Postoperative delirium (POD) has a major impact on patient recovery after cardiac surgery. Although its pathophysiology remains unclear, there could be a correlation between cerebral blood flow (CBF) variations during cardio-pulmonary bypass (CPB) and POD. Our study aimed to evaluate whether variations in on-pump CBF, compared to pre-anesthesia and pre-CPB values, are associated with POD following coronary artery bypass grafting (CABG) surgery.

This prospective observational cohort study included 95 adult patients undergoing elective on-pump CABG surgery. Right middle cerebral artery blood flow velocity (MCAV) was assessed using Transcranial Doppler before anesthesia induction, before CPB and every fifteen minutes during CPB. Pre-anesthesia and pre-CPB values were chosen as baselines. Individual values, measured during CPB, were converted as percentage changes relative to these baselines and named as %MCAV₀ and %MCAV₁, respectively. POD was assessed using the Confusion Assessment Method for ICU (CAM-ICU) during the first 48 post-operative hours and with the 3-Minute Diagnostic Interview for Confusion Assessment Method (3D-CAM) on the fifth post-surgical day.

Overall POD incidence was 17.9%. At 30 minutes of CPB, %MCAV₀ was higher in POD group than in no-POD group (p = .05). %MCAV₀ at 45 minutes of CPB was significantly higher in POD group (87 (±17) %) than in no-POD group (68 (±24) %), p = .04. %MCAV₁ at 30 and 45 minutes of CPB were higher in POD group than in no-POD group, at the limit of statistical significance. We found %MCAV₁ > 100% in POD group, but not in no-POD group.

Significant differences in %MCAV₀ became evident after 30 minutes of CPB, whereas differences in %MCAV₁ at 45 minutes of CPB were at limit of statistical significance. In POD group %MCAV₁ was higher than 100% at 30 and 45 minutes of CPB, which is supposed to be a sign of cerebral hyperperfusion. Monitoring CBF during CPB could have prognostic value for POD.