Administering a full dose of a standard blood thinner early to moderately ill hospitalised patients with COVID-19 could halt the formation of blood clots and reduce the risk of severe disease and death, according to a study.

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COVID-19 is marked by heightened inflammation and abnormal clotting in the blood vessels, particularly in the lungs, and is believed to contribute to progression to severe disease and death. The researchers at St. Michael's Hospital and the University of Vermont Larner College of Medicine in Canada noted that heparin -- a blood thinner given regularly at a low dose to hospitalised patients stops clots from forming and reduces inflammation. The yet-to-be-published study, post on the preprint server MedRxiv, examined the benefits of administering a therapeutic full dose of heparin versus a prophylactic low dose to moderately ill patients admitted to hospital wards with COVID-19.

"This study was designed to detect a difference in the primary outcome that included ICU transfer, mechanical ventilation or death," says Mary Cushman, study co-principal investigator and a professor at the University of Vermont's Larner College of Medicine. The primary outcome was a composite of ICU admission, mechanical ventilation, or death up to 28 days, the researchers said, adding that safety outcomes included major bleeding. Primary outcome occurred in 37 of 228 patients with therapeutic full dose heparin, and 52 of 237 with low dose heparin.

Four patients with therapeutic heparin died compared to 18 with prophylactic heparin. "While we found that therapeutic heparin didn't statistically significantly lower incidence of the primary composite of death, mechanical ventilation or ICU admission compared with low dose heparin, the odds of all-cause death were significantly reduced by 78 per cent with therapeutic heparin," said first author and co-principal investigator Michelle Sholzberg, an assistant professor at the University of Toronto. Peter Juni, a co-principal investigator, from the University of Toronto, said that the research clearly indicated that therapeutic heparin is beneficial in moderately ill hospitalised COVID-19 patients.

The study showed that therapeutic heparin is beneficial in moderately ill hospitalised patients but not in severely ill ICU patients, he said. "We believe that the findings of our trial and the multiplatform trial taken together should result in a change in clinical practice for moderately ill ward patients with COVID-19," Sholzberg added.