Cerebral oxygenation and autoregulation during rewarming on cardiopulmonary bypass

BACKGROUND: Rewarming on cardiopulmonary bypass (CPB) is associated with increased metabolic demands; however, it remains unclear whether cerebral autoregulation is affected during this phase. This RCT aims to describe the effects of 20% supranormal, compared to normal CPB flow, on monitoring signs of inadequate perfusion, oxygenation, and disturbed cerebral autoregulation, during the rewarming phase of CPB. METHOD: Thirty two patients scheduled for coronary artery bypass grafting were allocated to a Control group (n = 16) receiving a CPB pump flow corresponding to preoperatively measured cardiac output, and an Intervention group (n = 16) receiving the corresponding CPB pump flow increased by 20% during rewarming. Cerebral Oximetry Index (COx) was calculated with the aid of Near Infrared Spectroscopy. RESULTS: Twenty five patients were included in the data. Results show a median COx value of 0.0 (IQR −0.33–0.5) (Control) and 0.0 (IQR −0.15–0.25) (Intervention), respectively; p = .85 with individual variations within groups. The median cerebral perfusion pressure (CPP) was 55 (52–58) (Control) and 61 (54–66) mmHg (Intervention); p = .08. No significant difference in rSO2 values was observed between the groups (58.5% (50–61) versus 64% (58–68); p = .06). CONCLUSION: The present study showed no difference between increased and normal CPB pump flow with respect to cerebral autoregulation during rewarming. Large variations in cerebral autoregulation were seen at individual level.