Efficacy and safety of two heparin regimens for prevention of venous thromboembolism in hospitalized patients with COVID-19: a meta-analysis

Intern Emerg Med. 2023 Apr;18(3):863-877. doi: 10.1007/s11739-022-03159-7. Epub 2022 Dec 29.


Venous thromboembolism (VTE) is common in patients with coronavirus disease-2019 (COVID-19). The optimal heparin regimen remains unknown and should balance thromboembolic and bleeding risks. The aim of this study was to evaluate the efficacy and safety of standard or higher heparin regimens for the prevention of VTE in patients hospitalized due to COVID-19. We performed a systematic literature search; studies reporting on hospitalized patients with COVID-19 who received standard heparin prophylaxis vs. high (intermediate or therapeutic) heparin regimens were included if outcome events were reported by treatment group and more than 10 patients were included. Primary study outcome was in-hospital VTE. Secondary study outcomes were major bleeding (MB), all-cause death, fatal bleeding and fatal pulmonary embolism. Overall, 33 studies (11,387 patients) were included. Venous thromboembolic events occurred in 5.2% and in 8.2% of patients who received heparin prophylaxis with at high-dose or standard-dose, respectively (RR 0.71, 95% CI 0.55-0.90, I2 48.8%). MB was significantly higher in patients who received high- compared to the standard-dose (4.2% vs 2.2%, RR 1.94, 95% CI 1.47-2.56, I2 18.1%). Sub-analyses showed a slight benefit associated with high-dose heparin in patients admitted to non-intensive care unit (ICU) but not in those to ICU. No significant differences were observed for mortality outcomes. Heparin prophylaxis at high-dose reduces the risk of VTE, but increased the risk of MB compared to the standard-dose. No clinical benefit for heparin high-dose was observed for ICU setting, but its role in the non-ICU deserves further evaluation. PROSPERO registration number: CRD42021252550.

Keywords: Anticoagulants; COVID-19; Embolism and thrombosis; Major bleeding; Meta-analysis.

Publication types

  • Systematic Review
  • Meta-Analysis

MeSH terms

  • Anticoagulants / therapeutic use
  • COVID-19* / complications
  • Hemorrhage / chemically induced
  • Heparin / adverse effects
  • Heparin, Low-Molecular-Weight / therapeutic use
  • Humans
  • Venous Thromboembolism* / drug therapy
  • Venous Thrombosis* / drug therapy


  • Heparin
  • Anticoagulants
  • Heparin, Low-Molecular-Weight