Fundamental Principles of Veterinary Anesthesia E-Book
76,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Fundamental Principles of Veterinary Anesthesia Comprehensive textbook integrating physiology and anesthesia of multiple species of animals in a unique practical setting Fundamental Principles of Veterinary Anesthesia is designed specifically for veterinary students, animal health technicians and veterinarians in general practice. The first edition of Fundamental Principles of Veterinary Anesthesia covers the key principles of veterinary anesthesia, encompassing a wide range of species, including dogs, cats, horses, cattle, and pigs, and establishing links between physiology, pharmacology, and clinical practice in healthy and ill patients. This text serves as a practical guide for students to prepare themselves for clinical work in a private practice setting, and as a rich, practical resource for those in general practice. This text is ideally used as a complete curriculum aligned resource, and the companion website is designed to decrease the burden of lecturers who need to compile PowerPoint presentations and review questions. Topics covered in Fundamental Principles of Veterinary Anesthesia include: * Practical approaches to the peri-anesthetic period, from patient assessment, through to preparing for, and successfully completing, an anesthetic event * Anesthetic drugs available in an academic or private practice, with a focus on commonly used drugs * Components of the anesthetic machine, gas flow through the machine, how vaporizers work and their functionalities * Principles and techniques of patient monitoring, with a focus on commonly available devices and their applications
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 1301
Veröffentlichungsjahr: 2024
Ähnliche
Fundamental Principles of Veterinary Anesthesia
Edited by
Gareth E. Zeiler
Valley Farm Animal Hospital,PretoriaandUniversity of PretoriaSouth Africa
Daniel S. J. Pang
University of CalgaryCanada
This edition first published 2024
© 2024 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 Gareth E. Zeiler and Daniel S. J. Pang to be identified as the authors of the editorial material in this work has been asserted in accordance with law.
Registered Office
John Wiley & Sons, Inc., 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.
Trademarks: Wiley and the Wiley logo are trademarks or registered trademarks of John Wiley & Sons, Inc., and/or its affiliates in the United States and other countries and may not be used without written permission. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc., is not associated with any product or vendor mentioned in this book.
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. 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. 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. 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.
A catalogue record for this book is available from the Library of Congress
Paperback ISBN: 9781119791249; ePub ISBN: 9781119791270; ePDF ISBN: 9781119791300
Cover Images: © Vlad Klok/Shutterstock Gareth E. Zeiler -Author Provided Image © Igor Djurovic/iStock/Getty Images
Cover Design: Wiley
Set in 9.5/12.5pt STIXTwoText by Integra Software Services Pvt. Ltd, Pondicherry, India
To BJZ and SJZ for their patience, understanding, and encouragement during the creation of this textbook, and to all my colleagues (especially LB, GFS, BTD, LCRM, and ERG) who taught me anesthesia and scientific writing, completed research projects together, and helped train the next generation in anesthesia. What a ride!
Gareth Zeiler
To J, for her support, kindness, and patience, and to all the clinicians, researchers, technicians, and residents who have taught me the art and science of anesthesia (DF, SC, ET, YR, NF, JL, CB, JK, GD, FRB, and MR).
Daniel Pang
Contents
Cover
Title Page
Copyright Page
Dedication Page
Contributors
Preface
Glossary
About the Companion Website
Section 1 Foundational Knowledge
1 Veterinary Anesthesia
2 Patient Assessment, Planning, and Preparation
3 Pain Physiology, Assessment, and Principles of Treatment
4 Principles of Anesthetic Monitoring and Monitoring Equipment
5 Inhalation Anesthetic Delivery Apparatus
6 Introduction to Pharmacology and Pharmacotherapy
7 Injectable Drugs Used for Premedication, Induction, and Maintenance of General Anesthesia
8 Inhalational Anesthetic Drugs
9 Nonsteroidal Anti-inflammatory Drugs, Local Anesthetic Drugs, and Adjunct Drugs Used for Pain Management
10 Other Drugs Used During the Peri-anesthetic Period
Section 2 Fundamental Aspects of Clinical Anesthesia
11 Standards of Practice for Performing Veterinary Anesthesia
12 Approach to Healthy Dog and Cat Anesthesia and Analgesia, and Selected Disease Processes and Procedures
13 Approach to Healthy Horse, Donkey, and Mule Anesthesia and Analgesia
14 Anesthesia and Analgesia of Healthy Exotic Companion Mammals, Ruminants, and Pigs
15 Approach to Neonatal, Pediatric, and Geriatric Patients
16 Approach to a Patient in Shock
17 Approach to a Patient with Cardiac Pathology
18 Approach to a Patient with Respiratory Pathology
19 Approach to a Patient with Renal, Urinary, or Hepatobiliary Disease
20 Anesthetic Complications and Cardiopulmonary Resuscitation
Appendix 1: RECOVER CPR Algorithms
Appendix 2: RECOVER CPR Emergency Drug Dose Charts
Appendix 3: Checklists
Appendix 4: Peri-anesthetic Monitoring Sheets
Index
End User License Agreement
List of Tables
CHAPTER 01
Table 1.1 A list of some...
CHAPTER 02
Table 2.1 Normal reference...
Table 2.2 Normal reference...
Table 2.3 American Society...
Table 2.4 Physiological variables...
Table 2.5 Characteristics...
Table 2.6 Fluid therapy...
Table 2.7 Indications and...
Table 2.8 Current guidelines...
CHAPTER 03
Table 3.1 Tools developed...
Table 3.2 Unidimensional...
Table 3.3 Examples of...
CHAPTER 04
Table 4.1 Evaluation...
Table 4.2 Pulse oximetry...
Table 4.3 Examples of...
Table 4.4 Methods of...
CHAPTER 05
Table 5.1 Advantages...
Table 5.2 The fundamental...
Table 5.3 Characteristics...
Table 5.4 Color conventions...
Table 5.5 The relationship...
Table 5.6 Classification...
Table 5.7 Checkout procedures...
CHAPTER 06
Table 6.1 Examples of...
Table 6.2 Examples of...
Table 6.3 Acceptable...
CHAPTER 08
Table 8.1 Vapor pressure...
Table 8.2 The minimum...
Table 8.3 Factors that...
CHAPTER 09
Table 9.1 Physiologic...
Table 9.2 Nonsteroidal...
Table 9.3 Physiochemical...
Table 9.4 Patient factors...
Table 9.5 Typical duration...
Table 9.6 Additives for...
CHAPTER 10
Table 10.1 Summary of...
Table 10.2 Summary of...
Table 10.3 The Vaughn–Williams...
Table 10.4 Commonly used...
Table 10.5 Summary of different...
Table 10.6 Recommendations...
Table 10.7 Nutraceuticals...
Table 10.8 Nutraceuticals...
Table 10.9 Nutraceuticals...
Table 10.10 Animal-based...
Table 10.11 Nutraceuticals...
CHAPTER 11
Table 11.1 Allowable Animal...
Table 11.2 AVA guidelines...
CHAPTER 12
Table 12.1 Procedural...
Table 12.2 Common types...
Table 12.3 Size chart to...
Table 12.4 Procedure of...
Table 12.5 Examples of...
Table 12.6 Examples of...
Table 12.7 Peri-anesthetic...
CHAPTER 13
Table 13.1 Nonsteroidal...
Table 13.2 Examples of...
Table 13.3 Drugs for...
Table 13.4 Drugs for...
CHAPTER 14
Table 14.1 Drugs and doses...
Table 14.2 Peri-anesthetic...
Table 14.3 Legislation...
Table 14.4 Recommended...
Table 14.5 Examples of...
Table 14.6 Recommended...
Table 14.7 General anesthetic...
Table 14.8 Selected local...
CHAPTER 15
Table 15.1 Consequences...
Table 15.2 Normal levels...
Table 15.3 Suggested doses...
Table 15.4 Suggested doses...
Table 15.5 Suggested doses...
Table 15.6 Suggested doses...
Table 15.7 Lower acceptable...
Table 15.8 Consequences...
Table 15.9 Common drug...
Table 15.10 Suggested...
Table 15.11 Suggested...
CHAPTER 16
Table 16.1 Intravenous...
Table 16.2 Synthetic...
Table 16.3 Natural colloids...
Table 16.4 Blood types...
Table 16.5 Commercial...
Table 16.6 Drugs used...
Table 16.7 Drugs used...
Table 16.8 Drug options...
CHAPTER 17
Table 17.1 Grading of...
Table 17.2 Summary table...
Table 17.3 Example protocols...
Table 17.4 Normal resting...
Table 17.5 Common arrhythmias...
CHAPTER 18
Table 18.1 Drugs commonly...
Table 18.2 Strategies...
Table 18.3 Strategies...
Table 18.4 Causes of...
Table 18.5 Causes of...
Table 18.6 Principles...
Table 18.7 Observations...
CHAPTER 19
Table 19.1 Drugs commonly...
Table 19.2 A summary of...
Table 19.3 Drugs commonly...
CHAPTER 20
Table 20.1 The causes of...
List of Illustrations
CHAPTER 01
Figure 1.1 The three major...
Figure 1.2 The hypothetical...
Figure 1.3 Hierarchy of...
CHAPTER 02
Figure 2.1 Examples of...
Figure 2.2 The total body...
CHAPTER 03
Figure 3.1 Overview of the...
Figure 3.2 Laminae of the...
Figure 3.3 Modulation of...
CHAPTER 04
Figure 4.1 Eye rotation...
Figure 4.2 Different mucous...
Figure 4.3 Placement of...
Figure 4.4 Doppler probe...
Figure 4.5 A Doppler probe...
Figure 4.6 Oscillometric...
Figure 4.7 Invasive blood...
Figure 4.8 An affordable...
Figure 4.9 Capnograph waveforms...
Figure 4.10 Examples of capnograph...
Figure 4.11 Some physiologic...
Figure 4.12 Peripheral...
Figure 4.13 A dog under...
Figure 4.14 A nine-year-old, male,...
CHAPTER 05
Figure 5.1 Examples of Inhalational...
Figure 5.2 Schematic of the...
Figure 5.3 The relationship...
Figure 5.4 Centralized bulk...
Figure 5.5 Examples of portable...
Figure 5.6 The gas circuitry...
Figure 5.7 An oxygen bottle...
Figure 5.8 Various types of...
Figure 5.9 Serial photographs...
Figure 5.10 Schematic drawings...
Figure 5.11 Mapleson Type...
Figure 5.12 The Mapleson...
Figure 5.13 The rebreathing...
Figure 5.14 Examples of...
Figure 5.15 A schematic...
Figure 5.16 Examples of...
Figure 5.17 Three different...
Figure 5.18 Examples of...
Figure 5.19 A schematic...
Figure 5.20 Photographs...
Figure 5.21 All waste gas...
CHAPTER 06
Figure 6.1 A concentration–time...
Figure 6.2 A concentration–time...
Figure 6.3 Different 1 mL...
Figure 6.4 A stepwise photo...
Figure 6.5 A collection of...
Figure 6.6 A capsule before...
CHAPTER 08
Figure 8.1 Impact of fresh...
Figure 8.2 The impact of...
Figure 8.3 Relationship...
Figure 8.4 Harbor seal...
CHAPTER 09
Figure 9.1 A flow diagram...
Figure 9.2 The chemical...
CHAPTER 10
Figure 10.1 Antimicrobial...
CHAPTER 12
Figure 12.1 Intravenous...
Figure 12.2 Other sites of...
Figure 12.3 The anatomy of...
Figure 12.4 Endotracheal...
Figure 12.5 Various lignocaine...
Figure 12.6 The procedure...
Figure 12.7 Cats are prone...
Figure 12.8 The tip (bevel)...
Figure 12.9 The ischiatic...
Figure 12.10 Epidural injections...
Figure 12.11 The epidural...
Figure 12.12 Collage of...
Figure 12.13 The uterus...
Figure 12.14 Sequential...
Figure 12.15 A cat that...
Figure 12.16 Obtaining a...
CHAPTER 13
Figure 13.1 An intravenous...
Figure 13.2 Surgery can...
Figure 13.3 Electrocardiogram...
Figure 13.4 A deeply sedated...
Figure 13.5 Deeply sedated...
Figure 13.6 A pressure bag...
Figure 13.7 Orotracheal...
Figure 13.8 Nasotracheal...
Figure 13.9 Considerations...
Figure 13.10 The in-hospital...
CHAPTER 14
Figure 14.1 Collage of exotic...
Figure 14.2 Performing an...
Figure 14.3 Flow diagram to...
Figure 14.4 Equipment used to...
Figure 14.5 A decision flowchart...
Figure 14.6 A dental rack can be...
Figure 14.7 Tracheal intubation...
Figure 14.8 Left: Two different...
Figure 14.9 Different sizes...
Figure 14.10 Photograph illustrating...
Figure 14.11 Photograph of a...
Figure 14.12 Needle and syringe...
Figure 14.13 Head positioning in...
Figure 14.14 Photographs showing...
Figure 14.15 Photographs showing...
Figure 14.16 Photographs showing...
CHAPTER 15
Figure 15.1 The body composition...
Figure 15.2 Normal cardiac...
Figure 15.3 A right lateral...
Figure 15.4 Different methods of...
Figure 15.5 Examples of different...
Figure 15.6 Nasotracheal intubation...
Figure 15.7 The body composition...
CHAPTER 16
Figure 16.1 Variation in...
Figure 16.2 The relationship...
Figure 16.3 Total body water...
CHAPTER 17
Figure 17.1 Normal cardiac...
Figure 17.2 S–T segment...
Figure 17.3 The American College...
Figure 17.4 Pathophysiology of...
Figure 17.5 Pathophysiology of...
Figure 17.6 Pathophysiology of...
CHAPTER 18
Figure 18.1 A decision flow diagram...
Figure 18.2 Examples of dogs and...
Figure 18.3 The Hagen...
Figure 18.4 Photos of the tongue...
Figure 18.5 The oxygen...
Figure 18.6 The five causes...
Figure 18.7 The effect of...
Figure 18.8 The effect of...
Figure 18.9 Different types...
Figure 18.10 Relationship...
Figure 18.11 Right lateral...
Figure 18.12 (a, b) Normal...
Figure 18.13 Left (a) and...
Figure 18.14 Examples of...
Figure 18.15 Series of left...
Figure 18.16 Left lateral...
Figure 18.17 Left lateral...
Figure 18.18 Right lateral...
Figure 18.19 Right lateral...
CHAPTER 19
Figure 19.1 A right lateral...
Figure 19.2 A human urine dip...
Figure 19.3 The mucous membrane...
Figure 19.4 Right abdominal...
CHAPTER 20
Figure 20.1 Reason’s...
Figure 20.2 Pre-induction...
Figure 20.3 Fishbone...
Figure 20.4 An emergency...
Figure 20.5 Photograph...
Figure 20.6 The four...
Figure 20.7 Basic life...
Figure 20.8 Techniques of...
Figure 20.9 Advanced life...
Figure 20.10 Post-cardiac...
Figure 20.11 External chest...
Figure 20.12 The resuscitator...
Figure 20.13 A demand valve...
Guide
Cover
Title Page
Copyright Page
Dedication Page
Table of Contents
Contributors
Preface
Glossary
About the Companion Website
Begin Reading
Appendix 1: RECOVER CPR Algorithms
Appendix 2: RECOVER CPR Emergency Drug Dose Charts
Appendix 3: Checklists
Appendix 4: Peri-anesthetic Monitoring Sheets
Index
End User License Agreement
Pages
i
ii
iii
iv
v
vi
vii
viii
ix
x
xi
xii
xiii
xiv
xv
xvi
xvii
xviii
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
Contributors
This textbook was written by 27 authors from nine countries with a range of different specializations and working at university hospitals or in private practice.
Abdur R. Kadwa
BSc (Vet Bio), BVSc, MMedVet (Anaesthesiology), Diplomate ECVAA
Senior Lecturer
Affiliation 1: Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria
Alicia M. Skelding
BScAgr, DVM, MSc, DVSc, Diplomate ACVAA
Assistant Professor, Veterinary Anesthesia
Affiliation 1: Michigan State University College of Veterinary Medicine
Benjamin M. Brainard
VMD, Diplomate ACVAA, Diplomate ACVECC
Edward H Gunst Professor of Small Animal Critical Care and Director of Clinical Research
Affiliation 1: College of Veterinary Medicine, University of Georgia
Carolyn Kerr
DVM, DVSc, PhD, Diplomate ACVAA
Professor
Affiliation 1: Department of Clinical Studies, Ontario Veterinary College, University of Guelph
Chantal McMillan
DVM, MVSc, Diplomate ACVIM
Senior Instructor
Affiliation 1: Faculty of Veterinary Medicine, University of Calgary
Daniel S. J. Pang
BVSc, PhD, Diplomate ACVAA, Diplomate ECVAA FRCVS
Professor
Affiliation 1: Faculty of Veterinary Medicine, University of Calgary
Affiliation 2: Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal
Eugene P. Steffey
VMD, PhD, Diplomate ACVAA, Diplomate ECVAA (retired)
Emeritus Professor (University of California, Davis)
Affiliation 1: Department of Surgical and Radiological Sciences, University of California, Davis
Affiliation 2: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University
Gareth E. Zeiler
BVSc (Hons), MMedVet (Anaesthesiology), PhD (UP), PhD (WITS), Diplomate ECVAA, Diplomate ACVAA, Diplomate ECVECC
Head of Anaesthesia and Critical Care Services and Extraordinary Lecturer
Affiliation 1: Valley Farm Animal Hospital, Pretoria, Gauteng
Affiliation 2: Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria
H. Nicole Trenholme
DVM, MS, Diplomate ACVECC, Diplomate ACVAA
Medical director, Head of services for emergency and critical care as well as anesthesia
Affiliation 1: Evolution Veterinary Specialty and Emergency Hospital, Lakewood, CO, United States
Affiliation 2: Adjunct Professor, Department of Veterinary Clinical Medicine and Veterinary Teaching Hospital, University of Illinois College of Veterinary Medicine
Hugo van Oostrom
DVM, PhD, Diplomate ECVAA
Head of Anaesthesia Services
Affiliation 1: IVC Evidensia The Netherlands
Jo Murrell
BVSc (hons), PhD, Diplomate ECVAA, MRCVS
Clinical Anesthesiologist
Affiliation 1: Highcroft Veterinary Referrals
John A.E. Hubbell
DVM, MSc, Diplomate ACVAA
Chief of Anesthesia Service and Emeritus Professor
Affiliation 1: Rood and Riddle Equine Hospital
Affiliation 2: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University
Jonathan Lichtenberger
DVM, MSc, Diplomate ACVIM (Cardiology)
Board-certified Veterinary Cardiologist and Founder of Pacific Coast Veterinary Cardiology
Affiliation 1: Pacific Coast Veterinary Cardiology
Justin F. Grace
BVSc, MMedVet (Anaesthesiology), MRCVS
Senior Lecturer
Affiliation 1: Sydney School of Veterinary Science, University of Sydney 2006, Australia
Affiliation 2: Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria
Keagan J. Boustead
BVSc, MSc, Diplomate ECVAA
Clinical Anesthesiologist
Affiliation 1: Westville Veterinary Hospital, Durban, KwaZulu Natal
Affiliation 2: Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria
Khursheed Mama
DVM, Diplomate ACVAA
Professor
Affiliation 1: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University
Matthew Gurney
BVSc, CertVA, PgCertVBM, Diplomate ECVAA, FRCVS
Anesthesiologist
Affiliation 1: Anderson Moores Veterinary Specialists
Affiliation 2: The Zero Pain Philosophy
Nigel Caulkett
DVM, MVetSci, Diplomate ACVAA
Professor
Affiliation 1: Faculty of Veterinary Medicine, University of Calgary
Nora Matthews
DVM, Diplomate ACVAA
Emeritus Professor
Affiliation 1: Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University
Pamela J. Murison
BVMs, PhD, Diplomate ECVAA, DVA, FHEA, MRCVS
Professor
Affiliation 1: School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow
Robert E. Meyer
DVM, Diplomate ACVAA (Emeritus)
Emeritus Professor
Affiliation 1: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University
Roxanne K. Buck
BVSc, MSc, MMedVet (Anaesthesiology), PhD, Diplomate ECVAA
Clinical Anesthesiologist
Affiliation 1: Department of Clinical Studies, Ontario Veterinary College, University of Guelph
Affiliation 2: Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria
Sabine B.R. Kästner
Prof. Dr. Med. Vet., MVetSci, Diplomate ECVAA
Professor
Affiliation 1: Department of Anaesthesia and Analgesia, Clinic for Small Animals, University of Veterinary Medicine Hannover
Samantha Swisher
DVM, MPH, DABVP (Exotic Companion Mammal), DACVPM
Exotic companion mammal specialist and resident in veterinary public health
Affiliation 1: Department of Veterinary Preventive Medicine, The Ohio State University College of Veterinary Medicine
Stijn Schauvliege
DVM, PhD, Diplomate ECVAA
Associate Professor
Affiliation 1: Department of Large Animal Surgery, Anaesthesia and Orthopaedics, Faculty of Veterinary Medicine, Ghent University
Tamara Grubb
DVM, PhD, Diplomate ACVAA
Anesthesiologist
Affiliation 1: International Veterinary Academy of Pain Management (President-Elect)
Affiliation 2: Veterinary Anesthesia, Analgesia and Continuing Education Services
Tim Bosmans
DVM, PhD
Anesthesiologist
Affiliation 1: Section of Anaesthesiology and Analgesia, Small Animal Department, Faculty of Veterinary Medicine, Ghent University
Preface
Providing anesthesia with appropriate patient care, including pre-anesthetic assessment, stabilization (as necessary), monitoring and management of physiologic variables, and a smooth recovery, is a fundamental skill, essential to facilitate a wide range of procedures. Nonetheless, we are aware that anesthesia can be daunting when faced with the many options available for drugs and equipment, and specific patient and procedure considerations.
Our goal in this book is to provide practical, accessible guidance on how to anesthetize frequently encountered companion, farm, and exotic species. We hope that it proves useful to veterinarians in general practice, those in their final years of veterinary study, and veterinary technicians (nurses). The material presented is intended to support and complement content covered in veterinary anesthesia courses and veterinary technician training. We are particularly pleased with the large number of figures presented in support of the text and complementary online resources.
Chapters are organized to cover general considerations applicable to all patients, with species-specific chapters describing anesthetic approaches in healthy and sick animals. Each chapter ends with questions to test the reader’s knowledge and understanding, with more questions available online.
As this is not intended to be an exhaustive reference textbook, we have intentionally limited lists of references to key articles for interested readers or to highlight more controversial areas.
We are indebted to the many co-authors who made this book possible. They have been generous in sharing their knowledge, experience and expertise, and have been patient with our many questions and numerous revisions as we strove to create the book we envisioned.
Every effort has been made to confirm accuracy of the text.
Gareth Zeiler and Daniel Pang
Glossary
Analgesia is defined as the inability to feel pain (https://www.iasp-pain.org/resources/terminology).
Anesthesia (as in general anesthesia) is defined as a state of drug-induced, controlled, and temporary loss of awareness that is induced for medical purposes.
Anesthetist is the person managing the anesthetic. This includes one or more of the following: administering the anesthetic, monitoring the patient, recording monitored variables, and providing analgesia. An anesthetist could be a veterinarian or a veterinary technician in the context of veterinary anesthesia. Note: The role of technicians will vary according to local regulations.
Anesthesiologist, though not strictly defined, it is generally accepted that the term is restricted to a veterinarian, and it is often, though not always, assumed that they have achieved specialist status, as recognized by their country’s veterinary professional body or by a specialty college.
Anxiolysis is defined as the reduction of anxiety.
Induction of general anesthesia describes the transition from a conscious state to an unconsciousness state (general anesthesia, as defined earlier).
Local anesthesia is defined as administering a local anesthetic drug, using various techniques, to induce the absence of sensation in a specific part of the animal’s body. Generally, the aim of inducing local anesthesia is to provide a local insensitivity to pain but often other local senses (feeling of sensations such as touch, heat, pressure, etc.) may also be lost.
Maintenance of general anesthesia is the phase of the anesthetic during which a stable plane of anesthesia and analgesia is maintained, and physiologic variables are ideally maintained within species-specific reference intervals to preserve optimal respiratory and hemodynamic stability.
Nociception is defined as the neural process of encoding noxious stimuli. The encoding may be autonomic (e.g., elevated blood pressure) or behavioral (e.g., motor withdrawal reflex). A sensation of pain is not necessarily implied (https://www.iasp-pain.org/resources/terminology).
Pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. An inability to communicate does not negate the possibility that an animal is experiencing pain (https://www.iasp-pain.org/resources/terminology).
Premedication is when drugs are administered alone, or in combination, to the patient before induction of general anesthesia. A sufficient time is necessary for these drugs to take effect before induction. This time period is typically around 15–20 min following intramuscular administration.
Recovery comprises the period from the end of anesthesia (stopping delivery of anesthetic drugs) to the return of consciousness and recovery of physiologic function.
Sedation describes a drug-induced decreased level of consciousness, from an awake state to a sleepy, but rousable, state.
About the Companion Website
This book is accompanied by a companion website which includes a number of resources created by author
for students and instructors that you will find helpful.
www.wiley.com/go/VeterinaryAnesthesiaZeiler
The Instructor website includes the following resources for each chapter:
Extra questions and answers
PowerPoint presentation templates
Figures of the textbook
Section 1 Foundational Knowledge
1 Veterinary Anesthesia
Gareth Zeiler and Daniel Pang
Introduction to Veterinary Anesthesia
Veterinary anesthesia is a fundamental discipline within the broad field of veterinary medicine that deals with anesthesia (local and general) and analgesia of all animals. Many aspects of veterinary anesthesia directly relate to the aims of an oath of ethics (oaths or credos are country dependent) that a veterinarian or veterinary technician (nurse) must take before being allowed to practice veterinary medicine. An example of such an oath is the American Veterinary Medical Association Veterinarian’s Oath:
“Being admitted to the profession of veterinary medicine, I solemnly swear to use my scientific knowledge and skills for the benefit of society through the protection of animal health and welfare, the prevention and relief of animal suffering, the conservation of animal resources, the promotion of public health, and the advancement of medical knowledge.
I will practice my profession conscientiously, with dignity, and in keeping with the principles of veterinary medical ethics.
I accept as a lifelong obligation the continual improvement of my professional knowledge and competence.”
Furthermore, many of these oaths address the five freedoms of animal welfare, which are as follows: the freedom (1) from hunger and thirst, (2) from discomfort, (3) from pain, injury and disease, (4) to express normal behavior, and (5) from fear and distress. Specifically, practicing anesthesia and providing analgesia in animals facilitates a wide range of procedures (e.g., surgery and many diagnostic imaging procedures) and prevents discomfort and pain. Furthermore, for example, treating painful age-related disease processes, such as providing analgesia to an old dog suffering debilitating osteoarthritis, addresses the freedom to express normal behavior. Pain-free animals are also more likely to eat and drink which addresses the freedom from thirst and hunger. Thus, the practice of veterinary anesthesia can address all freedoms, enabling veterinarians and technicians to meet their ethical obligation to uphold their oath.
Anesthesia (as in general anesthesia) is defined as a state of controlled, temporary loss of sensation or awareness that is induced for medical purposes.
Local anesthesia is defined as administering a local anesthetic drug, using various techniques, to induce the absence of sensation in a specific part of the animal’s body. Generally, the aim of inducing local anesthesia is to provide a local insensitivity to pain but often other local senses (feeling of sensations such as touch, heat, pressure, etc.) may also be lost.
Analgesia is defined as the inability to feel pain. However, many drugs that are used to treat pain (opioids, nonsteroidal anti-inflammatory drugs, etc.) are more accurately described as “hypoalgesics,” as they decrease the sensation of pain rather than abolishing it completely. Local anesthetic drugs provide loss of sensation and are thus considered true analgesics.
The anesthetist is the person administering the anesthetic and providing analgesia. An anesthetist could be a veterinarian or a veterinary technician. Note: The role of technicians will vary according to local regulations.
Though not strictly defined, it is generally accepted that the term “anesthesiologist” is restricted to a veterinarian, and it is often, though not always, assumed that they have completed postgraduate, discipline-specific clinical training and are registered by their country’s veterinary professional body, or board-certified by a college, conferring specialist status as a veterinary anesthesiologist.
The Stages of Learning and Developing Skills in Veterinary Anesthesia
There are three major areas that require development to become proficient at practicing anesthesia and analgesia (Figure 1.1). These are focused on (1) your development (knowledge and practice of anesthesia, to achieve proficiency as a new graduate through practice and situational awareness), (2) understanding your patient, and (3) understanding the drugs.
Figure 1.1 The three major fields that require development to become proficient at practicing anesthesia and analgesia. These fields are focused on your development, your understanding of the patient, and an understanding of the drugs used during the peri-anesthetic period.
Your development begins with building your knowledge and understanding. This involves enrolling into a veterinary degree course where fundamental aspects of veterinary anesthesia are taught in a classroom environment. At this early stage of development, you are classified as a novice on the learning and development staircase framework (Figure 1.2). Many of the aspects of veterinary anesthesia will be foreign to you because you have not necessarily been exposed to clinical practice. This makes the initial learning of this subject a challenge. As you progress through classroom learning, some faculties have a skills laboratory where you will be exposed to the practical aspects of performing certain procedures on purpose-built training models (simulators). Once that phase of learning is completed you are considered an apprentice and you will be ready for clinical training with live patients (academic hospitals or at private practice rotation programs, depending on your school). During this period of training, you will gain practical experience and begin to develop your skill set while applying the theory from the classroom. Upon graduation from the veterinary program, you are considered proficient at veterinary anesthesia.
Figure 1.2 The hypothetical learning and development staircase that starts in the lecture halls (A), graduating from a degree in veterinary science (C), and then specializing in veterinary anesthesia (D and E).
Over and above learning the fundamental principles of veterinary anesthesia is the need to incorporate knowledge gained from other courses, such as physiology (species-specific and disease pathophysiology). Understanding and integrating this knowledge is essential to practicing anesthesia at an acceptable level. In most anesthesia courses, there is not enough time to review physiology and pathophysiology so it is therefore expected that a student recalls and integrates this knowledge during the course. This also applies to the core concepts of pharmacology (such as receptor function and location, and principles of pharmacokinetics and pharmacodynamics).
Colleges and Associations
There are a number of colleges and academies where a veterinarian or veterinary technician can enroll for postgraduate training with the goal of becoming a specialist. Acquiring this status will classify you as an expert (specialist) in veterinary anesthesiology. The differentiation between expert and master is not formally structured, but Diplomates would be expected to achieve master status with experience. However, veterinarians or veterinary technicians who have a keen interest in anesthesiology but do not want to pursue a specialist degree can join an association to keep up to date with developments in the field or gain additional knowledge at their own pace and level of interest. Table 1.1 lists a few internationally recognized organizations that offer specialist training or information to interested persons. Your country may offer some regional organizations where advanced training or information can be found; it is best to consult your local associations or schools for information.
Table 1.1 A list of some internationally recognized organizations that offer specialist training in veterinary anesthesia or provide a source of information to an interested person.
Entity
Criteria for membership
Description
Website
ACVAA
Membership requires diplomate status. Diplomate status is achieved by completing a residency and passing the board-certifying examination.
The American College of Veterinary Anesthesia and Analgesia. The ACVAA exists to promote the highest standards of clinical practice of veterinary anesthesia and analgesia and defines criteria for designating veterinarians with advanced training as specialists in the clinical practice of veterinary anesthesiology. The ACVAA issues certificates to those meeting these criteria, maintains a list of such veterinarians, and advances scientific research and education in veterinary anesthesiology and analgesia.
www.acvaa.org
ECVAA
Membership requires diplomate status. Diplomate status is achieved by completing a residency and passing the board-certifying examination.
The European College of Veterinary Anaesthesia and Analgesia. The mission of the ECVAA is to contribute significantly to the maintenance and enhancement of the quality of European Veterinary Specialists in Anaesthesia and Analgesia across all European countries at the highest possible level so as to ensure that improved veterinary medical services will be provided to the public.
www.ecvaa.org
AVTAA
Veterinary technician specialist (anesthesia and analgesia) status is achieved by completing credentials and passing a certifying examination.
The Academy of Veterinary Technicians in Anesthesia and Analgesia. The AVTAA exists to promote interest in the discipline of veterinary anesthesia. The Academy provides a process by which a veterinary technician may become credentialed as a Veterinary Technician Specialist (Anesthesia and Analgesia). The Academy provides the opportunity for members to enhance their knowledge and skills in the field of veterinary anesthesia.
www.avtaa-vts.org
AVA
All professions and animal caregivers with an interest in veterinary anesthesia, analgesia, and associated animal welfare can join the association.
The Association of Veterinary Anaesthetists. The AVA is an active, enthusiastic group of veterinary surgeons and others (e.g., researchers, technicians, and pharmacologists) who share an interest in animal anesthesia, analgesia, and animal welfare. The AVA promotes the study of, and research into, the subject of anesthesia and analgesia in animals; and to promote collaboration between anesthetists in all places, and actively encourage the establishment and taking of diplomas and degrees in veterinary anesthesia.
www.ava.eu.com
NAVAS
All professions and animal caregivers with an interest in veterinary anesthesia, analgesia, and associated animal welfare can join the society.
The North American Veterinary Anesthesia Society. The NAVAS helps veterinary professionals and caregivers advance and improve the safe administration of anesthesia and analgesia to all animals through development of standards consistent with recent findings documented in high-quality basic and clinical scientific publications and texts. The NAVAS encourages discussion and disseminates information to all those interested in veterinary anesthesia and analgesia, including the general public. The NAVAS strives to be a community of, and an accessible resource for, all veterinary caregivers and interested individuals within the general public on matters relevant to veterinary anesthesia, analgesia, and related animal welfare.
www.mynavas.org
Referral and Advice Considerations
There are specialists in veterinary anesthesiology all over the world who will accept a case referral or be prepared to consult on a case if physical referral is not an option. The ACVAA and ECVAA websites have directories listing board-certified veterinary anesthesiologists. If that approach is unsuccessful, then phoning your local region’s registering body or association could be helpful.
When to Consider Referral
A good rule of thumb is to consider the predicted risk of peri-anesthetic mortality for the patient’s physical status classification (see Chapter 2 for a description of the American Society of Anesthesiologists physical status classification). As physical status classification increases, the risk of mortality increases. A further consideration is veterinarian familiarity with the species to be anesthetized. For example, it is not unreasonable to consider that a veterinarian who primarily works with cats and dogs will be less proficient anesthetizing a pet reptile. This lack of familiarity will increase the anesthetic risk as it is likely to impact the quality of anesthetic management. Another consideration for referral is access to a specialist. Some anesthesiologists are prepared to travel and assist with a case at your practice.
Asking for Advice when Referral Is Not an Option
While referral may not always be an option, with potential financial and geographic limitations, modern communications increase the options available for specialist consultation, such as teleconsulting/telemedicine. Other sources of free advice can be found on professional networks (often hosted by associations and controlling bodies), invited email lists (ACVA-L), social media groups (e.g., interest groups on Facebook), and in some cases anesthesiologists employed at local veterinary specialty/academic hospitals. Information provided by those without recognized advanced training is not subject to any form of quality control and practitioners should be aware of the associated risks.
Interpreting the Science
How to Find Quality Information in a Hurry
When looking for information quickly most of us turn to an internet search engine; however, information available on websites is often inaccurate and incomplete. This explains the commonly held misconception that there are a large number of dog and cat breeds that are especially “sensitive” to anesthetic drugs (see Further Reading). Unfortunately, distinguishing between reliable and unreliable sources may not be obvious. A helpful approach is to examine the credentials of the person/group providing information. At an individual level, only Diplomates of the American College of Veterinary Anesthesia and Analgesia or European College of Veterinary Anaesthesia and Analgesia are entitled to use the post-nominal “DACVAA” or “DECVAA,” respectively. The terms “specialist,” “anesthetist,” and “anesthesiologist” can be misleading as these are not necessarily defined or protected terms in all countries. Any association or group producing anesthesia resources should include Diplomates within its membership. Such groups include the ACVAA, ECVAA, and the Association of Veterinary Anaesthetists and Continental/National Anesthesia Associations (e.g., NAVAS, North American Veterinary Anesthesia Society).
Evaluating Scientific Articles
A detailed description of interpreting scientific articles is beyond the scope of this chapter. Interested readers are referred to the Further Reading section. Research quality can be viewed as a hierarchy, ranging from personal opinion and case reports to systematic reviews and meta-analysis (Figure 1.3). Based on this, some of the more popular means for veterinarians to gain new information, such as through conference (congress) presentations, should be assessed based on the credentials (qualifications and relevant experience) of the speaker and quality of evidence (including a description of strengths/weaknesses) presented.
Figure 1.3 Hierarchy of evidence, ranging from low quality (bottom layer of pyramid) to high quality (top layer of pyramid). Note: Quality varies within individual layers, such as may occur with strengths/weaknesses in the design and reporting of clinical trials. Source: Figure adapted from Greenhalgh (2019).
In general, much of the reporting of research in veterinary medicine falls below well-established guidelines. This reflects a risk of bias and weak study design in published articles, highlighting that publication is not a guarantee of the quality of work. For example, in a study to compare treatment A versus treatment B, if the treatment an animal receives is not randomly assigned it is possible that some other factors biased the allocation of treatments. Similarly, if the outcome of treatment depends on a researcher evaluation (e.g., pain assessment), researcher awareness of the treatment given to an animal could affect subsequent evaluation. A particularly common limitation in veterinary clinical research is insufficient sample size, i.e., too few animals were studied to identify an important difference between treatments on an outcome of interest (e.g., pain relief). Therefore, when assessing the results and conclusions from an article it is helpful to confirm if comparable articles reported similar findings, whether research findings have been successfully applied, and the interpretation of research results by independent experts.
Further Reading
Cockcroft, P. and Holmes, M. (2003).
Handbook of Evidence-based Veterinary Medicine
, 1e. Wiley-Blackwell. ISBN: 1405108908.
Greenhalgh, T. (2019).
How to Read a Paper: The Basics of Evidence-based Medicine
, 6e.Wiley-Blackwell. ISBN-10: 1119484745.
Hofmeister, E.H., Watson, V., Snyder, L.B.C., and Love, E.J. (2008). Validity and client use of information from the World Wide Web regarding veterinary anesthesia in dogs.
J Am Vet Med Assoc
233: 1860–1864.
Rufiange, M., Rousseau-Blass, F., and Pang, D.S.J. (2019). Incomplete reporting of experimental studies and items associated with risk of bias in veterinary research.
Vet Rec Open
6: e000322.
https://doi.org/10.1136/vetreco-2018-000322
.
2 Patient Assessment, Planning, and Preparation
Tim Bosmans, Roxanne Buck, and Gareth Zeiler
Sedation Compared to General Anesthesia
Sedation is the depression of awareness, whereby the patient’s response to external stimuli is reduced, but consciousness is maintained. Depending on the patient’s level of alertness before sedation and on the combination and dose of sedatives used, the effect of sedation can be described as mild, moderate, or deep. The aim of mild sedation is to provide anxiolysis with minimal suppression of consciousness. Moderate sedation depresses consciousness, but the patient will still respond to external tactile and auditory stimuli. With deep sedation, the patient will only respond to noxious stimuli. It is a common misconception that sedation is safer than general anesthesia. Although patients usually maintain their physiological reflexes and breathe spontaneously, deep sedation can result in levels of cardiovascular, respiratory, and thermoregulatory depression, and it should not be assumed that reflexes are always maintained. These effects might even be exacerbated when different classes of drugs are used in combination. For example, the combination of alpha-2 adrenergic receptor agonists and opioids results in a synergistic effect and might lead to depression of airway reflexes which can cause upper airway obstruction that leads to asphyxia (e.g., in brachycephalic dogs). Also, sedated patients are generally not monitored as closely as anesthetized patients and, if sedated for procedures like radiographs, their body position is often changed regularly which can increase the risk of regurgitation and aspiration. Thus, monitoring of the sedated animal should always be performed.
General anesthesia, on the other hand, is an induced, reversible, loss of consciousness, whereby the animal is thought to have no recognition of all types of stimuli that occur. Three criteria should ideally be met under general anesthesia and this “triad of anesthesia” includes, unconsciousness, muscle relaxation, and analgesia. Specific drugs that act on one or more components of the triad are used in combination to reduce the side effects of each individual drug. This concept is termed “balanced anesthesia.”
Defining the Purpose of Performing Anesthesia
Before anesthetizing any patient, it is vital that the veterinarian appreciates why this particular patient requires anesthesia. As anesthesia may be required for a variety of procedures, understanding the purpose of anesthesia enables the veterinarian to better plan and prepare for the procedure. For example, a patient having orthopedic surgery will likely require more potent analgesics than one having a small cutaneous mass removed. Likewise, the condition of the patient, the nature, and anticipated duration of the procedure will influence the choice of drugs and method of delivery. Additionally, by understanding why the patient is being anesthetized, the veterinarian can make informed choices about fluid management, the extent of monitoring required, and better appreciate any potential risks to the patient.
Safe and efficient anesthesia requires an optimized patient because inadequate pre-operative preparation is generally accepted as a major contributory factor to pre-anesthetic mortality. A thorough pre-anesthetic assessment allows the veterinarian to develop a pre-anesthetic plan with the goal of reducing patient morbidity and mortality and improving patient and owner experience. The pre-anesthetic plan encompasses the following processes:
Documentation of the condition(s) for which the anesthesia is required.
Assessment of the patient’s overall health status and identification of any hidden conditions that could cause problems during the procedure.
Peri-anesthetic risk determination.
Education of the owner about the procedure and post-procedure care to reduce anxiety and facilitate recovery.
Optimization of the patient’s medical condition before anesthesia.
Development of an appropriate peri-anesthetic care plan.
Patient Assessment
Anesthesia is accompanied by depression of normal physiologic function, most often manifested as hypoventilation, hypotension, and hypothermia due to depression of respiratory, cardiovascular, and neurological functions. Healthy patients are often, though not always, able to compensate enough for these changes to maintain adequate system function. Stressors, such as hypovolemia, hypothermia, pain, or coexisting diseases, can leave animals physiologically compromised, thereby increasing the risk of peri-anesthetic morbidity and mortality.
Before anesthesia, the veterinarian should endeavor to learn as much about the patient as possible to identify individual risk factors that could impact anesthesia. A thorough history and physical examination, in combination with appropriately directed laboratory and other diagnostic procedures, can help identify underlying physiologic and pathologic changes that could impact the anesthetic plan. Thereafter, medical treatment of coexisting diseases and stabilization of the patient before anesthesia play an important role in reducing peri-anesthetic morbidity and mortality.
History Taking
A history should be collected before anesthesia. The history should begin with the signalment of the patient, as species, breed, sex, and age can all alter the patient’s response to anesthesia. Thereafter, the history should focus on the main reason for presentation and the details of current illness (as applicable). History of previous illnesses and medical care, including any previous reactions to anesthetic or other drugs (such as antibiotics), should also be discussed. The history should include a complete review of systems to identify undiagnosed disease or inadequately controlled chronic diseases, with particular focus on the cardiopulmonary and nervous systems (for example exercise intolerance or a history of seizures), which are the most relevant systems in respect of fitness for anesthesia. Confirmation of any current medication, in particular any behavior modifying drugs, cardiac drugs, chronically administered analgesics (e.g., nonsteroidal anti-inflammatory drugs), herbal medicines, and their dosing schedules, is also essential. During this time, it is also important that the veterinarian verifies the client’s contact details, outlines potential risks of the anesthetic and procedure, and obtains consent before proceeding with drafting an anesthetic plan.
There can be some important breed-specific considerations in anesthesia though these are less common than often perceived. For example, greyhounds can have prolonged recovery after receiving some drugs (barbiturates), and other breeds affected by the multiple drug resistance mutation 1 (MDR1; now known as “ABCB1”) gene should initially receive reduced dosages of some drugs (e.g., opioids) and should be reassessed. Some breed-associated conditions can also influence anesthesia. Brachycephalic dogs, for example, are predisposed to upper airway obstruction, miniature schnauzers may have sick sinus syndrome, and Cavalier King Charles Spaniels are predisposed to mitral valve disease. These are examples of common breed-specific considerations and other examples are described in species-specific chapters.
Patient age is also an important consideration. Pediatric and geriatric patients may require dose adjustments. Older patients tend to have more comorbidities than younger patients and more pre-operative diagnostic tests may be warranted (Chapter 15).
Patient sex should also be considered. Pregnancy alters physiology and can affect drug pharmacokinetics. In some species, such as horses, intact males can be more difficult to handle because of their temperament, and they often have higher drug requirements.
Physical Clinical Examination
A physical examination should be completed to build on the information gathered during the history. Documenting physical examination findings forms an important part of the clinical record, and it has been shown that failure to record a physical exam increases the odds for anesthetic-related death in dogs.
For elective cases, it is recommended to perform a clinical examination within 12–24 h before anesthesia. At a minimum, the focused pre-anesthesia examination should encompass assessment of the airway, lungs and heart, with documentation of vital signs. Any abnormal findings on the physical examination should be investigated before proceeding.
Assessment of the cardiovascular system should focus on hydration status and determining the adequacy of tissue perfusion. Heart rate and rhythm, as well as pulse quality and regularity, should be assessed (Table 2.1). Additionally, capillary refill time and mucous membrane color should be noted. Thoracic auscultation should be performed to detect any cardiac murmurs.
Table 2.1 Normal reference intervals of heart rate and mean arterial pressure ranges for common veterinary species during general anesthesia.
Animal
Heart rate
(beats/min)
Mean arterial blood pressure
(mmHg)
Dog
70–100
70–100
Cat
100–200
80–120
Horse (adult)
35–45
70–90
Horse (foal)
50–80
60–80
Cow
60–80
90–140
Sheep and goat
60–90
80–110
Pig
60–90
80–110
The pulmonary system is assessed through respiratory rate, volume, and effort in combination with auscultation of the lungs. Respiratory rates are usually between 12 and 25 breaths/min for small animals and 8 and 20 breaths/ min for large animals. Tidal volumes are usually 8–14 mL/kg at rest. Additionally, the veterinarian should assess for potential upper airway obstruction or difficult intubation.
Evaluation of the nervous system should focus particularly on demeanor, mentation, level of pain, and the presence of any paralysis or weakness. Temperament can impact the ability to perform a physical examination and also affect the response of the patient to drugs. Anxious and highly stressed patients may require higher doses of sedatives, or more potent sedatives, which can predispose to respiratory or cardiovascular depression.
The renal and hepatic systems are also of importance given their role in drug metabolism and excretion. Therefore, if signs of renal (e.g., polyuria/polydipsia) or hepatic disease (e.g., icterus) are identified during the physical examination then they should be investigated further.
Hematology and Biochemical Investigation
Generally, a good clinical history combined with physical examination represents the best method of screening for the presence of disease. Hematologic and biochemical investigation should be performed if a disease is detected or suspected based on clinical examination.
Pre-anesthetic laboratory screening generally includes complete blood cell (CBC) count, serum biochemistry, and urinalysis. Hypoproteinemia and anemia are two of the more common abnormalities that may affect how the patient responds to anesthesia, and urinalysis can be useful in early detection of renal disease (Table 2.2).
Table 2.2 Normal reference intervals for total plasma protein and packed cell volume (PCV) in veterinary species that are commonly anesthetized.
Parameter
Dog
Cat
Horse
Cow
Sheep
Pig
Total plasma protein (g/dL)
5.7–7.2
5.6–7.4
6.5–7.8
7.0–9.0
6.3–7.1
6.0–7.5
PCV (%)
36–54
25–46
27–44
23–35
30–50
30–48
However, the costs of tests, patient stress associated with blood sampling, and questionable significance of abnormal values in changing the anesthetic drug protocol have called into question whether pre-anesthetic screening is necessary in healthy veterinary patients. In human anesthesia, pre-anesthetic screening in healthy patients is not recommended and does not change patient management, predict peri-operative complications, or affect outcomes. In veterinary anesthesia, there is no consensus on the usefulness or necessity of blood tests, and the Association of Veterinary Anesthetists (AVA) voted in 1998 that routine pre-anesthetic screening is unnecessary if the patient is healthy based on physical examination and history, and the clinical use of pre-anesthetic blood tests remains at the discretion of the veterinarian. However, in geriatric animals, evidence suggests that there is value in documenting pre-anesthetic blood tests to appreciate possible progression of undiagnosed or chronic diseases after an anesthetic.
The timing of performing pre-anesthetic blood work is also controversial. It has been suggested that blood tests obtained within 3–6 months before an anesthetic that were within normal reference intervals for the patient are reasonable in clinically healthy animals with no change in history. However, pre-anesthetic laboratory screening has been recommended within two weeks of anesthesia in all otherwise healthy geriatric dogs and cats. Where laboratory values or the patient’s health are abnormal, blood work should be repeated immediately before anesthesia.
Additional biochemical testing in individual patients should be considered when indicated by abnormalities found during the physical examination or in the history. Serum biochemical profiles should be tailored according to the patient, for example, serum glucose and liver function should be investigated in diabetic patients and clotting function tests should be performed where prolonged hemostasis is suspected. The clinician should consider the risk–benefit ratio of any ordered laboratory test, as guided by the age of the patient, complexity of the surgical procedure, and completeness of the history and physical examination.
Other Pre-anesthetic Assessments
The need for any additional pre-anesthetic assessments is usually dictated by historical and clinical findings. For example, blood pressure should be measured in patients with known renal, cardiovascular, or endocrine disease. An electrocardiogram should be performed where arrhythmias are detected on auscultation. Additionally, an echocardiogram may provide detailed information on the structure and function of the heart. Thoracic radiographs should be performed where lower airway disease or cardiac disease is suspected.
The veterinarian should practice good judgment when ordering pre-anesthetic tests, balancing the need for information with test cost and the likelihood of useful information being received.
Risk Assessment and Patient Stratification
Anesthesia is not without risk of morbidity and mortality. Numerous studies have attempted to estimate mortality ranging in commonly anesthetized species, with reported mortality figures across all cases of 0.17–1.5% in dogs, 0.24–2.2% in cats, and 0.9–1.9% in horses, based on large-scale multicenter studies (see Further Reading).
Although anesthetic mortality risk cannot be simply predicted before anesthesia, the American Society of Anesthetists (ASA) formalized a classification system that summarizes patient assessment to a numerical value, thereby helping to identify those patients who warrant special attention. The five category ASA physical status classification system has been used in human anesthesia since 1963, and in veterinary anesthesia, as in humans, mortality is associated with increased ASA class. Each risk category has been defined to provide guidelines to the clinician, and approved examples have been established for human anesthesia. The definitions commonly used in veterinary patients are derived from these examples although the veterinarian should remember that the ASA status classification is a clinical judgment based on multiple factors, with inherent subjectivity (Table 2.3). To improve communication and assessments at a specific institution, institutional-specific examples can be developed.
Table 2.3 American Society of Anesthesiologists (ASA) physical status classification system.
ASA classification
Definition
Patient examples
ASA I
A normal healthy patient
Healthy patient with a normal body condition score
ASA II
A patient with mild systemic disease
Mild diseases without any substantiative functional limitations, e.g., well-controlled epilepsy, pregnancy, obesity, and fractures without shock
ASA III
A patient with severe systemic disease
Substantive functional limitations with one or more moderate-to-severe diseases, e.g., poorly controlled diabetes mellitus and mitral valve disease with moderate reduction of ejection fraction
ASA IV
A patient with severe systemic disease that is a constant threat to life
Cardiac valve dysfunction with severe reduction of ejection fraction or congestive heart failure, shock, sepsis, disseminated intravascular coagulation, and severe trauma
ASA V
A moribund patient that is not expected to survive without the procedure
Severe hemorrhage, multiple organ dysfunction syndrome, and decompensated congestive heart failure
The addition of “E” denotes an emergency procedure. With
emergency
defined as existing when delay in treatment of the patient would lead to a significant increase in the threat to life or body part.
It is important to understand the purpose of the system is to assess and communicate pre-anesthetic comorbidities. While the system alone does not predict peri-operative risks, when used alongside other factors, it can be useful in predicting peri-operative risks. Dogs and cats with ASA status ≥ III have an increased risk of anesthesia-related death and severe complications (hypotension and hypothermia) compared to those with ASA status < III (see Further Reading).
