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Covid-19 and Blood Clots

One potential consequence of Covid-19 is a range of blood clotting abnormalities, which affect up to a third of those who experience the severe version of the disease. This set of complications is responsible for some of the serious harm that the disease can cause. Covid-19 is not the only condition that can lead to a clotting disorder, of course, and it’s worth understanding some basics about normal and abnormal clotting.
The term “blood clots” is often applied to any condition in which clots form anywhere in the body when or where they shouldn’t. The sites that concern us here are within blood vessels, most commonly veins. Obviously, we want our blood to clot when we bleed from an injury. Normal clotting occurs through a complex mechanism that includes:

– Constriction of injured blood vessels.
– Adhesion of platelets that quickly patch them.
– Chemical clotting factors that coagulate other blood cells to form the clot.
– Deposition of fibrin, a soluble fibrous protein, that strengthens the clot while the tissue heals around it.
The complexity of the process makes it susceptible to malfunction, both by failure to properly form a clot or by forming one when it isn’t called for.
The most common clotting abnormality is thrombophlebitis in the superficial veins of the legs, with redness, swelling, and tenderness along the course of the vein. Although it is not generally a high-risk condition, it can become severe and should be evaluated for treatment by a health care provider.
Serious forms of Covid-19 can cause abnormal clots called thrombi in both small and large blood vessels, which can interfere with blood flow. In small vessels this is worst in feet and toes. It can reduce oxygenation in the tissues, causing pain, and if extreme it can cause necrosis or tissue death.
In larger vessels, thrombi can break off from the wall of the vessel and travel to the lungs, a process called embolization. Pulmonary emboli are serious and can result in lung injury, shock, and death. As a result of this risk, anticoagulant medication is a standard treatment for hospitalized Covid patients.
Severe Covid-19 can cause abnormal clotting as a result of the overwhelming inflammatory response that may occur. It is an overreaction of the immune system to the virus. Reducing this with anti-inflammatory medication is also a standard of treatment in severe cases.
Of course, Covid-19 isn’t the only cause of abnormal clotting. Conditions that increase the risk include pelvic surgery, surgery of the legs, pregnancy, certain genetic conditions, autoimmune diseases, and some cancers. Estrogen-containing drugs such as combination oral contraceptives and estrogen treatment or replacement therapy also increase the risk, which brings up the question of whether they should be discontinued if the person taking them is infected with Covid-19. This concern does not apply to progesterone-only contraception.
There is no single right answer to this question, particularly for mild cases of Covid-19 among people who are fully vaccinated. In that instance the infection tends to be mild and shorter than the time it takes for one’s clotting profile to return to normal. But discontinuing an effective contraceptive method may have undesirable consequences as well. In addition, some people may have other health factors that could add to the risk of abnormal clotting. For them, temporary use of an anticoagulant medication may be considered, whether or not alternative contraception is chosen or estrogen is temporarily discontinued. The best course for someone using an estrogen medication is to contact one’s health care provider to help determine if a precautionary change in medication is wise, given their total health circumstances.

About Dr. Joseph Moser

Dr. Joseph Moser is the Chief Medical Officer at University of Maryland Charles Regional Medical Center. He has over 40 years of experience in the health care field and now oversees all of UM Charles Regional Medical Center’s doctors on staff.Dr. Moser headshot

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