Sepsis: definition, epidemiology, and diagnosis
Andrew Lever and Iain Mackenzie





What is sepsis?
Systemic illness caused by microbial invasion of normally sterile parts of the body is referred to as "sepsis." This is a term that specifically serves to differentiate an illness of microbial origin from an identical clinical syndrome that can arise in several non-microbial conditions, of which pancreatitis is the archetype. The similarity in clinical picture is explained by the pathophysiological role of cytokines, host derived peptides released in response to a wide variety of stimuli, which are common to both. The current terminology was defined in the early 1990s and despite recent review remains largely unchanged. This defines sepsis as the association of a panoply of non-specific inflammatory responses with evidence, or suspicion, of a microbial origin. When accompanied by evidence of hypoperfusion or dysfunction of at least one organ system, this becomes "severe sepsis." Finally, where severe sepsis is accompanied by hypotension or need for vasopressors, despite adequate fluid resuscitation, the term "septic shock" applies. Increasing severity correlates with increasing mortality, which rises from 25-30% for severe sepsis up to 40-70% for septic shock. Within this terminology, the archaic term "septicaemia," which persists in the language of the non-specialist and layman, straddles the definitions of sepsis, severe sepsis, and septic shock.

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