PWS Appendix 6.pdf

Appendix 6: AVMA Guidelines for the Euthanasia of Animals: 2020 Edition

Guideline document (121 pages)

AVMA GUIDELINES FOR THE EUTHANASIA OF ANIMALS: 2020 EDITION 1

AVMA Guidelines for the Euthanasia of Animals:

2020 Edition* Members of the Panel on Euthanasia Steven Leary, DVM, DACLAM (Chair); Fidelis Pharmaceuticals, High Ridge, Missouri Wendy Underwood, DVM (Vice Chair); Indianapolis, Indiana Raymond Anthony, PhD (Ethicist); University of Alaska Anchorage, Anchorage, Alaska Samuel Cartner, DVM, MPH, PhD, DACLAM (Lead, Laboratory Animals Working Group);

University of Alabama at Birmingham, Birmingham, Alabama Temple Grandin, PhD (Lead, Physical Methods Working Group); Colorado State University, Fort Collins, Colorado Cheryl Greenacre, DVM, DABVP (Lead, Avian Working Group); University of Tennessee, Knoxville, Tennessee Sharon Gwaltney-Brant, DVM, PhD, DABVT, DABT (Lead, Noninhaled Agents Working Group); Veterinary

Information Network, Mahomet, Illinois Mary Ann McCrackin, DVM, PhD, DACVS, DACLAM (Lead, Companion Animals Working Group);

University of Georgia, Athens, Georgia Robert Meyer, DVM, DACVAA (Lead, Inhaled Agents Working Group); Mississippi State University, Mississippi

State, Mississippi David Miller, DVM, PhD, DACZM, DACAW (Lead, Reptiles, Zoo and Wildlife Working Group); Loveland, Colorado Jan Shearer, DVM, MS, DACAW (Lead, Animals Farmed for Food and Fiber Working Group); Iowa State

University, Ames, Iowa Tracy Turner, DVM, MS, DACVS, DACVSMR (Lead, Equine Working Group); Turner Equine Sports Medicine and

Surgery, Stillwater, Minnesota Roy Yanong, VMD (Lead, Aquatics Working Group); University of Florida, Ruskin, Florida

AVMA Staff Consultants Cia L. Johnson, DVM, MS, MSc; Director, Animal Welfare Division Emily Patterson-Kane, PhD; Animal Welfare Scientist, Animal Welfare Division

The following individuals contributed substantively through their participation in the Panel’s Working Groups, and their assistance is sincerely appreciated.

Inhaled Agents—Scott Helms, DVM, DABVP; Lee Niel, PhD; Daniel Weary, PhD Noninhaled Agents—Virginia Fajt, DVM, PhD, DACVCP Physical Methods—Rose Gillesby, DVM; Jeff Hill, PhD; Jennifer Woods, BSc Aquatics—Craig Harms, DVM, PhD, DACZM; Nick Saint-Erne, DVM; Michael Stoskopf, DVM, PhD, DACZM Avian—Laurel Degernes, DVM, MPH, DABVP; Laurie Hess, DVM, DABVP; Kemba Marshall, DVM, DABVP; James

Morrisey, DVM, DABVP; Joanne Paul-Murphy, DVM, DACZM, DACAW Companion Animals—Kathleen Cooney, MS, DVM; Stacey Frick, DVM; John Mays; Rebecca Rhoades, DVM Equids—Fairfield Bain, DVM, MBA, DACVIM, DACVP, DACVECC; Thomas R. Lenz, DVM, MS, DACT; Nathaniel

Messer IV, DVM, DABVP; Stuart Shoemaker, DVM, DACVS Food and Fiber Animals—Eric Benson, PhD; C. Scanlon Daniels, DVM, MBA; John Deen, DVM, PhD, DABVP, DACAW; John Gilliam, DVM, MS, DACVIM, DABVP; Dee Griffin, DVM, MS; Glen Johnson, DVM; James Kober, DVM; Meghann Pierdon, VMD, DACAW; Paul Plummer, DVM, DACVIM-LA; Richard Reynnells, PhD; James Reynolds, DVM, MPVM, DACAW; Bruce Webster, PhD

Laboratory Animals—James Artwhol, MS, DVM, DACLAM; Larry Carbone, DVM, PhD, DACLAM; Paul Flecknell, VetMB, MRCVS, PhD, DECVA, DECLAM, DACLAM, FRCVS; David P. Friedman, PhD; Debra Hickman, DVM, DACLAM, DACAW; Kathleen Pritchett-Corning, DVM, DACLAM, MRCVS

Reptiles, Zoo and Wild Animals—Scott Citino, DVM, DACZM; Mark Drew, DVM, MS, DACZM; Julie Goldstein, DVM; Barry Hartup, DVM, PhD; Gregory Lewbart, MS, VMD, DACZM; Douglas Mader, MS, DVM, DABVP, FRSM; Patrick Morris, DVM, DACZM

*The AVMA Panel on Euthanasia develops the content of the guidelines, with support from its working groups. The panel is required to do a comprehensive review and update of the report at least every 10 years, although more frequent major revisions are possible based on substantive information gleaned from new research and experience with practical implementation. To ensure the guidelines remain as up-to-date as possible, interim revisions (reflecting substantive updates, but of a less extensive nature than a major revision) are also accommodated.

2 AVMA GUIDELINES FOR THE EUTHANASIA OF ANIMALS: 2020 EDITION

Copyright © 2020 by the American Veterinary Medical Association

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ISBN 978-1-882691-09-8

Version 2020.0.1

AVMA GUIDELINES FOR THE EUTHANASIA OF ANIMALS: 2020 EDITION 3

CONTENTS

Part I—Introduction and General Comments I1 Preface I2 Historical Context and Current Edition I2.1 History of the Panel on Euthanasia I2.2 Substantive Changes Since the Last Edition I2.3 Statement of Use I3 What Is Euthanasia?

I3.1 A Good Death as a Matter of Humane Disposition I3.2 A Good Death as a Matter of Humane Technique I4 Euthanasia and Veterinary Medical Ethics I5 Evaluating Euthanasia Methods I5.1 Consciousness and Unconsciousness I5.2 Pain and Its Perception I5.3 Stress and Distress I5.4 Animal Behavior I5.5 Human Behavior I5.6 Sedation Versus Anesthesia I6 Mechanisms of Euthanasia I7 Confirmation of Death I8 Disposal of Animal Remains I9 Footnotes I10 References

Part II—Methods of Euthanasia M1 Inhaled Agents M1.1 Common Considerations M1.2 Principles Governing Administration M1.3 Inhaled Anesthetics M1.4 Carbon Monoxide M1.5 Nitrogen, Argon M1.6 Carbon Dioxide M2 Noninhaled Agents M2.1 Common Considerations M2.2 Routes of Administration M2.3 Barbituric Acid Derivatives M2.4 Pentobarbital Combinations M2.5 Tributame M2.6 T-61 M2.7 Ultrapotent Opioids M2.8 Dissociative Agents and α2-Adrenergic Receptor Agonists M2.9 Potassium Chloride and Magnesium Salts M2.10 Chloral Hydrate and α-Chloralose M2.11 Alcohols

M2.12 MS 222 (TMS)

M2.13 Benzocaine Hydrochloride M2.14 Eugenol M2.15 2-Phenoxyethanol M2.16 Quinaldine (2-Methylquinoline, Quinalidine Sulfate) M2.17 Metomidate M2.18 Sodium Hypochlorite M2.19 Formaldehyde M2.20 Lidocaine Hydrochloride M2.21 Unacceptable Agents M3 Physical Methods M3.1 Common Considerations

M3.2 PCB

M3.3 NPCB

M3.4 Manually Applied Blunt Force Trauma to the Head

M3.5 Gunshot M3.6 Cervical Dislocation M3.7 Decapitation M3.8 Electrocution M3.9 Kill Traps M3.10 Maceration M3.11 Focused Beam Microwave Irradiation M3.12 Thoracic (Cardiopulmonary, Cardiac) Compression M3.13 Adjunctive Methods M4 Footnotes M5 References

Part III—Methods of Euthanasia by Species and Environment S1 Companion Animals S1.1 General Considerations S1.2 Acceptable Methods S1.3 Acceptable With Conditions Methods S1.4 Adjunctive Methods S1.5 Unacceptable Methods S1.6 Special Considerations S1.7 Fetuses and Neonates S1.8 Euthanasia in Specific Environments S2 Laboratory Animals S2.1 General Considerations S2.2 Small Laboratory and Wild-Caught Rodents (Mice, Rats, Hamsters, Guinea Pigs, Gerbils, Degus, Cotton Rats, etc) S2.3 Laboratory Farm Animals, Dogs, Cats, Ferrets, and Nonhuman Primates S2.4 Laboratory Rabbits S2.5 Laboratory Fish, Amphibians, and Reptiles S3 Animals Farmed for Food and Fiber S3.1 General Considerations S3.2 Bovids and Small Ruminants S3.3 Swine S3.4 Poultry S4 Equids S4.1 General Considerations S4.2 Methods S4.3 Special Cases and Exceptions S5 Avians S5.1 General Considerations S5.2 Methods S5.3 Eggs, Embryos, and Neonates S6 Fish and Aquatic Invertebrates S6.1 General Considerations S6.2 Finfish S6.3 Aquatic Invertebrates S7 Zoologic and Free-Ranging Nondomestic Animals S7.1 General Considerations S7.2 Captive Invertebrates S7.3 Captive Amphibians and Reptiles S7.4 Captive Nonmarine Mammals S7.5 Captive Marine Mammals S7.6 Free-Ranging Wildlife S7.7 Free-Ranging Marine Mammals S8 Footnotes S9 References Glossary Appendices

4 AVMA GUIDELINES FOR THE EUTHANASIA OF ANIMALS: 2020 EDITION

Part I—Introduction and General Comments I1 Preface

Animal issues are no longer socially invisible, and increasingly, greater attention is being devoted to understanding the moral significance of experi-ences of animals and to taking into consideration the welfare of animals. During the past half-century, ef-forts to ensure the respectful and humane treatment of animals have garnered global attention.1,2 Concern for the welfare of animals is reflected in the growth of animal welfare science and ethics. The former is evident in the emergence of academic programs, es-tablishment of specialty colleges, implementation of curricular changes in veterinary colleges, prolifera-tion of scientific journal articles, and development of funding streams committed either partially or exclu-sively to the study of how animals are impacted by various environments and human interventions. The latter has seen the application of numerous ethical approaches (eg, rights-based theories, utilitarianism, virtue ethics, contractarianism, pragmatic ethics) to assessing the moral value of animals and the nature of the human-animal relationship.1,3–9 The proliferation of interest in animal use and care, at the national and international levels, is also apparent in recent protec-tions accorded to animals in new and amended laws and regulations, institutional and corporate policies, and purchasing and trade agreements. Changing so-cietal attitudes toward animal care and use have in-spired scrutiny of some traditional and contemporary practices applied in the management of animals used for agriculture, research and teaching, companion-ship, and recreation or entertainment and of animals encountered in the wild. Attention has also been fo-cused on conservation and the impact of human in-terventions on terrestrial and aquatic wildlife and the environment. Within these contexts, veterinarians provide leadership on how to care well for animals, including how to relieve unnecessary pain and suf-fering.

In creating the 2020 and 2013 edition of the AVMA Guidelines for the Euthanasia of Animals (Guide-lines), the POE made every effort to identify and ap-ply the best research and empirical information avail-able. As new research is conducted and more practi-cal experience gained, recommended methods of eu-thanasia may change. As such, the AVMA and its POE have made a commitment to ensure the Guidelines reflect an expectation and paradigm of continuous improvement that is consistent with the obligations of the Veterinarian’s Oath.10 As for other editions of the document, modifications of previous recommen-dations are also informed by continued professional and public sensitivity to the ethical care of animals.

While some euthanasia methods may be utilized in slaughter (which refers to humane killing of ani-mals destined for human consumption) or harvest and depopulation, recommendations related to hu-mane slaughter and depopulation fall outside the pur-view of the Guidelines and are addressed by separate documents.

The Guidelines set criteria for euthanasia, spec-ify appropriate euthanasia methods and agents, and are intended to assist veterinarians in their exercise of professional judgment. The Guidelines acknowl-edge that euthanasia is a process involving more than just what happens to an animal at the time of its death. Apart from delineating appropriate meth-ods and agents, these Guidelines also recognize the importance of considering and applying appropriate pre-euthanasia (eg, sedation) and animal handling practices, as well as attention to disposal of animals’ remains.

I2 Historical Context and Current Edition

I2.1 HISTORY OF THE

PANEL ON EUTHANASIA

Since 1963 the AVMA has convened a POE to eval-uate methods and potential methods of euthanasia for the purpose of creating guidelines for veterinarians who carry out or oversee the euthanasia of animals.

The scope of the 1963 edition was limited to meth-ods and recommendations applicable to dogs, cats, and other small mammals. Subsequent editions pub-lished in 1972 and 1978 encompassed more methods and species (laboratory animals and food animals, respectively), and included additional information about animals’ physiologic and behavioral responses to euthanasia (specifically, pain, stress, and distress), euthanasia’s effects on observers, and the economic feasibility and environmental impacts of various ap-proaches. In 1986 information on poikilothermic, aquatic, and fur-bearing wildlife was introduced; in 1993 recommendations for horses and wildlife were

ABBREVIATIONS

ASIC Acid-sensing ion channel CAS Controlled atmospheric stunning DEA Drug Enforcement Agency EEG Electroencephalogram or electroencephalographic EPA Environmental Protection Agency HPA Hypothalamic-pituitary axis

IACUC Institutional animal care and use committee MS 222 Tricaine methanesulfonate NPCB Nonpenetrating captive bolt PCB Penetrating captive bolt POE Panel on Euthanasia SNS Sympathetic nervous system

AVMA GUIDELINES FOR THE EUTHANASIA OF ANIMALS: 2020 EDITION 5

added; and in 2000 an update acknowledged a need for more research on approaches suitable for depopu-lation. An interim revision by the AVMA Animal Wel-fare Committee in 2007 incorporated information derived from an existing, but separate, AVMA policy on the use of maceration to euthanize day-old chicks, poults, and pipped eggs, and the name of the report was changed to the AVMA Guidelines on Euthanasia.

In 2013 the process for compiling the POE’s report was substantially changed to include more breadth and depth of expertise in the affected spe-cies and environments in which euthana sia is per-formed. More than 3 years of deliberation by more than 60 individuals, including veterinarians, an imal scientists, behaviorists, psychologists, and an an imal ethicist, resulted in robust commentary and recom-mendations. A comment period allowed AVMA mem-bers an opportunity to provide input and share their experiences directly with POE members.

The 2020 iteration of the Guidelines constitutes the ninth edition of the POE’s report. The process for compiling this edition was similar to that of the 2013 edition. Two years of review, discussion, and revision by the POE culminated in this edition. A comment period was held and the input from AVMA members helps ensure the resulting document is not only sci-entifically robust, but practically sound.

I2.2 SUBSTANTIVE CHANGES

SINCE THE LAST EDITION

In this interim update of the Guidelines, meth-ods, techniques, and agents of euthanasia have been updated and de tailed descriptions have been includ-ed to assist veter inarians in applying their profession-al judgment. Spe cies-specific sections have been ex-panded or added to include more guidance for terres-trial and aquatic species kept for a variety of purposes and under dif ferent conditions. Where possible, ap-propriate flowcharts, illustrations, tables, and appen-dices have been used to clarify rec ommendations.

Appendices 1 and 2 may be useful as a quick refer-ence guide, but should never be used in lieu of the full text of the document by those perform ing eutha-nasia. All illustrations and figures have been moved to Appendix 3 of the document.

Some of the more significant changes are as fol-lows:

• Language was added to clarify the distinction be-tween sedation and anesthesia. Specifically, ani-mals under sedation may be aroused to a conscious state with sufficient stimulation. Recognizing this is critical when categorizing the effects of agents and distinguishing even deep states of sedation from unconsciousness.

• The conditions for the use of CO2 with rodents in the laboratory have changed from a recommended 10% to 30% of the chamber or cage volume/min to a recommended 30% to 70% of the chamber or cage volume/min. The extensive literature used to make this recommendation is cited and the AVMA appreciates the proactive efforts made by the in-ternational research community to provide the evidence needed to make this determination.

• Euthanasia techniques appropriate for use with rabbits raised for meat are categorized and de-scribed. This material is located in the Laboratory Animals section to place them with other tech-niques used with these species.

• The Animals Farmed for Food and Fiber section has been expanded to include American bison, wa-ter buffalo, camelids, and cervids. Updates to the application of captive bolt in several species have been made and new illustrations are available to assist veterinarians in proper usage.

• In the Avians section the recommendation for when avian embryos achieve the potential for per-ception has been amended from 50% to 80% of in-cubation for all avian eggs. This recommendation should be applied across avians with consideration for species-specific differences in development and using the best available data.

I2.3 STATEMENT OF USE

The Guidelines are designed for use by members of the veterinary profession who carry out or oversee the euthanasia of animals. As such, they are intended to apply only to nonhuman species.

The species addressed by the practice of vet-erinary medicine are diverse. A veterinarian experi-enced with the species of interest should be consult-ed when choosing a method of euthanasia, particular-ly when little species-specific research on euthanasia has been conducted. Methods and agents selected will often be situation specific, as a means of mini-mizing potential risks to the animal’s welfare and personnel safety. Given the complexity of issues that euthanasia presents, references on anatomy, physiol-ogy, natural history, husbandry, and other disciplines may assist in understanding how various methods may impact an animal during the euthanasia process.

Veterinarians performing or overseeing eutha-nasia must assess the potential for animal distress due to physical discomfort, abnormal social settings, novel physical surroundings, pheromones or odors from nearby or previously euthanized animals, the presence of humans, or other factors (including im-pact on the environment and other animals). In ad-dition, human safety and perceptions, availability of trained personnel, potential infectious disease concerns, conservation or other animal population objectives, regulatory oversight that may be species specific, available equipment and facilities, options for disposal, potential secondary toxicity, and other factors must be considered. Human safety is of ut-most importance, and appropriate safety equipment, protocols, and knowledge must be available before animals are handled. Advance preparation includes protocols and supplies for addressing personnel in-jury due to animal handling or exposure to drugs and equipment used during the process. Once eutha-

6 AVMA GUIDELINES FOR THE EUTHANASIA OF ANIMALS: 2020 EDITION

nasia has been carried out, death must be carefully verified. All laws and regulations pertaining to the species being euthanized, the methods employed, and the disposal of the animal’s remains and/or any water containing pharmaceuticals used for euthana-sia must be followed.

The POE’s objective in creating the Guidelines is to provide guidance for veterinarians about how to prevent and/or relieve the pain and suffering of ani-mals that are to be euthanized. While every effort has been made to identify and recommend appropriate approaches for common species encountered under common conditions, the POE recognized there will be less than perfect situations in which a recommend-ed method of euthanasia may not be possible and a method or agent that is best under the circumstances will need to be applied. For this reason, although the Guidelines may be interpreted and understood by a broad segment of the general population, a veterinar-ian should be consulted in their application.

I3 What Is Euthanasia?

Euthanasia is derived from the Greek terms eu meaning good and thanatos meaning death. The term is usually used to describe ending the life of an individual animal in a way that minimizes or elimi-nates pain and distress. A good death is tantamount to the humane termination of an animal’s life.

In the context of these Guidelines, the veteri-narian’s prima facie duty in carrying out euthanasia includes, but is not limited to, (1) their humane dis-position to induce death in a manner that is in accord with an animal’s interest and/or because it is a matter of welfare, and (2) the use of humane techniques to induce the most rapid and painless and distress-free death possible. These conditions, while separate, are not mutually exclusive and are codependent.

Debate exists about whether euthanasia appro-priately describes the killing of some animals at the end of biological experiments11 and of unwanted shel-ter animals. The Panel believes that evaluating the so-cial acceptability of various uses of animals and/or the rationale for inducing death in these cases is beyond its purview; however, current AVMA policy supports the use of animals for various human purposes,12 and also recognizes the need to euthanize animals that are unwanted or unfit for adoption.13 Whenever ani-mals are used by humans, good animal care practices should be implemented and adherence to those good practices should be enforced. When evaluating our responsibilities toward animals, it is important to be sensitive to the context and the practical realities of the various types of human-animal relationships.

Impacts on animals may not always be the center of the valuation process, and there is disagreement on how to account for conflicting interspecific interests.

The Panel recognizes these are complex issues since how to bring about a “good death” for animals is re-garded as “essentially contested” (morally and con-ceptually),14 raising concerns across a large number of domains, including scientific, ethical, economic, environmental, political, and social.

I3.1 A GOOD DEATH AS A

MATTER OF HUMANE DISPOSITION

Humane disposition reflects the veterinarian’s desire to do what is best for the animal and serves to bring about the best possible outcome for the animal.

Thus, euthanasia as a matter of humane disposition can be either intent or outcome based.

Euthanasia as a matter of humane disposition oc-curs when death is a welcome event and continued existence is not an attractive option for the animal as perceived by the owner and veterinarian. When animals are plagued by disease that produces insur-mountable suffering, it can be argued that continuing to live is worse for the animal than death or that the animal no longer has an interest in living. The hu-mane disposition is to act for the sake of the animal or its interests, because the animal will not be harmed by the loss of life. Instead, there is consensus that the animal will be relieved of an unbearable burden.

As an example, when treating a companion animal that is suffering severely at the end of life due to a debilitating terminal illness, a veterinarian may rec-ommend euthanasia, because the loss of life (and at-tendant natural decline in physical and psychological faculties) to the animal is not relatively worse com-pared with a continued existence that is filled with prolonged illness, suffering, and duress. In this case, euthanasia does not deprive the animal of the oppor-tunity to enjoy more goods of life (ie, to have more satisfactions fulfilled or enjoy more pleasurable expe-riences). And, these opportunities or experiences are much fewer or lesser in intensity than the presence or intensity of negative states or affect. Death, in this case, may be a welcome event and euthanasia helps to bring this about, because the animal’s life is not worth living but, rather, is worth avoiding.

Veterinarians may also be motivated to bring about the best outcome for the animal. Often, veteri-narians face the difficult question of trying to decide (or helping the animal’s owner to decide) when eu-thanasia would be a good outcome. In making this de-cision many veterinarians appeal to indices of welfare or quality of life. Scientists have described welfare as having 3 components: that the animal functions well, feels well, and has the capacity to perform behaviors that are innate or species-specific adaptations15–17 (an alternative view is also available18). An animal has good welfare if, overall, its life has positive value for

it. When an animal no longer continues to enjoy good welfare (when it no longer has a life worth living be-cause, on balance, its life no longer has positive value for it, or will shortly be overcome by negative states), the humane thing to do is to give it a good death. Eu-thanasia relieves the animal’s suffering, which is the desired outcome.

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I3.2 A GOOD DEATH AS A

MATTER OF HUMANE TECHNIQUE

When the decision has been made to euthanize and the goal is to minimize pain, distress, and nega-tive effect to the animal, the humaneness of the tech-nique (ie, how we bring about the death of animals) is also an important ethical issue. As veterinarians and human beings it is our responsibility to ensure that if an animal’s life is to be taken, it is done with the highest degree of respect, and with an emphasis on making the death as painless and distress free as possible. When euthanasia is the preferred option, the technique employed should result in rapid loss of consciousness followed by cardiac or respiratory arrest and, ultimately, a loss of brain function. In ad-dition, animal handling and the euthanasia technique should minimize distress experienced by the animal prior to loss of consciousness. The POE recognized that complete absence of pain and distress cannot al-ways be achieved. The Guidelines attempt to balance the ideal of minimal pain and distress with the real-ity of the many environments in which euthanasia is performed.

While recommendations are made, it is impor-tant for those utilizing these recommendations to un-derstand that, in some instances, agents and methods of euthanasia identified as appropriate for a particular species may not be available or may become less than an ideal choice due to differences in circumstances.

Conversely, when settings are atypical, methods nor-mally not considered appropriate may become the method of choice. Under such conditions, the hu-maneness (or perceived lack thereof) of the method used to bring about the death of an animal may be distinguished from the intent or outcome associated with an act of killing. Following this reasoning, it may still be an act of euthanasia to kill an animal in a man-ner that is not perfectly humane or that would not be considered appropriate in other contexts. For exam-ple, due to lack of control over free-ranging wildlife and the stress associated with close human contact, use of a firearm may be the most appropriate means of euthanasia. Also, shooting a suffering animal that is in extremis, instead of catching and transporting it to a clinic to euthanize it using a method normally considered to be appropriate (eg, barbiturates), is consistent with one interpretation of a good death.

The former method promotes the animal’s overall in-terests by ending its misery quickly, even though the latter technique may be considered to be more ac-ceptable under normal conditions.19 Neither of these examples, however, absolves the individual from their responsibility to ensure that recommended methods and agents of euthanasia are preferentially used.

I4 Euthanasia and Veterinary Medical Ethics

The AVMA has worked to ensure that veterinar-ians remain educated about public discourse around animal ethics and animal welfare issues and that they are able to participate in meaningful ways. While an essential ingredient in public discourses about ani-mals, sound science is by itself inadequate to address questions of ethics and values that surround the ap-propriate treatment of animals, especially as they relate to end-of-life issues. Since the 2013 edition, a number of authors20,21 have probed in greater depth the issue of a good death for animals in both philo-sophical and ethical terms. To this end, and consis-tent with its charge, the POE hopes to provide veteri-narians, those under their supervision, and the public with well-informed and credible arguments on how to approach the ethically important and sometimes complex issue of the death of an animal. In so doing, it hopes to promote greater understanding regarding the contexts or settings involving euthanasia and the complexity of end-of-life issues involving animals.

While not a regulatory body, the AVMA also hopes to offer guidance to those who may apply these Guidelines as part of regulatory structures designed to protect the welfare of animals used for human purposes. By creating and maintaining these Guidelines, the AVMA hopes to ensure that when a veterinarian or other professional intentionally kills an animal under their charge, it is done with respect for the interests of the animal and that the process is as humane as possible (ie, that it minimizes pain and distress to the animal and that death occurs as rapidly as possible).

The AVMA does not take the death of nonhuman animals lightly and attempts to provide guidance for its members on both the morality and practical ne-cessity of the intentional killing of animals. Veteri-narians, in carrying out the tenets of their Oath, may be compelled to bring about the intentional death of animals for a variety of reasons. The finality of death is, in part, what makes it an ethically important issue;

death forever cuts off future positive states, benefits, or opportunities.22 In cases where an animal no longer has a good life, however, its death also extinguishes permanently any and all future harms associated with poor welfare or quality of life.19 What constitutes a good life and what counts as an impoverished life, or one that has limited quality such that the death of the animal is the most humane option, are research areas in need of further study by the veterinary and eth-ics communities.23,24 Animal scientists and veterinar-ians are also investigating the processes by which an animal dies during the antemortem period and eutha-nasia methods and techniques that mitigate harmful effects.25–28 Further research is also needed regarding the different contexts within which euthanasia oc-curs, so that improvements in the performance and outcomes of euthanasia can be made.

The intentional killing of healthy animals, as well as those that are impaired, is a serious concern for the public. When animals must be killed and veterinar-ians are called upon to assist, the AVMA encourages careful consideration of the decision to euthanize

8 AVMA GUIDELINES FOR THE EUTHANASIA OF ANIMALS: 2020 EDITION

and the method(s) used. This is also true for euthana-sia carried out during the course of disease control or protection of public health, as a means of domestic or wild animal population control, in conjunction with animal use in biomedical research, and in the pro-cess of food and fiber production. Killing of healthy animals under such circumstances, while unpleasant and morally challenging, is a practical necessity. The AVMA recognizes such actions as acceptable if those carrying out euthanasia adhere to strict policies, guidelines, and applicable regulations.

In thinking seriously about veterinary medical ethics, veterinarians should familiarize themselves with the plurality of public moral views surround-ing animal issues and also be cognizant of personal views and complicating factors that may impact their own ethical decision-making. While the Veterinari-an’s Oath,10 Principles of Veterinary Medical Ethics of the AVMA,29 state veterinary practice acts, and other guidance emanating from veterinary professional or-ganizations and regulatory bodies provide direction for how veterinarians should interact with clients and their animals, different veterinarians may have differ-ent personal ethical values1,30 and this may impact their recommendations.

In their capacity as animal advocate and client advisor, the precision and credibility of advice provid-ed by veterinarians will help to advance client com-pliance. In many instances when veterinarians are called upon to benefit society through their scientific knowledge, practical experience, and understanding of how animals are benefited and harmed, straightfor-ward answers may not be forthcoming. In such cases, veterinarians and animal welfare scientists may have to facilitate conscientious decision-making by pro-moting ethical dialogue.31–34 As advisor and conduit for information (and while respecting the autonomy of their clients to make decisions on behalf of their animals), veterinarians should advance pertinent scientific knowledge and ethical concerns related to practices and procedures so that their clients and/or society can make informed decisions.1

Veterinarians who are committed to a broad un-derstanding of the “do no harm” principle may have to determine whether an animal’s life is worth liv-ing, especially when there is no consensus on when it is appropriate to let that life go. While welfare or quality of life is typically adopted as part of the as-sessment of an animal’s interests, what is in an ani-mal’s interest need not be singularly identified with its welfare, especially if welfare is defined narrowly and if the animal is harmed more by its continued life than its death. For example, if welfare is defined solely in terms of an animal’s subjective experience, euthanasia may be warranted even if the animal is not showing signs of suffering at the present time and if there is some commitment to avoid harm. Euthanasia may be considered to be the right course to spare the animal from what is to come (in conjunction with a more holistic or objective account of what is in an animal’s interest), if medical intervention would only prolong a terminal condition, or if current health conditions cannot be successfully mitigated. In these instances, intentional killing need not be motivated by narrow welfare-based interests35 but may be con-nected to the overall value of death to the animal.

That some animals are subjects-of-a-life,36–39 and that human caretakers have moral responsibilities to their animals and do not want to see them endure contin-ued harm,40,41 may be factors in deciding whether death is in an animal’s interest. (A subject-of-a-life is a being that is regarded as having inherent value and should not be treated as a mere means to an end. It is a being that possesses an internal existence and has needs, desires, preferences, and a psychosocial iden-tity that extends through time.3,6)

In some cases (eg, animals used for research), in-tentional killing of the animal to minimize harm to it may be trumped by more pressing ends. Here, the decision to kill an animal and how to do so will be complicated by external factors, such as productivity, the greater public and general good, economics, and concern for other animals. In human-animal relation-ships there usually are other mitigating factors that are relevant besides ones pertaining only to animal welfare or the animal’s interest(s). In laboratory situ-ations, for example, where animals are employed as research subjects and death may be a terminal point, animal welfare considerations are balanced against the merits of the experimental design and merits of the research. In such cases, ensuring the respectful and humane treatment of research animals will be largely up to IACUCs. These committees must apply the principles of refinement, replacement, and re-duction, and ensure a respectful death for research animals. The decision to induce death may also in-volve whether replacements can be created for the animals that are killed.42,43 These other factors might justify killing an animal, despite the fact that the ani-mal might otherwise have had a life worth living. For example, killing may be justified for disease control or public health purposes, population control, bio-medical research, or slaughter for food and/or fiber.

In other instances, keeping an animal alive that does not have a life worth living can be justified (eg, re-search circumstances where it would be impractical to kill the animal or when ensuring its survival would promote a greater good19).

There may be instances in which the decision to kill an animal is questionable, especially if the ani-mal is predicted to have a life worth living if it is not killed. One example is the healthy companion animal whose owner wants to euthanize it because keeping it in the home is no longer possible or convenient.

In this case, the veterinarian, as advisor and animal advocate, should be able to speak frankly about the animal’s condition and suggest alternatives to eutha-nasia.

Prima facie, it is the ethical responsibility of vet-erinarians to direct animal owners toward euthanasia

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as a compassionate treatment option when the alter-native is prolonged and unrelenting suffering.44 How-ever, accommodating a pluralism of values, interests, and duties in animal ethics is challenging. This un-derscores the need for veterinarians to consider the broader context in thinking about what animal care she or he will prescribe. There are no easy reduction-ist formulas to which to appeal. In many cases, advice will need to be responsive to the needs at hand. At-tention must be given to how the welfare and suffer-ing of the animal are understood within the context of its whole life and in light of socially acceptable ways in which humans and animals interact in differ-ent environments.

Because veterinarians are committed to improv-ing animal and human health and welfare, and be-cause they work tirelessly to discover causes and cures for animal diseases and promote good animal management, some may feel a sense of disquiet or de-feat when euthanasia becomes the better course of action. The POE hopes that these Guidelines and oth-er AVMA policies will assist veterinarians who may be struggling with what may seem to be gratuitous euthanasia, the acceptability of certain procedures, and the sometimes routine nature of performing eu-thanasia. Toward that end, the decision aids in Fig-ures 1 and 2a are offered as a resource.

I5 Evaluating Euthanasia Methods In evaluating methods of euthanasia, the POE considered the following criteria: (1) ability to induce loss of consciousness and death with a minimum of pain and distress; (2) time required to induce loss of consciousness; (3) reliability; (4) safety of personnel;

(5) irreversibility; (6) compatibility with intended animal use and purpose; (7) documented emotional effect on observers or operators; (8) compatibility with subsequent evaluation, examination, or use of tissue; (9) drug availability and human abuse poten-tial; (10) compatibility with species, age, and health status; (11) ability to maintain equipment in proper working order; (12) safety for predators or scavengers should the animal’s remains be consumed; (13) legal requirements; and (14) environmental impacts of the method or disposition of the animal’s remains.

Euthanasia methods are classified in the Guide-lines as acceptable, acceptable with conditions, and unacceptable. Acceptable methods are those that consistently produce a humane death when used as the sole means of euthanasia. Methods accept-able with conditions are those techniques that may require certain conditions to be met to consistently produce humane death, may have greater potential for operator error or safety hazard, are not well docu-mented in the scientific literature, or may require a secondary method to ensure death. Methods accept-able with conditions are equivalent to acceptable methods when all criteria for application of a method can be met. Unacceptable techniques are those meth-ods deemed inhumane under any conditions or that the POE found posed a substantial risk to the human applying the technique. The Guidelines also include information about adjunctive methods, which are those that should not be used as a sole method of eu-thanasia, but that can be used in conjunction with other methods to bring about euthanasia.

The POE recognized there will be less-than-per-fect situations in which a method of euthanasia that is listed as acceptable or acceptable with conditions may not be possible, and a method or agent that is the best under the circumstances will need to be applied.

As with many other procedures involving ani-mals, some methods of euthanasia require physical handling of the animal. The amount of control and kind of restraint required will be determined by the species, breed, and size of animal involved; the de-gree of domestication, tolerance to humans, level of excitement, and prior handling experience of the ani-mal; the presence of painful injury or disease; the an-imal’s social environment; and the method of eutha-nasia and competence of the person(s) performing the euthanasia. Proper handling is vital to minimize pain and distress in animals, to ensure the safety of the person performing euthanasia, and, often, to pro-tect other people and animals. Handling animals that are not accustomed to humans or that are severely injured or otherwise compromised may not be pos-sible without inducing stress, so some latitude in the means of euthanasia is needed in some situations.

The POE discussed the criteria for euthanasia used in the Guidelines as they apply to circumstances when the degree of control over the animal makes it dif-ficult to ensure death without pain and distress. Pre-medication with the intent of providing anxiolysis, analgesia, somnolence for easier and safer IV access, and reduction of stage II or postmortem activity that could be distressing to personnel is strongly encour-aged to reduce animal distress and improve person-nel safety. This is particularly important for prey spe-cies, nondomesticated species, and animals enduring painful conditions.

Personnel who perform euthanasia must dem-onstrate proficiency in the use of the technique in a closely supervised environment. Each facility or in-stitution where euthanasia is performed (whether a clinic, laboratory, or other setting) is responsible for training its personnel adequately to ensure the facil-ity or institution operates in compliance with federal, state, and local laws. Furthermore, experience in the humane restraint of the species of animal to be eutha-nized is important and should be expected, to ensure that animal pain and distress are minimized. Train-ing and experience should include familiarity with the normal behavior of the species being euthanized, an appreciation of how handling and restraint affect that behavior, and an understanding of the mecha-nism by which the selected technique induces loss of consciousness and death. Euthanasia should only be attempted when the necessary drugs and supplies are available to ensure a smooth procedure.

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Selection of the most appropriate method of eu-thanasia in any given situation depends on the spe-cies and number of animals involved, available means of animal restraint, skill of personnel, and other con-siderations. Information in the scientific literature and available from practical experience focuses pri-marily on domesticated animals, but the same general considerations should be applied to all species.

Euthanasia must be performed in accord with ap-plicable federal, state, and local laws governing drug acquisition and storage, occupational safety, and methods used for euthanasia and disposal of animals, with special attention to species requirements where possible. The AVMA encourages those responsible for performing euthanasia of nonhuman animals to re-view current federal, state, and local regulations. If drugs have been used, careful consideration must be given to appropriate disposal of the animal’s remains and steps should be taken to avoid environmental contamination or harm to other animals.

Circumstances may arise that are not clearly cov-ered by the Guidelines. Whenever such situations arise, a veterinarian experienced with the species should apply professional judgment, knowledge of clinically acceptable techniques, professional ethos, and social conscience in selecting an appropriate technique for ending an animal’s life.

It is imperative that death be verified after eutha-nasia and before disposal of the animal. An animal in deep narcosis following administration of an inject-able or inhalant agent may appear to be dead, but might eventually recover. Death must be confirmed by examining the animal for cessation of vital signs.

Consideration should be given to the animal species and method of euthanasia when determining appro-priate criteria for confirming death.

Safe handling and disposal of the resulting ani-mal remains are also critically important when the presence of zoonotic disease, foreign animal diseas-es, or other diseases of concern to population health is suspected. Appropriate diagnostic samples should be collected for testing, pertinent regulatory authori-ties should be notified, and the animal’s body should be incinerated, if possible. Use of personal protective equipment and precautions for handling biohazard-ous materials are recommended. Animals that have injured humans may require specific actions to be taken depending on local and state laws.

I5.1 CONSCIOUSNESS

AND UNCONSCIOUSNESS

Consciousness refers to the subjective or inner qualitative experience of an animal in question. In humans, consciousness is common during both sleep and anesthesia, as evidenced by dreaming.45 One de-fining feature of dreaming is that, even while con-scious, we do not experience our environment—we are disconnected from it. Ideally, general anesthesia prevents the experience of surgery and pain (con-nected consciousness), as well as producing behav-ioral unresponsiveness, either by inducing uncon-sciousness or by disconnecting consciousness from the environment.45

Unconsciousness, defined as loss of individual awareness, occurs when the brain’s ability to inte-grate information is blocked or disrupted. In humans, onset of anesthetic-induced unconsciousness has been functionally defined by loss of appropriate re-sponse to verbal command; in animals, by loss of the righting reflex.46,47 This definition, introduced with the discovery of general anesthesia more than 160 years ago, is still useful because it is an easily observ-able, integrated whole-animal response.

Anesthetics produce unconsciousness either by preventing integration (blocking interactions among specialized brain regions) or by reducing information (shrinking the number of activity patterns available to cortical networks) received by the cerebral cortex or equivalent structure(s). Further, the abrupt loss of consciousness that occurs at a critical concentration of anesthetic implies that the integrated repertoire of neural states underlying consciousness may collapse nonlinearly.48 Cross-species data suggest that memo-ry and awareness are abolished with less than half the concentration required to abolish movement. Thus, an anesthetic state (unconsciousness and amnesia) can be produced at concentrations of anesthetic that do not prevent physical movements.47

Measurements of brain electrical function have been used to objectively quantify the unconscious state. At some level between behavioral unrespon-siveness and the induction of a flat EEG (indicating the cessation of the brain’s electrical activity and brain death), consciousness must vanish. However, EEG data cannot provide definitive answers as to onset of unconsciousness. Brain function monitors based on EEG are limited in their ability to directly indicate presence or absence of unconsciousness, es-pecially around the transition point48; also, it is not always clear which EEG patterns are indicators of ac-tivation by stress or pain.28

Physical methods that destroy or render nonfunc-tional the brain regions responsible for cortical inte-gration (eg, gunshot, captive bolt, cerebral electrocu-tion, blunt force trauma, maceration) produce instan-taneous unconsciousness. When physical methods directly destroy the brain, signs of unconsciousness include immediate collapse and a several-second pe-riod of tetanic spasm, followed by slow hind limb movements of increasing frequency49–51 in cattle;

however, there is species variability in this response.

The corneal reflex will be absent.52 Signs of effective electrocution are loss of righting reflex, loss of eye-blink and moving object tracking, extension of the limbs, opisthotonos, downward rotation of the eye-balls, and tonic spasm changing to clonic spasm, with eventual muscle flaccidity.53,54

Decapitation and cervical dislocation as physical methods of euthanasia require separate comment.

The interpretation of brain electrical activity, which

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can persist for up to 30 seconds following these methods,55–58 has been controversial.59 As indicated previously, EEG methods cannot provide definitive answers as to onset of unconsciousness. Other stud-ies60–63 indicate such activity does not imply the abil-ity to perceive pain and conclude that loss of con-sciousness develops rapidly.

Once loss of consciousness occurs (ie, there is no longer an inner qualitative experience) subsequently observed activities, such as convulsions, vocalization, reflex struggling, breath holding, and tachypnea, can be attributed to the second stage of anesthesia, which by definition lasts from loss of consciousness to the onset of a regular breathing pattern.64,65 Thus,…