Predictive Capacity of Oxygen Delivery During Cardiopulmonary Bypass on Acute Kidney Injury

Background: The randomized goal-directed perfusion trial confirmed retrospective findings that a goal-directed perfusion strategy to maintain oxygen delivery index (DO₂i) during cardiopulmonary bypass greater than 280 mL/min/m² reduces the incidence of acute kidney injury (AKI). We developed a predictive model for AKI using data from the Australian and New Zealand Collaborative Perfusion Registry to determine whether these findings could be validated in a real-world clinical setting and to identify an optimal DO₂i threshold for predictive diagnostic accuracy.

Methods: Data in 19,410 cardiopulmonary bypass procedures were randomly divided into training (n = 9705) and validation (n = 9705) datasets. Multivariate logistic regression was used to determine the best predictive models for AKI (RIFLE [renal Risk, Injury, Failure, Loss of renal function and End-stage renal disease] classification), incremental predictive value of minimum cardiopulmonary bypass DO₂i, and optimal threshold.

Results: Minimum DO₂i was significantly associated with any AKI, AKI risk, and AKI injury or greater class in both datasets (validation dataset; any AKI odds ratio [OR], 0.993; 95% confidence interval [CI], 0.991-0.995; P < .001; AKI risk OR, 0.994; 95% CI, 0.992-0.996; P < .001, AKI injury or greater 0.993; 95% CI, 0.991-0.996; P < .001), representing on average a 7% increase in the likelihood of AKI for every 10-mL/min/m² decrease in DO₂i. Diagnostic accuracy was similar for both datasets, with an optimal DO₂i threshold of 270 mL/min/m². The odds of any AKI were increased by 52% in those below the threshold (OR, 1.52; 95% CI, 1.29-1.77; P < .001).

Conclusions: This study confirms previous findings that minimum DO₂i during cardiopulmonary bypass is independently associated with AKI, supporting previous findings in a broader-risk, multicenter cohort.