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Obstetric Anesthesia A Case-Based and Visual Approach Thomas L. Archer Editor Foreword by Jonathan L. Benumof
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Obstetric Anesthesia
Thomas L. Archer Editor
Obstetric Anesthesia A Case-Based and Visual Approach
Editor Thomas L. Archer, MD, MBA Department of Anesthesiology 2008–2015 University of California San Diego School of Medicine San Diego, CA USA
ISBN 978-3-030-26476-5 ISBN 978-3-030-26478-9 (eBook) https://doi.org/10.1007/978-3-030-26478-9 © Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland
Foreword
I know very well that Dr. Thomas L. Archer is a very good writer of clinical, case- based, scientifically well-grounded, teaching book chapters. He wrote six wonderful chapters for my single-edited Clinical Anesthesiology: Lessons Learned from Morbidity and Mortality Conferences book (published by Springer). My book has enjoyed a great deal of success over the past 5 years, and I think the best part of the book was Dr. Archer’s six obstetric anesthesia chapters. I have no doubt that the 32 case-based chapters in his book Obstetric Anesthesia: A Case-Based and Visual Approach will all be of the very high quality that he has already demonstrated is the norm for him. Dr. Archer writes great case-based chapters because he is a very good clinician- scientist-teacher. He was Chief of the Obstetric Anesthesia Division at UCSD Medical Center for many years and was widely respected by everyone for his clinical care. He is scientific in his clinical approach, and, as such, his clinical approach is strongly evidence based. He is also a great teacher; he is clear, organized, up-to- date, and, most importantly, passionate about communicating well and interestingly. Finally, the book itself is very complete and well organized and, as such, makes a great contribution to the education of all who are interested in obstetric anesthesia. Jonathan L. Benumof, MD Department of Anesthesiology University of California San Diego School of Medicine San Diego, CA USA
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Preface
I dedicate this book to Jonathan L. Benumof, MD, who has recently retired from a long and distinguished career as physician, teacher, researcher, innovator, and wonderful role model in anesthesia care, teaching, and investigation. I had the good fortune of having Dr. Benumof as a teacher and role model during my anesthesia residency at UCSD in the late 1970s, and I reconnected with him when I served as Director of Obstetric Anesthesia at UCSD from 2008 until 2015. When I was on the faculty myself, he taught me an immense amount about medical writing and the construction of helpful illustrations as I wrote six chapters for one of his many books, and his calm, understated, respectful, and always reasonable demeanor has always served me as an example of how a physician should carry himself. One of his many early contributions to my education and development occurred as I heard him talk about the importance of “patient buy-in” when performing possibly uncomfortable procedures such as awake intubations. His use of that term (invented by him?) brought me early to understand that respect for the patient’s experience, understanding, and worldview is an essential aspect of excellent medical care, both from a humanistic and egalitarian point of view and because, practically, if the patient “buys in to” the need for the uncomfortable procedure, everything will go much easier for everyone—including the patient’s physicians! So Dr. Benumof would frequently have us residents literally sit down with the patient and explain, fully and empathetically, what was going on and why the possibly uncomfortable procedure was necessary, and this experience of getting “patient buy-in” provided me early on with an example of “patient-centered care,” although, of course, it was not called that at the time. When I was a resident, Dr. Benumof profoundly impressed me as well when I learned that he was learning the skill of fiber optic intubation from a pulmonologist at UCSD. I was impressed that he had the vision and humility to seek out new skills outside his “comfort zone” and thereby continue to grow, learn, and evolve even though he was already a highly regarded member of the Anesthesia Faculty. So it was in that spirit of “trying something new” that I started to work with these three emerging technologies presented in this book:
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1. The use of pre-procedural ultrasound to facilitate neuraxial block placement, especially in obese patients and those with spinal pathology 2. The use of hand-held (bedside, “point-of-care”) transthoracic echocardiography for guiding maternal resuscitation 3. The use of electrical cardiometry for trending maternal cardiac output, in order to detect inferior vena cava compression and give an early warning of possible developing fetal hypoxia Even though I have “drunk the Kool-Aid” with respect to the usefulness of all three of these technologies, I recognize that all of them are not fully accepted within the anesthesiology community. All I ask is that you remain open to their possible utility in your practice. In this book, I have tried to create realistic scenarios in which there is often time pressure, lots of labor pain, multiple priorities and trade-offs, incomplete information, false assumptions, general uncertainty, imperfect results, and—yes—scenarios in which people make mistakes. By including interactions and even conversations with patients and other staff in the cases, I have also tried to convey a feeling for how obstetric anesthesia is very different from other subspecialties of anesthesia care, and that in obstetric anesthesia—even more than in other anesthetic subspecialties—good interpersonal relations and communication skills as well as medical knowledge and skill are essential to success. Furthermore, we can all be trained to improve our communication skills, and I have tried to include some concrete techniques for improving the patient’s (and physician’s) medical care experience. The colorful (and at times fanciful) figures which I have drawn are not meant to be anatomically correct, definitive, or completely “accurate” in any sense. Rather, they are impressionistic abstractions meant to dramatize and clarify concepts and relationships and to inspire further study and research. The majority of the material I present in this book is well accepted in obstetric and obstetric anesthesia circles, but—in the spirit of adventure described above—I have also included some emerging knowledge and speculations which, I believe, merit further research. As can be seen from the Table of Contents, the book is organized around several themes: 1 . Focusing on the patient’s experience, worldview, and preferences 2. Smooth, respectful, and collegial functioning of the obstetric care team and the importance of good interpersonal skills 3. Physiology of pregnancy and labor and the many threats to fetal oxygenation, both with and without anesthetic interventions 4. Causes and management of obstetric hemorrhage 5. Management of four unexpected and relatively uncommon obstetric crises 6. Management of morbidly obese patients and those with known placenta accreta 7. Recognition and management of common technical problems in obtaining successful neuraxial anesthesia
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8 . Prevention and management of anesthetic complications and mistakes 9. Finally, a presentation of the theory that one cause of dysfunctional labor may be poor uterine perfusion and myometrial hypoxia due to inferior vena cava compression The cases in this book are all fictional but are based on my experience and study over many years at different institutions. Likewise, all of the “data” or “simulated data” from electrical cardiometry are fictional—but are based on my experience using the ICON electrical cardiometry device manufactured by Osypka Medical, Inc. Some of the simulated data may resemble published data (which was, indeed, obtained from actual patients), and the simulated data is not meant to be definitive, comprehensive, or to convey settled truth but rather to describe phenomena which I have observed in real patients and to stimulate further research. The hemodynamic data derived from the LiDCO system (which requires an arterial line) and the one magnetic resonance image are real patient data, de-identified and used with the permission of the University of Texas Health Science Center, San Antonio. I hope you enjoy the book and find it of use in your care of patients, in teaching, and in planning your research. June 25, 2019
Thomas L. Archer, MD, MBA
Acknowledgments
I would like to thank the following people who have immensely enriched my life: Steve Hebert, MD, for his friendship, deep clinical experience, excellent judgment, calm and pleasant manner, and finely honed and continual concern for the welfare of the patients and staff. Erin Martin, MD, for her thoughtfulness with patients and colleagues, her hard work as a fellow, her excellent clinical judgment and skills, her fine writing and—lastly—for her strength and intellectual honesty to disagree with people in authority when they champion either mistaken orthodoxy or wild ideas. Jerasimos Ballas, MD, for his hard work, enthusiasm, fine patient care, and contributions to the ideas behind the “COOL Study.” Andrew Hull, MD, for his wit, wonderful teaching at Board Rounds, and all- around incisive intelligence and also for encouraging Dr. Ballas to work with me for his Maternal Fetal Medicine thesis.
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Part I Pregnancy, Anesthesia and Threats to Fetal Oxygenation 1 Normal Pregnancy, Labor, and Delivery––Without Epidural Analgesia���������������������������������������������������������������������������������� 3 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 3 Lessons Learned�������������������������������������������������������������������������������������� 4 Lesson 1 ���������������������������������������������������������������������������������������������� 4 Lesson 2 ���������������������������������������������������������������������������������������������� 7 Lesson 3 ���������������������������������������������������������������������������������������������� 9 Lesson 4 ���������������������������������������������������������������������������������������������� 14 Lesson 5 ���������������������������������������������������������������������������������������������� 14 References������������������������������������������������������������������������������������������������ 17 2 Neuraxial Anesthesia and the Supine Position Cause Non-reassuring Fetal Status�������������������������������������������������������������������� 19 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 19 Lessons Learned�������������������������������������������������������������������������������������� 20 Lesson 1 ���������������������������������������������������������������������������������������������� 20 Lesson 2 ���������������������������������������������������������������������������������������������� 21 Lesson 3 ���������������������������������������������������������������������������������������������� 21 Lesson 4 ���������������������������������������������������������������������������������������������� 22 Lesson 5 ���������������������������������������������������������������������������������������������� 22 Lesson 6 ���������������������������������������������������������������������������������������������� 22 Lesson 7 ���������������������������������������������������������������������������������������������� 23 Lesson 8 ���������������������������������������������������������������������������������������������� 24 Lesson 9 ���������������������������������������������������������������������������������������������� 25 Lesson 10 �������������������������������������������������������������������������������������������� 26 References������������������������������������������������������������������������������������������������ 26
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3 Hyperstimulation ������������������������������������������������������������������������������������ 29 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 29 Lessons Learned�������������������������������������������������������������������������������������� 30 Lesson 1 ���������������������������������������������������������������������������������������������� 30 Lesson 2 ���������������������������������������������������������������������������������������������� 30 Lesson 3 ���������������������������������������������������������������������������������������������� 31 Lesson 4 ���������������������������������������������������������������������������������������������� 31 Lesson 5 ���������������������������������������������������������������������������������������������� 32 Lesson 6 ���������������������������������������������������������������������������������������������� 33 Lesson 7 ���������������������������������������������������������������������������������������������� 33 Lesson 8 ���������������������������������������������������������������������������������������������� 33 Lesson 9 ���������������������������������������������������������������������������������������������� 34 Lesson 10 �������������������������������������������������������������������������������������������� 34 Lesson 11 �������������������������������������������������������������������������������������������� 35 4 Scheduled Repeat Cesarean Delivery���������������������������������������������������� 39 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 39 Lessons Learned�������������������������������������������������������������������������������������� 40 Lesson 1 ���������������������������������������������������������������������������������������������� 40 Lesson 2 ���������������������������������������������������������������������������������������������� 40 Lesson 3 ���������������������������������������������������������������������������������������������� 42 Lesson 4 ���������������������������������������������������������������������������������������������� 42 Lesson 5 ���������������������������������������������������������������������������������������������� 42 Lesson 6 ���������������������������������������������������������������������������������������������� 42 Lesson 7 ���������������������������������������������������������������������������������������������� 43 Lesson 8 ���������������������������������������������������������������������������������������������� 43 Lesson 9 ���������������������������������������������������������������������������������������������� 46 Lesson 10 �������������������������������������������������������������������������������������������� 49 Lesson 11 �������������������������������������������������������������������������������������������� 49 Lesson 12 �������������������������������������������������������������������������������������������� 49 Lesson 13 �������������������������������������������������������������������������������������������� 49 Lesson 14 �������������������������������������������������������������������������������������������� 50 References������������������������������������������������������������������������������������������������ 50 Part II Postpartum Hemorrhage 5 Uterine Atony: The Most Common Cause of Postpartum Hemorrhage���������������������������������������������������������������������������������������������� 53 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 53 Lessons Learned�������������������������������������������������������������������������������������� 57 Lesson 1 ���������������������������������������������������������������������������������������������� 57 Lesson 2 ���������������������������������������������������������������������������������������������� 58 Lesson 3 ���������������������������������������������������������������������������������������������� 58
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Lesson 4 ���������������������������������������������������������������������������������������������� 58 Lesson 5 ���������������������������������������������������������������������������������������������� 58 Lesson 6 ���������������������������������������������������������������������������������������������� 59 Lesson 7 ���������������������������������������������������������������������������������������������� 59 Lesson 8 ���������������������������������������������������������������������������������������������� 59 Lesson 9 ���������������������������������������������������������������������������������������������� 59 Lesson 10 �������������������������������������������������������������������������������������������� 59 Lesson 11 �������������������������������������������������������������������������������������������� 60 Lesson 12 �������������������������������������������������������������������������������������������� 60 Lesson 13 �������������������������������������������������������������������������������������������� 60 Lesson 14 �������������������������������������������������������������������������������������������� 61 Lesson 15 �������������������������������������������������������������������������������������������� 61 Lesson 16 �������������������������������������������������������������������������������������������� 61 Lesson 17 �������������������������������������������������������������������������������������������� 61 Lesson 18 �������������������������������������������������������������������������������������������� 61 Lesson 19 �������������������������������������������������������������������������������������������� 62 Lesson 20 �������������������������������������������������������������������������������������������� 62 Lesson 21 �������������������������������������������������������������������������������������������� 62 Lesson 22 �������������������������������������������������������������������������������������������� 62 References������������������������������������������������������������������������������������������������ 67 6 Hypovolemic Shock���������������������������������������������������������������������������������� 69 Thomas L. Archer, David J. Elkin, and Michael K. Fujinaka Case Presentation ������������������������������������������������������������������������������������ 69 Lessons Learned�������������������������������������������������������������������������������������� 71 Lesson 1 ���������������������������������������������������������������������������������������������� 71 Lesson 2 ���������������������������������������������������������������������������������������������� 71 Lesson 3 ���������������������������������������������������������������������������������������������� 72 Lesson 4 ���������������������������������������������������������������������������������������������� 72 Lesson 5 ���������������������������������������������������������������������������������������������� 72 Lesson 6 ���������������������������������������������������������������������������������������������� 73 Lesson 7 ���������������������������������������������������������������������������������������������� 73 Lesson 8 ���������������������������������������������������������������������������������������������� 75 Lesson 9 ���������������������������������������������������������������������������������������������� 75 Lesson 10 �������������������������������������������������������������������������������������������� 75 Lesson 11 �������������������������������������������������������������������������������������������� 75 Reference ������������������������������������������������������������������������������������������������ 78 7 A Traumatic Cesarean Delivery with Consumptive Coagulopathy�������������������������������������������������������������������������������������������� 79 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 79 Lessons Learned�������������������������������������������������������������������������������������� 82 Lesson 1 ���������������������������������������������������������������������������������������������� 82 Lesson 2 ���������������������������������������������������������������������������������������������� 82 Lesson 3 ���������������������������������������������������������������������������������������������� 83
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Lesson 4 ���������������������������������������������������������������������������������������������� 83 Lesson 5 ���������������������������������������������������������������������������������������������� 83 Lesson 6 ���������������������������������������������������������������������������������������������� 83 Lesson 7 ���������������������������������������������������������������������������������������������� 84 Lesson 8 ���������������������������������������������������������������������������������������������� 88 Lesson 9 ���������������������������������������������������������������������������������������������� 89 Lesson 10 �������������������������������������������������������������������������������������������� 89 Lesson 11 �������������������������������������������������������������������������������������������� 90 Lesson 12 �������������������������������������������������������������������������������������������� 90 Lesson 13 �������������������������������������������������������������������������������������������� 90 Lesson 14 �������������������������������������������������������������������������������������������� 91 Lesson 15 �������������������������������������������������������������������������������������������� 91 Lesson 16 �������������������������������������������������������������������������������������������� 91 Lesson 17 �������������������������������������������������������������������������������������������� 91 Lesson 18 �������������������������������������������������������������������������������������������� 92 Lesson 19 �������������������������������������������������������������������������������������������� 92 Lesson 20 �������������������������������������������������������������������������������������������� 92 Lesson 21 �������������������������������������������������������������������������������������������� 92 Lesson 22 �������������������������������������������������������������������������������������������� 92 Lesson 23 �������������������������������������������������������������������������������������������� 93 Lesson 24 �������������������������������������������������������������������������������������������� 93 Lesson 25 �������������������������������������������������������������������������������������������� 93 Lesson 26 �������������������������������������������������������������������������������������������� 93 Lesson 27 �������������������������������������������������������������������������������������������� 93 Lesson 28 �������������������������������������������������������������������������������������������� 94 Lesson 29 �������������������������������������������������������������������������������������������� 94 Lesson 30 �������������������������������������������������������������������������������������������� 94 Lesson 31 �������������������������������������������������������������������������������������������� 94 Reference ������������������������������������������������������������������������������������������������ 97 8 Trial of Labor After Cesarean Delivery (TOLAC), with Uterine Dehiscence and Emergency Cesarean Delivery Under General Anesthesia ������������������������������������������������������ 99 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 99 Lessons Learned�������������������������������������������������������������������������������������� 101 Lesson 1 ���������������������������������������������������������������������������������������������� 101 Lesson 2 ���������������������������������������������������������������������������������������������� 101 Lesson 3 ���������������������������������������������������������������������������������������������� 103 Lesson 4 ���������������������������������������������������������������������������������������������� 104 Lesson 5 ���������������������������������������������������������������������������������������������� 104 Lesson 6 ���������������������������������������������������������������������������������������������� 104 Lesson 7 ���������������������������������������������������������������������������������������������� 104 Lesson 8 ���������������������������������������������������������������������������������������������� 104 Lesson 9 ���������������������������������������������������������������������������������������������� 105
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Lesson 10 �������������������������������������������������������������������������������������������� 105 Lesson 11 �������������������������������������������������������������������������������������������� 106 References������������������������������������������������������������������������������������������������ 106 Part III More Obstetric Crises 9 High Spinal ���������������������������������������������������������������������������������������������� 109 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 109 Lessons Learned�������������������������������������������������������������������������������������� 112 Lesson 1 ���������������������������������������������������������������������������������������������� 112 Lesson 2 ���������������������������������������������������������������������������������������������� 112 Lesson 3 ���������������������������������������������������������������������������������������������� 112 Lesson 4 ���������������������������������������������������������������������������������������������� 113 Lesson 5 ���������������������������������������������������������������������������������������������� 114 Lesson 6 ���������������������������������������������������������������������������������������������� 115 Lesson 7 ���������������������������������������������������������������������������������������������� 116 Lesson 8 ���������������������������������������������������������������������������������������������� 117 Lesson 9 ���������������������������������������������������������������������������������������������� 117 Lesson 10 �������������������������������������������������������������������������������������������� 117 References������������������������������������������������������������������������������������������������ 117 10 Prolapsed Umbilical Cord ���������������������������������������������������������������������� 119 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 119 Lessons Learned�������������������������������������������������������������������������������������� 120 Lesson 1 ���������������������������������������������������������������������������������������������� 120 Lesson 2 ���������������������������������������������������������������������������������������������� 120 Lesson 3 ���������������������������������������������������������������������������������������������� 122 11 A Patient Delivers Vaginally After an Eclamptic Seizure�������������������� 123 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 123 Lessons Learned�������������������������������������������������������������������������������������� 125 Lesson 1 ���������������������������������������������������������������������������������������������� 125 Lesson 2 ���������������������������������������������������������������������������������������������� 126 Lesson 3 ���������������������������������������������������������������������������������������������� 126 Lesson 4 ���������������������������������������������������������������������������������������������� 126 Lesson 5 ���������������������������������������������������������������������������������������������� 126 Lesson 6 ���������������������������������������������������������������������������������������������� 127 Lesson 7 ���������������������������������������������������������������������������������������������� 128 Lesson 8 ���������������������������������������������������������������������������������������������� 129 Lesson 9 ���������������������������������������������������������������������������������������������� 129 Lesson 10 �������������������������������������������������������������������������������������������� 131 Lesson 11 �������������������������������������������������������������������������������������������� 131 Lesson 12 �������������������������������������������������������������������������������������������� 132
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Lesson 13 �������������������������������������������������������������������������������������������� 132 Lesson 14 �������������������������������������������������������������������������������������������� 132 Lesson 15 �������������������������������������������������������������������������������������������� 132 Lesson 16 �������������������������������������������������������������������������������������������� 133 Lesson 17 �������������������������������������������������������������������������������������������� 133 Reference ������������������������������������������������������������������������������������������������ 133 12 Cesarean Delivery Under General Anesthesia in a Septic Patient�������� 135 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 135 Lessons Learned�������������������������������������������������������������������������������������� 136 Lesson 1 ���������������������������������������������������������������������������������������������� 136 Lesson 2 ���������������������������������������������������������������������������������������������� 136 Lesson 3 ���������������������������������������������������������������������������������������������� 137 Lesson 4 ���������������������������������������������������������������������������������������������� 137 Lesson 5 ���������������������������������������������������������������������������������������������� 137 Lesson 6 ���������������������������������������������������������������������������������������������� 140 Reference ������������������������������������������������������������������������������������������������ 140 Part IV More Challenging Cases 13 Morbidly Obese Preeclamptic Patient with Difficult IV Access for Urgent Cesarean Delivery ���������������������������������������������������� 143 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 143 Lessons Learned�������������������������������������������������������������������������������������� 145 Lesson 1 ���������������������������������������������������������������������������������������������� 145 Lesson 2 ���������������������������������������������������������������������������������������������� 145 Lesson 3 ���������������������������������������������������������������������������������������������� 147 Lesson 4 ���������������������������������������������������������������������������������������������� 148 Lesson 5 ���������������������������������������������������������������������������������������������� 155 Lesson 6 ���������������������������������������������������������������������������������������������� 155 Lesson 7 ���������������������������������������������������������������������������������������������� 158 Lesson 8 ���������������������������������������������������������������������������������������������� 158 Lesson 9 ���������������������������������������������������������������������������������������������� 158 Lesson 10 �������������������������������������������������������������������������������������������� 159 Lesson 11 �������������������������������������������������������������������������������������������� 162 Lesson 12 �������������������������������������������������������������������������������������������� 162 Lesson 13 �������������������������������������������������������������������������������������������� 167 Lesson 14 �������������������������������������������������������������������������������������������� 167 Lesson 15 �������������������������������������������������������������������������������������������� 167 References������������������������������������������������������������������������������������������������ 167 14 Patient with Known Placenta Previa and Accreta for Elective Cesarean Hysterectomy������������������������������������������������������ 169 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 169
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Lessons Learned�������������������������������������������������������������������������������������� 173 Lesson 1 ���������������������������������������������������������������������������������������������� 173 Lesson 2 ���������������������������������������������������������������������������������������������� 173 Lesson 3 ���������������������������������������������������������������������������������������������� 173 Lesson 4 ���������������������������������������������������������������������������������������������� 175 Lesson 5 ���������������������������������������������������������������������������������������������� 175 Lesson 6 ���������������������������������������������������������������������������������������������� 177 Lesson 7 ���������������������������������������������������������������������������������������������� 177 References������������������������������������������������������������������������������������������������ 177 15 A Patient with Severe Idiopathic Pulmonary Hypertension Delivers Her Fourth Child���������������������������������������������� 179 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 179 Lessons Learned�������������������������������������������������������������������������������������� 182 Lesson 1 ���������������������������������������������������������������������������������������������� 182 Lesson 2 ���������������������������������������������������������������������������������������������� 186 Lesson 3 ���������������������������������������������������������������������������������������������� 187 Lesson 4 ���������������������������������������������������������������������������������������������� 187 Lesson 5 ���������������������������������������������������������������������������������������������� 187 Lesson 6 ���������������������������������������������������������������������������������������������� 187 Lesson 7 ���������������������������������������������������������������������������������������������� 187 Lesson 8 ���������������������������������������������������������������������������������������������� 187 Reference ������������������������������������������������������������������������������������������������ 188 Part V Successful Neuraxial Anesthesia 16 Fooling Ourselves: Intravenous Fentanyl Creates the Illusion of a Successful Epidural���������������������������������������� 191 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 191 Lessons Learned�������������������������������������������������������������������������������������� 192 Lesson 1 ���������������������������������������������������������������������������������������������� 192 Lesson 2 ���������������������������������������������������������������������������������������������� 192 Lesson 3 ���������������������������������������������������������������������������������������������� 193 Lesson 4 ���������������������������������������������������������������������������������������������� 193 Lesson 5 ���������������������������������������������������������������������������������������������� 193 17 What Not to Do During Uterine Contractions: Three Vignettes with One Simple Lesson���������������������������������������������� 195 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 195 Lessons Learned�������������������������������������������������������������������������������������� 196 Lesson 1 ���������������������������������������������������������������������������������������������� 196 18 A One-Sided Epidural ���������������������������������������������������������������������������� 199 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 199
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Lessons Learned�������������������������������������������������������������������������������������� 200 Lesson 1 ���������������������������������������������������������������������������������������������� 200 Lesson 2 ���������������������������������������������������������������������������������������������� 200 Lesson 3 ���������������������������������������������������������������������������������������������� 203 Lesson 4 ���������������������������������������������������������������������������������������������� 203 Lesson 5 ���������������������������������������������������������������������������������������������� 205 Lesson 6 ���������������������������������������������������������������������������������������������� 205 References������������������������������������������������������������������������������������������������ 207 19 Dosing an Epidural for “Back Labor.”�������������������������������������������������� 209 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 209 Lessons Learned�������������������������������������������������������������������������������������� 210 Lesson 1 ���������������������������������������������������������������������������������������������� 210 Lesson 2 ���������������������������������������������������������������������������������������������� 210 Lesson 3 ���������������������������������������������������������������������������������������������� 210 Lesson 4 ���������������������������������������������������������������������������������������������� 210 Lesson 5 ���������������������������������������������������������������������������������������������� 212 Lesson 6 ���������������������������������������������������������������������������������������������� 212 20 Management of a Patient with an Unsatisfactory Labor Epidural, Now Going for Cesarean Delivery ���������������������������� 213 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 213 Lessons Learned�������������������������������������������������������������������������������������� 214 Lesson 1 ���������������������������������������������������������������������������������������������� 214 Lesson 2 ���������������������������������������������������������������������������������������������� 214 Lesson 3 ���������������������������������������������������������������������������������������������� 216 21 Rescuing a Low Spinal���������������������������������������������������������������������������� 217 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 217 Lessons Learned�������������������������������������������������������������������������������������� 218 Lesson 1 ���������������������������������������������������������������������������������������������� 218 Lesson 2 ���������������������������������������������������������������������������������������������� 218 Lesson 3 ���������������������������������������������������������������������������������������������� 218 References������������������������������������������������������������������������������������������������ 222 22 A Failed Epidural Followed by a Failed Spinal (Part 1)���������������������� 223 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 223 Lessons Learned�������������������������������������������������������������������������������������� 224 Lesson 1 ���������������������������������������������������������������������������������������������� 224 Lesson 2 ���������������������������������������������������������������������������������������������� 227 Lesson 3 ���������������������������������������������������������������������������������������������� 227 Lesson 4 ���������������������������������������������������������������������������������������������� 227 Lesson 5 ���������������������������������������������������������������������������������������������� 229
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Lesson 6 ���������������������������������������������������������������������������������������������� 229 Lesson 7 ���������������������������������������������������������������������������������������������� 229 Lesson 8 ���������������������������������������������������������������������������������������������� 229 Lesson 9 ���������������������������������������������������������������������������������������������� 230 Lesson 10 �������������������������������������������������������������������������������������������� 231 23 A Failed Epidural Followed by a Failed Spinal (Part 2)���������������������� 233 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 233 Lessons Learned�������������������������������������������������������������������������������������� 234 Lesson 1 ���������������������������������������������������������������������������������������������� 234 Lesson 2 ���������������������������������������������������������������������������������������������� 234 Lesson 3 ���������������������������������������������������������������������������������������������� 235 Lesson 4 ���������������������������������������������������������������������������������������������� 236 Lesson 5 ���������������������������������������������������������������������������������������������� 236 Lesson 6 ���������������������������������������������������������������������������������������������� 236 Lesson 7 ���������������������������������������������������������������������������������������������� 239 Lesson 8 ���������������������������������������������������������������������������������������������� 239 Lesson 9 ���������������������������������������������������������������������������������������������� 239 Lesson 10 �������������������������������������������������������������������������������������������� 239 References������������������������������������������������������������������������������������������������ 239 24 Labor Epidural for a Patient with Scoliosis������������������������������������������ 241 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 241 Lessons Learned�������������������������������������������������������������������������������������� 242 Lesson 1 ���������������������������������������������������������������������������������������������� 242 Lesson 2 ���������������������������������������������������������������������������������������������� 243 Lesson 3 ���������������������������������������������������������������������������������������������� 246 Lesson 4 ���������������������������������������������������������������������������������������������� 249 Reference ������������������������������������������������������������������������������������������������ 250 Part VI Anesthetic Complications 25 Wrong Medication ���������������������������������������������������������������������������������� 253 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 253 Lessons Learned�������������������������������������������������������������������������������������� 254 Lesson 1 ���������������������������������������������������������������������������������������������� 254 References������������������������������������������������������������������������������������������������ 255 26 Headache After Dural Puncture with an Epidural Needle������������������ 257 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 257 Lessons Learned�������������������������������������������������������������������������������������� 258 Lesson 1 ���������������������������������������������������������������������������������������������� 258 Lesson 2 ���������������������������������������������������������������������������������������������� 258
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Lesson 3 ���������������������������������������������������������������������������������������������� 259 Lesson 4 ���������������������������������������������������������������������������������������������� 259 Lesson 5 ���������������������������������������������������������������������������������������������� 259 Lesson 6 ���������������������������������������������������������������������������������������������� 259 Lesson 7 ���������������������������������������������������������������������������������������������� 259 Lesson 8 ���������������������������������������������������������������������������������������������� 260 Lesson 9 ���������������������������������������������������������������������������������������������� 260 Lesson 10 �������������������������������������������������������������������������������������������� 260 Lesson 11 �������������������������������������������������������������������������������������������� 260 Lesson 12 �������������������������������������������������������������������������������������������� 262 Reference ������������������������������������������������������������������������������������������������ 263 27 Neurological Deficit After Neuraxial Analgesia for Labor and Vaginal Delivery�������������������������������������������������������������� 265 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 265 Lessons Learned�������������������������������������������������������������������������������������� 266 Lesson 1 ���������������������������������������������������������������������������������������������� 266 Lesson 2 ���������������������������������������������������������������������������������������������� 266 Lesson 3 ���������������������������������������������������������������������������������������������� 266 Lesson 4 ���������������������������������������������������������������������������������������������� 266 References������������������������������������������������������������������������������������������������ 270 28 Left Sciatic Neuropathy After Cesarean Delivery in an Obese, Diabetic Patient������������������������������������������������������������������ 271 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 271 Lessons Learned�������������������������������������������������������������������������������������� 272 Lesson 1 ���������������������������������������������������������������������������������������������� 272 Lesson 2 ���������������������������������������������������������������������������������������������� 272 Lesson 3 ���������������������������������������������������������������������������������������������� 272 Reference ������������������������������������������������������������������������������������������������ 273 29 Vasopressin, Used as a Vasopressor During Cystoscopy, Causes Non-reassuring Fetal Status������������������������������������������������������ 275 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 275 Lessons Learned�������������������������������������������������������������������������������������� 276 Lesson 1 ���������������������������������������������������������������������������������������������� 276 Lesson 2 ���������������������������������������������������������������������������������������������� 276 Lesson 3 ���������������������������������������������������������������������������������������������� 277 30 Emergency Cesarean Delivery After Repair of an Ankle Fracture�������������������������������������������������������������������������������� 279 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 279 Lessons Learned�������������������������������������������������������������������������������������� 280
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Lesson 1 ���������������������������������������������������������������������������������������������� 280 Lesson 2 ���������������������������������������������������������������������������������������������� 281 Lesson 3 ���������������������������������������������������������������������������������������������� 281 Lesson 4 ���������������������������������������������������������������������������������������������� 282 Lesson 5 ���������������������������������������������������������������������������������������������� 282 Lesson 6 ���������������������������������������������������������������������������������������������� 283 Lesson 7 ���������������������������������������������������������������������������������������������� 283 Lesson 8 ���������������������������������������������������������������������������������������������� 283 Lesson 9 ���������������������������������������������������������������������������������������������� 283 Lesson 10 �������������������������������������������������������������������������������������������� 283 Lesson 11 �������������������������������������������������������������������������������������������� 284 Lesson 12 �������������������������������������������������������������������������������������������� 286 References������������������������������������������������������������������������������������������������ 286 31 Another Spinal Mishap��������������������������������������������������������������������������� 287 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 287 Lessons Learned�������������������������������������������������������������������������������������� 288 Lesson 1 ���������������������������������������������������������������������������������������������� 288 Lesson 2 ���������������������������������������������������������������������������������������������� 288 Lesson 3 ���������������������������������������������������������������������������������������������� 288 Lesson 4 ���������������������������������������������������������������������������������������������� 289 Lesson 5 ���������������������������������������������������������������������������������������������� 289 Lesson 6 ���������������������������������������������������������������������������������������������� 289 Part VII Dysfunctional Labor and Uterine Oxygenation: A Theory 32 Cardiac Output-Guided Resuscitation of the Uterus: An Obese Patient Has Dysfunctional Labor Which Resolves with Position Change. Coincidence or Possible Therapy?������������������������������������������������������������������������������������ 293 Thomas L. Archer Case Presentation ������������������������������������������������������������������������������������ 293 Lessons Learned�������������������������������������������������������������������������������������� 295 Lesson 1 ���������������������������������������������������������������������������������������������� 295 Lesson 2 ���������������������������������������������������������������������������������������������� 295 Lesson 3 ���������������������������������������������������������������������������������������������� 296 Lesson 4 ���������������������������������������������������������������������������������������������� 296 Lesson 5 ���������������������������������������������������������������������������������������������� 297 References������������������������������������������������������������������������������������������������ 301 Index������������������������������������������������������������������������������������������������������������������ 303
Contributors
Thomas L. Archer, MD, MBA Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA David J. Elkin, MD Department of Emergency Medicine, Maimonides Medical Center, Brooklyn, NY, USA Michael K. Fujinaka, MD, QME, FIPP Apex Pain and Wellness, Foster City, CA, USA
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Part I
Pregnancy, Anesthesia and Threats to Fetal Oxygenation
Chapter 1
Normal Pregnancy, Labor, and Delivery––Without Epidural Analgesia Thomas L. Archer
Case Presentation A 20-year-old woman, G1P0, presents to Labor & Delivery (L&D) in active labor at 40 weeks estimated gestational age (L-1). She has painful uterine contractions, and her cervix is 4 cm dilated on admission. The nurses easily start an IV in one of the prominent superficial veins of her forearm, and they position the patient in bed tilted toward her left side. The obstetric anesthesiologist visits the patient as a matter of routine—to introduce herself to the patient, to find out basic information about her medical history, and to answer any questions she may have about the options for pain relief during labor. The patient thanks the anesthesiologist for the visit, but says she is going to try to “go natural” (L-2). The first stage of labor is very painful, and the patient accepts a small dose of intravenous nalbuphine for analgesia, but continues to decline an epidural (L-3). Soon, her cervix becomes fully dilated, and she pushes or “bears down” with each contraction, performing a Valsalva maneuver to push the baby head first down the birth canal. After a painful and exhausting second stage of labor, she delivers a healthy baby girl and is joyful to be a new mother! The tired but happy mother receives her vigorous baby from the nurses and gets skin-to- skin contact with the baby immediately. The baby makes sucking movements with her mouth, and the mother puts the baby to her breast (L-4). The nurses check the uterine fundus and it is firm. Oxytocin is added to the mother’s intravenous fluid and infused at a low rate (L-5).
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_1
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T. L. Archer
Lessons Learned Lesson 1 Some of the physiological changes of normal pregnancy are shown in Boxes 1.1 and 1.2 [1] as well as Table 1.1 [2], while Fig. 1.1 graphically summarizes the hemodynamics of normal pregnancy before the onset of labor. The increased metabolic demands of pregnancy increase maternal oxygen consumption and cardiac output, and the growing uterus and placenta provide another path for blood flow, thereby lowering total systemic vascular resistance. The heart remodels Table 1.1 Arterial blood gas (ABG) changes in normal pregnancy
ABGs Nonpregnant PaCO2 (mm Hg) 40 PaO2 (mm Hg) 100 pH 7.40 HCO3− (mEq/L) 24
Pregnant at term 30 103 7.44 18
At term, the mother has a respiratory alkalosis with metabolic compensation (less HCO3− buffer) [2] Large heart of pregnancy
Wide-open IVC, no obstruction by uterus.
Low normal BP
High normal CO
IVC
Normally increased venous capacitance in pregnancy.
Endometrial spiral arteries remodel and dilate, allowing abundant placental perfusion and fetal oxygenation.
Healthy capillary endothelium
= Normal or beneficial hemodynamic effect
= Well oxygenated fetus
= Dilated endometrial spiral arteries
Low normal SVR of pregnancy
= Well perfused myometrium, not contracting
= Normal resistance arterioles (6 cm.
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Box 15.2 Maternal Transthoracic Echocardiography and Right Heart Catheterization Results at 36 Weeks Estimated Gestational Age 1. Ejection fraction 58%, cardiac output = 6.0 L/min, pulmonary artery pressure = 87 mmHg. 2. Abnormal septal motion and position suggesting right ventricular pressure overload. 3. Right ventricle is moderately enlarged with overall depressed systolic function. 4. Right ventricular hypertrophy. 5. Left and right atria are normal in size. 6. Mild/moderate tricuspid regurgitation. Peak velocity of the tricuspid regurgitation envelope is 4.7 m/sec suggesting elevated peak pulmonary artery and right ventricular systolic pressure of 87 + CVP mm Hg. 7. All valves appear normal.
2. General: gravid woman sitting in bed, in no acute distress and breathing comfortably on room air. 3. Pulmonary: clear to auscultation bilaterally, no wheezing. 4. Cardiovascular: regular rate and rhythm, prominent second heart sound, systolic murmur appreciated at the left sternal border. Her laboratory studies are as follows: 1. Electrolytes, blood urea nitrogen (BUN), creatinine, glucose, and calcium are all normal. 2. WBC = 11.6, Hgb = 11.6, Hct = 35, platelets 81K. 3. INR = 0.9, PT = 9.7 sec, PTT = 28.3 seconds, and fibrinogen = 378 mg/dL 4. Thromboelastogram (TEG) is normal. Hand-held transthoracic echocardiography (TTE) exam by the anesthesia team appears grossly unchanged from that obtained during the anesthesia consultation (L-6). Arterial and central lines – as well as a lumbar epidural – are placed uneventfully. A test dose of 3 mL lidocaine 1.5% with epinephrine 1:200,000 is injected with negative results for intravascular or intrathecal injection (L-7). For Stage 1 of labor, fentanyl 100 mcg alone (without additional local anesthetic) (L-8) is injected epidurally at 21:15, 23:32, and 00:18. For stage 2, bupivacaine 0.1% and fentanyl 2 mcg/mL are infused at 6 mL/hour. The patient delivers a vigorous baby girl at 00:47 without complications or significant changes in hemodynamics or oxygenation. Estimated blood loss at delivery is 150 mL, and once the patient is stable after delivery, she is transferred to the surgical intensive care unit (SICU). The postpartum care plan set forth in Box 15.3 is implemented and her course in the SICU is uneventful. She is discharged to home on postpartum day 6.
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Box 15.3 Postpartum Care Plan: 1. Oxytocin is a vasodilator and will increase cardiac output. Use very low doses if at all. Use phenylephrine to prevent or treat hypotension. 2. For postpartum hemorrhage, try not to use carboprost, methylergonovine, or misoprostol. All these agents increase pulmonary vascular resistance. 3. Transfer to Surgical Intensive Care Unit (SICU) after delivery. Patient will need SICU care to continue epoprostenol infusion. 4. Patient can breast feed baby. Make sure SICU has breast pump available.
Normal SVR allows adequate BP with low normal CO
Low normal CO. BP OK. Patient is compensated.
High CVP required to fill stiff RV Mother, compensated
No pain Normothermia Normoxia Normocarbia Epoprostenol Sildenafil Nitric oxide
Optimal pulmonary vasodilator management achieves lowest possible PVR
Well-filled but stiff RV
RA RV RV
LA
LV
High but manageable PVR
Fig. 15.1 Pregnant patients with severe pulmonary hypertension are at high risk of death and their management must be meticulous. Pregnancy is a condition which demands an increased cardiac output, but a high, fixed pulmonary vascular resistance does not allow the cardiac output to increase much, if at all. The best that can be hoped for is the situation shown in this figure: optimal medical management has reduced the pulmonary vascular resistance as much as possible, and the patient is doing well for the time being. Note that maintenance of a normal SVR is a required condition in order for this fragile compensation to persist. If the SVR falls due to exercise or neuraxial anesthesia, the increase in CO needed to maintain BP might necessitate extremely high RV and PA pressures, resulting in interventricular septal shift, catastrophic reduction in CO and BP, and death. Abbreviations: BP blood pressure, CO cardiac output, CVP central venous pressure, LA left atrium, LV left ventricle, PVR pulmonary vascular resistance, RA right atrium, RV right ventricle, SVR systemic vascular resistance
Lessons Learned Lesson 1 Severe pulmonary hypertension is one of the most dangerous medical conditions a pregnant woman can have. This patient’s survival during pregnancy and successful delivery depended on her meticulous medical and obstetric care during pregnancy – long before she went into labor! Figures 15.1, 15.2, 15.3, 15.4, 15.5, 15.6, and 15.7
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Normal SVR
CO and BP fall. LV unable to serve body’s needs. Patient may die.
Very high CVP allows RV to fill Mother, decompensated by PVR
Pain Hypothermia Hypoxia Hypercarbia No medications
Crisis of very high PVR
Well-filled but stiff RV
RA
RV
RV RV Very high PVR
LA
LV Interventricular septal shift prevents LV from filling. CO falls.
Fig. 15.2 When the PVR increases (e.g., due to pain), the systolic pressure in the RV can exceed that in the LV and the interventricular septum will “bow” or bulge toward the LV, as shown in Fig. 15.2. Septal bowing during systole is a sign of pressure overload, whereas septal bowing during diastole is a sign of volume overload or hypertrophy of the RV. Abbreviations: BP blood pressure, CO cardiac output, CVP central venous pressure, LA left atrium, LV left ventricle, PVR pulmonary vascular resistance, RA right atrium, RV right ventricle, SVR systemic vascular resistance
LV RV
LV
Diastole: Hypertrophic RV encroaches on the LV
RV
Systole: Higher pressure in RV pushes interventricular septum into LV, causing echocardiographic “D-sign.”
Fig. 15.3 Such bowing or bulging of the interventricular septum limits the ability of the LV to fill in diastole and thereby limits cardiac output. With LV filling already impaired in diastole due to the RV hypertrophy, the deviation of the septum toward the LV during systole becomes even more extreme, further decreasing cardiac output. This compression and flattening of the interventricular septum under these circumstances is called the “D-sign.” This figure shows an even more extreme case when the interventricular septum bows into the LV, rather than just becoming flatter. Abbreviations: LV left ventricle, RV right ventricle
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Increased blood pooling in capacitance veins from NA
BP falls. CO can’t increase. Patient dies. Mother, decompensated by NA
No pain Normothermia Normoxia Normocarbia Epoprostenol Sildenafil Nitric oxide
Optimal pulmonary vasodilator management: lowest possible PVR
Low CVP is unable to fill stiff RV
RA Under-filled stiff RV
LV
RV RV
LA
SV and CO fall.
High but manageable PVR
Fig. 15.4 Neuraxial anesthesia without compensatory pharmacological vasoconstriction can cause disaster in patients with pulmonary hypertension. The sympathectomy from neuraxial anesthesia with local anesthetics will reduce venous return, right ventricular filling pressure, and systemic vascular resistance. The combination of a reduced CO and a reduced SVR will cause a catastrophic decrease in blood pressure, resulting in death. These effects may be able to be prevented by careful use of phenylephrine to maintain venous return and SVR, and the non-invasive trending of CO and SVR might be useful for this purpose. Abbreviations: BP blood pressure, CO cardiac output, CVP central venous pressure, LA left atrium, LV left ventricle, NA neuraxial anesthesia, PVR pulmonary vascular resistance, RA right atrium, RV right ventricle, SV stroke volume, SVR systemic vascular resistance
Uterus obstructs IVC and reduces VR
Normal SVR
CO falls, BP falls. Patient dies. Mother, decompensated by reduced VR and CO
No pain Normothermia Normoxia Normocarbia Epoprostenol Sildenafil Nitric oxide
Optimal pulmonary vasodilator management: lowest possible PVR
Low CVP is unable to fill stiff RV
RA Under-filled stiff RV
LV
RV RV
LA
SV and CO fall.
High but manageable PVR
Fig. 15.5 Compression of the inferior vena cava by the gravid uterus can also cause disaster in patients with pulmonary hypertension. Maintenance of venous return and an adequately high CVP is of key importance for maintaining the filling and stroke volume of a stiff RV. Abbreviations: BP blood pressure, CO cardiac output, CVP central venous pressure, IVC inferior vena cava, LA left atrium, LV left ventricle, PVR pulmonary vascular resistance, RA right atrium, RV right ventricle, SV stroke volume, SVR systemic vascular resistance, VR venous return
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Increased PVR: Uterus obstructs vena cava:
Hypothermia, hypoxemia, hypercarbia, pain, catecholamines. Wrong or no medications.
Reduced VR and CO
Maternal death in pulmonary hypertension Capacitance vein dilation:
Arteriolar dilation:
Reduced VR and CO
Reduced SVR
Extensive sympathectomy from NA, without use of compensatory vasoconstrictor such as phenylephrine.
Fig. 15.6 This flowchart summarizes three common causes for the deterioration of patients with pulmonary hypertension: (1) increased pulmonary vascular resistance, (2) decreased venous return and CVP due to inferior vena cava compression, and (3) sympathectomy due to neuraxial anesthesia without pharmacological compensation such as phenylephrine to constrict capacitance veins and resistance arterioles. Abbreviations: CO cardiac output, NA neuraxial anesthesia, PVR pulmonary vascular resistance, SVR systemic vascular resistance, VR venous return Manageable PVR:
Warm, comfortable patient breathing plenty of oxygen. Maintain correct medications: (Flolan, sildenafil, etc.)
Patient tilted to left to maintain VR and CO
Maternal survival in pulmonary hypertension Maintain normal venous capacitance, VR and CO
Maintain normal SVR
Provide anesthesia while maintaining venous and arteriolar tone. For labor: neuraxial opioids plus minimal local anesthetic. For cesarean delivery: epidural plus IV vasopressor infusion. TTE guidance. GA plus TEE guidance?
Fig. 15.7 This flowchart summarizes the three ways to help pregnant patients with pulmonary hypertension survive pregnancy and delivery: (1) lower pulmonary vascular resistance as much as possible with medications and keep the patient warm, comfortable, well ventilated, and well oxygenated, (2) prevent inferior caval obstruction by having the patient avoid the supine position, and (3) perform neuraxial anesthesia with great caution and use phenylephrine to help maintain venous tone, venous return, and systemic vascular resistance. Echocardiography may be used to follow the filling of the right and left ventricles. Electrical cardiometry might be useful for trending stroke volume and cardiac output non-invasively. Abbreviations: CO cardiac output, GA general anesthesia, IV intravenous, PVR pulmonary vascular resistance, SVR systemic vascular resistance, TEE transesophageal echocardiography, TTE transthoracic echocardiography, VR venous return
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illustrate the following proposition: At least three hemodynamic processes have to be well maintained in order for the patient to survive pregnancy and delivery: (1) pulmonary vascular resistance has to be kept as low as possible, (2) adequately high right ventricular filling pressure has to be maintained, and (3) systemic vascular resistance must be maintained high enough to allow a satisfactory blood pressure at a low-normal cardiac output.
Lesson 2 The Sixth World Symposium on Pulmonary Hypertension has classified pulmonary hypertension into five etiologic classes, which are shown in Box 15.4 in a simplified form [1]. The following distinctions may help the reader navigate her way through this very complicated field: “primary therapy” refers to treatment of an underlying disease, if known (e.g., mitral stenosis, sarcoidosis); “pulmonary hypertension specific therapy” refers to pharmacological therapy such as an epoprostenol infusion or oral sildenafil directed at the pulmonary hypertension (PH) itself, without regard to the underlying etiology of the PH. This patient had idiopathic pulmonary hypertension, previously called “primary pulmonary hypertension.”
Box 15.4 Pulmonary Hypertension Etiologic Classes, Anticoagulation and Terminology 1. Idiopathic and pulmonary arteriolar disease (e.g., connective tissue diseases, HIV infection, portal hypertension, congenital heart disease, schistosomiasis, and drug use) 2. Pulmonary hypertension due to left heart disease (e.g., mitral stenosis, left ventricular failure) 3. Pulmonary hypertension due to chronic hypoxemia (e.g., living at high altitude, chronic obstructive pulmonary disease) 4. Chronic thromboembolic pulmonary hypertension (CTEPH, which may be amenable to anticoagulation and/or surgical therapy) 5. Multi-factorial or uncertain etiology (e.g., myeloproliferative disorder, sarcoidosis) Note on anticoagulation: It is used in all pregnant patients with pulmonary hypertension (PH), and in non-pregnant patients with idiopathic etiology class 1 and etiology class 4. Its use in non-pregnant patients with other etiologies of PH is individualized. Notes on terminology: Only etiology class 1 is termed “pulmonary arterial hypertension.” Etiology classes 2–5 are termed “pulmonary hypertension.” “Primary therapy” is directed at the underlying disease, whereas “pulmonary hypertension therapy” is directed at the pulmonary hypertension itself (e.g., with pulmonary vasodilator therapy such as epoprostenol or sildenafil).
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Lesson 3 This patient probably could not have withstood the exertion and increased cardiac output required during a painful vaginal delivery. In this setting, an epidural analgesic is not only relieving pain but is probably also helping to save a life.
Lesson 4 Anticoagulation is used primarily in class 4 and idiopathic class 1 pulmonary hypertension patients [1]. In patients with other etiologies, anticoagulation is controversial and employed on an individualized basis.
Lesson 5 Since a pregnant patient can require delivery at any time of the day or night, it is important to have the carefully developed plan of care easily accessible to all caregivers at all times in both the electronic and physical chart.
Lesson 6 Point of care transthoracic echocardiography (TTE) is not meant to replace a formal study, but is performed here as a baseline study, should her clinical condition deteriorate.
Lesson 7 A smaller test dose might have been more prudent in this fragile patient.
Lesson 8 Figure 15.8 explains why neuraxial opioids may be safer than local anesthetics for pain relief in labor in patients with pulmonary hypertension: Neuraxial opioids block pain to some extent but do not cause sympathectomy, whereas local anesthetics do block sympathetic nerves and will decrease the systemic vascular resistance (SVR) and increase venous pooling with a resultant decrease in venous return and cardiac output.
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Dorsal horn Opioids
Pain Pain afferents LA
Dilated resistance arterioles Decreased SVR
Lateral horn sympathetic outflow LA
Spinal cord
Dilated capacitance veins Decreased CO
Spinal nerves
Fig. 15.8 Opioids and local anesthetics both block incoming pain transmission, but local anesthetics block outgoing sympathetic nerves as well, causing hemodynamic problems. Both opioids such as fentanyl and local anesthetics block the entry of pain sensation to the brain, but they operate by different mechanisms and at different locations. Opioids block incoming pain transmission in the substantia gelatinosa of the dorsal horn of the spinal cord and have no major effects on efferent sympathetic nerves. Local anesthetics, on the other hand, block spinal nerves in a relatively undifferentiated manner: in fact, local anesthetics block sympathetic efferent nerves more easily than pain afferents, so when local anesthetics are used for neuraxial block, they reduce the sympathetic vascular resistance and the cardiac output by dilating resistance arterioles and capacitance veins. Abbreviations: CO cardiac output, LA local anesthetics, SVR systemic vascular resistance
If local anesthetics are to be used – as they would need to be with a cesarean delivery under neuraxial anesthesia – a phenylephrine infusion must be available to maintain the SVR, venous tone, and venous return. In this setting, some continuous and non-invasive technology for trending cardiac output and systemic vascular resistance, such as electrical cardiometry, might be helpful, although it was not used in this case.
Reference 1. Up To Date. Etiology classification summarized from the Sixth World Symposium on Pulmonary Hypertension and published by European Respiratory Journal 24 January 2019. Anticoagulation guidelines summarized from the following page of Up To Date: https://www.uptodate. com/contents/treatment-of-pulmonary-hypertension-in-adults?search=anticoagulation%20 pulmonary%20hypertension&source=search_result&selectedTitle=1~150&usage_ type=default&display_rank=1. Accessed 7 April 2019.
Part V
Successful Neuraxial Anesthesia
Chapter 16
Fooling Ourselves: Intravenous Fentanyl Creates the Illusion of a Successful Epidural Thomas L. Archer
Case Presentation In his first few days on the OB Anesthesia rotation, the anesthesia resident is urgently called to do an epidural for a healthy patient with severe labor pain, and the anesthesia attending accompanies him to the patient’s room, where she is screaming in pain. It is her first baby; she is at four centimeters of cervical dilation and says she has to push. The nurses are afraid she will push and that the baby’s head will tear her cervix, and they have been encouraging her to get an epidural for several hours, but she has refused until now. Now the patient’s husband is very upset and impatient for his wife to get pain relief. The mood in the room is almost desperate. The anesthesia attending’s usual practice is to administer 50–100 mcg of fentanyl to the patient before actually placing the epidural, in order to diminish the patient’s pain and anxiety and help her hold still for the procedure without straining during uterine contractions (L-1). While the anesthesia resident is preparing to perform the epidural, the anesthesia attending administers a total of 200 mcg of fentanyl to the patient, and she finally says she is more comfortable (L-2). The anesthesia resident finishes his epidural placement quickly, but the attending is not confident that he has seen a true loss of resistance – despite the resident’s assurance to him that he has felt it. The resident passes the epidural catheter with some difficulty, doses it appropriately with local anesthetic and 100 mcg of fentanyl, and tapes the catheter in place. Soon the patient has a smile on her face and is very grateful for the pain relief provided (L-3). As is his custom, the anesthesia attending checks the patient’s anterior thighs with ice wrapped in a rubber glove, and finds that the patient still has cold sensation there. The resident sees this result as well, but the anesthesia resident and attending
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soon leave the room, feeling that one should not argue with success and that the normal numbness in the legs will develop soon. The anesthesia resident and attending return to their didactic session, but 20 min later, the resident’s pager goes off. “Uh-oh,” he says, giving it a glance. “The last patient is hurting again. The nurses say the epidural doesn’t seem to be working anymore.” The resident and attending return to the patient’s room and find her to be highly uncomfortable again. “Welcome back,” she says. “I felt marvelous for a while but then it started to hurt again. What’s going on?” The anesthesia attending checks the patient’s anterior thighs for cold sensation again and finds that the sensation and strength in her legs are completely intact. The resident replaces the epidural and this time both the resident and attending are convinced that there has been a loss of resistance with the Tuohy needle. Also, the epidural catheter passes very easily this time! The second epidural works perfectly and this time the patient says, “Oh, now I see what you meant about the numbness in my legs. I didn’t feel it before.” (L-4). The anesthesia resident explains to the patient that the first “epidural” had appeared to work because of all the fentanyl she had received, but that now the epidural is really in the right place and that it should work much better from now on. The rest of the patient’s long labor is pain free and she delivers a healthy baby girl vaginally many hours later (L-5).
Lessons Learned Lesson 1 IV fentanyl prior to epidural placement has several potential dangers: (1) maternal over-medication, with respiratory depression and all of the other side effects of narcotics; (2) fetal over-medication, with sedation of the fetus’ cerebral cortex, causing loss of fetal heart rate variability which may be confused with the effects of hypoxia, and (3) neonatal sedation causing problems with bonding and breast feeding. With respect to these concerns, the anesthesiologist should tell the obstetrical team that he may give fentanyl to the patient prior to epidural placement, so that they are aware of its possible effect on fetal heart rate variability. Furthermore, judicious IV fentanyl administration should not be a problem for bonding and breast feeding since it wears off quickly and most babies will latch onto the breast with appropriate encouragement and time.
Lesson 2 Despite the dangers, IV fentanyl prior to epidural placement is very useful both for patient comfort and for facilitating block placement. Since delivery was
16 Fooling Ourselves: Intravenous Fentanyl Creates the Illusion of a Successful Epidural 193
probably still several hours away in this primiparous patient at 5 cm of cervical dilation, the attending had few qualms in treating the patient’s severe pain aggressively until the epidural could take hold. Another alternative would have been to give less fentanyl and do a combined spinal-epidural anesthetic, but this would not have addressed the problem of helping the patient hold still for the procedure in the first place.
Lesson 3 Another potential danger of IV fentanyl prior to epidural placement is exactly what happened in this case: the anesthesia team thought that the “epidural” was working when all of the patient’s analgesia resulted from the systemic effects of the fentanyl she received, since the tip of the epidural catheter was not in the epidural space.
Lesson 4 Because of the danger mentioned in Lesson 3, the anesthesia team needs to check cold sensation in the patient’s lower extremities after the epidural has been placed, as well as just asking the patient if she feels better. Epidural blocks vary in how rapidly they start to work – particularly with varying dosing regimens – but the patient usually is starting to lose cold sensation in her thighs by the time the dressing has been applied. If the patient does not quickly and symmetrically lose cold sensation in her anterior thighs after epidural placement, the anesthesia provider should be suspicious that the epidural will not work properly.
Lesson 5 The most important lesson from this vignette is to be modest, flexible, realistic, and honest with yourself about your epidural placements. Do not try to talk a patient into feeling comfortable! Yes, it is true that sometimes “pressure” can be “misinterpreted” as pain, but pay close attention to the patient’s subjective experience, especially if she is suffering. Have a low threshold for replacing the epidural catheter if it is not working properly. The advantages and disadvantages of administering IV fentanyl to the patient prior to epidural block placement are summarized in Box 16.1.
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Box 16.1 Advantages and Disadvantages of Administering IV Fentanyl Prior to Neuraxial Block Advantages: 1 . Patient gets more comfortable immediately and her anxiety decreases. 2. Patient cooperates better with holding still for block placement. 3. Patient strains less with painful contractions, decreasing the chance of puncturing the dura (“wet tap”) or an epidural vein with the epidural needle. Disadvantages: 1 . Maternal opioid side effects, especially respiratory depression. 2. Fetal opioid side effects: loss of fetal heart rate beat-to-beat variability can be mistaken for fetal hypoxia. For this reason, tell obstetricians when you administer fentanyl prior to performing an epidural. 3. Neonatal opioid side effects: possible neonatal sedation, bonding, and impaired breast feeding. 4. Anesthesiologist complacency with quality of “epidural.”
Chapter 17
What Not to Do During Uterine Contractions: Three Vignettes with One Simple Lesson Thomas L. Archer
Case Presentation Case #1 The anesthesiologist pops her epidural needle tip through the ligamentum flavum into the epidural space at the height of a uterine contraction, while the patient is straining. Immediately after the loss of resistance, the plunger of the glass syringe is pushed back against the anesthesiologist’s thumb as the syringe fills with spinal fluid under pressure (L-1). Case #2 The anesthesiologist pops his epidural needle tip through the ligamentum flavum into the epidural space at the height of a uterine contraction, while the patient is straining. Immediately after the loss of resistance, the glass syringe fills with blood from an engorged epidural vein (L-1). Case #3 The anesthesiologist pops his epidural needle tip through the ligamentum flavum into the epidural space at the height of a uterine contraction, while the patient is straining. Fortunately, his needle does not puncture either the dura or an engorged epidural vein. At the height of the next contraction, he passes the epidural catheter into the epidural space and feels an immediate pop as the semi-transparent catheter fills with blood (L-1).
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Lessons Learned Lesson 1 When the patient is in pain and straining or holding her breath, the epidural veins are engorged and the dura becomes tense due to the increased pressure within the epidural space. Do not attempt to break through the ligamentum flavum with your epidural needle – or to pass a catheter into the space – when the patient is having a contraction or otherwise straining, since the chance of puncturing the dura or an epidural vein is increased at that time. Wait until the contraction is over to enter the space or pass the catheter. In fact, it seems to help to avoid puncturing an epidural vein with the epidural catheter if you have the patient take a deep breath as you pass the catheter – that maneuver decreases intra- and extra-pleural pressure and probably shrinks the epidural veins briefly, making a puncture less probable. It is acceptable to advance the epidural needle within the interspinous ligament during contractions (as long as the patient is holding still), but once you start to feel the increased grittiness of the ligamentum flavum, you should stop advancing the needle and wait for the contraction to end and for the patient to relax before you pop into the epidural space. Administering intravenous fentanyl to the patient prior to performing an epidural helps the patient relax her chest and abdomen between uterine contractions. Figures 17.1, 17.2, 17.3, and 17.4 give a schematic review of what happens in the epidural space when a patient strains and increases her intrathoracic and/or intraab-
Head
SVC
CSF
Epidural veins
Spinous processes
Azygos vein
Normal intrathoracic pressure
IVC Normal intraabdominal pressure
Lumbar collateral veins
Fig. 17.1 In a comfortable pregnant patient who is not straining, pushing, or holding her breath – and who is positioned on her left side or is sitting upright – the inferior vena cava is wide open and the collateral system of lumbar, epidural, and azygos veins is decompressed, minimizing pressure within the epidural space. Abbreviations: CSF cerebrospinal fluid, IVC inferior vena cava, SVC superior vena cava
17 What Not to Do During Uterine Contractions: Three Vignettes with One Simple…
Vertebral bodies
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Interspinous ligament
CSF
Spi
Supraspinous ligament
nou
sp
roc
ess
Epidural vein Ligamentum flavum Epid
ural
Posterior longitudinal ligament
nee
dle
Nice placement! Skin and fat
Dura
Fig. 17.2 The time to advance the epidural needle into the epidural space is between contractions, when the patient is not in pain and not straining, in order to minimize the chance of puncturing an epidural vein or the dura. Abbreviation: CSF cerebrospinal fluid
CSF Head
Engorged epidural veins
Azygos vein
Increased intrathoracic pressure
Increased intraabdominal pressure
Lumbar collateral veins
Fig. 17.3 Straining and breath-holding increase intrathoracic and intraabdominal pressure, which forces blood from the vena cava into the lumbar, epidural, and azygos collateral venous system, engorging the epidural veins with blood. Abbreviation: CSF cerebrospinal fluid
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Vertebral bodies
CSF
Interspinous ligament
Spi
nou
Supraspinous ligament
sp
roc
ess
Engorged epidural veins Epi
dur
al n
eed
le
Blood return
Ligamentum flavum
Posterior longitudinal ligament
Dura
Skin and fat
Fig. 17.4 If a needle or epidural catheter tip enters the epidural space when the epidural veins are engorged, one’s chance of hitting an epidural vein increases. Abbreviation: CSF cerebrospinal fluid
dominal pressure. (The vertebral bodies are omitted from Figs. 17.1 and 17.3.) The key lesson is to not advance anything into the hazard-laden epidural space during a uterine contraction! A further footnote to this lesson is to not administer the epinephrine-containing test dose right before a uterine contraction, since the HR normally increases by 20–30 beats per minute during a normal painful contraction, and the anesthesiologist may be fooled into thinking that the test dose is positive for intravascular injection when the increased heart rate is actually caused by pain and autotransfusion.
Chapter 18
A One-Sided Epidural Thomas L. Archer
Case Presentation A 32-year-old woman, G2P1 and at term, has broken her bag of water and is in early labor at 3 am. Her cervix has dilated to 3 cm, and she is having severe labor pain and is requesting an epidural. The resident has been busy all night and decides not to use ultrasound for this epidural placement, since he can easily feel her spinous processes. He deftly places the epidural, but the block is one sided. The patient says, “Wow, this is strange, the same thing happened to me last time. They had to do it over again, because the first time it worked on just one side” (L-1). The resident examines the patient with ice in a rubber glove and confirms that the patient is unable to feel the cold on her right leg and abdomen, but that the left side of her body has normal cold sensation. The resident explains that one-side blocks do occur from time to time and that it sometimes helps to pull the catheter back a little bit in order to get it back into the middle, since the tip may have traveled away from the midline. The resident undoes the sterile dressing, pulls the catheter back 1 cm, and replaces the dressing. He then injects a new test dose and follows it with another dose of local anesthetic. After waiting a few more minutes to make sure there are no adverse effects, he leaves the room but promises to be right back to make sure that the block is working properly (L-2). The resident returns after 15 min and finds that the patient is still having pain on her left side. She says, “Well, the pain on the left side is a little better, but it’s still there and it still hurts a lot. But now I can’t move my right leg at all.” The resident apologizes for not having fixed the problem and promises to come back shortly with someone to help. The attending always uses ultrasound for epidural placement, maintaining that she gets better results and fewer one-sided blocks when she uses it. She feels that this may be a good opportunity to convince the resident to use ultrasound for all T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_18
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epidural placements, by demonstrating its utility for finding the spinous processes and checking for rotation of the vertebral bodies (L-3). “Well,” says the attending, “Since you said it was an easy placement and since it isn’t working adequately now, let’s just pull it out, start over and put it back in – but this time with the benefit of ultrasound!” The patient’s cervix is now 4 cm dilated and her pain is increasing. In two divided doses, the resident gives her 100 mcg of fentanyl IV, removes the old epidural catheter, and applies the US probe to the patient’s lumbar spine. “Well, gosh,” he murmurs with surprise as he works with the probe, “I was way off midline.” By using ultrasound – and using it properly without pulling the skin to one side or the other as he places the probe at various locations on the skin – the resident can see that he had punctured the skin with the epidural needle about a centimeter to the right of an imaginary vertical line passing through the tips of the two adjacent spinous processes. There is no rotation of the vertebral body at that level, so the explanation for the one-sided block is simply that he had misjudged the midline (L-4). The resident carefully marks the skin indicating the correct vertical and horizontal axes that define the best insertion point and further notes that the depth to the ligamentum flavum/dura complex (L-5) is 4.8 cm. He carefully re-preps the back and skillfully replaces the epidural catheter – but this time with the insertion point more than a centimeter to the left of his first puncture site. The resident easily gets loss of resistance at a depth of 5.1 cm and passes the catheter 4 cm into the epidural space. He gives yet another test dose and when it is negative he gives another local anesthetic dose. He then does a Cohen maneuver for good measure, and by the time he has finished applying the new sterile dressing, the patient says – with a relaxed smile on her face –, “OK, this time it’s working. I can feel the left side getting numb and the pain is gone.” The attending and the resident are both delighted with their successes (L-6).
Lessons Learned Lesson 1 As part of your history-taking, ask the patient about previous experiences with anesthesia – particularly labor analgesia, where patient experiences can vary so widely. If the resident had heard the patient’s story of a one-sided block before, he might have been especially meticulous about defining the true midline and looking for vertebral rotation (which was not present in this case).
Lesson 2 Pulling the catheter back when the epidural block is one sided is often very effective – particularly if the catheter originally entered the epidural space in the midline and if it was inserted more than 4 cm into the space. The key to avoiding a one-sided block is entering the epidural space in the midline in the first place, as shown in Figs. 18.1 and 18.2.
18 A One-Sided Epidural
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Patient’s left side
Anterior
= Pain or no pain
= Epidural catheter
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= Cerebrospinal fluid
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Fig. 18.1 Two initially one-sided epidural placements illustrate the importance of entering the epidural space in the midline. Epidural A entered the epidural space in the midline, but the tip of the catheter traveled far over to the right side of the epidural space as it was advanced. This epidural will be a failure, with the patient having pain on her left side and being too numb on her right. Epidural B, on the other hand, entered the epidural space left of the midline and the tip – again, advanced blindly – has deviated even farther to the left. The patient with epidural B will hurt on her right side and be too numb on her left side. At this point, epidurals A and B perform equally poorly, by being one-sided blocks. To see why epidural A can almost certainly be “fixed” (unlike epidural B), please see Fig. 18.2
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= Epidural catheter
= Dura
= Ligamentum flavum
= Epidural space
= Cerebrospinal fluid
= Nerve roots (motor or sensory)
Fig. 18.2 The epidural that entered the epidural space in the midline can probably be fixed by pulling it back. Epidural A can only get better when it is pulled back – the tip must get closer to the midline, thereby allowing local anesthetic to spread more evenly to the two sides. Epidural B, on the other hand, probably cannot be fixed by pulling it back – no matter how far you pull it back, the tip will always tend to be located to the left side of the epidural space. Hence, any technique that helps us place the epidural in the middle of the epidural space should (on average) improve the quality and symmetry of our blocks
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Some practitioners will pass the catheter more deeply into the epidural spaces of obese patients, realizing that the mobility of the subcutaneous fat will tend to pull the catheter out of the epidural space over time as the patient moves around in bed. Other practitioners recommend always passing the catheter 4 cm into the epidural space, but using the Cohen maneuver in obese patients to prevent it from getting pulled out by the abundant mobile adipose tissue. In any event, pulling the catheter back 1 cm is often effective for rescuing a one- sided block, but the obstetric anesthesiologist should resist the temptation to “fiddle” excessively with a block that is not working well. Often, prompt replacement using ultrasound guidance is the best way to fix a poor epidural – including a one- sided epidural.
Lesson 3 Some authors are proponents of using pre-procedural ultrasound on every patient, claiming that it improves the success rate and quality of their blocks [1]. Others say it isn’t necessary – at least in patients with normal body habitus who probably have normal anatomy [2]. The role of pre-procedural ultrasound in facilitating neuraxial block placement is being investigated and debated, and using ultrasound has certainly not become the standard of care.
Lesson 4 When performing epidurals, we usually assume that the vertebral bodies are not rotated – and they usually are not rotated appreciably, as shown in Fig. 18.3a. But another pitfall of just palpating the spinous process to determine the right needle trajectory is that one can palpate a spinous process without realizing that the corresponding vertebral body is, in fact, rotated, as shown in Fig. 18.3b. Rotation of vertebral bodies in scoliosis is the norm and this fact explains the clinical practice of aiming the needle slightly into the scoliotic curve when placing epidurals in scoliotic patients (without the benefit of ultrasound). If one feels the spinous process and then advances the needle straight forward in a patient with scoliosis, as shown in Fig. 18.3b, one’s needle will go toward the right side of the epidural space-- or miss the space entirely. Figure 18.4b shows how the epidural needle has to be angled in order to hit the underlying epidural space when the vertebra is rotated-- which was not the case in this patient. Unfortunately, despite all the benefits of ultrasound – and even if there is no rotation of the vertebral bodies as in scoliosis – it is still easy to misjudge the midline
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Normal spine with no vertebral rotation in transverse plane
Two spines viewed from patient’s back
Scoliotic spine with vertebral rotation in transverse plane
Level of two L3-4 interspaces shown below
L3-4 viewed from above
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Fig. 18.3 Getting the “midline” wrong when the vertebral body is rotated. When we feel a spinous process, we usually assume that we will hit the ligamentum flavum if we advance the needle straight ahead in the sagittal plane, as shown in (a). But what if the underlying vertebral body is rotated in a scoliotic patient, as shown in (b)? If that is the case (as can be seen with pre-procedural ultrasound), one has to angle the needle to the left in order to enter the epidural space at its midpoint and avoid a one-sided block. (Please note that the vertebral bodies are viewed from above, i.e., from the patient’s head looking downward). So “midline” is a slippery concept: Do we mean the spinous processes, or do we mean the epidural space? The bottom line is that the spinous processes can be unreliable guides to the midline of the epidural space – even if we can palpate the spinous processes. Using ultrasound in obese patients, we can not only identify the spinous processes with confidence, but also determine whether the vertebral body is rotated or not. Abbreviation: L lumbar
while using ultrasound, as shown in Fig. 18.5. Silhouette A shows the true position of a subcutaneous spinous process in red and a blue skin marking that overlies it when the mobile skin has not been displaced to one side from its normal position. A common mistake, shown in silhouette B, is to inadvertently pull the skin over to the left (or the right) with the ultrasound probe as one identifies the midline and then to make the mark on that point on the skin which happens to overlie the midline at that moment. When the operator has made his mark, he removes the ultrasound probe from the skin and the mobile skin snaps back into its original position – which is no longer over the midline, as shown in silhouette C! The way to avoid this error is to simply place the ultrasound probe on the skin every time one takes a look at underlying structures, without ever pulling the skin one way or another with the probe.
18 A One-Sided Epidural
Normal spine with no vertebral rotation in transverse plane
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Two spines viewed from patient’s back
Needle aiming into scoliotic curve
Level of two L3-4 interspaces shown below
L3-4 viewed from above
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Fig. 18.4 When a vertebra is rotated (which cannot be ascertained by palpating the spinous process), the epidural space is not directly anterior to the spinous process in the sagittal plane and the needle has to be directed to the left (in this example) in order to enter the epidural space in its midline and avoid a one-sided block (or missing the epidural space altogether). Vertebral rotation can be discerned with pre-procedural ultrasound and the angle of needle insertion adjusted accordingly. Abbreviation: L lumbar
Lesson 5 “Ligamentum flavum/dura complex“is the term used to describe the fact that the ligamentum flavum and dura often appear as one single line on ultrasound since those two structures are separated only by the thin epidural space.
Lesson 6 There are many subtleties to consistently placing effective epidurals, whether one uses ultrasound or not. But ultrasound does not lie, although it can be used improperly, like any other tool. When used with care, ultrasound is remarkably effective in facilitating epidural block placement, especially in obese patients and those with spine abnormalities or previous surgery. Ultrasound enthusiasts argue that the technology converts the blind and somewhat “magical” process of epidural placement
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= Obese patient seen from back
= Our goal: A skin marking (blue) overlying spinous process ( red) when skin is not stretched.
= Line overlying spinous processes in patient without scoliosis (true midline)
MS
= Setting ourselves up for failure : We stretch mobile skin (MS) to the left with the ultrasound probe when we make our mark on the skin.
= Failure achieved! Mobile skin (with blue dot on it) moves back to the right when skin is no longer stretched to the left by the ultrasound probe.
Fig. 18.5 Getting the midline wrong again – even with ultrasound! Unfortunately, we can improperly mark the midline even if we use ultrasound. Ultrasound is a tool that does not lie – but it can be used improperly. Panel (a) of this figure shows what we would like to achieve with ultrasound: a skin marking (blue dot) that overlies a spinous process (red dot). However, if we stretch the patient’s mobile skin to the left or the right with the ultrasound probe as we make our skin marking, as in Panel (b), the skin will move back to its original position once we take the probe off the skin – and the skin marking will no longer lie directly over the spinous process, as shown in Panel (c)! The key lesson here is that the ultrasound probe must simply be placed on the skin and lifted vertically off the skin – rather than being dragged across the skin – when marking the midline. This may seem like a trivial point, but it can easily make the difference between success and failure in identifying the midline. Abbreviation: MS movement of mobile skin to the left using the ultrasound probe
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using palpable landmarks alone into a more rationalized and fully visualized process that involves less “magic” and more knowledge.
References 1. Talati C, Arzola C, Carvalho JC. The use of ultrasonography in obstetric anesthesia. Anesthesiol Clin. 2017;35(1):35–58. 2. Arzola C, Mikhael R, Margarido C, Carvalho JC. Spinal ultrasound versus palpation for epidural catheter insertion in labour: a randomised controlled trial. Eur J Anaesthesiol. 2015;32(7):499–505.
Chapter 19
Dosing an Epidural for “Back Labor.” Thomas L. Archer
Case Presentation A 32-year-old healthy woman, G2P1001, is in labor at 6 cm of cervical dilation. She received an epidural at 4 cm and got complete relief of her labor pain, which at that time was anterior and right above the pubic symphysis (L-1). The nurse calls the anesthesiologist and reports that the patient is now complaining of severe pain in her lower back with each contraction. When the anesthesiologist arrives in the patient’s room, the patient says, “Boy, I’m sure glad you’re here! This is the same back labor I had last time! Can you fix it like they did the last time with some stronger stuff?” The anesthesiologist confirms that the patient’s and fetus’ vital signs are stable (L-2) and that the epidural infusion is still running (L-3). Next, he checks the patient’s block level with ice in a rubber glove and finds that it has been stable at about T7. The patient is already partly sitting up, but the anesthesiologist raises the back of her bed a little further and then slowly doses the epidural with 5 mL of lidocaine 2% with bicarbonate and epinephrine, plus fentanyl 100 mcg (L-4). The anesthesiologist stays in the room for a few minutes to make sure there are no adverse effects from the injection (L-5), and within 5 min the patient’s back labor is melting away. Her vital signs are stable since the block level has only gone up to T6 (L-6). Note: This patient’s story continues in Chap. 27.
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_19
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Lessons Learned Lesson 1 Ask where the labor pain is located! Changes in the location and character of the pain can herald important changes in the patient’s condition – such as descent of the fetal head into the pelvis (as in this case) or more dangerous events such as placental abruption or uterine rupture. An epidural can mask the pain of uterine rupture in cases of trial of labor after cesarean section (TOLAC) and uterine rupture should always be kept in mind as a possible cause of a dramatic change in the quality, intensity, or location of labor pain – even in patients who have no prior uterine scar.
Lesson 2 Maternal or fetal vital sign changes would eventually be seen with either placental abruption or uterine rupture, but with simple back labor both the maternal and fetal vital signs should be stable.
Lesson 3 Whenever there is a question about the functioning of an epidural (and even when it is working well), it is a good idea to check the level of the block with ice from time to time. Occasionally, an epidural has “stopped working” because the epidural pump has been turned off. Needless to say, the block can also go too high.
Lesson 4 Relieving the pain of “back labor” often requires the strongest local anesthetic and opioid combination in your armamentarium, for two reasons: (1) back labor is very painful and hard to block (perhaps because it is caused by the direct pressure of the hard fetal occiput on the lumbosacral plexus, as shown in Figs. 19.1 and 19.2), and (2) you want to know quickly if your maximum epidural pain therapy will work, since the next step would be a new CSE – and this will take time during which the patient will be very uncomfortable.
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No nerve pressure at pelvic brim Soft face Hard occiput Sacrum Lumbosacral nerves
Mother’s back
Mother’s front
Fig. 19.1 Occiput anterior (OA) presentation and labor pain without “back labor.” With an OA presentation (the most common presentation), it is the baby’s soft face that drags across the sacrum and its nerves, and this type of presentation tends not to cause “back labor”
Nerve pressure at pelvic brim Hard occiput
Soft face
Sacrum Lumbosacral nerves
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Mother’s front
Fig. 19.2 Occiput posterior (OP) presentation with “back labor.” Babies whose journey down the birth canal has been accompanied by severe lower back and sacral pain often emerge “OP” or “occiput posterior” at birth – suggesting that it is the baby’s hard occiput “dragging” over the sacrum and its nerves that causes the intense form of labor pain called “back labor.”
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Lesson 5 Every epidural injection must be approached with caution. Catheters can “migrate” and a catheter that has performed well can suddenly produce a serious complication. Accidental intrathecal injection of an “epidural” dose will cause a high block or total spinal with loss of consciousness, hypotension or cardiovascular collapse, and respiratory arrest. Intravascular injection can cause maternal tachycardia (if epinephrine is part of the mixture) or maternal mental changes and seizure. Each new injection can also “merely” cause hypotension due to an extension of the existing epidural block. With epidural analgesia, the dictum “every dose is a test dose” is very important! Also, observe whether there is any pain during the injection itself. Epidural injections should be painless. The patient will feel the cold local anesthetic solution running through the tubing taped to her back, but she should feel no pain. Pain during an epidural injection is definitely abnormal and may indicate intradural placement of the catheter and is an indication for replacement of the catheter.
Lesson 6 Relieving a patient’s back labor in this way is very satisfying and is an example of differential block: the patient’s anterior labor pain (coming from the dilating cervix and entering the spinal cord at T10-L1) is well blocked by the dilute epidural infusion solution, but direct pressure on the sacrum and lumbosacral nerves usually requires higher local anesthetic concentrations. Another memorable example of different types of pain being blocked by different agents is that the pain due to peritoneal traction at cesarean delivery (CD) was not blocked very well by neuraxial local anesthetics alone, before neuraxial opioids came into widespread use in the 1980s. With the advent of intrathecal opioids in the 1980s, the quality of spinal block for peritoneal pain during CD has greatly improved.
Chapter 20
Management of a Patient with an Unsatisfactory Labor Epidural, Now Going for Cesarean Delivery Thomas L. Archer
Case Presentation An obese 32-year-old woman in good health, G1P0, needs a cesarean delivery for failure to progress in labor. Her cervix has not dilated beyond 6 cm, despite ample time and strength of uterine contractions as demonstrated by the use of an intrauterine pressure catheter (IUPC). The patient is exhausted and anxious and has had a fair amount of breakthrough pain above her pubic symphysis and in her back, despite three MD-administered epidural boluses of local anesthetic and fentanyl. The patient’s block level to cold sensation is at T8 (L-1). Labor & Delivery has been busy and the anesthesia resident has not had time to replace the patient’s epidural catheter – which had been somewhat hard to insert in the first place. The patient’s airway appears to be consistent with routine intubation if required. It is three o’clock in the morning and the obstetric team feels some urgency to start her CD since her fetus has shown a few late decelerations with some loss of fetal heart rate variability. The anesthesia team takes the patient back to the operating room and uses the obstetric ultrasound machine to define the point, angle, and depth required to reach the ligamentum flavum and dura. A single-shot, full-dose spinal with bupivacaine 12 mg, preservative-free morphine 100 mcg and fentanyl 25 mcg is administered at L3-4 and an excellent spinal block develops such that the patient’s fingers are tingly, but fortunately she has no trouble breathing (L-2). The anesthesia team reassures the patient that the block should go no higher and that it will soon recede a little, making it easier for her to breath (L-3). The obstetric team uneventfully delivers a vigorous baby and the patient makes a swift recovery, with good post-operative pain control.
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Box 20.1 When Has the Epidural Failed? Primary criteria for failed epidural: 1. Patient dissatisfaction with pain relief. This assumes that the practitioner has evaluated the block clinically (e.g., with cold sensation from ice in a rubber glove) and used an adequate local anesthetic mixture. 2. Greater than two MD-administered epidural boluses, in an attempt to “save” the epidural and provide adequate pain relief. Supplemental signs that epidural may fail to give adequate pain relief for cesarean delivery: 1. Significant asymmetry in level of block to cold sensation between patient’s two sides. 2. Localized areas of breakthrough pain (“hot spots”). 3. Patchy or discontinuous areas of loss of cold sensation in legs. Patchy but extensive block may indicate subdural placement of catheter, in which case it should be removed.
Lessons Learned Lesson 1 The patient has a low level to cold sensation with breakthrough pain despite adequate dosing and three MD-administered boluses. This is clearly a failed epidural. The anesthesiologist needs to be honest with himself and set firm criteria for replacing a failed epidural. Box 20.1 presents common criteria for making such a decision.
Lesson 2 Unsatisfactory (failed) epidurals that go to CD can be managed with several neuraxial block variations, all of which are reasonable under most circumstances and all of which also have potential disadvantages and dangers (see Box 20.2). One could argue in this situation, however, that a combined spinal/epidural (CSE) using a reduced intrathecal dose of local anesthetic is always preferable to a single-shot spinal. Why burn your bridges with a full dose single-shot spinal when you can give a reduced dose of local anesthetic intrathecally and then pass an epidural catheter to supplement the block in the unlikely event that the intrathecal dose is inadequate? My answer to this question is twofold: (1) Performing the CSE takes a little more time than a spinal, and (2) what if your block level with the reduced dose of local anesthetic is too low and your epidural catheter doesn’t thread or just doesn’t work
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Box 20.2 The Failed Epidural: What to Do? For continued labor analgesia: • Have a low threshold for replacing epidural, perhaps at another interspace. • Consider a new combined spinal-epidural (CSE), including intrathecal fentanyl. For subsequent cesarean delivery: • • • •
De novo spinal anesthetic with full or reduced dose. De novo CSE with full or reduced dose. De novo epidural with titrated dosing. Consider reducing intrathecal dose of local anesthetic by 20–40% if substantial epidural block exists or if epidural has been dosed within the last 30 min. • Predicted ease of intubation will influence your choices, due to risks of block failure or high spinal. • General or local anesthesia as last resorts.
Table 20.1 Neuraxial block alternatives for the patient with a failed labor epidural who requires cesarean delivery Neuraxial technique Single-shot spinal Full IT dose Single-shot spinal Reduced IT dose Combined spinal-epidural Full IT dose Combined spinal-epidural Reduced IT dose Epidural Titrated epidural dosing
Advantages Quick; little chance of block being too low
Disadvantages Fixed duration; block may go too high, requiring intubation
Quick; little chance of block being too high
Fixed duration; block may go too low, requiring general anesthesia
Quick onset of block; catheter allows block titration upward and increased duration Quick onset of block; catheter allows block titration upward and increased duration
More time required than for single-shot spinal; catheter may not work More time required than for single-shot spinal; catheter may not work
Minimal chance of too high a block. Allows careful titration to avoid airway management
Slow onset; may not work, as first epidural did not work
Abbreviations and explanations: IT intrathecal, Reduced dose = 60–80% of full dose
once you have inserted it? Then you may have a supine patient who has to be put under general anesthesia. Of course, the opposite risk exists with a full-dose spinal – the block may go too high, necessitating intubation! Table 20.1 presents the advantages and disadvantages of five different neuraxial techniques which can be used in patients with failed labor epidurals who need a cesarean delivery.
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One’s approach should be individualized based on multiple factors such as (1) the time pressure for delivery, (2) the degree of existing block from the inadequate epidural, (3) the time since the last epidural injection, (4) the condition of the patient’s airway, and (5) the patient’s temperament and emotional state. The tendency of some practitioners, however, is to use a full intrathecal dose when taking a patient with a failed epidural to CD, unless there is a significant block already in place or unless the time since the last epidural injection has been less than 30 min. This is, however, a controversial area, and it is always important to plan for what to do if the block is too low, on the one hand, or too high, on the other hand. For example, if the patient’s airway appeared difficult for routine intubation, it might be preferable to choose either a CSE beginning with a reduced dose IT injection, or even to perform a “straight” epidural at another interspace, if time allowed. Unfortunately, the scenario of a patient with an unsatisfactory labor epidural who now needs a CD is relatively common and there is no easy or single answer. The best way to avoid this problem before CD is to have a low threshold for replacing an unsatisfactory labor epidural.
Lesson 3 Once the baby has been delivered, mothers with high blocks usually find it easier to breath, since the abdominal contents exert much less pressure on the diaphragm. Sometimes the patient feels better if one gently assists her ventilation until the baby is delivered or the block recedes a bit. Needless to say, a high spinal presents an increased risk of aspiration, and the anesthesiologist needs to have her suction at the ready and to keep the patient under close and continuous observation.
Chapter 21
Rescuing a Low Spinal Thomas L. Archer
Case Presentation A 33-year-old woman, G2P1 at 39 weeks gestation, is having an elective repeat cesarean delivery. The resident places a single-shot spinal anesthetic at the L4-5 interspace (L-1) and very slowly and carefully (L-2) injects 1.6 mL of heavy 0.75% bupivacaine, combined with 100 mcg of preservative-free morphine and 25 mcg of fentanyl. The patient has had back pain during her pregnancy and has requested that everyone move her very slowly and carefully while she is on the OR table. After the spinal injection, the team slowly and carefully helps her adopt the supine position with a tilt to the left, as is routine. Within minutes, the patient feels intense numbness developing in her buttocks, but after 5 min her block has only reached T10, as judged by loss of cold sensation. After another 5 min, the level has only risen to T9. The resident calls the anesthesia attending and says (out of the patient’s hearing) “It looks like we may have to repeat the block.” The attending replies, “Well, maybe we can fix this one. Let’s see what we can do.” After an explanation to the patient, the attending drapes a sheet between her legs to cover the perineum and with the help of the resident they lift both legs together, gently flexing both the hip and the knee joints. The attending then has the nurse tip the OR table into about ten degrees of Trendelenburg position. The anesthesia attending and the resident then gently push the flexed thighs onto the patient’s pregnant abdomen and hold that position while asking her to cough a few times. The fetal heart rate is being monitored continuously and does not change during the maneuver (L-3).
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After 90 s in that position, the attending has the nurse flatten the OR table and the attending and resident stretch the legs out again to the original supine and left-tilted position. The attending has the resident wait another 2 min – at which time the resident finds that the level of anesthesia has increased to T4. Surgery and delivery of a vigorous baby girl proceed smoothly.
Lessons Learned Lesson 1 Reynolds [1] states that no spinal needle should be knowingly inserted above the L3-4 interspace, and certainly hitting the spinal cord is always a danger with spinal anesthesia. But inserting the spinal very low can cause problems too, as explained in the next lesson.
Lesson 2 If one is injecting a hyperbaric anesthetic solution at a low interspace in the sitting position, one could argue that some degree of rapidity of injection, turbulence, and mixing of the injected solution would help the anesthesia to travel cephalad by helping the anesthetic solution get over the lordotic “hump.” Also, laying the patient flat immediately after injecting the spinal helps avoid an anesthetic level that is too low.
Lesson 3 This maneuver deliberately increases intraabdominal pressure and may obstruct the inferior vena cava – neither of which is good for the mother or the fetus over an extended period of time. So, this maneuver should be performed gently, briefly and with plenty of Trendelenburg position to decrease the need for vena caval compression. Needless to say, one should watch the patient very closely during this maneuver, while checking the effects of the spinal assiduously and continually. This maneuver could (theoretically) cause a spinal that is too high. Figures 21.1, 21.2, 21.3, 21.4, 21.5, and 21.6 illustrate and explain the anatomy and physiology of all these maneuvers and how they help spread the hyperbaric anesthetic solution in a cephalad direction. There are anecdotal reports that this maneuver may still work up to 30–60 min after the intrathecal injection!
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Pregnant abdomen IVC
Thighs
LC
AV
Head
Hips Anterior epidural veins Lumbar lordosis of posterior elements CSF of spinal column
Fig. 21.1 Schematic portrayal of left-tilted supine pregnant woman. Lumbar lordosis and intraabdominal pressure are normal for pregnancy in the figure, and both are increased from the nonpregnant state. The inferior vena cava is wide open and the lumbar and epidural collateral veins are not distended. The uterine venous pressure is low and the uterus is not congested. Note: the anterior elements of the spine (vertebral bodies) and posterior epidural veins are not shown. Abbreviations: AV azygos vein, CSF cerebrospinal fluid, IVC inferior vena cava, LC lumbar venous collaterals
Pregnant abdomen
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Bolus of hyperbaric local anesthetic solution “trapped” by gravity below the lumbar lordosis.
Fig. 21.2 A hyperbaric dose of local anesthetic solution injected low in the thecal sac with the patient in the sitting position can pool below the peak of the lumbar lordosis, prevented by gravity from traveling farther up the neuraxis. Note: the anterior elements of the spine (vertebral bodies) and posterior epidural veins are not shown
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Thighs
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Flexion of thighs flattens out lumbar lordosis, decreasing barrier to cephalad spread of hyperbaric local anesthetic solution.
Fig. 21.3 Flexing the thighs 90° – even without putting pressure on the abdomen – flattens out the lumbar lordosis and helps the hyperbaric local anesthetic solution travel cephalad. Note: the anterior elements of the spine (vertebral bodies) and posterior epidural veins are not shown
igh s
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Obstructed IVC
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Distended anterior epidural veins
Compressed CSF column Local anesthetic pushed cephalad
Fig. 21.4 Flexing the thighs further onto the abdomen increases intra-abdominal pressure and closes off the inferior vena cava, thereby squeezing blood into the lumbar-epidural-azygos system and compressing the thecal sac – all of which drives the anesthetic solution farther cephalad. Note: the anterior elements of the spine (vertebral bodies) and posterior epidural veins are not shown. Abbreviations: CSF cerebrospinal fluid, IVC inferior vena cava
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Fig. 21.5 Trendelenburg position allows the hyperbaric anesthetic mixture to “fall” even further cephalad. Of course the solution has mixed with spinal fluid by now and is less hyperbaric than it was. Note: the anterior elements of the spine (vertebral bodies) and posterior epidural veins are not shown
Pre g abd nant om en
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Coughing causes turbulence and further mixing of anesthetic solution with CSF
Fig. 21.6 Finally, having the patient cough creates turbulence in the cerebrospinal fluid and facilitates the mixing and cephalad distribution of anesthetic with the CSF. But vigilance is required, since all of these maneuvers – which are often performed together – might convert a spinal that is too low into one that is too high! Note: the anterior elements of the spine (vertebral bodies) and posterior epidural veins are not shown. Abbreviation: CSF cerebrospinal fluid
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Finally, the different mechanisms illustrated in Figs. 21.1, 21.2, 21.3, 21.4, 21.5, and 21.6 are presented separately for conceptual purposes, but in practice they are usually performed all together [2].
References 1. Reynolds F. Neurologic complications of pregnancy and neuraxial anesthesia, p. 744. In: Chapter 32 of Chestnut’s obstetric anesthesia, principles and practice. 5th ed. Philadelphia: Elsevier Saunders; 2014. 2. Kim JT, Shim JK, Kim SH, Jung CW, Bahk JH. Trendelenburg position with hip flexion as a rescue strategy to increase spinal anaesthetic level after spinal block. Br J Anaesth. 2007;98(3):396–400.
Chapter 22
A Failed Epidural Followed by a Failed Spinal (Part 1) Thomas L. Archer
Case Presentation A 27-year-old obese diabetic woman, G1P0, receives a labor epidural which works perfectly for 2 h but then stops working after she changes position repeatedly and vigorously for Foley catheter placement (L-1). The resident had accessed the epidural space easily and passed the catheter 3 cm into the space (L2), but did not perform the Cohen maneuver (L-3) before he applied the sterile dressing. The patient’s contractions are becoming more frequent and painful and the resident is preparing to replace the epidural when the fetus begins to have late decelerations (L-4). The obstetricians temporize by administering terbutaline – which slows uterine contractions substantially – and the fetal heart rate normalizes (L-5), so the patient is taken back to the OR for a cesarean delivery under non-emergent conditions (L-6). In the OR, the resident tries to perform a single-shot spinal at the same interspace as the epidural, advancing the needle carefully and checking frequently for cerebrospinal fluid by removing the stylet. Soon he gets the slow return of clear fluid into the hub of the spinal needle (L-7). He hadn’t felt any pop– which is often felt when the tip of the needle punctures the dura– and he was unable to freely aspirate fluid through the spinal needle, but he injects the spinal dose nevertheless. Over the next 5 min, the “spinal” has no effect whatsoever on the patient’s pain or lower extremity sensation (L-8). The attending arrives and discusses the options with the patient – either to repeat the spinal or to put her to sleep. The resident has given her some fentanyl by now and she is feeling better. The attending offers the hope that they will get the spinal to work if they try a second time, but says she can’t promise success. Encouraged by the attending, the patient opts for trying the spinal again (L-9).
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This time the resident uses pre-procedural ultrasound and sees the ligamentum flavum at a depth of 4.6 cm – deeper than where he thought he had injected the first spinal dose. This time, again, the resident gets clear fluid back more superficially but – with the attending urging him on – he continues to insert the needle further. He then feels a pop, removes the stylet, and is able to aspirate clear fluid into his syringe (L-10). This time he injects the intrathecal dose and an excellent spinal develops. The resident says to the patient, “The first time I probably got into a pocket of local anesthetic and thought that it was spinal fluid. This time, I got it in the right place and we’ll be OK now” (L-11). The patient’s spinal anesthesia works well this time; the mother relaxes and her baby boy is born with Apgar scores of 7 and 8.
Lessons Learned Lesson 1 When an epidural that had been working well simply stops working, the most common cause is that the epidural catheter tip has been pulled out of the epidural space. (The second most common cause is that someone turned off the epidural infusion pump or that the tubing has become disconnected.) Figures 22.1, 22.2, 22.3, 22.4, and 22.5 show how movement of subcutaneous fat can pull the tip of the epidural catheter out of the epidural space, if the Cohen maneuver is not used in obese patients. Interspinous ligament Vertebral bodies
CSF
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Epidural space
s Mobile skin and SC fat
Epidural vein Ligamentum flavum
Epid
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Posterior longitudinal ligament
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Nice placement !
Fig. 22.1 Successful epidural placement, showing the relationships (not to scale) between the skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space with veins, dura, cerebrospinal fluid, posterior longitudinal ligament, and vertebral bodies. Abbreviations: CSF cerebrospinal fluid, SC subcutaneous
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Epidural space Initial epidural doses work well
Epid
ural
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Fig. 22.2 The catheter has been passed through the epidural needle into the epidural space in this obese patient who has a thick layer of mobile subcutaneous fat. The Cohen maneuver is not performed despite the patient’s obesity and a sterile dressing is promptly applied over the epidural insertion site, thereby affixing the epidural catheter to the mobile skin. Initial epidural doses of local anesthetic work – as long as the catheter tip remains within the epidural space! Abbreviations: CSF cerebrospinal fluid, SC subcutaneous
Vertebral bodies
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Epidural space Tip of “epidural” catheter gets pulled out of epidural space by mobile skin and fat.
Posterior longitudinal ligament
Mobile skin and SC fat displaced upward by patient movement
Catheter affixed to skin
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Fig. 22.3 Subsequently, the obese patient moves vigorously in bed, causing extensive motion of the subcutaneous fat on her back. Since the epidural catheter is affixed to the skin – and since there is no “slack” in the catheter (which would have been provided by the Cohen maneuver) – the motion of the subcutaneous fat pulls the catheter out of the epidural space, with the tip now resting in the interspinous ligament. Abbreviations: CSF cerebrospinal fluid, SC subcutaneous
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Epidural space
Interspinous ligament
Mobile skin and SC fat restored to original position
“Epi dur cath al” eter
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Catheter tubing buckles under skin
Fig. 22.4 When the patient stops moving and settles back into her original position, the subcutaneous fat returns to its original position, but the damage has been done: the tip of the epidural catheter is no longer resting in the epidural space, but rather is located in the interspinous ligament. Abbreviations: CSF cerebrospinal fluid, SC subcutaneous
Vertebral bodies
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Epidural space Pocket of LA in interspinous ligament
Mobile skin and SC fat restored to original position
Fai
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Fig. 22.5 A subsequent injection or infusion of local anesthetic is now deposited within the interspinous ligament rather than the epidural space and the “epidural” stops working. Abbreviations: CSF cerebrospinal fluid, LA local anesthetic, SC subcutaneous
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Lesson 2 Most obstetric anesthesiologists place the catheter 3–4 cm within the epidural space. A more shallow placement runs the risk of having the catheter pulled out of the epidural space by skin motion (as happened in this case), whereas inserting the catheter more deeply increases the risk of a one-sided block.
Lesson 3 The Cohen maneuver is a technique for ensuring that the mobility of the skin and subcutaneous fat in obese patients does not pull the tip of the epidural catheter out of the epidural space. The maneuver is explained graphically in Figs. 22.6, 22.7, and 22.8.
Lesson 4 In this diabetic patient, there are two factors militating against adequate placental perfusion: (1) frequent uterine contractions and (2) probable placental vascular disease. If the epidural were working, it could constitute a third factor by causing
Vertebral bodies
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Fig. 22.6 For the Cohen maneuver, the epidural catheter is placed in the usual fashion, but the sterile dressing is not immediately applied to the catheter at the skin puncture site. This is done in order to allow the skin and fat to slide over the catheter during the subsequent step shown in Fig. 22.7. Abbreviations: CSF cerebrospinal fluid, SC subcutaneous
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Epidural space Tip of epidural catheter does not get pulled out of epidural space
Posterior longitudinal ligament
Mobile skin and SC fat displaced upward by operator’s hand Mobile fat slides out over catheter
Dura
Fig. 22.7 The operator now deliberately stretches the mobile skin and subcutaneous fat as far as possible, slipping it out along the catheter as far as possible. Although it is the skin and fat that are moving out, it appears that the epidural catheter is being “sucked” under the skin! The sterile dressing is then applied (as in Fig. 22.8), thereby affixing the epidural catheter to the skin when it has been fully stretched out – but not before! Abbreviations: CSF cerebrospinal fluid, SC subcutaneous
Vertebral bodies
Sterile dressing is finally applied, and then…
CSF
Epidural space Epidural works fine despite subsequent patient motion, due to slack in the catheter
Posterior longitudinal ligament
Dura
…mobile skin and SC fat return to original position
Catheter tubing buckles under skin
Fig. 22.8 After the sterile dressing has been applied and the catheter has been affixed to the skin, the operator lets go of the fat layer and allows the tissue to return to its normal location. The excess length of epidural catheter buckles within the subcutaneous fat, thereby providing the “slack” required to prevent the catheter from being dislodged by any subsequent patient movement. Abbreviations: CSF cerebrospinal fluid, SC subcutaneous
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hypotension, and the supine posture with inferior vena caval compression by the gravid uterus is a fourth threat to placental perfusion that must always be guarded against.
Lesson 5 The use of terbutaline here is an example of “intrauterine resuscitation”– performing a maneuver which improves and stabilizes the fetal condition, in order to buy time until more definitive therapy (cesarean delivery, in this case) can be brought to bear.
Lesson 6 Even if a cesarean delivery is inevitable, intrauterine resuscitation can convert an anxiety-provoking emergency into a much less stressful situation. In this case, once the uterine contractions become less frequent, the fetus’ oxygenation improves and there is even adequate time to repeat a failed spinal anesthetic!
Lesson 7 Whenever a spinal anesthetic is performed after local anesthetic has been injected or infused into the spine, one must always ask the question: “What is this fluid coming back through the spinal needle? Is it cerebrospinal fluid (CSF) or is it residual local anesthetic?” Fig. 22.9 shows how you can be fooled into thinking that a pocket of local anesthetic within the interspinous ligament is CSF.
Lesson 8 It is easy to confuse two distinct failed spinal syndromes: the first is a low spinal, which has very profound effects which are limited to the legs and perineum, and, second, a failed spinal which has no numbing effect at all on the legs or perineum. The first failed spinal syndrome suggests that the local anesthetic is “trapped” caudad to the lumbosacral lordosis (see Chap. 21) but the second syndrome suggests that no local anesthetic reached the CSF at all.
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Epidural space Pocket of LA in interspinous ligament
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nal
Posterior longitudinal ligament
nee
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Fig. 22.9 Since the Cohen maneuver was not performed, patient movement has pulled the “epidural” catheter out of the epidural space and local anesthetic has accumulated in the interspinous ligament. When the anesthesiologist attempts to do a spinal “on top of” the failed “epidural,” she encounters fluid return. The fluid comes from the pocket of LA in the interspinous space, but the resident thinks that she has accessed the CSF with the tip of her spinal needle, and she injects her “intrathecal” dose. That “spinal” fails, of course, since the injection is not intrathecal. This may be the mechanism of some cases when a failed spinal has been blamed on “bad bupivacaine.” Abbreviations: CSF cerebrospinal fluid, LA local anesthetic
Lesson 9 This patient may have had several hours of severe labor pain since her epidural stopped working and may not be willing to undergo a second attempt at a spinal. On the other hand, if the anesthesiologist suspects that the first spinal was simply not placed correctly, repeating the spinal is a reasonable option. Communication with the patient and the obstetrician is of key importance and the judicious administration of intravenous fentanyl to the patient at this point will often help her accept a second attempt.
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CSF
Epidural space
Dural “POP”
Pocket of LA in interspinous ligament Spin
al n
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eed
le
Dura True CSF !
Figs. 22.10 The “solution” to this problem is to be aware of this possibility of being fooled by a pocket of local anesthetic in the interspinous ligament and to push the spinal needle deeper, until one feels the “pop” of the spinal needle puncturing the dura. Once the injection is made into the CSF, the spinal will work normally. Abbreviations: CSF cerebrospinal fluid, LA local anesthetic
Lesson 10 Figure 22.10 shows how the resident achieves success by advancing the needle farther than before, feeling the pop as the spinal needle punctures the dura and finally injecting the medication into the CSF. One does not always feel the dural pop, but one usually does.
Chapter 23
A Failed Epidural Followed by a Failed Spinal (Part 2) Thomas L. Archer
Case Presentation A 32-year-old diabetic woman, G2P1, receives a labor epidural at L3-4 which causes an intense block in her groins, legs, and perineum, but does not ascend above that level. The patient had given a history of spinal surgery at T9-L1 and had a scar on her back consistent with that level (L-1). The resident and the attending had used pre-procedural ultrasound on this patient and had determined that both the L2-3 and L3-4 interspaces had normal sonographic anatomy (L-2). The attending suggests that they repeat the block at L2-3, but as a combined spinal-epidural anesthetic (CSE), so that some local anesthetic (LA) and fentanyl is injected directly into the CSF, thereby bypassing a possible obstruction to local anesthetic spread within the epidural space. The resident is preparing to perform this procedure under the attending’s supervision, when the fetus begins to have late decelerations as contractions become more frequent. The obstetricians decide that the fetus is not tolerating labor (L-3), administer terbutaline to suppress uterine contractions, and prepare to perform a cesarean delivery. After the terbutaline and the cessation of uterine contractions, the fetal heart rate returns to normal, so there is ample time for neuraxial anesthesia. The resident’s first attempt at a spinal fails to extend the block (L-4), but his second attempt with a full dose of LA is successful after he feels the pop which usually accompanies true dural puncture (L-5). The block level rapidly ascends to T4 but it continues cephalad and within minutes the patient says she is short of breath (L-6). The resident gives ephedrine 15 mg (L-7) and calmly tells the patient that he is going to help her breathe with a mask until the spinal level
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_23
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diminishes – but that he may have to put her to sleep and put in a breathing tube (L-8). With the resident gently assisting her breathing, the patient seems to relax. She says her hands feel numb but when the resident checks them, they still have some grip strength. The patient remains alert and the spinal level goes no higher. The anesthesia resident has the suction ready in case the patient regurgitates, but he decides not to intubate, since he believes that the spinal level will soon recede (L-9). Surgery begins and a vigorous baby boy is delivered. By the time of delivery, the patient is breathing more easily but her hands are still numb and she is unable to hold the baby. The rest of surgery proceeds smoothly and the resident explains what happened – that the spinal went too high because some of the local anesthetic in the epidural space got into the spinal fluid. The patient accepts the resident’s explanation and is able to hold her baby in the Recovery Room as the spinal wears off. Her post-operative pain relief is excellent. The next day the resident and the attending visit the patient to explain again what had happened and to apologize for the patient’s bad experience with the high spinal (L-10).
Lessons Learned Lesson 1 Any patient that has had spine surgery should be a “red flag” – not as a contraindication to neuraxial anesthesia, necessarily – but as a stimulus to the exercise of our humility and caution. Previous spine surgery can interfere with the successful functioning of an epidural, and the patient needs to understand from the beginning that the epidural may not work perfectly and may require adjustments along the way. Perhaps a high spinal should be mentioned as one of the possible complications of any neuraxial block, particularly when previous spinal surgery may have changed the characteristics of the epidural space.
Lesson 2 Pre-procedural ultrasound can help us identify normal appearing interspaces, including any degree of twisting of the spine (as in scoliosis). The use of pre- procedural ultrasound in no way guarantees a successful epidural (since a blockage to epidural spread of local anesthetic may still exist above the level that appears normal on ultrasound), but it at least gives us the assurance that the space appears to be normal. In the context of a patient who has had spinal surgery, it is also beneficial to know the exact depth to the ligamentum flavum/dura complex, but despite all
23 A Failed Epidural Followed by a Failed Spinal (Part 2)
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Fig. 23.1 Successful epidural placement, showing the relationships (not to scale) of skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space with veins, dura, cerebrospinal fluid, posterior longitudinal ligament, and vertebral bodies. But in contrast to the patient described in Chap. 22, this patient’s epidural space has been blocked by scar tissue from previous spine surgery. Abbreviations: CSF cerebrospinal fluid, LA local anesthetic, SC subcutaneous
the information that can be derived from pre-procedural ultrasound, previous surgery may have caused adhesion of the dura to the ligamentum flavum, and the risk of a “wet tap” (puncturing the dura as well as the ligamentum flavum) may be increased in patients who have had spine surgery. In this patient – as shown in Fig. 23.1 – the resident successfully accessed the epidural space in the routine manner, but did not realize that there was a blockage to the spread of epidural local anesthetic cephalad from his point of epidural catheter placement, shown in Fig. 23.2. Furthermore, it should be noted, there is no way of predicting the existence of such a blockage, but the risks of both a “wet tap” and a poorly functioning epidural are probably increased in patients who have had spine surgery. Whether pre-procedural ultrasound can in some way reduce this risk has not been investigated.
Lesson 3 As in the case described in Chap. 22, the patient’s diabetic placental vascular disease may be responsible for the fetus’ not being able to withstand the added stress of uterine contractions in labor.
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Obstruction to epidural spread of LA Sterile dressing
Pocket of LA in epidural space
Epidural LA does not move cephalad. Block fails.
Epi dur plac al cath eter ed p rop erly
Posterior longitudinal ligament
Dura CSF
Fig. 23.2 Local anesthetic is injected through the catheter into the epidural space, but spread is inadequate in a cephalad direction due to a blockage within the space, and the local anesthetic forms a localized pocket within the epidural space. Abbreviations: CSF cerebrospinal fluid, LA local anesthetic
Lesson 4 Similarly to what happened in the case described in Chap. 22, the first spinal is a failure. As shown in Fig. 23.3, the resident’s spinal needle accesses a pocket of local anesthetic in the epidural space outside the dura and he injects his “intrathecal” dose into that pocket of fluid, thinking that it is cerebrospinal fluid.
Lesson 5 Figures 23.4 and 23.5 show how the spinal block is finally executed with success. When attempting to perform a spinal “on top of” a failed epidural, it is important to feel the dural pop to know that one has accessed the cerebrospinal fluid, rather than a pocket of local anesthetic – in this case, a pocket within the epidural space.
Lesson 6 Figure 23.6 shows how the hole in the dura made by the spinal needle can allow local anesthetic already in the epidural space to pass into the CSF, thereby adding to the effect of the full intrathecal dose administered. Because of this risk, many
23 A Failed Epidural Followed by a Failed Spinal (Part 2)
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Obstruction to epidural spread of LA
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Fig. 23.3 When this patient with a failed epidural goes to cesarean delivery, the spinal needle enters the pocket of local anesthetic in the epidural space. The local anesthetic drips from the spinal needle, fooling the operator into thinking that he has accessed the cerebrospinal fluid, but the injection of the intended “intrathecal” dose does not extend the block in a cephalad direction. Abbreviations: CSF cerebrospinal fluid, LA local anesthetic
Vertebral bodies
Obstruction to epidural spread of LA
Dural “POP” CSF
Spin
al n thro eedle po ugh dura ps
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Fig. 23.4 As in Chap. 22, when the spinal needle is pushed farther inward, the tip finally pops through the dura. Abbreviations: CSF cerebrospinal fluid, LA local anesthetic
p ractitioners would perform a combined spinal epidural (CSE) in this situation and/ or use a reduced initial dose of intrathecal local anesthetic, since they know that the situation shown in Fig. 23.6 may occur. It has been shown that a “dural puncture epidural” can in fact augment an epidural block [1, 2].
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Fig. 23.5 The second and truly intrathecal full dose injection has its full effect by bypassing the epidural obstruction. Abbreviation: CSF cerebrospinal fluid
Vertebral bodies
But spinal may work too well !
EITLA
CSF
Posterior longitudinal ligament
Dura
Fig. 23.6 The level of the spinal anesthesia can go too high, since residual local anesthetic in the epidural space can now pour into the CSF through the hole in the dura, adding to the effect of the previously injected full dose. For this reason, many practitioners would perform a combined spinal epidural with a reduced initial dose in this situation. If the initial level were too low, they could augment the block with epidural medication, knowing that the hole in the dura would allow some leakage of the epidural medication into the CSF, despite the blockage in the epidural space itself. Needless to say, in this situation the block height is difficult to predict and vigilance is required – as always! Abbreviations: CSF cerebrospinal fluid, EITLA excessive intrathecal local anesthetic
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The key difference between this case and the one described in Chap. 22 is that in this case the pocket of local anesthetic is in the epidural space – rather than in the interspinous ligament – and therefore has a greater probability of passing through the hole made in the dura and causing a high, or total, spinal.
Lesson 7 The resident knows that the complete sympathectomy of a high spinal is often accompanied by bradycardia and cardiovascular collapse [3], so he is preventing that from happening by administering vasopressors prophylactically.
Lesson 8 The decision whether to intubate or not has to be individualized, based on many factors: the patient’s NPO status, whether the patient is in labor or not, the extent of the block, the probable ease of intubation, the mental state of the patient, etc.
Lesson 9 Often a high block will stabilize at a level that is “high” but not “too high” – and even that degree of high block will not last long. Admittedly, it does not take long for a patient to regurgitate and aspirate.
Lesson 10 As presented in Box 9.1, it is important to see the patient after any adverse outcome and to listen thoughtfully and empathetically to her account of the experience. It may have helped, as well, if one had mentioned while consenting the patient for anesthesia that a high spinal is one of the infrequent complications of a neuraxial anesthetic.
References 1. Chau A, Bibbo C, Huang CC, Elterman KG, Cappiello EC, Robinson JN, Tsen LC. Dural puncture epidural technique improves labor analgesia quality with fewer side effects compared with epidural and combined spinal epidural techniques: a randomized clinical trial. Anesth Analg. 2017;124(2):560.
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2. Pan PH, Bogard TD, Owen MD. Incidence and characteristics of failures in obstetric neuraxial analgesia and anesthesia: a retrospective analysis of 19,259 deliveries. Int J Obstet Anesth. 2004;13:227–33. 3. D’Angelo R, Smiley RM, Riley ET, Segal S. Serious complications related to obstetric anesthesia: the serious complication repository project of the Society for Obstetric Anesthesia and Perinatology. Anesthesiology. 2014;120(6):1505–12.
Chapter 24
Labor Epidural for a Patient with Scoliosis Thomas L. Archer
Case Presentation A 27-year-old woman, G2P1 and at term, is having her second baby. Her cervix has dilated to 3 cm when she presents to L&D with regular painful contractions. When she meets the anesthesiologist, she tells her that she is in excellent health— except for her back. She says she has scoliosis and wants to know if it will prevent her from having an epidural this time—and if there is any increased danger of the epidural causing more back problems later on if she does decide to have one. She had an epidural with her first baby but reports that it took the anesthesiologist a long time to get it in, and even then that it seemed to work mostly on the right side (L-1). The anesthesiologist replies that there are pain relief options other than epidurals, but that a new technology is now available that allows us to visualize the spine with sound waves and that this technology has helped her a great deal, personally, when she performs potentially difficult epidurals (L-2). In fact, she tells the patient, she uses ultrasound imaging now for all her epidurals. She goes on to say that she uses the same ultrasound machine as the obstetricians use to view the baby. Of course, she adds, she can’t guarantee success, but she offers to at least take a look at the patient’s back with ultrasound and give the patient her opinion regarding the feasibility of an epidural in her case (L-3). The patient agrees that taking a look can’t hurt and the anesthesiologist then gives the patient some IV fentanyl to temporarily lessen her labor pains. The patient relaxes with the IV analgesic and the anesthesiologist begins by palpating the spinous processes of her back from the upper thoracic region to the sacrum. She notes that her spine does seem to follow a very shallow S-shaped curve, and she knows
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that part of the scoliosis process involves a twisting of the vertebral bodies themselves in the transverse plane, as well as the formation of the S-curve in the coronal plane by the palpable spinous processes. She then uses the probe to find the sacrum and quickly marks out the levels of the first few lumbar interspaces. She then notes that there are tiny puncture scars from the patient’s previous epidural at L3-4, and at that level she sees an image similar to that seen in Fig. 24.8 Panel A, in which the usual landmarks are distorted, probably demonstrating a rotation of the vertebral body when seen from above as shown in Fig. 24.9 Panel A. One interspace higher, however, at L2-3—as shown in Figs. 24.8 Panel B and 24.9 Panel B—she notes that the interspace is wide open and that there is no twisting of the vertebral body. Furthermore, the reflection from the ligamentum flavum/dura complex at that level is very bright (Fig. 24.8 Panel B), suggesting that the interlaminar space is wide open at that level. She notes that the depth of the ligamentum flavum/dura complex at the L2-3 interspace is 4.1 cm. She gives a favorable report to the patient, saying that the anatomy looks normal a little higher up from where they went the last time, and that she thinks that an epidural placement there should go smoothly—although, of course, she cannot guarantee success. The patient feels reassured that the anesthesiologist seems to have converted what used to be a “blind” procedure into something guided by imaging technology and she asks the anesthesiologist to proceed with an epidural at the level which looks favorable. The epidural placement goes smoothly at L2-3 and the Tuohy needle enters the epidural space on the first pass. The anesthesiologist threads the catheter and tapes up the epidural after dosing it sequentially as follows: test dose 3 mL of 1.5% lidocaine with epi 1:200,000, followed by fentanyl 100 mcg, followed by 3 mL of 2% lidocaine. By the time the dressing is on, the patient says, “Wow, I think I can feel my legs getting warm already!” And then she adds, “Gosh, that sure was different from last time! Let’s just hope it works—these contractions are getting stronger again.” The epidural works perfectly for labor and delivery, and since it only took one pass to place the catheter, the patient does not even report any skin tenderness the next day at the insertion site. The anesthesiologist feels very pleased that she upgraded her epidural skills by taking a course on the use of ultrasound to facilitate neuraxial block placement [1] (L-4).
Lessons Learned Lesson 1 Figure 24.1 shows schematic drawings of two spines: a normal spine A on the left and a scoliotic spine B on the right. Scoliosis not only involves an S-curve of the palpable spinous processes when seen from the patient’s back, but also involves rotation in the transverse plane of some of the vertebral bodies located within the curves.
24 Labor Epidural for a Patient with Scoliosis Normal spine without scoliosis or vertebral rotation (viewed from patient’s back)
L3-4 viewed from above
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L3-4 level of vertebral body in each spine
B
A
Palpable spinous processes Skin surface = Transverse section of lumbar vertebra = Needle direction in transverse plane (approach to the “target”)
= Our “target” for neuraxial anesthesia — center of spinal canal
Fig. 24.1 A normal spine is shown in Panel (a) on the left and above: The spinous processes form a palpable straight line going down the back and the spinal canal is directly anterior to the spinous process in the sagittal plane In scoliosis, shown in Panel (b) on the right and above, the palpable spinous processes form a gentle S-curve down the back. In addition, vertebrae located within the curves may be rotated in the transverse plane, as shown in Panel (b) on the right and below. Hence, in this example, the spinal canal is located to the left of the palpable spinous process, such that one would have to angulate the needle to the left (“into the curve of the scoliosis”) in order to access the epidural space. Panel (b) below also shows why the patient might have gotten a right-sided epidural with her first baby: if the previous anesthesiologist inserted the epidural needle “straight ahead” in the sagittal plane, he may have accessed the right side of the epidural space (if he hit it at all!). Abbreviation: L lumbar
Lesson 2 Figure 24.2 shows the basic idea of using ultrasound to visualize the spine beneath a layer of subcutaneous fat. It is obvious—but sometimes optimistically ignored— that the thicker the subcutaneous fat layer, the more exact the needle path must be in order to hit the ligamentum flavum “target.” Figure 24.3 shows how ultrasound only sees surfaces—it cannot look into bone. Therefore, the images that it forms should be conceived of as lines which represent
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Sound waves
Subcutaneous fat
SP AP TP
Our tiny and often distant target
VB
Fig. 24.2 Neuraxial ultrasound made simple. This schematic diagram shows the general idea of using ultrasound to visualize a spine that is hidden beneath a layer of subcutaneous fat. Sound waves reflect back from the structures they hit, forming an image which is seen in white on the darkened screen. The schematic sound wave arrows point to five of the vertebral elements that can be seen with ultrasound: one spinous process, two articular processes (also called facet joints), and two transverse processes Intuitively, one can see that the thicker the layer of subcutaneous fat, the harder it will be to get the needle into our correct, small, and distant target space. Abbreviations: AP articular process (also called facet joint), SP spinous process, TP transverse process, VB vertebral body Spinous process
US probe
Articular process Transverse process
LF/D complex
PLL of VB VB
VB
Fig. 24.3 This figure shows how the ultrasound image is built up from the reflections of sound from the surfaces of underlying structures. The left side of the figure shows the underlying vertebral structures: spinous process, articular processes (also called facet joints), transverse processes, ligamentum flavum/dura complex, and posterior longitudinal ligament of the vertebral body The right side of the figure shows how the sound wave reflections seen on the ultrasound screen only show the surfaces of the various structures, as white lines. Abbreviations: LF/D complex ligamentum flavum/dura complex, PLL posterior longitudinal ligament of vertebral body, US ultrasound, VB vertebral body
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only the surfaces of the structures we are looking at. In other words, if the “real” vertebra looks like the image on the left side of Fig. 24.3, the ultrasound image will consist only of the white lines drawn on the bony surfaces, as shown on the right side of the same figure. Figure 24.4 shows an actual spinal ultrasound image on the left and an overlay on the right showing the same structures identified in Fig. 24.3. Figures 24.5 and 24.6 show two classic spinal ultrasound views: Fig. 24.5 shows the view obtained when the probe is positioned directly over the spinous process, in which all we “see” is the spinous process itself, whereas Fig. 24.6 shows the view
SP AP TP
PLL
LF/D
VB
Fig. 24.4 To the left in the figure, we see a real spinal ultrasound image without any identifying markers. On the right, we see the same image with white markers overlying the structures identified with green labels as follows: spinous process (SP), articular process (AP, also called facet joints), transverse process (TP), ligamentum flavum/dura complex (LF/D), and posterior longitudinal ligament (PLL) of the vertebral body. The vertebral body itself (VB) is also marked for orientation but is not seen with ultrasound. (Note: The image on the left side comes from the PIE website [1] and has been modified on the right by the author with permission)
a
b
With probe positioned over the spinous process…
…all you “see” is spinous process!
Fig. 24.5 What you see on the ultrasound view depends on the level at which you position the probe. When the probe is located over the spinous process, as shown in Panel (a), you only see spinous process on ultrasound, as shown in Panel (b) to the right. (Note: images are from the PIE website [1] and are used with permission)
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b Articular process
Ligamentum flavum
Transverse process Posterior longitudinal ligament (vertebral body)
With probe positioned between spinous processes…
…you can “see” into spinal canal!
Fig. 24.6 When we move the probe lower—as shown in Panel (a) to the left—we are able to “see” between the spinous processes, and—if our angle is correct—we can “see” all the way to the ligamentum flavum, dura, spinal canal, and posterior longitudinal ligament, as shown in Panel (b) on the right. (Note: images are from the PIE website [1] and are modified and used with permission)
obtained when the probe is positioned so as to “look” between the spinous processes at the correct angle, in which case we can “see” all the way through to the ligamentum flavum, spinal canal, and the posterior surface of the corresponding vertebral body.
Lesson 3 Figure 24.7 shows the process of finding and marking the exact insertion point, insertion angle, and depth to the ligamentum flavum prior to sterile preparation of the skin. Panel A shows identification of the line between two spinous processes (the “midline”). Panel B shows the establishment of the cephalad-caudad level at which the ultrasound probe can “see” between the spinous processes all the way to the ligamentum flavum/dura complex (so called since the two structures often cannot be distinguished by ultrasound since they are only a few millimeters apart). Panel C shows how the intersection of these two lines identifies the proper insertion point. All that remains now is for the operator to remember and reproduce with his needle the angle of the probe which shows the ligamentum flavum/dura complex at its brightest and clearest, and to measure the depth to those structures on the ultrasound screen! Figure 24.8 shows ultrasound views similar to what the anesthesiologist saw in this case: At L3-4, the usual landmarks are hard to make out and appear lower on the left side of the screen than on the right, whereas at L2-3 everything looks normal. This is why the anesthesiologist was fairly confident she could get a good block at L2-3.
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Fig. 24.7 Using the ultrasound probe on the unprepared skin to define: (Photo a) the “midline” between the spinous processes running along the cephalad-caudad axis, (Photo b) the cephalad- caudad level at which the sound waves “see” the ligamentum flavum/dura complex between the spinous processes, and (Photo c) the proper needle insertion point as defined by the intersection of the vertical and horizontal lines identified in Photos (a) and (b). All that remains now to achieve success is to note the depth to the ligamentum flavum and to remember the proper angle for successfully slipping between the spinous processes to access the ligamentum flavum and the midline of the epidural space. (Note: Images used with permission from [1])
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L3-4: bad interspace for an epidural!
L2-3: good interspace for an epidural!
Landmarks are asymmetrical because of rotated vertebra
Landmarks are symmetrical and LF/D complex and ventral dura show up well.
Fig. 24.8 The ultrasound view at L3-4 looks bad, whereas it looks good at L2-3. The anesthesiologist is fairly confident of being able to perform a good block at L2-3 because the ultrasound anatomy appears normal at that level. Abbreviations: L lumbar, LF ligamentum flavum, LF/D ligamentum flavum/dura complex. (Note: Images used and modified with permission from [1])
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L2-3 L3-4
L2-3 viewed from above
Palpable spinous processes
Skin surface
= Needle direction in transverse plane (approach to the “target”)
Fig. 24.9 This figure makes the same point as Fig. 24.8, but shows it in a different way. In Panel (a) on the left, we see the situation at L3-4: the vertebra is rotated, and advancing the needle straight ahead would not hit the middle of the epidural space—and might miss it altogether. However, on the right side of the figure (in Panel b), we see the situation one interspace higher: at L2-3, the ultrasound landmarks are normal, suggesting that there is no vertebral rotation and that the ligamentum flavum is accessible to our needle if we aim it “straight forward” in the precise sagittal plane. Abbreviation: L lumbar
Figures 24.9 and 24.10 attempt to further cement the reader’s understanding of these concepts: In Fig. 24.9, Panel A, the vertebra at the L3-4 interspace is twisted, and if the operator proceeds to pass the needle in the usual “straight forward” manner (in the exact sagittal plane), she will not enter the midline of the epidural space—and in fact may miss it entirely. The message of Fig. 24.9, Panel B is that the usual needle direction will be successful at the next interspace up (L2-3), because the vertebra is not twisted at that level. Figure 24.10 attacks the twisted vertebra problem in another way. Rather than avoiding block placement at L3-4, we could use our knowledge gained from ultrasound to direct our needle in the proper direction to hit the midline of the epidural
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Single scoliotic spine with vertebral rotation at L3-4, but not at L2-3 (view from patient’s back)
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L2-3 viewed from above
Palpable spinous processes
Skin surface
= Pre-ultrasound teaching for needle direction in scoliosis:
= Needle direction in transverse plane (approach to the “target”)
“Aim into the concavity of the scoliosis in the transverse plane.”
Fig. 24.10 This figure rounds out the story with a final observation: the anesthesiologist might have achieved a successful block at L3-4 if she had angulated her needle as shown on the left side of the figure—but she chose to keep it simple and perform her block at a normal-appearing interspace (L2-3), since it appeared more “straightforward.” Abbreviation: L lumbar
space at L3-4, as shown on the left in Panel A. But in practice, it is almost certainly better to perform our blocks at interspaces which have normal ultrasound anatomy, if possible, such as at L2-3, shown in Panel B to the right.
Lesson 4 The main message of this chapter is that ultrasound helps to identify normal- appearing interspaces and may increase the ease of block placement and our overall success with neuraxial anesthesia. But this is a controversial topic which is still being debated and investigated.
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Box 24.1 Ultrasound: A Promising Technical Advance in Spinal and Epidural Techniques Bedside ultrasound can be extremely useful to facilitate spinal and epidural anesthesia placement by providing the following information: • The exact interspace at which the puncture should be performed, which is especially important in spinals to avoid hitting spinal cord • The best interspace, which has normal anatomy and is “wide open” • The ideal insertion point at the intersection of vertical and horizontal axes • The best angle of the needle pass • The distance from the skin to the epidural space • Anatomical abnormalities, such as scoliosis Ultrasound provides both proven and yet-to-be-proven advantages by: • Providing a superior teaching tool for spinals and epidurals, as it facilitates the learning curve, and may increase safety during the learning curve • Shortening the duration of procedures • Increasing the comfort of procedures, both for patient and operator • Decreasing the number of attempts and the associated trauma • Possibly decreasing the number of accidental dural punctures • Forecasting difficult epidurals (similar to difficult intubations) • Transforming difficult epidurals into easy epidurals • Helping in the selection of the best equipment for the spinal/epidural Note: Box 24.1 is adapted from the PIE website, with permission [1].
Reference 1. The images for Figures 24.4 through 24.8 and text of Box 24.1 are from the website of the University of Toronto’s Perioperative Interactive Education (PIE) division and are used and modified with permission. PIE has an excellent online interactive module for learning spinal ultrasound, which can be accessed at the following address: http://pie.med.utoronto.ca/VSpine/ VSpine_content/VSpine_ultraSoundGuided_lumbar.html.
Part VI
Anesthetic Complications
Chapter 25
Wrong Medication Thomas L. Archer
Case Presentation An anesthesia resident prepares what he thinks is his usual intrathecal dose for the repeat cesarean delivery (CD) of a healthy woman at term. The Pharmacy Department restocks the anesthesia carts carefully each morning and the resident withdraws a vial from the place in the cart where the vials of 0.75% bupivacaine in dextrose are kept. He does not inspect the vial for cracks, does not read the label, and does not read the label a second time aloud. As is his custom, he leaves the opened and empty vial on a piece of 4 × 4 gauze in case the vial needs to be inspected later. To the solution he has drawn up from the uninspected vial, he adds 25 mcg of fentanyl and 100 mcg of preservative-free morphine. The spinal placement is routine, but the anesthesia attending notices that the spinal starts to work more quickly than usual. The quality of the block, however, and its level are perfect and the CD proceeds uneventfully. One of the junior OB residents performs the surgery under the careful supervision of the OB attending, surgery takes at least an hour, and as they are closing the skin, the patient is starting to complain of pain. His curiosity and suspicion aroused; the anesthesia attending inspects the vial from which the fluid for the spinal had been withdrawn—and discovers that it had been a vial of 5% lidocaine in dextrose for intrathecal injection. The patient is immediately informed and has good post op analgesia, since the morphine and fentanyl had been added as usual. The case was thoroughly discussed at the next Departmental quality improvement meeting and is treated as a near-miss by the Hospital risk management system (L-1).
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_25
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Lessons Learned Lesson 1 Box 25.1 presents two different approaches to human error: the personal approach and the systems approach [1]. The resident readily admits he made a very serious mistake, accepts the blame, and feels ashamed of being so careless, but despite the recognized importance of personal responsibility and accountability in individual cases, the systems approach is generally considered today to be the more constructive global and long-term approach to preventing human error. Box 25.1 Two Approaches to Combating Human Error The personal approach: 1 . Focuses on the individual’s performance 2. Speaks in terms of personal accountability and guilt 3. Interprets error as a sign of personal weakness 4. Modifies individual behaviors (e.g., punishment, expulsion from program) 5. Is limited in scope The systems approach: 1 . Focuses on the environment and the working conditions 2. Holds the organization accountable 3. Sees susceptibility to error as a systematic weakness 4. Intervenes by modifying processes 5. Builds in defenses and safeguards to prevent error After the error (with both approaches): 1 . Recognize the error and disclose it 2. Consider consequences and outcomes 3. Take appropriate action 4. Perform a root cause analysis 5. Follow up to make changes
Clinicians need to develop habits of mind to guard themselves against mistakes of this sort, and some of those habits are listed in Box 25.2 [2].
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Box 25.2 Habits of Mind to Avoid Simple Errors 1. Respect the potency of intravenous, intrathecal, and epidural medications. 2. Examine the kit and practice in a non-clinical setting. 3. Have a checklist, system, and routine. 4. Be hyper-vigilant when deviating from your routine. 5. Give yourself permission to remove distractions (e.g., asking for silence). 6. Use labels. 7. Check and double-check labels. 8. Clear your visual field. 9. Develop and pay attention to internal alarms (slow down).
The patient was very lucky not to have suffered harm from this mishap. It was, indeed, a “near-miss.” Since the resident did not inspect the label at all, the medication could have been some agent not at all appropriate for intrathecal injection. By good fortune, he administered an appropriate volume of hyperbaric 5% lidocaine in dextrose, rather than the bupivacaine he had wanted to give. Intrathecal lidocaine is no longer used very often because of the risk of the transient neurologic syndrome (TNS), the characteristics of which are summarized in Box 25.3 [3]. It should be noted, however, that hyperbaric lidocaine was used in obstetric anesthesia for decades with excellent results, and cases of TNS with lidocaine were seen very rarely or not at all in obstetric patients. Of course, this fact in no way justifies the resident’s error. Box 25.3 Transient Neurologic Syndrome (TNS) with Intrathecal Lidocaine 1. Only rare reported cases of TNS in obstetric patients. 5% hyperbaric lidocaine was used for decades in obstetric anesthesia with excellent results. 2. Pain in low back and thighs. 3. Onset 1–24 h after the block. 4. May last 7–10 days. 5. No loss of motor, bowel, or bladder function. 6. Rare paresthesias. 7. May respond to NSAIDs. 8. More common with lithotomy position and knee surgery. 9. More common with doses of 80–100 mg.
References 1. Reason J. Human error: models and management. West J Med. 2000;172(6):393–6. 2. This list is adapted from an anonymous resident’s presentation. 3. Zaric D, Pace NL. Transient neurologic symptoms (TNS) following spinal anaesthesia with lidocaine versus other local anaesthetics. Cochrane Database Syst Rev. 2009;(2):CD003006.
Chapter 26
Headache After Dural Puncture with an Epidural Needle Thomas L. Archer
Case Presentation An anesthesiologist is attempting to perform a labor epidural for a patient with severe labor pain who is straining and vocalizing, but immediately after the loss of resistance, he feels another pop and cerebrospinal fluid flows back into his syringe (L-1). He leaves the Tuohy needle where it is, replaces the stylet, and then quickly threads the “epidural” catheter 3 cm into the subarachnoid space after removing the stylet (L-2). Applying counter-pressure against the catheter so as not to pull it out of the subarachnoid space, he removes the Tuohy needle and says to the patient, “I’m afraid I made a hole in that membrane called the dura I told you about, so we should be able to give you good pain relief for labor but you might get a headache later on. We’ll be following you very closely afterwards” (L-3). He aspirates the intrathecal catheter with the 3 mL syringe and obtains free flow of cerebrospinal fluid (L-4). He doses the subarachnoid spinal catheter with 25 mcg of fentanyl and 1.25 mg of 0.25% bupivacaine (total volume 1 mL) and flushes the catheter with 0.5 mL of normal saline (L-5). Before taping the catheter to the skin, he performs a “Cohen Maneuver” to make sure that movement of the patient’s subcutaneous tissue doesn’t pull the catheter out of the subarachnoid space (L-6). The patient gets excellent pain relief for labor immediately and is still able to move her legs. The anesthesiologist tapes the subarachnoid catheter up the patient’s back to her left shoulder but does not yet connect the infusion he had planned to use epidurally (L-7). The patient’s level of cold sensation gets established at T6 and she has some hypotension which the anesthesiologist treats with IV fluid, left-sided positioning, and phenylephrine. He carefully explains to the patient what happened, and that it
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_26
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shouldn’t cause any problems except for the fact that she may get a headache after she delivers or the following day. The anesthesiologist then carefully informs the nurses, the OB team, and the other anesthesia provider on duty with him of what has happened, and writes “intrathecal catheter” on the L&D whiteboard opposite the patient’s name (L-8). He tells the patient and the nurse that he wants to make sure that the catheter is functioning properly and so he is not going to start the infusion right away, but rather he wants the patient to have the nurse contact him as soon as she starts to feel labor pain again, so that he knows how long the analgesia lasts and can then dose the catheter and start the intrathecal infusion personally (L-9). The patient starts to feels labor pain again after about 75 min and the anesthesiologist doses the intrathecal catheter again with 25 mcg of fentanyl and 0.625 mg of bupivacaine and starts the intrathecal infusion of 0.1% bupivacaine and 2 mcg/mL fentanyl at 1 mL per hour. The patient has excellent pain relief for her labor and for her cesarean delivery for failure to progress. For the cesarean delivery, the anesthesiologist carefully titrates the level of anesthesia with 0.5% isobaric bupivacaine after injecting morphine 100 mcg and fentanyl 15 mcg. At the end of the surgery, the anesthesiologist removes the epidural catheter and puts a sterile dressing over the hole in the skin (L-10). The following day the patient complains of a typical frontal-occipital headache radiating into her shoulders which appears a few seconds after she sits up and disappears when she lies down. The anesthesiologist apologizes for the complication and the patient opts for conservative therapy for 24 h to see how the headache evolves (L-11). By the next morning, the patient says that her headache is getting better and that she can get up for short periods of time before her head starts to hurt. She chooses not to have an epidural blood patch but to continue with conservative management. The following day the headache has disappeared (L-12).
Lessons Learned Lesson 1 It is important not to attempt to enter the epidural space while the patient is straining, vocalizing, or holding her breath during a contraction. The contraction itself, plus any degree of Valsalva maneuver, engorges the epidural veins, makes the dura tense, and makes either a “wet tap” or a “bloody tap” a much more likely occurrence.
Lesson 2 The subarachnoid catheter should not be advanced farther than 4 cm into the subarachnoid space in order to avoid touching the conus medullaris of the spinal cord, which could cause the conus medullaris syndrome. Some practitioners do not use subarachnoid catheters at all in this situation. Rather, they attempt another epidural
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placement at another interspace. Those who do use intrathecal catheters argue that the “damage” (the hole in the dura) has already been done and that one may as well take advantage of the access to the CSF that has been achieved—as long as the subarachnoid catheter is used with the utmost care.
Lesson 3 It is best to inform the patient immediately when an unforeseen event occurs.
Lesson 4 He draws back to get CSF for two reasons: (1) to confirm intrathecal placement of the catheter, since it could be subdural or intradural (which would not be acceptable), and (2) to remove all the air from the catheter to prevent pneumocephalus when he injects local anesthetic into the CSF.
Lesson 5 The dead space of an epidural catheter is approximately 0.3 mL and the anesthesiologist wants to make sure that all of the local anesthetic mixture gets into the CSF.
Lesson 6 The Cohen Maneuver has been described in Chap. 22, but in brief its purpose is to prevent movement of the patient’s subcutaneous tissue from pulling the catheter out of the epidural or subarachnoid space.
Lesson 7 Some practitioners will connect an appropriately low-dose infusion immediately under these circumstances, whereas others like to wait and make sure that the catheter is behaving as a subarachnoid catheter should and that it is not—for example— behaving like a subdural catheter (by causing a widespread, patchy block). In either case, the catheter used in this non-routine way should be the object of very careful scrutiny to make sure that neither too little nor too much analgesia is provided and that there is no indication of abnormal placement or neurological damage.
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Lesson 8 The entire L&D team needs to know that this “epidural catheter” is not in the epidural space! Everyone on the team needs to have a heightened sense of awareness about this patient, so that no one injects an epidural-sized dose of local anesthetic into the subarachnoid space. It also puts the entire team on notice that this patient is at high risk for developing a PDPH.
Lesson 9 Some practitioners like to be sure that the catheter is functioning normally and that the numbness wears off normally. If there were neurological damage, the numbness would not wear off and it would be highly important to know that fact.
Lesson 10 Since the needle path had communicated with the subarachnoid space, some practitioners feel more comfortable protecting the sterility of the needle puncture site to a greater extent that if it were “just” an epidural puncture.
Lesson 11 Box 26.1 presents the diagnosis and therapy of a post-dural puncture headache. The best new idea in the last 10 years for treating these headaches appears to be that of sphenopalatine ganglion blockade (see the next lesson).
Box 26.1 Post-dural Puncture Headache (PDPH) Characteristics: 1. Symmetrical, frontal-occipital, can radiate into shoulders. Sometimes associated with nausea, rarely associated with hearing problems or abducens nerve palsy. 2. Provoked within seconds to minutes by upright posture, relieved by supine posture. 3. Usually starts 24 h after dural puncture, but can occur more quickly after a large bore needle puncture.
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Principles of management: 1. Not all postpartum headaches after neuraxial anesthesia are due to dural puncture! Postpartum headache is common. Take a careful history to rule out alternative diagnoses. 2. Usually resolves spontaneously within 7 days, but can be disabling in an active woman with multiple responsibilities. Reassurance and oral analgesics may be sufficient therapy. Remain available to the patient. 3. Continued conservative therapy may be indicated if patient tolerates upright posture at all. 4. If diagnosis of PDPH is made, therapy should match the extent of symptoms and the needs of the mother. 5. Many practitioners try to wait 24 h before performing epidural blood patch (EBP). 6. Headache with atypical features (e.g., atypical location, fever, or focal neurological signs) should rapidly prompt a search for other diagnoses. 7. Brain imaging is recommended after two failed epidural blood patches (and for headaches with atypical features). Alternative diagnoses: 1. Preeclampsia 2. Tension headache, migraine, caffeine withdrawal, ondansetron administration 3. Breast-feeding headache (“lactation headache“—probably due to oxytocin release) 4. Sinus infection, cortical vein thrombosis, subarachnoid hemorrhage, meningitis, subdural hematoma, brain tumor Therapy: 1. Conservative therapy is hydration, salt intake, caffeine, and oral analgesics. 2. Sphenopalatine block with local anesthetic on cotton swab is a possible new therapy [1]. 3. Epidural blood patch is the “gold standard,” but disadvantages are: it is a second invasive procedure and only 60–90% effective. Risks include infection (rare) and transient leg and back pain. 4. The commonly recommended volume of blood is 20 mL, injected slowly and stopped early for increased back discomfort or pressure.
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Lesson 12 This patient and her anesthesiologist were fortunate in this case. Dural puncture with a large bore epidural needle carries about a 50% rate of highly symptomatic PDPH. If the patient had had severe and disabling symptoms, the practitioner might have wanted to do the blood patch before the recommended wait of 24 h. Figure 26.1 shows the two theories for explaining PDPH. The first theory (B) is that of “vasodilation” which suggests that decreased intracranial pressure forces the
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Vasodilation theory
= Normal intracranial blood vessel
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c
Traction theory = Brain “floating” in CSF
= Intracranial vessel painfully dilated by low intracranial pressure = Traction on dura as brain sinks downward = Intracranial blood vessel allowed to contract by pressure from blood patch = Movement of CSF and/or brain
= Epidural blood patch
= CSF within dura
= CSF escaping through needle hole in dura
Fig. 26.1 Theories of post-dural puncture headache (PDPH). (a) represents the normal situation in which adequate volumes of cerebrospinal fluid (CSF) surround the brain and spinal cord and allow the brain to “float” comfortably within the skull—with neither painful traction on the dura nor painful dilation of blood vessels. (b) represents the vasodilation theory of post-dural puncture headache, in which loss of spinal fluid causes CSF pressure within the head to decrease when the patient assumes an upright posture. This intracranial hypotension forces or “pulls open” blood vessels so that they take up the volume formerly occupied by CSF. (c) represents the traction theory of PDPH, in which loss of CSF forces the brain to move in a caudad direction within the skull when the patient is upright, thereby pulling on the dura and other intracranial pain-sensitive structures. (d) shows how an epidural blood patch may restore intracranial CSF volume and pressure, thereby reversing both of the proposed mechanisms. Abbreviation: CSF cerebrospinal fluid
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dilation of blood vessels within the brain. The fact that vasoconstrictors such as caffeine, ergot alkaloids, and sumatriptan are somewhat efficacious in relieving the pain of a PDPH supports the vasodilation hypothesis. The second theory (C) is that of “traction” of the “sagging” brain on the dura and other pain sensitive structures within the skull. Of course, both explanations may be true. A relatively new development is that of sphenopalatine ganglion block, which is performed as follows: lidocaine on cotton swab applicators is applied to the back of the nasopharynx and left in place for 10 min. This therapy appears to work reasonably well, although it is temporary and may have to be repeated [1].
Reference 1. Up To Date: https://www.uptodate.com/contents/post-dural-puncture-headache?search= sphenopalatine%20ganglion%20block&source=search_result&selectedTitle=1~4&usage_ type=default&display_rank=1. Accessed 4/19/2019.
Chapter 27
Neurological Deficit After Neuraxial Analgesia for Labor and Vaginal Delivery Thomas L. Archer
Case Presentation The next day when the anesthesiologist visits the patient on post-delivery rounds (L-1), she complains of trouble with her right foot. Neurological examination reveals weakness in dorsiflexion of the foot (foot drop) and numbness in the great toe. The rest of her neurological exam is normal—specifically, she denies trouble with urination or defecation and any other numbness or weakness in the lower extremities. She is concerned that the epidural may have caused the problem and wants to know if it will get better (L-2). The anesthesiologist explains to the patient that what she has is probably an “obstetric palsy,” that is, a neurological problem caused by the birth process itself, rather than the anesthesia. In this instance, he explains, the deficit may be due to the pressure of the baby’s head on nerves called the “lumbosacral trunk” at the pelvic brim, which is the entrance to the pelvis from above. The anesthesiologist reminds the patient that she had severe “back labor” and says that that pain may have been caused by the back of the baby’s head rubbing against those very nerves as the baby’s head came through the pelvis. He reassures the patient that the neurological deficit will probably get better over the next few days but adds that he is going to ask a neurologist to see her in order to get another expert evaluation of the lesion and for follow-up, including any physical therapy or orthopedic appliances that may be required (L-3). After reassuring the patient, the anesthesiologist promises to come back the next day to check on her and he then alerts the nurses to the fact that the patient will have
Note: This chapter continues the case begun in Chapter 19. T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_27
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trouble walking and will need assistance. He also informs the obstetric team of what has happened and they agree to have Physical Therapy see the patient. The next day, the strength and sensation in the foot have improved and by the third day after delivery the patient says her foot is back to normal (L-4).
Lessons Learned Lesson 1 Visiting patients the day after they deliver is a very satisfying activity which contributes to our role and image as perioperative physicians. It also allows one to personally detect any complications that may be attributed to anesthesia care, such as nerve deficits.
Lesson 2 Transient neurological deficits after neuraxial anesthesia and delivery are not uncommon and the anesthesiologist always is concerned that her block may have caused nerve damage. The etiology of the nerve deficit is almost always something other than the neuraxial block itself (see Fig. 27.1), and the anesthesiologist should evaluate the patient with that reassuring knowledge in mind.
Lesson 3 Obtaining a neurologist’s consultation on the patient has value for several reasons: (1) It shows that the problem is being taken seriously, (2) it makes sure that nothing else is being missed (such as multiple sclerosis, a generalized neuropathy, or a spinal cord or root lesion), and (3) it helps with prognosis and rehabilitation (including short-term bracing), should that be required.
Lesson 4 Of course, most patients would have been discharged from the hospital before the third postpartum day! If the patient has been discharged, the anesthesiologist should follow up with a phone call and any referrals required. It is extremely important for the anesthesiologist to follow up on any post-delivery neurological deficits, secure
27 Neurological Deficit After Neuraxial Analgesia for Labor and Vaginal Delivery
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Pregnant abdomen
LS
1 2
Buttocks 3
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OR table Perineum Mother’s back
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Fig. 27.1 Four possible causes of nerve damage after vaginal or cesarean delivery under neuraxial block: (1) Lateral femoral cutaneous (L2–3) or femoral nerve (L2-4) stretched at inguinal ligament. (2) Lumbosacral trunk (L4-5) or obturator nerve (L2-4) compressed by fetal head at pelvic brim. (3) Sciatic nerve (L5-S2) in buttock, pressure after emerging from sciatic notch, often caused by operating room table. (4) Mechanical or chemical damage from needle insertion or injection at any level. Abbreviation: LS lumbar spine
in the knowledge that the vast majority of them will have been caused by something other than neuraxial anesthesia, such as nerve compression or stretch. Reynolds [1] makes the point, however, that anesthesia cannot be entirely absolved in some of these cases, since numbness and weakness make it possible to position the patient inappropriately. Specific nerve lesions and precautions to prevent them are shown in Tables 27.1 and 27.2 [2]. How do we distinguish between spinal root lesions (perhaps caused by our neuraxial block) and peripheral nerve lesions, which are probably “obstetric palsies?” The phenomenon of “dorsal sparing” can be useful in making that distinction. Figure 27.2 depicts the fact that motor and sensory roots within the cerebrospinal fluid (CSF) innervate both the ventral and dorsal rami of the mixed spinal nerves, and Fig. 27.3 shows that lesions of the spinal roots will affect both the dorsal and ventral rami, and will thus affect the paraspinous muscles innervated by the dorsal rami. Peripheral nerve lesions, on the other hand, as seen in Fig. 27.4, will only affect structures innervated by the ventral rami and will spare structures innervated by the dorsal rami. So if there is no evidence of damage to the dorsal rami innervating the paraspinous muscles, it suggests that the nerve lesion is peripheral, and this observation would tend to exonerate the anesthesiologist’s needle from the accusation of having caused the neurological deficit.
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Table 27.1 Signs and symptoms of obstetric palsies and other nerve lesions Nerve Lateral femoral cutaneous nerve Lumbosacral trunk Obturator nerve Sciatic nerve Common peroneal nerve Femoral nerve Cauda equina Intravertebral spinal root
Signs, symptoms, and comments Numbness or burning lateral thigh. No motor signs. Common in pregnancy before labor. “Meralgia paresthetica.” Foot drop, numbness great toe Numbness inner thigh, weak hip adduction Weakness of both dorsi- and plantarflexion of foot. Numbness in foot Foot drop, numbness great toe Weakness in extension at the knee. Patellar reflex decreased or absent. Trouble climbing stairs Cauda equina syndrome (highly variable presentation) Dermatomal signs and symptoms do not follow peripheral nerve distribution. Damage to dorsal or ventral spinal roots emerging from the spinal cord will affect both dorsal and ventral rami. “Dorsal sparing” of the paraspinous muscles suggests a peripheral nerve lesion, rather than nerve damage from a needle inserted into the spinal canal (see Fig. 27.4)
Table 27.2 Causes and prevention of obstetric palsies Nerve Lateral femoral cutaneous (“meralgia paresthetica“) Femoral
Cause Tissue swelling of pregnancy or lithotomy position. Most common neuropathy in pregnancy and after delivery
Prevention Reassurance Reduce hip flexion between contractions while pushing
Prolonged hip flexion
Lumbosacral trunk Obturator Sciatic
Pressure from fetal head at pelvic brim
Common peroneal
Lateral pressure on nerve at fibula, below knee Prolonged squatting
Reduce hip flexion between contractions CD for cephalopelvic disproportion Avoid very prolonged pushing Avoid sciatic pressure when tilting patient on OR table for CD Minimize CD duration Careful positioning Frequent position change
Pressure from OR table Prolonged sitting
Abbreviations: CD cesarean delivery, OR operating room
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Posterior Dorsal rami to paraspinous muscles
Sensory spinal root DRG Spinal cord MSN Motor spinal root
Ventral rami to lower extremities Anterior
Fig. 27.2 Spinal roots and dorsal and ventral rami of mixed spinal nerves. Sensory and motor roots innervate both the dorsal and ventral rami of the mixed spinal nerves. Abbreviations: DRG dorsal root ganglion, MSN mixed spinal nerve
Dorsal ramus
Needle damage to either root affects both dorsal and ventral rami
Paraspinous muscle lesion
Ventral ramus Lower extremity lesion
Fig. 27.3 Needle damage to the spinal cord or spinal roots (the lesion labeled #4 in Fig. 27.1) will show up in both the ventral and dorsal rami and hence the paraspinous muscles will be affected, as well as the lower extremities
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Dorsal sparing of paraspinous muscles with peripheral nerve or plexus lesion
Lower extremity lesion Peripheral nerve or plexus damage
Fig. 27.4 Dorsal sparing. When peripheral nerves are damaged—as in obstetric palsies of types #1, #2, or #3 in Fig. 27.1—there will be no damage to the dorsal rami of the spinal nerves and the paraspinous muscles will be unaffected. Demonstration of dorsal sparing would tend to exonerate the anesthesiologist as the direct cause of a neurologic lesion after a neuraxial anesthetic
References 1. Reynolds F. Chapter 32 of Chestnut’s obstetric anesthesia, principles and practice. In: Neurologic complications of pregnancy and neuraxial anesthesia. 5th ed. Philadelphia: Elsevier Saunders; 2014. p. 744. 2. Tables 1 and 2 draw heavily on information in Dr. Reynolds’ excellent chapter cited above.
Chapter 28
Left Sciatic Neuropathy After Cesarean Delivery in an Obese, Diabetic Patient Thomas L. Archer
Case Presentation A 31-year-old woman, G3P2, presents electively near term for her third cesarean delivery (CD). Her pregnancy has gone well and her baby is of normal estimated fetal weight, but the patient is obese and has had Type 2 diabetes for 10 years, which has been poorly controlled at times (L-1). The obstetrician tells the anesthesiologist that the surgery may take longer and have more bleeding than usual, because the operative report from the last CD described a lot of adhesions and bleeding. When he hears this, the anesthesiologist decides to administer a combined spinal-epidural anesthetic (CSE) to be able to prolong the block if necessary. CSE block placement goes smoothly and the patient gets a solid T2 level for cold sensation to ice wrapped in a rubber glove. Before preparation of the skin, the patient is tipped over to her left side with a right flank roll in such a way as to avoid pressure on the right sciatic nerve in the buttock (L-2). Surgery proceeds with care; the baby is vigorous when delivered and bleeding is minimized, but surgery lasts almost 2 hours and the anesthesia resident has to dose the epidural catheter with 5 mL of 2% lidocaine with epinephrine 1:200,000 plus fentanyl 100 mcg in order to extend the duration of anesthesia. The day after surgery, the patient complains of weakness and numbness in the left foot and an inability to walk. Neurological examination by the anesthesiologist reveals numbness of the left foot and severe weakness of the foot and great toe for both dorsi- and plantarflexion. Despite the hopes of her caregivers, the patient’s recovery is not rapid. She is seen by the Neurology service who diagnose a left sciatic neuropathy [1], and she is fitted for a foot brace and seen by Physical Therapy.
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_28
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Six weeks after delivery, the patient still has weakness in her left foot, but it seems to be gradually getting better (L-3).
Lessons Learned Lesson 1 It is not diabetes per se that causes end-organ damage, but rather the hyperglycemia associated with poor control. The organs most commonly damaged by hyperglycemia are the eyes, kidneys, peripheral nerves, and blood vessels (including the heart), and the end-organ damage is due to inflammation: increased vascular permeability and white cell and platelet activation—similar to what happens in preeclampsia.
Lesson 2 During cesarean delivery, the patient is usually tipped to the left in order to minimize obstruction of the inferior vena cava by the pregnant uterus and thereby maximize venous return. The bolster or pillow used for tilting the patient should be soft and large and should put pressure on the right flank area or bony pelvis, and not on the right sciatic nerve in the buttock. Right sciatic palsies have occurred when a bag of IV fluid under the right buttock has been used to tilt the patient to the left, causing pressure on the right sciatic nerve and subsequent neuropathy. Unfortunately, left sciatic neuropathy can also be seen after CD, presumably from the extra pressure on the left sciatic nerve due to the pelvic tilt. These possible mechanisms for sciatic nerve damage at CD are shown schematically in Fig. 28.1, Panels A, B, and C
Lesson 3 An attempt to avoid both left and right sciatic neuropathy at CD can be made by removing the flank roll from the patient’s right side after delivery, as shown in Fig. 28.1, Panel A. This restoration of the full supine position may evenly distribute
28 Left Sciatic Neuropathy After Cesarean Delivery in an Obese, Diabetic Patient
a
b
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c
= Sciatic nerve, minimized pressure = Minimized risk = Sciatic nerve, no pressure, seen through flank bolster = Sciatic nerve, compressed by OR table or buttock bolster
= Potential sciatic nerve damage = Bolster under flank (B) or buttock (C). = OR table
= Bony skeleton L
R
= Patient’s buttocks = Patient’s head
Fig. 28.1 Left or right sciatic nerve damage from positioning with leftward tilt at cesarean delivery. With a prolonged leftward tilt of the patient during cesarean delivery, the left sciatic nerve is always at risk. The right sciatic nerve can also be damaged, if the bolster to tilt the patient is mistakenly placed under the right buttock. Removal of the tilting flank bolster after delivery to distribute the pressure evenly between the two sciatic nerves may help to prevent this problem. Abbreviations: L left, OR operating room, R right
the pressure of the OR table between the two sciatic nerves in the buttocks and thereby lessen the chance of excessive pressure on any one nerve, but this theory for prevention of sciatic palsy at CD has not been studied. Duration of surgery and hypotension may also be factors contributing to sciatic neuropathy.
Reference 1. Postaci A, Karabeyoglu I, Erdogan G, Turan O, Dikmen B. A case of sciatic neuropathy after caesarean section under spinal anaesthesia. Int J Obstet Anesth. 2006;15(4):317–9. Epub 2006 Jun 13.
Chapter 29
Vasopressin, Used as a Vasopressor During Cystoscopy, Causes Non-reassuring Fetal Status Thomas L. Archer
Case Presentation A 29-year-old pregnant woman, G2P1 at 36 weeks estimated gestational age, had a kidney stone with left hydronephrosis and was undergoing cystoscopy and stone removal under spinal anesthesia. During surgery the fetal heart rate (FHR) and uterine contractions were being monitored externally by a labor and delivery nurse. The anesthesia provider—who did not usually take care of pregnant patients—was relieving the regular provider for lunch. The regular provider had been supporting the blood pressure as needed with phenylephrine, but the relieving provider decided to use what he thought was a small dose of vasopressin to support the blood pressure, since he was accustomed to using that medication in cardiac surgery patients (L-1). Shortly after the anesthesia provider gave the vasopressin, the labor and delivery nurse who was monitoring the FHR reported that the fetus’ heart rate had fallen from 160 to 60. She palpated the uterus and found that it was tightly contracted (L-2). Subcutaneous terbutaline 0.2 mg and 50 mcg of nitroglycerin IV were required to relax the uterus and restore the FHR to normal. Intravenous phenylephrine was used to support the blood pressure after nitroglycerin administration and as needed during the rest of the case (L-3).
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_29
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Lessons Learned Lesson 1 Figure 29.1 (not the pregnant patient presented in the case) shows the hemodynamic effects of a dose of phenylephrine followed by the effects of a dose of vasopressin. Both medications increase the blood pressure by increasing the systemic vascular resistance, but vasopressin—unlike phenylephrine—makes the uterus contract as well (not shown in this figure). Using vasopressin for routine blood pressure support in a pregnant patient under spinal anesthesia was a serious blunder that could have asphyxiated the fetus.
Lesson 2 Uterine contractions deprive the placenta of perfusion and stop oxygen delivery to the fetus. Sustained uterine tetany would kill the fetus. Figure 29.2 shows a comparison of the various physiological effects of oxytocin and vasopressin, which are structurally similar hormones and are both secreted by the posterior pituitary gland. Oxytocin and vasopressin both cause uterine smooth muscles to contract, whereas oxytocin dilates vascular smooth muscle but vasopressin constricts it.
Phenylephrine
Vasopressin
8 CO 0 3000 SVR 0 200 BP 0 SV
150
HR 0 0
15 Minutes
30
Fig. 29.1 Like phenylephrine, vasopressin increases blood pressure by increasing systemic vascular resistance. Note: This is NOT the patient in the presented case, but is shown here as a hemodynamic illustration of the two vasopressors, phenylephrine and vasopressin. Hemodynamic data shown was derived from the LidCO system and arterial line in a non-pregnant patient
29 Vasopressin, Used as a Vasopressor During Cystoscopy, Causes Non-reassuring… Uterine tone
Arteriolar tone
Collecting ducts
Social behavior
Oxytocin
Contracts pregnant uterus
Vasodilator
Retains water
Modulates behavior
Vasopressin (ADH)
Contracts pregnant uterus
Vasoconstrictor
Retains water
Modulates behavior?
= Normal, physiological and desired effects
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= Possibly harmful “side effects”
Fig. 29.2 Oxytocin and vasopressin are both nonapeptides secreted from the posterior pituitary gland and their structures differ only with respect to two amino acid positions. As shown in this figure, they have many overlapping and contrasting functions and activities. The “normal,” sought- after or physiological “effects” are shown in green, whereas the undesirable “side-effects” are shown in red. The yellow box for vasopressin’s effect on social behavior indicates that this is an emerging area of research. The anesthesia provider in this case did not know or remember the fact that vasopressin can cause uterine contractions in higher doses and should be used in pregnant patients only if clearly necessary. Abbreviation: ADH antidiuretic hormone (another name for vasopressin—also called arginine vasopressin)
Lesson 3 Nitroglycerin relaxes both uterine and vascular smooth muscle and can decrease the blood pressure to a dangerous degree. If sublingual or intravenous nitroglycerin is used during labor as part of intrauterine resuscitation in a case of uterine hyperstimulation, care must be given to supporting the maternal blood pressure. Alpha agonist vasopressors such as phenylephrine have no important effect on uterine smooth muscle.
Chapter 30
Emergency Cesarean Delivery After Repair of an Ankle Fracture Thomas L. Archer
Case Presentation A 34-year-old woman, G1P0 and at 36 weeks estimated gestational age, slips on the stairs at home and fractures her right ankle (L-1). She is otherwise in good health and last ate 2 h before her injury. The orthopedists feel that the fracture needs to be repaired immediately since there are signs of neurovascular compromise at the ankle. The patient is afraid of the effect of general anesthesia on the baby and is happy when the anesthesia provider suggests that a spinal anesthetic would be a good technique in her case. He says that he will add morphine and fentanyl to the intrathecal mixture, thereby giving her some pain relief for the first 24 h after surgery. Her pregnancy has gone well so far and the patient is quite sure that she did not hit her abdomen when she fractured her ankle. She denies vaginal bleeding, contractions or uterine tenderness (L-2). The labor nurse and OB resident checked the fetal heart rate before surgery and found a normal tracing, with an FHR of 150 and with good FHR variability (L-3). The labor nurse had been intending to stay to monitor the fetus during surgery, but got called away by emergencies occurring in Labor & Delivery (L-4). The anesthesia provider administers the spinal anesthetic easily, using bupivacaine 12 mg, morphine 100 mcg, and fentanyl 25 mcg as the intrathecal dose and achieves the T4 level which he had intended, knowing that the orthopedic team plans to use a tourniquet (L-5). The anesthesia provider uses phenylephrine and ephedrine to support the BP and gives the patient small doses of fentanyl and midazolam for anxiety. Unfortunately, surgery lasts much longer than anticipated and
T. L. Archer (*) Department of Anesthesiology 2008–2015, University of California San Diego School of Medicine, San Diego, CA, USA © Springer Nature Switzerland AG 2020 T. L. Archer (ed.), Obstetric Anesthesia, https://doi.org/10.1007/978-3-030-26478-9_30
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the spinal begins to wear off (L-6). The orthopedists deflate the tourniquet to remove that source of pain, but the anesthesia provider is still forced to administer GA to the patient because of continuing pain from ongoing surgery. During general anesthesia, the anesthesia provider conscientiously maintains the blood pressure within the patient’s normal range and maintains the end tidal CO2 at about 30 mm Hg (L-7). He also makes sure that the patient remains positioned with her pelvis and uterus well tilted to the left, and he adjusts the flank roll (“hip roll”) from time to time, making sure that nothing is pressing on the right sciatic nerve in the buttock (L-8). At the end of surgery, the labor and delivery nurse returns to the OR to check the FHR. The fetal heart rate is 150 but there is no beat-to-beat variability at all! The nurse has been taught that loss of beat-to-beat variability (which had been present prior to surgery) indicates fetal hypoxia (L-9). She is alarmed and calls for the OB resident to come down STAT to the OR. He too is alarmed, calls his attending, and with another resident’s help performs an emergency cesarean delivery in the same OR where the ankle surgery had been performed, since their interpretation of the fetal heart rate tracing was that the fetus was severely hypoxic (L-10). The baby was born very floppy and the neonatologist who was called STAT to the orthopedic OR had to ventilate her with a bag and mask for several minutes before she became vigorous. Umbilical artery blood gas results were: pH = 7.34, pO2 = 20 mm Hg, pCO2 = 50 mm Hg, HCO3 = 22 mEq/L, and base deficit = 2.5 mEq/L (L-11). The baby had to spend 2 days in the neonatal intensive care unit because of breathing difficulties, but then acted normally. The mother made an uneventful recovery from anesthesia and the intrathecal opioids served her well for the pain of both her ankle surgery and her cesarean delivery. When the case was investigated later by the hospital’s Quality Improvement Committee, it was determined that neither the anesthesia provider nor the OB resident had known that general anesthesia eliminates FHR variability—not because it causes fetal hypoxia, but simply because it puts both the maternal and the fetal cortex to sleep (L-12), and it is an awake and functioning fetal cortex which generates FHR variability.
Lessons Learned Lesson 1 Box 30.1 presents two very “high level” approaches to trauma care for pregnant women: (1) In severe trauma, pregnancy is a secondary consideration and resuscitation of the mother is the only concern, and (2) in minor trauma, the main worry is placental abruption. Needless to say, this box is not presented as an algorithm for diagnosis or treatment, but simply as an orientation as to how the subject of trauma in pregnancy is often discussed.
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Box 30.1 Two Different General Approaches to Trauma in the Obstetric Patient are Discussed Below Severe trauma: 1 . Pregnancy is completely secondary and incidental to management. 2. Stabilize mother first in terms of airway, breathing, circulation. 3. Use any diagnostic studies (including X-ray with shielding if practical) that would be indicated in a non-pregnant patient. 4. Emptying the uterus may be a beneficial part of resuscitation. Minor trauma: 1 . Placental abruption can occur with minor trauma. 2. Observe patient for 4–24 h, depending on the absence or presence of the following signs: vaginal bleeding, greater than six contractions per hour for 4 h, uterine tenderness, fetal heart rate decelerations, or tachycardia. Note: These two approaches are not mutually exclusive or meant as a guide to management. They are presented as two common overviews in discussions of trauma in the pregnant patient.
Lesson 2 Placental abruption can occur after minor abdominal trauma, since the relatively liquid placenta can easily shear off from the elastic myometrium when the uterus suffers an impact. The fetal heart rate in abruption will eventually show late decelerations or fetal tachycardia as the abrupting placenta is progressively unable to supply the fetus with oxygen. After trauma, vaginal bleeding, more than six contractions per hour for 4 h and uterine tenderness are all “red flags” suggesting possible abruption, and in the presence of any of those signs, 24 h of external monitoring may be indicated. If none of these signs are present—and if the fetal heart rate tracing is normal—4 h of monitoring is considered sufficient before discharge [1].
Lesson 3 Figure 30.1 shows an awake fetal cortex varying its sympathetic and vagal stimulation to a well-oxygenated fetal heart, thereby generating the normal fetal heart rate variability of 6–25 beats per minute in a normal baseline heart rate of 110–160 beats per minute. Loss of beat-to-beat variability is completely normal in a fetus whose cerebral cortex is sharing its mother’s general anesthesia! In an unanesthetized and unsedated
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Awake and well-oxygenated fetal cortex produces FHR variability due to its varying vagal and sympathetic output to the heart.
Alert fetal cerebral cortex
Alert medulla
Vagal afferents from AAC and AAB are silent for hypoxemia and hypertension.
Normal vagal tone AAC
Well oxygenated myocardium produces FHR = 110-160 beats/min with beat-to-beat variability:
AA
Aortic arch baroreceptor (AAB) not triggered by hypertension B
Aortic arch chemoreceptor (AAC) not triggered by hypoxemia
Aortic arch
Fig. 30.1 In an awake and well-oxygenated fetus, the active cerebral cortex varies its sympathetic and vagal input to the heart, thereby generating fetal heart rate variability. Abbreviations: AAB aortic arch baroreceptor, AAC aortic arch chemoreceptor, FHR fetal heart rate
fetus, loss of beat-to-beat variability suggests that the fetal cortex may be depressed by hypoxia, but such loss of FHR variability with a normal FHR is completely normal in an anesthetized fetus. On the other hand, if there had been both fetal bradycardia and loss of FHR variability, that would have been highly suggestive of fetal hypoxemia (in the absence of maternal beta blocker administration).
Lesson 4 Historically, a common practice has been to look at the fetal heart rate before and after surgery “to document that the fetus is OK,” but it is better to monitor the FHR continuously during surgery—as we would monitor the function of other maternal “organs”—since we may be able to make adjustments intraoperatively to improve the fetus’ condition, such as maternal position change, transfusion, raising the blood pressure, or removing positive end-expiratory pressure (PEEP). Of course fetal heart rate monitoring may not be possible during abdominal surgery, at least without sterile equipment that can be used on the surgical field.
Lesson 5 It requires a high dermatomal level to block tourniquet pain, and even then tourniquet pain “breaks through” the block eventually. Also, when the tourniquet is deflated, lactic acid will flood into the maternal circulation causing both metabolic
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and respiratory acidosis. These metabolic changes in the mother after tourniquet deflation would be another reason to monitor the fetus during surgery and would necessitate adjustments of ventilation to keep the end tidal CO2 around 30 mm Hg, as was done in this case.
Lesson 6 A combined spinal epidural (CSE) anesthetic would have been a better choice than a single-shot spinal.
Lesson 7 The arterial pCO2 at the end of pregnancy is about 30–32 mm Hg and there is normally very little end-tidal to arterial gradient for CO2 during pregnancy because of the increased blood volume and reduced or absent alveolar dead space (i.e., all the alveoli are perfused). For this reason, end-tidal CO2 usually is very close to arterial pCO2 in pregnant patients (in the absence of positive end-expiratory pressure or hypovolemia, which will both increase alveolar dead space.)
Lesson 8 See Chap. 28, as well, regarding sciatic nerve compression during cesarean delivery.
Lesson 9 The Labor and Delivery nurse and the OB resident saw the tracing schematically represented in the lower left corner of Fig. 30.2: a completely fixed heart rate with no beat-to-beat variability at all.
Lesson 10 Fetal hypoxia would have caused fetal bradycardia (or perhaps tachycardia, early on), but loss of FHR variability is normal for an anesthetized fetus. A much more common cause of the loss of FHR variability is the maternal administration of opioids (e.g., fentanyl) during labor, and the obstetric anesthesiologist needs to inform the obstetrician of such administration.
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Anesthetized fetal cerebral cortex
Zz
Anesthetized medulla Vagal afferents from AAC and AAB are silent for hypoxemia and hypertension.
AAC Well oxygenated myocardium produces FHR = 110-160 beats/min with no variability:
AA
B
Aortic arch chemoreceptor (AAC) not triggered by hypoxemia.
Aortic arch baroreceptor (AAB) not triggered by hypertension.
Aortic arch
Fig. 30.2 When the fetal cortex is “depressed” by hypoxia, analgesics, or general anesthesia, it no longer varies its sympathetic and parasympathetic input to the heart, and we see reduced or absent beat-to-beat variability. Ignorance of this fact caused the medical care team in this case to perform an unnecessary cesarean delivery for a preterm fetus. Abbreviations: AAB aortic arch baroreceptor, AAC aortic arch chemoreceptor, FHR fetal heart rate
The situation generating the FHR of 150 with no variability is shown in Fig. 30.2: an anesthetized fetal cortex no longer varies its sympathetic and vagal input to the heart, and the heart rate becomes fixed. It should be noted that—besides the varying input from an awake fetal cortex—the FHR is the result of both “non-reflex” and “reflex” influences: The main non-reflex influence on fetal heart rate is myocardial oxygenation. Hypoxic myocardium will decrease its rate of contraction, but the FHR of well-oxygenated myocardium can also decrease due to vagally-mediated reflexes initiated by baro- or chemo-receptors (or by head compression), and these decreases in FHR can occur despite adequate myocardial oxygenation. Hence, “non-reflex” fetal bradycardia is felt to be much more ominous than “reflex” bradycardia. In this case, both fetal cortex and myocardium were undoubtedly well- oxygenated, but the fetal heart rate variability had been abolished by anesthesia.
Lesson 11 When babies are born by cesarean delivery under GA, some observers do not clearly distinguish between the “depression” (or “floppiness”) due to general anesthesia and the depression due to the possible episode of fetal hypoxia which made the emergency CD necessary in the first place. Often the baby born under such circumstances is “floppy” and “depressed” due to the general anesthesia and not due to
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hypoxia, and what determines whether or not the baby will be “floppy” (have poor tone and respiratory effort) under these circumstances is the amount of anesthetic agent in the baby’s brain. Anesthesia and hypoxic depression can and should be distinguished by obtaining umbilical cord arterial blood gases (ABGs) after delivery under general anesthesia. ABGs will be normal (as in this case) when the depression is due to anesthesia and will show a severe metabolic acidosis in the case of depression due to a hypoxic episode. Such a distinction is obviously important from a human, medical, and medicolegal point of view, since the delivery of a “floppy” baby can be psychologically traumatic and provoke anxiety in the parents if they learn of the baby’s condition at birth. Box 30.2 presents the ABG values and clinical conditions which are thought to be compatible with an episode of intrauterine hypoxia sufficient to cause fetal brain damage [2]. In the absence of such values and conditions, the parents should feel reassured that their baby’s “floppy” condition at birth was just due to the anesthesia—and not due to hypoxia.
Box 30.2 Umbilical Artery Blood Gas Values and Other Findings Consistent with Fetal Hypoxia Sufficient to Cause Brain Damage 1. Fetal signs: • Fetal umbilical artery pH