Clinical Science Articles Survival by Dialysis Modality in Critically Ill Patients with Acute Kidney Injury Kerry C. Cho,* Jonathan Himmelfarb, † Emil Paganini, ‡ T. Alp Ikizler, § Sharon H. Soroko,  Ravindra L. Mehta,  and Glenn M. Chertow* *Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California; † Division of Nephrology, Department of Medicine, Maine Medical Center, Portland, Maine; ‡ Division of Nephrology, Department of Medicine, Cleveland Clinic Foundation, Cleveland, Ohio; § Division of Nephrology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and  Division of Nephrology, Department of Medicine, University of California San Diego, San Diego, California Among critically ill patients, acute kidney injury (AKI) requiring dialysis is associated with mortality rates generally in excess of 50%. Continuous renal replacement therapies (CRRT) often are recommended and widely used, although data to support its superiority over intermittent hemodialysis (IHD) are lacking. Data from the Program to Improve Care in Acute Renal Disease (PICARD), a multicenter observational study of AKI, were analyzed. Among 398 patients who required dialysis, the risk for death within 60 d was examined by assigned initial dialysis modality (CRRT [n  206] versus IHD [n  192]) using standard Kaplan-Meier product limit estimates, proportional hazards (“Cox”) regression methods, and a propensity score approach to account for selection effects. Crude survival rates were lower for patients who were treated with CRRT than IHD (survival at 30 d 45 versus 58%; P  0.006). Adjusted for age, hepatic failure, sepsis, thrombocytopenia, blood urea nitrogen, and serum creatinine and stratified by site, the relative risk for death associated with CRRT was 1.82 (95% confidence interval 1.26 to 2.62). Further adjustment for the propensity score did not materially alter the association (relative risk 1.92; 95% confidence interval 1.28 to 2.89). Among critically ill patients with AKI, CRRT was associated with increased mortality. Although the results could reflect residual confounding by severity of illness, these data provide no evidence for a survival benefit afforded by CRRT. Larger, prospective, randomized clinical trials to compare CRRT and IHD in severe AKI are needed. J Am Soc Nephrol 17: 3132–3138, 2006. doi: 10.1681/ASN.2006030268 A cute kidney injury (AKI) frequently complicates crit- ical illness and is associated with considerable mor- tality and morbidity. When severe enough to require dialysis, mortality rates in excess of 50% have been reported in most studies (1– 4). Since its introduction in the late 1970s (5), continuous renal replacement therapy (CRRT), including he- mofiltration and hemodiafiltration, has gained widespread ac- ceptance in the treatment of dialysis-requiring AKI (6 –10). Sev- eral clinical trials have demonstrated beneficial effects of CRRT over intermittent hemodialysis (IHD) on hemodynamic stabil- ity, solute clearance, and ultrafiltration capacity (11–16). Direct comparisons of CRRT and IHD using observational data are problematic, because patients who are hemodynamically un- stable are more likely to be treated with CRRT. Attempts to account for underlying severity of illness and comorbidity have yielded disparate conclusions (17,18). Results from underpow This controlled study by Cho and colleagues on the benefits of continuous versus intermittent dialysis in treating acute kidney injury relates to a Mini-Review by Van Biesen et al. in this month’s issue of CJASN (pp. 1314 –1319) that discusses how acute kidney injury is currently defined and the use of the RIFLE criteria. ered randomized clinical trials of CRRT and IHD have been limited and equivocal (19 –21). In this study, we analyzed the subcohort of patients from the Program to Improve Care in Acute Kidney Disease (PICARD) who required dialysis (n = 398), evaluating clinical character- istics and outcomes that were associated with the initial as- signed dialysis modality (CRRT versus IHD). We hypothesized that unadjusted results would show a survival advantage to IHD and that results adjusted for confounding and selection effects would show no significant difference between assigned modality groups. Materials and Methods Study Participants The PICARD network is composed of five academic medical centers in the United States: University of California San Diego (Coordinating Center), Cleveland Clinic Foundation (CCF), Maine Medical Center, Vanderbilt University, and University of California San Francisco. Dur- ing a 31-mo period (February 1999 to August 2001), all patients who Received March 24, 2006. Accepted August 21, 2006. Published online ahead of print. Publication date available at www.jasn.org. Address correspondence to: Dr. Glenn M. Chertow, University of California San Francisco, Department of Medicine Research, UCSF Laurel Heights Suite 430, 3333 California Street, San Francisco, CA 94118. Phone: 415-476-2173; Fax: 415- 476-1700; E-mail: chertowg@medicine.ucsf.edu Copyright © 2006 by the American Society of Nephrology ISSN: 1046-6673/1711-3132