Low Oxygen Delivery as a Predictor of Acute Kidney Injury during Cardiopulmonary Bypass.

Low indexed oxygen delivery (DO2i) during cardiopulmonary bypass (CPB) has been associated with an increase in the likelihood of acute kidney injury (AKI), with critical thresholds for oxygen delivery reported to be 260-270 mL/min/m2. This study aims to explore whether a relationship exists for oxygen delivery during CPB, in which the integral of amount and time below a critical threshold, is associated with the incidence of postoperative AKI. The area under the curve (AUC) with DO2i during CPB above or below 270 mL/min/m2 was calculated as a metric of oxygen delivery in 210 patients undergoing CPB. To determine the influence of low oxygen delivery on AKI, a multivariate logistic regression model was developed including AUC < 0, Euroscore II to provide preoperative risk factor adjustment, and incidence of red blood cell transfusion to adjust for the influence of transfusion. Having an AUC < 0 for an oxygen delivery threshold of 270 mL/min/m2 during CPB was an independent predictor of AKI, after adjustment for Euroscore II and transfusion [OR 2.74, CI {1.01-7.41}, p = .047]. These results support that a relationship exists for oxygen delivery during CPB, in which the integral of amount and time below a critical threshold is associated with the incidence of postoperative AKI.