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

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 degrees 40 degrees, 42 degrees, and 43.5 degrees 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 degrees C did not result in alterations of the energy metabolism. When the i.m. temperature was raised to 43.5 degrees 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 degrees C produced a marked reduction in the osmotic resistance of the erythrocytes.