Malignant hyperthermia

Abstract

Malignant hyperthermia (MH) is a rare syndrome seen when susceptible individuals are exposed to one or more of various triggering agents, most commonly a depolarizing muscle relaxant or an inhalational anaesthetic agent. There is a dramatic rise in metabolic rate and oxygen consumption which if not treated promptly and effectively results, in the majority of cases, in the patient's death. Fatal responses to physical stress associated with the familial muscular disease known as MH are being increasingly reported in situations not related to anaesthesia or drugs. Moreover, cases of MH were recognized to be "induced" in the postoperative period when obviously the major effects of anaesthesia were no longer of important consideration. Therefore a more expanded concept of MH seems to develop, including the assumption that one of the other factors in MH is stress. The implication of this extends far beyond the scope of anaesthesiology. The acute hypermetabolic state in MH, resulting in acidosis, heat production and muscular activity is probably due to an inability to control calcium concentration within the skeletal muscle fiber, and may involve a generalized alteration in cellular or subcellular membrane permeability. The susceptibility to develop MH is controlled by several genetic factors. Evaluation of affected families is guided by in vitro analysis of drug-induced contractures in muscle biopsy specimens; a practical and reliable non-invasive test to predict the susceptibility is still being sought. At the present time there is incontrovertible evidence that the hydantoin derivate dantrolene sodium is the only known specific drug in treatment and prophylaxis of MH. A concept for the treatment of MH and guidelines for the management of a patient at risk are presented; medico legal aspects of the complication are stressed.