(1005) Evaluating the Impact of Body Mass Index on Unfractionated Heparin Dosing in Critically Ill Patients

Introduction: Unfractionated heparin (UFH) is often the primary anticoagulant in the intensive care unit (ICU), however uncertainty exists regarding the optimal dosing weight in patients with obesity. The purpose of this study was to evaluate the appropriateness of an UFH protocol dosed by adjusted body weight (AdjBW) in critically ill patients.

Methods: This was a retrospective cohort study of adult patients initiated on an UFH protocol in critically ill patients between May 2022 and September 2023. Patients were excluded if they had an Impella® device or received UFH for < 24 hours (h). Patients were dosed by AdjBW regardless of body mass index (BMI). Patients were divided into three cohorts: non-obese (BMI < 30 kg/m2), obese (30-39.9 kg/m2), severely obese (≥40 kg/m2). Statistical analysis was conducted using the Kruskal-Wallis test for continuous variables and the Fisher’s exact or chi-squared tests for categorical variables. The primary objective was to compare the median time to therapeutic UFH level (anti-Xa or aPTT) in critically ill non-obese, obese, and severely obese patients. UFH levels were collected for 7 days after initiation or until discontinuation. Patients who did not reach a therapeutic level were excluded from the primary outcome. Secondary objectives included mean infusion rate at first therapeutic UFH level and mean percent of therapeutic, subtherapeutic, and supratherapeutic levels.

Results: A total of 136 patients were included: non-obese (n=50), obese (n=50), severely obese (n=36). The majority (89.7%, n=122) achieved a therapeutic level. Fewer patients in the non-obese group achieved a therapeutic UFH level compared to the obese or severely obese groups (80%, 94%, 97.2%; p=0.016). Mean infusion rates (units/kg/h) at the first therapeutic UFH level were similar across groups (14.8 vs. 15.2 vs. 14.8, p=0.716). No difference was found in median time to first therapeutic UFH level between the non-obese, obese, and severely obese groups (14.8 h, 11.8 h, 16.9 h; p=0.628). There was no difference in the mean percent of therapeutic (44.9%, 47.9%, 53.9%; p=0.547) or subtherapeutic (49.5% vs. 43.1% vs. 39.3%; p=0.400) UFH levels across the cohorts.

Conclusions: Critically ill patients on an UFH protocol dosed with AdjBW achieved therapeutic UFH levels in similar times across weight cohorts.