CEREBRAL LACTATE RELEASE AFTER CIRCULATORY ARREST BUT NOT AFTER LOW-FLOW IN PEDIATRIC HEART OPERATIONS

Arteriovenous (jugular bulb) differences in blood lactate were followe d throughout the procedure and until 18 hours postoperatively in 17 ch ildren undergoing congenital heart operations during profound hypother mia. Transcranial Doppler sonography was used to monitor changes in bl ood flow velocity in the middle cerebral artery. Ten children had a pe riod of total circulatory arrest (39+/-6 minutes) during profound hypo thermia (arrest group). Another 7 children had continuous but reduced pump flow (0.6 to 1.2 L/m(2)) throughout hypothermic cardiopulmonary b ypass (low-flow group). The mean age was 7.3+/-1.3 months in the arres t group and 7.9+/-2.2 months in the low-flow group. The mean time on b ypass was 90+/-10 minutes in the arrest group and 75+/-9 minutes in th e low-flow group. The velocity of blood flow in the middle cerebral ar tery decreased significantly (p<0.05) in both groups to less than 50% of the preoperative level during hypothermia and increased during and after rewarming.; Differences in blood lactate level were significantl y less than zero (p<0.05) from the start of rewarming until 3 hours af ter the end of cardiopulmonary bypass in the arrest group, whereas dif ferences in blood lactate level remained close to zero in the low-flow group. We conclude that circulatory arrest during profound hypothermi a is followed by a period with release of lactate from the brain, indi cating anaerobic cerebral metabolism and possibly disturbed cerebral a erobic metabolism. This study argues for the avoidance of circulatory arrest whenever possible.