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Body mass index and acute kidney injury in the acute respiratory distress syndrome

Soto, Graciela J. MD, MS; Frank, Angela J. MD; Christiani, David C. MD, MPH; Gong, Michelle Ng MD, MS

doi: 10.1097/CCM.0b013e3182591ed9
Clinical Investigations

Objectives: Obesity is increasingly encountered in intensive care units but the relationship between obesity and acute kidney injury is unclear. We aimed to evaluate whether body mass index was associated with acute kidney injury in the acute respiratory distress syndrome and to examine the association between acute kidney injury and mortality in patients with and without obesity.

Design: Retrospective study.

Setting: Massachusetts General Hospital and Beth Israel Deaconess Medical Center.

Patients: Seven hundred fifty-one patients with acute respiratory distress syndrome.

Interventions: None.

Measurements and Main Results: Acute kidney injury was defined as meeting the “Risk” category according to modified Risk, Injury, Failure, Loss, End-stage criteria based on creatinine and glomerular filtration rate because urine output was only available on the day of intensive care unit admission. Body mass index was calculated from height and weight at intensive care unit admission. The prevalence of acute kidney injury increased significantly with increasing weight (p = .01). The odds of acute kidney injury were twice in obese and severely obese patients compared to patients with normal body mass index, after adjusting for predictors of acute kidney injury (age, diabetes, Acute Physiology and Chronic Health Evaluation III, aspiration, vasopressor use, and thrombocytopenia [platelets ≤ 80,000/mm3]). After adjusting for the same predictors, body mass index was significantly associated with acute kidney injury (odds ratioadj 1.20 per 5 kg/m2 increase in body mass index, 95% confidence interval 1.07–1.33). On multivariate analysis, acute kidney injury was associated with increased acute respiratory distress syndrome mortality (odds ratioadj 2.76, 95% confidence interval 1.72–4.42) whereas body mass index was associated with decreased mortality (odds ratioadj 0.81 per 5 kg/m2 increase in body mass index, 95% confidence interval 0.71–0.93) after adjusting for mortality predictors.

Conclusions: In acute respiratory distress syndrome patients, obesity is associated with increased development of acute kidney injury, which is not completely explained by severity of illness or shock. Although increased body mass index is associated with decreased mortality, acute kidney injury remained associated with higher mortality even after adjusting for body mass index.

From the Division of Critical Care Medicine (GJS, MNG), Department of Medicine, Jay B. Langner Critical Care Service, Department of Medicine, Montefiore Medical Center, Bronx, NY; Environmental Health Department (DCC), Environmental and Occupational Medicine and Epidemiology Program, Harvard School of Public Health, Boston, MA; Pulmonary and Critical Care Unit (AJF, DCC), Department of Medicine, Massachusetts General Hospital, Boston, MA; Department of Epidemiology and Population Health (MNG), Albert Einstein College of Medicine, Bronx, NY.

Supported, in part, by research grants R01 HL 84060, R01 HL 86667, and R01 HL 60710 from the National Heart, Lung, and Blood Institute (Massachusetts General Hospital, Boston, MA); and by the Clinical and Translational Science Awards Grant UL1 RR025750, KL2 RR025749, and TL1 RR025748 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH), and NIH roadmap for Medical Research. Its contents are solely the responsibility of the authors and do not necessary represent the official view of the NCRR or NIH (Albert Einstein College of Medicine, Bronx, NY).

The authors have not disclosed any potential conflicts of interest.

Address request for reprints to: Graciela J. Soto, MD, MS, Division of Critical Care Medicine, Jay B. Langner Critical Care Service, Department of Medicine, Montefiore Medical Center, 111 East 210th Street, Bronx, NY 10467. E-mail: gsoto@montefiore.org

© 2012 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins