Predicting acute kidney injury following nonemergent cardiac surgery: A preoperative scorecard

Objective: To determine the predictors of postoperative acute kidney injury (AKI) following nonemergent cardiac surgery among patients with variable preoperative estimated glomerular filtration rate (eGFR) levels. Methods: A retrospective study of patients who underwent elective or in-hospital cardiac surgical procedures was performed between January 2006 and November 2015. The procedures included isolated coronary artery bypass grafting (CABG), isolated aortic valve replacement (AVR), or combined CABG and AVR. The primary outcome AKI (any stage) following nonemergent cardiac surgery utilizing the 2012 Kidney Disease-Improving Global Outcomes (KDIGO) criteria. Patients were categorized based on the following renal outcomes: mild AKI, severe AKI (KDIGO stage 2 or 3), and postoperative dialysis. Patients with G5 preoperative kidney function (including dialysis patients) were excluded. Results: A total of 6675 patients were included in our study. The mean age was 66.8 years (SD ± 10.4), with 76.3% being males. A total of 4487 patients had normal or mildly decreased eGFR (G1 or G2) preoperatively (67.2%), while 1960 patients were in the G3 category (29.4%). Only 228 patients (3.4%) had G4 renal function. A total of 1453 (21.7%) patients experienced postoperative AKI. The need for postoperative dialysis occurred in 3.2% of the AKI subgroup. In-hospital mortality was higher among the AKI subgroup (7.2% vs. 0.5%; p <.0001). In an adjusted model, a lower preoperative eGFR category was the strongest predictor of AKI. A practical scorecard for the preoperative estimation of severe AKI for nonemergent cardiac procedures incorporating these parameters was developed. Conclusions: Preoperative eGFR is the strongest predictor of postoperative AKI in individuals undergoing nonemergent cardiac surgery. A practical scorecard incorporating preoperative predictors of AKI may allow informed decision-making and predict AKI following nonemergent cardiac surgery.