Malignant hyperthermia.

Malignant hyperthermia is now recognized as a distinct entity in anesthetic practice and can be considered as a pharmacogenetic disease of obscure etiology occuring in man and pigs with a dominant inheritance. A close association with myopathy has been noted. Commonly used muscle relaxants or anesthetic drugs can act as triggering agents in genetically susceptible patients, who develop a real hypermetabolic state, characterized by a rapid rise in body temperature, muscular rigidity, tachycardia and tachypnoea, cyanosis and severe respiratory and metabolic acidosis, the lethality being about 60%. Other clinical, biochemical and histopathological features of this condition are described. The prevention and early diagnosis of this syndrome is very important. Therefore, it is necessary in the preanesthetic evaluation, to obtain information from the patient, with regard to previous anesthetic experiences, and to have a more exact anamnesis in patients with muscular diseases or with other members of the family under suspicion. Some screening methods are described. The prognosis of malignant hyperthermia depends on an early diagnosis. Although the incidence is, fortunately, small, this condition is sufficiently significant and acute in nature to require that anesthesiologist be aware of its clinical pathophysiology and prepared to recognize and treat it promptly. Therefore body temperature should be controlled continuously in all anesthetized patients, particularly in the younger age group and especially in those in which symptoms of muscle rigor have been observed particularly after application of succinylcholine and halothane. A regime of treatment is suggested, based on current concepts of the pathogenesis. It consists in establishing effective and rapid cooling, reversal of tissue hypoxia and correction of respiratory and metabolic acidosis and hyperkalemia. Specific therapy with dantrolene sodium may prove to be an answer to this serious problem.