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Given the coagulopathy that often complicates severe COVID-19 illness, certain best practices should be followed for venous thromboembolism (VTE) prevention and treatment, even if data to inform these decisions are scarce, experts said.

Critically or acutely ill COVID-19 patients should receive anticoagulant thromboprophylaxis (unless contraindicated), according to recent guidance from the American College of Chest Physicians. Other interim recommendations from the group include:

• For thromboprophylaxis, low-molecular-weight heparin (LMWH) -- or the related fondaparinux (Arixtra) -- is favored over unfractionated heparin (UFH), which is in turn recommended over direct oral anticoagulants (DOACs)
• Discourage use of antiplatelets for VTE prevention in critically or acutely ill patients
• Discourage routine ultrasound screening for the detection of asymptomatic deep vein thrombosis (DVT) in the critically ill
• LMWH and UFH are favored over oral anticoagulants for acutely ill patients with proximal DVT or pulmonary embolism
• Any patient with COVID-19 and proximal DVT or pulmonary embolism should be placed on anticoagulation therapy for at least 3 months

These guidelines, voted on by a consensus panel and last week in the journal CHEST, were echoed during an American College of Cardiology (ACC) webinar on Thursday discussing VTE in COVID-19.

All patients hospitalized with the infection should receive some form of thromboprophylaxis given their increased risk of abnormal clotting, said Deborah Siegal, MD, of McMaster University in Hamilton, Ontario, during the ACC discussion.

Adam Cuker, MD, MS, of the University of Pennsylvania in Philadelphia, said that the preference at his center is LMWH, which reduces the number of injections and therefore the number of times a nurse needs to enter the rooms of COVID-19 patients, saving personal protective equipment.

LMWH is preferred over UFH because of the lower risk of heparin-induced thrombocytopenia, according to Cuker.

A big question mark hangs over the dosing of prophylactic anticoagulation for patients with COVID-19: should they receive a standard dose for VTE prophylaxis, an intermediate or escalated dose, or a full-on therapeutic dose?

"We don't have the data yet," lamented Gregory Piazza, MD, MS, of Harvard Medical School and Brigham and Women's Hospital in Boston.

"New trials appear on every day looking at thromboprophylaxis in COVID-19," he said. "Until we have those trials, it's hard to know whether you would pick an intermediate or full dose. The important thing is that patients are protected in some form."

Given that COVID-19 is a key risk factor for VTE, Siegal said she likes "to be more aggressive" in her anticoagulant dosing if she can, while weighing the patient's risks of bleeding and renal impairment.

Finally, ACC discussants were faced with the question of post-hospital VTE prophylaxis among those who recover from COVID-19.

The pandemic environment raises several concerns, said Barbara Wiggins, PharmD, of Medical University of South Carolina in Charleston, noting that patients are going home before they are fully recovered, and it's unknown how long their prothrombotic state lasts or when they will be able to seek further medical care.

Post-hospital prophylaxis is usually associated with a modest reduction in VTE risk offset by increased bleeding and increased costs to the healthcare system -- a thinking that has been revisited in the current COVID-19 era, Cuker said. "At our institution, we have been much more encouraging of discharging COVID-19 patients with thromboprophylaxis provided they meet certain criteria."

Anticoagulation guidance in COVID-19 first appeared in March after early Chinese reports of abnormal clotting in certain patients. A consensus group, representing the International Society on Thrombosis and Haemostasis and other professional societies, published guidance in April recommending post-discharge prophylaxis with LMWH or DOACs.

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