Comparing two strategies of cardiopulmonary bypass cooling on jugular venous oxygen saturation in neonates and infants

Background.: Cerebral protection during deep hypothermic circulatory arrest is predicated on efficient and complete cerebral cooling. Institutions approach cooling quite differently. We compared two different cooling strategies in terms of measured jugular venous bulb saturations in 39 infants undergoing deep hypothermic cardiopulmonary bypass to evaluate the effect of institutional cooling practices on jugular venous bulb saturation, an indirect measure of cerebral cooling efficiency. Methods.: The patients were grouped based on the method of core cooling. In group A (n = 17), core cooling was achieved rapidly by setting the water bath temperature of the heat exchanger at 4° to 5°C, and the patient was cooled until rectal temperature and nasopharyngeal temperature were 15°C or lower. In group B (n = 22), the heat exchanger was initially set at 18°C and slowly lowered to 12°C. Hypothermic temperatures of 12°C were maintained until the nasopharyngeal temperature was 18°C or less and the rectal temperature was 20°C or lower. Once cooling was complete, blood samples were analyzed by cooximetry for determination of arterial oxygen saturation and jugular venous bulb saturation. Results.: In group A, the measured jugular venous bulb saturation was 98.0% ± 0.9% and the oxygen saturation to jugular venous bulb saturation difference was 0.3% ± 0.5%, measured at the time that institutional cooling objectives were achieved (total cooling time, 15.0 ± 0.45 minutes). In group B, jugular venous bulb saturation was 86.2% ± 12% and the oxygen saturation to jugular venous bulb saturation difference was 10.8% ± 12.2%, measured at the time that institutional cooling objectives were achieved (total cooling time, 17.5 ± 1.1 minutes) (p < 0.01). Conclusions.: Differences in cardiopulmonary bypass cooling techniques may alter the rate at which jugular bulb saturations rise. We believe this represents an indirect measure of the efficiency of brain cooling and therefore of cerebral protection.