Anesthesia & Analgesia, Vol 82, 803-809, Copyright © 1996 by International Anesthesia Research Society
Prior hypothermia attenuates malignant hyperthermia in susceptible swine
PA Iaizzo, CH Kehler, RJ Carr, DI Sessler and KG Belani
Department of Anesthesiology, University of Minnesota, Minneapolis, USA.
This study was designed to determine the extent by which mild or moderate
hyperthermia attenuates the triggering of malignant hypothermia (MH)
induced by the combined administration of halothane and succinylcholine.
Sixteen susceptible swine were initially anesthetized with nontriggering
drugs and then either kept normothermic (approximately equal to 38 degrees
C, n = 6) or cooled to induce mild (approximately equal to 35 degrees C, n
= 6), or moderate (approximately equal to 33 degrees C, n = 4) hypothermia.
Next, after a 30-min control period, the normothermic and mildly
hypothermic animals were administered 1 minimum alveolar anesthetic
concentration (MAC) halothane followed by a bolus dose of succinylcholine
(2 mg/kg). Within 10 min all normothermic animals developed fulminant MH,
whereas the onset of MH was slowed or was absent in the mildly hypothermic
group. To test whether moderate hypothermia could more effectively minimize
the signs of a MH episode, this group of animals was exposed to 1.5 MAC
halothane followed 10 min later by a 3-mg/kg bolus of succinylcholine. MH
was not induced and anesthesia was then changed to nontriggering drugs
(ketamine and pancuronium). The animals were then aggressively rewarmed to
38 degrees C: a slight increase in the ETCO2 was detected, but MH episodes
did not spontaneously occur. Subsequently, the readministration of
halothane and succinylcholine rapidly provoked fulminant MH. We concluded
that the induction of mild hypothermia impairs triggering and reduces the
progression of MH induced by the combined administration of halothane and
succinylcholine, whereas moderate hypothermia was completely protective and
thus could be considered for prophylaxis.
