The pandemic of a novel coronavirus infection COVID-19 has become a real challenge to the mankind and medical community and has raised a number of medical and social issues. Based on the currently available information on COVID-19 clinical cases, it follows that COVID-19 patients in critical condition exhibit a clinical picture of disseminated intravascular coagulation (DIC), septic shock with developing multiple organ failure, which justifies use of anticoagulant therapy in COVID-19 patients. In addition to isolating virus RNA from biological material and polymerase chain reaction diagnostics, use of simple and easily accessible laboratory blood markers is necessary for management of COVID-19 patients. If the activation of coagulation processes is sufficient enough, consumption of platelets and blood clotting factors can be diagnosed by laboratory methods as prolongation of routine blood clotting tests and increasing thrombocytopenia. Hyperfibrinogenemia, increased D-dimer level, prolonged prothrombin time, thrombocytopenia, lymphopenia, leukocytopenia, increased concentration of interleukin-6 and ferritin are observed in most COVID19 patients. The degree of increase in these changes correlates with severity of the inflammatory process and serves as a prognostically unfavorable sign. Here we discuss value of laboratory monitoring playing an essential role in such pathological crisis that contributes to patient screening, diagnosis as well as further monitoring, treatment and rehabilitation.

The rate of thrombosis and disseminated intravascular coagulation (DIC) has been increasing in COVID-19 patients. Key features related to such condition include minimal or no risk of bleeding, moderate thrombocytopenia, high plasma fibrinogen as well as complement components level in the areas of thrombotic microangiopathy. The clinical picture is not typical for classic DIC. This review systematizes the pathogenetic mechanisms of hypercoagulation in sepsis and its extreme forms in patients with COVID-19. The latter consist of the thrombosis-related immune mechanisms, the complement activation, the macrophage activation syndrome, the formation of antiphospholipid antibodies, the hyperferritinemia, and the dysregulation of the renin-angiotensin system. Taking into consideration the pathogenetic mechanisms, the biomarkers had been identified related to the prognosis of the disease development. Patients with pre-existing cardiovascular disease and other risk factors, including obesity, diabetes, hypertension, and aging pose the peak risk of dying from COVID-19. We also summarize new data on platelet and endothelial dysfunction, immunothrombosis, and, as a result, thrombotic storm as essential components of COVID-19 severe features.

This article summarizes numerous studies on the relationship of biological processes such as inflammation and thrombosis. The huge role of neutrophils and the extracellular neutrophil traps (NETs) secreted by them has been demonstrated. The discovery of NETs has opened new horizons in the understanding of neutrophil biology and the role of these cells in the body. The use of chromatin in combination with the intracellular proteins, as an effective antimicrobial agent has ancient roots and changes our understanding of chromatin only as a carrier of genetic information. Through NETs, neutrophils can contribute to the development of pathological venous and arterial thrombosis or immunothrombosis, as well as atherosclerosis. NETs release has been shown to be one of the causes of thrombosis in conditions such as sepsis and cancer. The presence of NETs in these diseases and conditions makes it possible to use them or individual components as potential biomarkers. NETs and their components may be attractive as therapeutic targets. Further studies of neutrophils and NETs are needed to develop new approaches to the diagnosis and treatment of inflammatory and thrombotic conditions. Perhaps long-forgotten drugs will find a new area for effective use.

The pandemic of a new coronavirus infection (Coronavirus Disease 2019, COVID-19) caused by SARS-CoV-2 became a real challenge to humanity and the medical community in 2020 and raised a number of medical, social and even philosophical questions. An almost avalanche-like increase in the number of infected people in a short time, due to the high contagiousness of viral infection, allowed us to identify groups of patients with mild, moderate and severe forms of the disease. Doctors around the world are faced with an acute problem of treating a large number of patients in critical conditions caused by COVID-19. 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. The first part of the article discusses the pathogenesis of non-specific universal biological responses of the body in critical condition - from the Sanarelli-Schwartzman phenomenon to the DIC, septic shock, systemic inflammatory response syndrome and the so-called neutrophil extracellular traps (NETs). The questions of cytokine storm in severe forms of systemic inflammatory response syndrome (SIRS), the role of inflammation in the activation of coagulation, and the relationship between inflammation and thrombosis are discussed. Modern ideas about the mechanisms of so-called NETosis, their role in the occurrence of immunothrombosis and inflammation-induced thrombosis in autoimmune diseases - vasculitis, antiphospholipid syndrome, and systemic lupus erythematosus is highlighted. The article discusses the possibility of participation of ADAMTS-13 metalloproteinase in the pathogenesis of multiple organ failure in severe endotheliopathy in patients with viral septic shock.

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.

Numerous studies have proven a close relationship between inflammatory diseases and the state of hypercoagulability. In fact, thromboembolic complications represent one of the main causes of disability and mortality in acute and chronic inflammatory diseases, cancer and obstetric complications. Despite this, the processes of hemostasis and immune responses have long been considered separately; currently, work is underway to identify the molecular basis for a relationship between such systems. It has been identified that various pro-inflammatory stimuli are capable of triggering a coagulation cascade, which in turn modulates inflammatory responses. Neutrophil extracellular traps (NETs) are the networks of histones of extracellular DNA generated by neutrophils in response to inflammatory stimuli. The hemostasis is activated against infection in order to minimize the spread of infection and, if possible, inactivate the infectious agent. Another molecular network is based on fibrin. Over the last 10 years, there has been accumulated a whole body of evidence that NETs and fibrin are able to form a united network within a thrombus, stabilizing each other. Similarities and molecular cross-reactions are also present in the processes of fibrinolysis and lysis of NETs. Both NETs and von Willebrand factor (vWF) are involved in thrombosis as well as inflammation. During the development of these conditions, a series of events occurs in the microvascular network, including endothelial activation, NETs formation, vWF secretion, adhesion, aggregation, and activation of blood cells. The activity of vWF multimers is regulated by the specific metalloproteinase ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13). Studies have shown that interactions between NETs and vWF can lead to arterial and venous thrombosis and inflammation. In addition, the contents released from activated neutrophils or NETs result in decreased ADAMTS-13 activity, which can occur in both thrombotic microangiopathies and acute ischemic stroke. Recently, NETs have been envisioned as a cause of endothelial damage and immunothrombosis in COVID-19. In addition, vWF and ADAMTS-13 levels predict COVID-19 mortality. In this review, we summarize the biological characteristics and interactions of NETs, vWF, and ADAMTS-13, the effect of NETs on hemostasis regulation and discuss their role in thrombotic conditions, sepsis, COVID-19, and obstetric complications.