RIFLE criteria for acute kidney injury are associated with hospital mortality in critically ill patients: a cohort analysis

Eric AJ Hoste¹^,2 , Gilles Clermont¹ , Alexander Kersten¹ , Ramesh Venkataraman¹ , Derek C Angus¹ , Dirk De Bacquer³ and John A Kellum¹

¹The Clinical Research, Investigation, and Systems Modeling of Acute Illness (CRISMA) Laboratory, Department of Critical Care Medicine, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA

²Intensive Care Unit, Ghent University Hospital, Gent, Belgium

³Department of Public Health, Ghent University, Gent, Belgium

author email corresponding author email

Critical Care 2006, 10:R73doi:10.1186/cc4915


Published:	12 May 2006

See related letter by Lopes et al., http://ccforum.com/content/11/1/401

Abstract

Introduction

The lack of a standard definition for acute kidney injury has resulted in a large variation in the reported incidence and associated mortality. RIFLE, a newly developed international consensus classification for acute kidney injury, defines three grades of severity – risk (class R), injury (class I) and failure (class F) – but has not yet been evaluated in a clinical series.

Methods

We performed a retrospective cohort study, in seven intensive care units in a single tertiary care academic center, on 5,383 patients admitted during a one year period (1 July 2000–30 June 2001).

Results

Acute kidney injury occurred in 67% of intensive care unit admissions, with maximum RIFLE class R, class I and class F in 12%, 27% and 28%, respectively. Of the 1,510 patients (28%) that reached a level of risk, 840 (56%) progressed. Patients with maximum RIFLE class R, class I and class F had hospital mortality rates of 8.8%, 11.4% and 26.3%, respectively, compared with 5.5% for patients without acute kidney injury. Additionally, acute kidney injury (hazard ratio, 1.7; 95% confidence interval, 1.28–2.13; P < 0.001) and maximum RIFLE class I (hazard ratio, 1.4; 95% confidence interval, 1.02–1.88; P = 0.037) and class F (hazard ratio, 2.7; 95% confidence interval, 2.03–3.55; P < 0.001) were associated with hospital mortality after adjusting for multiple covariates.

Conclusion

In this general intensive care unit population, acute kidney 'risk, injury, failure', as defined by the newly developed RIFLE classification, is associated with increased hospital mortality and resource use. Patients with RIFLE class R are indeed at high risk of progression to class I or class F. Patients with RIFLE class I or class F incur a significantly increased length of stay and an increased risk of inhospital mortality compared with those who do not progress past class R or those who never develop acute kidney injury, even after adjusting for baseline severity of illness, case mix, race, gender and age.