LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II ...

20 LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II63. Section title EUTHANASIASeveral techniques are available for euthanasia, the rapid, painless,and minimally distressing killing of rats and mice. The NAS Guidemandates that individuals performing euthanasia procedures beadequately trained and experienced and use approved techniques andagents in accordance with guidelines established by the 1993 Reportof the American Veterinary Medical Association Panel onEuthanasia (1, 2).64. Euthanasia methods Three general methods of euthanasia used in rats and mice are:1. Inhalant agents (carbon dioxide, halothane, isoflurane, etc.)sufficient to cause respiratory depression and death;2. Injectable drugs, such as an overdose of barbituric acidderivatives or highly concentrated pentobarbital agents;3. Physical methods, such as cervical dislocation, decapitation, orfocused microwave irradiation. Physical methods are utilized incases where other agents would contaminate or interfere withresearch results. If this is not a concern, physical methodsshould be performed while the animal is sedated oranesthetized.65. Inhalant methodsThis image shows a mouse in an inhalation chamber.One or more animals may be placed in an inhalationchamber, precharged with gaseous anesthetic agentsor carbon dioxide, and held there until death.Overcrowding in the chamber should be avoided, as itmay produce distress in the animals and prolong theonset of anesthetic activity. When soaked materials ordry ice are used, there should be a grid or separationbetween these and the animal to prevent distressassociated with dermal contact. Chloroform should notbe used because of the risk of toxicity to workers andother animals. Ether should not be used because of itsexplosive potential. When using gaseous agents, ahood or scavenging system should be utilized toprovide protection to the technician. Carbon dioxideexposure, while rapid and effective in adult rats andmice, requires prolonged exposure times in neonatesto ensure death.66. Physical methodsThere are several physical methods of euthanasia.One method is cervical dislocation (shown) whichinvolves placing a rod or thumb and forefinger on theanimal’s neck, immediately behind the skull, as shownin this image. While holding the base of the tail, pullbackwards and up, separating the cervical vertebraefrom the skull. This severs the spinal cord and disruptsblood flow to the brain, resulting in death. Otherphysical methods include decapitation or microwaveirradiation. Commercially available focused microwaveirradiation instruments direct their energy at the brain ofthe rodent undergoing euthanasia. Microwave ovensare not acceptable.