CEREBRAL OXYGENATION DURING PEDIATRIC CARDIAC-SURGERY USING DEEP HYPOTHERMIC CIRCULATORY ARREST

Background: Deep hypothermic circulatory arrest is a widely used techn ique in pediatric cardiac surgery that carries a risk of neurologic in jury. Previous work in neonates identified distinct changes in cerebra l oxygenation during surgery. This study sought to determine whether t he intraoperative changes in cerebral oxygenation vary between neonate s, infants, and children and whether the oxygenation changes are assoc iated with postoperative cerebral dysfunction. Methods: The study incl uded eight neonates, ten infants, and eight children without preexisti ng neurologic disease. Cerebrovascular hemoglobin oxygen saturation (S c-O2), an index of brain oxygenation, was monitored intraoperatively b y near-infrared spectroscopy. Body temperature was reduced to 15 degre es C during cardiopulmonary bypass (CPB) before commencing circulatory arrest. Postoperative neurologic status was judged as normal or abnor mal (seizures, stroke, coma). Results: Relative to preoperative levels , the age groups experienced similar changes in Sc-O2 during surgery: Sc-O2 increased 30 +/- 4% during deep hypothermic CPB, it decreased 62 +/- 5% by the end of arrest, and it increased 20 +/- 5% during CPB re circulation (all P < 0.001); after rewarming and removal of CPB, Sc-O2 returned to preoperative levels. During arrest, the half-life of Sc-O 2 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 Sc-O2 increase during deep hypothermic C PB was less in these patients than in the remaining study population ( 3 +/- 2% versus 33 +/- 4%, P < 0.001). There were no other significant Sc-O2 differences between outcome groups. Conclusions: Brain oxygenat ion changed at distinct points during surgery in all ages, reflecting fundamental cerebral responses to hypothermic CPB, ischemia, and reper fusion. However, the changes in Sc-O2 half-life with age reflect devel opmental differences in the rate of cerebral oxygen utilization during arrest, consistent with experimental work in animals. Certain intraop erative cerebral oxygenation patterns may be associated with postopera tive cerebral dysfunction and require further study.