Background: The Centers for Medicare and Medicaid (CMS) and Surviving Sepsis Campaign recommends patients with sepsis-induced hypoperfusion receive 30 mL/kg of crystalloid fluid within three hours (30by3). Recently, CMS released a modification of this recommendation allowing for fluid dosing based on ideal instead of actual body weight (IBW/ABW) for obese patients. This study aims to determine the effect of IBW vs. ABW fluid dosing on mortality for patients with severe sepsis or septic shock with respect to body mass index (BMI).
Methods: This was a single-center retrospective cohort study. Using ICD 9 and 10 codes in combination with Sepsis-2 criteria, 1,144 patient visits were included between January 1, 2014-May 30, 2017. We determined whether 30by3 based on IBW and ABW dosing affected mortality based on BMI overall, and specifically for underweight (BMI <18.5 kg/m2) and obese (BMI ≥30 kg/m2) patients. Logistic regression was used, and all models adjusted for mortality in emergency department sepsis score, age, sex, severe vs. septic shock, time to antibiotics, and history of end-stage renal disease and heart failure.
Results: Of the 1,144 visits, 119 (10.4%) were underweight and 330 (28.8%) were obese patients. Patients received 30by3 based on ABW dosing 79.0% (underweight) vs. 57.0% (normal/overweight) vs. 23.9% (obese) and IBW dosing 50.4% (underweight) vs. 56.8% (normal/overweight) vs. 47.3% (obese). Across the entire range of BMI, receiving 30by3 based on ABW improved mortality (OR 0.58, 95% CI 0.40-0.86), with no change improvement in mortality for IBW dosing (OR 0.81, 95% CI 0.56-1.18). Underweight patients receiving 30by3 based on ABW demonstrated improved mortality (OR 0.13, 95% CI 0.03-0.55) which loses significance when dosed by IBW dosing (OR 0.46, 95% CI 0.13-1.63). There is no change in mortality for obese patients receiving 30by3 for either ABW dosing (OR 0.51, 95% CI 0.20-1.28) or IBW dosing (OR 0.83, 95% CI 0.39-1.79).
Conclusion: The modification by CMS to allow for IBW vs. ABW dosing of crystalloid fluids does not impact mortality for obese patients with severe sepsis or septic shock. However, there was a survival benefit observed for ABW dosing of fluids when measured across all body types that is not found for IBW dosing. This effect seems to be driven by improved survival for ABW dosing in underweight patients relative to IBW dosing.