Obesity and Site-specific Nosocomial Infection Risk in the Intensive Care Unit

Background: Obese patients are at higher than normal risk for postoperative infections such as pneumonia and surgical site infections, but the relation between obesity and infections acquired in the intensive care unit (ICU) is unclear. Our objective was to describe the relation between body mass index (BMI) and site-specific ICU-acquired infection risk in adults.

Methods: Secondary analysis of a large, dual-institutional, prospective observational study of critically ill and injured surgical patients remaining in the ICU for at least 48 h. Patients were classified into BMI groups according to the National Heart, Lung and Blood Institute guidelines: <or= 18.5 kg/m(2) (underweight), 18.5-24.9 kg/m(2) (normal), 25-29.9 kg/m(2) (overweight), 30.0-39.9 kg/m(2) (obese), and >or= 40.0 kg/m(2) (severely obese). The primary outcomes were the number and site of ICU-acquired U.S. Centers for Disease Control and Prevention-defined infections. Multivariable logistic and Poisson regression were used to determine age-, sex-, and severity-adjusted odds ratios (ORs) and incidence rate ratios associated with differences in BMI.

Results: A total of 2,037 patients had 1,436 infection episodes involving 1,538 sites in a median ICU length of stay of 9 days. After adjusting for age, sex, and illness severity, severe obesity was an independent risk factor for catheter-related (OR 2.2; 95% confidence interval [CI] 1.5, 3.4) and other blood stream infections (OR 3.2; 95% CI 1.9, 5.3). Cultured organisms did not differ by BMI group.

Conclusion: Obesity is an independent risk factor for ICU-acquired catheter and blood stream infections. This observation may be explained by the relative difficulty in obtaining venous access in these patients and the reluctance of providers to discontinue established venous catheters in the setting of infection signs or symptoms.