Title: Evaluation of heparin dosing in obesity for treatment of deep vein thrombosis and pulmonary embolism.
Authors: Elise Paskowski, PharmD; Brandon Snyder, PharmD, BCPS
Acknowledgments: Aundrea Rosenberger, PharmD, BCIDP; Theodore Bell, MS
Objective: This study aims to look at the safety of using actual body weight in our deep vein thrombosis (DVT) and pulmonary embolism (PE) heparin protocol by comparing supratherapeutic aPTT values in obese and non-obese populations.
Background: Obesity rates in the United States are rising, yet venous thromboembolism (VTE) guidelines lack dosing strategies for obese patients. Research has shown mixed results, supporting the use of actual bodyweight or adjusted bodyweight in obese patients.
Methods: A retrospective chart review was conducted from May 1, 2024, to September 1, 2025, on patients who were ordered the heparin DVT/PE order set. Inclusion criteria were age ≥18, one aPTT drawn 5–7 hours after heparin initiation, and dosing based on actual body weight with no prespecified cap. Exclusion criteria included pregnancy, prior heparin use, no bolus given, protocol ordered but not administered, non-protocol aPTT goals, incorrect timing, or use of non-actual body weight. Currently at WellSpan Ephrata Community Hospital, patients receive an 80 unit/kg bolus dose followed by 18 unit/kg/hr based on actual body weight. Average aPTT values were compared between obese (BMI ≥ 30kg/m2) and non-obese patients. The primary outcome is a comparison of the average first aPTT values in the obese vs non-obese populations. The secondary outcome is the incidence of major bleeding events.
Results: Mean aPTT values were compared between obese and non-obese populations. For the primary outcome, the mean aPTT in the non-obese group was 79.4 seconds. The mean aPTT in the obese group was 105.19 seconds. The institutional therapeutic range for aPTT values is 45-70 seconds. Major bleeding events occurred in eight patients from the non-obese group and one patient from the obese group. Major bleeding events were defined as bleeding that led to a drop in hemoglobin of greater than or equal to 2, a drop in hemoglobin requiring a transfusion or a bleed in a critical site like the cerebrum or abdominal area. A demographic comparison was completed between groups.
Conclusions: Supratherapeutic aPTT values are a nursing-driven protocol. Using adjusted body weight in obese patients reduces mean aPTT and nursing workload. Elevated aPTT values put both populations at risk for major bleeds. These findings support using adjusted body weight in obese patients. Limitations to this study include being a single-center retrospective chart review with a small sample size, evaluating one indication at a single time point.
Self-assessment question: What are some benefits to using adjusted bodyweight in obese patients shown by this study? (Choose all that apply)
A. Decreased bleeding events
B. Decreased nurse workload
C. Decreased mean aPTT value
D. Increased bleeding events
References: - Pennsylvania department of health. Obesity. Commonwealth of Pennsylvania. https://www.pa.gov/agencies/health/diseases-conditions/chronic-disease/obesity. 2025. Accessed on August 3, 2025.
- Gerlach AT, Folino J, Morris BN, Murphy CV, Stawicki SP, Cook CH. Comparison of heparin dosing based on actual body weight in non-obese, obese and morbidly obese critically ill patients. Int J Crit Illn Inj Sci. 2013;3(3):195-199. doi:10.4103/2229-5151.119200
- J. Hirsh, S. S. Anand, J. L. Halperin, & V. Fuster. Circulation. Guide to Anticoagulant Therapy: Heparin: A Statement for Healthcare Professionals From the American Heart Association. AHA/ASA Journals. https://www.ahajournals.org/doi/10.1161/01.cir.103.24.2994. June 19, 2001. Accessed August 3, 2025.
- Fan J, John B, Tesdal E. Evaluation of heparin dosing based on adjusted body weight in obese patients. Am J Health Syst Pharm. 2016;73(19):1512-1522. doi:10.2146/ajhp150388
- M. Safani, S. E. Hill, R. Winters, S. Kawanishi, S. W. Eppstein, S. Min, & M. Drachenberg. CHEST journal. The Use of Average Body Weight in Dosing Unfractionated Heparin. https://journal.chestnet.org/article/S0012-3692(13)60435-3/fulltext#:~:text=recommend%20the%20use%20of%20weight,)%20of%200.07%20L/kg. June 2013. Accessed August 3, 2025.
- Nguyen K, Murray B, Campbell-Bright S, et al. Adjusted Versus Total Body Weight Dosing for Intravenous Heparin Infusions and Target Attainment in Obese Patients. Hosp Pharm. Published online June 29, 2025. doi:10.1177/00185787251348377
