MIcrovascular Dysfunction in CRitically Ill cOVID-19 Patients

The study of pathophysiological mechanisms of cellular penetration of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) allows the understanding of organ failures observed in COVID 19. In order to allow its fusion with the cell membrane, SARS-Cov-2 must bind the Angiotensin Converting Enzyme 2 (ACE2) via its Spike protein. This process requires the priming of the viral S protein by a cellular serine protease TMPRSS2. Thus, any cell co-expressing these two receptors is a potential target for the virus. Among all the cells for which this co-expression could be observed, endothelial cells and vascular pericytes seem to be potential targets, whose infection could lead to the development of an endothelial dysfunction responsible for microcirculatory dysfunction. In addition, inappropriate host immune system response observed in Covid-19 with massive production of pro-inflammatory cytokines as IL-6, TNF α and VEGF could lead to endothelial dysfunction through neutrophils, monocytes and macrophages mobilization producing Reactive Oxygen Species that increase endothelium and glycocalyx damages. The resulting pro-adhesive, pro-vasoconstricting and prothrombotic effects could lead to vascular micro-thrombosis, capillary plugging and impairment of capillary flow. Whether endothelial dysfunction is caused by direct viral cell infection or pro-inflammatory response is uncertain, but various studies have confirmed that endotheliopathy plays a key role in pathophysiological mechanisms in Covid 19. In the context of critical care, the evaluation of microcirculatory perfusion appears to be a diagnostic tool of major importance. Indeed, microcirculatory dysfunction is directly associated with increased organ failure and mortality in the ICU. In addition, many clinical situations such as sepsis or hemorrhagic shock may be responsible for a loss of hemodynamic coherence between macro and microcirculatory parameters. Thus, the correction of macrohemodynamic parameters (arterial pressure, cardiac output, plasma lactate, central venous oxygen saturation) may be associated with persistent microcirculatory hypoperfusion. It thus appears essential to develop systems for assessing the microcirculation in order to move towards resuscitation guided by microcirculatory objectives. The aim of this study is to describe the sublingual microcirculation and to evaluate endothelial dysfunction in critically ill patient with Covid-19, and to determine whether there is a correlation between the severity of microcirculatory damage, endothelial dysfunction and clinically important outcomes in ICU. The data will serve to develop strategies for individualized management of high-risk patients screened with microcirculation evaluation.