normally enough for CPB. Heparin is usually administered at doses of 300–400 international units (iu) per kg body weight to achieve an adequate ACT; however, heparin resistance can occur. Heparin resistance is defined as the inability to raise the ACT to the expected level for a given dose and serum concentration of heparin. There are a few possible causes of heparin resistance; but the most likely reason for cardiac surgical patients to present with heparin resistance is prior exposure to heparin, which can cause a depletion of AT-III or a downregulation of AT-III activity. Heparin resistance is usually overcome by administering extra heparin until an adequate ACT for CPB can be achieved. However, if this is not successful then the patient can be given additional AT-III in fresh frozen plasma, or as an AT-III concentrate, to restore anticoagulation. After bypass, the anticoagulant effects of heparin are reversed by protamine which binds to and inactivates heparin.

Initiation of CPB The following sequence of events occurs before the patient can be put onto bypass: ●●

The arterio-venous recirculation loop from the CPB circuit is clamped and the lines divided.

●●

An ACT of >400 seconds is confirmed.

●●

The arterial line from the CPB circuit is connected to the arterial cannula. Care is taken to ensure that the connection is air-free by slowly bleeding back from the patient and/ or ‘coming up’ on the arterial line to displace air from the connection. When the arterial line is open to the circuit, the perfusionist checks the pressure in the arterial line to ensure the cannula has been correctly inserted. A lack of pulsatile ‘swing’ on the arterial line pressure suggests that the arterial line could have pierced the opposing wall of the aorta, been placed into a false lumen or might even have transfixed the aorta.



When the patency of the aortic cannula has been confirmed, the perfusionist can give rapid fluid transfusions if required. At this stage the perfusionist can displace the prime from the arterial line into the cardiotomy reservoir.

●●

●●

The venous cannula is connected to the venous line.

On instruction from the surgeon, the perfusionist initiates bypass; the arterial line is unclamped, and the main pump head slowly started to pump prime into the arterial cannula. The perfusionist observes the line pressure as the flow is increased; and when it is

●●

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established that there is no obstruction to arterial flow, the venous line is unclamped, and blood drained from the right side of the heart into the venous reservoir. If the venous drainage is adequate, the flow is increased until the target flow is reached and full CPB is established. If the venous return is not sufficient to establish full CPB, the perfusionist asks the surgeon to reposition the venous cannula until adequate drainage is achieved.

When first going onto CPB, the perfusionist observes the colour change in the venous blood as it passes through the circuit as a quick visual check that the oxygenator is functioning correctly.

Flows During cardiac surgery CPB takes over the function of the heart and lungs; the primary function of CPB is therefore to deliver enough oxygen to meet the patient’s oxygen demand. The oxygen demand of an anaesthetised and paralysed patient is determined primarily by their size, and by their temperature and depth of anaesthesia. During bypass, oxygen delivery is determined by the pump flow and the oxygen content of the blood. The oxygen-carrying capacity of the blood is largely determined by the haematocrit. Early clinical and experimental studies were undertaken to determine the flow index (equivalent to the cardiac index) needed to provide optimum oxygenation and tissue perfusion for an anaesthetised and paralysed patient at 37°C. It was found that patients needed a flow index in the region of 1.8–2.2l/min/m2. Before bypass, the perfusionist calculates the patient’s body surface area and determines the flows required to achieve an adequate flow index. During bypass, the perfusionist uses various measured parameters (pH, lactate and venous oxygen saturation; SvO2) to assess the adequacy of tissue perfusion and oxygenation. The perfusionist can then alter the blood flow and other conditions (haemocrit, temperature and depth of anaesthesia) to match oxygen delivery to demand. Goal-directed perfusion systems are currently becoming available to directly and accurately measure oxygen delivery and extraction; however, they have yet to be widely adopted.

Blood pressure management During bypass, the mean arterial pressure (MAP) is maintained between 50 and 80mmHg. The target pressure for a given procedure is determined by local protocol and the individual needs of the patient. As a rule, patients with cerebrovascular disease, carotid artery stenosis, renal dysfunction or chronic hypertension need higher perfusion pressures during CPB. The perfusionist controls the MAP either pharmacologically (using vasoconstrictor or vasodilator agents) or by altering the pump flow.

Haemodilution and fluid balance Some haemodilution is almost inevitable when first going onto bypass, due to prime from the circuit being delivered to the patient. Excessive haemodilution causes a precipitous fall in blood pressure, haematocrit and colloid oncotic pressure. The decrease in colloid

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oncotic pressure can cause rapid fluid loss from the circulation as water moves from the intravascular space into the extravascular compartment. Excess water in the interstitial and intracellular spaces can cause tissue oedema and organ dysfunction. The fall in haematocrit (HCT) caused by haemodilution reduces tissue oxygen supply and increases transfusion requirements. However, with careful consideration, the perfusionist can minimise the initial haemodilution of bypass by reducing the prime volume of the CPB circuit and using various blood conservation strategies. During bypass, the perfusionist needs to maintain a safe fluid level in the cardiotomy reservoir while providing optimum tissue perfusion and avoiding haemodilution. Throughout CPB, the perfusionist continuously monitors the patient’s volume status by observing and recording urine output, HCT, blood loss and fluid given. Excess fluid can be removed from overloaded patients by increasing pump flow and blood pressure or by administering diuretics to increase diuresis. If the rate of diuresis is not sufficient, a haemofilter can be connected to the CPB circuit. Haemofilters (or haemo-concentrators) contain bundles of hollow-fibre semipermeable membranes and can rapidly (at a rate of 30–50ml/min) remove large volumes of fluid (and electrolytes) from the circulation.

Volatile anaesthetics During CPB, volatile anaesthetics (isoflurane, desflurane, or sevoflurane) can be administered, via a vaporiser, into the gas supply to the oxygenator. Exhaust gases can be scavenged using the theatre anaesthetic gas scavenging system. An anaesthetic monitor can be used to measure the anaesthetic gas concentration in the exhaust from the oxygenator which has been shown to correlate reasonably well with arterial blood concentrations. The concentration of anaesthetic delivered will normally be prescribed by the anaesthetist. Volatile anaesthetics cause vasodilation and are sometimes used during bypass to manage blood pressure.

Blood gas management As mentioned earlier, the primary function of CPB is to take over the function of the heart and the lungs. The perfusionist therefore needs to maintain adequate blood pressure, optimise tissue oxygenation and make sure that CO2 is removed from the blood. Blood gas analysis is essential to ensure adequate tissue perfusion. Several parameters are measured either continuously (using in-line monitoring) or by taking regular blood samples for analysis. Table 9.1 (page 176) shows the parameters that are routinely measured during CPB and their normal ranges. The perfusionist interprets the blood gas and electrolyte results and acts as required to optimise patient perfusion. Blood oxygen and carbon dioxide concentrations are easily regulated by altering the fraction of oxygen and the sweep speed (l/min) of the gas supply to the membrane oxygenator. The acid-base status and serum lactate concentrations are very important to the perfusionist: an increasing metabolic acidosis and rising lactate indicate that the patient is underperfused and oxygen demand is exceeding oxygen delivery. The perfusionist can increase tissue perfusion and oxygenation by increasing the pump flow rate and, if necessary, increasing the

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haematocrit. Alternatively, the patient’s metabolic demand could be decreased by reducing the patient’s temperature or increasing the depth of anaesthesia.

Table 9.1: Arterial blood gas and electrolyte parameters routinely measured during CPB Parameter

Normal range

pH

7.35–7.45

PaO2 (Partial pressure of O2)

10.5–13.5kPa (70–100mmHg)

PaCO2 (Partial pressure of CO2)

4.7–6.0kPa (35–45mmHg)

HCO3 (bicarbonate)

22–28mmol/litre

BE (base excess)

-2 to +2mmol/litre

SaO2 (arterial oxygen saturation)

92–98%

Haemoglobin (Hb)

Males 130–180g/litre, Females 115–165g/litre

Haematocrit (HCT)

Males 40–54%, Females 37–47%

Na (sodium)

135–145 mmol/litre

Cl (Chloride)

98–106mmol/litre

K (potassium)

3.5–5.3mmol/litre

Ca2 (calcium)

2.2–2.6mmol/litre

Mg2

0.7–1.0mmol/litre

–

+

–

+

+

+

Lactate

0.5–2.2mmol/litre

Glucose

4.0–6.0mmol/litre

Cardioplegia As mentioned earlier, cardioplegia solutions are infused into the heart to cause a rapid diastolic arrest which provides a motionless heart for the surgeon to operate on and reduces the metabolic demands of the heart. The constituents of cardioplegia solutions vary considerably; however, most solutions contain a high concentration of potassium to stop the heart and are mixed with blood to provide oxygen and physiological buffering to the heart. Blood cardioplegia devices are used to mix the cardioplegia solution with blood from the CPB circuit, which is then warmed or cooled before being delivered to the heart. There are a few different routes for infusing cardioplegia into the heart and the method used depends on the operation being performed and the surgeon’s preference. Cardioplegia infusion can be either antegrade or retrograde. Antegrade cardioplegia is usually delivered into the aortic root after the aortic cross-clamp has been applied. For surgery that requires the aorta to be opened, antegrade cardioplegia is delivered directly into the coronary ostia via balloon-tipped or hand-held cannulas. Retrograde cardioplegia is delivered via a balloon-tipped cannula placed in the coronary sinus. Pressures are carefully monitored during cardioplegia delivery to ensure that cardioplegia is being adequately delivered and to avoid potential damage to myocardial or vascular tissue.

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Strategies for myocardial protection using cardioplegia vary considerably between centres and individual surgeons; however, most approaches use an initial high dose potassium solution to stop the heart. This is then ‘topped up’ periodically with a cardioplegia solution containing a lower potassium concentration. ‘Topping up’ cardioplegia maintains diastolic arrest, replenishes the supply of oxygen and substrates to the myocardium, and buffers acidosis. Alternative cardioplegia techniques include the use of crystalloid cardioplegia (with no blood) and, more recently, the use of single-shot solutions which can provide diastolic arrest and myocardial protection for a few hours without the need for ‘topping up’.

Venting Vent suction is used to actively aspirate excess blood from the heart and lungs to maintain a bloodless operating field and avoid distension of the cardiac chambers. Excess blood in the heart and lungs during CPB can be caused by inadequate venous drainage and collateral blood flow. Common sites for venting include the main pulmonary artery, the superior pulmonary vein, the left atrium, the left ventricle, and the aortic root. Vent suction is also used to actively remove air from the heart during de-airing procedures. Under-pressure release valves are commonly positioned in vent lines to prevent excessive negative pressures from pulling air into the vented vessel or cardiac chamber.

Handling of suction blood During cardiac surgery, shed blood from the operative field can be salvaged and returned to the circulation using pump suckers. However, when blood leaves the vessels and is exposed to air and the non-vascular surfaces within the chest it becomes ‘activated’. Activated suction blood has been shown to cause platelet activation and thrombin generation and contains numerous proinflammatory mediators, activated leucocytes, plasma-free haemoglobin, endotoxin, vasoactive agents and significant amounts of particulate contamination (such as fat, bone and cellular debris). Returning suction blood to the circulation has been shown to increase the systemic inflammatory response and adversely affect coagulation and vascular, pulmonary, brain, kidney and liver function. It is therefore generally agreed that suction blood is ‘nasty stuff’ and when possible should not be returned to the circulation. There are several strategies that can be employed to reduce the amount of suction blood returned to the patient – for example, improving haemostasis throughout the operation, to minimise the amount of shed blood, and using the cell saver sucker instead of the pump suckers. Alternatively, the perfusionist can divert the suction blood to a separate reservoir. Some cardiotomy reservoirs have an integral reservoir specifically designed to facilitate the separation of suction blood. Separated suction blood can either be discarded or sent to a cell saver for processing before being returned to the patient. If blood loss is excessive, it is generally necessary to return the suction blood directly back into the circulation to avoid the need for haemodilution or the excessive removal of clotting factors by cell saver processing.

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CO2 insufflation

Blowing CO2 into the chest cavity (CO2 insufflation) is sometimes used during open heart procedures to replace the air in the chest cavity with CO2. Any gas drawn into the open chambers of the heart during the operation is then mostly CO2 which reduces the volume of gaseous emboli being delivered to the patient because CO2 is more soluble in blood than the 78% nitrogen in room air. The perfusionist needs to be aware that CO2 insufflation is being used to prevent the, often unpredictable, hypercapnia that can develop due to excess absorption of CO2 into the blood. It is also important to avoid collections of stagnant blood when using CO2 insufflation because it is thought that the acidity of hypercapnic blood reduces the efficacy of heparin and can lead to clot formation.

Temperature The perfusionist carefully controls the patient’s body temperature during CPB by regulating the temperature of the water supply to the heat exchanger. Reducing the patient’s body temperature protects the organs from ischaemic insult by reducing the patient’s metabolic rate and oxygen demand. It is estimated that every 1-degree reduction in body temperature reduces the metabolic rate by 7%. Special care is taken, when rewarming the patient, to ensure adequate and even rewarming and to avoid over-heating the patient. Excessive warming can cause serious harm to the patient due to the reduced solubility of gases in the blood, causing increased gaseous microemboli or even protein denaturation at higher temperatures.

Circulatory arrest and cerebral perfusion Deep hypothermic circulatory arrest (DHCA) is used during surgical procedures that require the circulation to be completely stopped – for example, repair of aortic dissections involving the aortic arch, removal of large tumours invading the vasculature, paediatric congenital repairs and some neurosurgical procedures. Deep hypothermia (17–18°C) dramatically reduces cellular metabolic rate and oxygen demand which protects the organs, especially the brain, from ischaemic injury during the period of circulatory arrest. Accurate temperature monitoring is essential for procedures requiring DHCA to ensure adequate and uniform cooling of the patient. A rectal or bladder temperature probe is used to measure core body temperature and a skin probe can be used to measure peripheral temperature. Tympanic or nasopharyngeal temperature provides an indication of brain temperature. Immediately, on initiation of CPB, the perfusionist begins cooling the patient. During cooling and during circulatory arrest, ice packs are normally placed around the patient’s head to facilitate and maintain cerebral cooling. When the target core temperature has been reached and maintained, the circulation is stopped, and the patient’s blood is partially drained into the cardiotomy reservoir. During circulatory arrest, the blood in the CPB circuit is continuously recirculated within the circuit to prevent stagnation and clotting. It is not known exactly how long the human brain can tolerate DHCA before irreversible neurological damage starts to occur. There is considerable variation between individuals, with some patients tolerating DHCA for more than 60 minutes while other patients sustain neurological injury after less than 20 minutes. However, it should be noted that there are many other factors

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involved. It may not be circulatory arrest per se that contributes to neurological injury during DHCA procedures – for example, cooling and warming the patient (and the consequently protracted bypass time) or emboli released from the surgical site could also be implicated. In addition to using deep hypothermia to protect the brain during periods of circulatory arrest, the brain can be further protected by using isolated cerebral perfusion when the circulation is stopped. Cerebral perfusion can be either retrograde or antegrade and it is delivered either continuously or intermittently during circulatory arrest. Retrograde cerebral perfusion is delivered, via a bridge in the perfusion circuit, to a snared venous cannula in the superior vena cava and blood is returned to the circuit using pump suckers in the aorta. Antegrade cerebral perfusion can be delivered via a few different cannulation sites and techniques. Bilateral antegrade cerebral perfusion can be provided by balloon-tipped cannulae in the innominate artery and left carotid artery, or, with the aorta clamped at the aortic root and proximal to the left subclavian artery, via a vascular graft on the right subclavian artery or through a side arm on the aortic vascular graft. Hemi-cranial cerebral perfusion can be achieved via a vascular graft on the right subclavian artery with the innominate artery clamped. Blood is returned to the circuit during antegrade cerebral perfusion through the normal venous cannula. As a rule of thumb, the minimum flow needed to adequately perfuse the human brain at 17°C is about 10–20ml/kg body weight/minute. Cerebral near-infrared spectroscopy monitoring can provide a useful indication of cerebral oxygen delivery during cerebral perfusion and can be used to empirically optimise cerebral perfusion. Using cerebral perfusion to protect the brain allows a reduced need for systemic hypothermia (22–25°C) because the other organs of the body are less susceptible to ischaemia. When the surgical procedure is complete, the patient can be put back onto full bypass and rewarmed. Rewarming from DHCA can take some time and the perfusionist must take care to avoid excessive temperature gradients and to ensure even heat distribution between the core and periphery.

Near-infrared spectroscopy Near-infrared spectroscopy can be used to measure regional oxygen saturation in the brain. A falling rSO2 index provides early warning of potential cerebral ischaemia and the perfusionist can implement a number of strategies to improve cerebral perfusion and rSO2 (see Table 9.2).

Table 9.2: Interventional strategies to increase cerebral regional oxygen saturation during CPB If the haematocrit 15KPa (112mmHg)), causes an increase in oxygen free radical production, contraction of the coronary arteries (with a decrease in coronary artery blood flow and increased coronary vascular resistance), contraction of coronary artery grafts and an increase in systemic vascular resistance and should be avoided when possible. It is not uncommon for cardiac anaesthetists to hyperoxygenate patients post-CPB, despite a lack of evidence for a beneficial effect of excess oxygen and growing evidence to suggest that hyperoxygenation has adverse effects. Nevertheless, it is believed that a degree of hyperoxygenation can offer an element of protection from ischaemic injury during CPB in patients with a low haematocrit.

Methods of reducing the impact of CPB A number of measures can be taken to reduce the adverse effects of CPB:

Reducing the overall foreign surface area of the CPB circuit by: moving the heart lung machine closer to the surgical field to reduce the length of the arterial and venous lines; using vacuum-assisted venous drainage to reduce the length and internal diameter of the venous line; selecting an oxygenator with the smallest surface area needed to meet the demands of the patient; or using a mini-bypass circuit

●●

Reducing haemodilution and the need for homologous blood transfusion

●●

Using circuits with a biocompatible coating

●●

Reducing the blood-air interface in the CPB circuit by using a soft-shell cardiotomy reservoir or even removing the venous cardiotomy reservoir altogether by using a mini-bypass circuit

●●

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●●

Where possible, separating the activated cardiotomy suction blood from the circulation

●●

Reducing RBC damage by minimising the use of pump suction and optimising pump occlusions.

Reducing haemodilution Delivering a large volume of prime to the patient, when they first go onto bypass, causes an immediate haemodilution which causes a fall in blood pressure and a significant reduction in haematocrit and colloid osmotic pressure. The fall in haematocrit causes a precipitous reduction in oxygen delivery and can trigger the need for homologous blood transfusion. The rapid reduction in colloid osmotic pressure can cause loss of fluid into the interstitial spaces (‘third spacing’). Accumulation of fluid in the tissues causes oedema, which can cause organ dysfunction, and is further exacerbated by the need for the perfusionist to replace lost volume. Reducing the volume of prime solution delivered to the patient can therefore offer significant benefit by reducing haemodilution, which preserves the haematocrit and the colloid osmotic pressure, thus increasing oxygen delivery, reducing the need for blood transfusions and maintaining a more physiological colloid osmotic balance between the blood and tissues. There are two different strategies that can be used by the perfusionist to effectively reduce the volume of prime delivered to the patient: ●●

Reducing the volume of the CPB circuit

●●

Autologous prime displacement.

Reducing the volume of the CPB circuit The total volume of the CPB circuit can be reduced by: positioning the heart lung machine closer to the operating field to reduce the length of the lines; using vacuum-assisted venous drainage to reduce the length and internal diameter of the venous line; and selecting the smallest oxygenator and reservoir needed to meet the demands of the patient.

Autologous prime displacement Autologous prime displacement uses the patient’s own blood to displace the prime solution in the CPB circuit before initiation of bypass. A few different techniques can be employed to displace the prime in the circuit with the patient’s own blood. When the arterial line is connected, and the patient is haemodynamically stable, blood from the aorta can be used to retrograde displace prime from the arterial line into a separate reservoir or sterile bag. Similarly, the prime in the venous line can be displaced by draining from the right atrium and displacing the prime into a reservoir or bag. Another method, which can facilitate almost complete displacement of the prime before going onto bypass is rapid antegrade prime displacement. Rapid antegrade prime displacement is achieved by clamping the arterial line, opening the venous line and using the main pump head to rapidly displace the prime into a separate cardiotomy reservoir. When much of the prime has been displaced, the line to the cardiotomy is clamped and the arterial line opened to establish full CPB. Using this method can significantly reduce haemodilution of the patient and is further facilitated by using a reduced volume circuit.

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Mini-bypass Conventional cardiopulmonary bypass has been around for decades. It is associated with complications such as end-organ dysfunction, coagulopathy, haemodilution, bleeding and blood transfusion. However, there is an alternative method, called minimally invasive Extracorporeal Membrane Oxygenation (ECMO) circulation. This particular practice has been shown to have less deleterious effects compared to the conventional practice. However, world utilisation of ECMO is still very low. It is mainly used for coronary artery bypass surgery and aortic valve replacement with and without grafts. The management of this technique is very different from that of conventional bypass. Firstly, there is no hard-shell reservoir. This can be replaced with a soft-shell bag that is clamped off from the circuit and used to add or take off circulatory volume. Some centres do not use the soft-shell bag; they simply run the system in an ECMO style, with a venous line leaving the patient, which goes to a centrifugal pump, an oxygenator and then returns to the ascending aorta. As it is a closed circuit, there is a lot of concern about air entering the venous line. It is paramount that air does not enter the system. To avoid this, the venous cannulation site can be secured with two sutures rather than one. If air still enters the venous line, there are detectors and air removal pumps that can remove the air before it travels further around the circuit. The MiECC can incorporate more safety features than a traditional bypass system. Due to the low priming volumes and biocompatibility coating of the system, research has shown that MiECC systems offer more benefits than conventional circuits. The haemoglobin is maintained at a higher level, fewer transfusions occur, there is a reduced need for platelets and fresh frozen plasma, inflammatory markers are reduced, atrial fibrillation is reduced, ventilation times are shortened and total hospital length of stay has also been shown to be shorter. However, before embarking on the development of a mini-bypass strategy, it is advisable to gain some hands-on experience in the set-up and management of a minimised circuit.

Critical incidents related to CPB Effective safety monitoring has made modern cardiopulmonary bypass an extremely safe practice and life-threatening events caused by perfusion-related incidents are now rare. However, events can occur that can have serious consequences for the patient and it is important that the perfusionist and other members of the surgical team act quickly and effectively to minimise harm to the patient.

Gross air embolus Pumping gross air into the patient is the perfusionist’s worst nightmare; this is often fatal or, at best, will leave the patient with a severe neurological deficit. Gross air can potentially be delivered to the patient through the arterial cannula if the cardiotomy reservoir is emptied and safety devices (perfusionist, level sensor and bubble detector) have failed to stop the main pump head or clamp the arterial line before air reaches the patient. The following steps should be taken immediately: ●●

Stop the main pump head.

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Put the patient is head down (Trendelenburg position).

Commence manual compression of the carotid arteries to prevent air entering the cerebral vasculature.

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If using a roller pump, it must be put into reverse and air sucked from the aorta.

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If an aortic vent is in situ, it must be turned on to suck air from the aorta.

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The surgeon uses manual compressions of the heart and aorta to help with de-airing.

Retrograde perfusion of the cerebral vessels can be attempted by connecting the arterial line to a venous cannula inserted into the superior vena cava. Any air in the cerebral vessels is flushed out through the aorta.

●●

If full CPB can be re-established, rapid cooling of the patient should be considered, to reduce cerebral metabolic demands and facilitate further de-airing of the brain while under deep hypothermic circulatory arrest.

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Other potential sources of gross air embolus during CPB include: a vent sucker being inserted in the pump boot the wrong way round, causing air to be blown into the vented compartment rather than blood to be sucked out; pressurisation of a sealed cardiotomy reservoir, causing air to be forced up the venous line (this can occur when using vacuum-assisted venous drainage if the vacuum is turned off and the suckers are on). Appropriate measures (big syringe, venting) should be taken to remove the air from the affected area.

Failing oxygenator The membrane oxygenators used during routine cardiac surgery are rated to function efficiently for at least six hours. A decrease in the gas exchange efficiency of the oxygenator (CO2 removal and oxygenation) is a sign of impending oxygenator failure. Failure of the oxygenator is caused by an accumulation of condensation and plasma in the gas phase which impedes gas exchange. Oxygenator failure is a gradual process and usually does not require the oxygenator to be changed. However, if necessary, the perfusionist can quickly replace the oxygenator with a preprimed oxygenator. If the tubing circuit used includes a diamond configuration, the perfusionist can change the oxygenator without having to come off bypass. If the circuit does not have a diamond, then bypass will be terminated briefly to change the oxygenator.

Oxygenator ‘clotting off’ The first signs of clot formation in the oxygenator are an increase in the pressure difference across the oxygenator (pre- and post-oxygenator pressures) and the appearance of clots at the ends of the membrane. Clot formation in the oxygenator is a serious complication and usually requires the oxygenator to be changed. The most likely reason for an oxygenator clotting off is inadequate or ineffective anticoagulation or the inappropriate reversal of heparin by the administration of protamine during CPB. Anticoagulation should be corrected immediately and, if necessary, the oxygenator and any other components of the circuit containing clots should be replaced. This will usually require bypass to be briefly interrupted.

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Heater-cooler water contamination The water in heater-cooler units (HCUs) is a potential source of microbial contamination. Strict cleaning regimes are used to reduce, as far as possible, microbial growth in heater-coolers and regular samples are taken from the water and air outlets for microbiological testing. Care is taken in the operating theatre to ensure that the patient is not exposed to any risk of infection from the heater-cooler unit. During 2014 and 2015, several cases of endocarditis caused by Mycobacterium chimaera were reported in patients following cardiac surgery in Switzerland, Germany and the Netherlands (Kohler et al. 2015; Sax et al. 2015). An investigation in Switzerland (Sax et al. 2015) found that M. chimaera isolates in ICUs were closely related to the strains of M. chimaera isolated from patients and concluded that the aerosolisation of contaminated water from the HCU was the most likely source of infection. Subsequent investigations around the world have identified numerous probable cases of M. chimaera infection associated with cardiopulmonary bypass and have identified widespread contamination of HCUs with M. chimaera. Consequently, health agencies around the world have issued strict guidelines on the use, decontamination and microbiological monitoring of HCUs used in cardiac surgery – see, for example, Public Health England Guidelines (Gov.UK, 2017).

Role of cell salvage in cardiac surgery Reinfusion bag

Anticoagulant

Collection reservoir

Saline wash

Centrifuge bowl Waste bag

Figure 9.7: Cell saver

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Cell savers are frequently used in cardiac surgery as part of a blood conservation strategy. During surgery, blood is mixed with an anticoagulant at the tip of a modified suction catheter which is connected to a vacuumed reservoir. When enough volume has been collected in the reservoir, the anticoagulated blood is transferred to a centrifuge bowl where it is spun and washed with normal saline to separate the red blood cells from waste products (fat, debris, anticoagulant, plasma, platelets, leukocytes and free plasma haemoglobin). The concentrated red blood cells are then transferred to a collection bag for re-infusion to the patient (see Figure 9.7). Concentrated RBCs collected during surgery can either be returned directly into the bypass circuit during CPB or kept for re-infusion after bypass. Where the perfusion strategy includes the separation of activated suction blood, the separated blood can be transferred to the cell saver for processing during CPB; however, caution should be exercised as excessive processing of suction blood will remove clotting factors from the circulation. After the termination of CPB, when the arterial cannula has been removed, any residual blood in the CPB circuit can be flushed through to the cell saver for processing.

Intra-aortic balloon pump The intra-aortic balloon pump (IABP) is designed to assist the heart using intra-aortic balloon counterpulsation, increasing the myocardial oxygen supply and decreasing myocardial oxygen demand. A balloon catheter is inserted, via the femoral artery, into the aorta with the tip of the catheter positioned just distal to the left subclavian artery. The length and volume (30–50cc) of the catheter used is dictated by the size of the patient. The patient’s ECG and blood pressure are measured on the IABP console and used to time the inflation and deflation of the IABP catheter. Inflation of the balloon catheter (with helium) occurs on the dicrotic notch, when the aortic valve closes, which increases blood pressure in the aorta (the augmented pressure) and consequently oxygen supply to the myocardium by increasing blood flow down the coronary arteries during diastole. Deflation of the balloon is timed to occur just before ventricular systole which decreases myocardial oxygen demand by reducing left ventricular afterload, augmenting left ventricular ejection and reducing left ventricular wall tension. Correct IABP timing is critical because ejection of the heart against an inflated balloon could cause myocardial damage, and excessive offloading can steal blood from the coronary arteries.

Ventricular assist devices Ventricular assist devices (VADs) are simple circuits that use a centrifugal pump with an inflow and outflow to provide support to the right ventricle assist devices, left ventricle assist devices or both ventricles. Right ventricle assist devices take blood from the right atrium or right ventricle and return it to the pulmonary artery; and left ventricle assist devices take blood from the left atrium or left ventricle and return it to the aorta. Temporary VADs are sometimes used after bypass (when medical treatment fails and IABP therapy is insufficient) as a bridge to recovery. Temporary VADs provide short-term (a few days or weeks) support to a failing ventricle(s) in the hope that the ventricle(s) recover and the VAD can be removed. Long-term VAD systems are also

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available in some specialist centres. These are more sophisticated and provide long-term (months or years) ventricular support. They are used as a bridge to transplant or destination therapy.

Extra corporeal membrane oxygenation Extra corporeal membrane oxygenation (ECMO) is a technique used to provide life support for the critically ill. It provides temporary support for patients with cardiac failure, pulmonary failure or both, when no other form of treatment is likely to be successful. There are various indications for its use, including, but not limited to, severe cardiac and/or pulmonary failure, support post CABG and/or valve surgery, bridge to heart and/or lung transplant, adult respiratory distress syndrome (ARDS), pulmonary embolism and much more. There are two types of ECMO: veno-arterial (VA) and veno-venous (VV). VA supports cardiac output by taking de-oxygenated blood from the venous system and returning it, oxygenated, to the aorta. VA gives support to both the heart and the lungs. VV, or respiratory ECMO, takes deoxygenated blood from the inferior vena cava and returns it, after oxygenating and removing CO2, to the right atrium (RA), giving support to just the lungs. There are a few different cannulation options for ECMO. Time is a big limitation for patients on ECMO with a 15- to 21-day maximum for femoral cannulated ECMO, but longer than 2 months if centrally cannulated. Other problems encountered can include cannulation-associated haemorrhage, embolism, acute leg ischaemia and infection, those associated with systemic anticoagulation, GI bleeding, intracranial bleeding, and exsanguination resulting from circuit disruptions.

Phrases commonly used by the surgeon during cardiopulmonary surgery ‘Come up’ – surgeon asking the perfusionist to pump fluid up the arterial line to facilitate deairing of the connection to the arterial cannula ‘Flow down’ – surgeon asking the perfusionist to reduce the main pump flow in order to reduce the blood pressure to facilitate the application of a clamp or aid haemostasis ‘Give a hundred’ – after bypass, surgeon asking the perfusionist to give 100ml of blood or fluid to the patient from the bypass circuit ‘Go on’ or ‘on bypass’ – surgeon instructing the perfusionist to initiate cardiopulmonary bypass ‘Good swing’ – perfusionist telling the surgeon that the arterial cannula has been correctly inserted as evidenced by an appropriate pulsatile pressure ‘swing’ on the arterial line pressure monitoring; a non-pulsatile pressure could indicate that the arterial cannula has been placed into a false lumen, has pierced the intima of the aorta or may even have transfixed the aorta ‘Half flow’ or ‘quarter flow’ – surgeon asking the perfusionist to reduce the main pump flow to half or quarter of the calculated mid flow; normally to start filling the heart when coming off bypass ‘Pump’ – heart lung machine ‘Pump monkey’ – affectionate term for a clinical perfusion scientist; often used by ‘gas men’

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‘Pump off’ – surgeon asking the perfusionist to turn the main pump off in order to reduce the blood pressure to facilitate the application of a clamp or to aid haemostasis ‘Rewarm’ – surgeon asking the perfusionist to rewarm the patient ‘Suck and blow’ – surgeon asking the perfusionist to run the cardioplegia solution and suck on the aortic root vent at the same time; this allows removal of air from the aortic root.

Conclusion In this chapter, you have read the names of surgeons who led their teams into uncharted territory, in the surgical treatment of heart disease. In the early stages of perfecting these new techniques, many heroic patients did not survive, but with resolve, focus and adaptation of the operations a much greater number of patients’ lives have been saved. Today, modern materials and molecular engineering are enabling scientists to create new implantable devices that constantly improve the treatment we can offer patients. Cardiac surgery must constantly adapt and change to keep pace with scientific and technological advances. Cardiopulmonary bypass has been a developing technology since the 1950s and CPB is now a routine and safe procedure, with thousands of operations performed every day using CPB. Ongoing research to better understand the pathophysiological effects of CPB has led to significant improvements in perfusion technology and practice, which have reduced the adverse effects of CPB on patients undergoing heart surgery. Future research is likely to lead to continuing advances in perfusion technology and practice and offer further benefit to patients.

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References Ashcroft, M. [Lord] (2014). WW1 trooper who rewrote history books. The Telegraph. 4th January 2014. p 1. https://www. telegraph.co.uk/history/world-war-one/inside-first-world-war/10551121/WW1-trooper-who-rewrote-history-books.html (Last accessed 26.3.2019). Barker, C.F. & Markmann, J.F. (2013). Historical overview of transplantation. Cold Springs Harbor Perspectives in Medicine. 3(4), 1–18. Braile, D.M. & de Godoy, M.F. (2012). History of heart surgery in the world. Brazilian Journal of Cardiovascular Surgery. 27(1), 125–34. Bruce Fye, W. (1995). Julien Jean César Legallois. Clinical Cardiology. 18(10), 599–600. Cordell, A.R. (1995). Milestones in the development of cardioplegia. Annals of Thoracic Surgery. 60(3), 793–96. DeWall, R.A. (2003). Origin of the helical reservoir oxygenator heart-lung machine. Perfusion. 18(3), 163–69. Got, V.L. (2005). Lillehei, Lewis and Wangenstein: The right mix for giant achievements in cardiac surgery. Annals of Thoracic Surgery. 79(6), S2210–S2213. Gov.UK (2017). Infections associated with heater cooler units used in cardiopulmonary bypass and ECMO: Guidance for Healthcare Workers in the UK. https://www.gov.uk/government/publications/infections-associated-with-heater-coolerunits-used-in-cardiopulmonary-bypass-and-ecmo (Last accessed 26.3.2019). Hessel, E.A. (2014). A brief history of cardiopulmonary bypass. Seminars in Cardiothoracic and Vascular Anesthesia. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.871.5810&rep=rep1&type=pdf (Last accessed 26.3.2019). Kohler, P., Kuster, S.P., Bloemberg, G., Schulthess, B., Frank, M., Tanner, F.C., Rössle, M., Böni, C., Falk V., Wilhelm, M.J., Sommerstein, R.,. Achermann, Y., Ten Oever, J., Debast, S.B., Wolfhagen, M.J., Brandon Bravo Bruinsma, G.J., Vos, M.C., Bogers, A., Serr, A., Beyersdorf, F., Sax, H., Böttger, E.C., Weber, R., van Ingen, J., Wagner, D. & Hasse B. (2015). Healthcare-associated prosthetic heart valve, aortic vascular graft, and disseminated Mycobacterium chimaera infections subsequent to open heart surgery. European Heart Journal. 36(40), 2745–53. Lim, M.W. (2006). A history of extracorporeal oxygenators. Anaesthesia. 61(10), 984–95. Rimmer, L., Fok, M. & Bashir, M. (2014). The history of deep hypothermic circulatory arrest in thoracic aortic surgery. Aorta (Stamford). 2(4), 129–34. Russo, M., Taramasso, M., Guidotti, A., Pozzoli, A., Nietilspach, F., von Segesser, L.K. & Maisano, F. (2017). The evolution of surgical valves. Cardiovascular Medicine. 20(12), 285–92. Safi, H.J., Estrera, A.L., Miller, C.C., Huynh, T.T., Porat, E.E., Azizzadeh, A., Meada, R. & Goodrick, J.S. (2005). Evolution of risk for neurologic deficit after descending and thoracoabdominal aortic repair. The Annals of Thoracic Surgery. 80(6), 2173–79. Sax, H., Bloemberg, G., Hasse, B., Sommerstein, R., Kohler, P., Achermann, Y., Rössle, M., Falk, V., Kuster, S.P., Böttger, E.C. & Weber, R. (2015). Prolonged outbreak of Mycobacterium chimaera infectionafter open-chest heart surgery. Clinical Infectious Diseases. 61(1), 67–75. Shore-Lesserson, L. & Gravlee, G.P. (2000). ‘Anticoagulation for cardiopulmonary bypass’. In: G.P. Gravlee, R.F. Davis, M. Kurusz and J.R. Utley (eds) Cardiopulmonary Bypass: Principles and Practice. 2nd edn. Philadelphia: Lippincott, Williams & Wilkins. 435–72. Stoney, W.S. (2009). Evolution of cardiopulmonary bypass. Circulation. 119(21), 2844–53. Šušak, S., Redžek, A., Rosi , M., Velicki, L. & Okiljevi , B. (2016). Development of cardiopulmonary bypass – A historical review. Serbian Archives of Medicine. 144(11–12), 670–75. Taha, A.Y. & Shehatha, J.S. (2014). Standing on the shoulders of the giants: stories of 3 pioneers. International Journal of Clinical Medicine. 5, 133–37. The National Museum of American History. (2018). Dodrill GMR Heart. Online. http://americanhistory.si.edu/collections/ search/object/nmah_998420 (Last accessed 26.3.2019). The United States National Library of Medicine. (1927–2003). The Clarence Dennis Papers. Online. https://profiles.nlm. nih.gov/ps/retrieve/Narrative/BX/p-nid/343 (Last accessed 26.3.2019). Von Frey, M. & Gruber, M. (1985). Studies on the metabolism of isolated organs. A respiration-apparatus for isolated organs. Virchows Archiv für Physiologie. 9, 519–32. Werner, O.J., Sohns, C., Popov, A.F., Haskamp, J. & Schmitto, J.D. (2012). Ludwig Rehn (1849–1930): the German surgeon who performed the worldwide first successful cardiac operation. Journal of Medical Biography. 20(1), 32–34.

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Illustrations Fig 9.2 Fig 9.4 Fig 9.7 Fig 9.8

Reproduced by permission of the Mayo Historical Unit, Mayo Clinic, Rochester, Minnesota, USA. Reproduced by permission of Medtronic Reproduced with kind permission from the Perfusion Department, Hull & East Yorkshire Hospitals NHS Trust, Hull, UK Image reproduced courtesy of Crocodile House Ltd, www.crocodilehouse.co.uk



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10 Surgery for aortic root disease Caroline Toolan, Omar Nawaytou, Aung Oo

Introduction Operations for the aortic root are a great demonstration of how techniques have evolved to tackle specific challenges posed by anatomy and pathology (see Figure 10.1). We are now at an enviable stage where there are multiple options for repair, replacement, and even reinforcement, of the aortic root and we can consider the benefits of long-term survival and re-intervention rates rather than focusing only on operative mortality.

Sinotubular junction Arterial wall within ventricle (interleaflet triangle)

Ventriculo-arterial junction Ventricle within sinus

Basal ring

Figure 10.1: The clinical anatomy of the aortic root

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In this chapter, we will examine the disease processes that affect the aortic root and how they present in patients. We will also examine the important operative anatomy of the aortic root and the different operative techniques used, highlighting the way in which all these factors help to guide surgical decision-making.

Pathophysiology The most frequent reason for aortic root surgery is aneurysmal dilatation (Catrovinci et al. 2015). Although other pathologies may affect the aortic root (such as a root abscess in infective endocarditis or involvement of the aortic root in an acute type A aortic dissection), these may be repaired using other techniques such as patch repairs or reconstruction, rather than root replacement. Occasionally an aortic root replacement may be necessary to facilitate an aortic valve replacement in an otherwise entirely calcified (or ‘porcelain’) aorta. Aneurysmal disease remains the mainstay of aortic root surgery but what constitutes an aneurysm in the ascending aorta? An aneurysm is defined as a localised dilatation of a vessel that includes all three layers of the wall (ACCF et al. 2010). Normal range values in women lie between 3.50 and 3.74cm, and 3.63–3.91cm in men, with an abnormal aortic root and ascending aorta dilatation considered to be present at a diameter above 40mm (European Society of Cardiology 2014). The danger from aneurysmal disease of the aorta comes from an increase in tension within the vessel wall as the aneurysm gets larger. This increased tension is described by Laplace’s rule (Levick 2010); as aneurysms increase in size, the likelihood of developing an acute aortic syndrome that could lead to rupture and death increases. Acute aortic syndromes include aortic dissection, intramural haematomas and penetrating aortic ulcers (ACCF et al. 2010). When the ascending aorta or root reaches 55mm, there is a 15% chance of such adverse events occurring (Nardi & Ruvolo 2016). These studies have helped inform international guidelines and determine threshold diameters at which aortic root surgery should be considered and balanced against an estimated elective operative mortality of up to 5%. The aetiology of ascending aortic aneurysms essentially relates to structural weaknesses in the aortic wall. In a meta-analysis of patients who had undergone aortic root surgery, nearly 50% had either a diagnosed underlying connective tissue disease or a bicuspid aortic valve (Moorkhoek et al. 2016). Although good control of hypertension is important for general cardiovascular health, its contribution to ascending aortic dilatation appears to be minimal – with a greater contribution from age-related degeneration of elastic fibres in the media (Goldfinger et al. 2016). Innate weaknesses within the aortic wall, secondary to connective tissue disease or bicuspid aortopathy, can cause excessively rapid aortic expansion and aneurysm formation with the potential for acute aortic syndromes at reduced diameters of expansion. Operative guidelines reflect this, with interventions recommended at lower thresholds. Of the patients with connective tissue disease who undergo ascending aortic replacement, the most frequent – in the region of 20–30% of the patient population – is Marfan syndrome (Moorkhoek et al. 2016). Marfan syndrome is a genetic condition with autosomal dominance which causes abnormalities

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in the production of glycoprotein Fibrillin-1 within the elastic lamina of the aortic wall (MartínezQuintana et al. 2017). The term ‘cystic medial necrosis’ is used to describe this process, which manifests as aneurysmal dilatation in the aorta. Loeys-Dietz syndrome is another connective tissue disorder causing weakness of arterial walls. In this condition, however, aneurysmal disease can be more widespread in the vascular tree, also appearing at an earlier age with more rapid expansion (Loughborough et al. 2018). Given the aggressive nature of this disease, operative thresholds tend to be at the lowest aortic diameter in the guidelines (see Table 10.1). Patients with bicuspid aortic valves and dilated aortic roots are classed as having bicuspid aortopathy. This is a heterogeneous group of patients who present with aneurysmal disease on average in their fifth decade, approximately 15 years earlier than patients with tricuspid valves and no history of connective tissue disease (Losenno, Goodman & Chu 2012). Either calcified stenotic valves or severe aortic regurgitation may be associated with the dilated aortic root. Cause and effect relationships between the root and valve pathology remain uncertain and, although the condition does appear to have a genetic element, specific inheritance patterns are still being defined. Inflammatory processes that affect blood vessels, such as Takayasu and giant cell arteritis, can also cause degeneration of this elastic layer and subsequent aneurysmal change. Such patients may present as part of an acute inflammatory illness which can complicate surgical management with the need for immunosuppressive regimes (ACCF et al. 2010).

Table 10.1: Guidelines for operative intervention on the aortic root (adapted from ECS 2014 and AHA 2010) European Cardiac Society (ECS) 2014

American Heart Association (AHA) Task Force (ACCF 2010)

Balloon aortic valvuloplasty (BAV)

Aortic root >5.5cm or Aortic root >5cm if Growth rate >3mm/yr

Root diameter >50mm or Growth rate >5mm/year

Connective tissue disease

>50mm or >45mm and growth rate >3mm/yr

Marfan >50mm or Growth rate >5mm/year Loeys-Dietz >4.2cm (TOE) >4.6cm (CT)

Non-connective tissue disease

>55mm

>55mm or growth rate >5mm/year

Signs and symptoms of aortic root disease Presentation of aortic root disease will depend on the underlying pathology. Presentations may relate to the aorta and/or the aortic valve or patients may be completely asymptomatic.

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Symptoms secondary to the aorta may be chest pain. This is a very concerning feature as it may herald acute dilatation or even onset of an acute aortic syndrome.

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Aortic valve disease may exist concurrently with aortic root aneurysms. This may be a stenotic or regurgitate lesion. Patients may present with an incidental finding of a murmur; or, at more advanced stages, there may be evidence of heart failure with breathlessness and exercise intolerance. Patients with aortic stenosis may present with classic symptoms of angina and syncope.

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However, with the advent of more frequent imaging, aortic root abnormalities are often detected as an incidental finding on investigations for other pathology. For example, mediastinal widening to indicate an aneurysm may be detected on a chest x-ray or dilatation may be apparent on a CT scan.

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It is important to ask patients about any family history related to aortic disease, or sudden death, to establish whether there may be a genetic component that might contribute to complications at an earlier stage in their disease process.

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Investigations The three main modalities used to image the aortic root are echocardiography (ECHO), magnetic resonance imaging (MRI) and computed tomography (CT). Each one has particular benefits and may be used to glean different information. ECHO and MRI have the advantage of not using ionising radiation and can potentially provide functional information about valvular and ventricular function. ECHO is far quicker and can be done in a clinic, but operator variability may be greater. CT scans are faster and more readily available than MRI scans and give good reproducible resolution of the aortic wall, but the use of ionising radiation is a disadvantage for those requiring multiple scans throughout their lives. Aortic diameters are measured from the external diameter in both CT and MRI. However, in ECHO, the internal diameter is taken. In all cases the measurement must be taken perpendicular to the direction of flow (ACCF 2010). Many patients will be under surveillance for many years prior to aneurysmal disease reaching a stage where intervention is necessary. In such cases regular monitoring with interval scans is used. The timeframe of these scans is dictated by both the size and rate of expansion of the aortic root as well as the rate of deterioration of any aortic valve disease. In such cases it’s best to employ a consistent method of scanning to ensure that any changes in aortic diameter are not related to varying imaging techniques. The AHA guidelines provide a model surveillance schedule with which to monitor patients with known aortic dilatation (ACCF et al. 2010).

Medical management In patients whose aorta shows enlargement but is below operative thresholds, management is aimed at modifying risk factors to prevent further expansion. Controlling hypertension is important to reduce the risk of death from all cardiovascular disease. However, beta-blockers have been associated with a reduced rate of expansion in root aneurysm size, particularly in Marfan patients, making them a preferential choice in management of blood pressure in these patients (Chun, Elefteriades & Mukherjee 2013). There has also been interest in the use of angiotensin 2 receptor blockers, such as losartan and valsartan, to reduce aneurysm expansion rates, particularly in patients with Marfan and Loeys-Dietz syndromes. Angiotensin 2 blockers appear to interfere with, and slow down, intracellular signalling pathways that contribute to degradation of the elastic fibres in the aortic media (Dietz 2010; Takeda et al. 2016). So far, studies have failed to show treatment translating

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into any difference in times to surgical intervention or death. However, research is ongoing in this area (Gao et al. 2016).

Anatomical considerations in aortic root surgery We have considered why we might need to perform aortic root surgery; now we will address the different techniques and when they are suitable. The aortic root extends from the annulus of the aortic valve up to the sinotubular junction and includes the aortic valve leaflets, the coronary ostia and the sinuses of Valsalva. The patency of the aortic valve within the aortic root is governed by the interaction of the aortic annulus and valve cusp morphology. If the aortic cusps remain unaffected by disease, it may be possible to perform an aortic root repair rather than replacement by re-establishing annulus geometry.

Annulus When we think of the aortic valve annulus, we refer to the hinge points of the aortic valve leaflets themselves. However, when observing the leaflet insertion points, we can see that in fact they are not oriented in a circular annular arrangement but suspended in a crown-like position within a cylinder, with the sinotubular junction at the top and the nadirs of the cusps at the base (Anderson 2000). If either end of the cylindrical aortic root dilates, leaflet coaptation is compromised, ultimately leading to valvular insufficiency, which is usually seen on echocardiography as a central jet.

Cusps Although annular changes can be solely responsible for aortic valve failure, abnormal geometry of the cusps can also be responsible. The ratio of the free margin of the aortic valve leaflet to the length of its cusp insertion determines how mobile a cusp is and its propensity to prolapse. A proportionally greater length of cusp insertion to a small free margin can be seen in bicuspid valve disease. This leads to a restrictive pattern of leaflet motion, with the cusps in effect being held closer to the sinuses (El Khoury & de Kerchove 2013). Conversely, in connective tissue disease, excessive leaflet tissue may cause the overly mobile cusp to prolapse into the ventricle. These types of pathology are more likely to create an eccentric pattern of aortic regurgitation (in contrast to annular disease), as the asymmetry of the valve leaflets will direct a regurgitant jet in a particular direction.

Coronary ostia As part of the planning for any aortic root procedure, it is essential to identify the position of the coronary ostia and any disease affecting them (such as calcification or extensive aneurysm). Coronary arteries that are diseased may warrant concurrent bypass grafts. Coronary ostia that are heavily calcified or even fixed by aneurysmal disease, far from their normal anatomical position, may need additional Dacron extensions attached to the coronary ostia to reach the repaired root. These are known as ‘Cabrol’ grafts (Cabrol et al. 1981). Identification of the heights of the coronary ostia on CT or ECHO is also important, particularly in patients with bicuspid aortic valves. In these patients, the height and position of coronary ostia may vary from the usual pattern, becoming more distal on the aorta or closer to

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the commissures. Foreknowledge of this may prevent the surgeon inadvertently making aortic incisions very close to ostia that may compromise coronary button formation at a later stage.

Replacement or repair? Whichever operative strategy is used, the aim should be an enduring and satisfactory long-term outcome with low associated morbidity and mortality. As with many other aspects of cardiac valvular disease, correction of aortic root pathology can include either aortic root replacement or repair. Both strategies involve replacing dilated coronary sinuses with Dacron grafts and reimplanting coronary ostia as ‘buttons’. Where the techniques differ is in management of the aortic valve and basal annulus. Valve-sparing root repairs may use techniques to repair or refashion native valve cusps, in addition to supporting and reinforcing the annulus complex. Replacement, on the other hand, involves complete excision of the aortic valve, along with the coronary sinuses, followed by replacement with either a bio prosthetic or mechanical prosthesis embedded in a Dacron tube graft (see Figure 10.2) (Lansac et al. 2013).

Figure 10.2: Valve-sparing root replacement: A, B, C images illustrate the remodelling technique with external ring annuloplasty Although the average age of patients presenting for aortic root surgery is the sixth decade, there is also a large proportion of younger adults with connective tissue disease or congenitally bicuspid aortic valves. The advantage of an aortic root repair over replacement is particularly relevant in these cases, as preservation of their own valve may eliminate the need for antithrombotic medication and its side effects. This is especially important in women who are planning families and hoping to avoid potentially teratogenic coumarins. With these younger patients, the long-term durability of repairs and likelihood of re-intervention is extremely important. Any repair strategies must be able to stand up to the high standards offered by root replacement with a mechanical valve conduit.

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Some factors will automatically select a patient for replacement rather than repair, such as degenerative calcific aortic valve disease that is not amenable to any repair. Even in young patients, in whom repair would be best achieved, connective tissue disorders can leave the aortic valve too distorted to create a viable repair and replacement may be necessary regardless. Although some series have demonstrated great success with aortic valve repair, it is acknowledged to be a more technically complex procedure than replacement and results have been more difficult to reproduce. Importantly, any patient undergoing a valve-sparing aortic root repair must be consented for a replacement; and valve options should be discussed in the event of failure to produce a satisfactory repair. Ultimately the best operative strategy will depend on the underlying pathology of the aortic root, combined with what is the most acceptable long-term outcome for the patient.

Aortic root replacement The modified Bentall procedure has been described as the ‘gold standard’ for aortic root pathology. This is secondary to the high standards it has set in short- and long-term outcomes, with which valve- sparing operations must now compete. The modified Bentall procedure has proven itself reproducible, compared with the technical challenges posed by repair strategies, with some series showing 30-day mortality rates of less than 2% in elective cases (Girardi 2008). Recent metaanalysis has shown freedom from reintervention in Bentall procedures with mechanical valves of 99%, and rates of prosthetic valve endocarditis that are less than 1% (Pantaleo et al. 2017). The initial operation described by Hugh Bentall and Anthony de Bono was an adaptation of a planned ascending aorta repair, when they encountered aortic tissue at the sinotubular junction that was too fragile for a direct graft anastomosis (Bentall & De Bono 1968). The Bentall procedure itself involved opening the dilated ascending aorta, resecting the valve and implanting the new valve and conduit within the existing aortic tissue. Two holes were then made in the conduit wall at the level of the coronary ostia and the aorta around the coronary ostia was sutured directly to the conduit. The aneurysmal aorta was closed around the outside of the prosthesis, to control haemorrhage from the porous graft material; this became known as the ‘inclusion’ technique. The main complications arising from this technique revolved around haemostasis, with pseudoaneurysm formation occurring within the aortic wrap and around the coronary ostia because anastomosis sites were difficult to visualise. To combat this issue, the technique was ‘modified’. Preservation of the existing aortic aneurysm was abandoned. Instead, the coronary arteries were excised from the aorta with some surrounding aortic tissue as a ‘button’ that could then be directly anastomosed onto the aorta. The aortic tissue was also excised more closely at the root and various techniques have now been developed to maintain a haemostatic seal at the annulus-valve-conduit join (Kouchoukos, Karp & Lell 1977). In addition, advances in the engineering of the graft material, with gel-impregnated Dacron and the addition of haemostatic sealants, have helped eliminate many previous problems with haemostasis. There are many ways of carrying out aortic root replacement. The following method is routinely used in our department.

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Operative technique for aortic root replacement Patient preparation Monitoring: ●●

Central venous access

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Arterial line monitoring for blood pressure

Transoesophageal echocardiography: check the left ventricular function pre- and postoperatively; review prosthetic valve function to ensure no there are no postoperative paravalvular leaks. Draping:

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Ensure exposure of chest, groins and both legs to the ankle; if the implantation of coronary button fails, a saphenous vein graft might be necessary.

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Initiation of cardiopulmonary bypass Cannulation: Most often cannulation will be central, with direct cannulation to the aorta and venous drainage from the right atrium.

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Cardioplegia: Antegrade delivery (alone or in combination with retrograde) may be used, depending on surgeon preference and the presence of aortic regurgitation.

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Temperature: A temperature on cardiopulmonary bypass of 34°C is maintained (please note that this varies in every institution and it depends on the operating surgeon and patient condition).

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Vent: ●●

A right superior pulmonary vein vent is used to decompress the left ventricle.

Aortic cross-clamp: The clamp is applied high on the ascending aorta to provide space for the distal anastomosis to be sutured.

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First surgical steps Aortic transection: The aorta is transected above the sinotubular junction to be sure of any high coronary artery positions.

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Excision of valve and preparation of the root and coronary buttons: Stay sutures (5/0 prolene) are placed in the tissue above the coronary buttons to minimise direct handling

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The coronary ostia are dissected away from the aortic root tissue and the aortic tissue is cut, with a 5mm cuff left around the hinge points of the aortic valve

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The aortic valve is removed

In non-connective tissue disease, the coronary buttons are formed, leaving a rim around the ostia for ease of suture placement. However, in connective tissue disease, this rim is minimised.

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Valve and graft preparation and insertion/position If a mechanical aortic valve is to be used, there are composite options in which the valve is already embedded within a tube graft (see Figure 10.3). However, this is not the case for tissue valves, and the tissue valve needs to be positioned inside the tube graft (see Figure 10.4).

A

B

C Figure 10.3: The mechanical root replacement; sutures are parachuted into the annulus A: Mechanical valve with tube graft B: Interrupted valve sutures C: Annulus

B C

A

D E

Figure 10.4: The tissue valve in place with separate tube graft secured over the valve A: Tissue aortic valve B: Tube graft C: Nylon tape D: Cross clamp E: Aortic cannula The tube graft is usually 2–4mm larger than the valve diameter. The 2-0 Ethibond sutures are placed around the valve annulus and passed through the cuff of the replacement valve, as for an aortic valve replacement. However, additional sutures are placed through the tube graft positioned over the valve as well, securing the two together. The valve and tube graft (or composite, if using a mechanical valve) are parachuted into the annulus and the sutures are tied.

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A further ‘haemostatic’ layer is then formed, using a 4-0 monofilament suture, which, starting from the posterior aspect of the valve passes through the 5mm cuff of aorta and subsequently through the valve cuff and tube graft as a continuous suture. This forms a reinforced seal at the root and has the appearance of a Cornish pasty when finished. The root can be now be pressurised with blood against a closed aortic valve to check haemostasis.

Positioning and suturing the coronary buttons ●●



It is very important to ensure that there are no kinks in the coronary buttons caused by incorrect positioning on the graft, so the heart must be filled when deciding on the position of the tube graft. Using tension on the stay suture holding the coronary button, the tube graft can be accurately positioned. A green needle can then be passed through the tube graft at this level to show where the centre of the button will be positioned; and a ‘hot knife’ (which melts the plastic of the graft) can be used to create a correctly sized opening in the graft.



The coronary button is then sutured in place, using a continuous 5-0 prolene and starting at the most inferior aspect. It is important to check the sutures from the internal aspect of the graft, to look for dog ears or asymmetry, as these will leak if they are left. They can be corrected with additional sutures or, in the case of particularly friable aortic buttons, reinforced with pericardial strips.

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The left coronary button is often performed prior to the right, to ensure ease of access.

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Glues or sealants may often be applied to the root at this stage to assist haemostasis.

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Distal anastomosis

A B C

Figure 10.5: The completed aortic root replacement surgery A: New tube graft aorta B: Teflon felt with prolene suture C: Aorta The distal end of the tube graft is now anastomosed to the ascending aorta. This is done in two layers and in two halves. A continuous 3-0 prolene suture secures the posterior aspect of the aorta and the tube graft together and is further secured with rubber-shod clips.

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The internal aspect of this anastomosis is reinforced with interrupted 3-0 pledgeted prolene sutures.

The anterior part of the anastomosis is then completed with the continuous suture and reinforced – this time in the external aspect with 3-0 pledgeted sutures (see Figure 10.5).

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Termination of cardiopulmonary bypass Rewarming: ●●

The patient is rewarmed to normothermia as the distal anastomosis is completed.

De-airing the heart: A small cannula/needle may be inserted into the tube graft to facilitate ejection of air prior to aortic cross-clamp removal.

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Aortic cross-clamp removed, following complete de-airing.

Pacing wires are inserted in case of heart block and to facilitate weaning from cardiopulmonary bypass.

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The patient can be slowly weaned from cardiopulmonary bypass when parameters are satisfactory.

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Valve check: with the heart ejecting, the valve function can be checked on TOE and visual checks of the coronary buttons and haemostasis of the aortic root can be performed. It is important to note any abnormal function of the ventricular muscle in case this indicates poor perfusion of a coronary button that might necessitate either refashioning of a coronary button or a coronary artery bypass graft.

Aortic root repair with valve preservation The titans of aortic valve repair are Dr Tirone David and Professor Magdi Yacoub who developed their individual strategies for valve-sparing root replacements within a few years of one another. Both procedures involve removal of the aortic sinuses and replacement with a Dacron graft with re-implantation of the coronary arteries. Where they differ is in their approach to the basal aortic annulus. The ‘David’ procedure (also referred to as the re-implantation technique) involves dissecting the valve to the basal annulus, creating a reinforced suture line below the nadirs of the valve cusps, then parachuting the Dacron graft over the remaining valve posts, suturing the valve in situ within the Dacron graft (David 2011). The Yacoub procedure, or remodelling technique, leaves the basal annulus undisturbed; instead the graft material is scalloped, then sutured directly to the cut edges of the aortic sinuses (Yacoub et al. 1983). The re-implantation (David) technique confers additional stability on the aortic annulus at the ventricular level. However, this has been shown to restrict the mobility of the aortic valve annulus, making it a less physiological solution with additional leaflet stress that may contribute to leaflet trauma (Leyh et al. 1999). Nevertheless, the long-term outcomes appear to favour the David procedure. The additional annular support appears to translate into reduced rates of aortic insufficiency and re-intervention,

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particularly in patients with connective tissue disorders and ongoing annular dilatation (Tian, Rahnavardi & Yan 2013). Additional leaflet stresses do not appear to have a clinically meaningful impact in terms of valve failure. With increasing experience, both procedures are used and modified, depending on underlying disease processes – for example, the likelihood of further annular dilatation and the degree of disease of the sinuses. Valve-sparing aortic root repair can be performed with an operative mortality between 2 and 4% but such series are from experienced, selected centres. Freedom from reoperation is linked to aortic regurgitation and can exceed 90% at 10 years (Shrestha et al. 2012; David et al. 2013). Increasingly, cusp repairs are being integrated into repair strategies to expand the scope of valve preservation to patients with bicuspid valves and prolapsing valves that might previously have been considered unsuitable. The ultimate aim of a successful valve-sparing aortic root repair would be to achieve a coaptation height of >4mm and trace to no aortic regurgitation (El Khoury & de Kerchove 2013).

Key operative elements of a re-implantation valve-sparing root repair This section describes the technique at our institution, which is based on Dr Tirone David’s technique with modifications in graft sizing as per El Khoury (El Khoury & de Kerchove 2013).

Patient preparation Monitoring: ●●

Central venous access

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Arterial line monitoring for blood pressure

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Transoesophageal echocardiography (TOE): assessment of valve and root morphology are particularly important in aortic root repair to dictate strategy or switch to a replacement if the valve is unsuitable. Bicuspid or tricuspid valve, whatever degree of calcification, and the direction of any regurgitant jets or prolapsing leaflets are all important to guide technique. TOE is also essential to check the function of the aortic valve after root repair and to assess left ventricular function.



Draping: Ensure exposure of chest, groin and both legs to the ankle. If a coronary button fails, a saphenous vein graft may be necessary.

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Initiation of cardiopulmonary bypass Cannulation: Most often cannulation will be central, with direct cannulation to the aorta and venous drainage from the right atrium. Cardioplegia:

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Antegrade delivery alone (or in combination with retrograde) may be used, depending on surgeon preference and the presence of aortic regurgitation.

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Temperature: A temperature on cardiopulmonary bypass of 34°C is maintained; the temperature can vary according to the local hospital protocol for aortic root surgery.

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Vent: ●●

A right superior pulmonary vein vent is used to decompress the left ventricle.

Aortic cross-clamp: The clamp is applied high on the ascending aorta to provide space for the distal anastomosis to be sutured.

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Aortic transection: ●●

The aorta is transected just distal to the sinotubular junction.

Assessment of valve Stay sutures are placed in the commissural posts of the valve (see Figure 10.6) and the valve is tested with saline to assess coaptation.

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The commissural height is measured between the non-coronary and left coronary cusp. This is equal to the ideal sinotubular diameter and dictates the tube graft size. The other commissural posts are also measured to inform their insertion height at the point of root reconstruction.

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The geometric height of the leaflets is measured. This dictates the height of the scallops that will be cut into the graft to form a tailored root anastomosis.

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A

B

C

Figure 10.6: The aortic root aneurysm with normal valve A: Normal aortic valve B: Aneurysmal aortic wall C: Pledgeted aortic stay suture

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Dissection of the root The tissue is dissected away to expose the root below the nadir of the aortic valve cusps. This extends to within the interventricular septum around the right coronary cusp (see Figure 10.7).

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Coronary buttons are preserved as the aorta is cut away from the sinuses, leaving a 5mm rim of tissue that the tube graft will be anastomosed to.

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A B

C Figure 10.7: The aortic root excised and the valve preserved A: Coronary ostia/button B: Preserved native aortic valve C: Coronary ostia/button

Graft preparation The tube graft is scalloped to reflect the variation in geometric height of the cusps. This ensures that the height of the commissures of the valves does not become distorted, which would otherwise affect the competency of the valve (see Figure 10.8).

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Figure 10.8: The surgically prepared Valsalva graft

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Root reconstruction Up to 12 numbers of 2-0 pledgeted Ethibond sutures are positioned from inside the aorta to the external aspect at the ventricular aortic junction. The pledgets sit along the line that joins all the nadirs of the valve cusps (see Figure 10.9).

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A

Figure 10.9: The proximal subannular suture line with pledgeted sutures in situ A: Pledgeted suture in situ The tube graft is positioned over the aortic root with the scalloped edges aligned with the correct corresponding aortic sinuses. The Ethibond sutures are passed through the base of the tube graft and tied (see Figure 10.10).

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Figure 10.10: The aortic valve re-implanted within the graft

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The commissural posts are then secured to the internal aspect of the tube graft at their corresponding heights.

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A 4-0 continuous prolene suture is used to attach the proximal edge of the aortic root to the tube graft, inside which the valve is suspended.

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The aortic root can now be pressurised with blood to check both the competence of the valve and haemostasis (see Figure 10.11).

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Figure 10.11: The aortic root, pressurised with blood/saline, being checked for the competence of the valve and bleeding points

Figure 10.12: The second distal suture line, with anastomosis being performed

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Coronary buttons: ●●

As per aortic root replacement.

Distal anastomosis: ●●

As per aortic root replacement (see Figure 10.12).

Termination of cardiopulmonary bypass Rewarm, de-air and reperfusion: The patient is rewarmed to normothermia as the distal anastomosis is completed (see Figure 10.13).

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A small cannula may be inserted into the tube graft to facilitate ejection of air prior to aortic cross-clamp removal.

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Pacing wires are essential in case of heart block and to facilitate weaning from cardiopulmonary bypass.

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The patient is weaned from cardiopulmonary bypass.

Valve check: ●●

It is essential to check that the repair is satisfactory with TOE.

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After haemostasis and valve function is confirmed, drains can be inserted and the sternum closed.

Figure 10.13: De-airing and cardioplegia perfusion prior to distal anastomosis

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Postoperative care It is prudent to repeat E examinations prior to hospital discharge, especially for patients undergoing valve preservation procedures. Follow-up regimes with imaging usually take place at 6 weeks, 6 months, 12 months and annually thereafter for at least 5 years (ACCF et al. 2010). For patients with connective tissue disease or valve preservation procedures, postoperative surveillance will be life-long to ensure longevity of repairs and no further aneurysmal expansion of the aorta. Complications that may be picked up on postoperative checks can include pseudoaneurysm formation or dilatation of coronary buttons.

Minimally invasive procedures in aortic root disease The potential advantages of minimally invasive aortic root procedures lie in reduced blood loss from a small wound, more rapid mobilisation which may translate into decreased hospital stay (Phan et al. 2014). Cosmesis is also an important consideration for many patients, particularly younger patients with connective tissue disease. In small studies of selected patients, minimally invasive strategies have shown results that equal those achieved through median sternotomy (Shrestha et al. 2015). Access to the aortic root may be achieved through a hemisternotomy. TOE is essential in these approaches not only to assess the result of the aortic valve but also ventricular function – in particular, to identify LV dilatation as well as guiding insertion of peripheral cardiopulmonary bypass cannulae to ensure satisfactory positions. Suitability for peripheral cannulation is an important part of preoperative assessment in patients for any kind of minimally invasive surgery. CT scans are used to evaluate femoral and iliac vessels to access patency. Myocardial protection is another key aspect, particularly for patients with aortic regurgitation where antegrade delivery may fail and simultaneously dilate the heart as it flows back through the aortic valve. External defibrillator pads must be attached to the patient prior to draping. There is no space or access for use of internal defibrillator paddles with minimal access techniques in the event of ventricular tachycardia (VT) or ventricular fibrillation (VF) intraoperatively.

Personalised external aortic root support The personalised external aortic root support (PEARS) is an alternative strategy to management of aortic root dilatation in patients with a competent aortic valve. Custom-made polymer mesh supports are constructed, based on MRI or CT dimensions. The mesh is then secured around the external surface of the aorta (from root to the ascending), with spaces formed at the level of the coronary arteries. The aim is that the mesh will stabilise the aorta, preventing further expansion. Criticisms of this technique focus on the fact that the aortic intima remains in situ so there is a risk of aortic dissection. Additionally, this intervention necessarily takes place at an earlier stage than a replacement or repair. This is to ensure that annular dilatation cannot progress to the point at which intervention for the aortic valve is necessary, although it does expose patients to an

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element of operative risk while their risk of acute aortic syndromes may remain low. Promising results have been reported, with the main complication relating to coronary artery compromise as a result of impingement on the external support itself (Treasure et al. 2014).

Clinical scenario1 A 28 -year-old patient has been under follow-up for a number of years with a known diagnosis of Marfan disease. He has a dilated aortic root which has increased in diameter over the last 8 months, from 42mm to 48mm. His aortic valve is trileaflet and mildly regurgitant. Questions to be considered: 1. Is surgical intervention recommended in this case? Yes, surgical intervention would be indicated in this case. Despite the measurements being taken over an interval of 8 months rather than 6 months, the rate of change in aortic diameter is substantial and suggests that this patient has an actively expanding aneurysm which will rapidly reach 50mm. 2. What surgical options are available to the patient? It is preferable in this case to preserve the native aortic valve if possible, as this has the advantage of avoiding a lifetime of anticoagulation with warfarin. Given that the patient has Marfan disease, the mechanism for the mild aortic regurgitation will most likely be aorto-annulus ectasia, which can be successfully corrected with a valve-sparing aortic root replacement. Other options are an aortic root replacement (Bentall procedure) with either a biological or mechanical prosthesis. A mechanical prosthesis would have greater longevity but has attendant anticoagulation requirements. A biological prosthesis in a patient of this age may only last from 5 to 8 years maximum but this option must still be discussed with the patient. Some patients may prefer to take the risk of early repeat surgery rather than warfarin therapy, depending on their stage of life. It is essential that all these options are discussed with the patient prior to surgery, even if a valve-sparing root replacement is planned. If intraoperatively the valve cannot be preserved, a Bentall procedure will be performed with the preferred valve type. 3. What are his chances of requiring further operative intervention with these options? In Marfan patients the chances of requiring reoperation on the aortic root following valve preservation surgery has been shown to be less than 10% at 20 years; for a mechanical Bentall procedure reintervention rates are 5% at 15 years (David et al. 2014). The patient is essentially committed to a further operation within the next ten years if a biological valve is chosen secondary to the rate of valve degeneration in this age group.

Clinical scenario 2 A 52-year-old patient presents with mixed aortic valve disease, moderate stenosis and severe aortic regurgitation with symptoms of breathlessness. The aortic root is dilated at 46mm and the aortic valve appears bicuspid on TOE but does not look calcified. The valve appears suitable for repair and a valve- sparing root replacement is planned, with a mechanical valve replacement

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option if the repair fails. At operation the valve is amenable to repair and a valve-sparing root replacement is performed. However, when the patient is weaned off cardiopulmonary bypass the TOE examination of the valve shows severe aortic regurgitation with a large coaptation defect. Unfortunately, the repair has failed. Questions to be considered: 1. What were the primary indications for surgery in this patient? Although this patient has several indications for surgery, the main one is the severity of his aortic valve disease, particularly symptomatic aortic regurgitation. The fact that the aortic root measures in excess of 45mm is an indication for intervention in the context of planned cardiac surgery. 2. What features are more likely to promote a successful valve repair? Although the reconfiguration of sinotubular junction (STJ) and aortic annulus that is part of a valvesparing root repair can correct aortic regurgitation secondary to dilatation of these structures, leaflet abnormalities require special attention. Prolapsing leaflets with excess leaflet tissue can be plicated so that leaflet edges are lifted to increase their coaptation height. In contrast, in bicuspid aortic valve disease, leaflets are often restricted by thickened raphe at the commissures. The leaflets may need augmenting with patch repairs in order to have sufficient material to ensure coaptation. If valves are heavily calcified or very thickened and restricted, the amount of augmentation required may preclude repair from the outset. The variant of bicuspid aortic valve classified using the Siever’s classification can give an indication as to repairability. However, this is outside the scope of this chapter. 3. How can the valve-sparing root replacement be converted to a mechanical root replacement? If a valve-sparing root replacement has failed, the native valve needs to be excised. Since the patient has now been weaned off cardiopulmonary bypass, this will need to be reinstated. This is why it is important to check valve function prior to removing bypass cannulae and reversing anticoagulation. The patient will need to have the aortic cross-clamp reapplied and the heart given further doses of cardioplegia. Given that the root has already been repaired, the operation can essentially proceed as an aortic valve replacement. The Dacron graft can be opened, followed by excision of the native valve. Annular sutures are placed in the newly repaired aortic valve annulus and the aortic valve prosthesis is inserted and the aortotomy closed.

Clinical scenario 3 A 19-year-old female patient with a known bicuspid aortic valve is referred for consideration of valve- sparing root replacement. She has moderate aortic stenosis, severe aortic regurgitation with evidence of left ventricular dilatation and a dilated aortic root at 45mm. A TOE has shown a valve morphology suggesting that a repair will be unsuccessful and is therefore an unsuitable procedure. When discussing the pros and cons of mechanical and biological root replacements, the patient asks if there are any other options that could avoid either early reoperation or warfarin; she hopes to have a family in the future.

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Question to be considered: 1. What alternatives might there be to the options already mentioned? The Ross procedure was developed by South African-born British surgeon, Donald Ross. In this procedure the patient’s native pulmonary valve is excised and translocated into the aortic position (a so-called pulmonary autograft). The pulmonary valve is then replaced with a pulmonary homograft (using a cadaveric pulmonary valve). Because the homograft is in the lower pressure pulmonary system, the process of valve degeneration is far slower than it would be if directly implanted in the aortic position. The patient will not need anticoagulation because there are no mechanical prostheses. This is more frequently performed in paediatric cardiac surgery, as pulmonary autografts have the advantage of growing with the patient. However, the Ross procedure is technically complex and success also depends on patient factors such as a suitable-quality pulmonary valve to use as an autograft and matching annular sizes. In experienced centres, results have improved year upon year and in-hospital mortality can be less than 5%. Reintervention rates are approximately 25% at 20 years and this includes degeneration of both homografts and autografts (Martin et al. 2017). The Ross procedure is a highly specialised operation that requires a skilled team and careful planning for good long-term results; however, it remains an important consideration in suitable patients.

Conclusion As expertise continues to grow and longevity of root repair with valve preservation surgery is established, the position of the Bentall procedure as the gold standard may be challenged. More experience with such techniques translates into improvements in survival that may see the thresholds for surgical intervention in aortic aneurysmal dilatation reduce in the future. Most importantly, the techniques selected must be appropriate for the patient. This depends not only on the anatomy and pathology of their disease but also on a full and frank preoperative discussion, taking into account lifestyle considerations, life expectancy and attitudes to the possibility of future surgical reintervention.

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Martin, E., Mohammadi, S., Jacques, F., Kalavrouziotis, D., Voisine, P., Doyle, D. & Perron, J. (2017) Clinical outcomes following the Ross procedure in adults: a 25-year longitudinal study. Journal of American College of Cardiology. 70(15), 1890–99. Martínez-Quintana, E., Caballero-Sánchez, N., Rodríguez-González, F., Garay-Sánchez, P. & Tugores, A. (2017). Novel Marfan syndrome-associated mutation in the FBN1 gene caused by parental mosaicism and leading to abnormal limb patterning. Molecular Syndromology. 8, 148–54. Moorkhoek, A., Kortland, N.M., Arabkhani, B., Di Cebta, I., Lansac, E., Bekkers, J.A., Bogers, A.J. & Takkenberg, J.J. (2016). Bentall Procedure: A systematic review and meta-analysis. Annals of Thoracic Surgery. 101(5), 1684–89. Nardi P. & Ruvolo G. (2016). Current indications to surgical repair of the aneurysms of ascending aorta. Journal of Vascular and Endovascular Therapy. 1(2–9), 1–4. Pantaleo, A., Murana, G., Di Marco, L., Jafrancesco, G., Barberio, G., Berratta, P., Leone, A., Di Bartolomeo, R. & Pacini, D. (2017). Biological versus mechanical Bentall procedure for aortic root replacement: a propensity score analysis of a consecutive series of 1112 patients. European Journal of Cardiothoracic Surgery. 52(1), 143–49. Phan, K., Xie, A., Di Eusanio, M. & Yan, T.D. (2014). Meta-analysis of minimally invasive versus conventional sternotomy for aortic valve replacement. Annals of Thoracic Surgery. 98(4), 1499–511. Shrestha, M., Baraki, H., Maeding, I., Fitzner, S., Sarikouch, S., Khaladj, N., Hagl, C. & Haverich, A. (2012). Long-term results after aortic valve-sparing operation (David I). European Journal of Cardiothoracic Surgery. 41(1), 56–62. Shrestha, M., Krueger, H., Umminger, J., Koigeldiyev, N., Beckmann, E., Haverich, A. & Martens, A. (2015). Minimally Invasive Aortic Valve Surgery (II) ... Systematic review and meta-analysis: techniques and a guide for the academic surgeon. Annals of Cardiothoracic Surgery. 4 (2),148–53. Takeda, N., Yagi, H., Hara, H., Fujiwara, T., Fujita, D., Nawata, K., Inuzuka, R., Taniguchi, Y., Harada, M., Toko, H., Akazawa, H. & Komuro, I. (2016). Pathophysiology and management of cardiovascular manifestations in Marfan and Loeys-Dietz syndromes. International Heart Journal. 57(3), 271–77. Tian, D., Rahnavardi, M. & Yan, T.D. (2013) Aortic valve sparing operations in aortic root aneurysms: remodeling or reimplantation? Annals of Cardiothoracic Surgery. 2(1), 44–52. Treasure, T., Takkenberg, J.J.M., Golesworthy, T., Rega, F., Petrou, M., Rosendahl, U., Mohiaddin, R., Rubens, M., Thornton, W., Lees, B. & Pepper, J. (2014), Personalised external aortic root support (PEARS) in Marfan syndrome: analysis of 1-9-year outcomes by intention-to-treat in a cohort of the first 30 consecutive patients to receive a novel tissue and valve-conserving procedure, compared with the published results of aortic root replacement. Heart. 100(12), 969–75. Yacoub, M.H., Fagan, A., Stassano, P. & Radley-Smith, R. (1983). Results of valve conserving operations for aortic regurgitation. Circulation. 68(3), 321.

Illustrations Fig 10.1 Adapted from Anderson 2000 and redrawn by medical illustrator Mrs Helen Carruthers on 18.5.2018. Fig 10.2 Adapted from Lansac et al. 2013 but redrawn by medical illustrator Mrs Helen Carruthers on 18.5.2018).

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11 Thoracic surgery Asghar Nawaz, Piotr Krysiak, Rajesh Shah, Bhuvaneswari Krishnamoorthy

Introduction Since ancient times there has been an understanding of the importance of the structures housed in the thorax. However, it was not until the advent of anaesthesia and control of ventilation that real progress could be made in thoracic surgery. In the first half of the twentieth century, thoracic surgery was mainly performed on patients suffering from pulmonary tuberculosis, and there was major progress in developing techniques for treating open chest wounds and pleural empyema during the First World War (1914–1918). The Second World War (1939–1945) saw the refining of treatments for early decortication in the haemothorax. In the early twentieth century, the accessibility of antibiotics helped to control and eliminate pulmonary tuberculosis and (by reducing the risk of infection) helped to ensure more satisfactory patient outcomes after surgery (Nabuco de Araujo, de Campos & Pêgo-Fernandes 2016). In 1972 the double-lumen endotracheal tube was developed and this allowed the ventilation of only one lung. Surgeons could operate on the other lung more easily, at less risk to the patient. This was especially important in the development of minimally invasive surgery, as the pulmonary hilar structures are more accessible. Another expansion of thoracic surgery occurred with the development of endoscopy, which enhanced diagnosis techniques and treatment of the larynx, trachea and bronchi (Nabuco de Araujo, de Campos & PêgoFernandes 2016). Moving into the twenty-first century, thoracic surgery has become more accessible than ever with the development of sophisticated diagnostic interventions such as computerised tomography (CT), magnetic resonance imaging (MRI) scans and the introduction of new surgical techniques. The evolution of thoracic surgery is ongoing, with the continuing development and improvement of endoscopic interventions and the introduction of video-assisted thoracoscopic surgery (VATS) and robotic-assisted thoracic surgery (RATS).

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General considerations regarding thoracic surgery The thorax is a flexible structural conical frame, made of bones, cartilage and muscles, that encompasses the vital organs – i.e. heart and lungs in addition to major blood vessels and other structures. The pre-, intra- and postoperative care of thoracic surgical patients is essentially unique and different from cardiac surgery. In addition to the general routine preparation, assessment and the World Health Organisation (WHO) Surgical Safety Checklist (National Patient Safety Agency 2009), the following points are important: 1. Correct site marking: The site mark should match the pre-op clinic correspondence, consent, operation list, CT and chest x-ray (CXR) imaging and should also be confirmed with the patient. This is to help prevent ‘wrong site surgery’ which is a Never Event. ‘Never events are serious incidents that are entirely preventable as guidance, or safety recommendations providing strong systemic protective barriers, are available at a national level, and should have been implemented by all healthcare providers’ (National Health Services Improvements 2018, p. 4). 2. Appropriate preoperative investigations: For example, spirometry is usually required for all thoracic surgery. For more major surgery, such as anatomical lung resection, a full set of pulmonary function tests should be carried out (Lim, Baldwin & Beckles 2010). High-risk patients, with borderline WHO performance status and pulmonary function tests, may require further investigations in the form of 6-minute walk test, shuttle walk test, stair-climbing test and cardiopulmonary exercise testing to fully evaluate the risk stratification for patients undergoing major surgery. All test results should be filed and documented in the patients’ notes and be accessible to all clinicians involved in their care. This group of patients will usually require anaesthetic assessment for fitness, prior to surgery. Stopping smoking prior to surgery also has a significant impact on postoperative recovery and pulmonary rehabilitation/optimisation. Nutritional supplements and correction of any anaemia should be considered. 3. Imaging: All current CT and positron emission tomography (PET) scans must be available and checked. All scans must be within three months of the operation date. This is important, as a disease such as lung cancer may have progressed and may no longer be amenable to surgical resection. The patient will then require further investigations and possible referral to oncology for alternative treatment. 4. Biopsies and tissue samples: Another crucial aspect in thoracic surgery is obtaining samples and tissue biobsies, ensuring they are labelled and handled accurately and sent to the laboratories safely. It is not uncommon to require a frozen section and it is important that these patients are identified before surgery and that the histopathology laboratory is informed in advance. This means that a pathologist is alerted and able to provide the report in a timely manner. In addition, before the surgeons scrub for the surgery, they should prepare the forms, labelling them urgent, completing the patient’s clinical details and all relevant information to ensure that the laboratory can carry out the tests quickly and accurately

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5. Positioning: Depending on the required operation, positioning is crucial to ensure that the surgical team has easy access to the operation site. A thoracic surgeon should also be available to undertake a bronchoscopy if required and/or position the monitors if using VATS. 6. Drains: Usually a single pleural drain is used in relevant thoracic surgery; however, more than one drain will occasionally be required. If using more than one, it is good practice to label them and leave clear instructions with the recovery and/or ward staff about suction on the drains and duration. 7. Finally: The WHO Surgical Safety Checklist should be completed and a debrief carried out, to discuss any problems and their resolution during the surgery with the whole operating team. The operating notes should be written up and any electronic data completed. If a CXR is required, it needs to be ordered and checked to ensure there are no problems (such as a pneumothorax or any fluid collection).

Diagnostic procedures Thoracic surgeons perform a variety of interventions to help establish the diagnosis, including staging lung cancer tests to aid in optimum patient management. One of the most potentially helpful diagnostic tools is bronchoscopy, which is used to procure tissues or secretions from the tracheobronchial tree or adjacent structures. Specimens are usually described as washings, brushings, biopsies or needle aspirations. Although respiratory physicians perform some of these, thoracic surgeons carry out a different set of diagnostic procedures as listed below.

Endoscopic procedures Bronchoscopy This is an optical tool for the visual inspection of the airways. It is an important part of routine thoracic surgical intervention.

Figure 11.1: The setup of the flexible bronchoscope for bronchoscopy

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Flexible bronchoscopy Flexible bronchoscopy (see Figure 11.1), performed routinely, has many advantages and can be performed under sedation and topical anaesthesia or via the endotracheal tube in the anaesthetic room. The bronchoscopes range from 2.7 to 6.2mm outer diameter with variable working channels (see Figure 11.2). A forward field of view is 120 degrees and the angle of deflection is up to180 degrees. Secretions can be aspirated and the bronchoscope can pass through narrowed and distorted airways beyond obstructing lesions. It is particularly useful when assessing the lobar and segmental airways.

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Figure 11.2: The fibre-optic flexible bronchoscope in situ on the airway tract at the carina, with right and left bronchi. A: Bronchus B: Carina. Advantages/Indications: ●●

Patient comfort

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Allows bedside bronchial toilet in an emergency

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Can be used on a ventilated patient

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Segmental/peripheral biopsies can be taken

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Photography available

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Laser/brachytherapy can also be performed.

Disadvantages/Risks: ●●

Small channel

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Risk of breakdown.

Rigid bronchoscopy Rigid bronchoscopy, an essential skill for thoracic surgeons, is almost always performed under general anaesthetic and is an important diagnostic and therapeutic tool for thoracic surgeons. Adult rigid scopes used to come with variable internal diameters of 6, 7 or 8mm and they are 40cm in length. Modern scopes can be used with telescopic lenses and illumination is supplied by a halogen light source. Advantages/Indications: Clear view of major airways to obtain tissue and perform interventions (e.g. removal of foreign bodies, dilation of strictures and placement of stents)

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Managing massive haemoptysis

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Relieving tracheal obstruction

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Performing laser bronchoscopy

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Insertion of endobronchial valves and coild for emphysema.

Disadvantages/Risks: ●●

Risk of injury to gums and dislodgement of teeth

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Requires general anaesthesia

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Risk of hypoventilation and airway bleeding.

The endoscopic examination For this procedure the patient is usually positioned supine on the operating table. While taking care of the patient’s eyes, lips and teeth, the first phase of diagnostic rigid bronchoscopy is visualisation of the larynx and the vocal cords. Gently lifting the epiglottis will bring the vocal cords into view and their mobility can be assessed. Rotating the scope 90 degrees, the tip is passed between vocal cords to visualise the tracheal rings. With flexible bronchoscopy, all lobar and segmental bronchi must be examined carefully and systematically. The carina can be identified as a sharp vertical ridge at the end of the trachea. Always examine the normal side first to prevent spillage of infection or malignant contamination. The right main bronchus is short and in line with the trachea. The right upper lobe bronchus comes off just distal to the carina, at 90 degrees, and trifurcates into the apical, anterior and posterior segmental bronchi. The bronchus intermedius is a continuation of the right main bronchus and it trifurcates into the middle lobe (medial and lateral segments), common basal trunk and apical lower lobe segment.

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The left main bronchus is much longer and divides into the upper lobe bronchus (which gives off the lingular and tri-segments) and the lower lobe bronchus (which gives off the apical segmental and the common basal trunk). When mucosal changes of malignancy are visualised, a trans-bronchial brushing and biopsy should be performed, which yields a combined diagnostic accuracy higher than 90%. Bronchial brushings are generally obtained after the biopsy tissue. The bronchial brush may be inserted into narrowed segmental bronchi to provide cytologically diagnostic material. The brush is passed vigorously over the surface of the lesion and then promptly stroked onto the surface of the glass slide, which is immediately immersed in 95% ethanol. Better results are achieved if four separate brush specimens are obtained and sent to the laboratory. If the procedure performed is uneventful, the patient can be discharged the same day, following recovery, having had the isolated endoscopic procedure as a day case. In almost all bronchoscopic procedures, the samples/specimens are obtained for cytological and histopathological examination and it is vitally important to handle these specimens very carefully, making sure all the specimens are counted and recorded in the theatre books and sent to the laboratories in appropriately labelled containers.

Endobronchial ultrasound-guided transbronchial needle aspirate This is similar to the above, but not described here as this procedure is usually performed by respiratory physicians.

Mediastinal procedures Mediastinoscopy This used to be one of the most common operations performed by thoracic surgeons and was the gold standard for diagnosis/staging the mediastinum but is now only used selectively, due to CT, PET scans and prevalent use of diagnostic bronchoscopy and endobronchial ultrasound. Indications: ●●

Primary lung cancer staging (mediastinal adenopathy)

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Central tumours

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High radioactive tracer uptake in the tumours/nodal tissue on PET scan

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Biopsy of mediastinal masses.

Caution to be exercised in the following conditions: ●●

Huge cervical goitre

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Extensive calcification or aneurysm of the innominate artery

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Superior vena cava obstruction

Permanent tracheostomy after laryngectomy and radiation. Procedure This is generally performed as a day case procedure under general anaesthesia. The surgeon

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usually operates from the head-end of table and the patient is positioned supine, with the neck moderately extended using an interscapular roll. Elevating the table head can help decrease the venous pressure. Video mediastinoscopy is a safe option that allows excellent visualisation. A 3cm transverse skin incision is centred between the anterior borders of the sternocleidomastoid muscles, 2cm above the jugular notch, and carried through the platysma. The avascular space between the strap muscles is opened vertically by blunt dissection; and palpation of the trachea aids in guiding to the plane. Using the middle finger, a tunnel is created in the pre-tracheal space and the scope is passed in front of the tracheal rings. If in doubt, needle aspiration may help differentiate between the nodes and vessels. Lymph nodes stations 2 (upper paratracheal), 4 (lower paratracheal) and 7 (subcarinal) can be sampled when staging lung cancer. For mediastinal conditions, biopsies can be taken from the mass. Bleeding is usually minor and requires no treatment. To assess haemostasis, the scope is withdrawn slowly and the space is filled with a swab for 1–2 minutes. Usually no drain is required and the wound is closed in layers.

Anterior mediastinotomy Also known as a parasternal mediastinotomy (Chamberlain procedure), this is a means of accessing the masses and nodes not reached by cervical mediastinoscopy in the subaortic region (stations 5 and 6). This approach can also be used on the right side and offers access to the upper hilum (station 10), the lung, and pleura on both sides. In addition to diagnosing and staging of lung cancer, an anterior mediastinotomy can be used to biopsy many anterior mediastinal masses. VATS can be used as an alternative approach. Procedure The patient is positioned supine and selective lung ventilation through a double-lumen endotracheal under general anaesthesia may be helpful. Adequate exposure into the mediastinum is achieved via a 4–6cm transverse incision made just lateral to the sternum at the second or third costal space. The mediastinum is then entered through the posterior perichondrium. The internal mammary artery and vein are retracted and spared. The mediastinal pleural reflection is separated bluntly from the posterior table of the sternum and retracted laterally. Finger dissection opens the loose areolar tissue and extends inward until the aorta, pulmonary artery, and intervening space are noted. Enlarged nodes can be sampled directly or through the mediastinoscope using the technique described above. If the pleura was not entered, drainage is usually not required.

Video-assisted thoracoscopy as a diagnostic tool The use of VATS as a diagnostic tool for pleural diseases, solitary pulmonary nodules and interstitial lung diseases has now been well accepted in mainstream thoracic surgery. The surgeon is very dependent on their assistant during VATS procedures and an able, knowledgeable assistant is crucial for the safe conduct of the operation. The assistant learns how to hold and manoeuvre the camera, keeping the working station in the centre of the screen and anticipating the next step to facilitate the smooth running of the procedure. Rotating the lens can give superior views but the camera must be kept vertical.

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Procedure The patient is placed in a full lateral decubitus position and the table flexed to widen the rib spaces on the operative side. Under general anaesthesia, selective single-lung ventilation is achieved using either a double-lumen endotracheal tube (ETT) or a bronchial blocker via ETT (depending on the anaesthetist’s preference). The procedure can be performed with one or several ports, depending on the procedure and experience/preference of the surgeon. For general exploration, three ports (placed in a triangular fashion) are used, one for the camera and two for operating instruments. The first 10mm port entry for the camera should be made by blunt dissection, using a finger to avoid iatrogenic injury to the lung in case of adhesions. This is usually sited in the mid-axillary to anterior axillary line, at the 7th or 8th intercostal space. The other two instrument ports are inserted under video guidance. Five- or 10-mm thoracoscopes are used with a 0- or 30-degree lens and a three-chip 3D video camera. Pre-warming the thoracoscope in a sterile hot-water bath effectively prevents fogging of the lens. For generalised lung and pleural problems, at least two to three biopsy samples are taken from different places. Most surgeons take a full-thickness pleural biopsy when dissecting for the first port entry.

Common indications for diagnostic VATS Pleural disease: ●●

Pleural effusions/masses

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Identification of source of haemothorax/chylothorax

Pleural space infections/empyema and localisation of broncho-pleural or pleuro-peritoneal fistulae.

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Pulmonary disease: ●●

Diffuse interstitial disease/pulmonary infiltrates

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Solitary pulmonary nodules

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Lung cancer staging and assessment of operability.

Mediastinal disease: ●●

Mediastinal cystic and solid mass lesions and lymphadenopathy.

Thoracic therapeutic procedures Tracheobronchoscopic procedures An airway intervention is a highly specialised thoracic surgical procedure practised by experienced thoracic surgeons. The endobronchial management takes a secondary palliative position for acutely unwell patients with inoperable tracheobronchial tumours. It is crucial that the surgeon is always in attendance in the operating room before the start of the anaesthesia for endoscopic procedures. Assistance is required to handle the scopes, instrumentation and tissues. There are several interventions for which a thoracic surgeon is

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needed, including tracheobronchial dilatations (using serial bougies or balloon dilatations that may necessitate fluoroscopy), endobronchial stent placements, mucous plugs and foreign body removal, haemoptysis and mechanical debridement, debulking using electrosurgery, laser, cryotherapy, brachytherapy and argon plasma coagulation. The operative details of endoscopic procedures are beyond the scope of this book but essentially surgeons need to follow the same principles as those elaborated in the endoscopic diagnostic procedures. Ensure that fluoroscopy is available for bronchoscopic balloon dilatation procedures.

Thoracic incisions Positioning, preparation and prophylaxis Most general thoracic surgical procedures are done with patients in the right or left lateral decubitus position with the spine parallel and close to the edge of the table. Pressure points are protected with padded foam pads to avoid positioning injuries due to nerve stretching or compression at pressure points. In addition to mechanically supporting the chest wall, a roll should be placed under the dependent chest wall to take pressure off the shoulder and brachial plexus. One or two pillows should be placed between the legs. The dependent areas e.g. tibial tuberosity, lateral malleolus should also be padded. Various manoeuvres are available to hold the patient in an appropriate lateral position. These include placing a sandbag under the operating table mattress, and positioning rolled sheets front and back, and beanbags. Padded straps or adhesive tape placed under surgical towels at the hip and the calf are also used. The dependent arm is flexed at the elbow and padded. The superior arm can be flexed similarly and appropriately padded, obtaining the so-called praying position, or it can be extended on a padded arm holder. Finally, the operating table is flexed (or an inflatable bag/gel bag can be used) to spread the intercostal space. Intermittent pneumatic compression devices can be applied prior to induction of anaesthesia, as they are a useful adjunct, helping to prevent the development of a deep vein thrombosis. Antibiotic prophylaxis should be given prior to skin incision and a dose as necessary to maintain adequate levels throughout the operation. A forced-air patient warming device helps to keep patients normothermic.

Posterolateral thoracotomy This incision (with serratus anterior muscle-sparing) is probably the most common incision used for open thoracic surgery. The posterolateral thoracotomy incision is made with the patient in the lateral decubitus position. The variable-length skin incision is placed to provide access to the appropriate intercostal space (ICS), most commonly the 5th ICS through the bed of the unresected 6th rib. The classic incision starts in front of the anterior axillary line, curves two fingerbreadths under the tip of the scapula, and extends vertically on a line halfway between the posterior midline, over the vertebral column and the medial edge of the scapula. The advantage of this approach is superb exposure to the operative site; and the disadvantage is the time expended because of the extent of the incision.

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With electrocautery, the anterior part of the latissimus dorsi muscle and the lower portion of the trapezius muscles are divided. The serratus anterior muscle is spared and retracted anteriorly. Placing a large Richardson or scapula retractor beneath the scapula, the surgeon’s hand is passed paraspinally, adjacent to the spinal cord, towards the head; and the operating surgeon should count the ribs caudally to locate the desired intercostal space. In modern practice the rib is not resected, and the neurovascular bundle is preserved and protected. The lung is then deflated, and the intercostal muscle is carefully incised down to the parietal pleura, using the electrocautery or periosteal elevator. If the lung does not drop away freely, adhesions should be suspected that may need to be released carefully. A Tuffier, Rienhoff or Finochietto-type rib spreader can be placed to open the ribs spaces slowly and in stages to minimise the chance of a rib fracture. Closure of the incision is carried out after inserting one or two chest drains through a separate stab incision, inferior to the skin incision in the anterior and midaxillary lines. Tunnelling the drain tract reduces the risk of surgical emphysema. At the end of the operation the bridge or bean bag or gel roll is taken off to aid rib approximation and two or three pericostal sutures of heavy absorbable material (such as no 1 Vicryl) are used to bring them back in position. Then both the musculofascial planes are closed with a running absorbable no. 0 Vicryl suture. The subcutaneous tissues are closed with a size 2-0 running suture of the same material and the skin, with a 3/0 Monocryl in a subcuticular fashion. All closures of incisions described in this chapter will use the above technique unless otherwise stated.

Axillary thoracotomy This is a good muscle-sparing incision for uncomplicated, straightforward pulmonary operations, which provides access to the apex of the lung and is also used for first rib resections. It is not recommended for complex operations as it provides less exposure. The main advantages are the speed of opening and closing and the reduced blood loss from minimal muscle transection.

Anterior thoracotomy The patient can be positioned supine, or with a roll placed under the back, and the incision is usually made in the 4th ICS. This incision can be altered in order to place it in the inframammary crease in women, for cosmetic reasons. Thoracic surgeons limit its use and it is mostly employed for lung transplant.

Thoracoabdominal incision This incision is commonly used for open thoracoabdominal aortic operations and oesophageal operations. It provides an extended exposure both to the thorax and abdomen for these difficult operations. It is less commonly used for routine thoracic surgery.

Median sternotomy The patient is positioned supine, with their arms by their side, and some surgeons use the gel bag in the interscapular area. The vertical midline skin incision starts from the suprasternal notch

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and ends at the xiphoid process. Townsend et al. (2016) describe how dissection is carried down through the scarpa’s fascia and extended above the sternal notch to divide the clavicular ligament using cautery. The apex of the linea alba is divided, allowing a finger to be passed cranially behind the sternum. This enables blunt dissection to sweep away the pleura and pericardium. The saw is used to split the sternum midline and haemostasis is achieved with cautery to the sternal edges and bone wax for bone marrow. The median sternotomy is the incision of choice for many anterior mediastinal lesions, but it can also be used for the resection of bilateral or occasionally for anterior trans-pericardial repair of post-pneumonectomy bronchopleural fistula. At the end of the procedure, the sternum is reapproximated with surgical stainless-steel wires.

Clamshell incision (bilateral transverse thoracosternotomy) The patient is positioned supine and the transverse incision is usually made over both 4th ICSs. The pectoral major muscle is lifted off the rib and the sternum and is then transected with an oscillating saw, after ligating both the internal mammary vascular bundles. The retractors are used on each side to get the maximum exposure. This incision is primarily used for bilateral lung transplantation; it is less commonly used for bilateral general thoracic surgical procedures such as the resection of bilateral metastatic lesions to the lungs and large anterior mediastinal masses. Heavy polyglycolic acid pericostal sutures are used to approximate the ribs, and figure-of-eight stainless- steel wires are used to close the sternum.

Lung resections Lung resections encompass a variety of operative procedures that could be grouped as anatomical and non-anatomical lung resections. A wedge resection or an excision biopsy are non-anatomical lung resections. Anatomical resections may be subgrouped to include segmentectomy, simple lobectomy, complex lobectomy (sleeve lobectomy, double-sleeve resection, bronchoplasty and pneumonectomy. A brief account of these common operations follows below.

Lobectomy A lobectomy is the most common operation and remains the definitive procedure of choice for early- stage non-small-cell lung cancer. It is an anatomical resection that ensures removal of the regional lymph nodes that course along the lobar bronchus, and thus provides the best staging information and local control. Most thoracic units in the UK are now performing VATS lobectomies in addition to open lobectomies, and the operative strategies can overlap. The VATS type is frequently performed through an anterior approach; and the posterior approach is used for the open cases. Bronchoscopy is routinely performed to evaluate the anatomy, suction the secretions and assess the resection in case of endobronchial tumours. Once the chest is opened, confirmation of the location and assessment for the resectability of the tumour is sought before committing to any structural division. The hilar and mediastinal lymph node dissection/sampling is an essential part of the operation for lung cancer surgery and should be performed either at the start, during dissection or at the completion of lobectomy (Goldstraw et al. 2015).

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Right-sided pulmonary resection Following the bronchoscopy, the anaesthetist places the double lumen endobronchial tube or bronchial blocker for single lung ventilation. As described above the patient is positioned in the left lateral decubitus position and the chest is entered through a standard serratus-sparing posterolateral thoracotomy via the fifth intercostal space or ports for VATS are inserted to surgeons’ choice (see Figure 11.3). The double retractor may be used in open cases to provide better exposure. Usually, the VATS lobectomy is performed with the anterior Copenhagen technique, so it is easy to follow similar steps even for the open cases.

A

B

Figure 11.3: The right lateral position, scapula, VATS utility incision marking A: Scapula B: Fifth intercostal space

Right upper lobectomy The lung is retracted posteriorly to expose the hilum using diathermy (we use a stick blunt diathermy in our centre which is very tissue-friendly), while being aware of the proximity of the phrenic nerve. The superior pulmonary vein is identified, dissected distally and either encircled or directly divided with a 30mm vascular stapler, making sure to preserve the middle lobe vein and also being aware of the pulmonary artery behind it. The truncus artery is then dissected free and ligated with the 30mm vascular stapler. We do not routinely divide the azygos vein but rather preferably preserve it. The lung is then flipped medially, and the posterior parietal pleura is incised so that the upper lobe of the bronchus is exposed. The posterior part of the oblique fissure is taken with the 60mm green stapler. This manoeuvre exposes the recurrent artery branch, which can also be

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stapled with the 30mm vascular stapler. By peeling away the parietal pleura at its bifurcation from the bronchus intermedius, the right upper lobe bronchus is brought into view. The right upper lobe bronchus is then divided with the stapler after confirming the patency of the bronchus intermedius by a lung reinflation test or confirmation from the anaesthetist carrying out a bronchoscopy. Finally, the transverse fissure is divided with the green 60mm stapler, making sure the pulmonary artery to the middle lobe and lower lobe is kept intact. The bronchial stump is then tested to check for the presence of an air leak under the water. The inferior pulmonary ligament is released so the lung fills up the space by upward movement. The fissure needs to be divided at the end; and use of the stapler to complete the fissure helps reduce the air leak. At least lymph node stations 2R, 4R, 7 and station 10 should be sampled for upper lobectomy cases. This procedure has also been carried out using VATS (see Figure 11.4).

D

A

B

C

F

F E

Figure 11.4: VATS right upper lobectomy and hilar lymph node dissection station 10 area, inside the thoracic cavity A: Superior vena cava B: Azygos vein C: Phrenic nerve D: Vagus nerve E: Upper lobe removed F: Lungs

Middle lobectomy The lung is retracted posteriorly and the hilar pleura overlying the superior pulmonary vein is incised and the middle lobe vein identified. The vein is ligated and divided with the 30mm vascular stapler. The anterior oblique fissure is partially divided with the green stapler, which exposes the middle lobe bronchus that lies immediately posterior to the vein. The bronchus is stapled with the device, after confirming the patency of the remaining bronchus with a test reinflation. The middle lobe arterial branch lies just posteriorly and is ligated with a 30mm

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vascular stapler. If required, the horizontal fissure can be divided with the green stapler to take the lobe out. A mediastinal lymph node dissection is then completed to obtain the most accurate and complete staging information.

Right lower lobectomy This lung is retracted toward the apex of the chest and the inferior pulmonary ligament is released, up to the level of the inferior pulmonary vein, and station 9 is dissected at this point. The inferior pulmonary vein is dissected by dividing the posterior parietal pleura cranially until the bronchial bifurcation and it is then divided with the vascular stapler. The pulmonary artery must be identified within the fissure to complete the resection; and usually the basal trunk and apical segmental branches are divided together using the stapling device. With the lung retracted, a linear stapler may be inserted from just above the apical segmental arterial branch, encompassing the parenchyma within the fissure to divide it. The lower lobe bronchus is divided with the stapler, after confirming the patency of the upper and middle lobe bronchus using either ventilation or bronchoscopy. At least lymph node stations 7, 8, 9 and 10 should be dissected for proper staging.

Left-sided pulmonary resection Following the bronchoscopy, the anaesthetist places the double-lumen endobronchial tube or bronchial blocker for single lung ventilation. As described above, the patient is positioned in the right lateral decubitus position and the chest is entered through a standard serratus-sparing posterolateral thoracotomy, via the 5th intercostal space, or ports for VATS are inserted, according to the surgeon’s preference. The double retractor may be used in open cases to provide better exposure. The VATS lobectomy is commonly performed with the anterior Copenhagen technique, so it is easy to follow similar steps even for the open cases. The surgeon should be aware of a few distinct features on the right, such as the aortic arch, the aortopulmonary window and the recurrent laryngeal nerve.

Left upper lobectomy The lung is retracted posteriorly to expose the hilum using diathermy, while being aware of the proximity of the phrenic nerve. Some surgeons prefer to get proximal control by encircling the left main pulmonary artery for the known feared widow maker complication (avulsion of short broad base apicoposterior segmental pulmonary artery branch). The superior pulmonary vein is identified, dissected distally and either encircled or directly divided with the 30mm vascular stapler. The apicoposterior segmental artery is then dissected free and ligated with the 30mm vascular stapler. The anterior segmental and lingular branches usually require dissection in the fissure. Exposure of the left upper lobe bronchus is achieved both from the anterior aspect of the hilum and from within the fissure. The left upper lobe bronchus is divided with the stapler, after confirming the patency of the lower lobe bronchus by lung reinflation test or confirmation from the anaesthetist carrying out a bronchoscopy.

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Finally, the fissure parenchyma is divided with the green 60mm stapler, making sure the pulmonary artery to the lower lobe is intact. The bronchus stump is then tested for an air leak under the water. The inferior pulmonary ligament is released so the lung fills up the space by upward movement. The last stage in this procedure is division of the fissure; and use of the stapler to complete the fissure helps reduce the air leak. At least lymph node stations 5, 6, 7 and station 10 should be sampled for an upper lobectomy.

Left lower lobectomy This is one of the easiest lobectomies, but a poorly developed fissure can make it challenging. With the lung retracted toward the apex of the chest, the inferior pulmonary ligament is released up to the level of the inferior pulmonary vein and station 9 is dissected at this point. The inferior pulmonary vein is dissected by dividing the posterior parietal pleura medial to the aorta, until the bronchial bifurcation, and divided with the vascular stapler. The anterior part of the oblique fissure is then dissected above the bronchus. The pulmonary artery must be identified within the fissure to complete the resection and usually the basal trunk and apical segmental branches are divided together (or separately) using the stapling device. The lower lobe bronchus is divided with a stapler, after confirming the patency of the upper and lingular bronchus using either ventilation or bronchoscopy. The oblique fissure is divided from anterior to posterior, allowing the lobe to be removed. At least lymph node stations 7, 8, 9 and 10 should be dissected for proper staging.

Sublobar resections Sublobar pulmonary resections comprise segmentectomy and wedge resections and are usually performed for inflammatory, metastatic lesions or to preserve the lung in case of primary lung cancer.

Segmental resections Segmental resections are based on the principle of following the lymphatic drainage and bronchial branches of the segments resected. Segments that are commonly amenable to segmentectomy include the trisegment lingular and apical segments.

Wedge resections These simple operations are the most common type of non-anatomic pulmonary wedge resections. Stapling techniques are probably used for more than 95% of wedge resections. The other major technique used in wedge resection is cautery or laser excision, sometimes referred to as a Perelman procedure.

Pneumonectomy Pneumonectomy is the surgical removal of an entire lung. It is technically one of the easiest and yet also one of the riskiest operations performed in the chest (Sugarbaker et al. 2009), as the final result is that the patient is left with only one lung. It is mostly performed in cases of lung cancer (central tumours, or tumours invading main bronchus or violating the fissures) or when the lung has been destroyed by inflammatory conditions, such as tuberculosis.

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Procedure The operating procedure is somewhat similar to that of a lobectomy. Preoperative bronchoscopy should always be performed to achieve the R0 (corresponds to complete cure or remission) resection. Following the double-lumen endobronchial tube intubation, the patient is placed in a lateral decubitus position. The most common approach is the posterolateral thoracotomy at the bed of the 6th rib. If a pneumonectomy is anticipated, care is taken to harvest an intercostal muscle pedicle while performing the thoracotomy. Once the chest has been opened, resectability is assessed. The inferior pulmonary ligament is released. The lung is retracted posteriorly to expose the anterior hilum, after incising the overlying pleura posterior to the phrenic nerve (which is usually preserved). The superior and inferior pulmonary veins are dissected free. The main pulmonary artery may have to be controlled first and encircled before the superior pulmonary vein. Test clamping the pulmonary artery for a few minutes before division of any anatomical structures is a useful manoeuvre, ensuring the patient remains haemodynamically stable. Every effort should be made to preserve the recurrent laryngeal nerve for better recovery. The sequence of ligation of the hilar structures depends on the position of the lesion and the surgeon’s preferences. The staplers are commonly used to ligate and divide and it is preferable to retain the short bronchial stump. After multi-station lymph node dissection/sampling, the chest cavity is washed with warm water and the stump tested for a leak and then covered with a flap of pleura, fat or muscle. Most surgeons tend to keep the drain in overnight, clamped with intermittent release for removal next morning.

Decortication for empyema Patients with frank pus or cloudy fluid or a pH 7 days) is a common complication after lung resection surgery (incidence ~10%). It is associated with increased hospital stay and cardiorespiratory morbidity. Risk factors include: ●●

Age, especially elderly patients >70 years old

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History of COPD

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Smoking

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Higher than average body mass index

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Type of pulmonary resection

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Presence of adhesions

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Incomplete fissure.

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Prolonged air leaks are self-limiting in most patients. Blood or talc pleurodesis can be considered in some cases. If a broncho-pleural fistula is suspected after major lung resections, bronchoscopy should be carried out to exclude stump dehiscence. If all conservative measures fail, surgical closure of the leak or insertion of an endobronchial valve are further options. Management of prolonged air leaks should be individualised according to the patient’s risk factors and the procedure undergone.

Clinical case scenario 2 A 76-year-old female undergoes a right upper lobectomy for a squamous cell carcinoma. Her past medical history includes severe osteoarthritis and previous total hip replacement, hypertension and chronic pain. She is also a current smoker. The procedure is uneventful and the patient is admitted to the thoracic ward. The team struggle to achieve effective analgesia. The patient has a poor cough effort and her oxygen requirements are slowly increasing. A chest X-ray shows a white-out of the right lung. The patient is taken back to theatre for a bronchoscopy and copious secretions are cleared from the intermediate bronchus.

Discussion Postoperative pulmonary complications are common following lung resection, and pneumonia and atelectasis are the most common of these complications. Patients who develop postoperative pulmonary complications have a higher risk of prolonged hospital stay, intensive care admission and mortality. Atelectasis occurs in up to 40% of patients. It often manifests around 24 hours postoperatively but may not be clinically significant. Risk factors include: ●●

Age >75 years

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BMI >30kg/m2

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American Society of Anaesthesiologists (ASA) >3

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History of smoking

COPD. In the case outlined above, failure to achieve effective analgesia led to poor cough effort and subsequent sputum retention. If not addressed promptly, this can progress to pneumonia. Initial measures to treat and prevent postoperative atelectasis include effective analgesia, physiotherapy (including incentive spirometry), early mobilisation and nebulisers. In severe cases, bronchoscopy, CPAP or even tracheostomy might be required.

●●

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References Goldstraw, P., Chansky, K., Crowley, J., Rami-Porter, R., Asamura, H., Eberhardt, W.E.E., Nicholson, A.G., Groome, P., Mitchell, A. & Bolejack, V. (2015). The IASLC lung cancer staging project: Proposals for revision of the TNM stage groupings in the forthcoming (eighth) edition of the TNM classification for lung cancer. Journal of Thoracic Oncology. 11(1), 39–51. Hansen, H.J. & Petersen, R.H. (2012). Video-assisted thoracoscopic lobectomy using a standardized three-port anterior approach – The Copenhagen Experience. Annals of Cardiothorac Surgery. 1(1), 70–76. Kaiser, L., Kron, I. & Spray, T. (2014). Mastery of Cardiothoracic Surgery. 3rd edn. Philadelphia: Lippincott Williams & Wilkins & Wolters Kluwer. Lim, E., Baldwin, D. & Beckles, M. (2010). Guidelines on the radical management of patients with lung cancer. Thorax. 65 (Suppl 3), 1–27. Nabuco de Araujo, P.H.X., Milanez de Campos, J.R. & Pêgo-Fernandes, P.M. (2016). 100 Years of History and Prospects in Thoracic Surgery. http://www.revistas.usp.br/revistadc/article/view/119664 (Last accessed 7.4.2019). National Health Services Improvements (2018). Revised Never Events policy and framework. https://improvement.nhs.uk/ documents/2265/Revised_Never_Events_policy_and_framework_FINAL.pdf (Last accessed 7.4.2019). National Patient Safety Agency (2009). WHO Surgical Safety Checklist. http://www.safesurg.org/uploads/1/0/9/0/1090835/ npsa_checklist.pdf (Last accessed 7.4.2019). Shields, M.D., Thomas, W., LoCicero, J., Reed, C.E. & Feins, R.H. (2009). 7th edn. General Thoracic Surgery. Philadelphia: Lippincott Williams and Wilkins & Wolters Kluwer. Sugarbaker, D.J., Bueno, R., Krasna, M., Mentzer, J.S. & Zellos, L. (2009). Adult Chest Surgery. New York: McGraw-Hill. Townsend, C.M., Beauchamp, R.D., Evers, B.M. & Mattox, K.L. (2016). 20th edn. Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice. Philadelphia: Elsevier.

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12 Cardiothoracic critical unit postoperative care Alan Ashworth and Fiona Wallace

Introduction Historically, cardiothoracic critical care developed from a need to provide advanced monitoring and organ support for patients who had recently undergone cardiothoracic surgery. While this remains at the core of cardiothoracic critical care, there has been significant diversification. A cardiothoracic critical care unit often cares for patients requiring extracorporeal life support (ECLS) for advanced respiratory and heart failure, transplant recipients and patients who have undergone interventional cardiological procedures. Cardiothoracic critical care units are staffed by highly skilled and specially trained multidisciplinary teams. Cardiothoracic anaesthetists and intensive care specialists work closely with surgeons, critical care nurses and other allied health professionals. Specific training in cardiothoracic critical care is now available via the Faculty of Intensive Care Medicine. The aim of this chapter is firstly to help the perioperative practitioner understand early postoperative management of patients in cardiothoracic critical care and secondly to provide a systematic overview of other commonly encountered issues.

Early postoperative management Most cardiothoracic critical care units have a rapid turnover of patients and the postoperative care of low-risk cases is a nurse-led, protocol-driven process. Over the past two decades, the management of patients following routine cardiac surgery has changed, with early extubation and rapid discharge allowing more efficient use of limited intensive care resources. These ‘fasttrack’ protocols have become possible due to improvements in cardiac surgical and anaesthetic techniques, improved myocardial protection, cardiopulmonary bypass techniques and improved management of bleeding. Anaesthesia for cardiac surgery traditionally involved high-dose opioid techniques, which contributed to prolonged ventilation postoperatively. ‘Fast-track’ cardiac anaesthesia

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employs a more balanced anaesthetic technique, using smaller doses of opioids and shorteracting muscle relaxants, thus allowing extubation within 8 hours. Early extubation is thought to reduce postoperative atelectasis as well as improving haemodynamics by restoring normal negative intrathoracic pressure. ‘Fast-track’ protocols also facilitate early ambulation, return to normal diet and a reduction in postoperative complications. This has led to reduced critical care and shorter length of hospital stay as well as a reduction in healthcare costs (Zhu, Lee & Chee 2012). ‘Fast-track’ cardiac surgery is not always successful. Predictors of failure of ‘fast-track’ protocols include: ●●

Impaired left ventricular function

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Previous cardiac surgery

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Extra cardiac arteriopathy

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Perioperative intra-aortic balloon pump

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Raised serum creatinine (>150mmol/l)

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Emergency and complex surgery

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Excessive postoperative bleeding

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Pre- and intra-operative use of inotropes

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Atrial arrhythmias (Constantinides et al. 2006).

Following surgery, the patient is transferred to the Intensive Care Unit (ICU), which should ideally be located close to the operating theatre. During transfer the patient should have continuous haemodynamic monitoring, and on arrival on the ICU there should be a comprehensive handover to the nursing and medical staff. In the UK, most patients who have undergone cardiac surgery will be admitted to the ICU sedated, intubated and ventilated. This allows a period of observation to ensure that the patient is cardiovascularly stable and not bleeding excessively. The aims of early postoperative management are: ●●

Adequate analgesia

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Normothermia

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Adequate oxygenation and ventilation

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Management of excessive bleeding

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Optimisation of haemodynamics

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Correction of electrolyte and metabolic derangements

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Control of arrhythmias.

Adequate analgesia With the move to ‘fast-track’ anaesthesia and the use of smaller doses of shorter-acting opioids, analgesia needs to be administered early in the postoperative period. Adequate analgesia is

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extremely important, following cardiac surgery, to reduce the risk of pulmonary and cardiovascular complications. There is evidence that patients with higher pain scores have a higher incidence of atelectasis, myocardial ischaemia and arrhythmias (Ziyaeifard, Azarfarin & Golzar 2014). The use of shorter-acting analgesics (such as fentanyl, alfentanil and remifentanil) can facilitate early extubation. In our Institution, we use an infusion of morphine or alfentanil started intra-operatively. Alfentanil is the analgesic of choice if the patient has preoperative renal dysfunction, or if they are at an advanced age or prolonged sedation is anticipated. Following extubation, the infusion is discontinued, and oral multimodal analgesia is administered in the form of regular (and as required) oxycodone, paracetamol and gabapentin. Side effects of intravenous opioids include nausea, vomiting, respiratory depression and somnolence; these are potential barriers to ‘fast-tracking’. Patient-controlled analgesia (PCA) can be useful for some patients as it provides good analgesia as well as improved patient autonomy and reduced anxiety. PCAs have also been demonstrated to reduce sedation and respiratory depression. The major disadvantage of PCA is a drop in blood analgesic concentrations while the patient is asleep. Non-steroidal anti-inflammatory drugs (NSAIDs) can be useful adjuncts in managing pain following cardiac surgery, as they improve pain scores and reduce opioid consumption and side effects. However, they should be used with caution, and are often avoided, due to the risk of acute kidney injury, upper gastrointestinal haemorrhage and platelet dysfunction.

Hypothermia Hypothermia is common following cardiac surgery and is due to vasodilatation, impaired thermoregulation, low ambient theatre temperatures and poor peripheral perfusion. Hypothermia may result in: ●●

Delayed extubation

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Increased risk of ventricular arrhythmias

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Increased systemic vascular resistance, which increases afterload and myocardial workload

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Shivering, resulting in increased oxygen consumption

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Impaired platelet function and coagulation cascade function.

The risk of hypothermia can be reduced by utilising forced-air warming blankets, heat and moisture exchangers on ventilator circuits and warmed intravenous fluids.

Adequate oxygenation and ventilation The aim of ventilation in the early postoperative period is to restore the functional residual capacity (FRC) by using lung protective ventilation and adequate levels of positive end-expiratory pressure (PEEP), which reduces shunt and improves gas exchange. Initial ventilation parameters should be tidal volumes of 6–8ml/kg predicted body weight, respiratory rate 10–15/minute, minimum of 5cmH2O PEEP and fraction of inspired oxygen of 0.5, aiming for PO2 greater than 8–10kPa and PCO2 between 4.5 and 6kPa. All patients will require supplemental oxygen to prevent hypoxia following extubation.

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Criteria for extubation: ●●

Adequate gas exchange on less than 50% oxygen ●●

pH 7.35–7.45

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PaO2 >8kPa.

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PaCO2 4.5–6 kPa.

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Oxygen saturations >95%.

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Normal electrolytes and metabolic status

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Haemodynamically stable

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Absence of excessive bleeding

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Temperature >36ºC

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Awake, alert and obeying commands

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Return of muscle strength and protective airway reflexes.

Pulmonary complications following cardiac surgery are common, with approximately 12% of patients experiencing an acute lung injury and about 1.5% requiring prolonged mechanical ventilation. These complications are associated with significant morbidity, mortality and increased length of stay. Postoperative pulmonary complications are due to a combination of peri-operative and patient factors. Patients presenting for cardiothoracic surgery often have smoking-related lung diseases and may have poor cardiac function. Intra-operative factors, such as positive pressure ventilation and lung handling, lead to a reduced functional residual capacity and vital capacity and atelectasis. The systemic inflammatory response to surgery and cardiopulmonary bypass leads to increased intravascular and extravascular lung water from increased capillary leakage due to the systemic inflammatory response. Postoperatively, an inability to cough and deep breathe, due to pain or weakness and poor mobility, also contribute to the inflammatory response. The resulting ventilation-perfusion mismatching and shunt leads to hypoxaemia. Atelectasis is the most common cause of hypoxaemia following cardiac surgery. Lung volumes are still significantly reduced up to a week following surgery. Regular physiotherapy and incentive spirometry should be used to reduce atelectasis. I-Cough is a simple, multidisciplinary postoperative pulmonary care programme developed in Boston and has been shown to reduce pulmonary complications and re-intubation (Cassidy et al. 2013). The i-Cough programme makes use of the following elements to prevent postoperative lung collapse: ●●

Incentive spirometry

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Coughing and deep breathing

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Oral hygiene

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Understanding, i.e. patient and staff education

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Getting out of bed at least three times each day

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Head of bed elevation (Cassidy et al. 2013).

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Management of excessive bleeding The key to avoiding excessive blood loss postoperatively is good surgical haemostasis. Excessive bleeding can be due to ‘surgical’ or ‘medical’ bleeding, or commonly a combination of the two. ‘Medical’ bleeding is secondary to coagulopathy such as defects in the coagulation cascade, platelet dysfunction, low fibrinogen or residual heparinisation. ‘Surgical’ bleeding requires a return to the operating theatre for re-exploration. Common sites of bleeding include vascular anastomoses, cannulation sites and small mediastinal arteries or veins. The management of excessive postoperative bleeding will be discussed more thoroughly in the ‘Haematology’ section of this chapter (see p. 258).

Optimisation of haemodynamics Following cardiac surgery, all patients require continuous haemodynamic monitoring to detect changes in blood pressure, intravascular volume status, heart rhythm and myocardial ischaemia. The most common cause of hypotension following cardiac surgery is hypovolaemia. Other causes include vasodilatation, which is common following cardiopulmonary bypass, and low cardiac output state. More than 20% of patients develop myocardial dysfunction following cardiac surgery. This ‘post-cardiotomy heart failure’ results in hypotension and inadequate oxygen delivery to tissue. Volatile anaesthetics and levosimendan (calcium sensitiser) show promise as cardioprotective agents (Mebazaa et al. 2010). Factors contributing to ‘post-cardiotomy heart failure’: ●●

Myocardial stunning

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Inadequate myocardial protection

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Reperfusion injury

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Myocardial ischaemia or infarction

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Incomplete revascularisation

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Metabolic derangement

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Mechanical or conduit issues

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Pulmonary hypertension and right ventricular failure.

Cardiac tamponade must be considered in patients with low cardiac output state following cardiac surgery. Beck’s triad of hypotension, distended neck veins and muffled heart sounds may be difficult to detect. Echocardiography can confirm but not rule out the diagnosis. Less common causes of hypotension in the postoperative period include dynamic left ventricular outflow obstruction, which typically occurs after aortic valve surgery in patients with left ventricular hypertrophy, acute paravalvular leak and tension pneumothorax. The aim of haemodynamic management is to ensure that there is adequate organ perfusion. Rapid assessment and diagnosis of the aetiology of hypotension is essential, followed by appropriate therapy, which may include fluid resuscitation, vasopressors, inotropes and insertion of an intra-aortic balloon pump. Management of these patients requires a good understanding of cardiovascular physiology.

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Preload should be optimised, and an optimum heart rate can be achieved by atrioventricular pacing. Preload is the left ventricular end-diastolic volume and can be assessed by central venous pressure, pulmonary capillary occlusion pressure and by echocardiography. The Frank-Starling principle describes the relationship between preload and cardiac output. Optimisation of preload may involve increasing intravascular volume with fluids or decreasing it with diuretics or renal replacement therapy. Fluid management post-cardiac surgery can be very challenging, due to altered haemodynamics and loss of fluid from the intravascular space caused by the systemic inflammatory response to cardiopulmonary bypass. If the patient has an optimum preload and normal or paced heart rhythm, the cause of the hypotension is impaired myocardial contractility, vasodilatation or both. Inotropic and vasopressor drugs may be used to optimise cardiac output and blood pressure. These measures will result in improved haemodynamics in most patients. However, in a small number of patients, some means of mechanical circulatory support may be indicated, such as an intra-aortic balloon pump or extracorporeal circulatory life support (see section in this chapter on ‘Life support systems’, p. 254).

Correction of electrolyte and metabolic abnormalities The postoperative course for most patients following cardiac surgery is characterised by predictable physiological derangements due to fluid and electrolyte shifts and cardiopulmonary bypass (see Table 12.1).

Table 12.1: The correction of electrolyte and metabolic abnormalities postoperatively according to the fluid and electrolyte shifts of the patient Electrolyte abnormality Risk factors/causes

Clinical signs

Investigations

Management

Hypokalaemia (K+ 5.5mmol/l)

Metabolic acidosis

Muscle weakness

Less common than hypokalaemia

Intra-op cardioplegia

Paralysis

ECG – peaked T waves, small P waves, wide QRS complexes Serum U+Es

Drugs

Assessment of intravascular volume

Haemolysis Adrenal insufficiency

Urine output

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Correct acidosis Calcium gluconate Insulin 10iu/50% dextrose infusion Frusemide Salbutamol nebuliser Renal replacement therapy

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Hypomagnesaemia (Mg