Cerebral oxygenation during pediatric cardiac surgery using deep hypothermic circulatory arrest

Abstract

Background: Deep hypothermic circulatory arrest is a widely used technique in pediatric cardiac surgery that carries a risk of neurologic injury. Previous work in neonates identified distinct changes in cerebral oxygenation during surgery. This study sought to determine whether the intraoperative changes in cerebral oxygenation vary between neonates, infants, and children and whether the oxygenation changes are associated with postoperative cerebral dysfunction. Methods: The study included eight neonates, ten infants, and eight children without preexisting neurologic disease. Cerebrovascular hemoglobin oxygen saturation (S(CO2)), an index of brain oxygenation, was monitored intraoperatively by near-infrared spectroscopy. Body temperature was reduced to 15Γ during cardiopulmonary bypass (CPB) before commencing circulatory arrest. Postoperative neurologic status was judged as normal or abnormal (seizures, stroke, coma). Results: Relative to preoperative levels, the age groups experienced similar changes in S(CO2) during surgery: S(CO2) increased 30 ± 4% during deep hypothermic CPB, it decreased 62 ± 5% by the end of arrest, and it increased 20 ± 5% during CPB recirculation (all P < 0.001); after rewarming and removal of CPB, S(CO2) returned to preoperative levels. During arrest, the half-life of S(CO2) was 9 ± 1 min in neonates, 6 ± 1 min in infants, and 4 ± 1 min in children (P < 0.001). Postoperative neurologic status was abnormal in three (12%) patients. The S(CO2) increase during deep hypothermic CPB was less in these patients than in the remaining study population (3 ± 2% versus 33 ± 4%, P < 0.001). There were no other significant S(CO2) differences between outcome groups. Conclusions: Brain oxygenation changed at distinct points during surgery in all ages, reflecting fundamental cerebral responses to hypothermic CPB, ischemia, and reperfusion. However, the changes in S(CO2) half-life with age reflect developmental differences in the rate of cerebral oxygen utilization during arrest, consistent with experimental work in animals. Certain intraoperative cerebral oxygenation patterns may be associated with postoperative cerebral dysfunction and require further study.