The furosemide stress test to predict renal function after continuous renal replacement therapy

We read with interest the recent article by Dr Chawla and colleagues showing that a furosemide stress test was able to predict the development of renal damage stage III according to the Acute Kidney Injury Network classification in critically ill patients [1]. In this study, 25 patients that subsequently developed acute kidney injury (AKI) had lower urine output 2 hours following administration of furosemide compared with 52 patients that did not develop AKI. Apart from predicting which patients will develop AKI based on the renal response to furosemide, this concept may possibly also be used to predict successful recovery of renal function after continuous renal replacement therapy (CRRT) in critically ill patients recovering from AKI. The current practice to discontinue CRRT mostly considers increases in urine output or a fall in serum creatinine while on a constant dose of continuous renal support. Observational studies have shown that the most significant predictor for successful termination of CRRT is indeed urinary production [2]. Urinary output >400 ml/day has an area under the receiver operator curve (AUROC) of 0.81, resulting in correct classification for 79% of the patients [3]. Not surprisingly, this predictive ability was negatively influenced by the use of diuretics; however, the renal response on diuretics by itself was not considered a potential predictor. Previously, we demonstrated that administration of furosemide compared with placebo after termination of CRRT did not improve renal function or shorten renal failure [4]. In our study, urinary production was measured over a 4-