Impact of hypothermia on the response to neuromuscular blocking drugs.

Muscle strength is reduced during hypothermia, both in the presence and in the absence of neuromuscular blocking drugs. A 2 degrees C reduction in body temperature may double the duration of neuromuscular blockade. Central body and muscle temperatures decline in parallel, as long as peripheral vasoconstriction does not occur. A reduction in muscle strength must be expected at a body temperature less than 36 degrees C (corresponding to a muscle temperature of approximately 35 degrees C). Local cooling of the hand may make adductor pollicis twitch tension monitoring less useful during clinical anesthesia. The efficacy of neostigmine is maintained during mild hypothermia. The use of a nerve stimulator is strongly recommended to monitor the effect of neuromuscular blocking drugs during intraoperative hypothermia.