Therapeutic enoxaparin improves gas exchange and decreases the need for mechanical ventilation in patients with coronavirus disease 2019 (COVID-19), according to a study published in Thrombosis Research.

In this open-label, phase 2 study, patients requiring mechanical ventilation were randomly assigned to receive therapeutic enoxaparin or subcutaneous unfractionated heparin (UFH), the standard anticoagulant thromboprophylaxis. Ten patients were assigned to each group, and gas exchange over time was assessed using the ratio of partial pressure of arterial oxygen (PaO2) to the fraction of inspired oxygen (FiO2).

The baseline characteristics and disease severity were similar between the 2 groups. Study authors observed a statistically significant rise in PaO2/FiO2 ratio in the therapeutic enoxaparin group, increasing from 163 (95% CI, 133–193) at baseline to 209 (95% CI, 171–247) after 7 days to 261 (95% CI, 230–293) after 14 days (P =.0004). The prophylactic UFH group did not show statistically significant difference over time; PaO2/FiO2 was 184 (95% CI, 146–222) at baseline, 168 (95% CI, 142–195) after 7 days, and 195 (95% CI 128–262) after 14 days (P =.487).

Patients receiving enoxaparin had a higher ratio of successful discontinuation from ventilation (hazard ratio [HR], 4; 95% CI, 1.035–15.053; P =.031) during 28 days of follow-up compared to patients receiving UFH. Ventilator-free days were higher in patients receiving enoxaparin at 15 days (interquartile range [IQR], 6–16) compared to 0 days (IQR, 0–11) in patients receiving UFH (P =.028). No statistical differences were seen between groups in all-cause 28-day mortality rate, in-hospital mortality rate, and ICU-free days.

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The main limitation of this work was the small sample size from a single center. The PaO2/FiO2 ratio assessment was limited in quantifying pulmonary dysfunction improvement.

The results from this study “demonstrated that therapeutic enoxaparin improved gas exchange over time and increased the ratio of successful liberation from mechanical ventilation,” investigators concluded.


Lemos ACB, do Espírito Santo DA, Salvetti MC, et al. Therapeutic versus prophylactic anticoagulation for severe COVID-19: a randomized phase II clinical trial (HESACOVID). Thromb Res. 2020;196:359-66.