Effect of intermediate/high versus low dose heparin on the thromboembolic and hemorrhagic risk of unvaccinated COVID-19 patients in the emergency department

Background: The optimal prophylactic dose of heparin in patients with coronavirus-associated disease 2019 (COVID-19) in the emergency department (ED) is debated. This study aimed to analyze different thromboprophylaxis approaches in unvaccinated COVID-19 patients admitted to ED without initial venous thromboembolism. Methods: Retrospectively, the effect of intermediate/high versus low dose heparin treatment was evaluated from December 2020 to July 2021 in a tertiary Academic Hospital in northeast Italy. The primary outcome comprised arterial or venous thromboembolism or all-cause death within 30 days. Secondary outcomes comprised each single primary outcome component or major hemorrhagic event. Cox regression was used to determine predictors of the primary outcome and propensity score weights to balance the effect of heparin treatment on all outcomes. Results: Data of 144 consecutive patients (age 70 ± 13, 33% females) were included in the study. High-dose prophylactic heparin was used in 69%, intermediate in 15%, and low in 17% of patients. The primary outcome occurred in 48 patients. Independent predictors of the primary outcome were COVID-19 severity (hazards ratio (HR) 1.96, 95% confidence interval (CI) 1.05-3.65, p = 0.035) and D-dimer levels (HR each log ng/dl 1.38, 95% CI 1.04-1.84, p = 0.026). Intermediate/high dose heparin did not affect the risk of the primary outcome compared with the low dose (weighted HR 1.39, 95% CI 0.75-2.56, p = 0.292). Intermediate/high heparin increased the risk of major hemorrhagic events (weighted HR 5.92, 95% CI 1.09-32, p = 0.039). Conclusions: In unvaccinated COVID-19 patients admitted to ED, prophylaxis with heparin at the intermediate/high dose did not reduce primary outcome compared with the low dose but increased the risk of major hemorrhagic events.