RIFLE classification in patients with acute kidney injury in need of renal replacement therapy

Objectives: To evaluate the association of RIFLE classification with the outcomes of critically ill patients with acute kidney injury (AKI) who require renal replacement therapy (RRT). Design and setting: Prospective cohort study in the medical-surgical ICUs at three tertiary hospitals. Patients: 214 patients over 1 year (mean age 71.4 +/- 15.8 years). Continuous RRT was used in 179 (84%); patients were classified as risk (25%), injury (27%), or failure (48%). Overall mortality was 76%. Patients: There were no significant differences according to RIFLE classification (risk 72%, injury 79%, failure 76%). Variables selected in multivariate analysis were: older age (OR 1.03, 95% CI 1.01-1.06), presence of comorbidity (3.15, 1.10-9.02), poor chronic health status (6.51, 1.95-21.71), number of associated organ dysfunctions (patients with one or two organ dysfunctions 5.93, 2.03-17.33; patients with three or more organ dysfunctions 26.76, 6.28-114.11), and start of RRT after the first day of ICU (2.46, 1.09-5.53). RIFLE classification was forced into the model and was not selected. However, a subgroup analysis of 150 patients who received mechanical ventilation and vasopressors found failure to be associated with increased mortality (3.58, 1.08-11.80). Conclusion: Older age, number of organ dysfunctions, presence of comorbidities, and reduced functional capacity were the main prognostic factors. Patients who required RRT after the first day of ICU had a worse outcome. The RIFLE classification did not discriminate the prognosis in patients with AKI in need for RRT.