Advances in Understanding Malignant Hyperthermia

Abstract

SUMMARY Patients with MH susceptibility are usually asymptomatic, otherwise healthy, and of all ages. New anesthetic monitoring techniques that permit the continuous analysis of expired CO2 facilitate the rapid detection and treatment of MH episodes. Because early, appropriate treatment reduces the morbidity and mortality of MH episodes, all patients receiving a general anesthetic should be monitored continuously for expired CO2 and temperature. Acute MH events should be treated immediately with intravenous dantrolene sodium. In virtually all cases, dantrolene rapidly reverses the potentially fatal hypermetabolism and skeletal muscle contracture produced by potent volatile anesthetic agents and/or succinylcholine. Dantrolene sodium should be administered in an initial dose of 2.5 mg/kg and titrated to effect. Dantrolene should be immediately accessible (within 5 minutes) in the office or operating room complex if one ever administers a potent inhalation anesthetic or succinylcholine. Because MH is the subject of active research, once an MH patient has been stabilized with initial treatment, medical personnel should contact the MH hotline consultant for the most up-to-date treatment recommendations. MH-susceptible patients may be safely anesthetized with amide local anesthetics. Potent inhalation anesthetics and succinylcholine must be totally avoided in MH-susceptible patients. Prophylactic dantrolene is generally not indicated unless the patient experiences awake MH episodes. Significant progress has been made in improving the diagnosis of MH susceptibility in patients who have not experienced a fulminant MH episode. A new MH clinical grading scale has been developed by an international MH expert panel. The North American caffeine halothane contracture test has been standardized, and minor modifications yield a test with nearly 100% sensitivity and 80% specificity. A least one molecular genetic defect responsible for MH susceptibility in pigs and humans has been identified. A molecular genetic test that accurately screens individuals preoperatively for MH susceptibility may be available by the end of this decade. The North American Malignant Hyperthermia Registry provides patient-specific clinical information to medical personnel caring for registered MH-susceptible patients. In addition, the Registry accumulates comparative data to support its MH epidemiology studies, including prediction of MH susceptibility and improvement of MH treatment protocols. Dentists, oral surgeons, and nurse-anesthetists should contact the Registry to report acute MH episodes and to obtain information on registering their patients.