EFFECT OF TEMPERATURE-VARIATION (22-DEGREES-C-44-DEGREES-C) ON HALOTHANE AND CAFFEINE CONTRACTURE TESTING IN NORMAL HUMANS

Background: Malignant hyperthermia (MH) susceptibility is diagnosed us ing halothane-caffeine contracture testing of a muscle sample maintain ed at 37 degrees C. However, there has not been a systematic study tha t examines the effect of different temperatures on the response of nor mal muscle to halothane and caffeine. We hypothesized that altering ba th temperature would modify the contracture responses. Methods: We obt ained muscle samples from 20 patients undergoing surgical procedures o f the lower extremities. The samples were dissected into 245 bundles a nd the bundles were exposed to halothane 3% or incremental caffeine, a ccording to the North American MH group protocol. Several bundles from each patient were simultaneously studied at four different temperatur es (22 degrees C, 30 degrees C, 37 degrees C and 44 degrees C). Each b undle was studied at only one temperature, the muscle samples of 3 pat ients were simultaneously studied at all four temperatures for halotha ne and caffeine. Results: Maximum contracture to caffeine (32 mM) was highest at 37 degrees C; however, at lower caffeine concentrations (2- 4 mM), there was no consistent effect of temperature on contracture re sponse. Likewise, temperature did not alter contracture responses to h alothane. The extremes of temperature (22 degrees C and 44 degrees C) were associated with lack of twitch in response to electrical stimulat ion. For the bundles exposed to halothane at 22 degrees C, the absence of a twitch was associated with the presence of a contracture, althou gh these were never above the diagnostic threshold. Conclusions: We co nclude that temperature has little effect on responses of normal muscl e to halothane and caffeine. (C) Acta Anaesthesiologica Scandinavica 4 0 (1996).