 Activation of blood platelets is a typical finding in patients with systemic inflammation and sepsis.They seem to mediate key pro-inflammatory mediator secretion, immune-cell activation while their adhesion to the endothelium enhances the pro-coagulatory activity of endothelial cells impairing microcirculation thus, may lead to multiple organ dysfunction. However, the exact effects of bacterial products on platelet function have not been found to be consistent and may vary according to the species, the timing of the study, and the pathogenesis of sepsis. Data vary, including both increased and decreased platelet reactivity and aggregation among patients with sepsis compared to healthy controls. Defining platelets behaviour during sepsis is particularly important in view of recent findings revealing potential association between antiplatelet therapy and reduction in short term mortality, incidence of acute lung injury and intensive care unit admission in critically ill patients.This study aims to measure P2Y12 mediated platelet reactivity, -using the point-of-care P2Y12 VerifyNow assay, in platelet reactivity units PRU- along different stages of sepsis, including bacteremiauncomplicated infection, sepsis, severe sepsis and septic shock. Subgroup follow up of patients going along different stages will also be performed. At the end of this study analysis of clinical and laboratory findings in correlation with platelet reactivity will be performed to assess platelet aggregation during sepsis. 