The emerging SARS-COV2 virus has shed a new light on the cross-talks between the immune and the hemostatic system. In this study we aim to evaluate the dynamic change in coagulation caused by the modulation of the inflammatory response by interleukin-6 antagonist as assessed by viscoelastic methods in critically ill COVID-19 patients. Furthermore we try to draw attention to possible associations between the endothelial cell injury, inflammation and coagulation.

The emerging SARS-COV2 virus has shed new light on the cross-talk between the immune and the hemostatic system. Pathophysiologically in COVID-19 infection the thrombo-inflammatory process is initiated by the host's exaggerated systemic inflammatory response, also called "dysregulated immune response" that activates both the inflammatory and the coagulation cascade directly by inflammatory mediators and indirectly by causing endothelial cell injury. These mechanisms altogether contribute to the imbalance of the hemostasis that is characterized by a procoagulant state.

In this multicenter prospective observational study, we aim to evaluate the dynamic change in coagulation as a result of immunomodulation by interleukin-6 antagonists in critically ill COVID-19 patients. We will assess the hemostatic system by a viscoelastic hemostasis assay (Clotpro, Haemonetics Corporation, Boston). Furthermore, we try to draw attention to possible associations between endothelial cell injury, inflammation, and coagulation. To compare these parameters we will draw blood for analysis before administration of IL-6 antagonist then 24h after, 48h after, and 7 days after.

Inclusion Criteria:

• Adults (>18 years old)
• Clinical diagnosis of SARS-CoV2 infection with rtPCR confirmation
• Disease severity with the indication of immunomodulation therapy with interleukin-6 antagonist: acute respiratory failure that requires invasive, noninvasive ventilation , or high flow nasal oxygen therapy with the following parameters: FiO2 > 0,4, flow > 30L/min and C Reactive Protein > 75 mg/L

Exclusion Criteria:

• The patient had previously been administered one of the following immunomodulating drug: anakinra, tocilizumab, sarilumab
• Presence of any condition or drug in the medical history that can lead to immunosuppression
• Suspicion of infection (active tuberculosis, bacterial, viral, fungal) or level of procalcitonine higher than 0,5 ng/ml at the enrollment of the patient
• Number of thrombocyte lower than 50 x 109 / L
• More than >120 hours passed between the admission to the ICU and the administration of interleukin-6 antagonist
• Administration of any of the following drugs the week before or during the study: fibrinolytic therapy, factor products (PCC, ATIII, FVIIa, FXIII), fibrinogen, desmopressin, tranexamic acid, blood products (FFP, thrombocyte concentrate)
• Pregnancy
• The patient or his legal guardian does not sign the consent

All adult patients admitted to intensive care units (ICUs) requiring mechanical ventilation with proven COVID-19 infection and treated with interleukin-6 antagonist therapy.

Data will be presented at conferences and in the results part of the article.