Malignant hyperthermia: is etomidate safe?

The safety of etomidate for induction of anesthesia in malignant hyperthermia-susceptible (MHS) pigs was evaluated in a two-phase experiment. Two litters of Purebred Poland China pigs, one MHS (n = 4) and the other malignant hyperthermia-resistant (MHR) (n = 4) were used. Phase I compared MHS vs MHR animals in terms of cardiovascular, metabolic, and skeletal muscle rigidity responses to etomidate and fentanyl anesthesia and to a subsequent malignant hyperthermia (MH) challenge with halothane-succinylcholine. When three of the four criteria for the diagnosis of MH occurred (rigidity, tachycardia, or increases in temperature or end-tidal CO2) in an animal, phase I was terminated. In phase II, only the MHS animals were used and experimental procedures were as in phase I except thiopental replaced etomidate. In phase I, evidence was inadequate to support the diagnosis of MH based upon responses of MHS pigs to the infusion of etomidate even though the infusion of etomidate in MHS pigs was associated with statistically significant increases in body temperature and plasma lactate levels above those observed in MHR pigs. Heart rate and bicarbonate levels were lower in MHS than in MHR pigs during etomidate infusion. With discontinuation of etomidate and a subsequent challenge with halothane-succinylcholine, all four pigs developed the MH syndrome within 15-30 min. Thiopental replacement of etomidate in the phase II experiment resulted in a twofold greater time (45-75 min) for halothane-succinylcholine to trigger MH in the susceptible pigs.(ABSTRACT TRUNCATED AT 250 WORDS)