Predicting cardiac surgery–associated acute kidney injury: The CRATE score

Abstract

Purpose: Acute kidney injury (AKI) is a frequent complication after cardiac surgery and is associated with increased mortality. The aim was to design a nondialytic AKI score in patients with previously normal renal function undergoing cardiac surgery. Methods: Data were collected on 909 patients who underwent cardiac surgery with cardiopulmonary bypass be- tween 2012 and 2014. A total of 810 patients fulfilled the inclusion criteria. Patients were classified as having AKI based on the RIFLE criteria. Postoperative AKI occurred in 137 patients (16.9%). Several parameters were recorded preoperatively, intraoperatively, and at intensive care unit admission, looking for a univariate and multivariate asso- ciation with AKI risk. A second data set of 741 patients, from 2 different hospitals, was recorded as a validation cohort. Results: Four independent risk factors were included in the CRATE score: creatinine (odds ratio [OR], 9.66; 95% con- fidence interval [CI], 4.77-19.56; P b .001), EuroSCORE (OR, 1.40; CI, 1.29-1.52; P b .001), lactate (OR, 1.03; CI, 1.01- 1.04; P b .001), and cardiopulmonary bypass time (OR, 1.01; CI, 1.01-1.02; P b .001). The accuracy of the model was good, with an area under the curve of 0.89 (CI, 0.85-0.92). The CRATE score retained good discrimination in valida- tion cohort, with an area under the curve of 0.81 (95% CI, 0.78-0.85). Conclusions: CRATE score is an accurate and easy to calculate risk score that uses affordable and widely available var- iables in the routine care surgical patients.