Major risk factors for severe Covid-19 - such as diabetes, obesity and advanced age - are linked to worn-out blood vessels that make clotting more likely, says John Atkinson, an immunologist and rheumatologist at Washington University School of Medicine in St. And in a July article in the New England Journal of Medicine, autopsies revealed that the lungs of people who died of Covid-19 were nine times as likely to be speckled with tiny clots as those of people who died of influenza. In a February report by researchers in China, about 70 percent of people who died of Covid-19 had widespread clotting, while few survivors did. ![]() In a July report in the journal Blood, Al-Samkari and colleagues found that nearly 10 percent of 400 people hospitalized for Covid-19 developed clots. “Everything was clotting,” Al-Samkari says. The clots filled needles used to draw blood, or the tubing connecting patients to medication drips and machines. But as Covid-19 patients filled hospital wards, it became apparent that their clotting was more frequent, more widespread and more severe than in other infections. Inflammation due to infection can also tip those clotting-factor dominoes. Depending on their location, clots can lead to problems such as breathing difficulties, heart attack, stroke and death. Being bedridden encourages clotting, especially in the legs and pelvis, and the clots may migrate to the lungs where they impede the organs’ ability to load the blood with oxygen. “It’s sort of a domino effect,” says Hanny Al-Samkari, a hematologist at Massachusetts General Hospital in Boston.Ĭlotting in uninjured blood vessels is a common occurrence in hospital patients, especially those in the intensive care unit. ![]() Proteins in the blood called clotting factors switch from dormant to active states in a chain reaction, and build a fibrous mesh. ![]() When a blood vessel is injured, cell fragments called platelets rush to plug the leak. Ongoing clinical trials may help to provide clearer guidelines in the future, but with so much about this virus still unknown, for now they must guess at best treatments and doses.Ĭlotting is normally a good thing. Researchers and clinicians are working to understand why, and trying medications to tamp down the clotting or the intense immune responses that seem to underlie it. Within a couple of weeks, Laurence observed several similar, striking cases - making some of the earliest observations that the blood-clotting process could go horribly awry in severe instances of Covid-19.
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