Effect of intermittent deep hypothermic circulatory arrest on brain metabolism.

The effect of intermittent systemic reperfusion during deep hypothermic circulatory arrest was investigated in dogs to learn how the total arrest period may be prolonged. The animals were cooled on cardiopulmonary bypass to 18 degrees C and divided into the following three experimental groups: group I (n = 7), 60 minutes of uninterrupted circulatory arrest; group II (n = 7), 120 minutes of circulatory arrest with 10 minutes of intermittent systemic perfusion every 30 minutes during the arrest period; group III (n = 7), 120 minutes of circulatory arrest with 10 minutes of intermittent systemic perfusion every 20 minutes during the arrest period. Cerebral oxygen extraction rate increased significantly during the arrest periods (p < 0.05) and returned to normal after each 10-minute period of systemic reperfusion in every group. During circulatory arrest, cerebral excess lactate increased in a time-dependent manner after 20 minutes (r = 0.78; p < 0.001). Anaerobic metabolism did not increase throughout the circulatory arrest period in group III, although it increased significantly in groups I and II (p < 0.05). The present data demonstrate that cerebral energy metabolism becomes predominantly anaerobic within the first 20 minutes of deep hypothermic circulatory arrest. The present findings suggest that intermittent systemic recirculation for brief 10-minute periods every 20 minutes during circulatory arrest should prevent cerebral anaerobic metabolism during long periods of arrest that are required to complete complicated surgical repairs.