Variations in onset of porcine malignant hyperthermia.

Variations in the onset of malignant hyperthermia were observed in five Poland China swine. These pigs were equivalently susceptible to malignant hyperthermia, based on the rapid onset in response to mask inhalation induction with halothane (five pigs) or sevoflurane (two pigs). A moderate dose of thiopental delayed the response to sevoflurane 10 minutes (one pig) and larger doses delayed it more than 60 minutes (two pigs). Total paralysis with pancuronium in the absence of other drugs delayed the response to halothane 30 and 60 minutes (two pigs). The results suggest that drugs that decrease either neuromuscular transmission or reflex responsiveness can delay the onset of episodes of malignant hyperthermia. These data suggest pancuronium as a relaxant of choice in anesthesia for susceptible subjects. Correlation with other data suggests that malignant hyperthermia may be difficult to initiate in subjects paralyzed by non-depolarizing relaxants in the absence of exposure to potent volatile agents. Thus the use of relaxant-induced paralysis might aid in the care of patients who develop recurrent malignant hyperthermia.