Objectives: The severity of acute kidney injury (AKI) has been a well-known predictor for in-hospital mortality. Whether AKI duration could predict in-hospital mortality is not clear. This study determines the association between the in-hospital mortality and AKI duration in patients after non-cardiac surgery.
Materials and methods: Surgical patients who were admitted to the ICU were enrolled. AKI cases were defined using KDIGO guidelines and categorized according to the tertiles of AKI duration (1st tertile: 2 days, 2nd tertile: 3-6 days and 3rd tertile: 7 days). The adjusted hazard ratios (HRs) for in-hospital mortality are compared to those without AKI. The predictability of mortality is accessed by calculating the area under the curve (AUC) for the receiver operating characteristic (ROC) curve.
Results: From a total of 318 postoperative patients, 98 developed AKI (1st tertile: 34 cases, 2nd tertile: 30 cases and 3rd tertile: 34 cases) and 220 had no AKI. The in-hospital mortality rates are 6.8% (non-AKI), 50% (1st tertile), 46.7% (2nd tertile) and 47% (3rd tertile). The HR's for in-hospital mortality are 7.92, 6.68 and 1.68, compared to the non-AKI group (p = 0.006, 0.021 and 0.476). Cumulative in-hospital survival rates are significantly different for the non-AKI group and the AKI groups (p < 0.001). The AUC for AKI duration and stage together (0.804) is higher than that for AKI stage and AKI duration alone (0.803 and 0.777) (both ps < 0.001).
Conclusion: In addition to severity, the duration of AKI may be a predictor of in-hospital mortality in patients, after non-cardiac surgery.
Keywords: Acute kidney injury; KDIGO stages; duration; mortality; non-cardiac surgery.