Continuous Renal Replacement Therapy and Mortality in Critically Ill Obese Adults

Importance: The outcomes of critically ill adults with obesity on continuous renal replacement therapy (CRRT) are poorly characterized. The impact of CRRT dose on these outcomes is uncertain.

Objectives: This study aimed to determine if obesity conferred a survival advantage for critically ill adults with acute kidney injury (AKI) on CRRT. Secondarily, we evaluated whether the dose of CRRT predicted mortality in this population.

Design setting and participants: A retrospective, observational cohort study performed at an academic medical center in Minnesota. The study population included critically ill adults with AKI managed with CRRT.

Main outcomes and measures: The primary outcome of 30-day mortality was compared between obese (body mass index [BMI] ≥ 30 kg/m²) and nonobese (BMI < 30 kg/m²) patients. Multivariable regression assessed was used to assess CRRT dose as a predictor of outcomes. An analysis included dose indexed according to actual body weight (ABW), adjusted body weight (AdjBW), or ideal body weight (IBW).

Results: Among 1033 included patients, the median (interquartile range) BMI was 26 kg/m² (23-28 kg/m²) in the nonobese group and 36 kg/m² (32-41 kg/m²) in the obese group. Mortality was similar between groups at 30 days (54% vs. 48%; p = 0.06) but lower in the obese group at 90 days (62% vs. 55%; p = 0.02). CRRT dose predicted an increase in mortality when indexed according to ABW or AdjBW (hazard ratio [HR], 1.2-1.16) but not IBW (HR, 1.04).

Conclusions and relevance: In critically ill adults with AKI requiring CRRT, short-term mortality appeared lower in obese patients compared with nonobese patients. Among weight calculations, IBW appears to be preferred to promote safe CRRT dosing in obese patients.