Abstract:
COVID-19 is associated with a high incidence of thrombotic complications, which can be explained by the complex and
unique interplay between coronaviruses and endothelial cells, the local and systemic inflammatory response, and the
coagulation system. Empirically, an intensified dose of thrombosis prophylaxis is being used in patients admitted to
hospital with COVID-19 and several guidelines on this topic have been published, although the insufficiency of high
quality and direct evidence has led to weak recommendations. In this Viewpoint we summarise the pathophysiology of
COVID-19 coagulopathy in the context of patients who are ambulant, admitted to hospital, and critically ill or
non-critically ill, and those post-discharge from hospital. We also review data from randomised controlled trials in the
past year of antithrombotic therapy in patients who are critically ill. These data provide the first high-quality evidence on
optimal use of antithrombotic therapy in patients with COVID-19. Pharmacological thromboprophylaxis is not routinely
recommended for patients who are ambulant and post-discharge. A first ever trial in non-critically ill patients who were
admitted to hospital has shown that a therapeutic dose of low-molecular-weight heparin might improve clinical
outcomes in this population. In critically ill patients, this same treatment does not improve outcomes and prophylactic
dose anticoagulant thromboprophylaxis is recommended. In the upcoming months we expect numerous data from the
ongoing antithrombotic COVID-19 studies to guide clinicians at different stages of the disease.
