Effect of Hypothermia of 2 to 24 Hours on Oxygen Consumption and Cardiac Output in the Dog

¹ From the Department of Surgery, Section of Experimental Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania

The changes occurring in cardiac output and oxygen consumption in short periods of hypothermia are the same when either ether or pentobarbital sodium is used as the anesthetic agent during the induction of hypothermia. Following an initial decrease in oxygen consumption, no further change occurred as long as the body temperature was maintained at a constant level. Cardiac output, arterial-venous oxygen difference, and coefficient of oxygen utilization remain unchanged for longer periods of time than most physiologic parameters studied during prolonged hypothermia at constant temperatures. After about 14 hours they also begin to alter so that by 24 hours the changes are profound. Stagnant anoxemia and marked increased in the coefficient of O₂ utilization resulting from the markedly lowered cardiac output, which was 5% of the precooled controls, occurred.