Since severe acute respiratory syndrome coronavirus 2 led to a world pandemic, extensive research has been conducted to identify its characteristics and form an appropriate management plan. One recognized complication of COVID-19 is coagulation defects that can lead to thromboembolic events. We have reviewed the literature to summarize and present the latest research about the pathophysiology, clinical manifestations, anticoagulation use and appropriate dose in COVID-19 patients, as well as the effect of anticoagulation in outpatient and post-hospital settings. The pathophysiology of coagulation abnormalities in COVID-19 is not fully understood yet, but multiple mechanisms appear to be involved, such as a direct viral attack, hyperinflammation, increased immune response, blood stasis, and endothelial injury. Clinical manifestations are mainly venous thromboembolism (deep vein thrombosis and pulmonary embolism), arterial thromboembolism, ischemic stroke, central venous sinus thrombosis, and central retinal vein occlusion. Anticoagulation is widely used in hospitalized patients with COVID-19, unless it is contraindicated. Heparinoid is the main anticoagulant used. However, the appropriate dosage is still debated as research is trying to find a balance between benefits and risks. In outpatients, it appears that anticoagulation has no benefit in contrast to post-hospitalization use, where benefit could be observed in severely affected patients. We concluded that thromboprophylaxis should be used in treating hospitalized COVID-19 patients, but the dosage is still a matter of debate. More research needs to be done on outpatient and post-hospitalized patients to derive accurate conclusions.
