USE OF NEAR-INFRARED SPECTROSCOPY TO MONITOR THE REGIONAL CEREBRAL OXYGEN SATURATION AFTER HYPOTHERMIC CARDIOPULMONARY BYPASS IN BABOONS:

Purpose: Cerebral complications after cardiopulmonary bypass (CPB) with or without deep hypothermic circulatory arrest are often related to the regional cerebral oxygen saturation levels in pediatric heart surgery patients. When cerebral dysfunction occurs, the rSO2 levels are significantly decreased (more than 20% compared to the pre-CPB level). The objective of this study was to investigate the effects of hypothermic CPB (27°C) on regional cerebral oxygen saturation levels using near-infrared spectroscopy (NIRS) in baboons Methods: The study involved seven baboons (mean weight, 15 kg). A novel NIRS INVOS Pediatric Cerebral Oximeter, which has advantages of being non-invasive and continuous (in real-time), was used. The NIRS sensor was place on each animal's forehead. After initiation of CPB, all animals were subjected to 20 minutes of core cooling, 60 minutes of hypothermic CPB while the aorta was cross-clamped, and 30 minutes of normothermic CPB. During CPB, the mean arterial pressure and pump flow was 50–60 mmHg and 100 ml/kg/min, respectively. The rSO2 levels were recorded before CPB, during CPB, and 30, 60, 120, 180, and 300 minutes, liter CPB. Results: The total duration of CPB was 135 minutes. The rSO2 levels did not change during normothermic CPB compared to the pre-CPB levels (47% ± 8.5% vs. 46.7% ± 8.1%, p = NS). The rSO2 levels were slightly increased during hypothermic CPB at 27°C (53.5% ± 6%), and at the end of CPB (49% ± 7.1%). There were no decreases in rSO2 levels after 30 min (51.8%, ± 8.9%), 60 min (52.8% ± 10.2%), 120 min (53.2%±6%),180 min (52.2% ± 11.1%), and 360 minutes (54.2% ± 15.7%) post-CPB. Conclusions: In our baboon model, there was no sign of cerebral dysfunction after full-flow hypothermic CPB with 60 minutes of aortic cross-damping. The NIRS INVOS Cerebral Oximeter is an excellent tool to monitor the rSO2 during and after CPB.