Acute kidney injury in adult postcardiotomy patients with extracorporeal membrane oxygenation: evaluation of the RIFLE classification and the Acute Kidney Injury Network criteria.

INTRODUCTION Acute kidney injury (AKI) is one of the major complications in adult postcardiotomy patients on extracorporeal membrane oxygenation (ECMO) support. The RIFLE (the Risk of renal failure, Injury to the kidney, Failure of kidney function, Loss of kidney function and End-Stage Kidney Disease) classification and the Acute Kidney Injury Network (AKIN) criteria were proposed to identify and classify AKI recently. This study aims to evaluate the occurrence of AKI during the initial 48 h of ECMO support by using both the RIFLE classification and the AKIN criteria, and to determine which scoring tool has better capability for predicting hospital mortality of adult postcardiotomy patients with ECMO support. METHODS From 2004 to 2008, 67 patients (> or = 18 years) who received extracorporeal membrane oxygenation support after undergoing cardiac surgery were enrolled and retrospectively evaluated. RESULTS The average age was 50.5+/-13.6 years; 48 patients (72%) were male. According to the RIFLE classification and the AKIN criteria, the incidence of AKI during first 48 h after receiving ECMO support was 81% and 85%, respectively. The overall mortality was 51% and the hospital mortality was much higher among patients who received renal replacement therapy (RRT) than in patients not receiving RRT (73% vs 32%, p=0.001). Either class-Failure for the RIFLE classification (odds ratio (OR)=12.6, 95% confidence interval (CI)=2.2-72.3, p=0.005) or the Stage 3 for the AKIN (OR=30.8, 95% CI=3.3-287.2, p=0.003) was found to be independently associated with the hospital mortality. The area under the receiver operator characteristic (ROC) curve for hospital mortality was 0.738 for the RIFLE classification (p=0.001) and was 0.799 for the AKIN criteria (p<0.001). No significant differences were found in both the incidence of AKI and the hospital mortality of AKI by using the RIFLE/AKIN criteria. CONCLUSIONS Acute kidney injury is a major complication and associated with high mortality in adult patients who received ECMO support after undergoing cardiac surgery. Both the RIFLE classification and the AKIN criteria have good short-term prognostic capability in these populations and either class-Failure for the RIFLE classification or the Stage 3 for the AKIN were found to be independently associated with the hospital mortality. However, it does not seem that the AKIN criteria have greater sensitivity and specificity, compared with the RIFLE classification in this study population.