Rewarming Temperature During Cardiopulmonary Bypass and Acute Kidney Injury: A Multicenter Analysis

Abstract

Background: Acute kidney injury (AKI) after cardiopulmonary bypass (CPB) is associated with a requirement for dialysis, a longer stay in the intensive care unit, a longer hospital length of stay, and mortality. An oxygenator arterial outlet temperature greater than 37°C has been reported to be associated with AKI; however, the influence of other rewarming temperatures is unclear. Using multicenter registry data, this study aimed to evaluate the role of CPB rewarming temperatures on AKI.

Methods: Data from 8,407 adult patients undergoing coronary artery bypass grafting (CABG) or valve repair or replacement, or a combination, were collected using the Perfusion Downunder Collaborative Database. Primary variables of interest were rewarming temperatures, defined as cumulative time the oxygenator arterial outlet temperature was greater than 36°C, greater than 36.5°C, or greater than 37°C. Propensity scores were calculated to determine the predicted probability of hyperthermic perfusion (rewarming temperature >37°C). The influence of temperature on AKI was determined using separate multivariate models adjusting for propensity score in the entire cohort (n = 6,904) and in propensity-matched patients (n = 2,044).

Results: Overall, 11.8% of patients acquired AKI. The duration of rewarming temperature greater than 36°C or 36.5°C was not associated with AKI. The duration of rewarming temperature greater than 37°C (hyperthermic perfusion) was independently associated with RIFLE (Risk, Injury, Failure, Loss, End-stage renal disease) risk classification or greater (odds ratio [OR], 1.42; 95% confidence interval [CI], 1.09-1.77; p = 0.012) and injury classification or greater AKI (OR, 1.52; 95% CI, 1.09-1.97; p = 0.016) in the entire cohort, and injury classification or greater AKI (OR, 1.51; 95% CI, 1.15-1.90; p = 0.006) in propensity-matched patients.

Conclusions: The duration of hyperthermic perfusion-rewarming temperature greater than 37°C-was an independent predictor of AKI. Avoidance of hyperthermic perfusion may be more beneficial in reducing AKI than avoidance of rewarming.