Blood thinners may protect against COVID-19 complications

• A new study has found that administering heparin-based blood thinners to patients with COVID-19 in the first 24 hours of hospital admission reduced the risk of death.
• The researchers observed a 27% reduced risk of 30-day mortality among patients who received blood thinners.
• Severe bleeding that required a blood transfusion occurred in 4.6% of patients and was not significantly linked with early intervention to prevent coagulation.

The ongoing COVID-19 pandemic has caused more than 2 million deaths throughout the world. The United States currently has the highest number of related mortalities, more than 499,000 at the time of publication.

While emerging COVID-19 vaccines may eventually help reduce the number of deaths, the relatively slow rollout in many countries has led to concerns that seeing significant effects will take time.

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Excessive blood clotting is a hallmark of some severe COVID-19 cases. In May 2020, thrombosis expert Prof. Beverley Hunt told Medical News Today that she was surprised to find such high levels of clotting factors in the blood of patients with severe COVID-19.

“Now we know that these patients have incredibly sticky blood. This stickiness is causing them to have deep vein thrombosis. And of course, if you have a deep vein thrombosis, bits of it can break off and travel through your body and block some of the blood supply to the lungs,” Prof. Hunt explained.

At the hospital where she works, patients were routinely receiving small doses of anticoagulants to reduce the risk of blood clotting. And as data on the use of blood thinners began to emerge, updates to clinical guidelines followed suit.

The National Institutes of Health (NIH) recommend that everyone who is hospitalized for COVID-19 treatment, except those who are pregnant, receive prophylactic anticoagulants.

Recently, a team of researchers in the United Kingdom and the U.S. published data from an observational cohort study. They found that anti-clotting therapy was linked with significantly fewer deaths among people admitted to the hospital with COVID-19.

“Our results provide strong, real-world evidence to support guidelines recommending the use of prophylactic anticoagulation as initial treatment for patients with COVID-19 on hospital admission,” the researchers write.

The results of the study were recently published in BMJ.

Collecting patient data

The team analyzed electronic health record data from veterans registered with the U.S. Department of Veteran Affairs who were admitted to a hospital with COVID-19 between March 1 and July 31, 2020.

They collected information from 4,297 veterans who had tested positive for COVID-19 either 14 days before admission or within 14 days of the hospital stay.

People were excluded from the study if they had used anticoagulants — drugs that prevent excessive blood clotting — in the 30 days before the admission. People were also excluded if they were actively bleeding or had severe anemia.

The median age was 68 years old, and most patients were men living in urban environments in the south. Among the patients, 45.1% were non-Hispanic Black, 37.3% were non-Hispanic white, and 11.8% were Hispanic.

Of the 4,297 patients in the study, 3,627, or 84.4%, received prophylactic anticoagulation medication within 24 hours of hospital admission. This medication is used to prevent blood clots in the veins, or venous thromboembolism.

About 30.2% of the patients received subcutaneous heparin, a drug that prevents blood clots from forming, and 69.1% received a blood thinner called enoxaparin.

Reduced risk of death

The 30-day mortality rate was lower among the patients who received prophylactic anticoagulation medication than those who did not.

The researchers write that:

“Receiving prophylactic anticoagulation was associated with a 27% decreased risk of death over the first 30 days, compared with receiving no anticoagulation.”

A total of 622 deaths occurred among the 4,297 patients in the study within 30 days of admission to the hospital. Of that number, 513 of the deaths involved patients who received prophylactic anticoagulation. The researchers note that 82% of the deaths occurred during the hospital stay.

“The evidence of benefit was strongest among patients not admitted to the [intensive care unit] within the first 24 hours of admission,” they observe in their study paper.

Only 4.6% of patients experienced a bleeding event that required a transfusion. This adverse effect was not associated with the prophylactic anticoagulation medication.

Several study limitations

This study was observational, and without the results of a randomized clinical trial, it is difficult to confirm whether the anticlotting treatment was effective or whether another variable, such as a patient characteristic or another treatment, could have influenced the results.

Another major limitation is the lack of an official cause of death for these patients. While the researchers reason that the reports strongly indicated venous and arterial thrombosis, it is possible that other COVID-19 complications may have been fatal.

Also, the researchers did not account for some risk factors for venous thromboembolism, such as immobility, weakened or impaired muscle movement, or specific thromboembolism biomarkers. This was because the information was not fully available to them at the time of the analysis.

In addition, the findings may not apply to the general population, as the study only included older participants, who had an increased risk of other health conditions. And only a fraction of the patient cohort was female.

Refining hospital guidelines

The Centers for Disease Control and Prevention (CDC) report that an increased risk of thromboembolism is associated with severe COVID-19, and they say that treatment guidelines for COVID-induced blood clotting are always being updated as new information emerges.

The researchers conclude that their results give real-world evidence of the effectiveness of blood-thinning medication upon hospital admission.

The NIH have now updated their guidelines for COVID-19 hospital admission to recommend early intervention with blood-thinning medication when appropriate.

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