Risk factors of early redialysis after weaning from postoperative acute renal replacement therapy

Objective: The aim of this study was to identify risk factors for redialysis in postoperative patients with acute renal failure (ARF) who had previously been weaned from acute dialysis. Although recovery of renal function is anticipated in patients with ARF, no data have been reported on successful weaning from acute dialysis. Design and setting: Retrospective observational case-control study in a 64-bed surgical ICU. Patients and methods: Success in discontinuing dialysis was defined as cessation from dialysis for at least 30days. A total of 304 postoperative patients who underwent acute renal replacement therapy in a surgical ICU between July 2002 and April 2005 were included. SOFA score biochemical data and renal function parameters were assessed on the day after the last session of renal replacement therapy, designated as day 0 (D0). Results: We could wean 94 patients (30.9%) from acute dialysis for more than 5 days, and 64 of these (21.1%) were successfully weaned for at least 30 days. The independent predictors for resuming dialysis within 30 days were: (a) longer duration of dialysis (OR 1.06), (b) higher SOFA score on D0 (OR 1.44), (c) oliguria (urine output < 100cc/8 h; OR 4.17) on D1, and (d) age over 65years (OR 6.35). The area under the ROC curve was 0.880. Two-way analysis of variance with repeated measurements over time showed a larger decline in SOFA score and an increase in urine output in patients with successful cessation of dialysis. Kaplan-Meier analysis showed a significant difference in early resumption of dialysis between patients with or without oliguria at D0. Conclusion: More than two-thirds of patients weaned from postoperative acute dialysis for more than 5 days were free of dialysis for at least 30days. Less urine output, longer duration of dialysis, age over 65years, and higher disease severity score are predictive of a patient's redialysis after initial weaning from acute dialysis.