Vascular resistance and venous blood K⁺ during hypothermia in skeletal muscle

¹ Department of Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina

Parameters of vascular resistance, perfusion pressure, and blood flow were measured as the temperature of the isolated gracilis (dog) muscle and perfusing blood was lowered continuously from approximately 37.5 C to 25 C. The rate of change of temperature varied from 4.20 C/min to 0.13 C/min. At the rapid rate of lowering the temperature, the vascular resistance of the muscle decreased and then increased. As the rate of lowering the temperature was decreased this response progressively changed to only an increased resistance. Eight experiments were performed in which the potassium concentration of the venous whole blood and plasma was determined as the temperature of the muscle was lowered. There was no significant change in the mean potassium concentration of the venous whole blood during hypothermia. However, the potassium concentration of the plasma decreased continuously as the temperature was lowered. Correlation coefficients between the change in peripheral resistance and the potassium concentration of the plasma appeared to be significant at the 5% level.