The present role of hypothermia in cardiac surgery.

IN THE PAST DECADE hypothermia has been a subject of intense experimental and clinical study.'-6 After initial experiences showed its severe limitations for intracardiac surgery, many technics of hypothermia were gladly discarded as pump-oxygenators were developed. Subsequently, the combination of hypothermia and extracorporeal circulation has permitted degrees of hypothermia previously incompatible with survival and has made possible elective use of long periods of complete circulatory arrest. These possibilities have prompted many experimental and clinical studies to determine the safety and advantages of surgical procedures performed during circulatory arrest and "deep " hypothermia. This review describes the current status of hypothermia in this changing field of cardiac surgery. Three broad areas of current use of hypothermia can be defined. Two of these, intracardiac surgery performed with hypothermia and circulatory occlusion and hypothermia for neurologic injury from cardiac arrest, are limited in scope and are briefly presented. By far the largest of the three is the combination of hypothermia with extraeorporeal circulation. Three subdivisions can be recognized in this broad category and are considered individually: (1) moderate hypothermia with extracorporeal circulation; (2) deep hypothermia with extracorporeal circulation and periods of circulatory arrest; and (3) selective cardiac hypothermia during extracorporeal circulation.