The Duration of Postoperative Acute Kidney Injury Predicts In-Hospital Mortality in Surgical Patients

Backgrounds: It has been known that severity of acute kidney injury can predict in-hospital and long term mortality. Recently, an additional parameter, duration of acute kidney injury (AKI), might allow better prediction of in-hospital mortality. We aimed to determine if duration of AKI adds additional prognostic information in postoperative patients with AKI. Methods: The study enrolled surgical patients who were admitted to the intensive care unit. AKI cases were defined by RIFLE (risk, injury, failure, loss and end-stage renal failure) criteria and categorized according to tertiles of AKI duration: first tertile, less than 1 day; second tertile, 2 - 5 days; third tertile, greater than or equal to 6 days. The hazard ratios (HRs) for in-hospital mortality after adjust multiple covariates compared to those without AKI were recorded . The predictability of mortality was accessed by calculating the area under the curve (AUC) of receiver operating characteristic curve. Results: In total, 504 postoperative patients with 377 developed AKI (first tertile: 124 cases, second tertile: 140 cases, third tertile: 113 cases) and 127 without AKI were enrolled. The overall in-hospital mortality was 39%. The in-hospital mortality rates were 15.7% (non-AKI), 28.2% (first tertile), 55% (second tertile), and 38.3% (third tertile) as well as the HRs for in-hospital mortality were 1.632, 2.956 and 2.212 compared to non-AKI group (P = 0.201, 0.010 and 0.040). Cumulative in-hospital survival rates differed significantly for non-AKI group vs. AKI groups (first, second and third tertile) (P < 0.001 by log-rank test). The AUC of AKI duration and stage together (0.696) was higher than AKI stage alone using RIFLE criteria (0.665) (both P < 0.001). Conclusions: AKI duration was an additional predictor of in-hospital mortality in patients with postoperative acute kidney injury. World J Nephrol Urol. 2014;3(1):18-24 doi: http://dx.doi.o rg/10.14740/wjnu143 w