Postanesthetic Shivering in Primates

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Abstract
There has been little research on the cause(s) of postanesthetic shivering (PAS) and on specific interventions. Therefore, PAS was investigated in 8 unoperated squirrel monkeys anesthetized with halothane-N2O mixture. Shivering developed in all monkeys in which body temperature was allowed to decrease (mean .+-. SEM [standard error of the mean] 2.8 .+-. 0.6.degree. C) during anesthesia. Shivering occurred in 25% of animals in which body temperature was actively maintained at preanesthetic levels during anesthesia. No shivering occurred in animals warmed both during and after anesthesia. Application of radiant heat to the skin stopped PAS immediately, even though deep body temperature remained low; shivering resumed within seconds after this heating was discontinued. Intracerebroventricular (0.1-2 mg) and i.v. (100 mg/kg) administration of the putative inhibitory neurotransmitter taurine also stopped the shivering in preliminary experiments, but central injection of .alpha.-MSH (100-300 .mu.g), an endogenous antipyretic, did not. The results implicate reduced body temperature and activation of central heat production pathways as major factors in PAS and suggest that halothane-N2O anesthesia per se, elevation of the thermal set-point, and surgical procedures are not essential to the shivering phenomenon. The results suggest for future study 2 methods to control PAS: application of radiant heat or administration of taurine.