Risks of treatment to prevent post-Covid clot is still unknown

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Covid is a disease known as thrombogenic, that is, it is characterized by having a high risk of clot formation.

The incidence of thrombosis in patients with Covid, according to a study published in August in the scientific journal The Lancet, ranges from 0.6 to 2 per 100,000 people, about 8 to 10 times greater than the risk of thrombosis by some vaccines against Covid-19. illness.

During the pandemic, doctors adopted anticoagulants such as heparin as a routine treatment to avoid or reduce such risks, often in doses above those recommended by health entities, such as the WHO (World Health Organization).

To date, however, studies that have evaluated the risks and benefits of these drugs to prevent post-Covid clots are not conclusive.

According to vascular surgeon and director of publications at the Brazilian Society of Thrombosis and Hemostasis, Eduardo Ramacciotti, since the beginning of the pandemic, scientists have reached three main global recommendations on the use of heparin based on randomized, double-blind clinical studies, considered the scientific gold standard. “And it is with great pride that I say that Brazil actively participated in this scope of evidence”, says he, who is the author of three studies published in specialized journals on the use of anticoagulant drugs.

In three different situations, the patient with symptomatic Covid without hospitalization, the one hospitalized with a serious condition and the patient before hospitalization (only in the ward), the risks of treatment with heparin outweighed the benefits.

Patients admitted to intensive care units (ICU) with a severe condition and high risk of developing clots, the administration of heparin did not significantly reduce this incidence. On the contrary, some studies have been stopped for the so-called futility reason, which is when the study brings more risks than benefits.

On the other hand, post-discharge use for up to 35 days after patient discharge reduced the risk of developing post-Covid thrombosis by up to 67%, according to a study published last year based on data from 320 patients in hospitals in the United States. Brazil.

In a study conducted in Brazil at the beginning of the pandemic with 184 patients hospitalized in ICUs, the researchers observed that 49% of them had some type of thromboembolic event, with 87% having a pulmonary embolism. Mortality among these patients was 14%, and 6.6% had a stroke.

Scientists stress that decisions made early in the pandemic to treat high-dose heparin were often made without scientific evidence, and now, two and a half years later, those risks have been reassessed.

“The conducts should not be taken based on biological plausibility [um conceito biológico é observado e por isso vai ser verdadeiro na vida real], but based on evidence. In a moment of uncertainty, you can even make individualized treatment decisions, but without having the correct evidence”, explains cardiologist Pedro Silva, from Hospital Samaritano Paulista.

Silva is a researcher on a study that evaluated the body of evidence regarding the use of anticoagulants in Covid patients in four phases: pre-ambulatory, outpatient, critically hospitalized (ICU) and post-discharge. According to him, the group that was considered to have the most benefit at the beginning of the pandemic, those hospitalized in the ICU, was the one that, on the contrary, showed a risk of death from bleeding.

For patients who were not hospitalized or who only had symptomatic Covid, without the need for hospital care, the benefits of using anticoagulants did not outweigh the risks of bleeding, which contraindicates the use of anticoagulants by low-risk patients and out of hospital use. “There is no benefit of ‘homemade’ anticoagulation, and the recommendation is even if you have a history of thrombosis and are diagnosed with Covid, if you are vaccinated, the chance is to have a mild picture of the disease. But look for your doctor and follow the recommendation”, says Ramacciotti.

Silva recalls that in addition to patients with Covid having a high risk of clot formation, the condition caused by the coronavirus disease also consumes on a large scale the platelet elements that help with clotting, so at the same time it forms clots it also has a high risk of bleeding .

“That’s why the use of anticoagulants without hospitalization found no benefit, because the balance is very delicate. At the same time that it can help in the elimination of clots, drugs such as heparin can cause bleeding”, he explains.

Regarding aspirin, an antiplatelet agent, Ramacciotti says that no study has found evidence in favor of its use to prevent post-Covid thrombosis. “And one of the craziest things I’ve seen is the recommendation to take anticoagulants before taking the Covid vaccine. There is absolutely no evidence of taking anticoagulants before immunization, on the contrary,” he says.

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