Urine neutrophil gelatinase-associated lipocalin and urine output as predictors of the successful discontinuation of continuous renal replacement therapy in critically ill patients with acute kidney injury

Abstract

Background: Continuous renal replacement therapy (CCRT) is a frequently used modality for the support of intensive care patients with acute kidney failure (AKI). Nevertheless, there are no objective criteria for the discontinuation of CRRT. The purpose of this study was to investigate whether urine neutrophil gelatinase-associated lipocalin (uNGAL) alone or in combination with urine output could be used as a diagnostic test for renal function recovery in ICU patients on CRRT.Methods: This was a single-centre prospective observational study including patients with acute kidney failure needing CRRT. Sixty-nine patients were enrolled, and 54 completed the study. Of the 54 patients, 22 recovered renal function (REC), defined as dialysis independency at 72 hours from discontinuation, while 32 patients did not (NREC). Urine NGAL was measured at 0, 6, 12, and 24 hours after CRRT discontinuation. The cumulated urine output was measured for 24 hours prior to discontinuation and at 6, 12, and 24 hours after discontinuation. Logistic regression was used to calculate the missing 6-hour uNGAL values by interpolation. The Youden index was used to calculate cut-off values. A P-value <0.05 was considered statistically significant.Results: Baseline characteristics at CRRT initiation were similar between groups. Compared to the NREC group, REC patients had significantly higher urine output (p<0.0001) and lower uNGAL (p<0.001) at all time points, except for uNGAL at 24 hours (p<0.24). The best single predictor for renal recovery was the cumulated urine output 24 hours after discontinuation (predictive value 83%). Combining uNGAL at 6 hours (cut-off 1650 µg/L) with the cumulated urine output during the 24 hours prior to discontinuation (cut-off 210 ml) proved superior, with predictive values of 92% (CRRT dependency) and 93% (renal function recovery).Conclusions: With predictive values up to 93%, the combination of uNGAL at 6 hours and the cumulatated urine output during the 24 hours prior to CRRT cessation proved to be the best diagnostic test for renal function recovery in ICU patients.Clinical trial registration: N/A