Anticoagulation stewardship quality improvement project to decrease incidence of supratherapeutic activated partial thromboplastic time in overweight cancer patients on unfractionated heparin infusions

Unfractionated Heparin (UFH) is widely used to treat multiple conditions in hospitalized patients. Standard dosing based on actual body weight (ABW) may lead to over-anticoagulation in overweight patients due to the limited vascularity of adipose tissue. Historically, ABW was used when BMI ≤ 40 kg/m 2 , and adjusted body weight (AdjBW) when BMI > 40 kg/m 2 . However, patients with ABW >130% of ideal body weight (IBW) and BMI ≤ 40 kg/m 2 experienced increased rates of supratherapeutic activated partial thromboplastin times (aPTTs). The objective of this project was to evaluate whether use of AdjBW for initial UFH dosing reduces supratherapeutic aPTTs in cancer patients with ABW >130% of IBW and BMI ≤ 40 kg/m 2 . A new high intensity UFH protocol utilizing AdjBW UFH dosing was implemented on July 9, 2024. This single-center quality improvement study compared the pre- and post-intervention aPTTs in hospitalized cancer patients. In the bolus/transition cohort the percentage of first supratherapeutic aPTTs decreased by 37% (RR 0.63; 95% CI: [0.46–0.86], p = 0.004 and the percentage of first therapeutic aPTTs increased by 82.1% (RR 1.82; 95% CI: [1.12–2.97], p = 0.03. In the no bolus cohort, the percentage of first supratherapeutic aPTTs decreased by 39.2% (RR 0.61; 95% CI 0.38–0.97, p = 0.04). Time to therapeutic aPTT was shorter in the post-implementation arm compared to pre-implementation. In conclusion, AdjBW-based UFH dosing significantly reduced the percentage of first supratherapeutic aPTTs and decreased the time to first therapeutic aPTT in obese cancer patients on the high-intensity UFH protocol.