Effects of cardiopulmonary bypass on cerebral blood flow in neonates, infants, and children

Cardiopulmonary bypass (CPB) management in neonates, infants, and children requires extensive alterations in temperature, pump flow rate, and perfusion pressure, with occasional periods of circulatory arrest. The effect of these alterations on cerebral blood flow (CBF) are unknown. This study was designed to determine the relation of temperature and mean arterial pressure to CBF during hypothermic CPB (18 degrees-32 degrees C), with and without periods of total circulatory arrest. CBF was measured before, during, and after hypothermic CPB with xenon-clearance techniques in 67 pediatric patients, aged 1 day-16 years. Patients were grouped based on different CPB techniques: group A, repair during moderate-hypothermic bypass at 25 degrees-32 degrees C; group B, repair during deep-hypothermic bypass at 18 degrees-22 degrees C; and group C, repair with total circulatory arrest at 18 degrees C. There was a significant correlation of CBF with temperature during CPB. CBF significantly decreased under hypothermic conditions in all groups compared with prebypass levels under normothermia. In groups A and B, CBF returned to baseline levels in the rewarming phase of CPB and exceeded baseline levels after bypass. In group C, no significant increase in CBF was observed during rewarming after total circulatory arrest (32 +/- 12 minutes) or after weaning from CPB. During moderate-hypothermic CPB (25 degrees-32 degrees C), there was no association between CBF and mean arterial pressure. However, during deep-hypothermic CPB (18 degrees-22 degrees C), there was an association between CBF and mean arterial pressure.