Background: Venous thromboembolism (VTE) is treated based on body weight to determine unfractionated heparin (UFH) dosage. However, this approach has not been thoroughly studied in obese patients. We aimed to determine the optimal infusion rate of UFH in obese patients using the weight-based dosing nomogram.
Methods: A retrospective review was conducted on adult patients treated with heparin per VTE protocol with activated thromboplastin time (aPTT) of 60-80 seconds. We calculated the median heparin infusion rate (units/kg/hour) required to achieve the first therapeutic aPTT in obese and non-obese patients. We also investigated the median time required to achieve the first therapeutic aPTT in both groups, the percentage of aPTT at the target goal within the first 24 hours of treatment, the percentage of sub and supra-therapeutic aPTT at 24 hours after initiation of heparin infusion, and incidence of thrombosis and bleeding during heparin treatment.
Results: We included 70 patients with confirmed VTE diagnosis. Obese patients required a lower UFH infusion rate (units/kg/hour) compared to non-obese patients (16.5 vs. 18, p = 0.24). The time to reach the first therapeutic aPTT was longer in obese patients compared to non-obese (17.7 hours vs. 15 hours respectively, p = 0.7). Major bleeding events were higher in the obese patients compared to the non-obese (6.25% vs. 2.6%, p = 0.44). In contrast, minor bleeding events were higher in the non-obese group (28.1% vs. 36.8%, p = 0.46). The overall rate of thrombotic events occurring during heparin treatment was 6.2% in obese patients and 5.3% in non-obese patients (p = 0.86).
Conclusion: Dosing of UFH in obese patients using the weight-based nomogram was associated with over-anticoagulation and demonstrated no significant difference in UFH dosing to reach the goal of aPTT in obese or non-obese patients.
Key words: Venous thromboembolism, unfractionated heparin, obesity, retrospective
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