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Euthanasia by decapitation: Evidence that this technique produces prompt, painless unconsciousness in laboratory rodents

1992; Elsevier BV; Volume: 14; Issue: 4 Linguagem: Inglês

10.1016/0892-0362(92)90004-t

1872-9738

R.Robert Holson,

Anesthesia and Neurotoxicity Research

Rapid euthanasia of laboratory rodents without the use of anesthesia is a necessary research technique whenever there is the likelihood of anesthesia or stress interfering with the chemistry of the tissues under investigation. Decapitation has long been the procedure of choice under such circumstances. Recently, however, the American Veterinary Medical Association (AVMA) panel on euthanasia recommended that decapitation be avoided on the grounds that the decapitated head may be conscious and suffering for as much as 15 seconds. The panel further recommended that if decapitation was scientifically necessary, the decapitated head be immediately immersed in liquid nitrogen. These AVMA guidelines now enjoy regulatory status; the recommendation that decapitation be avoided has thus caused considerable difficulty for all research requiring rapid, anesthesia-free collection of tissues. The scientific validity of these recommendations is consequently a matter of great practical as well as theoretical importance. The decision to discourage decapitation appears to have been based on a single literature report claiming that the EEG of the decapitated head revealed conscious suffering for more than 10 seconds (Mikeska and Klemm 1976). This review carefully examines the scientific literature on this subject. It is concluded that the report by Mikeska and Klemm of EEG activation in the decapitated head is correct, but that this phenomenon is also seen when the decapitated head is under deep anesthesia, and in normal brains under ether anesthesia or during REM sleep. Hence these findings do not demonstrate either consciousness or the perception of pain. Furthermore, a substantial body of research indicates that unconsciousness due to hypoxia must occur in the decapitated head in at most 6 and more probably less than 3 seconds. Moreover, even if the decapitated head is conscious for some seconds, high cervical section immediately severs sensory input from the head and neck region to the brain. Thus, the severed head is anatomically incapable of experiencing substantial pain in the region of major trauma. Finally, no evidence was found to support the recommendation that the severed head be immersed in liquid nitrogen. It is, accordingly, urged that the AVMA panel recognize that decapitation produces rapid, pain-free unconsciousness in rodents, and that they alter their recommendations to allow rodent decapitation without qualification. Due to the rapidity of unconsciousness, it is further urged that the disposition of the severed head be left up to the investigator, without requiring immersion in liquid nitrogen or any other mandatory technique.