Morris AE, Stapleton RD, Rubenfeld GD, Hudson LD, Caldwell E, Steinberg KP
Chest. 2007;131:342-348.
Background
The association between body mass index (BMI) and outcomes in critically ill patients is unclear. Our objective was to determine the association between BMI and outcomes in a population-based cohort of patients with acute lung injury (ALI).
Methods.
In a prospective cohort study of all ICU patients in King County, Washington, with ALI in 1 year (1999 to 2000), 825 patients had a BMI recorded. Using multivariate analysis, patients in the abnormal BMI groups were compared to normal patients in the following areas: mortality, hospital length of stay (LOS), ICU LOS, duration of mechanical ventilation, and discharge disposition.
Results.
There was no mortality difference in any of the abnormal BMI groups compared to normal-weight patients. Severely obese patients had longer hospital LOS than normal-weight patients (mean increase, 10.5 days; 95% confidence interval [CI], 4.8 to 16.2 days; p < 0.001); this was accentuated when analysis was restricted to survivors (mean increase, 14.3 days; 95% CI, 7.1 to 21.6 days; p < 0.001). ICU LOS and duration of mechanical ventilation were also longer in the severely obese group when analysis was restricted to survivors (mean increase, 5.6 days; 95% CI, 1.3 to 9.8 days; p = 0.01; and mean increase, 4.1 days; 95% CI, 0.4 to 7.7 days, respectively; p = 0.03). Severely obese patients were more likely to be discharged to a rehabilitation or skilled nursing facility than to home.
Conclusion.
BMI is not associated with mortality in patients with ALI, but severe obesity is associated with increased morbidity and resource utilization in the hospital and after discharge.
Editor's Comment.
Obesity is recognized as an important cause for excess morbidity and mortality in the general population. The above study provides results somewhat contrary to this prevailing dogma and fails to define an increased mortality in critically ill, severely obese (BMI >40 kg/m2) patients. It does find a longer length of stay, both in the intensive care unit (ICU) and the overall hospitalization, and a higher likelihood of requiring posthospital rehabilitation, but no excess in mortality that might be attributed to obesity. Previous studies have provided conflicting data, and several variables need to be considered to explain the inconsistent results. Obesity may be too narrow a surrogate for the overall health status of patients, nutritional reserve may be an important consideration in patients with intensely catabolic critical illness, and obesity itself may influence the nature of care provided. Most directly, this may not only be reflected in the ventilatory tidal volume settings chosen but may also influence decisions in the ICU regarding the timing of interventions such as intubation, extubation, and tracheostomy. Severe obesity itself may also be the primary factor leading to posthospitalization skilled nursing facility care because of potential difficulties in providing adequate support in the home in such patients.
Overall, although the true risks posed by severe obesity cannot be completely defined by this article, this study does provide additional justification for continuing to provide aggressive care to the severely obese, critically ill patient because the results do not indicate an independent mortality risk secondary to obesity alone.
SK