The effect of body mass index on patient outcomes in a medical ICU

Study objectives: To examine the effect of patient body mass index (BMI) on outcome in intensive care. Design: In a prospective study, the patients were classified into groups based on the calculated BMI, as follows: BMI < 19.0 (n = 350), : 19.0 and < 25.0 (n = 663), >= 25.0 and < 29.9 (n = 585), >= 30.0 and < 40.0 (n = 396), and >= 40.0 (n = 154). Groups were compared by age, APACHE (acute physiology and chronic health evaluation) 11 score, mortality, ICU length of stay (LOS), hospital LOS, number receiving ventilation, and ventilator-days. Adverse events including nosocomial pneumonia, ventilator-days per patient, failed extubations, and line-related complications were recorded. Setting: The study was conducted in a 9-bed medical ICU of a 650-bed tertiary care hospital. Measurements: Height and weight were prospectively recorded for the first ICU admission during a hospital stay. Results: Between January 1, 1997, and August 1, 2001, 2,148 of 2,806 patients admitted to the ICU had height and weight recorded. There were no differences in APACHE 11 score, mortality, ICU LOS, hospital LOS, number receiving ventilation, ventilator-days, average total cost, or average variable cost among the five groups. However, the severely obese patients were more frequently female and younger than those who were overweight and obese (p < 0.001). Adverse events were infrequent, but there were no differences between the obese/very obese compared with others. Conclusion: BMI has minimal effects on ICU outcome after patients are admitted to a critical care unit.