The association between cerebral blood flow variations during on-pump coronary artery bypass grafting surgery and postoperative delirium

Introduction: 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. Methods: 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. Results: 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. Conclusions: 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.