Contractures in skeletal muscle of malignant hyperthermia susceptible patients after in vitro exposure to sevoflurane

Background: Sevoflurane, a potent inhalational anaesthetic agent that is st ructurally similar to halothane, has some favourable characteristics, but m ay also be able to trigger malignant hyperthermia (MH) in susceptible patie nts. The diagnosis of malignant hyperthermia susceptibility relies on the i n vitro contracture test on skeletal muscle. The present study was undertak en to investigate whether exposure to sevoflurane of muscles of malignant h yperthermia susceptible (MHS) patients would also cause an abnormal contrac ture. Methods: Muscle fascicles obtained from three MHS patients, one malignant h yperthermia non-susceptible (MHN) patient, two control patients and one mal ignant hyperthermia equivocal (MHE) patient were exposed to sevoflurane ins tead of halothane in the ill vitro contracture test, carried out according to the protocol of the European Malignant Hyperthermia Group. The muscle fa scicles were surplus to diagnostic requirements. Sevoflurane concentrations in the testbath were measured using a headspace gas chromatographic techni que. Results: The kinetics of sevoflurane concentration in the testbath were sim ilar to those of halothane. An in vitro contracture response of 2 mN or mor e was seen in all four MHS/MHE patients with sevoflurane but not in the thr ee control/MHN patients. The magnitude of muscle contracture in the sevoflu rane test was less than in the conventional halothane test at comparable te stbath concentrations. Conclusions: Sevoflurane can trigger an abnormal contracture in human muscl e in vitro. This is indicative of malignant hyperthermia susceptibility. Ex posure to sevoflurane should be avoided in patients thought to be susceptib le to malignant hyperthermia.