COVID-19 is an infectious disease caused by the beta-coronavirus SARS-CoV-2 that in 2020 has spread worldwide. In most severe patients, the clinical picture begins with respiratory failure further deteriorating up to multiple organ failure. Development of coagulopathy is the most adverse prognostic. Analyzing currently available clinical data revealed that 71.4 % and 0.6 % of survivors and fatal cases, respectively, demonstrated signs of overt disseminated intravascular coagulation (DIC). Monitoring D-dimer level, prothrombin time, platelet count and fibrinogen content is important for determining indications for treatment and hospitalization in COVID-19 patients. In case such parameters deteriorate, a more pro-active “aggressive” intensive care should be applied. Low molecular weight heparin (LMWH) should be administered to all patients with diagnosed COVID-19 infection (including non-critical patients) requiring hospitalization, but having no contraindications to LMWH.

An issue of the novel coronavirus infection spreading is currently in the first place among others in the list of the international medical community. Due to lack of information, conflicting research findings, multicomponent effect of the virus on the body host, as well as various consequences that the virus triggers in the body, now every medical specialty does study the viral attack pathogenesis. Recent months showed that vascular complications are the most severe in the Coronavirus Disease 2019 (COVID-19) and are the main cause of death in the patients. The mechanisms of vascular complications are complex and affect both the hemostatic system and immune responses, “inflammatory storm”, disorders of the renin-angiotensin-aldosterone system, endotheliopathy, etc.Due to the leading role of vascular complications in the viral infection pathogenesis, several groups of patients are at extra risk, including pregnant women, patients with a burdened obstetric history, with hereditary thrombophilia and antiphospholipid syndrome, and patients after in vitro fertilization (IVF). In this category of pregnant women, use of low-molecular-weight heparins (LMWH) is particularly important for both prevention of vascular and obstetric complications, and for pathogenetic therapy of COVID-19.

For last months, humanity has faced a formidable unknown enemy, which is presented as a new coronavirus infection. Despite the fact that the causative agents of new diseases appear at a certain frequency and that the virus SARS-CoV-2 has certain common properties with its predecessors, at the moment we are dealing with a new unknown pathogenesis of the development of severe complications in patients with risk factors. A final understanding of pathological process mechanisms is the goal of the scientific community. Summarizing research data from different countries, it became obvious that in severe cases of viral infection, we are dealing with a combination of the systemic inflammatory response syndrome, disseminated intravascular coagulation and thrombotic microangiopathy (TMA). Thrombotic microangiopathy is represented by a group of different conditions in which thrombocytopenia, hemolytic anemia, and multiple organ failure occur. The article reflects the main types of TMA, pathogenesis and principles of therapy. The main participants in the process are described in detail, including the von Willebrand factor and ADAMTS-13. Based on the knowledge available, as well as new data obtained from patients with COVID-19, we proposed possible models for the implementation of conditions such as sepsis, TMA, and DIC in patients with severe new coronavirus infection. Through a deeper understanding of pathogenesis, it will be possible to develop more effective diagnosis and therapy.

The pandemic of a new coronavirus infection COVID-19 has become a real challenge to humanity and the medical community and has raised a number of medical and social issues. From the currently available information on clinical cases of COVID-19, it follows that COVID-19 patients in critical condition have a clinical picture of disseminated intravascular coagulation (DIC), septic shock with the development of multiple organ failure, which justifies the anticoagulant therapy use in patients with COVID-19. In addition to isolating virus DNA from biological material and diagnosing SARS-CoV-2, the use of simple and easily accessible laboratory markers in the blood is necessary for the management of patients with COVID. If the activation of coagulation processes is sufficient enough, the consumption of platelets and blood clotting factors can be diagnosed by laboratory methods in the form of prolongation of routine blood clotting tests and increasing thrombocytopenia. Hyperfibrinogenemia, increased D-dimer, prolonged prothrombin time, thrombocytopenia, lymphopenia, leukocytopenia, increased interleukin 6, and ferritin are observed in most COVID-19 patients. The degree of increase in these changes correlates with the severity of the inflammatory process and is a prognostically unfavorable sign. In the article authors discuss laboratory monitoring that plays an essential role in this crisis, contributing to patient screening, diagnosis, as well as monitoring, treatment and rehabilitation.

After the vaccination campaign initiation in Europe and the UK, reports of rare cases of atypical thrombosis, including sinus vein thrombosis and splanchnic venous thrombosis, began to appear in association with the use of vector vaccines AstraZeneca (ChAdOx1) and Johnson & Johnson/Janssen. The syndrome called VITT (vaccine-induced immune thrombotic thrombocytopenia) manifested as thrombosis simultaneously with a decrease in platelet count, a significant increase in D-dimer levels and a detection of factor 4 platelet (PF4) antibodies. We present a detailed review of the epidemiology, pathogenesis, clinical presentation, diagnostics and treatment of VITT, which is by its nature an immune complication, similar to the processes occurring in heparin-induced thrombocytopenia (HIT). All international and national organizations and regulatory authorities, including experts in the field of thrombosis and hemostasis and the VITT expert council recommend continuing the prompt mass vaccination against COVID-19 as the only method that can reduce the incidence of severe cases, stop the spread of COVID-19 infection and the emergence of new dangerous mutations in the viral genome. Failure to vaccinate poses an incomparably greater risk of fatal thrombotic and inflammatory complications associated with infections, compared with the risks of extremely rare adverse events that can occur after vaccination. It should be noted that information on VITT, described as a sporadic phenomenon of an abnormal immune response to some variants of vaccines against COVID-19, cannot be translated to other vaccines (including registered in the Russian Federation) and even more cannot be a reason for refusal to use them.