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Chapter Fourteen Euthanasia
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Research Techniques Previous units in this text have dealt primarily with the laboratory animal technician’s approach to animal care, environment and basic science. This last unit is devoted to research procedures that involve animals. Commonly, these procedures are performed or monitored by laboratory animal technicians. Also presented is a section describing some of the common research methods most animal technicians will observe as part of their animal care duties.
Euthanasia Euthanasia is “act of inducing painless death.” Other terms are; “put to sleep” or “sacrifice.” AVMA, in its 2000 Report of the AVMA Panel on Euthanasia, published criteria for painless death. Report is recommended reading for any technician who wants to develop a thorough understanding. Experiments require tissue exam after death. Painless methods of euthanasia fail to halt reflexive body actions immediately after death. Emotional distress experienced as a result of euthanizing an animal is a perfectly normal.
Euthanasia II Everyone involved in euthanizing animals will experience anxiety at some time or another. Some people will be more affected than others, & the procedure is never something you should get used to. To be more at ease with the use of various euthanasia procedures, animal technicians must have a basic understanding of subject. This understanding will ensure the procedure is always performed in a caring, humane & safe manner, with minimal anxiety for animal.
Euthanasia Methods Chemical or physical Chemical - either inhaled or injected Several are actually anesthetic agents that when given as an overdose result in rapid, painless death. Physical methods require mechanical devices. Intravenous injection & cervical dislocation require considerable practice. Handle in a way that avoids fear & apprehension. Not done in presence of other animals. Verified by determining that heart has completely stopped beating & all respiration has ceased.
Inhalant Chemicals Methoxyflurane, isoflurane and halothane are nonflammable, non-explosive inhalants. produce rapid anesthesia Cotton soaked w/ liquid anesthetic placed in bottom of chamber, under a grate, so animals cannot come in contact with cotton. After liquid has vaporized in chamber, animals are placed in chamber and cover is secured.
CO 2 CO 2 reasonably safe for handler and effective & inexpensive, especially for rodents. Its use does not require a fume hood if the room is well ventilated. Compressed gas, usually a mixture of oxygen & CO 2, is supplied in a metal cylinder. Carbon dioxide is colorless, odorless & heavier than air, and is easily emptied from cylinder into a top- opening chamber or bag. Neonatal animals require much longer exposure to CO 2 in order to cause death.
Injectable Chemicals 4 injectable agents listed in AVMA report as “Acceptable IV.” IV is preferred but some can be given via other routes; decision must be left to an individual with experience & expertise. Pentobarbital (barbiturates) produces rapid anesthesia & death. safe when used as intended & usually inexpensive disadvantage is potential for human abuse Drug Enforcement Admin. (DEA) controlled Careful record keeping & inventory control of these substances is necessary.
Physical Methods Cervical dislocation is a method of rapidly breaking the neck. Useful when tissues must be free from drug residues. Only for poultry, mice or rats weighing <200 g, & rabbits weighing <1 kg. Sedate or lightly anesthetize prior to cervical dislocation if O.K. with experiment. Decapitation using guillotine; head is severed at atlas/axis joint of neck. Only use on conscious animals if IACUC has verified it is essential for project & prior induced unconscious- ness would invalidate research data.
Additional Reading “2000 Report of the AVMA Panel on Euthanasia.” J. Am. Vet. Med. Assoc. 202(2), Fox, J.G., Cohen, B., and Loew, F.M. Laboratory Animal Medicine. Academic Press, Orlando, FL., Pekow, C.A. “Suggestions from Research Workers for Coping with Research Animal Death.” Lab Animal, 23 (10), Walshaw, S.O. “Animal Death and Human Emotion in the Laboratory.” Lab Animal, 23 (10), 1994.