Adjusted Versus Total Body Weight Dosing for Intravenous Heparin Infusions and Target Attainment in Obese Patients

Background: Intravenous unfractionated heparin is commonly used to treat venous thromboembolism; however, dosing in obese patients is challenging due to unpredictable pharmacokinetics and conflicting guidance. Methods: This single center, retrospective cohort study was conducted to evaluate the achievement of therapeutic heparin correlation values (HCV), a standardized version of the activated partial thromboplastin time (aPTT), with heparin infusions dosed utilizing total body weight (TBW) versus adjusted body weight (ABW) in obese patients. The primary outcome was to determine the percentage of initial HCV within the therapeutic range after heparin initiation. Key secondary outcomes included incidence of supratherapeutic HCV at any time and major bleeding events. Results: A total of 477 patients were included, with 94.9% (n = 453) of patients in the TBW cohort (mean body mass index (BMI) 36.8 ± 7.4 kg/m²) and 5.1% (n = 24) in the ABW cohort (mean BMI 42.1 ± 9.3 kg/m²). Initial HCV was within the therapeutic range in 41.9% (n = 190) and 54.2% (n = 13) of patients in the TBW cohort and ABW cohort, respectively (P = .238). Supratherapeutic HCV during any point in therapy occurred in 64.7% (n = 293) of the TBW cohort and 41.7% (n = 10) of the ABW cohort (P = .022). Major bleeding occurred in 15.2% (n = 69) of patients in the TBW cohort and 12.5% (n = 3) in the ABW cohort (P = .716). Conclusions: In obese patients receiving a heparin infusion, dosing based on ABW compared to TBW did not result in a higher likelihood of achieving a therapeutic initial HCV, but the rate of supratherapeutic HCV was reduced.