Effect of oxygen delivery during cardiopulmonary bypass on postoperative neurological outcomes in patients undergoing cardiac surgery: A scoping review of the literature

Background Reduced oxygen delivery (DO 2 ) during cardiopulmonary bypass (CPB) was proposed as a risk factor for the development of postoperative neurological complications (PONCs), including cerebrovascular accidents (CVA), delirium, and postoperative cognitive dysfunction (POCD). We aimed to review the current evidence on the association between intraoperative DO 2 and the incidence of PONCs. Methods MEDLINE, Embase, the Cochrane Library, and Web of Science were electronically searched to identify comparative studies from inception until July 2023 that reported the association between intraoperative DO 2 levels and the incidence of PONCs (as defined by the scales and diagnostic tools utilized by the studies’ authors) in adults patients undergoing cardiac surgery using CPB. Results Of the 2513 papers identified, 10 studies, including 21,875 participants, were included. Of these, three studies reported on delirium, two on POCD, and five on CVA. Eight studies reported reduced intraoperative DO 2 in patients who developed delirium and CVA. There was a lack of consensus on the cut-off of DO 2 levels or the correlation between the period below these threshold values and the development of PONC. Conclusions Limited data suggest that maintaining intraoperative DO 2 above the critical threshold levels and ensuring adequate intraoperative cerebral perfusion may play a role in minimizing the incidence of neurological events in adult patients undergoing cardiac surgery on cardiopulmonary bypass.