About 1 in 52,000 adults suffer from malignant hyperthermia, a hypermetabolic crisis that can be triggered by anesthetics or stress. More males are affected than females. The exact cause of malignant hyperthermia is unclear (it's at least partially genetic), but it is set in motion by general anesthetic agents. Lidocaine does not cause this, but most forms of general agents can, most notably halothane and succinylcholine, a muscle relaxant often used in conjunction with anesthesia. Death rates from malignant hyperthermia are between 60 and 80 percent depending on how soon it's noticed.