Body Mass Index (BMI) Does Not Affect Survival and Length of Stay (LOS) in Septic Shock Patients

Abstract

Purpose: 65.7% of US adults age 20 years and older are overweight (BMI 25-30) and 30.6% are obese (BMI >30). These statistics are reflected in the ICU patient population. We studied the effect of BMI on survival and LOS in patient with septic shock. Methods: Subjects were patients from the ICU Project Impact Database admitted to Cooper University Hospital ICU in septic shock over a three year period from 2008-2011. A total number of 293 patients were evaluated and separated based on whether they survived or not. Variables analyzed “BMI, length of stay, and others thought to play a role in mortality septic shock lactate, chronic kidney disease (CKD), cirrhosis”. BMI was classified into four groups: underweight (<18); normal (18-24.9); overweight (25-29.9) and obese (>30). Univariate analysis was used to compare the two groups (alive or deceased) for any significant differences. Subsequently, each of the variables found to be significantly different [p<0.05] were then analyzed using multivariate analysis to evaluate whether any were independent predictors of mortality in patients with septic shock. Results: When comparing mortality in septic shock patients with normal BMI (40%) using univariate analysis there was a trend for a decreased mortality in underweight (30.8%; p=0.526) and obese patients (35.6%; p=0.561) although not statistically significant. When evaluating median LOS in patients among all BMI classifications there was no significant difference in median ICU LOS or hospital LOS. Variables found to be statistically significant in relation to mortality were patients with CKD (Deceased 25% vs. Alive 15%) [p= 0.05], Multiple Organ Dysfunction (MOD) >2 (Deceased 87% vs. Alive 76.2%) [p=0.03] and elevated lactate on admission (Deceased 3.5 vs. Alive 2.7) [p=0.05]. Age, APACHE II, and cirrhosis were also found to be significant. When looking at differences in percent mortality using multivariate analysis, only age (Deceased 66.03 vs. Alive 58.49) [p=0.00], APACHE II (Deceased 23.95 vs. Alive 17.49) [p=0.00] and presence of cirrhosis (Deceased 9.4% vs. Alive 0.7%) [p=0.03] were found to be independent predictors of mortality in Septic shock patients. Conclusion: There was a trend for a protective effect on mortality in septic shock patients who were underweight BMI although this trend was not statistically significant. There was no significant difference among the BMI groups in relation to ICU or hospital LOS. The study was sufficiently powered to detect a difference between BMI groups suggested by the finding of significant independent predictors for mortality in septic shock with age, APACHE score, and presence of cirrhosis all of which had previously been reported.Table: No Caption available.Table 2: . No Caption available.