Porcine malignant hyperthermia. V: Fatal hyperthermia in the Pietrain pig, associated with the infusion of alpha-adrenergic agonists.

The effects of the administration of noradrenaline alone, and noradrenaline with either phentolamine or propranolol, on thermogenesis and substrate mobilization were investigated in six Pietrain (MH-susceptible) and six Large White (unsusceptible) pigs. The infusion of noradrenaline alone produced a significantly increased lipolytic response and a significantly decreased hyperglycaemic response in Pietrain pigs compared with the Large White breed. Although noradrenaline alone produced only a small increase in body temperature in both breeds, the administration of noradrenaline with propranolol in two Pietrain pigs was associated with the development of fatal hyperthermia. In a further experiment, phenylephrine or isoprenaline was infused into six Pietrain pigs. Three pigs, receiving phenylephrine, became hyperthermic and died, whereas isoprenaline had no effect on body temperature. The results demonstrate the importance of alpha-adrenergic stimulation to heat production in MH-susceptible pigs.