A Tale of Two Centers: Is Low-Molecular-Weight Heparin Really Superior for Prevention of Post-Traumatic Venous Thromboembolism?

BACKGROUND Low-molecular-weight heparin (LMWH) is widely used for venous thromboembolism (VTE) chemoprophylaxis following injury. However, unfractionated heparin (UFH) is a less expensive option. We compared LMWH and UFH for prevention of post-traumatic deep venous thrombosis (DVT) and pulmonary embolism (PE). METHODS Trauma patients aged 15 years and older with at least one administration of VTE chemoprophylaxis at two Level I trauma centers with similar DVT-screening protocols were identified. Center 1 administered UFH every eight hours for chemoprophylaxis and Center 2 used twice-daily anti-factor Xa-adjusted LMWH. Clinical characteristics and primary chemoprophylaxis agent were evaluated in a two-level logistic regression model. Primary outcome was incidence of DVT and PE. RESULTS There were 3,654 patients: 1,155 at Center 1 and 2,499 at Center 2. The unadjusted DVT rate at Center 1 was lower than at Center 2 (3.5% vs. 5.0%; p=0.04); PE rates did not significantly differ (0.4% vs. 0.6%; p=0.64). Patients at Center 2 were older (mean 50.3 vs. 47.3 years, p<0.001) and had higher Injury Severity Scores (median 10 vs. 9, p<0.001), longer stays in the hospital (mean 9.4 vs. 7.0 days, p<0.001) and intensive care unit (mean 3.0 vs. 1.3 days, p<0.001), and a higher mortality rate (1.6% vs. 0.6%, p=0.02) than patients at Center 1. Center 1's patients received their first dose of chemoprophylaxis earlier than patients at Center 2 (median 1.0 vs. 1.7 days, p<0.001). After risk adjustment and accounting for center effects, primary chemoprophylaxis agent was not associated with risk of DVT (odds ratio, 1.01; 95% confidence interval, 0.69-1.48; p=0.949). Cost calculations showed UFH was less expensive than LMWH. CONCLUSIONS Primary utilization of UFH is not inferior to LMWH for post-traumatic DVT chemoprophylaxis and rates of PE are similar. Given UFH is lower in cost, the choice of this chemoprophylaxis agent may have major economic implications. LEVEL OF EVIDENCE Level II. Prognostic and Epidemiological.