Studies in balanced hypothermic perfusion

1. 1. A method of balanced hypothermic perfusion is described which permits quantitation of changes in total blood flow in increments as small as 2.5 Gm. 2. 2. The practicality of this technique is demonstrated for cardiopulmonary bypass in small animals (4.0 to 9.0 kilograms body weight). 3. 3. The total body oxygen consumption was determined during cooling to 10 ° C., after a 40-minute period of total circulatory arrest, and throughout rewarming. 4. 4. An oxygen debt was detected during the rewarming phase of all experiments. 5. 5. The administration of succinylcholine chloride throughout this period failed to alter the dimensions of the debt. 6. 6. Since the oxygen utilization during return to normothermia never exceeded the precooling (control) rate, a rapid satisfaction of this deficiency must have occurred. 7. 7. Evaluation of left ventricular stroke work was performed before and after varying periods of total circulatory arrest at 10 ° C. The postarrest studies (carried out 30 minutes after rewarming) disclosed a 10 per cent reduction in left ventricular function after 45 minutes of cardiac ischemia.