The Effect of Body Mass Index and Weight-Adjusted Fluid Dosing on Mortality in Sepsis.

PURPOSE: The Surviving Sepsis Campaign guidelines recommend 30 mL/kg of fluids within 3 hours (30by3) of sepsis-induced hypoperfusion, but a national mandate released an allowance for dosing based on ideal instead of actual body weight (IBW/ABW) for obese patients. This study aims to determine the dose-effect of 30by3 for patients with severe sepsis or septic shock (SS/SS) with respect to body mass index (BMI) categories and secondarily, examine the clinical impact of IBW vs. ABW-based dosing. METHODS: Retrospective cohort study of adults (≥18 years; n = 1,032) with SS/SS presenting to an urban, tertiary-care emergency department. Models include MEDS score, antibiotic timing, lactate, renal and heart failure, among others. RESULTS: The cohort was 10.2% underweight and 28.7% obese. Overall mortality was 17.1% with 20.4% shock mortality. An exponential increase in mortality was observed for each 5 mL/kg under 30by3 for underweight (p = 0.02), but not obese patients. ABW vs IBW-30by3 dosing was reached in 80.0 vs 52.4% (underweight), 56.4 vs 56.9% (normal/overweight), and 23.3 vs 46.0% (obese). Across all BMI categories, there was increased mortality for not reaching ABW-based 30by3 dosing (OR 1.78, 95% CI 1.18-2.69) with no significant impact for IBW (OR 1.28, 95% CI 0.87 -1.91). The increased mortality for failing to reach ABW-dosed 30by3 remained for underweight patients ABW (OR 5.82, 95% CI 1.32-25.57) but not obese patients. Longer ICU stays were observed for not reaching 30by3 based on ABW (β = 2.40, 95% CI 0.84-3.95) and IBW dosing (β = 1.58, 95% CI 0.07-3.08) overall. This effect remained for obese and underweight (except IBW dosing) patients. CONCLUSIONS: An exponential, dose-effect increase in mortality was observed for underweight patients not receiving 30by3. Therefore, the mortality impact of under-dosing may be amplified using ABW for underweight patients. Fluid dosing did not impact mortality for obese patients, but we caution against deviation from guidelines without further studies.

Duke Scholars

Author John David Purakal Emergency Medicine