EFFECT OF COCAINE ON THE CONTRACTURE RESPONSE TO 1-PERCENT HALOTHANE IN PATIENTS UNDERGOING DIAGNOSTIC MUSCLE BIOPSY FOR MALIGNANT HYPERTHERMIA

Two case reports have cited the recreational use of cocaine as possibl e trigger of a malignant hyperthermia (MH) crisis. We evaluated whethe r toxic concentrations of cocaine altered the in vitro muscle response to halothane during contracture tests for MH. Twenty-two patients wer e studied. Muscle biopsies were obtained and first tested for MH susce ptibility with 3% halothane and caffeine contracture testing. Ten pati ents were diagnosed as MH-susceptible and 12 as MH non-susceptible, in accordance with the North American Malignant Hyperthermia Group proto col. Then, muscle strips were exposed to 1% halothane in the presence and absence of 0.1 mmol . L(-1) cocaine. Cocaine alone did not affect baseline muscle tension in either group. With 1% halothane, MH non-sus ceptible muscle showed no contracture with or without cocaine. In cont rast, in the presence of 1% halothane, MH non-susceptible muscle showe d either no change in contracture (six patients), an increase (two pat ients), or a decrease (two patients) when exposed to cocaine. However, the overall effect of cocaine on muscle contracture in the presence o f 1% halothane was insignificant in both groups. We conclude that coca ine, even at toxic levels, does not have a direct effect on skeletal m uscle contractility and thus is safe for MH-susceptible patients.