EFFECT OF INTERMITTENT DEEP HYPOTHERMIC CIRCULATORY ARREST ON BRAIN METABOLISM

The effect of intermittent systemic reperfusion during deep hypothermi c circulatory arrest was investigated in dogs to learn how the total a rrest period may be prolonged. The animals were cooled on cardiopulmon ary bypass to 18 degrees C and divided into the following three experi mental groups: group I (n = 7), 60 minutes of uninterrupted circulator y 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 w ith 10 minutes of intermittent systemic perfusion every 20 minutes dur ing the arrest period. Cerebral oxygen extraction rate increased signi ficantly during the arrest periods (p < 0.05) and returned to normal a fter each 10-minute period of systemic reperfusion in every group. Dur ing circulatory arrest, cerebral excess lactate increased in a time-de pendent manner after 20 minutes (r = 0.78; p < 0.001). Anaerobic metab olism did not increase throughout the circulatory arrest period in gro up III, although it increased significantly in groups I and II (p < 0. 05). The present data demonstrate that cerebral energy metabolism beco mes predominantly anaerobic within the first 20 minutes of deep hypoth ermic circulatory arrest, The present findings suggest that intermitte nt systemic recirculation for brief 10-minute periods every 20 minutes during circulatory arrest should prevent cerebral anaerobic metabolis m during long periods of arrest that are required to complete complica ted surgical repairs.