This blog looks at whether this is a common occurrence and what may be causing it.


At the Mount Sinai hospital, a case series of five patients have been put together, ready to be published in the New England Journal of Medicine. It details patients aged 33, 37, 39, 44, and 49 who all began to experience a sudden onset of symptoms including slurred speech, confusion, drooping on one side of the face, and feeling dead in one arm. At the time of writing one has sadly died, two remain hospitalized and one is in rehab. Only the youngest is able to speak. All of them were found to be COVID positive.

This drastic case series highlights a growing problem of strokes and clotting disorders in COVID patients, one noted by medics across the world. This blog looks at whether this is a common occurrence and what may be causing it.

Before reading this blog it will be helpful to read our previous blog on why and how blood clots.


In mid-February Tang et al published a paper noting that patients with abnormal clotting parameters were associated with a poorer prognosis. In their study, 11% of their patients died, but out of these patients, 71% had these abnormal parameters, compared to just 0.6% of survivors. The patients who died also demonstrated DIC (disseminated intravascular coagulation), a condition in which clotting is triggered in the patients' blood across the body, not just at the site of injury.

There is one major issue with this study. In most European hospitals patients receive anticoagulant medications on a daily basis. This is because lying in a hospital bed when ill can promote the formation of clots in your legs. Most hospitals in China do not provide this anticoagulation, but even then the incidence of clotting is remarkably high.

After this, the evidence begins piling up. 9th April, Cui et al found 25% of patients with severe COVID had clots in their legs, of which just under half died. Looking at a specific clotting parameter (D-DIMER) was remarkably accurate at predicting high-risk patients.

Italian doctors found in 16 patients in critical care with severe Acute Respiratory Distress Syndrome (a severe inflammatory condition caused by COVID) also had deranged clotting parameters.

French studies had found these sickest patients often had large clots in their lungs, blocking blood flow in the lung and causing severe issues in keeping the patient's blood well oxygenated.

Some studies showed even patients hooked up to artificial lungs (known as ECMO) were not safe from the problems caused by excessive clotting.


So why is this occurring? As with everything in medicine, the answer is complicated and usually multifactorial. So we will simplify it.

We must look at the platelets in our blood. These fragmented cells have an important role in triggering the clotting cascade and creating a clot. During an infection white blood cells (important immune cells responsible for finding and destroying invading organisms) release many chemical signals around an infection site. This triggers platelets, the formation of small protein meshes that can literally net the viral particles in the blood.

But it looks like they have an anti-viral role as well. Researchers have found specialist receptors on platelets that recognize viruses in the blood, leading to the release of specialist anti-viral molecules that target and destroy the viruses. This is an interesting finding because it is white blood cells that are known to destroy invading organisms.

So how does it go wrong? In severe infections, there is a very large viral load, and this can cause an excessive response. Too many white blood cells release too many chemical signals, causing too many platelets to activate. The same thing can occur with the virus directly activating too many platelets at once. This results in clots forming in the blood throughout the body, including the lung and the brain. It is another instance of the body falling victim to its own protective mechanism.

A second problem is that as these platelets are activated, they and the clotting proteins in the patient’s blood are “used up”. This is dangerous, because without these platelets and clotting proteins the body is unable to stop any bleeding sites. Profuse bleeding can occur from small injuries, further complicating the treatment of the patient.

So what can be done?

Hospitals have already started looking at giving patients with severe COVID anticoagulation therapy. And it seems in patients with deranged clotting, giving anticoagulation therapy can lower mortality.  The International Society on Thrombosis and Haemostasis (Clotting) has recommended that patients with severe COVID receive high dose anticoagulation medication to thin their blood, because these patients are at such high risk of clots. This regime will be used for hospital patients and those in critical care.

And what about for the everyday public? Should we be worried? So far the data suggests this is only happening in people suffering from severe symptoms of COVID. But the incident in New York certainly raises some questions, and it will be interesting to read their report in NEMJ. Should you panic and start taking anti-coagulant medication at home? Definitely not. But what you should do is be educated in the symptoms of common diseases caused by clots. Diseases such as strokes and DVTs.


Remember, act F.A.S.T

  • Facial Droop on one side
  • Arm or hand on one side feels numb or weak with reduced power (same in one leg)
  • Slurred speech making it difficult to understand
  • Time to phone an ambulance

Other symptoms can include sudden loss in balance, sudden loss in vision in one eye, problems swallowing, and more.


Look out for a swollen, painful calf on one side that is hot to touch.


If you have a swollen, painful calf and are also having trouble breathing, with some sharp stabbing pain in your chest, contact the emergency services as soon as possible.

Dr Rajan Choudhary, UK, Chief Product Officer, Second Medic Inc


Request A Callback

Request a Callback

Get Quick Consultation & Support
Chat with Whatsapp