Presented in order of most common citation to least frequent citation.
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Appendix D: Recommendations of the 2000 AVMA Panel
(See C.2.b. Euthanasia) The 2000 AVMA Panel on Euthanasia Report characterizes euthanasia methods by type:
1) Inhalant agents,
2) Noninhalant pharmaceutical agents, and
3) Physical methods.
The Panel further classifies the methods into those that are considered acceptable, conditionally acceptable and unacceptable when used as the sole means of euthanasia.
Euthanasia of Homeothermic (Warm-blooded) Animals Inhalant Agents Inhalant Anesthetics: The Panel recommends the use of halothane, enflurane, sevoflurane, methoxyflurane, isoflurane and desflurane (in order of preference) for animals under 7 kg. Although acceptable for use in larger animals these agents are not often used due to cost and difficulty in admin-istration. Induction with methoxyflurane (metofane) is unacceptably slow in some species. Ether was formerly used extensively, but is now only con-ditionally acceptable due to irritation of mucous membranes and risk of fire and explosion. Nitrous oxide (N2O) does not produce anesthesia, and may produce hypoxemia and cardiac or respiratory arrest. It may be used in combination with other anesthetics to speed anesthesia onset. It is impor-tant to minimize exposure to personnel to these potentially toxic agents; therefore fume hoods must be used.
Carbon Dioxide (CO2): Carbon dioxide is an effective and widely used agent to euthanize rodents. This method causes hypoxia attributable to depresssion of vital centers. Use of carbon dioxide generated by other methods (e.g.. dry ice, fire extinguishers) is not acceptable. Compressed CO2 gas in cylinders is the only recommended source of carbon dioxide, since the inflow to the euthanasia chamber can be regulated. An optimal flow rate will displace at least 20% of the chamber volume per minute. In some species (e.g. rats) prefilling the chamber to 70% or more will produce rapid unconsciousness with minimal distress. Young animals, and some burrowing and diving animals, are relatively resistant to the hypoxemic effect of CO2. Since the effects of carbon dioxide are reversible, it is impor-tant to ensure that the animals are dead.
Other agents: Nitrogen and argon are listed as conditionally acceptable methods for death by hypoxemia, and are relatively safe. Although effect-tive, they may cause distress and other methods are preferred. Carbon monoxide induces unconsciousness without significant discomfort, and is considered acceptable for euthanasia for dogs, cats, and other small mam-mals. However, it is dangerous to use, and the Panel recommends it only if proper precautions are observed.
Non-inhalant Agents Barbiturates: Injection of barbiturates, particularly sodium pentobarbital, is the most rapid and reliable method of euthanasia for most research animals. In non-rodent species, barbiturates are given intravenously to be most effective. A sedative or tranquilizer may be given prior to the barbiturate in animals that are difficult to restrain. Intraperitoneal injection is also accept-able when necessary if restraint or intravenous administration would be more stressful. In rodent, intravenous barbiturate for euthanasia is not common, since equally humane and less time-consuming methods are available. Intraperitoneal injection of barbiturate is acceptable for eutha-nasia in small mammals.
Sodium pentobarbital is listed as a Schedule II drug by the U.S. Drug Enforcement Administration (DEA). Current federal drug regulations require strict accounting for barbiturates, and they must be used under the super-vision of personnel registered with the DEA. Some effective euthanasia solutions contain barbiturates in combination with other agents, and are listed Schedule III and are less restricted in use.
Potassium Chloride (KCl): KCl induces immediate cardiac arrest without any significant depression of the central nervous system. Hence, it must only be used after the animal is deeply anesthetized.
Neuromuscular Blocking Agents(Succinycholine, Curare, etc): These drugs induce muscular paralysis and death by suffocation. They are not accept-able for euthanasia.
Physical Methods Physical methods are sometimes necessary to obtain scientifically valid data and, while aesthetically displeasing to some individuals, are humane when properly performed by skilled and experienced personnel with appro-priate, well-maintained equipment. The Panel considers most physical methods to be conditionally acceptable.
Cervical Dislocation: This is frequently used for mice, poultry and other small birds, immature rats weighing less than 200 grams and rabbits weigh-ing less than one kilogram. Cervical dislocation is described in the 2000 AVMA Report as a humane technique for euthanasia of rodents and small rabbits in research, which induces rapid loss of consciousness without chemically contaminating tissue. Its use must be scientifically justified and approved by the IACUC on a case-by-case basis. As part of the approval process the IACUC must be assured that the personnel are appropriately qualified in the use of this method for the specific species involved. It is critical that personnel performing these procedures are thoroughly trained, usually by practicing the procedure on anesthetized animals.
Decapitation: Decapitation may be used to euthanize rodents and small rabbits. Except in neonatal animals, a guillotine is generally used. The sec-tion should be through the atlanto-occipital joint. The 2000 AVMA Report recommends that decapitation be done only when scientifically justified and approved by the IACUC on a case-by-case basis. As part of the approval process the IACUC must be assured that the personnel are appropriately skilled in the use of this method for the specific species involved.
Microwave Irradiation: This method is used when a project requires fixation of mouse or rat brain metabolites in vivo without losing anatomic integrity of the brain. Commercial microwave chambers will render a rodent uncon-scious in less 100 msec. and dead in under one second. These instruments differ from household units in that they direct most of the microwave energy at the head of the animal. Only instruments designed for this purpose and having the appropriate power and microwave distribution may be used.
Penetrating Captive Bolt: This method is conditionally acceptable for rumi-nants, horses, and swine when chemical agents are scientifically contra-indicated. Use of a non-penetrating captive bolt only stuns and should not be attempted as the sole means of euthanasia.
Euthanasia of Poikilothermic (Cold-blooded) Animals The 2000 Report of the AVMA Panel on Euthanasia addressed the euthana-sia of poikilothermic animals and in doing so pointed out that the available objective information on these species in the literature limits the guidelines that can be developed. The Panel also pointed out the differences in the metabolism, respiration and tolerance to cerebral hypoxia between these species and homeothermic animals must be considered when selecting a method of euthanasia.