Deadly blood clots in Covid-19-patients – what is behind the observation

Deadly blood clots in Covid-19-patients – what is behind the observation

When blood coagulates, it is usually a good thing: we Have injured us, to form a stopper, which close the wound and Bleeding to death protect. However, it may also happen that these clots will form under certain circumstances in the blood vessels. Then they are to mortal danger. Depending on where a clot occurs, it can tear, and in various organs Hiking: In the brain, blood clots from solve, for example, strokes in the coronary vessels, a heart attack. The Thrombus is fixed in the lungs, it triggers a pulmonary embolism. Larger caps will disturb the gas exchange and with acute shortness of breath, pain and palpitations are noticeable.


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In healthy humans, this blood stopper fortunately, rare. However, certain factors influence the risk: certain medicines including, a hereditary predisposition or surgeries and injuries. Also, certain pathogens can increase the risk – including, apparently, an infection with the Coronavirus Sars-CoV-2. In a small study from Hamburg suggests.

The research group led by Dominic Wichmann from the University hospital Hamburg-Eppendorf (UKE) has examined twelve corpses which were proven to be infected with the Coronavirus, and published the results in the journal “Annals of Internal Medicine”.

Clots in the lungs

It was striking that seven of the twelve patients had developed deep vein thrombosis – despite the fact that before her death, no suspicion of a thrombosis consisted. In four of the patients had a clot and had wandered into the lungs, where it blocked a vessel and a pulmonary embolism triggered. The embolism was in these patients, the direct cause of death. The deceased were between 52 and 87 years of age, predominantly male and vorerkrankt. Approximately half of the patients had coronary heart disease and Asthma, three of them were diagnosed with COPD – also known under the name smoker’s lung.

Especially in the lungs of the deceased, the researchers were able to demonstrate high levels of Sars-CoV-2. In six patients, the Virus was also found in the blood, and in five cases, in the liver, the kidneys or the heart. The researchers conclude that the Virus spread, possibly, over the blood vessels in the body and impact on blood clotting takes up.

Stavros Konstantinides, Director of the center for thrombosis and Hämastose at the University hospital in Mainz, and is familiar with the phenomenon from the medical practice. He estimates that approximately every fourth Covid-19-Patient developed a severe course with a “more or less severe thrombosis and pulmonary embolism”. His estimate is based on patients whose course must stationary be treated in hospital. In most cases, the infection is mild and without complications.

As reasons for the increased risk, he cites several factors: the Receptor is located, to which the Virus binds and in the cells of the body penetrates, not only in the lung tissue, but also in the so-called endothelial cells. This dress blood vessels. “In this way, it is also possible that Sars can infect vessels CoV-2, smaller and larger blood and thrombosis can occur,” says Konstantinides. “But also by the infection of the lungs of Sars-CoV-2 provides for an increased thrombosis risk, the patient’s inflammation by partially severe lung enough oxygen get.”

Covid-19: In the case of a lack of oxygen to pulmonary embolism think

“The lack of oxygen, hypoxia, is itself already a risk factor for thrombosis,” says Konstantinides. In the therapy of Covid patients it is therefore important to ensure an adequate oxygen supply and ventilate Diseased optionally, if you need extra oxygen. Experts from professional societies to discuss whether it makes sense, the blood clotting in Covid-19-inhibit patients as a precaution to dangerous emboli – most experts agree to this. Many questions are still open, says the physician. “We don’t know yet if a low, for the prophylaxis usual dose of Heparin is sufficient, if you need a higher, classic therapy used doses, or even something in between.” All of these question would have to be in a separate study, investigated. Heparin is a substance which inhibits blood clotting.

Especially in the case of Covid patients is often difficult, if the lack of oxygen was due to a pneumonia or an embolism – possibly both causes come into question, emphasizing Konstantinides. The state of health of a patient should deteriorate rapidly, should doctors think, therefore, always to a possible thrombosis and the appropriate diagnostics to initiate.

Embolism about with a lung CT or by certain blood values to determine, says Clemens Wendtner, chief of infectious diseases and tropical medicine at the München Schwabing hospital. An embolism is detected early, it can be used with high-dose Heparin dissolved.

Some patients also develop a tremendous inflammatory response of the immune system to the Virus. Also this could increase the view of Konstantinides the risk of thrombosis. “There are approaches, the Hyper-inflammation in Covid-19-patients by medications that block the excessive immune system to bring back under control,” says Wendtner.

The Munich chief doctor also refers to a preventive dose of Heparin and a sufficient oxygen saturation in the blood to a pulmonary embolism in Covid-19 patients prevent. Good oxygen values are, for example, with a so-called “High-flow oxygen therapy” can be achieved. “In this case, the Patient has high quantities of Oxygen, up to 14 litres per Minute receives, via a mask, without the need for invasive ventilation.” This therapy isn’t working, could be connected to the Patient on a ventilator.

Further studies will be needed

Sars-CoV-2 is not the only pathogen that is associated with blood clots. Other infectious diseases, affect the risk, including the tuberculosis and the Syphilis pathogen, and the varicella-Zoster Virus that triggers the chicken pox. Antiplatelet drugs such as acetylsalicylic acid (Asa, Aspirin), Heparin, and Phenprocoumon (Marcumar), inhibit blood clotting and can prevent clots in special predisposition. At the same time increase the risk for bleeding. The therapy is therefore a need for close medical care.

To be the influence of Covid-19 to the blood clotting more research is needed, stressed Stavros Konstantinides. The exact risks are not yet known – the data is still very thin. Previous clinical studies have some significant limitations, so the physician. “They were generally small, included only small patient collectives, as well as this autopsy study, or you didn’t know according to which criteria the patients were evaluated for pulmonary embolism.”

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