The Effect of Regional Hypothermia of Neuromuscular Transmission

To determine the influence of hypothermia on the neuromuscular transmission, 25 patients were studied during O2-N2O(50%)-enflurane(1-2%) anesthesia without any muscle relaxants. Ventilation was controlled to maintain normocapnia and neuromuscular transmission was monitored by delivering train-of-four(TOF) stimuli to the ulnar nerve at wrist(Accelograph, Biometer) while the circulation to the ipsilateral forearm was occluded by tourniquet for 20 minutes. Regional hypothermia was induced to the isolated arm by intravenous injecton of 20ml normal saline cooled by 10℃ and by surface cooling with ice pack in 15 patients (hypothermia group). To compare the neuromuscular transmission in hypothermia with 10 patients in normothermia whose temperature were maintained at normothermia by intravenous injection of 20ml normal saline of 36℃(normothermia group), TOF response was measured following temperature gone down. The results obtained were as follows. First twitch height of TOF response(T1) was not changed, significantly in normothermia group for 20 minutes. In hypothermia group, T1 was decreased insignificantly until the temperature fell to 32℃, but it began to decrease significantly from below 31℃ as compared to normothermia group, e. g., 82.4±31.2/o(p