Preoperative proteinuria predicts adverse renal outcomes after coronary artery bypass grafting

Abstract

Whether preoperative proteinuria associates with adverse renal outcomes after cardiac surgery is unknown. Here, we performed a secondary analysis of a prospectively enrolled cohort of adult patients undergoing coronary artery bypass grafting (CABG) at a medical center and its two affiliate hospitals between 2003 and 2007. We excluded patients with stage 5 CKD or those who received dialysis previously. We defined proteinuria, measured with a dipstick, as mild (trace to 1+) or heavy (2+ to 4+). Among a total of 1052 patients, cardiac surgery-associated acute kidney injury (CSA-AKI) developed in 183 (17.4%) patients and required renal replacement therapy (RRT) in 50 (4.8%) patients. In a multiple logistic regression model, mild and heavy proteinuria each associated with an increased odds of CSA-AKI, independent of CKD stage and the presence of diabetes mellitus (mild: OR 1.66, 95% CI 1.09 to 2.52; heavy: OR 2.30, 95% CI 1.35 to 3.90). Heavy proteinuria also associated with increased odds of postoperative RRT (OR 7.29, 95% CI 3.00 to 17.73). In summary, these data suggest that preoperative proteinuria is a predictor of CSA-AKI among patients undergoing CABG.

Figure 1.

Unadjusted risk for postoperative AKI, RRT, and 30-day all-cause mortality in patients with different severities of proteinuria and CKD stage. The unadjusted risk for adverse outcomes (AKI, RRT, and 30-day all-cause mortality) increased stepwise in each group of CKD stage (A) and severity of proteinuria (B). Comparison of patients with CKD stage 4 or normal proteinuria: *P < 0.05; ***P < 0.001.

Figure 2.

Conditional effect plot of baseline CKD stage and severity of proteinuria on estimated probability of AKI in 1052 patients with postcoronary artery bypass grafting surgery. The condition effect plot was drawn under the following conditions: patients with diabetes mellitus, recent myocardial infarction, and nonelective surgery but without IABP. Patients with mild or heavy proteinuria had a higher risk of postoperative AKI, even after adjusting for CKD stage.