Screening for and treating venous thromboembolic events in COVID-19 patients

Stuttgart/New York – An infection with SARS-CoV-2 does not only cause severe pneumonia. Experience over recent weeks has shown that thromboses and embolisms are relatively common with COVID-19. During the body’s systemic inflammatory response, the virus seems to also attack the endothelial cells lining the interior surface of blood vessel, which results in uncontrolled blood clotting. According to an article in the medical journal TH Open (Thieme, New York, 2020), Swiss clinicians recommend the use imaging techniques to systematically screen patients for possible thromboses and aggressive treatment with agents that can dissolve these. Additional compression therapy could also be helpful.

Many patients who are treated for COVID-19 in hospital develop blood clots. Undetected, they can cause fatal pulmonary embolisms. Since early April, clinicians at the Cantonal Hospital Fribourg, Switzerland have been using duplex ultrasound to regularly screen all COVID-19 patients for thrombi in the neck, arms and legs. If the result is inconclusive, the examination is repeated within seven days. CT angiography is carried out if a pulmonary embolism is suspected in order to visualise any blockage in the pulmonary arteries by a thrombus.

Angiologist Daniel Périard and his team report that they found thromboses in 17 of 29 patients in this way. That is more than 58 percent. Two of these patients had developed a pulmonary embolism. The D-dimer levels were elevated in the patients with thrombosis. This laboratory result indicates that the body is in the process of breaking down blood clots, and therefore indirect evidence that they have formed. Some of the patients also had increased LDH levels. This enzyme is released into the bloodstream when tissue is damaged. Six of a further 29 patients who were treated in general wards were found to have developed a venous thromboembolic event (VTE). That equates to about 20 percent.

Once diagnosed with COVID-19, most of these patients were given one subcutaneous injection of enoxaparin or two injections of unfractionated heparin per day, the hospital’s usual thrombosis prophylaxis protocol. Since VTEs can develop despite these prophylactic measures, Périard believes that all COVID-19 patients should be given higher doses of the prophylactic medication and regularly screened with duplex ultrasound.

In the Swiss university hospital’s intensive care unit, all patients who tested positive for thrombosis are treated with a therapeutic dose of either enoxaparin or unfractionated heparin. Rivaroxaban, another anticoagulant, is used in the general wards. According to Périard, a marked, but not complete, reduction in new VTEs and pulmonary embolisms was seen at the hospital in the first four weeks following introduction of the new protocol.

He thinks compression therapy or other supportive measures should also be added to prophylactic medication. Compression stockings are sufficient for patients in general wards, but Périard recommends intermittent pneumatic compression devices for ICU patients. These devices consist of cuffs around the legs that regularly change pressure, imitating the skeletal-muscle pump which in healthy people prevents the formation of blood clots in the veins of the legs.

G. Grandmaison, A. Andrey, D. Périard, R. P. Engelberger, G. Carrel, S. Doll, J.-B. Dexpert, C. Krieger, H. Ksouri, D. Hayoz, G. Sridharan:
Systematic Screening for Venous Thromboembolic Events in COVID-19 Pneumonia
TH Open 2020; 4 (2); e113-e115; published online as “Letter to the Editor” on 8th June 2020