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.

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.

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).

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.