Erythrocyte membrane fluidity in malignant hyperthermia.

Malignant hyperthermia (MH) is a rare but serious complication of general anesthesia that potentially carries a high mortality and morbidity. It is associated with excessive release of calcium into skeletal muscle following exposure to certain drugs, including the volatile general anesthetics. Since these are recognized membrane fluidizing agents it has been speculated that this condition might represent a generalized defect in membrane physical properties either at rest or inducible by fluidizing agents. If this hypothesis were found to be correct, malignant hyperthermia might conveniently be detected by examining membrane physical properties of easily accessible cells rather than the cumbersome method of muscle biopsy currently employed. To test this hypothesis we identified patients proven to be susceptible to MH by muscle biopsy and a cohort of patients not susceptible to MH as defined by negative muscle biopsy testing. Erythrocytes were isolated from both groups and membrane physical properties examined using conventional, widely available, steady-state fluorescence polarization techniques. Erythrocyte membranes were evaluated with multiple probes both in the basal condition and following fluidization with either increasing temperature or two concentrations of a fluidizing alcohol. We report, contrary to previous publications, that no discernable differences were detectable between MH-positive or negative patients. Thus, we find no evidence for a generalized membrane defect in MH and conclude that the determination of erythrocyte membrane physical properties, by these techniques, are of no use in the preoperative screening for this disorder.