INFLUENCE OF TEMPERATURE AND CIRCULATORY ARREST ON CEREBRAL BLOOD FLOW IN NEONATAL PIGLETS UNDERGOING PULSATILE CARDIOPULMONARY BYPASS

Abstract

Purpose: To investigate the influence of temperature and circulatory arrest on global and regional cerebral blood flow (CBF) during pulsatile perfusion, we performed the following studies in a neonatal piglet model. Methods: Using a pediatric physiologic pulsatile pump, we subjected six piglets to deep hypothermic circulatory arrest (DHCA) and six other piglets to hypothermic cardiopulmonary bypass (HCPB). The DHCA group underwent hypothermia for 20 minutes, DHCA for 60 minutes, cold reperfusion for 10 minutes, and rewarming for 40 minutes. The HCPB group underwent 15 minutes of cooling, followed by 60 minutes of HCPB, 10 minutes of cold reperfusion, and 30 minutes of rewarming. The following variables remained constant in both groups: pump flow (150 ml/kg/min), pump rate (150 bpm), and stroke volume (1 ml/kg). During the 60-minute aortic cross-clamp period, the temperature was kept at 18°C for DHCA and at 25°C for HCPB. Global and regional CBF (ml/100g/min) was assessed with radiolabeled microspheres. Results: The CBF was 48% lower during deep hypothermia at 18°C (before DHCA) than during hypothermia at 25°C (55±6 vs. 106±8; P<0.05). After rewarming, the global CBF was 45% lower in the DHCA group than in the HCPB group (48±7 vs. 87±15; P<0.05). Fifteen minutes after the termination of CPB, the global CBF was only 25% lower in the DHCA group than in the HCPB group (42±8 vs. 56±11; P=NS). In the right and left hemispheres, cerebellum, basal ganglia, and brainstem, blood flow resembled the global CBF. Conclusions: Both HCPB and DHCA significantly decrease the CBF during CPB. Unlike HCPB, DHCA has a continued negative impact on the CBF after rewarming. However, 15 minutes after the end of CPB, there is no statistical intragroup difference in the CBF. This may be due to the faster recovery in CBF after DHCA with pulsatile flow.