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Profound hypothermia is used for circulatory arrest during cardiovascular operations. Cold retrograde cerebral perfusion enhances cerebral protection during circulatory arrest. This study examines the results of circulatory arrest under moderate systemic hypothermia and cold retrograde cerebral perfusion.Circulatory arrest under moderate systemic hypothermia (nasopharyngeal temperatures of 19° to 28°C, mean of 23°C) and cold (10°C) retrograde cerebral perfusion were employed in 104 consecutive patients for operation on the proximal aorta (103 patients) or for a venous tumor invading the heart (1 patient). Aortic operations consisted of replacement of the entire transverse arch in 49 patients, hemiarch in 16, ascending aorta in 37, and an extraanatomic aortic bypass in 1. Most patients (83%) also had other procedures such as coronary artery bypass or an aortic valve operation. Sixteen patients had had previous aortic operations. The mean circulatory arrest time was 27 minutes (range, 6 to 105 minutes).There were eight in-hospital deaths. Preoperative shock, peripheral vascular disease, and previous aortic operations were independent predictors of operative mortality. There were eight strokes; clinical assessment and computed tomographic scans of the brain suggested that the strokes were embolic in 6 patients. Atherosclerosis/laminated thrombi in the aorta and the duration of circulatory arrest were independent predictors of stroke. Four patients had seizures without neurologic deficit. No patient had development of paraplegia or paraparesis.Systemic hypothermia of 23°C (nasopharyngeal) and cold retrograde cerebral perfusion (10°C) appear to be safe for circulatory arrest times of less than 30 minutes. This strategy of cerebral protection may also be adequate for longer circulatory arrest times.