J.N. Lucke

Treatment of porcine malignant hyperthermia. A review based on experimental studies.

The metabolic and endocrine changes in porcine malignant hyperthermia are described and the importance of the catecholamine response emphasised. The relative effectiveness of several different therapeutic agents in the treatment of this syndrome in the Pietrain pig are described and the importance of a common link with the catecholamine response discussed.

Thermogenesis in Stress-susceptible Pigs: A Review

Stress syndromes Malignant hyperthermia (MH) is a fulminant thermogenic syndrome occurring during anaesthesia in which a hypermetabolic condition stimulates muscle to the level that would be expected during intense exercise. MH occurs rarely in human subjects (Britt & Kalow 1970), but commonly in certain breeds of pig such as the Pietrain and some strains of Landrace and Poland China pigs. Such animals are often referred to as stress-susceptible because they succumb to a variety of stress factors, showing many of the signs that would be seen in MH (Sybesma & Eikelenboom 1969). The severe stress of slaughter, for example, induces a fast rate of post-mortem muscle glycolysis in such pigs: the rapid fall in pH before cooling denatures myofibrillar protein so that intracellular water is lost. This is an economically important condition referred to as pale, soft exudative (PSE) pork (Lister 1970). The association between extreme sensitivity to stress and MH in pigs has been well established. There is some evidence which suggests that individual people and families susceptible to MH may also be particularly susceptible to stress, so that there may be analogous human and porcine stress syndromes (Wingard 1974). It is only in specific breeds of pigs that MH can be reproduced with any degree of certainty, and there is little convincing evidence that the syndrome occurs during anaesthesia in other species. However, it seems likely that stress and excitement might induce a fatal hyperthermia in some wild animals and birds through increased muscle metabolism (Harthoorn et al. 1974, Henschel & Louw 1978). This syndrome, referred to as capture myopathy, has many biochemical features in common with MH and this suggests that a thermogenic effect of catecholamines on muscle might be widespread in nature (Lucke et al. 1979).

Effect of dantrolene on leg metabolism in porcine malignant hyperthermia

The effect of the intravenous administration of dantrolene 3.5 mg/kg body weight on leg metabolism during porcine malignant hyperthermia (MH) was investigated in six Pietrain pigs. Arterial pH improved only slowly after dantrolene and was associated with the continuing efflux of lactate from the leg. Oxygen uptake by the leg had returned to control values 30 minutes after dantrolene. Glucose production by the leg was observed during malignant hyperthermia but this was rapidly abolished by dantrolene. It is concluded that the most useful indices for assessing the adequacy of the treatment of MH are those which reflect changes in oxidative muscle metabolism.