RIFLE: association with mortality and length of stay in critically ill acute kidney injury patients.

OBJECTIVE To correlate the RIFLE classification with mortality and length of stay both in the intensive care unit and hospital. METHODS A prospective, observational, longitudinal cohort study, approved by the Institution's Ethics Committee. Data were collected for all patients staying longer than 24 hours in the intensive care unit of Hospital Universitário Polydoro Ernani de São Thiago - Universidade Federal de Santa Catarina from September 2007 to March 2008, followed-up either until discharge or death. Patients were divided in two groups: with or without acute kidney injury. The acute kidney injury group was additionally divided according to the RIFLE and sub-divided according to the maximal score in Risk, Injury of Failure. Loss and End-stage classes were not included in the study. APACHE II and SOFA were also evaluated. The t Student and Chi-Square tests were used. A P<0.05 was considered statistically significant. RESULTS The sample included 129 patients, 52 (40.3%) with acute kidney injury according to RIFLE. Patients were more severely ill in this group, with higher APACHE and SOFA scores (P<0.05). Compared to the without kidney injury group, the kidney injury severity caused increased intensive care unity (Risk 25%; Injury 37.5%; Failure 62.5%) and in-hospital (Risk 50%; Injury 37.5%; Failure 62.5%) mortality, and longer intensive care unit stay (P<0.05). CONCLUSION The RIFLE system, according to the severity class, was a marker for risk of increased intensive care unit and in-hospital mortality, and longer intensive care unit stay. No relationship with in-hospital length of stay was found.