Laser surgery in veterinary medicine 9781119485988, 1119485983, 9781119486022, 1119486025, 9781119486053, 111948605X

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Laser Surgery in Veterinary Medicine

Laser Surgery in Veterinary Medicine Edited by Christopher J. Winkler, DVM, DABLS, VMLSO Suffolk Veterinary Group Animal Wellness and Laser Surgery Center Selden, New York, USA

This edition first published 2019 © 2019 John Wiley & Sons, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. The right of Christopher J. Winkler to be identified as the author of this editorial material has been asserted in accordance with law. Registered Office John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA Editorial Office 111 River Street, Hoboken, NJ 07030, USA For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com. Wiley also publishes its books in a variety of electronic formats and by print‐on‐demand. Some content that appears in standard print versions of this book may not be available in other formats. Limit of Liability/Disclaimer of Warranty The contents of this work are intended to further general scientific research, understanding, and discussion only and are not intended and should not be relied upon as recommending or promoting scientific method, diagnosis, or treatment by physicians for any particular patient. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Library of Congress Cataloging‐in‐Publication data has been applied for ISBN: 9781119486015 Cover Design: Wiley Cover Images: Photo credit – Gaemia Tracy, Photo credit – Katalin Kovacs, Photo credit – Christopher J. Winkler 10 9 8 7 6 5 4 3 2 1

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Contents Dedication and Acknowledgments  viii About the Editor  ix Foreword   x Preface   xii List of Contributors  xv Disclaimer  xvii About the Companion Website  xviii Part I 

The Science of Laser Surgery  1

1 Laser Physics and Equipment  3 Peter Vitruk 2 Understanding and Utilizing Power Density  14 Noel Berger 3 Laser–Tissue Interaction: Selecting a Laser for Surgery  22 Christopher J. Winkler 4 The Ideal Laser Scalpel  32 Peter Vitruk 5 Combining Laser Surgery with Laser Therapy (Photobiomodulation)  42 David S. Bradley 6 Laser Safety in the Operating Theater  52 Christopher J. Winkler Part II 

Laser Surgery in Canines and Felines  61

7 Elective Laser Surgery Procedures  63 Paul Sessa and Andrew Brockfield 8 Oral Laser Surgery Procedures  84 Jan Bellows 9 Laser Surgery Procedures of the Nose and Throat  99 Ray A. Arza

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Contents

10 Laser Surgery Procedures of the Ear  106 Louis N. Gotthelf 11 Periorbital and Eyelid Laser Surgery Procedures  116 Daniel M. Core 12 Ophthalmic Lasers for the Treatment of Glaucoma  129 Noelle La Croix and Jay Wayne 13 Dermatologic Laser Surgery Procedures  141 David Duclos 14 Urogenital and Perianal Laser Surgery Procedures  164 William E. Schultz 15 Oncological Laser Surgery Procedures  198 Devin Cunningham and F. A. (Tony) Mann 16 Laser Photodynamic Therapy Procedures  206 Katalin Kovács 17 Surgical Lasers in Minimally Invasive and Endoscopic Small Animal Procedures  217 David S. Sobel 18 Laser Neurosurgical Procedures  239 Gaemia Tracy Part III 

Laser Surgery in Equines  245

19 Equine Laser Surgery Procedures  247 Lloyd P. Tate and Kathryn B. Tate Part IV 

Laser Surgery in Exotics Species  265

20 Laser Surgery Procedures in Small Exotic Animals (Small Mammals, Reptiles, and Avians)  267 Eva Hadzima, Maros Pazej, and Katherine Weston 21 Laser Surgery in Aquatic Animals (Sea Turtles)  292 Brooke M. Burkhalter and Terry M. Norton Part V 

Integrating Surgical Lasers in Your Veterinary Practice  313

22 Tips and Tricks for Veterinary Laser Surgeons  315 Les “Laser Les” Lattin 23 Pain Management in Laser Surgery Procedures  320 Noel Berger 24 Laser Surgery in the Mobile Practice  324 Janine S. Dismukes

Contents

25 Economic Considerations for Laser Surgery  327 John C. Godbold, Jr

Part VI  The Future of Lasers in Veterinary Medicine and Surgery  335 26 The Future of Lasers in Veterinary Medicine and Surgery  337 Christopher J. Winkler Appendix A: Glossary  341 Appendix B: Certifying and Academic Laser Organizations  346 Appendix C: Tables of Laser Settings  347 Index  359

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Dedication and Acknowledgments This book is dedicated in loving memory to those who still remain with us in our hearts, particularly to Donna and Robert Sessa, and to Jack Winkler. This book would not have been possible without the efforts of an extraordinary group of contributing veterinarians, experts, and their staffs, in the field of laser medicine and surgery. The past year has been a wonderfully illuminating education in each of your fields, and I am proud to bring your brilliant work to others’ attention. It has been the greatest of pleasures collaborating with you. A heartfelt thank you to you all. To John C. Godbold, Jr., DVM, whose mentorship, encouragement, patience, time, and input were invaluable and instrumental in the creation of this book. I am honored to call you my teacher, my colleague, and my friend. To Mr. Stephen Fisher, MBA, of the American Board of Laser Surgery, for his generous correspondence and aid with reference materials and figures.

To my editors, Erica Judisch, Purvi Patel, Susan Engelken, and Sandeep Kumar, for all of your advice and assistance. To my own staff past and present, for all of your help and enthusiasm for this project. To all of our patients who have helped us learn, and those that these efforts here are intended to help in the future, this is for you. To my family and friends for their support, especially to my parents Nancy and Joseph, whose own dedication and faith and love are an everlasting source of inspiration. To my children John and Kevin, my greatest endeavor, and to Nicole, my wife and companion in this our ­adventure. I love you very much.

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­About the Editor Christopher J. Winkler, DVM graduated from Ross University School of Veterinary Medicine in 2001, and worked on Long Island, NY, as an emergency room veterinarian and associate general practitioner before purchasing Suffolk Veterinary Group in 2006. Incorporating surgical lasers into his practice in 2010, he soon added laser therapy and began formal training a short time later, earning certifications in Veterinary Laser Medicine and Surgery from the American Board of Laser Surgery (ABLS) in 2015, and Veterinary Medical Laser Safety Officer from the American Institute of Medical Laser Applications (AIMLA) in 2016. Dr. Winkler has spoken on laser surgery and laser therapy and served as an associate laser surgery wet‐lab instructor for a number of national veterinary conferences including the NAVC, AVMA, and WVC. He has also conducted webinars on laser therapy for veterinary technicians and Ross University students, and published articles on laser surgery for Veterinary Practice News. He is a member of the American Society for Laser Medicine and Surgery (ASLMS), and is a faculty member of both the American Laser Medicine College and Board (ALMCB) and the American Laser Study Club (ALSC), for which he also sits on the editorial board of its journal. He receives referrals from veterinarians locally and nationally for laser surgery and laser therapy cases,

c­ ontinues to advise educating bodies on veterinary laser curricula, and offers his services as a laser consultant to veterinarians and equipment manufacturers.

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­Foreword My love affair with lasers and other light based medical technologies began in 1999 with a picture in a veterinary trade magazine. The picture, accompanying an article about a simple CO2 laser surgery procedure, was intriguing, a bit mysterious, and somehow very exciting. Our first date was a few weeks later when the representative for a surgical laser company brought a CO2 laser to my practice for a demonstration. After putting the laser in my hands for the first time, the representative talked me through several procedures. Seeing tissue vaporize was more intriguing, more mysterious, and exquisitely more exciting than the picture. I was in love, and my first CO2 surgical laser was delivered within a month. For early adopters of lasers, one of the challenges was an almost complete lack of information about the science of laser–tissue interaction and no information about its use in specific veterinary surgery procedures. Progress was made and new applications became more common because early adopters were willing to share their clinical experiences. We sought any potentially helpful publication, we networked to share case reports, and we celebrated when laser surgery texts were published in 2002 and 2006 (Bartels 2002; Berger and Eeg 2006). For me, sharing case reports led to making presentations about laser surgery, and leading wet labs and workshops in which my co‐faculty and I learned as much as participants. Eighteen years and over 600 educational events later, I continue to join participants in a quest for up‐to‐date information about surgical lasers and their use in veterinary medicine. Laser Surgery in Veterinary Medicine now gives us that information. Teaching wet labs and workshops has given me the opportunity to work with many talented colleagues ­serving as co‐faculty. One of the most notable is Dr. Christopher J. Winkler. Chris joined the teaching team for a CO2 laser wet lab I was leading several years ago and immediately excelled in teaching the technology one‐on‐one. Since then he has continued to be one of my first choices for co‐faculty. His depth of knowledge, understanding of the science, and ability to apply that science to clinical applications is

superb. He is one of only six veterinarians in the world certified by the American Board of Laser Surgery. No one is more qualified to be the editor and a contributing author of Laser Surgery in Veterinary Medicine. Dr. Winkler has gathered together an impressive group of scientists and veterinarians from academia, industry, specialty practices, and general practice as chapter contributors. Together with Dr. Winkler, the contributors give the veterinary community an authoritative source of information about laser surgery. The chapters on the science and safety of laser surgery are detailed and clearly presented. They include excellent illustrations and diagrams that help simplify the complexities of laser–tissue interaction. The chapters on clinical applications contain practical guidelines about species‐specific procedures, and help make this book a practical and usable clinical reference. The inclusion of many intraoperative pictures clarifies the contributing authors’ text descriptions. The chapters on integration give a road map for successful incorporation of laser surgery into a practice. And, the final chapter gives a glimpse into the future of laser surgery and what we can look forward to. A valuable feature of this book is the information about laser settings for procedures. Current surgical lasers have higher power, are more efficient, have improved software, and an increased number of delivery options. Since laser settings may vary depending on the specific equipment being used, tables for recommended settings use a standardized format applicable to multiple equipment options. Practitioners can adapt the recommendations to a wide range of equipment. Another valuable feature is that it is noncommercial. Just as with the tables of settings, the text describes treatment procedures and protocols in generic, noncommercially specific ways. Contributing authors do not recommend specific laser manufacturers. Rather, they describe a broad range of equipment and discuss the differences, benefits, and limitations between them. Laser Surgery in Veterinary Medicine will be the go‐to source of knowledge and reference for veterinary

­Forewor

s­ tudents, veterinary colleges, general practitioners, specialists, and those involved in the continued development of new laser devices for veterinary medicine. I look forward to it being a valuable addition to my library. And, I look forward to our quest for up‐to‐date information about surgical lasers and their use in veterinary medicine being over for a while.

­References Bartels KE. (2002). Lasers in medicine and surgery. Vet. Clin. North Am. Small Anim. Prac. 32(3). pp. 495–745.

Berger NA. Eeg PH. (2006). Veterinary Laser Surgery: A Practical Guide. Hoboken, NJ: Wiley‐Blackwell.

John C. Godbold, Jr. Stonehaven Veterinary Consulting Jackson, Tennessee, USA

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Preface Without any external influence, particles of light known as photons are spontaneously emitted by excited atoms and molecules as they return to lower levels of energy. This is the source of all light in nature. While formulating his Special Theory of Relativity in 1916, Albert Einstein described how photons might be emitted from atoms under external influence. He predicted what is now known as stimulated emission, where photons of a particular wavelength could stimulate atoms in an excited state to emit more photons of the same wavelength without absorption of the stimulating photons (Hecht and Teresi 1982b). Charles H. Townes, James P. Gordon, and H.J. Zeiger began working on a device in the 1950s that would amplify stimulated emission. Their invention of the microwave amplification by stimulated emission of radiation (MASER) would become the groundwork laid by Townes and Arthur Schawlow for the device known as the light amplification by stimulated emission of radiation (LASER), a term first coined by graduate student Gordon Gould, who also recognized that the temperature of laser light could exceed that of the operating temperature of its originating device (Hecht and Teresi 1982b). However, it was Theodore Maiman who built the first working laser in 1960 (Wyckoff 2014). Thinking outside the box with solid instead of gaseous mediums to create laser light, his solid ruby laser, pumped by a simple flashlamp, was a palm‐sized invention compared to Townes’ large design. Maiman predicted at a press conference highlighting his invention that such a concentrated light might be applied to medicine and surgery (Hecht 2005). Doctors did indeed begin experimenting with lasers in the 1960s to understand their possible use. Dermatologist Dr. Leon Goldman was a pioneer of laser surgery, trying one out on his own skin before offering it to his patients. A strong advocate of their use, he was the first to suggest that lasers not only can be used for surgical procedures, but are required for certain procedures such as those on the larynx, gastrointestinal (GI) tract, and brain (Hecht and Teresi 1982c).

In 1964 Dr. Kumar C. Patel invented the CO2 laser, a device of greater power with the subtle difference of operating in a vibrational rather than electronic transition of its active media, creating a wavelength of laser light much longer than those of other lasers. Though most of the interest in the CO2 laser at the time was in military and industrial applications, this wavelength would prove crucial to what would become one of the most prolific lasers to be used in human and veterinary surgery (LuxarCare 2004–2018). The first CO2 surgical lasers used articulated arms for delivery of light to the patient. Hollow waveguide delivery systems were also created in the 1960s alongside the burgeoning development of optical fibers for communication and image transmission (Harrington 2000). These two systems made the delivery of laser light to the patient more flexible and minimally invasive, and doctors and veterinarians began adapting them to their patients and procedures. One notable example was the Nd:YAG laser, delivered through optical fibers to facilitate minimally invasive surgery in equine species (Hecht and Teresi 1982a). From the 1970s to the 1980s, Dr. Kathy Laakmann‐ Crothall patented both the all‐metal radio frequency (RF)‐excited CO2 laser resonator (a lighter, more robust and heat‐efficient system than previous CO2 lasers) and the development of a flexible waveguide for CO2 surgical laser systems. This paved the way for laser surgical units to be utilized easily in general practice settings, and surgical lasers saw wider marketing to veterinary practices (LuxarCare 2004–2018). My own first encounter with surgical lasers occurred in the early winter of 2000. I was completing my small animal surgery rotation in my clinical year of veterinary school when I was assigned with two or three other students to a workshop conducted by one of our surgical interns to declaw a cat with a surgical laser. I remember it was winter because I was wearing a heavy pair of boots, which did not fit very well at all into the foot pedal of the laser’s trigger, and my foot got stuck on the trigger while I was trying to manipulate the laser. No one was hurt

Preface

(including the cat), but I do remember the intern examining his fingers as I left the room. My first experience with surgical lasers was thus not a fond one. I had the unfortunate impression they were merely a toy for declaws, and I had no particular desire to encounter them again as I proceeded with my training. Nearly 10 years later, my veterinary practice was riding the rapids of the Great Recession, and I was seeking ideas to make the practice distinctive. Fortuitously, a surgical laser representative stopped by and asked for a few minutes of my time. These few minutes showed me the surgical laser’s true potential, helping me to push past my previous encounter and decide to give it a try. I quickly became fascinated by the subject of laser medicine and surgery, and over the past eight years I have not conducted a surgery without a laser. I find it quite ironic that following my first encounter with lasers as a student, I’ve now had the opportunity to use a number of different laser models to conduct countless varied successful procedures, many of which I would not have attempted without a laser, and that I now cannot say enough about the benefits a surgical laser brings to both patient and surgeon. Seeing patient after patient leave my own clinic and those of my colleagues with such an improved recovery, sometimes almost as if nothing has happened, makes using lasers a very satisfying clinical experience. Clients are thrilled we offer this service and enjoy talking about it with others. No less rewarding are the new friends and colleagues with whom I’ve since met and worked, and the educational events I’ve learned and shared. I only wish I’d started using lasers sooner. In the past two decades, new advances have been made in laser technologies that are available now to veterinarians in specialty and general practice, as well as new techniques for working alongside the burgeoning field of veterinary laser photobiomodulation. Certifying bodies, such as the American Board of Laser Surgery and the American Institute of Medical Laser Applications, and academic laser societies such as the American Society for Laser Medicine and Surgery and the American Laser Study Club, have been established and continue to grow. The number of veterinarians utilizing laser surgery has dramatically increased, creating an opportunity for a remarkable collaboration between this small but growing body of knowledge and experience, which the reader will see manifest here. Laser Surgery in Veterinary Medicine details a wide variety of laser surgical equipment, and includes the tutelage, work experience and recommendations of a number of experienced and talented contributors from a diversity of venues of laser medicine and surgery. Topics addressed include laser physics, tissue‐interaction, safety, photobiomodulation, photodynamic therapy, small and large animal practice, specialty practice,

mobile practice, exotic animal practice, and practice integration. Chapters on canines and felines are further divided by surgical subject. Some of the most commonly asked questions I receive when discussing lasers with veterinarians about their concerns are recommendations for specific laser settings and techniques for a given procedure. Today’s lasers have seen improvements in power, efficiency, ergonomics, software, and options for spot size and power density which all affect the answer to these questions. To accommodate such concerns of practitioners, tables for recommended laser settings for each procedure have been designed within this text in a standardized format which reflects current technology and practices, following which each procedure is described in further detail. The tables of laser settings have also been compiled into an appendix for quick reference in a surgical setting. In researching and collaborating with so many experts, we have endeavored together to refrain from recommending specific laser manufacturers, preferring instead to describe a broad range of equipment which should serve the practitioner well, while discussing the differences, benefits, and limitations between them. In like fashion, rather than describing settings in a manner particular to a single piece of equipment, the previously mentioned tables of laser settings discuss their particulars in the broadest possible terms to allow the practitioner to adapt them to the wide range of surgical lasers available today. In this endeavor my coauthors and I have strived to provide as much information as possible while avoiding confusion for the reader, who may still find it worthwhile to consult their laser’s manufacturer for further discussion of the adaptation of these tables to their own laser surgical unit. The recommended laser settings within come from the experience behind performing countless procedures over many years. They remain recommendations, and we look forward to our readers sharing their own methods, refinements, and experiences with us and others. The understanding of basic subjects such as laser physics, biophysics, laser–tissue interaction, and laser safety are becoming a necessary and valuable foundation for students and practitioners as the use of lasers becomes more ubiquitous in veterinary practice. This book is therefore intended as a source of knowledge and reference for the veterinary student, veterinary colleges, general practitioners and specialists alike, and experts in laser industry for the further development of equipment and applications. As a state‐of‐the‐art method of performing surgery, we believe laser surgery should indeed be introduced with great enthusiasm to veterinary students at the university level, and my colleagues and I hope to assist here in making such an introduction an interesting and informative one.

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Preface

­References Harrington J. (2000). A review of IR transmitting, hollow waveguides. Fiber Integr. Opt. 19. pp. 211–217. Hecht J. (2005). Beam: The Race to Make the Laser, Chapters 15 and 16. New York, NY: Oxford University Press. pp. 169–194. Hecht J, Teresi D. (1982a. A laser bestiary: different kinds of lasers. In: Laser: Light of a Million Uses, Chapter 3. Toronto, ON: General Publishing Company, Ltd. pp. 36–38. Hecht J, Teresi D. (1982b. The short but tempestuous history of the laser. In: Laser: Light of a Million Uses, Chapter 4. Toronto, ON: General Publishing Company, Ltd. pp. 49–61. Hecht J, Teresi D. (1982c. Laser medicine: a bright promise. Laser: Light of a Million Uses, Chapter 5. Toronto, ON. General Publishing Company, Ltd. 62–80.

LuxarCare. (2004–2018). Brief history of the surgical CO2 laser. http://www.luxarcare.com/main. php?group=resources&page=laser_history (accessed 7 August 2018). Wyckoff EB. (2014). The laser light mystery. The Man Who Invented the Laser: The Genius of Theodore H. Maiman, Chapter 4. Berkeley Heights, NJ: Enslow Publishers, Inc. pp. 23–31.

Christopher J. Winkler Suffolk Veterinary Group Animal Wellness and Laser Surgery Center Selden, NY, USA 2018

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List of Contributors Ray A. Arza, DVM

John C. Godbold, Jr., DVM

RSA Veterinary Technologies Taylorsville, KY, USA

Veterinary Laser Consultant Stonehaven Veterinary Consulting Jackson, TN, USA

Jan Bellows, DVM, Diplomate AVDC, ABVP (canine and feline)

All Pets Dental Weston, FL, USA Noel Berger, DVM, MS, DABLS

Quail Hollow Animal Hospital Wesley Chapel, FL, USA David S. Bradley, DVM, FASLMS

Veterinary Medical Director K‐Laser Oakdale, CA, USA Andrew Brockfield, BSc.

Salida Veterinary Hospital Salida, CA, USA Brooke M. Burkhalter, DVM

Sea Turtle Hospital at UF Whitney Lab St. Augustine, FL, USA; Turtle Hospital Marathon, FL, USA Daniel M. Core, DVM

Airline Animal Health and Surgery Center Bossier City, LA, USA Devin Cunningham, DVM

University of Missouri College of Veterinary Medicine Columbia, MO, USA Janine S. Dismukes, DVM

Mobile Laser Veterinary Services Garner, NC, USA David Duclos, DVM, Diplomate ACVD

Animal Skin & Allergy Clinic Lynnwood, WA, USA

Louis N. Gotthelf, DVM

Animal Hospital of Montgomery, LLC Montgomery Pet Skin and Ear Clinic Montgomery, AL, USA Eva Hadzima, DVM, MVDr

Dewinton Pet Hospital Heritage Pointe, AB, Canada Katalin Kovács, DVM, PhD

Small Animal Laser Clinic Budapest, Istvánmezei út 6. Hungary Noelle La Croix, DVM, Diplomate ACVO

Veterinary Medical Center of Long Island West Islip, NY, USA Les “Laser Les” Lattin

Senior Laser Consultant LuxarCare/Aesculight Surgical Lasers Gaithersburg, MD, USA F. A. (Tony) Mann, DVM, MS, Diplomate ACVS, Diplomate ACVECC

Professor Small Animal Soft Tissue Surgeon Director of Small Animal Emergency and Critical Care Services University of Missouri College of Veterinary Medicine Columbia, MO, USA Terry M. Norton, DVM, Diplomate ACZM

Georgia Sea Turtle Center Jekyll Island, GA, USA; Turtle Hospital Marathon, FL, USA

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List of Contributors

Maros Pazej, DVM, MVDr

Gaemia Tracy, DVM

Dewinton Pet Hospital Heritage Pointe, AB, Canada

Northstar VETS Veterinary Emergency Trauma and Specialty Center Robbinsville, NY, USA

William E. Schultz, DVM

Schultz Veterinary Clinic Okemos, MI, USA Paul Sessa, DVM

Salida Veterinary Hospital Salida, CA, USA David S. Sobel, DVM, MRCVS

Metropolitan Veterinary Consultants Hanover, NH, USA; Elands Veterinary Clinic Dunton Green, Kent, UK Kathryn B. Tate, DVM

Southern Pines, NC, USA Lloyd P. Tate, Jr., VMD, Diplomate ACVS, DABLS

Professor emeritus NCSU‐CVM Southern Pines, NC, USA

Peter Vitruk, PhD, DABLS

Special Advisor on Physics and Safety Education American Board of Laser Surgery Aesculight, LLC Bothell, WA, USA Jay Wayne, PhD

Department of Biology Suffolk County Community College Selden, NY, USA Katherine Weston, BSc

Dewinton Pet Hospital Heritage Pointe, AB, Canada Christopher J. Winkler, DVM, DABLS, VMLSO

Suffolk Veterinary Group Animal Wellness and Laser Surgery Center Selden, NY, USA

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­Disclaimer Please read the statements and the surgical and therapeutic protocols within this text carefully before utilizing any of this information. The information and recommendations are based on previously published scientific information and years of practice, clinical, and research experience by the contributing authors. Knowledge about laser surgery and photobiomodulation is constantly changing through ongoing research, clinical trials, and day‐to‐day clinical experience. The information within this text is presented for educational purposes only and is designed to be a reference to complement formal training about laser surgery and laser therapy. This text contains neither complete nor comprehensive information about any of the conditions addressed,

and each condition should be evaluated on an individual basis in each patient prior to surgery. This text is not a substitute for professional advice, care, diagnosis, or treatment. It is the sole responsibility of the veterinarian, veterinary surgeon, veterinary technician, veterinary assistant, and veterinary therapist to gain the knowledge and comply with all federal, national, provincial, state, and local laws regarding the use of therapeutic and surgical lasers for any condition. Dr. Christopher J. Winkler, all of the contributing authors of this text, and anyone involved with the publication of this text expressly disclaim any and all responsibility and legal liability for any kind of loss or risk, personal or otherwise, which is the result of the direct or indirect use or application of any of the material within this text.

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­About the Companion Website This book is accompanied by a companion website:

www.wiley.com/go/winkler/laser The website includes: Thirty six videos to accompany Chapters 7, 10, 14, 20, and 21.

1

Part I The Science of Laser Surgery

3

1 Laser Physics and Equipment Peter Vitruk

­Introduction This chapter covers the principles of laser physics to the extent and depth required to understand basic structure and function of a veterinary surgical laser and the process of generating laser light, followed by a discussion on equipment focusing on the practical aspects of CO2 lasers (the most commonly used surgical laser in veterinary surgery) while briefly reviewing other types of more specialized surgical lasers.

­Creating Laser Light Photons and Waves According to the photon theory of light, light is made of particles called photons. A photon travels at the speed of light c; it carries a specific electromagnetic energy (E = hf, where h is Planck’s constant and f is the photon’s frequency); and it has a momentum, or spin, that defines its polarization. The photon theory of light took its origin from the efforts of Max Planck to properly explain the spectrum of blackbody radiation; it remains an important part of Quantum Mechanics, which explains the properties of light and matter on the microscopic scale. According to the wave theory of light, light travels in a wave at the speed of light c, just as in photon theory. Such a wave is made of both electric and magnetic waves oscillating at frequency f (also just as in photon theory). The orientation of the electrical field defines the wave’s polarization. The wave theory of light is an important concept in many branches of physics from optics to electromagnetism. Quantum electrodynamics (QED) is the theory that combines both photon and wave ­theories of light together.

When considering the principles of lasers and processes involved in generating laser light, it is useful to think of light in terms of photons, emitted or absorbed when atoms or molecules of the active medium inside the laser change their atomic or molecular energy states. For instance, if an electron of an atom having its two energy states separated by hf, is impacted by a photon of energy hf, and the photon is absorbed by the atom, the electron will undergo an energy change from a lower state to a higher state (Figure 1.1a). At the same time, when considering the optical properties of the laser apparatus known as the optical resonator, it is most helpful to think of light in terms of waves. For instance, consider the shape of the resonator mirror that matches the shape of the laser beam’s wave front reflected from the mirror surface (Figure  1.2). Such a light wave with an extended curved wavefront is the result of a superimposition of many individual synchronized photons of the same frequency. Absorption, Spontaneous Emission, and Stimulated Emission An atom or molecule that has absorbed a photon and entered a higher energy state (Figure 1.1a), will undergo an energy transition to a lower energy state while emitting a photon with energy equal to the difference between the two states (Figure 1.1b). This is known as spontaneous emission, the source of natural light. In addition to light absorption and spontaneous emission, a third way light interacts with matter is also possible, and was first described by Albert Einstein (Siegman 1986; Verdeyen 1989; Saleh and Teich 1991; Endo and Walter 2007). If the energy of a photon matches the difference between the two states, and the electron is in the higher of the two states, then the incoming photon will trigger the electron to jump to a lower energy state while

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

Laser Physics and Equipment

– hf

c

hf

–

Absorption of light

+

+

Wave fronts of light waves resonating between the mirrors

(b) – – Spontaneous emission of light

+

hf hf

+

(c) –

hf

hf

hf

Photon

– Stimulated emission of light

+

hf

Curved total reflector mirror

(a) Curved total reflector mirror

4

+ Nucleus

hf

+

– Electron

Atomic energy levels

Figure 1.1  Absorption (a), spontaneous emission (b), and stimulated emission (c) of light by an atom.

an identical photon will be emitted in the same direction as the original incoming photon (Figure 1.1c). Such emission of light is referred to as stimulated emission. Active Medium and Excitation (Pumping) Mechanism A working laser requires two critical components: an active medium (a medium of atoms or molecules in high energy states, such as carbon dioxide gas in a CO2 laser) and an optical resonator. The high‐energy states of an active medium can be created through a variety of mechanisms, such as energizing atoms or molecules optically (optical pumping), or electrically. Figure 1.3 illustrates an active medium placed between two mirrors that form an optical resonator. Optical Resonator An optical resonator typically consists of two mirrors, one a total reflector (often concave), and the other partially reflective and partially transmissive. The transmissivity of the partial reflector represents the resonator loss

Figure 1.2  Laser resonator mode having its wavefront matching the shape of the resonator mirrors.

of laser light, and for many practical lasers, the loss is designed to match the amplification of light as it takes a round trip through the active medium (Figure 1.3). The length of the resonator apparatus is inversely proportional to how strong the amplification (or gain) is for any particular type of laser. Weak gain lasers, such as surgical CO2 gas lasers or ophthalmic excimer gas lasers, require an active medium of relatively long length. Strong gain lasers, such as solid‐state erbium or semiconductor diode lasers, have relatively short‐length active media. For the simplest types of laser resonators, the strongest resonator mode has a bell‐shaped intensity spatial distribution profile (also known as a Gaussian profile, discussed in depth in Chapter 2). As the beam propagates away from the laser, it diverges and its diameter increases (Figure 1.3). Such diverging laser beams can be easily collimated and then focused by appropriate lenses (Figure 1.4) to be utilized for medical and surgical purposes. Inverse Population and Light Amplification A medium will first need to have an inverse population, a sufficient quantity of atoms or molecules in higher energy states, for stimulated emission to occur. Stimulated emission within an optical resonator in turn results in light amplification, where a single photon among atoms or molecules in high‐energy states can result in an avalanche of many identical photons of the same wavelength traveling parallel and synchronous to each other through the medium (Figure 1.2). When these conditions are met in an apparatus, laser light is produced. The word LASER is thus an acronym for light amplification by stimulated emission of radiation. A highly important concept of a functioning laser is a sustained pumping mechanism that is key to a powerful laser oscillation, especially for surgical, therapeutical, and industrial applications. Such sustained laser ­pumping may be illustrated by how a CO2 laser pumping mechanism is optimized through (i) selecting the ­composition of gases in the active medium and their respective partial gas pressure; (ii) selecting the diameter

­Creating Laser Ligh Mirror (total reflector, gold plated metallic surface)

Active medium

Laser beam

(e.g. gas discharge plasma in a gas mixture of He, N2, CO2, and Xe)

Laser beam diverges as it propagates, its intensity decreases

Mirror (partial reflector, AR coated ZnSe crystal)

Lowest order gaussian laser beam intensity profile spatial distribution

Figure 1.3  Laser resonator and an active medium producing a monochromatic, coherent, collimated laser beam exiting through the partially reflective resonator mirror. The lowest‐order resonator mode is bell‐shaped (Gaussian beam intensity profile). As it propagates away from the resonator, the laser beam diverges.

Light bulb

Lens collects only a fraction of the light from the light bulb

Lens

Ordinary light is not focusable Lens collects entire output of laser

Laser light is focusable

Laser

Figure 1.4  Unlike the ordinary light, laser light can be efficiently focused into a very small spot.

of the active medium; and (iii) selecting electrical parameters of the plasma that is maintained inside the active gas medium (Endo and Walter 2007). One of the most important gases in the active medium of a CO2 laser is nitrogen (N2) that stores up to 80% of the energy, pumped into the plasma, in its first vibrational excited state. CO2 molecules colliding with such excited N2 molecules undergo energy transition into upper lasing energy levels. In order to maintain the lowest population on the lower lasing energy level of the CO2 molecule, helium (He) gas is added to the mixture for the most efficient cooling of the active medium. Finally, xenon (Xe) gas is

added to the gas mixture to optimize the energy of electrons in the plasma so that the most efficient excitation of N2 molecules can take place. Now having achieved proper gas composition, the diameter of the active medium is also optimized per total gas pressure for maximum electro‐optical efficiency, which can exceed 20%. Finally, the electric current through the active medium plasma is optimized for the desired combination of output laser power and laser efficiency. Properties of Laser Light: Monochromaticity, Coherence, Collimation Laser light emanating from the laser’s partial reflector (Figure  1.3) is monochromatic (of a single wavelength), coherent (the photons of the beam oscillate in sync with each other), and typically collimated (the photons travel parallel to each other, if the partial reflector is designed as a flat surface mirror). The most important practical feature of the laser beam for surgery is its ability to be focused to a very tight focal spot (Figure 1.4) so that beam power and energy densities are maximized. Monochromaticity is also extremely important, as the laser beam wavelength is uniquely related to its interaction with the target tissue’s optical properties such as absorption, scattering, and reflection from the target’s surface (discussed further in Chapter 3). Determined by the type of active medium within the optical resonator, it is the laser’s wavelength that best determines the purpose for which the laser light will be used.

5

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Laser Physics and Equipment

Another often overlooked property of laser light is its power. None of the alternative light‐generating technologies are capable of producing the same efficacy of a laser if a specific spectral wavelength is required. Monochromaticity, collimation, and the sheer amount of energy of a laser beam make laser surgery practical. Indeed, as will be demonstrated subsequently, high‐ speed soft tissue laser incisions with erbium and CO2 lasers can only happen at fluencies in excess of hundreds of joules per square centimeter. This translates to a practical laser device in the desired optical spectrum range with strong absorption by histological water of soft tissues with laser beam power in the range of 30–60 W.

­Practical Surgical Lasers Being the most commonly used surgical laser in veterinary surgery, we will examine the CO2 laser for demonstrating practical aspects of equipment for generating laser light and delivering it to the patient (Figure 1.5). Laser Tube Technology CO2 laser resonator chambers of the 1960s were made of glass tubes. They proved quite fragile not only for their material make‐up but also because they could not

4

8

6 7,9,10

7 5 1 3

2

Figure 1.5  Basic building blocks of a surgical CO2 laser: (1) metal CO2 laser tube resonator; (2) low‐voltage 32 V DC and RF power supplies; (3) heat exchanger; (4) beam delivery system; (5) laser power meter; (6) beam attenuator (shutter); (7) devices monitoring the performance of the above critical components; (8) user control panel; (9) software program controlling the above hardware items; and (10) safety “watch‐dog” software program monitoring the above items. Source: Image courtesy of Aesculight–LightScalpel LLC, Bothell, WA.

­perate without a flowing liquid coolant needed to o ­prevent the glass from cracking under the intense heat generated by electrical plasma discharges within the laser tube. Voltages exceeding 10 000 V are required to create and sustain plasma in such glass tubes, creating a significant electrical hazard concern. They were also not serviceable in the event of eroded electrodes and metal‐ sputtered glass tube walls, often necessitating laser tube replacement in the event of failure. Their other limitations, such as laser pulse width, laser power stability, and laser beam quality, have led to their replacement in the mid‐1990s by all‐metal laser resonator chambers in nearly all industrial and most medical applications (Figure 1.6). Rugged and reliable in power ranges from 10 to 1000 W, all‐metal radio‐frequency (RF) excited CO2 laser tubes also allow for fast and relatively inexpensive service. The all‐metal tube is also easily cooled with forced air, which allows for a smaller, inexpensive, ­reliable and light‐weight integration of heat dissipation into the practical surgical laser system. The CO2 laser is only 10–20% efficient; hence 80–90% of electrical energy is transformed directly into heat inside the laser tube and system. This waste heat needs to be removed or the laser will overheat and its power will deteriorate during operation. Older CO2 lasers constructed without heat exchangers could not be operated for extended periods of time without overheating and subsequent laser power deterioration during surgeries (this is difficult to track if such lasers also lack on‐board laser power meters for accurate laser beam power monitoring). Lasers featured in Figure  1.7 include efficient heat exchangers in their design: air‐cooled (and light weight) or cooled by flowing water (and correspondingly heavier, with minor concern for affecting electronics during maintenance). Some laser manufacturers may claim that their laser beam power can be “internally calibrated.” This is technically impossible if their lasers lack a laser power meter with which to measure laser power. US Food and Drug Administration (FDA) regulations require the presence of a laser power meter in US medical lasers (FDA CDRH Title 21 Part 1040.11 defines “medical laser” as such used on humans). Those lasers lacking them are not considered medical devices as the absence of laser power control and monitoring may negatively impact outcomes of laser treatments, laser power being one of the critical parameters for quality of incisions and hemostasis. FDA regulations (CFR Title 21 Part 1040) also require another very important safety device: the beam attenuator, or shutter, as a part of the laser intended for either veterinary or medical use. It is recommended that ­practitioners seeking to purchase a surgical laser make

­Practical Surgical Laser

(a)

(b)

All-metal tube CO2 laser

Glass tube CO2 laser

Figure 1.6  All‐metal (a) and glass (b) CO2 laser tube designs. Source: Images courtesy of Aesculight–LightScalpel LLC, Bothell, WA.

certain that the device is compliant with these and other local and national regulations and standards for construction and operation of a medical device. Beam Delivery Technology Laser light and its energy needs to be delivered efficiently from laser resonator to target tissue, and this is not a trivial task. Historically, the first medical delivery systems developed in the 1960s were based on a sequence of seven mirrors (approximating the design and flexibility of the human arm) that guided the laser beam to a desired location, culminating in passing the beam through a focusing lens in order to maximize laser beam fluence on the target. Such articulated arm delivery systems (Figures 1.7 and 1.8) saw wide use in the 1970s–1980s. The advantages of the articulated arm are mainly applications where alternative fiber technology cannot handle high‐ peak laser power. It is also highly efficient in its transmission of energy from resonator to patient. The alignment and integrity of all seven mirrors is critical, however, and can only be verified and calibrated at the factory or by trained field service engineers; an articulated arm of questionable alignment should be taken out of service for maintenance. The system is also quite heavy and can be taxing during a lengthy procedure. Solid core fibers (e.g. quartz) were developed and adapted from communication applications for medical use. Such fibers guide laser light through them by utilizing a total internal reflection phenomenon. The advantage of solid core fiber technology is application in flexible endoscopy. A severe limitation of such technology is that current solid core fiber materials cannot

transmit wavelengths greater than 3000 nm. Solid core fibers are thus not applicable as a delivery system for CO2 lasers and even for 2940 nm erbium lasers, and advantages they provide to endoscopic applications only extend to those near‐infrared spectral laser wavelength ranges that are not ideal for efficient incision. Many veterinary applications still continue to see effective use of solid core fiber delivery technology, however, and will be examined later in this text. A highly important aspect of utilizing solid core fibers is proper “cleaving” of its distal end, without which the fiber’s tip can fracture during surgery (due to thermally‐induced mechanical stresses) and harm the patient. Flexible hollow waveguide fibers (Figures 1.5, 1.7, and 1.8) became the dominant delivery technology for surgical CO2 lasers since the mid‐1990s. Such technology is very similar to solid core fiber technology in a sense that both rely on (i) minimizing optical losses of the core (glass in the case of solid core fibers, air in the case of hollow core waveguide fibers) and (ii) maximizing reflection of laser light from the internal walls of the fiber. Hollow core fibers utilize highly polished, highly reflective metal surfaces, which are additionally coated with a laser‐wavelength‐specific dielectric layer of specific thickness. Rugged and long‐lasting, modern‐day hollow waveguide fibers are capable of transmitting hundreds of watts of CO2 laser power with beam quality that rivals solid core surgical lasers (e.g. 2780 nm erbium lasers). The advantages of hollow core waveguide fiber technology over articulated arms are significantly lighter weight and flexibility, with development for endoscopic use (albeit limited to rigid endoscopes; flexible endoscope usages are currently limited to hospital OR applications and continue to be prohibitively expensive for veterinary use).

7

Laser Physics and Equipment

CO2 laser with allmetal tube resonator and flexible hollow waveguide fiber beam delivery

Flexible hollow waveguide fiber

Flowing water cooled glass laser tube

8

Sterilizable handpiece

CO2 laser with glass tube resonator and articulated arm beam delivery

Articulated arm

Handpiece

All metal laser tube

Low voltage 32 V DC power supply

High voltage 20 000 V DC power supply

Water tank Forced air cooling

Water pump

Water cooler

Figure 1.7  Side‐by‐side comparison of air‐cooled, all‐metal tube, flexible‐waveguide CO2 laser (left) and a liquid‐cooled, glass‐tube, articulated arm CO2 laser (right). Source: Image courtesy of Aesculight–LightScalpel LLC, Bothell, WA.

The flexible fiber can also be calibrated at any time by the user. Care should be taken with both solid and ­hollow core fibers as any kink or break in the fiber will destroy its transmissive properties and necessitate replacement.

Hollow waveguide fibers enable use of compact and ergonomic handpieces (Figure 1.9) with scalpel‐like feel, featuring pinpoint accuracy as well as enhanced ergonomics, flexibility, and accessibility for surgeons. These laser handpieces are designed for a laser beam’s focal

­Practical Surgical Laser

(a)

(b) Seven-mirror articulated arm beam delivery. Handpiece features a single focal spot size. Long focus lens in the handpiece, along with the long optical path through sevenmirror optical train, require an aiming beam to track the focal spot of the invisible CO2 laser beam

Flexible fiber beam delivery. Autoclavable handpiece features three different focal spot sizes. No aiming beam is needed due to short focus lens and short optical path optical train inside the handpiece

Figure 1.8  Articulated arm (a) and flexible hollow waveguide fiber (b) CO2 laser beam delivery systems. Source: Images courtesy of Aesculight–LightScalpel LLC, Bothell, WA.

spot centered at 2 mm from the distal end of the hand piece tip (or nozzle). Spot sizes (discussed in Chapter 2) may be facilitated either by fixed tips selected by the ­surgeon prior to the procedure, or selected during the procedure on a specially designed adjustable hand piece. Laser handpieces should be designed for ease of cleaning and sterilization and must withstand thousands of ­cleaning and autoclave sterilization cycles. Lenses should be cleaned following procedures as per manufacturer recommendations. A highly important practical aspect of any CO2 laser delivery system is a continuous purge of air (or ­nitrogen or helium, etc.) during surgery. The purge’s purpose is twofold: (i) prevent the surgical laser plume from back‐streaming into the fiber and (ii) prevent the surgical laser plume from obstructing the view of the surgical site. Laser Power Control Exposures: Continuous Wave, Single Pulse, and Repeat Pulse The pattern of time variation of output power from a laser apparatus is known as a temporal mode, or exposure, and can be controlled by the user through simple programming of the laser console and use of the trigger (usually a footswitch). Exposures are usually available in three preprogrammed forms: continuous wave, repeat

pulse, or single pulse. Pulse frequency is conventionally defined as a number of pulses per second, and its unit of measure is hertz (Hz). The percentage of time that the laser power is ON is conventionally defined as duty cycle, displayed as a percentage (%). The duty cycle determines the average power, which defines the depth of laser incision (further discussed in Chapter 4). The continuous wave exposure is turned ON and OFF by the footswitch, and the lasing duration lasts as long as the footswitch is depressed (Figure 1.10a,b). Long pulse and continuous wave CO2 lasers are less‐efficient cutters but provide for greater depth of coagulation for excising and incising highly vascular and inflamed tissues such as hemangioma. The single pulse exposure (Figure  1.10c,d) is turned ON and OFF electronically with the lasing duration predetermined by the preset pulse duration of 5–500 ms at the control panel. A single timed exposure is delivered for each depression of the footswitch. In repeat pulse exposure, the laser beam cycles between ON and OFF while the footswitch is depressed. Repeat pulse exposure (Figure  1.10e,f ) is turned ON and OFF by the footswitch, while the RF driver is modulated during “footswitch ON” in a predetermined fashion at the control panel by the preset pulse duration (5–200 ms) and preset frequency (e.g. in 1–50 Hz range).

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Laser Physics and Equipment

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(a)

(h) (i)

ON

Power (W)

Power (W)

0

(c)

Power (W)

0

Laser Power Control Modes: SuperPulse vs. Non‐SuperPulse Another programmable method of laser light delivery is the SuperPulse mode, characterized by extremely short pulses of high‐peak power, in which pulse durations are shorter than a target soft tissue’s thermal relaxation time of approximately 1.5 ms, while the spacing between pulses is greater than the tissue’s thermal relaxation time. Such intense pulses of high power exceed the power of a continuous wave exposure and help to facilitate efficient ablation, while the interval between pulses minimize collateral thermal trauma. SuperPulse may be available in different forms of exposure and can be achieved at variable frequencies of 50–400 Hz, with peak laser power being up to 50 times greater than the average power indicated on the control panel. The non‐SuperPulse mode is simply characterized by a steady laser output from the laser tube as described in the previous discussion of

3

1

2

3

Time (s)

Time (s)

Non-SuperPulse mode LASING 0.1

(d)

(e)

2

SuperPulse mode LASING

“SINGLE PULSE” control signal @ 100 ms Power (W)

Figure 1.9  Autoclavable laser handpieces available for flexible hollow waveguide fiber CO2 lasers. Handpieces are designed to work as a distal attachment on a flexible hollow waveguide fiber (these handpieces do not use disposable tips): (a) handpiece with a handle and a back‐stop for laser beam, for use in soft palate resection; (b) handpiece with adjustable focal spot size diameters of 0.25, 0.4, and 0.8 mm; (c) contra‐angle dental handpiece with 0.25 mm spot size; four straight handpieces with fixed spot sizes of 0.25 mm (d), 0.4 mm (e), 0.8 mm (f ), and 1.4 mm (g); straight handpiece with fixed 3 mm by 0.4 mm wide ablation rectangular spot (h); and a smoke evacuating attachment to work with any handpiece (i). Source: Image courtesy of Aesculight–LightScalpel LLC, Bothell, WA.

Non-SuperPulse mode LASING 1

(b)

OFF

Footswitch controlled “CONTINUOUS” mode

Time (s)

SuperPulse mode LASING

0.05

0.1

0.15

Time (s)

“REPEAT PULSE” control signal @ 20 Hz and 50% duty cycle Power (W)

Non-SuperPulse mode LASING 0.05

(f) Power (W)

0

0.1

0.15

Time (s)

SuperPulse mode LASING

0.05

0.1

0.15

Time (s)

Figure 1.10  A CO2 laser’s gated exposures: continuous (a, b), single pulse (c, d), and repeat pulse (e, f ).

exposures. Discussions of SuperPulse will continue in Chapters 2 and 4. Nd:YAG, Ho:YAG, Er:YAG, and Er:YSGG Lasers Although the principles of the creation of laser light remain the same as in CO2 lasers, other lasers use different active media to create lasers of differing wavelengths, which may have different applications in soft tissue surgery. Cylindrical rods of yttrium aluminum garnet (YAG), with additions (known as dopants) of neodymium (Nd), holmium (Ho), or erbium (Er) are used as active mediums in Nd:YAG, Ho:YAG, and Er:YAG solid‐state lasers. An yttrium scandium gallium garnet (YSGG) rod, with an erbium dopant, is used in the Er:YSGG solid‐state laser. Clinical applications for the Nd:YAG (1064 nm) laser are based on the wavelength’s low absorption in water and a relatively higher absorption in hemoglobin and oxyhemoglobin. It cannot produce photothermal ­ablation

­Practical Surgical Laser

due to extremely high ablation thresholds and is t­ herefore utilized as a hot glass tip cautery device rather than an optical laser in soft tissue cutting applications (further examined in Chapter 4). However, its ease of transmission through inexpensive commercial optical fibers, coupled with a wavelength excellent for achieving coagulation and hemostasis over large volumes of soft tissue, makes it ideal for minimally invasive procedures and those involving neoplasia and other difficult‐to‐reach lesions, particularly in equines (Chapter 19). A frequency‐doubled Nd:YAG laser is known as a KTP (potassium‐titanyl‐phosphate) laser, with a wavelength of 532 nm. A frequency‐tripled Nd:YAG laser operates at 355 nm, the range where excimer pulsed‐gas lasers operate. Both 532 and 355 nm Nd:YAG lasers have great applications in human dermatology, but their applications in veterinary surgery are limited. Nd:YAG lasers can achieve short pulse durations at high peak energy, known as Q‐switching. The Ho:YAG (2100 nm) laser is also easily transmitted through optical fibers and can operate in a liquid environment. Its absorption in water is much stronger than for Nd:YAG lasers, and it is a far more efficient photothermal laser than its Nd:YAG cousin. Water absorption at 2100 nm is still much weaker relative to the CO2 laser wavelength, which is why the Ho:YAG laser is not as efficient a cutter while producing more collateral thermal damage. Its absorption in water and its delivery through optical fibers of small diameter make it ideally suited for lithotripsy (Chapter  17) and neurological applications such as IVDD treatment and prevention (Chapter 18). Both Er:YAG (2940 nm) and Er:YSGG (2780 nm) wavelengths are close to the water absorption peak near 3000 nm, which makes them excellent choices for cutting bone and enamel with relatively low water concentrations. Water absorption at 2940 nm is approximately 3 times stronger than for 2780 nm, and approximately 15 times stronger than for the 10 600 nm CO2 laser wavelength. Both Er:YAG and Er:YSGG wavelengths are thus also good for cutting soft tissue, but remain poor coagulators (further discussed in Chapter 4). Near‐infrared Diode Lasers and Hot Fiber Tips As further explained in Chapter  4, diode near‐IR laser wavelengths are weakly absorbed by soft tissue (Fisher 1987, 1993; Willems et al. 2001; Vogel and Venugopalan 2003; Vitruk 2014; Vitruk et al. 2014). Instead, the tissue is cut thermomechanically on contact with a charred glass “hot tip” (Figure 1.11), with the temperature profile inside the tissue approximated as T = 37 + 63(1 − 1.5 (x/δ)  + 0.5(x/δ)3) and illustrated in Figure  1.12, where δ  =  (8Kt)½ is the heat propagation distance,

Near IR absorber (char)

B

Heat diffusion from hot tip

Hot glass tip

HT >> B Hot tip coagulation depth

Figure 1.11  Hemostasis and coagulation through heat diffusion from the hot tip into the soft tissue. HT is heat propagation‐driven depth of coagulation, B is blood vessel diameter. Source: Image courtesy of LightScalpel LLC, Bothell, WA.

K ≈ 0.155 mm2/s is the soft tissue thermal diffusivity, and t is the “ON” time of the heat source at the surface of the tissue (Ozisik 1980; Willems et al. 2001; Rathmore and Kapuno 2011; Vitruk et al. 2014). The heat propagation‐driven coagulation depth HT = 0.45 (8 Kt)½ contains the 60–100°C tissue temperatures as indicated in Figure 1.12. For soft tissue cutting with such lasers, an optically dark carbonized material, or “char” (e.g. organic matter, burnt ink, or burnt corkwood), is first deposited on the very end of the fiber tip (Romanos et al. 2015). The diode laser beam is absorbed by the char, which heats the tip of the fiber from 900 to 1500 °C (Romanos 2013; Romanos et al. 2015). As a result, soft tissues are heated up through heat conduction and diffusion from the hot fiber tip to and through the soft tissue. The hot tip thus acts as a nonlaser, thermal ablation device with the approximate temperature profile in soft tissue shown in Figure 1.12. In other words, the diode laser does not cut tissue with photons but with a hot fiber (akin to electrocautery where soft tissue is cut by a heated metal tip). The cutting speed of a heated diode fiber is limited by its disintegration at elevated temperatures (up to 1500°C), thus raising concerns about biocompatibility of the burnt tip’s cladding chemicals and thermally fractured fiber (FDA 2005; ISO 2009; Vitruk 2012; Romanos 2013; Romanos et al. 2015). Sapphire tips are not only more rugged at high‐operating temperatures in excess of 1000°C but also more expensive (Fisher 1987, 1993). Figure 1.13 illustrates use of a hot fiber laser tip on gingival tissue. Figure 1.13 illustrates the coagulation depths calculated for constant tip temperature (red line) and constant tip power (blue line) conditions, that are also

11

Laser Physics and Equipment

Figure 1.12  Approximate temperature distribution in soft tissue; surface temperature is 100 °C, coagulation temperature is 60–100 °C, body temperature is 37 °C. Source: Graph courtesy of LightScalpel LLC, Bothell, WA.

100 Soft tissue temperature, T (°C)

T = 37 °C + 63 °C* [1 – 1.5 (x/δ) + 0.5 (x/δ)3] 90 80 70 60 Tcoag = 60 °C

50 40 0.0

0.2

0.4

0.6

0.8

1.0

Dimensionless distance from the soft tissue surface (x/δ)

10 Diode hot tip coagulation depth measurements from Romanos (2013):

Diode radiant (photo-thermal) coagulation depths Coagulation depth, HT (mm)

12

1

Temperature controlled No temperature control

“Leaky” diode hot tip

Diode hot tip (100% “black” char) coagulation depths. Wavelength independent

Temperature controlled hot tip

0.1

Power controlled hot tip

Blood capillary diameters, B = 20–40 μm 0.01 0.03

0.04

0.06

0.1

0.2

0.3

0.4

2

1.3

1

Hot tip handspeed (mm/s) For 0.4 mm diameter glass tip

13

10

8

6

4

3

Hot tip-to-tissue contact time (s)

Figure 1.13  Hot tip coagulation depth, HT (mm) as a function of tip‐tissue contact time (or hand speed). Logarithmic scales are in use. Source: Graph courtesy of LightScalpel LLC, Bothell, WA.

compared to measurements for constant temperature (red circles) and under constant power (blue circles) conditions (Willems et al. 2001; Braga et al. 2005; Faghri et al. 2010). Figure 1.13 illustrates that the hot fiber tip noticeably reduces the coagulation depth to less than 1 mm vs. multi‐mm Near‐IR photothermal coagulation depths (see Chapter 4). Also seen in Figure 1.13, the hot tip coagulation depth is affected by tip‐to‐tissue contact time (or by the surgeon’s hand speed, through skill and training), but still significantly exceeds blood vessel diameters.

The coagulation process and cutting capabilities of the hot tip strongly depend on the properties of the char on the diode’s glass tip. Insufficient charring can reduce the tip temperature (which brings sterility ­compliance concerns; FDA 2002) and increases risk of near‐IR‐induced sub‐surface thermal necrosis (Willems et al. 2001); it also heightens risks of bleeding due to tissue being cut by sharp edges of the glass tip. While solid‐state lasers certainly have their veterinary applications, it is important to remember these factors for efficacy of beam delivery and prevention of adverse collateral thermal injury to the patient.

­Reference

­References Braga WF, Mantelli MBH, Azevedo J. (2005). Analytical solution for one‐dimensional semi‐infinite heat transfer problem with convection boundary condition. AIAA. 4686. pp. 1–10. Endo M, Walter RF. (2007). Gas Lasers. Boca Raton, FL: CRC Press. Faghri A, Zhang Y, Howell JR. (2010). Advanced Heat and Mass Transfer. Columbia, MO: Global Digital Press. p. 260. FDA (2002). Updated 510(k) sterility review guidance K90‐1: final guidance for industry and FDA. U.S. Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health, Office of Device Evaluation. August 30. FDA (2005). Medical devices with sharps injury prevention features. Guidance for industry and FDA staff. U.S. Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health, General Hospital Devices Branch, Division of Anesthesiology, General Hospital, Infection Control, and Dental Devices, Office of Device Evaluation. August 9. Fisher JC. (1987). Basic laser physics and interaction of laser light with soft tissue. In: Shapshay SM, ed. Endoscopic Laser Surgery Handbook. New York, NY: Marcel Dekker. pp. 96–125. Fisher JC. (1993). Qualitative and quantitative tissue effects of light from important surgical lasers. In: Wright CV, Fisher JC, ed. Laser Surgery in Gynecology: A Clinical Guide. Philadelphia, PA: Saunders. pp. 58–81. ISO 10993‐1:2009 (2009). Biological evaluation of medical devices – Part 1: Evaluation and testing within a risk management process, 4th ed. ISO.

Ozisik NM. (1980). Heat Conduction. New York: Wiley. p. 352. Rathmore MM, Kapuno RRA. (2011). Engineering Heat Transfer, 2nd ed. Sudbury, MA: Jones & Bartlett Learning. p. 406. Romanos GE. (2013). Diode laser soft‐tissue surgery. Compend. Contin. Educ. Dent. 34(10). pp. 752–757. Romanos GE, Belikov AV, Skrypnik, AV, et al. (2015). Uncovering dental implants using a new thermo‐ optically powered technology with tissue air‐cooling. Lasers Surg. Med. 47. pp. 411–420. Saleh BEA, Teich MC. (1991). Fundamentals of Photonics. New York, NY: John Wiley. Siegman A. (1986). Lasers. Sausalito, CA: University Science Books. Verdeyen JT. (1989). Laser Electronics. Englewood Cliffs, NJ: Prentice Press. Vitruk P. (2012). Soft tissue cutting abilities of CO2 and diode lasers. Vet. Pract. News. 11. p. 24. Vitruk P. (2014). Oral soft tissue laser ablative and coagulative efficiencies spectra. Implant Practice US. 7(6). pp. 19–27. Vitruk P, Convissar R, Romanos G. (2014). Near-IR laser noncontact and contact tip-tissue thermal interaction differences. Paper presented at: Academy of Laser Dentistry 21st Annual Conference and Exhibition, Scottsdale, Arizona (27 February 2014). Vogel A, Venugopalan V. (2003). Mechanisms of pulsed laser ablation of biological tissues. Chem. Rev. 103(2). pp. 577–644. Willems PWA, Vandertop WP, Verdaasdonk RM, et al. (2001). Contact laser‐assisted neuroendoscopy can be performed safely by using pretreated ‘black’ fiber tips: experimental data. Lasers Surg. Med. 28(4). pp. 324–9.

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2 Understanding and Utilizing Power Density Noel Berger

­Introduction Laser light output is described in terms of energy, power, and their respective densities. The importance of power density cannot be understated as the paramount consideration in regard to a surgical laser’s ability to interact with biologic tissue; a concept referred to as laser–tissue interaction (LTI), which will be discussed later within this text. The most applicable features of a surgical laser’s power density will be demonstrated in this chapter.

­A Power Density Parable Energy is expressed in joules. Power = Energy/Time, expressed as J/s or W. Fluence = Energy/Area energy is applied, expressed as J/cm2. Power density = Power/Area power is applied, expressed as W/cm2. As an illustration to explain the concepts of energy, power, energy density, and power density, the example of a team of people building a wall using bricks will be used. For the sake of clarity, we can assume that all of the people are equal in all regards, and all of the bricks are equal in all regards. The location of the wall is irrelevant. The parameters that are at our disposal are the following: 1) the number of bricks that are being used to build the wall (energy density); 2) the length, width, and depth of each layer of bricks that are laid down (energy density); 3) the number of people working at any given time (power density); 4) the height of the wall being constructed (power density); 5) the time required to build the wall (power density).

In this first example, there is only one person to construct a wall that needs to be 10 ft high and 100 ft long. The wall is to be constructed using 1000 bricks that are 1 ft3 each. It takes this individual 1 hour to lay 100 bricks, so in this particular scenario, the wall will be completed in 10 hours. The energy required to do this task is represented by the total number of bricks, e.g. 1000 bricks of energy. The power required to do this work is a function of the time required to complete the task, e.g. 100 bricks per hour. The energy density is a function of the area that the wall takes up on the ground without regard to the time required to complete the task, e.g. 1 brick per square foot. Finally, the power density is a function of the energy density over time, e.g. 1 brick per square foot per hour. The parameters of this wall building exercise can be easily adjusted to provide greater illumination and clarity to define power density. We can change energy density by manipulating some of the five parameters mentioned earlier: By increasing or decreasing the number of bricks used to build the wall, we effectively change the wall itself, and within the parameters of the area contacting the ground, the energy density will be greater or lesser based on the depth of each layer, or the area of the wall in contact with the ground. When we change the depth of each layer of bricks that are laid down, the energy density of that wall increases or decreases. From either side of the wall it still looks like a wall, but it took more or less actual resources to construct each layer. We can change power density by manipulating any of the other parameters mentioned previously: By adding more workers, or using fewer workers, we will increase or decrease the power density of this project, assuming each worker produces effort at the same rate. From the earlier example where a brick layer can lay 10 bricks per layer per hour: If there are 10 people

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

­Laser Beam Geometr

working, then the project will be completed in one hour, but if only one person works for five hours, the wall will only be half‐completed. More profoundly, though, if we choose workers that have the power to lay 200 bricks per hour, the wall‐building power of that team has instantly doubled. Finally, the height of the wall has the most intense impact on our simplified understanding of power density. If the bricks occupy a given length and width (indicating energy density), and we increase or decrease the height of each of the individual bricks, the power density has subsequently increased or decreased, assuming all other influences of labor and time being equal. The power density required to perform work to build a wall that is made from taller bricks will be far greater than the power density required to perform work to build the standard wall that is 10 bricks high. It is the same with laser beams. We can change the energy level of the beam. We can change the area that the beam targets. We can manipulate how long the target is irradiated by the beam. We can change the time domain that it takes to release the specified energy of that laser beam. Thus, the concept evolves that energy and energy density relate to a quantifiable amount of work that can be performed by raw materials and their physical properties. Ultimately, power and power density are then time‐dependent functions of energy and energy density.

­Laser Beam Geometry The distribution of power density across a laser beam is called the transverse electromagnetic mode (TEM). Many distributions of power density are physically possible and are designated as TEMmn, where m and n are positive integers representing the number of troughs in the x‐direction and y‐direction of a three‐dimensional (3‐D) plot of the intensity profile of a beam traveling in the z‐direction (axis). Thus, a beam designated by TEM01 would appear to be a bell‐shaped dome having a deep central crater at the apex, appearing much like a typical volcano, and a beam designated by TEM30 would appear very similar to a bull’s-eye (Figure  2.1). Complicated TEMs are rarely desirable in surgery, and the most common useful mode of any laser beam is TEM00, or the fundamental mode. The geometry of a TEM00 laser beam is commonly known as Gaussian and is three dimensional. The highest power density, Pc, is at the center of the beam. Power diminishes logarithmically (Gaussian curve) with distance from the central axis. The effective diameter, de, of the laser beam is represented by a cross section at radius r = w, which defines an area equal to 86.5% of the total

(a)

(b)

(c)

Figure 2.1  Selected transverse electromagnetic modes (TEMs) of a laser beam. (a) The fundamental mode (TEM00) is Gaussian, with the power of the beam highest at the center and diminishing logarithmically toward the edge. (b) TEM01 has practically no power at the center of the beam and has high power at the inner circumference of the beam that diminishes logarithmically toward the edge. (c) TEM30 is comprised of concentric laser beams: the center of the beam is Gaussian, the middle beam has lower power, and the outer beam has the lowest power. Many other TEMs exist but are not desirable for use in surgery. Pc

de = 2w

Figure 2.2  Above is a 3‐D representation of a Gaussian laser beam and the relative power within its spatial confines. Below is the cross section of this laser beam perpendicular to its axis of propagation. Note that in a Gaussian laser beam, the center of the beam, Pc, possesses 100% of the power; this power diminishes logarithmically toward the periphery of the laser beam. At radius r = w = 1/2 de, the beam contains 86.5% of the total power density of the beam. There is very low power beyond the effective diameter, de, while within the effective diameter the power will be much higher.

spot. Here, the power Pr = Pc e−2. It follows then, that at radius r  w, the fluence will be very low compared to the center of the laser beam (Figure 2.2).

15

16

Understanding and Utilizing Power Density

­Power Density’s Effect on Tissue Power density is the most important element of laser physics for the veterinary laser surgeon to comprehend. Understanding this concept fully will substantially increase the ability of the surgeon to achieve consistent, reproducible, and reliable therapeutic outcomes for the patient. There are basic guidelines for laser energy properties within soft tissue that any laser surgeon must understand. The laser’s effect depends on the power placed into the system to produce the photons and the power concentrated within the effective diameter of the laser beam. Power is usually expressed in watts on equipment settings. Any time laser energy is applied to a tissue to produce a desired effect and time is also a factor, the term “Joule” is used. A joule is defined as a watt‐second; it is the amount of time power is applied to a target tissue to produce a cumulative effect. The aperture spot size, also known as the focal spot, results in the concentration of energy within an area producing a power density, expressed as W/cm2. The advantage of a small focal spot size with adequate power applied over a specific time is optimal vaporization of the target tissue. This also produces less secondary collateral thermal damage to tissue. Fewer cells are affected, damaged, or destroyed at the margins of an incision when using higher power density. LTI depends greatly on wavelength. The 10 600 nm wavelength is strongly absorbed by water, which makes it an ideal laser for soft tissue surgical applications. The near‐infrared wavelengths are poorly absorbed by water and moderately absorbed by tissue pigments such as oxyhemoglobin and melanin, which make them acceptable for tissue coagulation or endoscopic applications. As long as the laser surgeon has a complete working knowledge of the wavelength applied and its expected results, consistent outcomes should be attainable within the limits of any wavelength. This is especially so with CO2 laser energy. If sufficient fluence (energy/area) is delivered to the tissue in a short period of time, vaporization occurs and a crater will be created at the tissue surface that has a 3‐D Gaussian profile. This is often referred to as the zone of vaporization and this will be discussed in greater detail in Chapter 3. When a deep laser crater is required, a small spot size is advantageous in that it concentrates a high amount of energy into the tissue due to extremely high amounts of excess fluence and rapid vaporization in that zone. When tissue heating or coagulation rather than vaporization is the desired effect, a larger spot size increases the area of the beam and thus reduces the total power density to the tissue. The energy is dispersed over a larger area, thus reducing fluence deposited to the target tissue. Lower power density is desirable for coagulation, and higher power density is desirable for ablation and incision.

If a surgeon desires to coagulate tissue without vaporizing it, the power density of the beam must not exceed the threshold of vaporization at that wavelength. The wavelength also should be poorly absorbed by histologic water and be scattered within the tissue, causing the conversion of laser energy to thermal energy and a slow increase in the temperature of the tissue. On the other hand, if a surgeon desires to precisely incise or cut tissue with minimal heating of surrounding tissues, the power density of the beam should far exceed the threshold of vaporization at that wavelength. The wavelength should be highly absorbed by water so that the light is attenuated rapidly as well. This causes rapid vaporization of tissue with minimal thermal conduction, but the ability to coagulate tissue is dramatically limited. There are conditions whereby a wavelength that causes coagulation can be used to cut, and likewise, there are conditions whereby a wavelength that causes vaporization can be used to coagulate. In general terms, to the extent that the effect of a given wavelength can vaporize and cut tissue, it loses the ability to coagulate tissue because that system dissipates heat efficiently. Likewise, the surgical effect of wavelengths that produce good coagulation are generally poorly ablative because they primarily generate heat as the result of that system’s LTI. There are power density thresholds that must be reached before the effects of rising temperature take place in the tissue. Since other effects may occur at higher and higher thresholds, the surgeon must apply the appropriate power density to achieve the desired threshold without exceeding the threshold for the next higher, undesired level. If a surgeon needs to only coagulate tissue, then the power density of the beam must be high enough to exceed the threshold for coagulation, but not so high as to cause vaporization. Equally true, a surgeon who is vaporizing or ablating tissue must avoid both char formation and coagulation. In this latter case, a power density should be selected that simultaneously exceeds both the thresholds of coagulation and vaporization but not the threshold of carbonization. These thresholds depend strongly on wavelength, power density, and tissue composition – specifically the water content. The boiling point of water, 100 °C, is reached rather quickly when CO2 laser power densities above 1500 W/ cm2 are applied, and produce the transformation of liquid water to steam vapor. Above 1500 W/cm2, the laser will consistently cause boiling. Below 10 W/cm2, only gentle warming of the water will occur. Between 100 and 1500 W/cm2, a mixture of warming and vaporization will occur. Within the soft tissue, these thresholds are almost equivalent. The mechanism of vaporization of soft tissue by a laser beam is the sudden boiling of histologic water to form steam. This intracellular steam expands rapidly and ruptures the relatively weak cell membranes that

­Altering Power Densit

previously confined it. The solid residue of cells and connective tissue are dehydrated and ejected from the impact zone of the laser beam and may actually ignite or burn, forming a plume of smoke. The temperature of the area not vaporized will be 5 mm

1 s Eth > 103 –104 J/cm2 H > 10 mm

1

Wavelength (nm)

90 10 00 00 0

50 00

00 30

15 00

10 00

0

220

0.33

3.3

mm

Blood vessel diameters B = 20–40 μm Absorption by H2O @ 75% concentration in soft tissue Absorption by HbO2 @ 150 g/l; Blood @ 10% in soft tissue

0.1

50

22

0.0033

0.033

2.2

0.7

70

0.22

Coagulation depth (H)

100

Photo-thermal ablation by CO2 lasers is 1000 times more energy efficient than by diode lasers

1000 times

1000

Photo-thermal coagulation by CO2 lasers is 5–15 times deeper than by Er lasers

0.007

J/cm2

2780 and 2940 nm Erbium lasers α ≈ 3300 and 9900 cm–1 TRT ≈ 60 and 6.7 μs Eth ≈ 0.6 and 0.2 J/cm2 H ≈ 10 and 3.3 μm

10 000

Ablation threshold fluence (Eth)

Absorption spectra of soft tissue (Figure  4.1) are summarized in Figure  4.12 with ablation thresholds and coagulation depths of soft tissue lasers for conditions most suited for high efficiency photothermal ablation (where pulse duration is shorter than thermal relaxation

ms

­Summary

time, t ≤ TR) with minimum collateral damage to surrounding tissue (pulse repetition rate f ≪ 1/TR). Soft tissue absorption in the 800–11 000 nm spectrum varies greatly: it is approximately 1000 times stronger for CO2 lasers relative to diodes, and it is approximately 10 times stronger for erbium lasers relative to CO2 lasers (i.e. approximately 10 000 times stronger for erbium lasers relative to diodes). Because near‐IR photons are weakly absorbed (1000– 10 000 times weaker than CO2 and erbium), diode lasers are not often used to cut soft tissue with photons. Instead, diode lasers cut soft tissue thermomechanically with hot charred glass tips (Figure 4.10c). These wavelengths are very useful in minimally invasive applications such as those using endoscopes, but are not efficient scalpels. Mid‐IR erbium laser wavelengths make these lasers highly energy efficient and spatially accurate photothermal ablation tools with poor coagulation efficiency. Coagulation depth can be increased by increasing pulse width and rate. IR CO2 laser wavelengths are highly efficient and spatially accurate photothermal ablation tools with good coagulation efficiency due to a close match between coagulation depth and soft tissue blood capillary diameters. Coagulation depth can be increased by increasing pulse

Thermal relaxation time (TRT)

For H ≪ B (diode laser wavelengths, Figure 4.11), optical absorption and coagulation depths are significantly greater than blood vessel diameters. Coagulation thus takes place over extended volumes far from the ablation site. Extended thermal damage zones for near‐IR irradiated soft tissue are documented in Willems et al. 2001; the documented 810 nm soft tissue absorption coefficient (0.7 cm−1) makes its observations highly relevant to the present analysis with absorption coefficient of approximately 0.4 cm−1 at 810 nm (Figure 4.1). For H > B (CO2 laser wavelengths, Figure 4.11), coagulation extends just deep enough into a severed blood vessel to stop the bleeding, more efficient then for the above two cases H ≪ B, and H ≫ B. Coagulation depth can be increased by increasing pulse width and rate in non‐ SuperPulse settings.

Soft tissue’ main chromophoroes’ absorption coefficient (cm–1)

40

Absorption by Hb @ 150 g/l; Blood @ 10% in soft tissue

Figure 4.12  Spectra of (a) absorption coefficient (cm−1), (b) thermal relaxation time (TRT) (ms), (c) short pulse ablation threshold fluence Eth (J/cm2) and (d) short pulse photothermal coagulation depth, H (mm), at histologically relevant concentrations of water, hemoglobin (Hb), oxyhemoglobin (HbO2) in subepithelial oral soft tissue. Logarithmic scales are in use. Source: Graph courtesy of LightScalpel LLC, Bothell, WA. Adapted from Duclos and Vitruk (2018) and Vitruk (2016).

­Reference

width and rate (non‐SuperPulse settings). The CO2 laser therefore fits the two requirements of an ideal soft tissue surgical laser scalpel, namely efficient vaporization of tissue and efficient cauterization of surgical margins, and is well suited to a great majority of soft tissue surgical laser ­procedures. Tissue vaporization is achieved through ­photovaporolysis of histological water. Tissue cauterization

is achieved through photopyrolysis of soft tissue in the ­temperature range 60–100 °C. Most significant for high ­fluence SuperPulse CO2 lasers, a coagulation depth of approximately 50 μm is sufficient for cauterization of sub‐50 μm diameters of blood vessel capillaries. The depth of coagulation can be extended upward of 500 μm for low fluence, long pulse, and continuous wave CO2 lasers.

­References Alberts B, Johnson A, Lewis J, et al. (2007). Molecular Biology of the Cell. 5th ed. New York, NY: Garland Science (Table 23‐1). Barton JK, Rollins A, Yazdanfar S, et al. (2001). Photothermal coagulation of blood vessels: a comparison of high‐speed optical coherence tomography and numerical modelling. Phys. Med. Biol. 46(6). pp. 1665–1678. Cheong WF, Prahl SA, Welch AJ. (1990). A review of the optical properties of biological tissues. IEEE J. Quantum Electron. 26(12). pp. 2166–2185. Duclos D, Vitruk P. (2018). Using soft tissue surgical lasers. Vet. Pract. News. 30(7). pp. 1, 38–39 (Figures 1‐2). Einstein A. (1905). Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen. Annalen der Physik. 322(8). pp. 549–560. Esen E, Haytac MC, Oz IA, et al. (2004). Gingival melanin pigmentation and its treatment with the CO2 laser. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 98(5). pp. 522–527. Fisher JC. (1987). Basic laser physics and interaction of laser light with soft tissue. In: Shapshay SM, ed. Endoscopic Laser Surgery Handbook. New York, NY: Marcel Dekker. pp. 96–125. Fisher JC. (1993). Qualitative and quantitative tissue effects of light from important surgical lasers. In: Wright CV, Fisher JC, eds. Laser Surgery in Gynecology: A Clinical Guide. Philadelphia, PA: Saunders. pp. 58–81. Hale GM, Querry MR. (1973). Optical constants of water in the 200 nm to 200 μm wavelength region. Appl. Opt. 12(3). pp. 555–563. Jacques SL. (1996). Origins of tissue optical properties in the UVA, visible, and NIR regions. In: Alfano RR, Fujimoto JG, eds. OSA TOPS on Advances in Optical Imaging Photon Migration, Vol. 2. Optical Society of America. pp. 364–369. Jacques SL. (2013). Optical properties of biological tissues: a review. Phys. Med. Biol. 58(11). pp. R37–R61. Mordon S, Rochon P, Dhelin G, et al. (2005). Dynamics of temperature dependent modifications of blood in the near‐infrared. Lasers Surg. Med. 37(4). pp. 301–307. Pang P, Andreana S, Aoki A, et al. (2010). Laser energy in oral soft tissue applications. J. Laser Dent. 18(3). pp. 123–131.

Pfefer TJ, Choi B, Vargas G, et al. (1999). Mechanisms of laser‐induced thermal coagulation of whole blood in vitro. Part of the SPIE Conference on Cutaneous Applications of Lasers: Dermatology, Plastic Surgery, and Tissue Welding. Proc SPIE. pp. 20–31. Prestin S, Rothschild SI, Betz CS, et al. (2012). Measurement of epithelial thickness within the oral cavity using optical coherence tomography. Head Neck. 34(12). pp. 1777–1781. Squier CA, Finkelstein MW. (2008). Oral mucosa. In: Nanci A, ed. Ten Cate’s Oral Histology: Development, Structure, and Function. 7th ed. St. Louis, MO: Mosby Elsevier. pp. 319–357. Squier CA, Brogden KA, eds. (2011). Human Oral Mucosa: Development, Structure, and Function. Chichester, West Sussex, UK: Wiley‐Blackwell. pp. 14–16. Svaasand LO. (2003). Lasers for biomedical applications. In: Driggers RG, ed. Encyclopedia of Optical Engineering. New York, NY: Marcel Dekker. pp. 1035–1041. Vitruk P. (2014a). Oral soft tissue laser ablative and coagulative efficiencies spectra. Implant Pract. US. 7(6). pp. 19–27. Vitruk P. (2014b). How CO2 lasers cut, coagulate soft tissue. Vet. Pract. News. 26(12). pp. 36–37 (Figures 1‐3). Vitruk P. (2016). Why soft‐tissue CO2 laser performs well. Vet. Pract. News. 28(12). p. 36 (Figure 1). Vogel A, Venugopalan V. (2003). Mechanisms of pulsed laser ablation of biological tissues. Chem. Rev. 103(2). pp. 577–644. Weast RC, ed. (1980–81). CRC Handbook of Chemistry and Physics. 61st ed. Boca Raton, FL: CRC Press. p. D‐174. Wieliczka DM, Weng S, Querry MR. (1989). Wedge shaped cell for highly absorbent liquids: infrared optical constants of water. Appl. Opt. 28(9). pp. 1714–1719. Willems PWA, Vandertop WP, Verdaasdonk RM, et al. (2001). Contact laser‐assisted neuroendoscopy can be performed safely by using pretreated ‘black’ fibre tips: experimental data. Lasers Surg. Med. 28(4). pp. 324–329. Yoshida S, Noguchi K, Imura K, et al. (2011). A morphological study of the blood vessels associated with periodontal probing depth in human gingival tissue. Okajimas Folia Anat Jpn. 88(3). pp. 103–109.

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5 Combining Laser Surgery with Laser Therapy (Photobiomodulation) David S. Bradley

­Introduction This book is dedicated mainly to surgical aspects of laser use, particularly photothermal laser‐tissue interactions in invasive methods to excise, incise, ablate, or otherwise remove or disrupt tissue. Lasers can also have a noninvasive, nonablative, photobiomodulation effect on tissue. This is a result of a photochemical effect between tissue and certain wavelengths of light. Laser therapy induces an optimal healing environment that relieves pain and inflammation, but more importantly, it directly enhances tissue repair, regeneration, and remodeling of both soft and hard tissue. The following pages will discuss these mechanisms briefly and then illustrate how they can be applied to improve the outcomes of laser and nonlaser surgical procedures.

­ he Science and Physiology T of Laser Therapy Laser therapy enables injured or stressed cells to ­function at their optimal capacity. It restores the normal biological function (Tunér and Hode 2002). Laser photobiomodulation therapy has a direct photochemical reaction within the body that stimulates a cascade of secondary effects and “downstream” physiologic reactions (Hawkins and Abrahamse 2007). As opposed to the CO2 laser that is in the far‐infrared range, the primary responses for photobiomodulation result from using photons within the visible red and near‐infrared ranges. They have a direct photochemical effect that enhances blood flow, improves tissue oxygenation, and results in an improved efficiency of the r­espiratory chain within the mitochondria of the cell due to changes in membrane permeability, resulting in improved signaling between mitochondria, nucleus and cytosol, nitric oxide formation, and increased oxidative metabolism to produce more ATP (Karu 1989). Other

direct effects include the production of reactive oxygen species as well as superoxide dismutase. It also causes a beneficial shift in the redox state. The “downstream” effect of secondary and tertiary reactions leads to the amplification of the primary photochemical reactions. Calcium is released from the mitochondria to improve and maintain adequate levels to improve cell metabolism and the regulation of signaling pathways responsible for significant events required for wound and tissue repair. Studies document enhanced cell migration, RNA and DNA synthesis, cell mitosis, protein secretion, and cell proliferation (Tunér and Hode 2002). Because this photochemical reaction works at such a basic metabolic level within the mitochondria, every cell in the body can respond favorably. Muscle or nerve cells and tissue that has been damaged can repair faster and better. Blood vessels and lymphatics will respond favorably, enhancing tissue perfusion and providing oxygen and nutrients. This enhanced blood flow and oxygenation to the treated area will help tissue healing (Larkin et al. 2012). The improved blood flow affected by laser therapy will extend well beyond the period of direct exposure. This is due to the warming effect and thermal gradient produced by some higher‐powered lasers. But more importantly, it is also due to the vasodilation elicited by the release of serotonin, histamine, and nitric oxide as well as the increased angiogenesis promoted by basic fibroblast growth factor and vascular endothelial growth factor (Kubota 2002). This is an important consideration when calculating dosage in the immediate postop period. We want to achieve the anti‐inflammatory, biostimulatory, and healing effects without creating too much vasodilation and blood flow. A lower dosage and power would be used in these situations. White blood cells will function efficiently to fight infection and clean up debris. The cascade of metabolic effects continues, which stimulates various physiological changes at the cellular level such as activation of fibroblasts, macrophages, and lymphocytes; growth factor release; neurotransmitter release; collagen synthesis; and

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

­Optimal Parameters for Laser Therap

improvement of cell membrane permeability and function of the Na+/K+ pump. Laser therapy also has a positive effect on prostaglandin production. This will mediate neutrophil activation, lymphocyte accumulation, and other inflammatory effects. Increased ATP will improve metabolic activity to increase oxygen and nutrient availability, which can enhance protein and enzyme production. It will stimulate and accelerate cell reproduction and growth, which leads to faster repair of damaged tissues and moderation of the inflammatory response (Wray et al. 1988; Karu 1989, 1999; Peavy 2002; Martin 2003; Vladimirof et  al. 2004; Karu and Kolyakov 2005; Hamblin and Demidova 2006). This improved rate and level of healing and reduction in inflammation will also reduce pain. But in addition, there is a direct stimulation of other cellular events that provides analgesia. Additional benefits of laser therapy for postoperative use include an enhanced production of collagen and epithelial cells and an improved alignment and organization of collagen fibers that enhances tensile strength of tendons. Photobiomodulation also stimulates a more normal distribution of Type I and Type III collagen during the healing process (Kubota 2002; Wood et al. 2010; Paraguassu et al. 2014). This will have positive effects that relate to musculoskeletal injury by improving the healing process and reducing intramuscular fibrosis (Herickson de Brito Vieira et al. 2014; Paolillo et al. 2014; Ribeiro et al. 2015). Again, all this leads to normalization of cell function. It enables the cell to do the job it is supposed to do and do its job better. Laser therapy does not make normal cells “super” cells. It does not stimulate an amplification of all metabolic processes, nor does it suppress them. It enables the cell to do its job, which sometimes means doing nothing. In vitro studies demonstrate that part of a cell’s normal function is to recognize normal cell‐to‐cell contact inhibition once cell cultures approach confluence. This is analogous, in vivo, to a healthy organism, which will regenerate healthy tissue, but stop further growth when healing is complete. This is a critical and unique feature to laser therapy. It accelerates normal healing and tissue regeneration without producing overgrowth or neoplastic transformation. Therefore, it improves the rate and health of the incision healing process with less scarring and better tensile strength (Figure 5.1).

­Optimal Parameters for Laser Therapy Let us briefly review the parameters of laser therapy that are important for optimal clinical response. The parameters of most concern include wavelength, power, delivery mode, and time. The two most important parameters that dictate how any laser is going to interact with living tissue are power and wavelength.

(a)

(b)

(c)

Figure 5.1  (a–c) This case illustrates severe plasma cell pododermatitis (a) treated via CO2 laser excision (b) followed with laser therapy to enhance healing and moderate the immune response. Figure (c) is 14‐ days postoperative. Source: Courtesy of Dr. Boaz Man.

Wavelength Wavelength is what determines the best function for a particular laser as well as dictating penetration efficiency (Figure 5.2). As mentioned, laser therapy works due to a

43

Combining Laser Surgery with Laser Therapy (Photobiomodulation)

Therapeutic window vs surgical region Mid-IR water absorption (NOTE: Broken Axes)

Goal: Maximal penetration with biological absorption

1500 cm–1

From an external source

Water continued into Mid-IR

Cellular targets in the near infrared (NIR) 440 nm

800 nm

Visible beam

Melanim

300

400

1000 cm–1

995 nm

Cytochrome c oxidase

970 nm

Hemoglobin (HbO2)

Water (H2O)

500 cm–1

Infrared (invisible beam) Absorbption (A.U.)

44

500

Visible (400–700 nm)

600

700

800

900

1000

0.36 cm–1

0.12 cm–1

10 000

10 600 11 000

Wavelength (nm)

CO2

UV (200–400 nm)

Figure 5.2  Absorption spectrum chart for the major chromophores involved in photobiomodulation. Source: Courtesy of David Bradley and K‐Laser.

wavelength‐specific form of photobiomodulation. Most therapy lasers now combine more than one wavelength due to a better understanding of the direct photochemical effects that are produced when a photon of light is absorbed by specific chromophores within the body (Longo et al. 1987; Moriyama et al. 2009; Emanet et al. 2010; Assis et al. 2012; Joensen et al. 2012). Available wavelengths are selected based on the target chromophores most important to the basic metabolic process of ATP production: water, Fe (hemoglobin), Cu (cytochrome‐c oxidase), and melanin and other superficial mediators (Figure  5.3). The shorter wavelengths (630–660 nm) are absorbed more superficially and lack the ability to penetrate as deeply as the longer wavelengths. These are very beneficial in wound healing (Al‐ Watban et al. 2007). Wavelengths within the 970–980 nm range have a moderately increased absorption by water. This can produce a mild warming effect in local tissues, especially if higher powered therapy lasers are used, thus creating a thermal gradient along which blood tends to flow. The 904–905 nm wavelength is closest to the peak of the hemoglobin absorption curve. This wavelength can enhance oxygen release into the tissue by as much as

30–50% over that which the 970–980 nm wavelengths are capable. Wavelengths in the 750–830 nm range are at the peak of absorption for the cytochrome‐c oxidase enzyme. This enzyme is found in the mitochondria of nearly every tissue of almost every living eukaryote and is the rate‐limiting step in the conversion of oxygen to ATP within the electron transport cycle. When cytochrome‐c oxidase has absorbed energy from a photon of light at these wavelengths, it can accelerate the step to improve ATP production, along with production of nitric oxide. This basic photochemical reaction improves blood flow, improves release of oxygen into the tissue, and improves the conversion rate of oxygen to ATP. Simultaneously delivering multiple wavelengths can give a synergistic effect and a wider range of treatment options that should result in better clinical outcomes. Power The next most important parameter to discuss is power. Specifically, we need to understand irradiance and fluence and how these principles relate to dosage. There is

­Optimal Parameters for Laser Therap

Chromophore

Biological target

Biological effect

970 nm

Water

Blood

Stimulates microcirculation

915 nm

Iron

Hemoglobin

Increases cell oxygenation

810 nm

Copper

Cytochrome c oxidase

Enhances ATP production

660 nm

Melanin

Skin

Promotes wound healing

Figure 5.3  Targeted photobiomodulation.

nothing inherently good or bad or better or worse about a high‐powered vs. a low‐powered laser. It depends on what you want to treat with laser therapy that will determine the best therapeutic laser for your facility. Let us start with a few basics here: “Power” is the rate of delivery of energy and is measured in watts which is 1 J/s. “Energy” is the total number of joules delivered and is simply calculated by multiplying your power by time in seconds. Power (W) × time (s) = dosage (J). “Irradiance” is the amount of power (W) delivered to a specific area. “Fluence” is the total amount of energy (J) delivered to a specific area. In laser therapy, this would be your dosage to a given area. Dosage is calculated in the same manner for all lasers. It does not matter if it is a Class III or a Class IV Laser or if it is being delivered in continuous wave (CW), repeat pulse (RP), or SuperPulse (SP). Put simply, dose is measured in joules, and one watt delivers one joule per second. It is the average power capable of being delivered by a specific laser therapy device that is critical to proper dosage administration. The photons of laser light (or any light) are constantly being scattered, reflected, and absorbed within tissue. As laser light travels through tissue, the number of photons reaching a specific depth will decrease at a calculated rate. This attenuation or “decay” of the incident laser beam has to be considered when calculating the number of photons needed to elicit a direct photochemical effect on tissue, especially if the desired target tissue is not on the surface. This decay and therefore the actual dosage delivered at any particular depth from the incident beam is calculated by equations such as the Boltzmann transport equation, diffusion equation, the scattering coefficient, and others. A full explanation of these interactions is beyond the scope of this chapter but can be found in the literature (Anderson and Parrish 1981).

Power is a critical component when determining efficiency, efficacy, and safety. It is imperative to success to have the proper number of photons delivered at a proper rate to saturate the desired volume of tissue. Even though we often talk in terms of power and energy, what we are really interested in is irradiance and fluence of the tissue. Power is what dictates the rate of delivery to the tissue. If delivered too rapidly, especially to a very small area (high irradiance), then superficial tissue heating could occur. If delivered slowly or over a broader area, then all the positive effects will be experienced in a large volume of direct tissue stimulation in a reasonable amount of time. The total energy (fluence) delivered to a tissue or body part will be a direct result of the irradiance (power delivered per unit area) at that depth, times the time of exposure. Dosages listed and recommended in the literature range from 1 to 2 J/cm2 for superficial wounds and acute superficial musculoskeletal conditions, to 10 J/cm2 or higher depending on the size and depth of the lesion, its severity, and its chronicity (Tunér and Hode 2002; Al‐ Watban et  al. 2007; Hawkins and Abrahamse 2007; Peplow et al. 2010). The classification of lasers is dictated by ANSI Standards and is based on the maximum average power output of any and all laser devices (ANSI 2014). Maximum laser output is calculated by the total average power (J/s), not a single burst or peak power. Therefore, if you want to administer laser therapy to small patients and superficial wounds as well as to larger patients and deep musculoskeletal or neurologic conditions, then selecting a laser that has a broad range of power adjustability from high to low will give the best results on the widest range of conditions. Delivery Methods and Time Varying how laser light is delivered to the tissue also has clinical significance. Laser light can be delivered in CW, RP, or SP. The literature continues to show that by adding

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Combining Laser Surgery with Laser Therapy (Photobiomodulation)

pulse frequencies to treatment protocols along with continuous wave delivery, we may have an enhanced effect on overall long‐term results across a broader range of applications and patient conditions. By modifying the pulse rate with which the laser is being delivered, we can have differing physiologic effects on cell–tissue structures (Cheida et al. 2002). It has also been shown that different tissue cultures and cell types respond differently to differing pulse rates (Karu 1997). SuperPulse is another laser delivery mode for some lasers, including some surgical, therapeutic, and industrial lasers. Using SuperPulse in therapeutic lasers can mitigate thermal and absorption effects of pigmented tissue. It may therefore (in theory) improve penetration, and with proper parameters increase the number of photons that reach the target tissue (Joensen et  al. 2012; Anders and Wu 2015). It is very important to keep in mind the average power and the total joules per minute being delivered by a laser for effective results. Do not be misled by statements of peak power, especially if the average power is very low, thusly producing inadequate dosage and power for effective photobiomodulation in larger areas or deeper tissue. Therapy lasers transmit their energy through some type of handpiece. Many handpieces available today can be used in a contact or noncontact technique (Enwemeka 2009; Peplow et al. 2010). Contact delivery is especially important for most musculoskeletal conditions in our veterinary patients because most of our patients are covered in fur. In human treatments, clothing is always removed. Realize that there is no evidence that any type of handpiece is superior to any other type in proper laser energy administration. In some acute musculoskeletal conditions, and particularly in postoperative treatments where any hair coat has been shaved, a noncontact delivery may be used. In all treatments, the handpiece should be held perpendicular to the surface area, and the line‐ of‐drive should be monitored so the energy is better distributed over the target tissue. Your line of drive or directional position of the handpiece should correlate with the anatomy and the direction of the target tissue distal to the handpiece. Understanding the physics of laser–tissue interactions is just as important as the physiology and biochemistry. Although laser therapy may seem a very complicated proposition, the physiology and dosages are becoming better understood and documented every day. Studies continue to improve our knowledge of the mechanisms and optimal parameters behind successful laser therapy. There are many patient variables that affect dose: coat length and color, skin color, hydration, vascularity, chronicity, severity, and even individual patient response. As we understand laser– tissue interactions and as more accurate measurements

and calculations are established, we can better ­quantify minimum desired dosages. This has led to advancements in laser technology and improved understanding of the science and physics that allows the incorporation of preset protocols to deliver proper dosages safely and accurately as well as simplify treatments for veterinary personnel. Because of the wide margin of safety and ease of use, it can and should be delegated to the veterinary staff for the most efficient and economic benefits. Two principles should be kept in mind, ­however. The first is that the only thing we can say for sure at this time is that if you administer too little a dosage, you will produce little to no response. And the second is that there is a very wide margin of safety for laser therapy. Initial comprehensive education and training is essential, but ongoing review and support are just as critical to realize the full benefits of laser therapy. This review of the basic tenets of laser therapy that moderate the inflammatory response, reduce pain, and enhance the healing process illuminate why it is an ideal adjunct for any nearly postoperative situation. Laser therapy works well in conjunction with other modalities and medications. It can reduce the incidence of incision complications and enhance the overall speed and quality of tissue healing (Dungel et al. 2014; Figurova et al. 2016). It will also have positive effects on deeper tissue manipulated during surgery, whether this tissue is exposed with a CO2 laser or other methods. It will enhance osteogenesis in postorthopedic surgeries (Barbos et  al. 2003; Kasem et al. 2004; Pinheiro et al. 2006; Fujimoto et al. 2010; Poosti et  al. 2012; Chang et  al. 2014). It will also enhance the ­healing in soft tissue structures including muscle ­tissue and muscle repair (Assis et  al. 2012; Ribeiro et al. 2015). In addition to the beneficial healing properties, laser therapy can further enhance the reduced postoperative pain that is associated with surgery. Laser therapy has been shown to be extremely effective in providing analgesia, both short term and long term. This enhanced patient comfort will reduce the level and duration of analgesics needed. The combined benefits of laser surgery and laser therapy serve to further reduce inherent healing risks and will shorten the time to recovery. Consequently, the veterinarian is less likely to encounter the secondary problems related to postoperative inactivity such as muscle atrophy, weakness, and loss of conditioning, as well as the more severe consequences of prolonged recumbency, pressure sores, and urine scalding. Thus, laser therapy is a tremendous adjunct to the rehab process that will allow patients to return to their normal activity and become an active member of the family more quickly (Simunovik et al. 2000).

­Specific Recommendation

­General Guidelines These guidelines will help you understand proper laser protocols. They will also help you individualize treatments for patients not responding to the preset programs, or for those conditions that do not fall under the typical preset protocols on many laser settings. Some Injuries May Respond to a Graduated Treatment from Lower to Higher Frequencies For example, start with CW, then go to 20 Hz, followed by 500  Hz, followed by 2500–5000  Hz. The protocols programmed into some lasers will do this for you automatically. Laser Therapy Has a Wide Margin of Safety For acute or sensitive conditions, always err on the conservative side when calculating. You can start conservatively and get more aggressive if a response is not observed within three to four treatments. Thermal Effects Vary with Hair Coat and Pigmentation: Darker Absorbs More If you get a withdrawal response, add SuperPulse to the CW phase, increase the spot‐size on the handpiece, increase the distance of the handpiece from the tissue, move the handpiece more rapidly, or reduce power. Noncontact Applications This may be used for all incisions and other immediate postoperative conditions. It is also used on open wounds or any area with discharge or exudates, or on very painful or sensitive areas. Noncontact treatments are almost always done in a scanning mode. Scan 1–2 cm from the surface over both the affected area and 2–5 cm of surrounding healthy tissue with slow passage (about 3 cm/s). Laser Therapy Effects Are Cumulative Response should improve with each treatment until healed. Again, other than with small and routine surgeries that are often treated just once during recovery, most should receive a minimum of three to six treatments (akin to 10–14 days of antibiotic therapy) in most cases. These postoperative surgeries should be treated two to three days in a row. Then continue every other day or twice weekly for another three to five treatments. If needed, continue twice weekly or at least once weekly until the surgical site is healed. As a general laser therapy principle, if positive response is not noticed in two to three treatments, then increase the dose by 25–50% per treatment until a positive response is observed. You can also expand your treatment area to include more of the potentially involved tissue.

Laser Therapy Is Extremely Safe Although the following contraindications are still listed in the literature, some of these may be removed or modified as we gain a better understanding of all the physiologic mechanisms behind laser therapy: Direct exposure to the eye. Direct exposure to any cancer/malignancy. (If a tumor has been removed with adequate margins, laser therapy may be cautiously used post‐operatively to improve healing.) Direct exposure to a gravid uterus. Direct exposure to a joint within seven days of an intra‐ articular or epidural injection of a steroid or non‐steroidal medication. Direct exposure to an area of active bleeding (due to the therapy laser’s vasodilatory effects). Direct exposure to photosensitive patients, especially those undergoing or recovering from photodynamic therapy.

­Treatment Techniques Current Dosage Recommendations for Postoperative Incisions and Joints Superficial Wounds/Incisions. Clean Contaminated

2–4 J/cm2 4–10 J/cm2 or higher

Deep Wounds/Infected Wounds/Orthopedics. 4–8 J/cm2 6–10 J/cm2

Superficial tendons/ligaments Deep joints/fractures Power Guidelines. Area Skin and mucosa Carpus/tarsus Shoulder Stifle Thoracic and lumbar spine, hip Neck

Power (W) 1–3 3–6 4–7 3–6 6–10 5–10

Optimum Beam Frequency (the preset protocols should incorporate these into the program). Pain/neuralgia Edema/swelling General stimulation Inflammation Infection

2–20 Hz or CW 1 000 Hz 500 Hz 5 000 Hz 10 000 Hz

­Specific Recommendations We will now discuss some specific conditions and situations and how to incorporate laser therapy into your standard postoperative routine. This section will discuss

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soft‐tissue healing that will include routine incisions and excisions as well as more advanced and invasive reconstructive surgeries. It will also discuss hard‐tissue healing including all orthopedic conditions. Elective Surgeries and Simple Incisions and Excisions Applying laser therapy as part of your routine postsurgical “pain package” is a common practice in many veterinary facilities. As mentioned above, this has been shown to reduce the incidence of suture and incisional complications. For most simple elective surgeries, this is usually done only once during recovery (Figure 5.4). Adhering to the principles discussed above and using a “wound” or “incision” setting on your device, you would deliver 2–4 J/ cm2 of laser energy to each incision and a surrounding margin of healthy tissue in a noncontact method. For declaws the same protocol can be applied, delivering a total of 60 J per paw. The laser energy is applied to the toes as well as the metacarpal and metatarsal areas. Soft Tissue Trauma and Reconstructive Surgery Including Grafts and Skin Flaps Laser therapy will greatly reduce the severe inflammatory response often associated with these surgeries. It can enhance the success of flap viability by the general principles of enhanced cellular and vascular stimulation. In these cases, the laser energy would be delivered over the entire area of injury, graft, or flap (Figure  5.5a). A “wound” protocol would normally be used. For grafts and skin flaps, a starting dosage of 2–4 J/cm2 would be

used. For injuries related to trauma (HBCs, falls, dog/cat fights, etc.), a larger dose may be applied to account for some of the damage suffered by deeper tissue structures (Figure 5.5b) (Pinfildi et al. 2005; Mak et al. 2012; Larkin et al. 2012). The same principles will apply to any intraabdominal incisions and repairs (Figure 5.6). Laser therapy can be used on any structure that can be targeted directly by exteriorizing or creating an open path for the laser beam to penetrate. It can be administered by the ­surgeon by wrapping the handpiece in a sterile sleeve. A more efficient use would be to adjust aperture size down to allow administration by the surgical technician. They can remain above the sterile field while the  surgeon provides access to the desired tissue (Figure  5.6a). The dosage delivered would be similar to  any other surgical incision, including the margin of  healthy tissue (Figure  5.6b). Use a “wound” or ­“incision” setting and apply 2–4 J/cm2. Although surgical lasers are used almost exclusively for soft‐tissue procedures, they can be used for orthopedic procedures on approach to gain access to hard tissue. For postoperative orthopedic surgeries, we want to enhance both soft‐tissue and hard‐tissue recovery. In cases such as these, the therapy laser is directed, and the dose is calculated to target the deep tissue structures (Figure 5.7). The incision and all other superficial structures in between will also receive an adequate dose of laser energy to enhance healing, reduce inflammation, and provide analgesic benefits. The depth of the structure and the size of the patient will dictate the appropriate dosage. Treat above and below the joint and as circumferentially as possible.

Figure 5.4  Images of ovariohysterectomy incisions postoperatively. The incision on the left did not receive laser therapy post‐ operatively. This incision on the right did receive laser therapy immediately post‐ operatively. Source: Courtesy of Dr. Susan Kelleher.

­Specific Recommendation

(a)

(b)

Figure 5.5  (a) Laser therapy following aural hematoma surgery. Source: Courtesy of Dr. Christopher Joseph Winkler. (b) Soft‐tissue wound prior to laser therapy (top), one day after (middle), and two days after (bottom) starting laser therapy. Source: Courtesy of Dr. Boaz Man.

(a)

(b)

Figure 5.6  (a, b) Intraoperative laser therapy of a bladder incision postcystotomy for stone removal (a), and an abdominal incision following exploratory surgery (b). Source: Courtesy of Dr. Christopher Joseph Winkler.

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(a)

(b)

Figure 5.7  Severe comminuted fracture in a sandhill crane shown preoperative (a) and four weeks postoperative (b) with complete healing. Source: Courtesy of Dr. Santiago Diaz.

­Conclusion I want to emphasize again that laser therapy is not just a “nondrug” pain reliever. One of the most exciting aspects of laser therapy is its ability to directly stimulate tissue repair, remodeling, and regeneration, even in chronic conditions. We are seeing improvement and resolution of things that

were traditionally less responsive, as well as helping procedures we encounter everyday heal faster and better. This is why there is so much excitement about laser therapy. This is why laser therapy is becoming an integral part of postoperative healing and recovery in main stream medicine. And this is why over 50% of your colleagues now offer laser therapy as part of their clinical armamentarium.

­References Al‐Watban FAH, et al. (2007). Low‐level laser therapy enhances wound healing in diabetic rats: a comparison of different lasers. Photmed. Laser Surg. 25(2). pp. 72–77. Anders JJ, Wu X. (2015). Comparison of light penetration of 810 nm and 904 nm wavelength light in anesthetized rats. Lasers Med. Sci. 30(8). p. 2041. Anderson RR, Parrish JA. (1981). The optics of human skin. J. Invest. Dermatol. 77(1). pp. 13–19. ANSI. (2014). American National Standard for Safe Use of Lasers ANSI Z136.1 – 2014. Washington, DC: American National Standards Institute. Assis L, et al. (2012). Low‐level laser therapy (808 nm) reduces inflammatory response and oxidative stress in rat tibialis anterior muscle after cryolesion. Lasers Surg. Med. 44(9). pp. 726–735. Barbos PA, et al. (2003). Effect of 830‐nm laser light on the repair of bone defects grafted with inorganic bovine bone and decalcified cortical osseous membrane. J. Clin. Laser Med. Surg. 21(6). pp. 383–388.

Chang W‐D, et al. (2014). Therapeutic outcomes of low‐ level laser therapy for closed bone fracture in the human wrist and hand. Photomed. Laser Surg. 32(4). pp. 212–218. Cheida AA, et al. (2002). Resonance response of cell tissue structures to impulse frequency of infrared laser radiation of low intensity. Vopr Kurortol Fizioter Lech Fiz Kult. (6). pp. 33–35. Dungel P, et al. (2014). Low level light therapy by LED of different wavelength induces angiogenesis and improves ischemic wound healing. Lasers Surg. Med. 46. pp. 773–780. Emanet SK, et al. (2010). Investigation of the effect of GaAs laser therapy on lateral epicondylitis. Photomed. Laser Surg. 28(3). pp. 397–403. Enwemeka CS. (2009). Intricacies of dose in laser phototherapy for tissue repair and pain relief. Photomed. Laser Surg. (3). pp. 387–393. Figurova M, et al. (2016). Histologic assessment of a combined low‐level laser/light‐emitting diode therapy

­Reference

(685 nm/470 nm) for sutured skin incisions in a porcine model. Photomed. Laser Surg. 34(2). pp. 53–55. Fujimoto K, et al. (2010). Low‐intensity laser irradiation stimulates mineralization via increased BMPs in MC3T3‐E1 cells. Lasers Med. Surg. 42. pp. 519–526. Hamblin MR, Demidova TN. (2006). Mechanisms of low level light therapy. Proc. SPIE 6140(612001). pp. 1–12. Hawkins D, Abrahamse H. (2007). Phototherapy – a treatment modality for wound healing and pain relief. African J. Biomed. Res. (10). pp. 99–109. Herickson de Brito Vieira W, et al. (2014). Use of low‐level laser therapy (808 nm) to muscle fatigue resistance: a randomized double‐blind crossover trial. Photomed. Laser Surg. 32(12). pp. 678–685. Joensen J, et al. (2012). Skin penetration and time‐profiles for continuous 810 nm and superpulsed 904 nm lasers in a rat model. Photomed. Laser Surg. 30(12). pp. 688–694. Karu T, Kolyakov SF. (2005). Exact action spectra for cellular responses relevant to phototherapy. Photomed. Laser Surg. 23(4). pp. 355–361. Karu T. (1989). Photobiology of Low Power Laser Therapy. London: Harwood Academic Publishers. Karu T. (1997). Nonmonotomic behavior of the dose dependence of the radiation effect on cells in vitro exposed to pulsed laser radiation at 820 nm. Lasers Surg. Med. 21(5). pp. 485–492. Karu T. (1999). Primary and secondary mechanisms of action of visible to near‐IR radiation on cells. J. Photochem. Photobiol. B 49(1). pp. 1–17. Kasem KM, et al. (2004). Enhancement of bone formation in rat calvarial bone defects using low‐level laser therapy. Oral Surg. Oral Med. Oral Pathol. Oral Endod. 97. pp. 693–700. Kubota J. (2002). Effects of diode laser therapy on blood flow in axial pattern flaps in the rat model. Lasers Med. Sci. 17(3). pp. 146–153. Larkin KA, et al. (2012). Limb blood flow after class 4 laser therapy. J. Athl. Train. 47(2). pp. 178–183. Longo L, et al. (1987). Effects of diode‐laser silver arsenide‐ aluminum (Ga‐Al‐As) 904 nm on healing of experimental wounds. Lasers Surg. Med. 7(5). pp. 444–447. Mak Michael CH, et al. (2012). Immediate effects of monochromatic infrared energy on microcirculation in healthy subjects. Photomed. Laser Surg. 30(4). pp. 193–199. Martin R. (2003). Laser accelerated inflammation/pain reduction and healing. Pract. Pain Manag. (Nov/Dec). pp. 20–25.

Moriyama Y, et al. (2009). In vivo effects of low level laser therapy on inducible nitric oxide synthase. Lasers Surg. Med. 41(3). pp. 227–231. Paolillo FR, et al. (2014). Low‐level laser therapy associated with high intensity resistance training on cardiac autonomic control of heart rate in wister rats. Lasers Surg. Med. 46. pp. 796–803. Paraguassu G, et al. (2014). Effect of laser phototherapy (660 nm) on type I and III collagen expression during wound healing in hypothyroid rats: an immunohistochemical study in a rodent model. Photomed. Laser Surg. 32(5). pp. 281–288. Peavy GM. (2002). Lasers and laser‐tissue interaction. Vet. Clin. Small Anim. 32(3). pp. 517–534. Peplow PV, et al. (2010). Laser photobiomodulation of wound healing: a review of experimental studies in mouse and rat animal models. Photomed. Laser Surg. 28(3). pp. 291–325. Pinfildi CE, et al. (2005). Helium–neon laser in viability of random skin flaps in rats. Lasers Med. Surg. 37. pp. 74–77. Pinheiro Antonio Luis B, et al. (2006). Photoengineering of bone repair processes. Photomed. Laser Surg. 24(2). pp. 169–178. Poosti AM, et al. (2012). The effect of low level laser on condylar growth during mandibular advancement in rabbits. Head Face Med. 8. p. 4. Ribeiro BG, et al. (2015). The effect of low‐level laser therapy (LLLT) applied prior to muscle injury. Lasers Surg. Med. 47. pp. 571–578. Simunovik Z, et al. (2000). Wound healing of animal and human body sport and traffic accident injuries using low‐level laser therapy treatment: a randomized clinical study of seventy‐four patients with control group. J. Clin. Laser Med. Surg. 18(2). pp. 67–73. Tunér J, Hode L. (2002). Some basic laser physics. In: Laser Therapy – Clinical Practice and Scientific Background. Grangesberg: Prima Books AB. pp. 12, 21, 22. Vladimirof YA, et al. (2004). Photobiological principles of therapeutic applications of laser radiation. Biochemistry (Moscow). 69(1). pp. 81–90. Wood VT, et al. (2010). Collagen changes and realignment induced by low‐level laser therapy and low‐intensity ultrasound in the calcaneal tendon. Lasers Med. Surg. 42(6). pp. 559–565. Wray S, et al. (1988). Characterization of the near infrared absorption spectra of cytochrome aa3 and haemoglobin for the non‐invasive monitoring of cerebral oxygenation. Biochim. Biophys. Acta 933(1). pp. 184–192.

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6 Laser Safety in the Operating Theater Christopher J. Winkler

­Introduction Although the benefits of surgical lasers are plentiful and rewarding, their potential to do harm, both to veterinary personnel and patient, should never be overlooked. Well‐rounded training with surgical lasers is not limited to the particulars of physics and biophysics, procedures, settings, and technique. It also includes knowledge of the potential for accident and injury in using these devices, coupled with the development of a situational awareness of both surgeon and staff for their patient and operating environment. It is not the surgical instrument itself that causes harm, but the person who uses it inappropriately. As the use of medical and surgical lasers becomes more prevalent in today’s veterinary facilities, the inclusion of laser safety discussions becomes essential to any comprehensive laser curricula being considered to prepare veterinary students and practitioners for the equipment awaiting them. Laser practitioners should learn to incorporate a checklist of laser safety measures into their everyday procedures. Such laser safety measures should include both those that apply to all surgical procedures, and special considerations tailored for a particular surgical procedure requiring additional forethought for laser safety. Though this chapter will review here many of the most important hazards pertinent to the use of lasers in a veterinary surgical setting, it should not be intended as a substitute for the more comprehensive guidelines laid down by the American National Standards Institute (ANSI) and for mandated federal and state regulations regarding the use of lasers in the workplace, specifically in the veterinary practice; the reader is strongly advised to become familiar with the latest versions of such.

­ overnment Regulations and ANSI G Standards US Federal and State Regulations Laser safety is overseen at the federal level by the Center for Devices and Radiological Health (CDRH) within the US Food and Drug Administration (FDA). The FDA clears premarket approval of medical devices and observes and enforces specific laser safety standards to be provided by manufacturers. State board regulations and any necessary state licensing for the safe use of lasers within the veterinary facility should also be examined and implemented by practice owners, office managers, laser surgeons, and laser safety officers (LSOs) (ANSI 2011).

ANSI Standards and the Laser Classification System ANSI created and continues to periodically update the Z136 series of documents as a guide for the safe use of lasers in the workplace. ANSI Z136.1 describes general laser safety use, while ANSI Z136.3 details their safe use in health care. In 2011, Z136.3 was updated to include guidelines for the veterinary profession. Federal regulations and the ANSI standards classify lasers according to the potential damage they may do to the eye and the skin. Some variations within the classes exist to allow for risk potential differences in operating power, whether the laser is viewed through an optical collection device (such as a magnifier), and some specific operating wavelengths. Manufacturers are required to apply warning labels to all laser products rated Class 2 and above (ANSI 2011).

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

­Maximum Permissible Exposure and Safeguarding the Nominal Hazard Zon

Class 1

Class 1 lasers include lasers that cannot cause eye or skin injury during normal operations, usually because they are enclosed and therefore never allowed exposure to eyes or skin. These devices typically operate at less than 1 mW. Examples include CD and DVD players. Class 2

Class 2 lasers include visible lasers that only remain safe from being a potential eye hazard by virtue of the aversion response or “blink reflex” (5

4–10

0

0

1–3

>4

>10

0

0

0

>1

and infection through vaporization of infectious agents and neoplastic cells at the surgical site. Furthermore, since FP surgeries typically involve multiple excisions, the noncontact incision of the laser prevents accidental bacterial and neoplastic contamination of consecutive surgical sites. The local thermal effects combined with decreased tissue manipulation have been shown to decrease the chances of tumor seeding and recurrence (Lanzafame et al. 1988a,b). There are some disadvantages of using the CO2 laser that must be considered during FP excision. Since many tumors grow on or near boney tissue of the carapace, plastron, skull, or digits, the surgeon must adjust for these locations to prevent complications. The power necessary to penetrate the epithelium and dense soft t­ issue closely associated with the bone to effectively ablate neoplastic

Prior to surgery, sea turtles with FP should undergo a thorough diagnostic work up to assess their overall health and screen for the presence of internal visceral tumors. The ideal database prior to surgery includes a complete physical exam, complete blood cell count (CBC) with differential, plasma chemistry panel, radiographs, computed tomography (CT), GI endoscopic exam, and laparoscopic exam of the coelomic cavity. While none of these diagnostics are definitive, they are the most comprehensive tools available at this time. Radiography and ultrasonography have very limited sensitivity for internal tumor identification. Larger ­ tumors, especially pulmonary, are often visible on radiographs (Figure 21.2). CT studies are more sensitive for smaller pulmonary lesions, but tumors can still be overlooked (Figure 21.3). Renal tumors and other coelomic visceral tumors are rarely visualized on CT. These tumors are sometimes identified with endoscopic and laparoscopic exams (Figure 21.4). However, tumors on the dorsal aspect of lungs or ­kidneys, and within organ parenchyma, will not be visible (Mader 2006). Magnetic resonance imaging (MRI) can be more sensitive for smaller visceral tumors. However, MRI requires heavy sedation and is often not readily available or is cost‐prohibitive (Croft et al. 2004). Turtles affected with FP are commonly found to be emaciated, anemic, and have pneumonia or other infections and injuries. These conditions often require stabilization and treatment prior to surgery. For anesthetic safety and decreased postoperative morbidity, a general rule of thumb is that the animal should be determined to be healthy enough overall for general anesthesia and have an albumin >1.0 g/dl and a PCV (packed cell volume) >20%, depending on the size and number of tumors being excised. Periocular tumors typically have less bleeding and less exposed surface area, and therefore can be done with lower values. Turtles with small tumor burdens often do not require general anesthesia and have less risk of hemorrhage, and surgery can be performed during more debilitated conditions using local anesthesia.

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Laser Surgery in Aquatic Animals (Sea Turtles)

(a)

(b)

Figure 21.2  (a–b) Radiographs of juvenile green sea turtle (Chelonia mydas) with pulmonary fibropapillomatosis. (a) Dorsoventral view showing numerous soft tissue nodules of various size throughout the pulmonary fields (several are highlighted with arrows). (b) Left lateral view showing multiple soft tissue nodules of various size within the pulmonary parenchyma (some lesions are highlighted with arrows).

Figure 21.3  Images of three‐view computed tomography (CT) scan of a juvenile green sea turtle (Chelonia mydas) with a visible pulmonary mass (highlighted with arrows) consistent with fibropapillomatosis.

Turtles undergoing surgery for excision of FP tumors often require general anesthesia for the procedure. A variety of sedation protocols are acceptable (Norton et  al. 2017). At our rehabilitation facilities, a common sedation protocol includes a combination of intravenous dexmedetomidine 50  μg/kg, ketamine 1.0–1.5  mg/kg, and butorphanol 0.4 mg/kg. Isoflurane or sevoflurane are recommended for anesthetic induction and maintenance. Local anesthesia is also used in conjunction with

general anesthesia for additional intraoperative and post‐operative analgesia, which lowers necessary gas concentrations (Figure 21.5). Lidocaine 2% or lidocaine 1% + epinephrine is administered up to 6 mg/kg total dose as local subcutaneous (SC) ring blocks or SC splash blocks around the tumors. The lidocaine can be diluted with sodium bicarbonate or saline to increase volume for larger tumor burdens. Lidocaine 2% (preservative free) can also be administered intrathecally for regional

­Sea Turtle Fibropapilloma Surgical Excision Procedur ­Sea Turtle Fibropapilloma Surgical Excision Procedur

(a)

(b)

(c)

(d)

Figure 21.4  (a–d) Images of fibropapilloma tumors identified on laparoscopic exam of the coelomic cavity of a juvenile green sea turtle (Chelonia mydas). (a, b) Renal tumors. (c) Hepatic tumor. (d) Pulmonary tumors.

anesthesia for inguinal procedures (Mans 2014). Often times, local anesthesia (with or without sedation) is adequate for animals with a small number of minor tumors or posterior quadrant procedures. FP tumor burdens are quite variable, and frequently very extensive. To formulate surgical planning, all factors of intraoperative and postoperative patient morbidity must be considered, including hemorrhage, protein loss, anesthesia time, pain, and infection. In an effort to minimize anesthetic complications, a general rule of thumb is to limit anesthesia time to one hour. Tumors are prioritized based on size, location, and detriment to the patient. Periocular tumors that block vision, large tumors limiting swimming or resting behaviors, and necrotic and infected tumors are removed first. For extensive tumor burdens, surgical procedures are often divided into anatomical regions or quadrants (for example, all tumors from right inguinal region) (Figure 21.6).

The turtle should be prepped for surgery using standard aseptic surgical prep techniques, using either chlorhexidine or betadine scrub and alcohol. Povidone‐iodine 5% and saline are recommended for periocular procedures. Alcohol is highly flammable, and therefore a thorough final rinse is performed with saline to prevent ignition with the surgical laser. Efforts should be taken throughout surgery to maintain sterility and prevent cross‐contamination of surgery sites. Procedure

To begin, a circumferential incision is made through the dermis surrounding the tumor with an additional 1–2 cm margin of clean skin where anatomically possible (Figure  21.7a). Hand movements should be slow and steady using the maximum wattage with which the surgeon is comfortable (Table  21.2). The wattage must be powerful enough to cut full thickness in a single sweep

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Figure 21.5  Lidocaine is administered intrathecally for regional anesthesia. Using sterile technique, Lidocaine 2% (preservative‐ free) up to 4 mg/kg is administered into the subdural space between coccygeal vertebrae using a 25 or 27 g needle at a 45° angle (Mans 2014). Frequently, 2 mg/kg is effective, leaving additional lidocaine dosing for other SC local blocks.

Figure 21.6  Turtles with stage 2–3 FP tumor burdens will undergo multiple procedures for surgical excision to minimize complications and post‐operative morbidity. Surgeries are commonly divided into quadrants based on anatomic regions as shown.

(Video 21.1). If the wattage is too low, charring and repetitive cutting motions will cause increased collateral thermal tissue damage. If the wattage is too high, the laser will penetrate unintended deeper tissue layers. The thickness and toughness of sea turtle skin varies based on species, size, and anatomic location. The skin over the

flippers is toughest, but extreme care must still be taken to protect underlying muscle, tendons, nerves, vasculature, and bone, as there is minimal SC tissue (Video 21.2). Irrigating the incision with sterile saline while cutting and allowing brief periods of tissue rest between incisions can help decrease thermal damage. SuperPulse mode can also be used for this purpose. In the inguinal region, care must be taken to avoid carapace or plastron marginal bone and coelomic lining that is fairly superficial in certain areas, especially in thin turtles. For dermal incisions, 0.4 mm spot size at 14–18 W continuous wave non‐SuperPulse is commonly recommended. After the dermal incision is completed, the power setting is often decreased to 12–16 W continuous wave non‐SuperPulse for SC dissection underneath the tumor. The tumor and dermal margin are retracted upward, and the laser used to cut through SC tissue to dissect and peel away neoplastic tissue, maintaining perpendicular orientation to the cutting surface throughout (Figure  21.7b–c and Video 21.3). As the end of excision is approached, saline‐ soaked gauze is placed behind the cutting surface as a backstop to prevent trauma of underlying tissue or drapes (Figure 21.7d). Most dermal FP tumors are superficial and do not extend beyond the dermis (Video 21.4). However, some tumors (especially inguinal and shoulder tumors) can invade deeper tissues, requiring more extensive dissection. Most hemostasis is achieved with the laser, though larger more vascular tumors may require additional measures. Supplemental hemostasis can be achieved with radiocautery and ligatures. Studies have shown that poliglycaprone 25 (monocryl) and polyglyconate (maxon) sutures cause the least tissue reaction in sea turtle skin (Govett et al. 2004). Hemostasis with the CO2 laser is effective for vessels less than 0.5 mm diameter and in parallel orientation. Since some vessels originate from deeper tissues, they may initially be perpendicular and require tissue manipulation to reorient for effective hemostasis. Increasing the distance of the hand piece to 1–3 cm from tissue helps defocus the beam and increase coagulation. Once the tumor has been completely excised, the power is decreased to 10–12 W continuous wave, non‐SuperPulse mode and a 1.4 mm spot size used with a defocused beam (1–3 cm from tissue surface) for tissue contraction and additional hemostasis. The use of an adjustable handpiece simplifies the adjustment of spot size enormously, further reducing anesthesia time. The defocused beam is used in a spiral or painting motion, beginning centrally and working outward toward margins (Figure  21.7e). This helps to shrink the size of incision to facilitate healing, reduce infection, and seal off nerve endings, lymphatics and blood vessels. Incisions are left open to heal via second intention. Previous methods of suturing and grafting proved unsuccessful. Incisions are covered with a topical

­Sea Turtle Fibropapilloma Surgical Excision Procedur ­Sea Turtle Fibropapilloma Surgical Excision Procedur

(a)

(b)

(c)

(d)

(e) Figure 21.7  (a–e) Surgical excision of fibropapilloma tumor from the ventral front flipper of a juvenile green sea turtle (Chelonia mydas). (a) Circumferential incision through the dermis including tumor and additional 1–2 cm margin of normal skin. (b, c) The laser beam is oriented perpendicular to the cutting surface while the tissue margin is retracted upward for SC dissection underneath the tumor. (d) Saline‐soaked gauze is placed behind the tumor to protect underlying tissue and drapes during excision. This is particularly necessary for tumors along flipper margins, and during the final stages of any excision. (e) After excision, a defocused beam with Wide Ablation tip is used in a spiral motion for hemostasis and contraction of the incision.

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Table 21.2  General laser settings for fibropapillomatosis tumors. Procedure

General FP surgery

Laser type and wavelength (nm)

CO2 (10 600)

CO2 (10 600)

CO2 (10600)

Spot size (mm)

0.4

0.25–0.4

1.4

Power (W)

14–18

12–16

10–12

Exposure

Continuous wave

Continuous wave

Continuous wave (defocused)

Mode

Non‐Superpulse

Non‐Superpulse

Non‐Superpulse

Duty cycle (%)

100

100

100

hydrogel or collagen product for moistening and protection during recovery. The incisions are either bandaged or left open, depending on size, location, and hemorrhage (Figure  21.8). Incisions with continued concerns for hemorrhage are bandaged with a hemostatic agent for 12–48 hours as needed to control bleeding. Pressure bandages are placed using Vetwrap, Elasticon, or action‐ bandages (Figure 21.9). Video 21.1  Dermal incision using CO2 laser for fibropapilloma tumor excision from juvenile green sea turtle (Chelonia mydas) (This video does not include audio commentary.). A dermal incision is made using a 0.4 mm focal spot size at 16 W continuous wave exposure in non‐SuperPulse mode. The power is set such that a full thickness incision is made through the dermis in a single sweep, using slow and steady linear hand movements while maintaining traction along the incision. Video 21.2  CO2 laser excision of fibropapilloma tumor from the dorsal aspect of a front flipper of a juvenile green sea turtle (Chelonia mydas). (This video does not include audio commentary.) Prior to the start of this video, a circumferential full thickness dermal incision was made around the FP tumor and the adjacent 1 cm of normal skin using a 0.4 mm focal spot size and 12 W continuous wave exposure in SuperPulse mode. The video begins at the start of SC dissection. The laser is used to dissect through the tissue planes underneath the tumor and associated dermis. The focal spot is redirected to maintain a perpendicular orientation to the cutting surface. Traction is maintained on excised tissue to facilitate visualization and depth of tissue plane, and maintain control of the depth of the incision. There is minimal SC tissue in this location, so extreme care must be taken to avoid cutting underlying musculature, nerves, tendons, and bones unless associated with the tumor. Video 21.3  CO2 laser SC dissection during excision of a large cluster of fibropapilloma tumors in the inguinal fossa and from a proximal rear flipper of a juvenile green sea turtle (Chelonia mydas) (This video does not include audio commentary.). Prior to the start of the video, a circumferential full thickness dermal incision was made around the region of FP tumors to be excised (depicted in Video 21.1). SC dissection is performed using a 0.4 mm focal spot size at 14 W continuous wave exposure in non‐SuperPulse mode. The laser orientation is adjusted throughout surgery to maintain perpendicular orientation to the cutting surface. Traction is maintained on tissue to allow visualization and accurate control

of tissue depth. The surgery is performed from superficial areas to deeper regions, constantly moving around the tumor pedicle to ensure maintenance of the desired tissue plane. If the surgeon continues in same region without equalizing the depth in other regions, they will inadvertently remove viable deeper layers of tissue. There is some hemorrhage noted from the transection of a deeper vessel in the SC adipose tissue. Not shown in the video is hemostasis provided with hemostats and ligature placement. Shortly thereafter, a small vessel was transected, and the laser beam was defocused and directed parallel to the surface of the vessel for hemostasis. Throughout the video, you can see the separation of SC adipose tissue and fascial planes from the deeper musculature during the careful dissection around the flipper. Maintaining this control of depth is crucial throughout the procedure. Video 21.4  CO2 laser excision of a large cluster of fibropapilloma tumors from the left ventral shoulder region of a juvenile green sea turtle (Chelonia mydas) (This video does not include audio commentary.). Highlights of a surgical excision of a large cluster of FP tumors from the left ventral shoulder region of a juvenile Green Sea Turtle. Dermal incisions, SC dissection, and maintaining adequate depth control are all depicted.

Considerations for Periocular FP Tumors The effects of the CO2 laser on deeper structures of the eyes of turtles has not been well studied. Therefore, it is unknown if there are negative impacts from laser use on and around periocular structures in sea turtles, including the scleral ossicles. Many surgeons find the laser more challenging and less precise for ocular procedures due to the viscous tear film production. However, some surgeons do utilize the laser in these regions. A water‐based ophthalmic lubricant should be utilized to protect the cornea during these procedures, as petroleum‐based lubricants may ignite under the laser. Procedure: Scleral Tumors

The technique for excision of scleral tumors is similar to that of dermal tumors, with some minor adjustments. The cornea should be protected with saline‐ soaked gauze or ophthalmic ointment to prevent collateral damage. Using a 0.25 mm spot size, 7–8 W, a repeat pulse exposure in SuperPulse mode, pulsing

­Sea Turtle Fibropapilloma Surgical Excision Procedur ­Sea Turtle Fibropapilloma Surgical Excision Procedur

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(b)

(c)

(d)

(e) Figure 21.8  (a–e) Examples of surgical sites immediately following excision of fibropapilloma tumors from a juvenile green sea turtle (Chelonia mydas). (a, b) Small excision sites without concerns of hemorrhage that do not require bandaging. (c–e) Larger excision sites with concerns for hemorrhage; these should be bandaged for 24–72 hours postoperatively.

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10 ms at 20 Hz, 20% power (Table  21.3), the tumor is dissected off the surface of the globe using lateral retraction in a “peeling motion” (Video 21.5). Rather than making a circumferential incision, the incision is started at one end of the tumor (usually the ventral aspect) and dissection is then continued circumferentially, gradually working around all margins of the tumor while carefully maintaining appropriate depth

(Figure 21.10). Care is taken to maintain a perpendicular orientation of the laser tip to the cutting surface during dissection. Extreme caution must be used when incising the anterior portion of the tumor, as it is often along the corneal margin. If tumors involve the cornea (Figure 21.11), a scalpel blade is used to perform a partial keratectomy in that region. If the tumor involves a full‐thickness penetration of the corneal tissue, an enucleation is performed. After excision, a 0.25– 0.4 mm spot size at 2–4 W continuous wave SuperPulse defocused beam can be used for focal ablation and hemostasis as necessary (Figure 21.10e). The conjunctival defect is left open to heal by second intention. Some surgeons still prefer using a conventional blade and iris scissors for the excision of scleral tumors (Video 21.6). Video 21.5  Surgical excision of scleral fibropapilloma tumor from a juvenile green sea turtle (Chelonia mydas) using CO2 laser (This video does not include audio commentary.) The eyelids are retracted open by an ophthalmic speculum to aid in visualization during the procedure. Using a 0.25 mm focal spot size and 7 W repeat pulse exposure in SuperPulse mode (pulsing at 10 ms, 20 Hz, 20% power), the tumor is dissected off the surface of the sclera using lateral retraction in a peeling motion. The incision is started along the ventral aspect of tumor and continued in a lateral direction circumferentially around the tumor, maintaining appropriate depth along the surface of the globe. Note how the surface of the cornea and the deeper structures of the eye are protected with saline soaked gauze. Ophthalmic ointment can also be used. Once the tumor has been completely excised, the focusing tip is distanced from the cutting surface to defocus the laser beam for surface ablation and hemostasis.

(a)

(b) Figure 21.9  (a, b) Examples of bandages placed to protect incisions and control hemorrhage post‐operatively for larger incisions in inguinal, shoulder, and flipper regions. Bandage layers most commonly consist of: hemostatic agent, hydrogel, nonadherent pad, gauze pads, and Vetwrap.

Video 21.6  Surgical excision of scleral fibropapilloma tumor from a juvenile green sea turtle (Chelonia mydas) using steel instruments (This video does not include audio commentary.). An incision is made through the conjunctiva along the lateral aspect of the scleral tumor using iris scissors. Dissection continues along the surface of the globe circumferentially around the tumor using iris scissors and a beaver scalpel blade.

Table 21.3  Laser settings for periocular fibropapillomatosis tumors. Procedure

Periocular FP tumors

Laser type and wavelength (nm)

CO2 (10 600)

CO2 (10 600)

CO2 (10 600)

Spot size (mm)

0.25

0.4

0.25

Power (W)

7–8

2–4

10

Exposure

Repeat pulse

Continuous wave (defocused)

Continuous wave

Mode

Superpulse

Non‐Superpulse

Non‐Superpulse

Frequency (Hz)

20 Hz, 10 ms

—

—

Duty cycle (%)

20

100

100

­Sea Turtle Fibropapilloma Surgical Excision Procedur ­Sea Turtle Fibropapilloma Surgical Excision Procedur

(a)

(b)

(c)

(d)

(e) Figure 21.10  (a–e) Excision of a scleral tumor from the left eye of a juvenile green sea turtle (Chelonia mydas) using a CO2 laser. (a) Common appearance of scleral and conjunctival/nictitating membrane fibropapilloma tumors. (b–d) The cornea is protected using saline‐soaked gauze. An incision is made through the conjunctiva along the ventral aspect of the tumor, including 3–5 mm of healthy conjunctiva for margins. The tumor is retracted laterally and dissection is continued around and underneath the tumor, carefully following the surface of the globe to control depth. (e) After excision, the tip is distanced from the cutting surface to defocus the beam for ablation and hemostasis of the globe surface and remaining conjunctiva.

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(a)

Figure 21.11  Juvenile green sea turtle (Chelonia mydas) with corneal fibropapilloma, requiring partial keratectomy.

Procedure: Eyelid and Conjunctival Tumors

For eyelid tumors, care is taken to preserve as much of the dermal eyelid margin as possible. Most of the time, the tumors originate from the conjunctival surface, and do not actively infiltrate the margin (Figure 21.12a). However, tumors that originate from or infiltrate the dermal aspect of the eyelids require resection of that region (Figure 21.13). The cornea is covered in ophthalmic ointment for protection. Saline‐soaked gauze is placed over the ointment to create a safe cutting surface. The tumor and associated eyelid or conjunctiva are retracted over the saline‐soaked gauze. A 0.25 mm focal spot size at 10 W continuous wave SuperPulse mode is used to make a linear, full thickness incision 1–3 mm proximal to the tumor base for excision (Figure  21.14a–b and Video 21.7). For conjunctival tumors on the medial eyelids, the same settings are used to dissect the conjunctiva from the dermal layer of the eyelid for excision. The conjunctival defect is left open to heal by second intention (Figure  21.14c). Some surgeons still prefer using a conventional scalpel blade and iris scissors for excision of conjunctival tumors (Figures 21.12b,c and 21.15a–c). If upper eyelid conjunctival tumors are removed in conjunction with scleral tumors, there is a risk of adhesions forming that may restrict the movement of upper eyelid, inhibiting closure over the cornea after healing. To facilitate healing in a more functional manner, a temporary tarsorrhaphy is often necessary for the first 7–10 days postop.

(b)

(c) Figure 21.12  (a) Juvenile green sea turtle (Chelonia mydas) with common scleral and conjunctival fibropapilloma tumors. (b, c) Excision of scleral tumors using conventional scalpel blade. The tumor is retracted laterally. A full thickness conjunctival incision is made along the limbus and continued along the surface of the globe, peeling away the tumor.

­Sea Turtle Fibropapilloma Surgical Excision Procedur ­Sea Turtle Fibropapilloma Surgical Excision Procedur

(a) Figure 21.13  A juvenile green sea turtle (Chelonia mydas) with fibropapilloma tumors originating from sclera and dermal surface of the ventral eyelid.

Video 21.7  Surgical excision of fibropapilloma tumor from corner of eyelids of a juvenile green sea turtle (Chelonia mydas) using CO 2 laser (This video does not include audio commentary.). Saline soaked gauze is used to protect the cornea and nearby tissues from the surgical laser. A 0.25 mm focal spot size at 10 W continuous wave SuperPulse mode setting is used. The tumor is retracted, allowing an incision to be made full thickness through the dermis and conjunctiva immediately adjacent to the tumor. Saline soaked gauze is placed underneath the tumor to provide a safe cutting surface for the final transection of medial tissue. The tip is then distanced from the cutting surface for ablation and hemostasis.

(b)

Considerations for Tumors Near Bone In many other species and their anatomical regions, the density and depth of soft tissues is such that the power of the laser can be precisely controlled to minimize collateral thermal damage beyond a few cell layers. Sea turtle anatomy differs, however, and there are several regions where the very thick epidermal tissue of these animals is directly associated with underlying bone. The power required to cut through the tissue generates collateral thermal energy that is transferred into the surrounding bone. This thermal energy has been demonstrated to vary in severity based on power and exposure time. The damage to outermost bone is mild, showing carbonized tissue. However, as laser surgery continues to approach this contact region, the tissue exhibits more pronounced zones of thermal necrosis and damage. These effects have caused focal

(c) Figure 21.14  (a, b) Surgical excision of a small fibropapilloma tumor from the margin of the nictitating membrane (third eyelid) of a juvenile Green sea turtle (Chelonia mydas) using CO2 laser. The cornea is protected with saline soaked gauze. The nictitating membrane is retracted over the saline soaked gauze. A full thickness incision is made through the third eyelid 3 mm proximal to the tumor margin for excision. (c) Postoperative photo following excision of the tumor from the margin of nictitating membrane. A tumor was also removed from the sclera (see Figure 21.10) exposing the scleral ossicle.

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Table 21.4  Laser settings for FP tumors near bone. Procedure

Laser type and wavelength (nm)

(a)

FP tumors near bone

CO2 (10 600)

CO2 (10 600)

Spot size (mm)

0.25–0.4

0.4–0.8

Power (W)

12–14

10–12

Exposure

Continuous wave

Continuous wave (defocused)

Mode

SuperPulse

Non‐SuperPulse

Duty cycle (%)

100

100

infarcts and abscesses within the underlying bone (Rayan et al. 1992; Krause et al. 1997). Therefore, the laser can be used cautiously for the initial approach to tumor resection around bone, but then conventional blade and steel instruments are used to complete the procedure (Table 21.4). Procedure

(b)

(c) Figure 21.15  (a–c) Excision of upper eyelid conjunctival fibropapilloma tumors from a juvenile green sea turtle (Chelonia mydas) using conventional steel instruments. (a) The tumor and conjunctiva are retracted laterally. (b) The incision is started along the dermal margin of the eyelid, preserving as much of the eyelid margin as possible. The excision is extended along the conjunctival surface until only normal conjunctival tissue is present, denoting complete excision. (c) Photo of conjunctival incision site after complete excision.

Radiographs with or without CT are performed prior to surgery to identify and evaluate the extent of boney involvement for surgical planning. Small tumors in earlier stages of growth can be hidden underneath the keratin and are not easily identified on physical exam alone. However, bone destruction is visible on CT (Figure 21.16). For tumors on the plastron, carapace, or face, the CO2 laser is used initially to cut through keratin and superficial epithelial tissue. A circumferential incision is made around the tumor including 1 cm margins beyond lytic area of bone as anatomically able, using a 0.25–0.4 mm spot size and 12–14 W continuous wave in SuperPulse mode (Figure 21.17a). From there, a #11 scalpel blade is used to deepen the incision to the level of bone. The scalpel blade or a sharp periosteal elevator is used to continue sharp dissection around and underneath the tumor for excision (Figure  21.17b). Once the tumor and surrounding epithelial tissue has been removed, the affected bone margins are excised using curettes, rongeurs, or bone saw as needed. Care must be taken to avoid damaging the coelomic lining. A defocused laser beam, at 0.4–0.8 mm spot size and 10–12 W continuous wave in non‐SuperPulse mode can be used for hemostasis as needed at the end of the procedure, although this will not be effective for cortical bleeding (Figure 21.17c). These areas are then packed with

­Sea Turtle Fibropapilloma Surgical Excision Procedur ­Sea Turtle Fibropapilloma Surgical Excision Procedur

(a)

(b)

(c)

(d)

Figure 21.16  (a–d) CT scans are utilized to identify bony involvement of FP tumors on the carapace and plastron. Margins of the affected bone must be debrided during tumor excision to prevent recurrence. (b, d) Image of 3D reconstruction of CT demonstrating lysis of bony carapace deep to external fibropapilloma tumors. There was previous trauma to the left posterior bridge of the carapace. There are two FP tumors on the right anterior bridge of the carapace also demonstrating associated bone lysis, not adequately visible on this image. (a, c) Photo of carapace of the same turtle showing gross appearance of the lytic lesions identified on CT. Note that the anterior lesion does not have a visible external tumor. There is only a discoloration of keratin. The tumor was visible after keratin was removed from that area.

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(a) (a)

(b) (b)

(c) Figure 21.17  (a–c) Excision of FP tumors in regions with underlying bone (carapace, plastron, skull) require a combination of laser for initial approach and a conventional blade to prevent excessive collateral thermal damage and abscessation of the surrounding bone. (a) The laser is used to make a circumferential incision through keratin and epithelium. (b) #11 scalpel blade being used to sharply dissect the tumor and associated soft tissue from underlying bone. (c) A defocused laser beam and wide ablation tip is used along the margins of the incision and soft tissues for hemostasis.

(c) Figure 21.18  (a) Postoperative excision site of a fibropapilloma tumor removal on the plastron of a juvenile Green sea turtle (Chelonia mydas). (b) Incision packed with hemostatic agent to control hemorrhage postoperatively. (c) The incision covered in bone cement for protection during initial stages of healing.

­Prognosis and Conclusio ­Prognosis and Conclusio

hemostatic agents and pressure bandaged. Incisions that are completely surrounded by bone can be packed with honeycomb, dental wax, or may covered in bone cement to help create pressure within the incision (Figure 21.18). Postoperative Care Recovery times allotted between surgical procedures vary based on the individual animal but are typically about two to four weeks. Postoperative care is similar to that of most species but also quite unique when caring for sea turtles due to the aquatic environment and stress. Primary factors that must be addressed include controlling hemorrhage, controlling pain, preventing infection, minimizing stress, and encouraging healing. In debilitated patients, this also includes managing other comorbidities such as anemia, emaciation, pneumonia, and other conditions. Postoperative hemorrhage is most critical during the initial 24‐hour period following ­surgery. Although hemorrhage can be well controlled intraoperatively, it may increase during recovery as blood pressure normalizes and the turtle becomes active, sometimes traumatizing the area. If bleeding is severe, additional radiocautery or ligature placement may be necessary. Most of the time, pressure bandages with hemostatic agents are effective, but these may need to be changed every few hours until controlled. Once the hemorrhage has stopped, a clean nonadherent bandage is left in place for 24–48 hours to prevent recurrence. Turtles are returned to the water as soon as possible based on recovery (Figure  21.19). Average times range from 3 to 24 hours postop, depending upon anesthetic recovery and postoperative bleeding. Bandages can remain in place while in water, as long as they do not prohibit swimming and surfacing. The water depth is adjusted to accommodate the turtle’s strength, pain, and abilities postop. Analgesics, most commonly meloxicam and tramadol, are administered for one to four weeks, depending upon the size and location of incisions (Norton et al. 2017). Infection risk is high after FP tumor excision due to open incisions and the aquatic environment. Good water quality is imperative during wound healing. Broad spectrum antibiotics are administered during healing for prophylaxis. Wound cleaning and topical wound care is provided during the initial 24–48 hours postop, then continued every 72 hours for the first two to three weeks, then once weekly until healed. Wounds are cleaned with dilute betadine or chlorhexidine and

saline, and loose caseous scab material is gently debrided once granulation has begun. Topical colloidal silver or zinc spray followed by hydrogel or collagen spray is applied. Topical antibiotic ointments are discouraged unless infection is present due to the risk of antibiotic resistance. The exception is for ocular incisions; triple antibiotic ophthalmic ointment is applied for three to seven days postop. Wound healing occurs quickly over several weeks (Figure 21.20). At our sea turtle rehabilitation facilities, therapeutic laser treatments (Class IV 12 W) are performed during the initial postop period to help control pain and inflammation (Figure 21.21). While overall healing time may not be altered (Kurach et al. 2015), decreased redness, swelling, and pain have been consistently observed during the acute healing phase. Laser therapy is performed every 72 hours with prescribed wound care during the initial two to three weeks postop. Beneficial effects of the laser are present with treatments as frequent as every 24–36  hours, but they are not significant enough to warrant the stress of additional animal handling for sea turtles.

­Prognosis and Conclusion Sea turtles heal quickly from dermal FP excisions, and once tumors are completely removed, they can successfully be released under the guidance of regulatory authorities. However, recurrence of FP tumors is common. Up to 60% of tumors regrow postoperatively (Page‐ Karjian et  al. 2014). Animals need to be monitored closely postop for development of new tumors and regrowth (Figure  21.22). When regrowth occurs, it is typically noted within 36 days of surgery (Page‐Karjian et al. 2014). The risk factors of regrowth, as with initial tumor development, are multifactorial and not completely known. As with all herpesviruses, stress and immunosuppression are likely critical factors. It is also dependent upon surgical margins, tumor stages, tumor aggression, internal tumors, and other unknown factors. Recurrent tumors are excised with the same techniques as previously described. If animals have extensive regrowth, additional or repeat diagnostics should be performed to screen for internal FP tumors. Recent genomic studies indicate that FP tumors share molecular characteristics with human basal cell carcinoma (Duffy et al. 2018). There are a number of effective therapies for treating basal cell carcinoma, including the topical application of fluorouracil (5‐FU)

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(a)

(b)

(c)

(d)

(e) Figure 21.19  (a–e) Juvenile green sea turtles (Chelonia mydas) in various depths of water with multiple types of bandages in place during the initial 4–36‐hour postoperative period following excision of fibropapilloma tumors.

­Prognosis and Conclusio ­Prognosis and Conclusio

(a)

(c)

(c)

(b)

(d)

Figure 21.20  (a–h) A series of photographs taken of a juvenile green sea turtle (Chelonia mydas) following the progression of healing after fibropapilloma tumor excisions. (a) Preoperative tumors present in the left inguinal fossa and peri‐cloaca. (b) Immediate postoperative excision from the left inguinal quadrant: exposed muscle and SC tissue present. No closure performed. (c) Two weeks postoperative: caseous scab material is completely covering all incisions, beginning to thicken as a protective layer while granulation tissue begins to form. (d) Four weeks postoperative: thick, healthy caseous scab material tightly adhered to underlying granulation bed. The margins are loosening and beginning to peel away as epithelialization begins. The smaller, more superficial anterior incision is fully epithelialized at this stage. (e) Six weeks postoperative: caseous scab material continues to loosen and peel away as epithelialization progresses. (f ) Eight weeks postoperative: the remaining granulation bed and caseous scab material are very superficial, with continued wound contraction and epithelialization. (g) Ten weeks postoperative: remaining caseous scab material ready to slough to allow epithelialization of remaining central area. (h) Incisional scar tissue fully healed prior to release.

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(e)

(f)

(g)

(h)

Figure 21.20  (Continued)

Figure 21.21  A juvenile Green sea turtle (Chelonia mydas) receiving laser therapy on incisions following fibropapilloma tumor excisions. Treatments are performed immediately postop, then repeated every 72 hours for two–three weeks to help control pain and inflammation.

Figure 21.22  A juvenile green sea turtle (Chelonia mydas) with fibropapilloma tumor regrowth noted within scar tissue of a previous surgical excision site on the left inguinal quadrant. A large cluster of FP tumors is visible adjacent to the right inguinal quadrant.

­Reference ­Reference

onto affected skin regions (Duffy et al. 2018). A 5‐FU treatment has been used experimentally as 1% ophthalmic solution, applied topically twice daily for six to eight weeks into the eyes (with a 15 minute “dry dock” time for the turtle to allow for sufficient contact). Initial studies have shown a decrease in recurrence of up to 50% with this treatment (Duffy et al. 2018). It has also been used topically on areas of skin of early regrowth or boney regions postop to prevent recurrence. There is some evidence that it is effective in treatment or prevention, and further research is currently being done to find other chemotherapeutics for FP tumors. Until more advancements are made in the understanding of the disease and treatment options, surgical excision with CO2 laser remains the treatment of choice for fibropapillomatosis.

The CO2 laser has many other applications in sea turtles and other aquatic animal species. It is commonly used to assist in flipper amputations. Similar settings for such procedures are used as described above for dermal FP excision procedures. Vessels larger than 0.5 mm diameter require ligation. The bone is disarticulated at the joint, or cut with giggly wire or rongeurs, depending on the location of the amputation. Surgical lasers are also commonly used for esophagostomies for fish hook removals and esophagostomy tube placement. They can also be used for enucleations, abscess lancing, and other soft tissue surgeries. Based upon the surgeon’s comfort and skill level, CO2 lasers have a wide variety of practicalities for soft tissue ­surgeries in aquatic species.

­References Aguirre AA, Lutz PL. (2004). Marine turtles as sentinels of ecosystem health: is fibropapillomatosis an indicator? Ecohealth. 1. pp. 275–283. Alfaro‐Nunez A, Bertelsen MF, Bojesen AM, et al. (2014). Global distribution of chelonid fibropapilloma‐associated herpesvirus among clinically healthy sea turtles. BMC Evol. Biol. 14. pp. 206–217. Croft LA, Graham JP, Schaf SA, et al. (2004). Evaluation of magnetic resonance imaging for detection of internal tumors in green turtles with cutaneous fibropapillomatosis. J. Am. Vet. Med. Assoc. 225(9). pp. 1428–1435. Duffy DJ, Schnitzler C, Karpinski L, et al. (2018). Sea turtle fibropapilloma tumors share genomic drivers and therapeutic vulnerabilities with human cancers. Commun. Biol. 1(1). p. 63. Govett P, Harms CA, Linder KE, et al. (2004). Effect of four different suture materials on the surgical wound healing of loggerhead sea turtles (Caretta caretta). J. Herpetol. Med. Surg. 14(4). pp. 6–11. Herbst LH. (1994). Fibropapillomatosis of marine turtles. Annu. Rev. Fish Dis. 4. pp. 389–425. Herbst LH, Lemaire S, Ene AR, et al. (2008). Use of baculovirus‐expressed glycoprotein H in an enzyme linked immunosorbent assay developed to assess exposure to chelonid fibropapillomatosis‐associated herpesvirus and its relationship to the prevalence of fibropapillomatosis in sea turtles. Clin. Vaccine Immunol. 15. pp. 843–851. Hirama S, Ehrhart LM. (2007). Description, prevalence, and severity of green turtle fibropapillomatosis in three

developmental habitats on the east coast of Florida. Fla. Sci. 70. pp. 435–448. Krause LS, Cobb CM, Rapley JW, et al. (1997). Laser irradiation of bone. I. An in vitro study concerning the effects of the CO 2 laser on oral mucosa and subjacent bone. J. Periodontal. 68(9). pp. 872–880. Kurach LM, Stanley BJ, Gazzola KM, et al. (2015). The effect of low‐level laser therapy on the healing of open wounds in dogs. Vet. Surg. 44(8). pp. 988–996. Lanzafame RJ, McCormack CJ, Rogers DW, et al. (1988a). Mechanisms of reduction of tumor recurrence with carbon dioxide laser in experimental mammary tumors. Surg. Gynecol. Obstet. 167(6). pp. 493–496. Lanzafame RJ, Qiu K, Rogers DW, et al. (1988b). Comparison of local tumor recurrence following excision with the CO2 laser, Nd:YAG laser, and Argon Beam Coagulator. Lasers Surg. Med. 8(5). pp. 515–520. Mader DR. (2006). Medical care of sea turtles: medicine and surgery. In: Mader DR, ed. Reptile Medicine and Surgery, 2nd ed. St. Louis, MO: Saunders, Elsevier. pp. 997–1000. Mans C. (2014). Intrathecal drug administration in turtles and tortoises. J. Exotic Pet Med. 23(1). pp. 67–70 Norton TM, Mosley CI, Sladky KK, et al. (2017). Analgesia and anesthesia. In: Manire CA, Norton TM, Stacy BA, et al. Sea Turtle Health & Rehabilitation. Plantation, FL: J. Ross Publishing. pp. 527–550. Page‐Karjian A, Torres F, Zhang J, et al. (2012). Presence of chelonid fibropapilloma‐associated herpesvirus in

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tumored and non‐tumored green turtles, as detected by polymerase chain reaction, in endemic and non‐endemic aggregations, Puerto Rico. Springer Plus. 1. p. 35. Page‐Karjian A, Norton TM, Krimer P, et al. (2014). Factors influencing survivorship of rehabilitating green sea turtles (Chelonia mydas) with fibropapillomatosis. J. Zoo Wildl. Med. 45(3). pp. 507–519.

Rayan GM, Stanfield DT, Cahill S, et al. (1992). Effects of rapid pulsed CO2 laser beam on cortical bone in vivo. Lasers Surg. Med. 12(6). pp. 615–620. Work TM, Balazs GH. (1999). Relating tumor score to hematology in green turtles with fibropapillomatosis. J. Wildl. Dis. 35. pp. 804–807.

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Part V Integrating Surgical Lasers in Your Veterinary Practice

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22 Tips and Tricks for Veterinary Laser Surgeons Les “Laser Les” Lattin

­Introduction I was actively involved in wet labs where many tissue models and techniques were discussed and developed, and I have had the opportunity to observe thousands of carbon dioxide (CO2) laser surgeries performed by many veterinary specialties over the past 28 years. In this chapter is information I have learned in that time from some of the most skilled CO2 laser surgeons in veterinary medicine.

­Intraoperative Recommendations Operating the Laser While Maintaining Sterility To maintain sterility when changing the settings on the panel of the laser, autoclave several syringe plungers and keep them in each of your sterile packs (Figure 22.1). The rubberized end can push buttons on the laser panel without damage. Keep the top of the plunger sterile by putting the plunger in a designated receptacle on the side of the laser (Figure 22.2). A 6″–12″ long piece of 1″ diameter polyvinyl chloride (PVC) pipe (purchased at any hardware store) can also be autoclaved in your pack (Figure  22.3). The surgeon can place this PVC pipe over the smoke evacuator nozzle (Figure  22.4) usually held by a stand or assistant (Figure 22.5). Now, if the pipe touches the surgeon, there is no contamination, and it can be adjusted by the surgeon to obtain maximum removal of any plume that is produced.

an important consideration with delicate surgeries (e.g. thyroidectomies, vaginal surgery, cherry eye, and entropion) where the tissue is thin, and air movement could enter the tissue to cause embolism. For such procedures, reducing or disconnecting this airflow will prevent such an occurrence. Regarding Char Char is a normal by‐product of laser use. Char remains following photovaporization, and its removal is extremely important, unless otherwise specifically directed in a given procedure in this text. If you attempt to cut through char, the laser beam will hit the char instead of your ­target, creating heat in the adjacent tissue, which could result in swelling and thermal injury. If the heat is excessive, dehiscence could occur. Remove char by using sterile moistened nonwoven gauze sponges to gently wipe while using slight downward pressure with a slight twist. A sterile‐moistened cotton‐ tipped applicator will also remove char in this instance. Char can be beneficial for distichia surgery. Leaving char in place permits the surgeon to hit the char in single pulse exposure and create lateral heat, which assists in ablating the hair follicle. The hair should not be inserted into the tip of the handpiece during the procedure because ablation of hair within the tip can cause deposition of char on the interior reflective surface, compromising power density and distribution of the laser beam. It is also generally recommended not to remove char from the site of soft palate resection to reduce risk of hemorrhage. Backstops

Preventing Air Embolism In a CO2 laser, air is flushed through the delivery system to keep any surgical smoke plume from entering. This air runs for about two seconds after the laser stops. This is

A sterile‐moistened gauze sponge can be used when performing laser surgery to act as a barrier against the laser beam. Place this sterile saline‐ or water‐soaked nonwoven gauze sponge behind tissue that you are lasing. Once

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

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Figure 22.3  A 12″ section of autoclaved PVC pipe.

Figure 22.1  Plunger and receptacle.

Figure 22.4  Smoke evacuator hose with mess before PVC pipe added.

Figure 22.2  Receptacle mounted on laser with sterile plunger.

Figure 22.5  Smoke evacuator after PVC added.

­Maintenance Recommendation

the beam cuts through this tissue, the soaked sponge will absorb the beam, preventing reflection and collateral damage. A laser directed on moistened gauze may not yield any initial result because the moisture absorbs the laser energy. A little smoke as the moisture is vaporized is a good visual cue to either move the beam away from that spot or deactivate the laser and remoisten the gauze. A nonwoven gauze sponge is recommended with laser use because there are no gaps in the weave of the sponge, leaving no opening for the laser beam to pass through. A well‐moistened nonwoven gauze sponge works well in the oral cavity to protect endotracheal tubes from inadvertent direct or indirect laser beam contact, helping to prevent damage to the tube and catastrophic combustion of anesthetic gases. In soft‐palate surgery, the same sponge can protect tissues behind the soft palate. Another use of the moistened nonwoven gauze sponge is for growth removal. Fold the gauze over to cut a fenestration in the center, then open and drape it to surround the growth (Figure 22.6). The gauze should stay in place as tension is placed on the growth using forceps in any direction, to ablate the growth while protecting surrounding healthy tissue. A groove director (Figure  22.7) is very useful for approach to the ventral midline. Use it to raise up the linea, applying tension so that the CO2 laser beam can be directed toward the groove director, cutting efficiently while protecting underlying tissue. Angle the groove director to keep the beam from reflecting upward toward the surgeon or other operating personnel.

Figure 22.7  Groove director.

Petrolatum‐based lubes are flammable. When performing laser surgery around the eyes, only aqueous water‐soluble lube should be used as a moistening agent. When working in the oral cavity, use lubricating water‐ soluble jelly on the teeth to provide an immediate barrier of protection from an inadvertent laser pass. Be sure to reapply as often as needed. When working in the ear canal, water or saline can be added below growths targeted for removal in the canal, to protect structures behind the growth. Visualization Accurate removal of diseased tissue is highly dependent on your ability to see what you are doing. Magnification loupes add greatly to your visualization of your surgical site and may make all the difference in spotting details important to your procedure. A light on the loupe will also add further detail where the overhead theater lights may not be able to reach.

­Maintenance Recommendations Laser Delivery System Calibration and Care

Figure 22.6  Fenestration in nonwoven gauze sponge.

Different delivery systems and handpieces may vary in their delivery of power to tissue from that shown on the laser panel. For consistent results, the surgeon should test each to ensure every surgery would have adequate power to achieve the goal of the procedure, including testing midprocedure during the changing of handpieces. For the hollow waveguide (HWG) delivery system of the CO2 laser, a routine calibration before each procedure will check the percent transmission of the laser beam through the waveguide. Following calibration, the surgeon can adjust the laser’s software to deliver the desired wattage accurately based on the HWG transmission being used for surgery. An HWG should not be bent or kinked and should have a gentle curve not to exceed the two ends being parallel to each other. To facilitate this shape, the laser should be positioned at the surgeon’s side or close by across the table. If the laser is too far away, the surgeon may tend to bend the fiber close to the handpiece, ­putting excessive stress on the end of the HWG. Repeated

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e­xcessive stress of this kind will otherwise cause the waveguide to develop memory and result in a decrease in power transmission over time. Too sharp a bend or kink will result in inadequate or zero transmission of the laser beam through the HWG and require replacement. Care should be taken with articulated arm delivery systems that they are not jarred, knocked around, or dropped during and between procedures. The mirrors within the arm may be knocked out of alignment in such instances, requiring return to the manufacturer for maintenance and realignment. If the targeting beam of an articulated arm system does not match the laser beam itself, then the unit should be removed from use immediately for expert maintenance. A dramatic decrease in power could be due to a loss of carbon dioxide gas in the resonator. Over time, the O‐ rings that contain the gas in the resonator could begin to shrink, resulting in CO2 leakage and loss of power. This is rare, but such instances would require maintenance by the manufacturer. Some CO2 laser models may have a SELF TEST feature to help diagnose a resonator leakage, and inquiry should be made to the manufacturer on how to do so.

Figure 22.8  Repurposed needle container before tips inserted.

Laser Tips and Handpieces Following the surgery, handpieces and tips can be cleaned with enzymatic or ultrasonic cleaner. The interior of the tip should not be scratched, or the integrity of the beam may be affected. A soft product like Ethilon or braided suture material can be used to clean the inner surface. When using a CO2 laser that uses ceramic tips, direct contact between the tissue and the tip can occlude the tip. The outer portion of the tip may appear dark due to cellular residue. To remove this residue, use wet–dry sandpaper of 200 grit or finer. Cut a small 1″‐square from the sheet. Fold this small piece of sandpaper and place the ceramic tip inside this folded square. Gently twist the tip in the sandpaper, and it will remove any char on the tip. If the surgeon should see a glow at the distal end of the tip during surgery, the tip should be replaced. Ceramic tips should never be cold soaked as ceramic can retain moisture; such tips could crack from the laser’s heat. To prevent this, steam autoclave tips prior to surgery to remove moisture. Because ceramic tips are small and hard to handle, a strainer basket, such as that used for tea leaves, can contain tips before placing the basket in the ultrasonic cleaner. This is a quick and easy way to clean them without misplacing them. A can of compressed air can be used to help unclog debris from inside tips and handpieces. To test tips for occlusion prior to surgery, the laser should be fired at a tongue depressor at 10 W, single

Figure 22.9  Repurposed needle container after tips inserted, ready for autoclave.

burst, 100 ms. Hold the tip about 1 mm off and perpendicular to the tongue depressor to produce a charred circle. If there is an area within the charred circle that appears untouched, this may indicate debris inside the tip, requiring a replacement tip and recalibration. Repeat the test with each new tip. A half‐circle on the char may be indicative of a kinked HWG. Small laser tips can be autoclaved in repurposed ­needle containers (Figure 22.8). A color code system can be used so that a certain spot‐size tip is matched to a needle container of a specific color. Put the cleaned tip in the container, and use autoclave tape around the cap. Autoclave with your packs or separately (Figure 22.9).

­Practic

Most CO2 laser handpieces can be cleaned like any surgical instrument. Enzymatic or ultrasonic cleaner can be used on stainless units without a lens prior to autoclaving. The lens portion of a CO2 surgical laser must never be autoclaved to avoid damaging the lens. Contact your laser manufacturer for information on keeping the lens of your laser clean.

­Practice Items such as tongue depressors, raw chicken, and eggs may be used to practice technique. Tongue depressors help to give excellent examples of different exposure and mode settings (continuous wave (CW), repeat pulse (RP), single pulse, and SuperPulse) of your CO2 laser and also assist in checking the integrity of ceramic tips. Practice on tongue depressors at different power settings, exposures, modes, and hand speeds to produce different effects on these objects and observe the results you would like to obtain in your procedures.

A tomato is also ideal for practice on organic material, as its water content can simulate skin. The use of the 0.8‐mm spot size allows better visualization of the results. Applying laser energy to a tomato stem will demonstrate sparking prior to a procedure. The lack of water here is comparable to hitting char or hard tissue such as teeth and bone. At 10 W, CW, an incision at slow speed will produce sparking because of the beam’s striking char. Increase the hand speed to reduce or eliminate this. A fast hand speed may produce little effect on the tomato’s surface due to inadequate time of exposure. A focused beam applied close to a tomato or tongue depressor produces a small spot and good depth. Backing the handpiece away from the tomato will increase the spot size with an exponential decrease in power. Observing these techniques helps to demonstrate the discussions of power density and fluence discussed in previous chapters, and with practice and observation, technique will improve. I hope some of these ideas learned from other laser surgeons can make your laser use more efficient and enjoyable.

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23 Pain Management in Laser Surgery Procedures1 Noel Berger

­Introduction Consumers of veterinary medical and surgical services continue growing the strength of the human–animal bond. It is not unusual at all to have companion animals accompany their owners in restaurants, hotels, libraries, office buildings, medical doctors’ offices, and schools. We are increasingly reminded that pet owners are referred to as persons in need of animal therapy services or even pet parents. Animal owners are more aware than ever of potential for presurgical and postsurgical discomfort, and they want assurances that any pain is controlled or alleviated. Major pharmaceutical companies spend significant marketing dollars on increasingly creative media targeted to address public perception of pain and pain management. These same companies also invest heavily in positioning pain management as an important consideration for the veterinary community. The current practice of veterinary medicine requires a comprehensive pain management program that minimizes and alleviates pain and its perception in our patients. Treatment protocols will vary widely among veterinary hospitals and among veterinary practitioners alike. However, it is clear that daily implementation of surgical pain management benefits both the patient and the veterinary–client relationship. Reducing anxiety and fear associated with pain is equally important, and astute veterinary practitioners are consistently using several modes of pain management to improve their patients’ quality of care. Pain‐reduction techniques enhance the perception of value of the cost of veterinary services for

clients, and veterinarians benefit from the improved team approach to pet care.

­Pain What is pain? It is described as an unpleasant sensory or emotional experience associated with actual or potential tissue damage, as defined by the International Association for the Study of Pain (IASP). The primary goal of pain management is to maximize absence of pain sensation and create analgesia. Physiologic pain is a protective mechanism by the body to warn of continuing contact with potentially tissue‐ damaging stimuli. It is produced by stimulation of primary nociceptors innervated by high threshold A‐ delta and unmyelinated C fibers. This type of pain teaches the body to avoid these types of noxious stimuli. This mechanism is managed by a complex interaction of nociceptors; first‐, second‐, and third‐order neurons ascending to the brain; and sensory and descending inhibitory neurons from the midbrain. They all combine to initiate, identify, and modify clinical pain response in our patients. Nociceptors have the important job of recognizing mechanical, chemical, or thermal energy. The affected nociceptors then modify this recognition to an electrical impulse that is carried up from the primary afferent fibers to the dorsal horn in the gray matter of the spinal tract and brainstem. Ultimately, these impulses travel through the thalamus to the cerebral cortex where realization, identification, and response are generated.

1  Portions of this chapter were adapted from: Berger and Eeg (2006).

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

­The Benefits of Pain Management Using Lasers in Surger ­The Benefits of Pain Management Using Lasers in Surger

Pain can further be broken down into subsections of peripheral pain. These include visceral pain and somatic pain. Visceral pain is a poorly localized pain often described in human medicine to be a dull or gnawing type of feeling. This type of pain is typically felt in the thoracic and abdominal viscera. Somatic pain is a localized pain event, identified in human medicine as a stabbing, aching, or throbbing feeling. Somatic pain includes the response noted after soft tissue surgery. It can be cutaneous and superficial or musculoskeletal and related to joint, muscle, periosteum, or bone. Neuropathic pain is often poorly responsive to treatment. This type of pain is a response to direct damage to peripheral nerves or the spinal cord. It can lead to maladaptive compensation by the cerebral cortex thereby perpetuating an inappropriate response to stimuli or lack thereof. For our discussion, clinical pain is the most important consideration before, during, and after laser surgery. Clinical pain is an ongoing activation of nociceptors due to peripheral tissue injury or deeper injury to the nervous system. Nociception is the physiologic process that, when reaching a completed pathway transmission to the cortex, results in conscious perception of pain. The ultimate goal of the laser surgeon is to modify, reduce, or eliminate the three distinct physiologic processes (transduction, transmission, and modulation) involved in nociception by pharmacological, mechanical, and thermal means. CO2 lasers, and to some extent diode lasers, provide the technological means for reducing tissue interaction and therefore reducing pain.

­Patient Pain Recognition Because animals are unable to talk, it is critical that clinicians have a complete understanding of potential physiologic and behavioral signs of pain. Once the clinician understands these pain indicators, they can formulate interventions for their patient. Physiologic alterations due to acute pain include increased blood pressure, heart rate, and peripheral vasoconstriction. Increased respiratory rate and muscle twitching or contraction may also occur. A stress leukogram is often noted in the presence of acute and intermediate pain. Weight loss due to reduced water and food intake may also be noted. Behavioral changes are unique to each patient. It is usually the animal’s owner who notes these changes or lack of normal behavioral signals postoperatively.

Animals typically become less active during painful stimuli, but more restless. The level of relaxation decreases significantly. They become variably aggressive and submissive during pain recognition. Postural changes are often seen in patients that have poor postoperative pain management. Animals generally demonstrate guarding behaviors over surgical sites. This can manifest in a variety of ways such as biting, scratching, licking, chewing, or pawing at the painful area. Cats’ purrs may be mistaken for signs of comfort, when in actuality they are an indication of a behavioral response to pain. When there is a likelihood of experiencing pain from surgical or therapeutic procedures, analgesics must be used regardless of the animals’ outward behavior. It is incumbent upon us, as the patients’ advocates, to use pain management and help the client understand that the benefits of analgesic drug administration far exceed the risks associated with pharmacologic administration to the patient.

­ he Benefits of Pain Management T Using Lasers in Surgery One of the greatest advantages of laser surgery, specifically procedures that use CO2 laser energy, is diminished postoperative pain. There is a preponderance of ­convincing evidence in the medical literature describing ex vivo studies of nerve conduction and reduction following CO2 laser transection. The demonstration of reduced horseradish peroxidase (HRPO) uptake has been the standard proof of reduced nerve conduction. In the veterinary literature, Mison et  al. (2002) showed in a clinical study that there was immediate postoperative reduced pain for CO2 laser declawed cats. The authors showed that in the immediate postoperative period, cats having the CO2 laser surgery technique used for this procedure were able to bear significantly more weight, as measured by peak vertical force on a pressure platform, than cats undergoing traditional scalpel surgery. There was no significant difference in weight bearing at seven days after s­ urgery in cats that had scalpel dissection vs. CO2 laser dissection. In this study, it was concluded that the benefit of using CO2 laser was realized in the immediate postoperative period when it is most important to have ­comfort. A similar study was conducted five years later by an independent group (Robinson 2007) that showed improved limb function may result from decreased pain during the first 48 hours following laser onychectomy.

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Other papers have described that the reduced pain veterinary patients may experience following elongated soft palate resection, anal sacculectomy, ablation of bladder transitional cell carcinoma, aural hematoma repair, meibomian adenoma excision, and a variety of benign skin lesions. Most of these studies focused on the reduction in hemorrhage or postoperative swelling. It is reasonable to further hypothesize from experience that reduced swelling will provide pain relief due to diminished activation of pressure nociceptors. Recently, it has been shown (Carreira et al. 2017) that skin incisions made with a CO2 laser caused a lower increase in arterial blood pressure compared to incisions made with a scalpel blade. This parameter is recognized by the American College of Veterinary Internal Medicine as a reliable indicator of the pain response in anesthetized patients. An increase in arterial blood pressure correlates well with more painful stimuli. Therefore, a significantly reduced measured arterial blood pressure would indicate a reduction in painful stimuli. The authors developed their thesis further by showing that patients undergoing CO2 laser surgery required less anesthesia compared to their counterparts undergoing scalpel surgery for the same procedure. Similar results have been shown in reports from human dentistry and oral surgery. Anecdotally, the perceived pain reduction following CO2 laser surgery continues long after the initial procedure. This has led to a general acceptance in the veterinary community that the use of CO2 lasers in veterinary surgery results in a more comfortable postoperative recovery. Although the transection of nerves, cutting tissue, ablating lesions, and surgery in general is painful and requires anesthesia, it is the intent of conscientious laser surgeons and anesthetists alike to minimize pain. Using a CO2 laser in surgery is one technique to arrive at these goals.

and presurgical epidural, with or without local anesthesia blocks to the skin or target tissue. Preemptive analgesia has been shown to be an effective and less costly way to provide for postoperative pain reduction and return to normal function following laser surgery. Multimodal analgesia simultaneously combines or administers in close order two or more analgesic drug classes and analgesic techniques. This maximizes the reduction in transduction, transmission, and modulation of the afferent pain response at different points in the pain perception pathway. Combining a number of drug classes (as previously stated) and techniques can produce a synergistic analgesia to reduce or eliminate pain perception. The main advantages are inhibition of surgery‐induced peripheral nociceptor stimulation associated with inflammation and transduction, stopping increased neuronal sensitivity within the spinal cord known as “wind up,” transmission, and prevention of resistance to postoperatively administered analgesics due to tachyphylaxis. There is an abundance of nontraditional methods for postoperative pain reduction using a variety of techniques and resources. Our interest is in the use of photobiomodulation. This is the use of near‐infrared laser wavelengths delivered at low‐power density to reduce the initiation and transmission of pain signals. The reader should refer to Chapter 5 for further information on this adjunctive laser treatment modality to surgical laser applications. The ultimate goal of modern anesthetic protocols is better postoperative quality of life. This can be measured by reduced short‐ and long‐term recovery, improved overall tissue healing, increased mobility, and return to normal family interaction. The combination of both preemptive and multimodal analgesia can be applied easily with little additional time or cost. The results are great benefits to the patient and client in the perioperative and postoperative period.

­ ain Management Strategies P for the Laser Surgery Patient

­Conclusion

It is important to embrace both preemptive analgesia and multimodal analgesia for maximum pain relief benefit to the patient. Preemptive analgesia is the administration or application of analgesics prior to surgery. The great advantages of this protocol are decreased duration and intensity of postoperative pain and elimination of a recurrent pain state. A partial list of preemptive analgesic techniques includes anesthetic premedications such as opioids, alpha‐2 agonists, nonsteroidal anti‐inflammatory drugs (NSAIDs),

Current anesthetic and analgesic techniques work synergistically with the use of laser energy during surgery to enhance control of pain. It is beyond the scope of this chapter to include any specific anesthetic or analgesic protocols. It is important that veterinarians and other medical professionals arm themselves and their staff with the best pain management information and surgical techniques to provide for superior pain control for their patients. Using lasers in surgery is one important tool to serve that purpose.­

­Further Readin ­Further Readin

Reference Berger, N.A. and Eeg, P.H. (2006). Pain management considerations for laser surgery procedures. Veterinary

Laser Surgery: A Practical Guide. Chapter 8, 101–108. Hoboken, NJ: Wiley‐Blackwell.

­Further Reading Mison MB, Bohart GH, Walshaw R, et al. (2002). Use of carbon dioxide laser for onychectomy in cats. J. Am. Vet. Med. Assoc. 221(5). pp. 651–653. Robinson DA. (2007). Evaluation of short‐term limb function following unilateral carbon dioxide laser or scalpel onychectomy in cats. J. Am. Vet. Med. Assoc. 230(3). pp. 353–358.

Carreira ML, Ramalho R, Nielsen S, et al. (2017). Comparison of the hemodynamic response in general anesthesia between patients submitted to skin incision with scalpel and CO2 laser using dogs as an animal model. A preliminary study. ARC J. Anesthesiology. 2(1). pp. 24–30.

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24 Laser Surgery in the Mobile Practice Janine S. Dismukes

­Introduction Mobile and house call veterinary practice is the original “Fear Free” paradigm in veterinary medicine. With the new push for “Fear Free” veterinary visits, more veterinarians should consider integrating house calls into their practice. Mobile veterinarians minimize the majority of the pet’s anxiety by allowing them to be in the comfort of their own homes. Many surgeries are perfect fits for mobile veterinary practice, as the pet falls asleep and wakes up in their own home. The only limitation would be those surgeries that require continuous rate infusion (CRI) medications and overnight monitoring postoperatively. A CO2 laser can be used for many types of procedures, including routine spays, neuters, mass removals, meibomian gland adenoma resections, cystotomies, soft palate resections, tonsillectomies, and amputations. This chapter will discuss how and why mobile veterinary services can (and should) include CO2 surgical lasers.

­Advantages There are many advantages of using a CO2 laser instead of a scalpel during mobile practice. First and foremost is the amazing control of bleeding. The laser also seals the lymph vessels. Minimal bleeding and lymphatic drainage thus minimizes bruising and swelling around the incision. This has all been demonstrated in discussion and the pictures throughout this text. However, in mobile practice, the appearance of the incision is particularly important because you are handing the pet directly to the client after a surgery; the laser helps to prevent a ­dramatically bloody, bruised, or swollen appearance to the surgical site. Additionally, the decreased swelling at the incision reduces the need for skin sutures to ensure closure, and the absence of sutures is esthetically ­pleasing

for clients. For most of my surgeries, only subcuticular sutures and skin glue are used. The lack of itchy skin sutures also greatly reduces a pet’s draw to their incision, precluding the need for Elizabethan collars. A mobile veterinary practice that offers CO2 laser surgeries is also considered innovative and appreciated by its clientele (Figure 24.1).

­Equipment A mobile veterinary vehicle that contains a surgery suite is required. The surgery suite must have wall brackets to secure oxygen tanks, blankets for warmth, an anesthesia vaporizer, and anesthesia monitors. Choose a mobile unit floor plan that allows the CO2 laser to be secured in transit as well as during surgery. If you have the laser prior to design of your mobile unit, custom fit a bracket onto the wall so that the laser can be secured during transit. As a practical matter, make sure there is enough electricity available in your mobile unit for the laser to work simultaneously with hot water blankets, heart and blood pressure monitors, lighting, and other equipment. Have the additional equipment needed for plugging into the client’s house for your power needs, should the mobile unit’s electrical requirements be inadequate or fail at the time of the procedure. I prefer the upright CO2 lasers with hollow waveguide and adjustable handpiece. Here is a picture of the bracket that I had installed (Figure  24.2), and a picture of the laser within the bracket for travel (Figure 24.3). I have a small sorting container nearby to hold laser goggles, laser handpieces, laser tips, suture material, and skin glue. The evacuation system is tucked under the surgery table to help remove the laser plume from the suite. With this setup, I can perform any surgery that I could in a standard “brick and mortar” practice.

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

­Logistic ­Logistic

Figure 24.1  A mobile veterinary practice vehicle equipped for laser surgery.

Figure 24.2  Wall‐mounted custom bracket installed for transporting a laser surgical unit.

Figure 24.3  The surgical laser within its bracket for transport.

­Logistics

procedure consent form and informs the client of what will happen, step‐by‐step. We ask that cats are placed in a small bathroom (i.e. no chasing or places to hide) prior to our arrival, as a means of minimizing the cat’s fear and anxiety. We ask that dogs are securely leashed. The veterinarian goes inside the home, obtains baseline vitals, and administers a sedative premedication. Cats can be held in the bathroom by their owners until they fall asleep, then brought into the surgical unit in a carrier. Dog owners are asked to take their pet for a short walk to evacuate bowels and bladder and, when the patient is groggy, walk them into the surgical unit.

The logistics of the mobile laser surgery experience begins with the client calling to schedule the procedure at their home. The receptionist gives the client preoperative instructions and schedules a technician visit to draw preoperative labs if bloodwork has not been acquired recently. On the morning of surgery, the mobile surgical unit parks in the client’s driveway, and a source of power is procured, by either plugging into an outlet on the client’s house or starting a mobile generator. The veterinarian or technician obtains the client’s signature on the

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Figure 24.4  Laser surgical procedures may be conducted in a mobile practice much the same as in a fixed clinic setting.

Owners are invited to stay in the surgical unit while an intravenous catheter is placed, induction medications are administered, the pet is intubated, and cardiopulmonary monitors are attached. Owners are usually content to leave their pet at that time. Surgical sites are clipped and prepped as usual, and the pet is transferred into the surgery suite. The CO2 laser procedure is performed as it would be in a fixed clinic setting (Figure 24.4). At time of extubation, the client is asked to put two towels in the dryer for 5–10 minutes. The warm towels are used to tightly swaddle the small dogs and cats, so the owners can hold them on their own couches as the pet

wakes up. The large dogs are carried inside the home with a stretcher. Most of the time, owners want to sit with the dog while waking up; therefore, a dog bed is placed on the floor in front of the couch. One warm towel is placed on the dog’s bed, then the dog on top of that, and then the other warm towel is placed on top of the dog. The owner sits on the floor holding the dog’s head in their lap to keep their heads from flopping as they wake from anesthesia. If the owner prefers or the veterinarian recommends, the bed and warm towels are placed in a crate or kennel, and the dog is carried directly to it from the surgical unit. It is this author’s observation that animals that wake up smelling their own home and hearing their owner’s voice recover from anesthesia much calmer and smoother than animals who are put in a stainless steel cage in a hospital setting. If the pet was anxious at the time of premedication, then adrenaline is still present when they wake up postoperatively. In extending the “Fear Free” paradigm, have a sedative (half of a Dexdomitor® premedication dose) ready when they are extubated to diminish or even eliminate the dysphoric thrashing or howling. Remind the owner that any vocalizing is not pain but that the pet is not understanding why there are “purple elephants flying around the room.” Recommend that the owner hugs the pet and talks to them in soothing tones to make them feel more secure.

­Conclusion Mobile and house call practice is not only for euthanasia but both pets and owners will also be pleasantly surprised at how smooth and easy a laser surgery experience can be.

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25 Economic Considerations for Laser Surgery John C. Godbold, Jr

­Introduction For at least three decades diplomate and general practitioner surgeons have embraced surgical lasers as valuable tools  –  tools that enhance surgical capabilities, increase surgical precision, facilitate new procedures, and improve the quality of patient care. If those attributes were the only consideration, laser technology would be used in every veterinary practice. Yet, for some, the illusion remains that laser technology is too expensive for veterinary medicine. Do surgical lasers give a positive return on the investment required for their purchase? Is investment in a surgical laser a good idea? Evidence in this and previous publications confirms laser technology can be a valuable addition to the surgery suite (Bartels 2002; Berger and Eeg 2006; Brown 2017). Decades of use and successful practitioner experience also have demonstrated that surgical lasers generate healthy revenue. Prior to investing in a surgical laser, practices should perform a return on investment (ROI) calculation, establish appropriate fees, and develop a plan for training staff and marketing the technology. With appropriate pre‐ purchase analysis and planning, a surgical laser can be economically successful.

­Valuable Technology. Affordable Technology? Veterinary clients have become increasingly demanding of high‐quality veterinary care. Clients expect care will include the most advanced technology available and perceive lasers to be part of that advanced technology. Because of the pervasive use of lasers in the human medical field, veterinary practices incorporating lasers as part of their technology are viewed by clients as being more progressive. Practice image defines what spectrum

of the veterinary clientele a practice attracts. Practices that clients perceive to be advanced, progressive, and cutting edge attract clients willing to pay for high‐quality care (Figure 25.1) (Irwin 2002). Regardless of the wavelength or specific laser device used for the procedures outlined in this textbook, the purchase of a surgical laser requires a significant investment. When this book was published prices ranged from several to tens of thousands of dollars (US$). Any practice investment should be preceded by a ROI assessment (Buy With Confidence 2010; Jergler 2017). Many easy‐to‐use ROI calculators are available on the Internet, including those that are specific for veterinary surgical lasers (Veterinary Surgical Laser ROI 2018). All ROI calculators include consideration of the cost of the equipment, cost of its use, and revenue generated from its use. Cost includes the actual equipment cost (purchased or leased), equipment supplies, maintenance, and staff costs associated with the equipment. Revenues include laser‐specific fees and fees from increased number and diversity of procedures performed. Additional nonspecific revenue will be realized from enhancement of the practice image following the introduction of laser technology. Calculating Cost Accurately estimate cost when calculating potential ROI of a surgical laser. In determining the actual equipment cost, consider whether a lease, lease purchase, financed purchase, or direct purchase is most advantageous. Since tax savings from depreciation or deduction may vary with different types of purchases, consult with the practice accountant for guidance. Estimate operating costs, which include laser expendable supplies, parts that require replacement over time, maintenance, and service plans. Most surgical lasers

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Figure 25.1  Veterinary clients have become increasingly demanding of high‐quality veterinary care. Confident recommendation of laser surgery by the veterinarian helps clients understand that laser surgery is part of high‐quality care. Source: Christopher Winkler.

require replacement of the delivery system every few years. Plume evacuation systems require filter replacement. If a prepaid service plan is not maintained, then a monthly amount should be budgeted for future maintenance. Overall cost of the surgical laser also includes the direct and indirect cost of staff. Time for training and safety certification should be factored in, as well as the day‐to‐day cost of staff time to set up the laser for surgery, assist with the laser during surgery, and set down the laser after surgery.

­Calculating Revenue Initial ROI calculation must include an estimate of ­revenue. One early decision must be how fees will be assigned, adjusted, or included for use of the laser device. Practices may use multilevel, tiered laser‐use fees added to various procedures, adjust total procedure fees when the laser is used, or increase all surgery fees (Textboxes 25.1 and 25.2). Regardless of the approach, an estimate of the average increase in procedure fees is multiplied times the number of procedures currently being performed to estimate laser revenue. The initial revenue calculation will be conservative; it will not include the increase in revenue from the a­ ddition of new clients attracted to a practice doing laser surgery and from the laser facilitating procedures the practice did not previously perform.

Textbox 25.1  Surgical Laser Revenue Projection Using Modest Laser Fees and Infrequent Use Average fee: US$50 Two laser surgery procedures a day Per day – US$100 Per week – US$500 Per month – US$2150 Per year – US$25 800

Textbox 25.2  Surgical Laser Revenue Projection Using Average Laser Fees and More Frequent Use Average fee: US$75 Three laser surgery procedures a day Per day – US$225 Per week – US$1125 Per month – US$4838 Per year – US$58 050

­Laser Fees Practices investing in a surgical laser should not hesitate to charge for using the device. Everything the practice does should reflect value in the technology. Clients expect cutting‐edge technology and accept the value of the technology modeled by the practice. Modeling the value of laser surgery begins with emphasis of patient benefit and continues with fees that reflect the worth of that benefit.

­Plan for Economic Succes ­Plan for Economic Succes

Obviously, fees must be within a range that clients are willing to pay. Fees for laser use must also be acceptable to staff members. If fees are so high that staff members are not comfortable prescribing laser surgery, then the device will not be used. Tiered Fee Structure An early approach to surgical laser fees, still in use in many practices, relies on a tier of laser add‐on or use fees (Textbox  25.3). The tier includes fees ranging from a modest amount for quick outpatient procedures or elective surgeries, to much higher fees for procedures requiring prolonged laser use or greater expertise. The tier may include a “zero” laser fee when the addition of the technology is pro bono. A rationale for this way of assigning fees is that it makes the laser’s use (and the practice’s value of its use) very transparent. Since there is an invoice line item for the laser’s use, the owner is reminded of the laser value with each invoice. Bundled Fee Structure Another approach is to bundle fees (Strategies for Pricing Part 3 2014) for procedures in which the laser is used. This requires increasing the overall fee for procedures by a flat or tiered rate rather than invoicing a specific laser use fee. An argument for this approach is that it eliminates the laser as an estimate item that clients might potentially decline since use of the laser is part of the overall procedure. Practices that use this method frequently promote that all of their procedures are performed with a laser since they are a “laser surgery practice.”

­ ea or Nay? Should Laser Y Be an Option? Many practices agonize over whether to make laser use an option that clients can choose or reject. Too many veterinarians, afraid of client reaction to higher fees when technology is included, have adopted the “a la carte” approach, and offer laser use as an option in procedures. If that has been your approach, outline for several routine surgical procedures the protocols that you know are the safest, the most effective, the most humane, and the most client‐friendly, regardless of cost. Experienced CO2 laser users would include laser use in almost every protocol. Next, ask yourself why you do not offer those protocols as the standard of care in your practice. Why offer less, if you know it is not the best? What will happen if you offer only the best? A few clients will drift away and join the phone shoppers at the local veterinary discount outlet, but the good news is that your fiscal health does not have to be tied to marginal clients. Your financial success can be tied to those clients who seek your care regardless of cost because they know you offer the best care available (Godbold 2002).

­Plan for Economic Success Establishing your practice as a laser surgery practice and making the addition of the laser an economic success requires more than calculating a ROI, establishing fees for its use, and making the commitment to have the laser be one of your standards of care. Staff must be trained and prepared, a core laser message adopted, and an appropriate marketing effort begun and maintained. Training and Staff Preparation

Textbox 25.3  Example of a Tier of Laser Use Fees Assigned as an Invoice Line Item in Addition to All Other Fees for a Procedure Tiered Laser Use Fees Level 0 – Pro‐bono procedures

US$0

Level I – Outpatient procedures

US$5 per min US$50 minimum

Level II – Elective procedures

US$40

Level III – Minor nonelective

US$80

Level IV – Routine nonelective

US$120

Level V – Extended nonelective

US$220

Everyone in the practice must be trained with basic information about the value of laser surgery. A surgical laser is not a sit‐in‐the‐corner, rarely used technology. It is a game changing, practice changing, quality of care‐ changing technology, and all in the practice must know about it. All must know something about it and some must know everything about it. In every practice, there should be a person who is responsible for the laser, ensures everyone is properly trained, and maintains all the information about laser surgery in one place. This important role is usually filled by a veterinary nurse or technician. At least one staff member should undergo laser safety training and be certified as a laser safety officer (LSO). An online LSO

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course with certification is available at www.aimla.org. The LSO will frequently be the head laser nurse or technician. Core Message Each practice should have a core message about laser surgery that all on the staff can paraphrase in his or her words (Figure  25.2). The core message may be simple: “Yes, we use a laser in all of our surgery procedures. It reduces bleeding and swelling and reduces pain afterwards. Patients are much more comfortable after the procedures. We love it and know you will be pleased.” A consistent core message, repeated in every conversation about surgical procedures, helps establish for staff members and clients that the technology is one of your standards of care. Having laser surgery become part of the practice’s identity has been very successful for many practices. Marketing Laser Surgery A generation ago, marketing in veterinary medicine was limited to yellow page ads and printed, mailed communications. Today, yellow pages ads are a distant memory (or should be!) and mailed communications are of little to no value. The digital revolution, driven by the Internet, laptops, tablets, and smart phones, has changed the way clients interact with practices. Clients no longer rely on a practice as their sole source of information. Clients are more informed and client‐to‐client dialogue is common.

Information is a click away and opinions are shared in exponential numbers (Fletcher 2016). Digital images and video have replaced detailed written information, and when written information is used, bullet points that grab (and keep) attention are required (Bruce 2012). Communication in the digital age changes rapidly and good marketing requires understanding digital trends and moving quickly into new digital venues. In‐office Displays, Pictures, and Videos

The lobby, reception, or waiting area and outpatient consultation rooms should be a marketing venue (Figure  25.3). Display pictures of recent laser surgery patients along with their engaged owners. Use a digital picture frame or display monitor to show appropriate videos of laser surgeries along with images of patients before and after surgery. Feature a laser surgery case of the week, both in the practice and on the Internet. Do obtain owner permission before using patient images. Equip initial phone contact and front office staff to identify potential laser surgery patients. Those staff members can begin educating owners about laser surgery and its advantages (the core message) before they reach the consultation room. Practice specific literature, tablet video (Figure 25.4), or a QR code (two‐dimensional barcode) directing the client to online content promoting laser surgery, can be in the owner’s hands while in the lobby and consultation room. Website

An eye catching, current, and search engine optimized website has become critical for effective marketing. Few Figure 25.2  Each practice should have a core message about laser surgery that all on the staff can paraphrase in his or her words. Staff members can begin educating owners about laser surgery and its advantages (the core message) before they reach the consultation room. Source: Christopher Winkler.

­Plan for Economic Succes ­Plan for Economic Succes

Figure 25.3  Educational displays about laser surgery can be placed in the lobby or reception area and serve as entertaining and educational ways of demonstrating the benefits of the advanced technology. Source: Christopher Winkler.

Figure 25.4  Videos of laser surgery patients, before and after surgery, can be shown by staff members to clients in the exam room. Digital tablets allow easy access to videos and pictures for client education. Source: Christopher Winkler.

practices have the internal resources to develop, maintain, and search engine optimize a website, so marketing dollars that used to be spent on yellow page ads and postage now must be directed toward professionals that can make your website an extension of your practice. Devote several pages of your website to laser surgery (Figures 25.5 and 25.6). Use the pages to emphasize the

practice’s core message about why laser is a standard of your care and the benefits of laser surgery in specific procedures. Include the same images, video, and case of the week that are components of in‐office marketing. Supply links to additional authoritative sources of information so clients receive positive reinforcement and support of your approach to the technology.

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Figure 25.5  Devote an entire page of the practice’s website to laser surgery. Use that page to emphasize the practice’s core message about why laser is a standard of your care. Source: Christopher Winkler.

Figure 25.6  Use additional website pages to detail the benefits of laser surgery when used in specific surgical procedures. Source: Christopher Winkler.

­Conclusio ­Conclusio

Figure 25.7  Social media, in multiple forms, is a marketing necessity for today’s practice. Frequent posts about laser surgery cases and their outcomes are popular and generate client interest. Source: Christopher Winkler.

Social Media

A website is used to display information that is more static, whereas social media is used to disseminate rapidly changing information and to establish practice‐to‐ client and client‐to‐client relationships. Social media, in multiple forms, is a marketing necessity for today’s practice. Facebook, Instagram, Pinterest, Twitter, and new platforms that will emerge are the single most effective way to reach clients. Clients’ appetites for still image and video content are now paired with easier methods of making and posting social media updates. To use social media sites effectively the practice needs to make additions, updates, and postings on a regular basis, preferably daily. Since social media content should include images or video, updates most often must be generated from within the practice rather than outsourced (Figure 25.7). Assign the task of keeping social media posts updated to a conscientious, technologically capable staff member who will also monitor for any negative comments. Community Marketing

Kennel clubs, feline clubs, civic groups, and schools all offer opportunities for a practice member to serve as a presenter. Develop a short, simple presentation about laser

surgery for event opportunities. Include images and ­videos, and several laser surgery patient stories. Make a practice member with good communication skills available to attend organizations’ events. Always have a generous supply of practice specific information for attendees including printed information with the practice’s website, social media presence, and a QR code with contact information.

­Conclusion The economic considerations required for a practice to incorporate laser surgery are no more complex than for any other technology. Practices must do an appropriate pre‐purchase analysis of the potential ROI. A proposed fee structure must be established to help determine if incorporating a surgical laser is economically sound. If the potential ROI supports acquiring a surgical laser, then a plan for integrating the technology should be detailed. Staff training and preparation should be initiated and a comprehensive marketing plan developed. Using these logical and organized steps, practices can make a conscientious decision about laser surgery technology and implement it in a way that will be successful.

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­References Bartels KE. (2002). Lasers in medicine and surgery. Vet. Clin. North Am. Small Anim. Pract. 32(3). pp. 497–745. Berger NA, Eeg PH. (2006). Economic consideration for use of laser energy. In: Veterinary Laser Surgery: A Practical Guide. Hoboken, NJ: Wiley‐Blackwell. Brown J. (2017). A look at veterinary lasers. https://www. veterinarypracticenews.com/a‐look‐at‐veterinary‐lasers (accessed 20 January 2018). Bruce R. (2012). 8 quick tips for writing bullet points people actually want to read. https://www.copyblogger. com/writing‐bullet‐points (accessed 20 January 2018). Buy With Confidence. (2010). Buy with confidence. https:// www.veterinarypracticenews.com/buy‐with‐confidence (accessed 20 January 2018). Fletcher D. (2016). How the digital revolution is changing consumer behavior. https://www.linkedin.com/pulse/

how‐digital‐revolution‐changing‐consumer‐behaviour‐ dee‐anne‐slade (accessed 20 January 2018). Godbold JC. (2002). If it is the best, why offer less? Laserpoints. 4. p. 8. Irwin JR. (2002). The economics of surgical laser technology in veterinary practice. Vet. Clin. North Am. Small Anim. Pract. 32(3). pp. 549–567. Jergler D. (2017). Many happy returns. https://www. veterinarypracticenews.com/many‐happy‐returns (accessed 20 January 2018). Strategies for Pricing, Part 3. (2014). Strategies for pricing, Part 3. https://www.avma.org/PracticeManagement/ BusinessIssues/economics/Pages/Strategies-for-PricingPart-3.aspx (accessed 20 January 2018). Veterinary Surgical Laser ROI. (2018). Veterinary surgical laser ROI. https://www.aesculight.com/why‐aesculight/ roi (accessed 20 January 2018).

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Part VI The Future of Lasers in Veterinary Medicine and Surgery

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26 The Future of Lasers in Veterinary Medicine and Surgery Christopher J. Winkler

­Introduction The past two decades have seen incredible progress in the development of laser technologies for the veterinary profession, and there is every indication this will continue. In keeping with the general consensus of today’s veterinary laser practitioners that higher power equates to improved results in surgical outcomes, the latest generation of surgical lasers have been developed with power outputs of up to 45 W at continuous wave, and up to 30 W at SuperPulse. With such units, laser surgery may now be conducted at the same hand speed as that performed with a scalpel blade, with the added benefits of no hemorrhaging, with reduced collateral thermal injury, and with sealed nerve endings and lymphatics. Such an innovation is an extraordinarily useful tool to possess for soft tissue surgery. Let us consider how lasers in veterinary medicine and surgery may continue to be developed and utilized even further.

­Laser Surgical Innovations Laser‐Tissue Welding Today’s surgical lasers are extremely efficient at creating incisions; can we also someday use them for closure of surgical incisions, as this author’s clients so often perceive or request? There is progress being made in this area to reduce or eliminate the need for sutures and ­staples. In studies to improve repair of surgical anastomoses of colorectal cancer patients, near‐infrared wavelengths of laser light have been used photothermally on exogenous nanocomposite chromophores (a protein “tissue patch” of polypeptides or collagen matrices laced with gold nanorods) to seal ruptured ex vivo porcine intestines, demonstrating immediate liquid‐tight seals and enhanced bursting pressure against leakage and peritoneal infection. The laser can be tuned to match the

maximum absorbance of a particular type of patch. The adaptation of this technology to other tissue types may be looked forward to with great anticipation, perhaps one day even replacing linear and circular cutting and stapling devices with dual laser wavelength devices that provide fluid‐tight seals and transect tissue without leaving staples within the patient (Huang et  al. 2013; Urie et al. 2015; Mushaben et al. 2018). Smaller Handheld Laser Units Today’s surgical lasers are large and bulky; it is the delivery system that makes it wieldy to the surgeon, and such delivery systems and handpieces have made great leaps forward over the past decade. But many surgeons yearn for entirely handheld units. Such units would be smaller, lighter and less bulky, allowing mobile and traveling surgeons to carry them with ease between practices, particularly in disaster relief. How would we move toward this goal? The relatively large size of surgical lasers is due to the requirements of the optical resonator, which must be of a certain length in order to function. As mentioned in Chapter 1, weak gain lasers require an active medium of relatively long length. Decreasing this length may be possible if the active media are placed under higher pressure. 3‐D printing using carbon‐fiber nanotubes may make it possible someday to produce an optical resonator small enough for a hand‐held unit while safely containing the pressure of the lasing medium. As we’ve seen in our everyday phones and portable electronics, circuitry is becoming adequately smaller to make a hand‐held surgical laser feasible. Paper‐based batteries may also one day carry enough charge to provide adequate power output for an entire surgery. Once these hurdles are all surmounted, two particular problems remain: smoke evacuation and heat dissipation. Smoke evacuation may always be a separate system where hand‐held lasers are concerned, but such units are still

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

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relatively small and quite portable compared to present‐ day lasers themselves. A heat dissipation technique would have to be developed, then, to allow for the safe operation of a hand‐held unit for the patient, surgeon, and the unit itself (Nystrom et  al. 2009; Chang 2014; Huang et al. 2014). In the meantime, strides may continue to be made toward developing more flexible and yet more rugged and efficient beam delivery systems. A hollow waveguide just as small and yet just as flexible as an optical fiber would continue to advance the way endoscopic procedures may be integrated with CO2 lasers, further increasing the number of minimally invasive procedures that can be performed. The continued development of specialty handpieces for specific procedures is also a direction of interest. A handpiece feature to strongly consider would be a feedback mechanism detecting tissue absorption spectra and temperature, adjusting the laser’s power density automatically in response to efficiently achieve the desired surgical effect.

­Laser Surgical Integrations The integration of laser surgery with other technologies will continue to further innovate how veterinary surgery is conducted. Even if a hand‐held surgical laser unit presently remains unworkable, the miniaturization of optical resonators would still allow for the production of even smaller lighter surgical laser units than those presently available. Smaller CO2 resonators would make room for the integration of other near‐infrared laser wavelengths within the same housing. Coupling such a unit with multiple flexible delivery systems would allow the surgeon the option of selection from WYSIWYG to WYDSCHY to SYCUTE surgical wavelengths and even therapeutic laser wavelengths in a single procedure, all delivered through a single hand piece. Smaller smoke evacuation units might also be integrated within the laser’s housing and hand piece. Cooperation between a variety of vendors may see the integration of video endoscopes into such a laser unit, providing the veterinary surgeon with a single minimally invasive endoscopic device delivering a multitude of laser wavelengths for enhanced versatility of procedures. Although push‐button consoles are now the norm, voice‐activation and Bluetooth may become mainstream in a sterile operating environment to assist the surgeon in system activation and safety. Voice‐activation may be integrated into today’s lasers to allow the surgeon to program power, exposure, operating mode, frequency, and duty cycle, and switch the unit from STANDBY to READY and back, all without the need for contact with the console. A Bluetooth earpiece could also be equipped

to vibrate when the laser is activated, creating an additional safety feature for veterinarians with hearing impairment. Heads‐up displays developed for aerospace are seeing use in modern motorcycle helmets, while wearable televisions and virtual reality systems are also now available to the public. With the integration of voice‐activated systems to eliminate direct contact with the laser, the additional step could be taken to provide a display in the laser surgeon’s protective eyewear to show the laser’s present display of power and settings (BioOptics World 2014; Cision PR Web 2018). As the use of therapy lasers becomes more prevalent in the operating theater, multiple optical density (OD) values in laser safety eyewear would eliminate the need for multiple lenses for different laser wavelengths and changing them on sterile personnel as they switch to different lasers during a procedure. An alternative would be to create laser safety eyewear with lenses capable of polarizing to different OD levels for different laser wavelengths, which may also be voice‐activated. Combining voice‐activation, displays which provide the surgeon valuable information at just a glance, and elimination of multiple safety lenses, would reduce the time of the operation even further, and therefore the patient’s time under anesthesia. Human trans‐oral robotic surgery (TORS) using CO2 lasers is already a reality. Such integration has demonstrated combining the superior dexterity of the robotic arm with the enhanced surgical aspects of the CO2 laser over steel scalpels or electrocautery, to precisely remove tumors with minimal invasiveness while improving post‐ surgical chemotherapy and radiation therapy options. The surgeon is not even required to scrub in for such a procedure and may even perform the surgery remotely. It is not difficult to imagine such equipment being developed for veterinary use as it becomes more widely available (UTHealth 2014; Mount Sinai 2018). Indeed, a report from the Oklahoma City Zoo and Botanical Garden has demonstrated that veterinary robotic surgery has already been used successfully during a gorilla’s umbilical hernia repair procedure to minimize trauma (KFOR‐TV and Querry 2018).

­Laser Education Veterinary School Curriculums The technologies and techniques we have discussed in this textbook are well‐established, and there is every indication that they will remain and continue to be developed, becoming an integral part of veterinary medicine and surgery of today and tomorrow. Colleges of Veterinary Medicine should consider taking steps to

­In Their Own Words: The Authors on the Future of Laser

incorporate coursework on laser physics, laser–tissue interaction, and laser safety into their curriculums to prepare their students and graduates for the technologies becoming so readily available in today’s practices. Such education would make tomorrow’s veterinarians valuable to their employers, improve levels of safety in veterinary facilities, and increase confidence and alacrity in veterinarians’ familiarity with laser equipment and techniques, all while continuing to improve the quality of patient care and meeting public expectations for the best and most advanced services available to their pets. Acceptance of Laser Medicine and Surgery as a Board Certification Specialty The precedent exists in radiology for a board certification based on a technology and how it interacts with living tissue in order to improve patient care. ­ Compartmentalizing components of a laser education within an existing specialty (such as surgery, internal medicine, or rehabilitation) potentially isolates the student from a complete understanding of how lasers work and fundamentally interact with living tissue, as the different lasers used in surgical applications, photodynamic therapy, and photobiomodulation all share the same roots in physics, tissue interaction, and safety, making a broad study of the subject invaluable to the understanding of practitioners wishing to implement these technologies in an integrated effort with utmost effectiveness. Governing bodies of veterinary medicine should therefore consider the establishment and recognition of laser medicine and surgery as a separate board certification.

I­ n Their Own Words: The Authors on the Future of Lasers My vision is of an un‐tethered laser surgical hand‐ piece, with laser emission activated and deactivatedbythesurgeon’sfingerpressure.Thehand‐piece will monitor tissue temperature and adjust power density for best tissue effect. John C. Godbold, Jr., DVM I have seen many advances in the use of Lasers over the past 28 years for both human and animal uses. I hope new applications continue to develop and that more surgeons take advantage of this amazing technology. Les “Laser Les” Lattin Laser surgical procedures offer the option to p erform traditional surgical procedures with ­ decreased morbidity, decreased surgical time,

and decreased recovery time. The future of laser surgery also offers the opportunity to perform procedures that a scalpel and blade previously could not reach. Gaemia Tracy DVM When I was a student in the mid 1980s, ultrasound imaging was becoming available, and we thought it would be utilized by specialists only. At this time, more than 30 years later, it is extremely common for general practitioners to have these devices in their hospitals for everyday use. My belief is that in the near future, every practitioner will have a laser in their hospital as well. The benefits are so obvious for the patient, client, and veterinarian alike. All veterinarians someday will be using surgical lasers, therapeutic lasers, and possibly refer cases for diagnostic imaging using lasers for optical coherence tomography. Noel Berger, DVM, MS, DABLS The future of CO2 lasers in veterinary surgery will revolve around minimally invasive robotic surgery. Human surgeons have embraced this new and exciting technology in the treatment of head and neck cancer, urogenital disease in women such as myomyectomy for uterine fibroids and prostatectomy in men. These robotic devices consist of a small flexible fiber‐based laser delivery system with a 360° mobile laser tip. They are equipped with cameras that can provide 3‐D images. They can be used by themselves or ­combined with a magnifying device such as an operating microscope. The mobility of the laser tips exceeds that of the human wrist allowing the surgeon unparalleled access to the target tissue. These devices incorporate and enhance the ­advantages of the CO2 laser: precise dissection, hemorrhage control and minimal collateral tissue damage. Procedures using minimally invasive robotic devices help achieve the goals of surgery: diminished patient morbidity, shorter anesthesia and hospitalization times and earlier return to function. Daniel M. Core, DVM There is much interest in performing direct tissue apposition … to directly “weld” vessels, bone, nerves, and possibly other soft tissues. This would reduce the morbidity and delay in healing associated with using artificial substances such as suture, glues, and even allografts. David S. Bradley, DVM, FASLMS

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­References BioOptics World. (2014). Ophthalmology/image‐guided surgery: ‛heads‐up’ 3D‐enabled retinal surgery broadcast live. https://www.bioopticsworld.com/articles/print/ volume‐7/issue‐3/departments/news‐notes/ ophthalmology‐image‐guided‐surgery‐heads‐up‐3d‐ enabled‐retinal‐surgery‐broadcast‐live.html (accessed 24 June 2018). Chang A. (2014). New 3D printer by MarkForged can print with carbon fiber. https://www.popularmechanics.com/ technology/gadgets/a10025/new‐3d‐printer‐by‐ markforged‐can‐print‐with‐carbon‐ fiber‐16428727/?click=pm_latest (accessed 24 June 2018). Cision PR Web. (2018). The Los Angeles Minimally Invasive Spine Institute reports the first use in the United States of a Novel Sony Heads‐Up Display for spinal surgery. http://www.prweb.com/releases/2016/06/ prweb13517248.htm (accessed 24 June 2018). Huang K, Seo M, Sarmiento T. et al. (2014). Electrically driven subwavelength optical nanocircuits. Nat. Photonics 8, 244–249. Huang H, Walker C, Nanda A. et al. (2013). Laser welding of ruptured intestinal tissue using plasmonic polypeptide nanocomposite solders. ACS Nano. 7(4). pp 2988–2998. KFOR‐TV and Querry K. (2018). Oklahoma City gorilla undergoes first robotic surgery to repair hernia. https://

kfor.com/2018/09/24/oklahoma‐city‐gorilla‐undergoes‐ first‐robotic‐surgery‐to‐repair‐hernia (accessed 25 September 2018). Mount Sinai. Skull Base Surgery Center. (2018) TransOral Robotic Surgery (TORS) program. https://www. mountsinai.org/locations/skull‐base‐surgery‐center/ treatment/transoral‐robotic‐surgery‐tors (accessed 24 June 2018). Mushaben M, Urie R, Flake T, et al. (2018). Spatiotemporal modeling of laser tissue soldering using photothermal nanocomposites. Lasers Surg. Med. 50(2). pp. 143–152. Nystrom G, Razaq A, Strømme M, et al. (2009). Ultrafast all‐polymer paper‐based batteries. Nano Lett. 9(10). pp. 3635–3639. Urie R, Quraishi S, Jaffe M, et al. (2015). Gold nanorod‐ collagen nanocomposites as photothermal nanosolders for laser welding of ruptured porcine intestines. ACS Biomater. Sci. Eng. 1(9). pp. 805–815. UTHealth. (2014). TORS‐L: transoral robotic surgery with CO2 laser offers greater precision for surgeons and de‐intensification of adjuvant therapies for patients. https://med.uth.edu/orl/2014/08/25/tors‐l‐ transoral‐robotic‐surgery‐with‐co2‐laser‐offers‐ greater‐precision‐for‐surgeons‐and‐de‐ intensification‐of‐adjuvant‐therapies‐for‐patients (accessed 24 June 2018).

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Appendix A Glossary Ablation  The process of removal of tissue by cutting or vaporization. Typically achieved in laser surgery when fluence exceeds 3 J/cm2. Absorption  The conversion of light to other forms of energy when it passes through material media. Active medium  A material selected for containment within a given optical cavity to undergo stimulated emission for the production of radiant energy (photons). The specific medium used within the optical cavity of a laser resonator determines the specific wavelength of laser light produced by that resonator. Articulated arm  A delivery system consisting of an apparatus of tubes and seven 360°‐swiveling elbow joints, each joint containing a mirror of high reflectance. Atom  The smallest unit having all the unique physical and chemical properties of any one of the elements, of which there are 108 varieties presently known. An atom consists of a nucleus containing neutrons (uncharged particles) and protons (positively charged particles), around which smaller, negatively charged particles known as electrons rotate in orbits that can be elliptic or circular and are constrained to have only certain sizes and distances from the nucleus. In a normal (neutral) atom, the number of electrons is equal to the number of protons. Attenuation  The progressive weakening of a light ray as it penetrates deeper into a material medium. In general, it is caused by both absorption and scattering. In homogeneous, isotropic materials, it is exponential in nature: the ray loses a constant fraction of its intensity in every unit distance of forward travel. Average power  An expression (in W) of the total amount of laser energy delivered divided by the duration of the laser exposure. For a pulsed laser, the product of the energy per pulse (J) and the pulse frequency (Hz). Beam of light  A bundle of rays of light traveling in the same general direction with an included solid angle that is less than 90°. May be divergent, convergent, or collimated.

Chromophore  A substance, molecule, or tissue type exhibiting selective light‐absorbing qualities (often to specific wavelengths), facilitating its conversion to other forms of energy. Also known as a photoacceptor. Coagulation  A process of denaturing living tissue by heating it to temperatures between 45 and 70 °C for sufficient periods of time. Typically, occurs in laser surgery at a fluence of 3 J/cm2 or less. Coherence  A unique characteristic of laser radiation, manifested in two ways: spatial and temporal. Spatial coherence is the coincidence of the crests and valleys of the electrical waves of light rays in a beam, along surfaces that are everywhere perpendicular to the rays. Temporal coherence is the constancy of speed of propagation, frequency, and wavelength of the light waves. Collimation  The property of a beam of light in which all the rays are parallel to one another; the beam has no divergence, and its included solid angle is 0°. A characteristic of laser radiation. Contact technique  A laser technique in which the delivery system of the laser comes into direct contact with the target tissue, such as the direct contact utilization of a charred hot glass tip of a diode or Nd:YAG laser. Continuous wave  A type of exposure where laser light is continuously emitted as long as the activation switch is depressed. By definition, a continuous wave always possesses a duty cycle of 100%. Delivery system  A means of delivery of laser light from a resonator to a patient. Its distal end is typically fitted with either a handpiece or other piece of equipment (a microscope or endoscope) for the refinement of laser light delivery to the patient. Drug‐to‐light interval  The period of time between the administration of a photosensitizer and its activation by light. Duty cycle  The percentage of a given single cyclical period of time in which laser light is being emitted, or

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

342

Appendix A Appendix A

“on.” For example, in a period of 1 second, if the laser were on for 0.8 seconds and off for 0.2 seconds, the laser’s duty cycle would be 80%. Electron  The small, negatively charged particle that orbits the nucleus of an atom. Energy  The ability to do work, such as lifting a mass against the force of gravity. The product of power (W) and duration (seconds). 1 J = 1 W × 1 second. Energy density  A synonymous term with fluence (see fluence). Excimer  A diatomic molecule consisting of a halogen atom (Cl or F) and an atom of noble gas (argon, dkrypton, or xenon), which exists only in the excited state of one or both atoms, and dissociates after emitting radiation in the ultraviolet portion of the spectrum. Excitation  The process by which an atom or molecule or ion increases its energy above the normal, or ground, level. It requires absorption of a quantum of energy from outside having exactly the value corresponding to the difference between the ground level and some permitted higher level. Exposure  The synonymous term used in this textbook for a temporal mode. Fluence  The energy delivered by a laser beam to a target, divided by the irradiated area of that target. The basic unit is 1 J/cm2. Frequency  The number of cycles per second of a sinusoidal wave of light passing a fixed point in space; or the number of pulses per second in the output power of a pulsed laser. Gaussian  The name given to a laser beam that has the most fundamental transverse electromagnetic mode (TEM00), or bell‐shaped distribution of power density across the beam. Hand piece  That part of a laser’s delivery system held in the hand of a surgeon for delivery of laser light to the patient. Handpieces come in a variety of designs, some with the means to adjust spot size in order to further manipulate control of fluence and power density during a surgical procedure. They are typically made of autoclavable materials to facilitate sterility. Hertz  The basic unit of frequency in the International System (SI) of units, measured in cycles per second. Hollow waveguide  A delivery system consisting of a flexible hollow metal tube, the inner surface of which carries high reflectance. Index of refraction  The ratio of the speed of light in free space to its speed in a material medium. The refractive index of every material medium is greater than unity, except near wavelengths where the medium exhibits significant absorption. Intensity  Synonymous with irradiance and power density of a ray or beam of light (see power density).

Ion  An atom in which the number of orbiting electrons is not equal to the number of protons on the nucleus. It has a net electric charge that is either positive or negative, but not zero. Irradiance  Synonymous with Intensity and power density of a ray or beam of light (see power density). Joule (J)  The basic unit of energy or work in the International System (SI) of units, equal to an exposure of 1 W of power for one second. Kilogram (kg)  The basic unit of mass in the International System (SI) of units, equal to 1000 g. Laser  An apparatus for the purpose of generating coherent, collimated, monochromatic electromagnetic radiation. The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation. Laser light  The spectrum of electromagnetic radiation producible by a laser apparatus, ranging from 100 to 20 000 nm, and consisting of sinusoidal waves of orthogonal electric and magnetic fields that are both perpendicular to its axis of propagation. Characteristics particular to laser light include coherence, collimation, and monochromaticity. Longitudinal modes  Those discrete wavelengths of standing waves of light reflected back and forth between the mirrors of an optical cavity in such a way that the forward and backward waves reinforce each other. Mass  The essential property of matter. Mass is convertible into energy according to the equation E = mc2, where E is energy, m is mass, and c is the velocity of light in free space. Matter  The fundamental substance of which all materials in the universe are composed. Its most important property is mass. Its basic unit is the atom. Meter  The basic unit of length in the International System (SI) of units. Molecule  A collection of atoms bound together by forces associated with the outermost electrons. Inorganic molecules are usually smaller than organic, the most complex of which can contain thousands of atoms. Monochromaticity  The property of having just one wavelength. A characteristic of laser radiation. Micrometer (μm)  One millionth (10−6) of a meter. Also known as a micron. Microsecond (μs)  One millionth (10−6) of a second. Mie scattering  A type of scattering caused by particles greater than or equal to the wavelength of the laser light being scattered, predominantly occurring in a forward direction of propagation. Millisecond (ms)  One thousandth (10−3) of a second. Mode  For the purpose of this textbook, the state in which the laser is operating with Superpulse either on or off.

Appendix A

Nanometer (nm)  One billionth (10−9) of a meter. In this textbook, the basic unit of a wavelength of laser light. Nanosecond  One billionth (10−9) of a second. Non‐contact technique  A laser technique in which the delivery system does not touch the target tissue, such as the beam of a CO2 laser. Light radiation may be focused or defocused depending on operator’s technique and procedure. Optical cavity  A chamber or volume of space coaxial with and located between two mirrors whose geometry is such that a paraxial ray of light traveling back and forth between the mirrors will always remain within the cavity. Optical fiber  A delivery system consisting of a solid slender filament of optically transparent material (quartz, glass, or polymethylmethacrylate) having a diameter between 0.1 and 1.0 mm and an index of refraction significantly greater than unity. It is usually clad with a thin coating of another material having a lower index of refraction. It transmits light by total internal reflection, even around bends of short radius. Peak power  The highest power in a laser pulse. Photobiomodulation  In medicine, the utilization of light energy to achieve physiological and biochemical changes within tissues in order to obtain a beneficial therapeutic outcome. Photochemolysis  Breakdown of living tissue or inorganic polymers by rupture of interatomic bonds caused by energetic photons at wavelengths shorter than 319 nm. This process occurs at average power densities below 1 W/cm2. Photodynamic therapy  The selective removal of unwanted cells and tissues through the release of reactive (singlet) oxygen by a chemical substance (photosensitizer) following that substance’s activation by light. Photon  A massless quantum of radiant energy, transmitted through free space and material media in straight‐lines at the speed of light. It is equivalent to a wavelet, and its energy is proportional to the frequency of this equivalent wavelet. Photoplasmolysis  The ionization of atoms in molecules by the strong electric fields of light waves at power densities above 10 billion W/cm2, to form a plasma at very high temperatures. Photopyrolysis  The conversion of light into heat within tissue, causing the elevation of its temperature to levels and for time intervals such that the tissue is destroyed (but not vaporized) by thermal breakdown and the denaturation of proteins, at temperatures between 50 and 100 °C. This process occurs in soft tissue at power densities between 1 and 100 W/cm2.

Photosensitizer  A chemical substance applied topically or systemically with selective uptake by cells that, when activated by light, releases reactive (singlet) oxygen to cause local cell death. Photothermolysis  The conversion of light into heat within tissue and the subsequent destruction of that tissue either by thermal breakdown or by vaporization of the histologic water. Includes both photopyrolysis and photovaporolysis. The primary process by which most laser surgery is conducted. Photovaporolysis  The conversion of light into heat within tissue, causing subsequent destruction of that tissue through rapid boiling of the water within and between cells to form steam, which expansively ruptures the cells and destroys the histologic architecture, at temperatures between 100 and 300 °C. This process occurs in soft tissue at power densities between 100 and 1 000 000 W/cm2. Picosecond  One trillionth (10−12) of a second. Planck’s constant  The proportionality factor (h) in the equation relating photonic energy to the frequency of the equivalent wavelet: Ep = hf. This factor is named after Max Planck, and its value is 6.626 × 10−34 J s. Plume  The smoke produced from aerosolization of by‐products due to laser–tissue interaction. It is composed primarily of water vapor, with cellular debris, particulate matter, carbonaceous and inorganic materials, and potentially biohazardous products. Population inversion  A condition of having more atoms or molecules of a medium in an excited state within a laser resonator than in unexcited or less‐ excited states. Power  The amount of work performed in a unit of time, such as the time‐rate of transfer of energy from one place to another, or transformation of energy from one form to another. The basic unit of power is the watt (W). 1 W = 1 J/1 second. Power density  The power transmitted by a laser beam per unit area of cross‐section of that beam, or the power falling upon the target of a laser beam per unit area of the irradiated surface of that target, also known as intensity and irradiance. The basic unit of power density in laser surgery is 1 W/cm2. Pulse duration  A measurement of the total amount of time that a pulse is emitted; also known as pulse width. Pumping  The process of adding energy to a laser medium in such a way that its atoms or molecules are excited, creating a population inversion. Radiation  The transport of energy through space from one point to another, with or without the need for an intervening material medium. It occurs in straight‐lines

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Appendix A Appendix A

and at constant speed in a homogeneous, isotropic medium. Radical  A group of connected atoms or ions that passes unchanged through a chemical reaction, and may form an important constituent of a molecule. Randomly diffused radiant flux  Light within tissue having such strong scattering that the probability of photon travel is equal in all possible directions. The exact opposite of collimated, coherent radiation such as laser light. When dealing with randomly diffused radiant flux, power density is the number of photons per unit time passing through a small sphere, divided by the equatorial cross‐section of that sphere. Ray of light  The axis of a light wave. Rayleigh scattering  A type of scattering caused by particles less than the wavelength of the laser light being scattered. Unlike Mie scattering, Rayleigh scattering is strongly dependent on the wavelength of laser light and may occur in any direction. Reflection  The redirection of a ray of light from its impact point on the boundary surface between two different media back into the hemisphere of space, centered at the impact point, from which that ray originated, in such a way that the angle of incidence is equal to the angle of reflection (both measured from the perpendicular to the reflecting surface in the plane defined by the incident and reflected rays). In general, some of the intensity of the ray will be lost by penetration into the reflecting medium, so that the reflected ray is relatively weaker than the incident ray. Refraction  The change in direction of a ray of light upon striking the interface between two media of different refractive indices, in such a way that the angle of incidence is always less in the medium of higher index. In general, refraction is accompanied by reflection of some of the intensity of the incident ray, except where the angle of incidence is greater than the critical angle for total reflection in dense‐to‐rare crossing of the interface. Repeat pulse  A type of exposure where the laser light is emitted intermittently in short bursts as long as the trigger is depressed. Repetition rate  Number of pulses per second, also known as the pulse rate, usually expressed in hertz. Resonator  That part of a laser apparatus consisting of the optical cavity and the active medium contained therein. Scattering  The change in direction of a ray of light in a material medium or living tissue without a change of wavelength; the result is the dispersal of the ray of light throughout tissue. Second (s)  The basic unit of time in the International System (SI) of units.

Single pulse  A type of exposure where laser light is emitted in only a single timed burst with depression of the trigger. Singlet oxygen  The lowest excited state of the O2 molecule. Highly cytotoxic in its reaction with surrounding organic compounds. Spectrum  A continuous range of wavelengths or frequencies of electromagnetic radiation. The whole electromagnetic spectrum spans more than 20 orders of magnitude, from long radio waves to ultra‐short cosmic rays. Speed of propagation  The distance traveled per unit time by a light wave or photon, without regard to direction. In free space, it is 2.998 × 108 m/s. Spontaneous emission  The emission of a photon of light by an excited atom or molecule as it returns to a lower level of energy without an external influence. The source of all light in nature. Spot Size  In focused laser beam systems, the diameter (in mm) of the circular pattern that laser light produces on its target tissue that contains 86% of the total power of the laser beam, or the diameter of the aperture of a handpiece to create just such a circular pattern when held at optimal focal distance from the target tissue. Spot size is inversely proportional to power density. Stimulated emission  The triggering of an excited atom or molecule by an incident photon to emit an identical photon, parallel to and synchronized with the incident photon, but without absorption of the incident photon. Superpulse  A mode of laser light delivery characterized by extremely short pulses of high peak power, in which the pulse durations are shorter than thermal relaxation time, while the spacing between pulses is greater than thermal relaxation time. Such intense pulses of high power exceed the power of a continuous wave exposure and help to facilitate efficient ablation, while the interval between pulses minimize collateral thermal trauma. Superpulse may be available in different forms of exposure. Temporal mode  The pattern of time‐variation of output power from a laser apparatus. In this textbook, temporal mode is synonymous with Exposure. Usually, available in three pre‐programmed forms: continuous wave, repeat pulse, or single pulse. Thermal relaxation time  The rate at which an irradiated tissue diffuses heat; it is dependent on a particular tissue’s wavelength‐dependent absorption coefficient. Transmission  The passage of laser light directly through tissue without any tissue effects, due to lack of an appropriate absorptive or scattering medium relative to the laser’s wavelength.

Appendix A

Transverse electromagnetic mode  The distribution of power density across a laser beam as a function of angular position and radial distance from the axis. It is usually abbreviated as TEMmn, where m and n are integers equal to the number of troughs of power density in the x‐direction and y‐direction, respectively, of a three‐dimensional plot of the intensity profile of the beam in which the z‐direction is the beam axis of propagation. Vaporization  The conversion of liquid water into vapor.

Velocity (of a photon or wave)  The vector whose direction is the direction of travel at the point or moment in question, and whose magnitude is the speed of the wave or photon at that point and moment. Watt (W)  The basic unit of power in the International System (SI) of units. 1 W equals 1 J/s. Wavelength  The distance between any two successive crests of the electric wave of a ray of light. In this book, measured in nanometers.

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Appendix B Certifying and Academic Laser Organizations American Board of Laser Surgery (ABLS) Administrative Office 55 Corporate Drive, 3rd Floor Trumbull, CT 06611, USA Phone: 203‐332‐2507 www.americanboardoflasersurgery.org [email protected] American Institute of Medical Laser Applications (AIMLA) 18070 Raymond Rd Marysville, OH 43040, USA Phone: 937‐642‐9813 www.aimla.org [email protected] [email protected] American Laser Medicine College and Board (ALMCB) (Advanced level training and certification in laser ­surgery and laser dentistry) Peter Vitruk, PhD [email protected]

Laser Institute of America (LIA) 13501 Ingenuity Drive, Suite 128 Orlando, FL 32826, USA Phone: 1‐800‐345‐2737 www.lia.org https://www.lia.org/contact International Academy for Laser Medicine and Surgery (IALMS) Borgo Pinti 57 50121, Florence, Italy Phone: (+39) 055.234.2330 http://ialms.international [email protected] North American Association for PhotobiomoduLation Therapy (NAALT) 3700 Koppers Street, Suite 100 Baltimore, MD 21227, USA Phone: 410‐592‐9889 www.naalt.org www.naalt.org/contact

American Laser Study Club (ALSC) www.americanlaserstudyclub.org [email protected] American Society for Laser Medicine and Surgery (ASLMS) 2100 Stewart Avenue, Suite 240 Wausau, WI 54401, USA Phone: 715‐845‐9283/877‐258‐6028 www.aslms.org [email protected]

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

347

Appendix C Tables of Laser Settings Table C.1  Chapter 7: Canine and feline elective laser surgery procedures.

Procedure

Laser type wavelength

Spot size (mm)

Power (W)

Exposure

Mode

Frequency (Hz)

Duty cycle (%)

Onychectomy, feline

CO2

0.25–0.4

6–12

Continuous wave

SuperPulse

—

100

0.25–0.4

8–15

Continuous wave

SuperPulse

—

100

0.25

6

Continuous wave

SuperPulse

—

100

0.25–0.4

10–20

Continuous wave

SuperPulse

—

100

0.25

7–10

Continuous wave

SuperPulse

—

100

10 600 nm Orchiectomy, canine

CO2 10 600 nm

Orchiectomy, feline

CO2

Ovariohysterectomy, canine

CO2

10 600 nm

Ovariohysterectomy, feline

10 600 nm CO2 10 600 nm

Laser Surgery in Veterinary Medicine, First Edition. Edited by Christopher J. Winkler. © 2019 John Wiley & Sons, Inc. Published 2019 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/winkler/laser

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Appendix C

Table C.2  Chapter 8: Canine and feline oral laser surgery procedures.

Procedure

Laser type Spot size/fiber wavelength diameter (mm)

Contact mucositis and mucosal ulceration

CO2 10 600 nm

Frenectomy

CO2

Power (W) Exposure

Mode

Frequency (Hz) Duty cycle (%)

0.8, or 2.5 × 0.4 3–6

Continuous wave Non‐SuperPulse —

100

0.4

4–6

Continuous wave Non‐SuperPulse —

100

CO2

0.25 or 0.3

4–8

Continuous wave Non‐SuperPulse —

100

10 600 nm

0.8

10–15

CO2

0.8 (defocused) 8–10

Continuous wave Non‐SuperPulse —

100

0.8 (defocused) 4

Continuous wave Non‐SuperPulse —

100

0.25 or 0.3

10

Continuous wave Non‐SuperPulse —

100

4

Continuous wave Non‐SuperPulse —

100

0.25 or 0.3

5

Continuous wave Non‐SuperPulse —

100

4 (defocused)

2

Continuous wave Non‐SuperPulse —

100

0.8–1.5

Repeat pulse

Pulsed

 50

30 s

33 ms

10 600 nm Gingivectomy Gingivoplasty

10 600 nm Gum Chewer’s lesions

CO2 10 600 nm

Operculectomy

CO2 10 600 nm

Diode laser 0.3 810 nm Oral mass excision

CO2 10 600 nm

Periodontal pocket surgery

CO2 10 600 nm

Diode laser 0.3 810 nm Stomatitis, feline

CO2

15–17

0.8

6

Continuous wave Non‐SuperPulse —

100

0.4

10

Continuous wave Non‐SuperPulse —

100

10 600 nm Tongue surface surgery CO2 10 600 nm

Table C.3  Chapter 9: Canine and feline laser surgery procedures of the nose and throat. Laser type wavelength

Spot size (mm)

Power (W)

Exposure

Elongated soft palate (marking)

CO2

0.4

6–8

Elongated soft palate (excision)

10 600 nm

Procedure

Frequency

Duty cycle (%)

Repeat pulse Non‐SuperPulse

10 Hz, 10 ms

 10

15–30

Continuous wave

—

100

0.4

3–4

Continuous wave

—

100

Stenotic nares (marking) CO2

0.4

4

Repeat pulse Non‐SuperPulse

2–5 Hz, 10 ms

2–5

Stenotic nares (alar fold ablation)

0.8

10–20

Continuous wave

SuperPulse or non‐SuperPulse

—

100

0.4

8–10

0.4

3–4

Continuous wave

Non‐SuperPulse

—

100

Everted laryngeal saccules

CO2 10 600 nm 10 600 nm

Stenotic nares (alar fold excision) Tonsillectomy

CO2 10 600 nm

Mode

SuperPulse

Table C.4  Chapter 10: Canine and feline laser surgery procedures of the ear.

Procedure

Laser type wavelength

Spot size (mm)

Power (W)

Exposure

Mode

Frequency

Duty cycle (%)

Apocrine cysts

CO2

0.8

3–4

Repeat pulse

Non‐SuperPulse

2 Hz, 200 ms

 40

6

Continuous wave

—

100

1.4

10–15

Continuous wave

Non‐SuperPulse

—

100

0.8

3–4

Repeat pulse

Non‐SuperPulse

2 Hz, 200 ms

 40

Continuous wave

SuperPulse

—

100

Non‐SuperPulse

—

—

2 Hz, 200 ms

40

10 600 nm Aural hematoma

CO2 10 600 nm

Cerumen glands

CO2

120–180 WG

Myringotomy

Nasopharyngeal polyps Stenotic ear canals

10 600 nm

0.25

CO2

0.8

4–6

Single pulse, 200–500 ms

10 600 nm

120–180 WG

4

Repeat pulse

CO2

0.8

10–15

—

100

120–180 WG

Continuous wave

Non‐SuperPulse

10 600 nm

6–7

Continuous wave

Non‐SuperPulse

—

100

CO2

0.8

10 600 nm

120–180 WG

Table C.5  Chapter 11: Canine and feline periorbital and eyelid laser surgery procedures.

Procedure

Cherry eye

Laser type wavelength

Spot size (mm)

Power (W)

Exposure

Mode

Frequency

Duty cycle (%)

CO2

0.25

3–4

Continuous wave

SuperPulse

—

100

0.25–0.4

3–5

Continuous wave

SuperPulse

—

100

Single pulse, 200–500 ms

Non‐SuperPulse

—

—

10 600 nm CO2

Distichiasis

10 600 nm Entropion (incisional)

10 600 nm

CO2

Entropion (non‐incisional)

10 600 nm

Eyelid neoplasia Lagophthalmos

CO2

0.25 or 0.4

10–15

Continuous wave

SuperPulse

—

100

0.4

8–10

Continuous wave

Non‐SuperPulse

—

100

Continuous wave

SuperPulse

—

100

CO2

0.25 or 0.4

3–5

10 600 nm

0.4

8–12

CO2

0.25

3–4

Continuous wave

SuperPulse

—

100

0.4

15–20

Continuous wave

SuperPulse

—

100

10 600 nm Nasal facial fold trichiasis

CO2 10 600 nm

Table C.6  Chapter 12: Ophthalmic lasers for the treatment of glaucoma.

Procedure

Laser type wavelength

Delivery system

Sites (°)

Power (mW)

Exposure

Duration (ms)

Energy (J)

Duty cycle (%)

ECP

Diode laser

1 mm × 30 mm

90–360

250 (100–1000)

To effect

—

100

810 nm

Endoscope

Continuous wave

mTSCP

Diode laser

MP3 probe

320–340

2000

Micropulse

18 000

12

33

TSCP

Diode laser

600 μm

24–55

1000–1500/site

1500–4000/site

2.5–4/site

810 nm

Glaucoma (“G”) probe

Continuous wave

810 nm 100

Table C.7  Chapter 13: Canine and feline dermatologic laser surgery procedures.

Procedure

Laser type wavelength

Actinic keratosis

Bowenoid in situ carcinoma

Spot size (mm)

Power (W)

Exposure

Mode

Frequency (Hz)

Duty cycle (%)

CO2

Wide ablation tip

 8

Repeat pulse

SuperPulse

20

40

10 600 nm

0.8 mm

 4

10

20

CO2

Wide ablation tip

10 600 nm

0.8 mm

12

Ceruminous (apocrine) cystomatosis

CO2

Wide ablation tip or 0.8 mm

12–25

External ear hyperplasia

CO2

12–25

10 600 nm

Wide ablation tip or 0.8 mm

Follicular cyst, interdigital

CO2 10 600 nm

Wide ablation tip

25

Repeat pulse

SuperPulse

10 600 nm

CO2

Wide ablation tip

10 600 nm Follicular tumors

CO2

Hamartomas

CO2

20–40 Repeat pulse

SuperPulse

29

Non‐SuperPulse

10–20

20–40

Repeat pulse

SuperPulse

29

73

Non‐SuperPulse

10–20

20–40

30–35

Continuous wave

Non‐SuperPulse

—

100

25–12

Repeat pulse

SuperPulse

29

73

10–20

30–50

29

73

 8  8

25–12

Repeat pulse

SuperPulse

0.25 mm

25

Repeat pulse

SuperPulse

Repeat pulse

SuperPulse

12 0.25 mm

10 600 nm

Wide ablation tip

CO2

Wide ablation tip

35

Squamous cell carcinoma

0004281502.INDD 350

20

40

29

73 73 73

20

40

29

73

15

20

60

10–20

20–60

SuperPulse

29

73

Non‐SuperPulse

20

40

SuperPulse

29

73

20

40

30

CO2

Wide ablation tip

30–35

10 600 nm

73

29

12

Repeat pulse

Repeat pulse

25–12 0.25 mm

40

29

20

0.8 mm

10 600 nm

10–20

20

10 600 nm

CO2

73

12 12

Sebaceous gland tumors

73 20

 8

10 600 nm

Pigmented viral plaques

40

20

12

12 Follicular cyst, elbow

 5

25 12

Repeat pulse

SuperPulse

3/12/2019 3:33:48 PM

Appendix C

Table C.8  Chapter 14: Canine and feline urogenital and perianal laser surgery procedures.

Procedure

Laser type wavelength

Spot size (mm)

Power (W)

Exposure

Mode

Frequency

Duty cycle (%)

Anal gland excision

CO2

0.25

10–15

Continuous wave

SuperPulse

—

100

10 600 nm

3–5

Cystotomy

CO2 10 600 nm

0.25

10

Continuous wave

SuperPulse

—

100

Orchiectomy, cryptorchid

CO2

0.25

10–15

Continuous wave

SuperPulse

—

100

Paraphimosis

CO2

0.25

10–15

Continuous wave

Non‐SuperPulse

—

100

0.25

15

Continuous wave

SuperPulse

—

100

0.25

15

Continuous wave

SuperPulse

—

100

0.25

10

Continuous wave

Non‐SuperPulse

—

100

0.25

15–20

Continuous wave

SuperPulse

—

100

0.25

15

Continuous wave

SuperPulse

—

100

CO2

0.25

15

SuperPulse

—

100

10 600 nm

Wide ablation tip

Continuous wave

10 600 nm 10 600 nm

Perineal urethrostomy, canine

CO2

5–8

10 600 nm

Perineal urethrostomy, feline

CO2

Prolapse, urethral

CO2

10

10 600 nm

10

10 600 nm Prolapse, vaginal

CO2 10 600 nm

Vasectomy, canine

CO2

15

10 600 nm Vulvoplasty, canine

Non‐SuperPulse Non‐SuperPulse

Non‐SuperPulse

Table C.9  Chapter 15: Canine and feline oncological laser surgery procedures. Laser type wavelength

Spot size

Power (W)

Exposure

Mode

Frequency

Duty cycle (%)

Cutaneous neoplasms (ablation)

CO2

0.8–1.4 mm

10 or more

—

100

3 mm wide ablation tip

Continuous wave

Non‐SuperPulse

10 600 nm

Cutaneous neoplasms (excision)

CO2

0.25–1.4 mm

10–15

100

(0.4 mm)

SuperPulse or non‐SuperPulse

—

10 600 nm

Continuous wave

Oral tumor (ablation)

CO2

0.4 mm defocused

10–15

Continuous wave

Non‐SuperPulse

—

100

10 600 nm

3 mm wide ablation tip

Oral tumor (excision)

CO2

0.25–1.4 mm

10–15

SuperPulse or non‐SuperPulse

100

(0.4 mm)

Continuous wave

—

10 600 nm

Subcutaneous neoplasms (lipoma, AGASACA)

CO2

0.25–1.4 mm

10–15

SuperPulse or non‐SuperPulse

100

(0.4 mm)

Continuous wave

—

10 600 nm

Thyroidectomy

CO2

0.25–1.4 mm

10–15

100

(0.4 mm)

SuperPulse or non‐SuperPulse

—

10 600 nm

Continuous wave

Procedure

351

352

Appendix C

Table C.10  Chapter 16: Canine and feline laser photodynamic therapy procedures.

Procedure

Laser type wavelength

Antimicrobial PDT

Diode (810 nm)

PDT of neoplasms

Diode (652 nm)

Drug‐to‐light interval

Power (mW)

Dose (J/cm2)

Treatment frequency

Methylene– violet–blue

5 min

500

10–100

1 wk−1

mTHPC

6 h

500

10–30 (non‐contact)

1 mo−1

Fiber diameter

Photosensitizer

400–600 μm microlens 400–600 μm microlens

30 (contact)

Table C.11  Chapter 17: Surgical lasers in minimally invasive and endoscopic small animal procedures.a

Procedure

Aural mass resection and ablation Ectopic ureter correction

Laser type wavelength

Power (W)

Frequency

Energy (J)

Dependent on otoscope

10–12

Continuous wave

a

Contact

Diode

325 μm sculpted, pointed tip

Up to 10

Short cycle

0.5–0.8

Contact

810 or 980 nm

Right‐angled firing fiber

Ho:YAG

Dependent on endoscope

a

8–10 Hz

1.2

Contact

Dependent on endoscope

12–15

5000–2000 Hz

a

Contact

a

4–10 Hz

0.8–1.7

Non‐contact

10–12

Long cycle

a

a

810 or 980 nm

Dependent on endoscope

Ho:YAG

550 μm

Up to 18

Long cycle

1.2

a

325 μm

8–12

15 Hz

0.5–0.8

a

Dependent on endoscope

Up to 12

Up to 20 000 Hz

a

Contact

Maximum allowed by endoscope

15

Short cycle

a

Contact and non‐contact

8–10

a

a

a

Diode 810 or 980 nm

2100 nm Endobronchial mass resection

Diode 810 or 980 nm

Fiber diameter

Ho:YAG

Contact technique

2100 nm Esophageal mass debulking

Diode

2100 nm Esophageal stricture resection

Ho:YAG

Everted laryngeal Saccule resection

Diode 810 or 980 nm

Gastric mass debulking

Diode

2100 nm

810 nm Gastric mass resection

Diode 810 or 980 nm

Maximum allowed by endoscope

Lithotripsy

Ho:YAG

325–550 μm

a

8–15 Hz

1.2–2

Contact or non‐contact

Myringotomy

Diode

325 μm or less