COVID-19

Although patients with COVID-19 primarily have a respiratory tract infection, new research is beginning to reveal that patients with severe COVID-19 may have coagulation abnormalities that can cause an increased risk of death (Tang et al, 2020a).

Within the complex interplay of factors present in coagulation, the formation of D-dimer proteins after the fibrinolysis of blood clots has proven to be a powerful predictor of mortality in patients hospitalised with COVID-19 (Zhang et al, 2020). Studies have similarly highlighted a small decrease in platelet count, and a slightly prolonged prothrombin time in patients with COVID-19 and coagulopathy (Guan et al., 2020; Huang et al., 2020).

The incidence of venous thromboembolism is also of particular interest as a significant proportion of patients with severe COVID-19 have venous and arterial thromboembolic complications (Tang et al., 2020b; Middeldorp et al., 2020)

Because of this, recent recommendations by the International Society of Thrombosis and Haemostasis (ISTH) advise the monitoring coagulation markers and using anticoagulation treatment with low molecular weight heparin (LMWH) for all patients who require hospital admission for COVID‐19 infection (Thachil et al., 2020). LMWH is widely available as it is common practice to use it as a primary bridging therapy agent.

But is there sufficient evidence to suggest that anticoagulation treatment improves patient outcomes?

Due to the rapid progression of the COVID-19 pandemic, research is still being carried out and the decision of whether or not to use anticoagulation therapy in patients with severe COVID-19 infections remains contentious.

Research has found blood clots in small vessels of people with severe COVID-19 (Magro et al., 2020) and a recent observational study found that systemic anticoagulation is associated with improved outcomes among patients hospitalised with COVID-19 and on mechanical ventilation (Paranjpe et al., 2020). This was also seen in another study where significant coagulopathy correlated with disease severity and a reduced intravascular coagulation with thromboprophylaxis (Fogarty et al., 2020).

Unfortunately, treatment with anticoagulant therapy has the potential for serious side effects. Anticoagulant therapy has a risk of haemorrhage if there is a high level of anticoagulant within the blood stream and monitoring is essential to ensure patient safety. There must therefore be clear strategies of when to use anticoagulation treatment and how to reverse it in cases of severe bleeds or when surgery is required.

While scientists are continually working to find new vaccines, improve testing and understand the pathogenesis of the disease, research is being carried out to build a clearer picture of how clotting occurs in people with COVID-19.

Currently, the utility of anticoagulation therapy and the appropriate level of dosing is still a matter of hot debate. Various novel anticoagulants developed over the years for a wide variety of targets, yet little research has so far been carried out to determine the best anticoagulants for treating COVID-19 associated blood clotting.

Trials are currently in progress to determine whether anticoagulation improves outcomes for patients hospitalized with COVID-19 and assess the effectiveness of varying doses (NCT04367831; NCT04372589; NCT04345848; NCT04366960). An extensive study is also planned for 5,000 COVID-19-positive patients to evaluate the effectiveness of three types of antithrombotic therapy (Mount Sinai, 2020).

These trials and others are building a clearer picture of the role of COVID-19 in the circulatory system and will help healthcare professionals choose the best treatments for their patients as we continue to progress through this pandemic and back to normality.

If you found this interesting, you may also enjoy reading about evaluating a fixed-dose strategy for urgent VKA reversal or find other recent publications on anticoagulation and its reversal by visiting our publication digests section.