Importance of fasting in the lymphocyte calcium test for malignant hyperthermia

Anaesthetic-induced increases in cytoplasmic free Ca2+ have been reported to be greater in lymphocytes from malignant hyperthermia (MH) susceptible patients than in those from controls, suggesting that this may be the basis for a less invasive test for MH susceptibility. In the present study the cytoplasmic Ca2+ concentrations of lymphocytes were monitored with indo-1 in 14 control subjects (nine fasted and five nonfasted) and five fasted MH susceptible and three fasted nonsusceptible patients, diagnosed by the halothane and caffeine contracture tests. No relationship was observed between MH susceptibility and Ca2+ concentrations in lymphocytes in the absence or presence of halothane. There was, however, a relationship in control subjects between fasting and the response of lymphocytes to halothane, with the halothane-induced Ca2+ increase being considerably larger in nonfasted subjects.