[A clinical study on brain perfusion during cardiopulmonary bypass].

The purpose of this study was to determine the optimum cerebral perfusion flow rate and pressure of the selective cerebral perfusion. Blood flows of the brachiocephalic and left common carotid artery in 34 patients were continuously monitored by means of electromagnetic flow meter during cardiac operations. Radial and common carotid arterial pressure were monitored simultaneously. Arterial and internal jugular venous blood were sampled and cerebral oxygen consumption was calculated. During steady state hypothermic cardiopulmonary bypass (CPB), mean cerebral perfusion flow was about 600 ml/min at CPB flow of 2.4 L/min/m2. Cerebral oxygen consumption was decreased to 50% of the prebypass level during steady state hypothermic CPB and then it returned to prebypass level after CPB. Common carotid arterial pressure was about 10 mmHg lower than radial arterial pressure during CPB. When CPB flow was remained at 2.4 L/min/m2, left common carotid arterial flow was not affected by common carotid arterial pressure within the range of 40 to 80 mmHg. Cerebral autoregulation might be preserved at this pressure level of the common carotid artery. When CPB flow was reduced from 2.4 L/min/m2, cerebral oxygen consumption was remained constant level until the flow reached to 1.6 L/min/m2, at which cerebral perfusion flow was about 400 ml/min. Data suggest that optimum cerebral perfusion flow during the selective cerebral perfusion may be about 600 ml/min although cerebral oxygen consumption was maintained when cerebral perfusion flow was reduced to 400 ml/min. Optimum cerebral perfusion pressure was 40-80 mmHg of carotid arterial pressure and when monitored in radial artery, more than 10 mmHg higher pressure should be required.