Epidemiology of Severe Sepsis and Septic Shock

Sepsis is defined as the combination of pathologic infection and physiological changes known collectively as the systemic inflammatory response syndrome (Martin, 2003). This response results in physiological alterations that occur at the capillary endothelial level. In the early stages, the clinical manifestations of this process are unspecific and it is often underappreciated in clinical practice. However, early recognition of this syndrome is vital to reducing mortality in sepsis. From clinical studies sepsis can be seen as a continuum of severity that begins with an infection, followed in some cases by sepsis, severe sepsis – with organ dysfunction – and septic shock. There has been a substantial increase in the incidence of sepsis during the last decades, and it appears to be rising over time, with an increasing number of deaths occurring despite a decline in overall in-hospital mortality (Bone, 1992). Advanced age, underlying comorbidities and number of organ dysfunction are factors which are consistently associated with higher mortality in severe sepsis and septic shock. In this chapter we are going to review the definitions of sepsis syndromes, the factors that have contributed to the widening of physicians’ awareness of sepsis, severe sepsis and septic shock; the incidence of severe sepsis and septic shock; the epidemiological data of patients with severe sepsis and septic shock in the emergency departments and intensive care units; the causative microorganisms, and the changes observed over recent years.