The Association of Oxygen Delivery and Transfusion on Cardiopulmonary Bypass with Acute Kidney Injury

Objectives We sought to estimate whether the association of transfusion and AKI has a threshold of oxygen delivery below which transfusion is beneficial, but, above which it's harmful. Design Retrospective study Setting Cardiovascular operating room and intensive care unit. Participants Patients undergoing cardiac surgery with continuous oxygen delivery monitoring during cardiopulmonary bypass. Interventions None Measurements and Main Results We used logistic regression to estimate the association between oxygen delivery (mean, cumulative deficit, and bands of oxygen delivery), transfusion, and their interaction and AKI. A subgroup analysis using transfused and non-transfused patients with exact matching on cumulative oxygen deficit and time on bypass with adjustment for propensity to receive a transfusion using logistic regression. 991 of 4,203 patients developed AKI within 7 days. After adjustment for confounders, lower mean oxygen delivery (OR=0.968, 95% CI=0.949, 0.988, p=0.002) and transfusions (OR=1.442, 95% CI=1.077, 1.932, p=0.014) were associated with increased odds of kidney injury by 7 days. As oxygen delivery decreased, the risk of AKI increased, with the slope of the odds ratio steeper below <160 mL/m2/min. In the subgroup analysis, matched transfused patients were more likely to develop AKI (145 [45%] v 101 [31%], p <0.001) than matched non-transfused patients. However, after propensity scoring adjustment, this was non-significant (OR=1.181, 95% CI=0.796, 1.752; p=0.406). Conclusions We found a non-linear relationship between oxygen delivery and AKI. We found no level of oxygen delivery at which transfusion was associated with a lessening of the risk of AKI.