Anaesthetic-induced malignant hyperpyrexia and a method for its prediction.

The clinical syndrome of anaesthetic-triggered malignant hyperpyrexia occurring in pigs is described. This condition in the pig is considered to be the same "explosive thermal idiosyncrasy" to general anaesthesia that is manifested by humans. The condition has a strong genetic factor occurring in 25 per cent of Landrace pigs used by us. Sex has no influence on its appearance. The clinical syndrome consists of: (1) tachycardia; (2) muscle rigor; (3) tachypnoea and hyperventilation progressing to apnoea; (4) blotchy cyanosis of the skin; (5) rapid, sustained and extreme rise in temperature; (6) gross acidosis. Prognosis, once the condition is well established, is extremely poor. All attempts at treatment have failed. Histological investigation has shown change in muscle only. The significance of this change is unknown. The muscle of affected pigs shows, in comparison to normal pigs, an abnormal fall in ATP content in response to incubation and to "in vitro" exposure to halothane. This reaction provides a method of predicting the development of the syndrome. Halothane, chloroform and suxamethonium have been identified as triggering agents. The mechanism of heat production is unknown.