The value of moderate hypothermia during anoxic cardiac arrest for coronary artery surgery

Abstract

Anoxic cardiac arrest, as opposed to induced ventricular fibrillation, greatly facilitates accurate distal anastomosis in aortocoronary bypass surgery. In order to diminish the anoxic insult, general and topical hypothermia may be used. In an attempt to establish the value of moderate hypothermia during anoxic cardiac arrest two groups of patients were compared. In group I coronary artery bypass procedures were performed under normothermic conditions with anoxic cardiac arrest. Patients in group II underwent similar procedures but under hypothermic conditions. General body hypothermia to an esophageal temperature of 30 degrees C and topical hypothermia with iced saline lavage were used. Using these techniques, the average intramyocardial temperature was 26 degrees C. Nonfatal cardiac complications did not occur more frequently in the hypothermic group. Operative mortality was decreased from 6.3% in the normothermic group to 1.5% in the hypothermic group. However, in group II, in addition to hypothermia, a second factor in the reduction of mortality was the completeness of the revascularization procedure: 58.5% of the patients had three or more bypass grafts in the hypothermic group. The mean anoxic arrest time was over 50 min for all patients--those who survived as well as those who died with postoperative low cardiac output or myocardial infarction. Therefore, anoxic arrest time should be kept as short as possible and certainly less than 50 min. Intermittent aortic occlusion and performance of the proximal anastomoses using a partial occluding clamp on the aorta are currently being used and, together with moderate hypothermia, provide a further reduction in postoperative myocardial complications.