The limit of hyperthermic strain on skeletal muscle tissue during regional perfusion

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Abstract
In experiments with dogs (n=43), we studied the influence of different temperatures on the hind leg subjected to an isolated perfusion over a period of 1 and 2 h. The main supplying vessels of a hind leg were clamped, cannulated, and connected to an extracorporeal circulation unit which consisted of a roller pump, an oxygenator, and a heat exchanger. Whole blood was used for the regional perfusion at a flow rate of 10 ml·min−1·100 g−1 of tissue. Intramuscular (i.m.) temperatures were set at 38°, 40°, 42°, and 43.5°C, respectively. The perfusion pressure, the osmotic resistance of the erythrocytes and the metabolic status in specimens of skeletal muscle obtained at the end of the perfusion period or after an 8-day follow-up observation served as parameters. A perfusion of 1 and 2 h at temperatures of up to 42°C did not result in alterations of the energy metabolism. When the i.m. temperature was raised to 43.5°C, a significant decrease in muscular high-energy compounds and an accumulation of lactate occurred. Only under this condition was there a rise in the perfusion pressure and a drastic reduction in the blood pH value in the venous line of the extracorporeal circulation. Acidosis and hyperthermia of 43.5°C produced a marked reduction in the osmotic resistance of the erythrocytes.