Community-Acquired Pneumonia Management Based on the PIRO System. A New Therapeutic Paradigm

In 2001, an International Sepsis Defi nition Conference [1] agreed to assess the strengths and weaknesses of the criteria for sepsis established in 1991 [2], and, if necessary, to update them. The update was necessary because the current understanding of host response was very simplistic, and the concepts of sepsis, severe sepsis, and septic shock were very robust for daily clinical practice. Moreover, the signs and symptoms of sepsis are more varied than the initial criteria. A staging system had to be developed that would characterize the progression of sepsis. A new system was proposed based on four features — predisposition, infection, response, and organ dysfunction — the PIRO system [3–6].

This new conceptual framework for understanding sepsis, called the PIRO concept, is a classifi cation scheme that can stratify patients based on their predisposing conditions, the nature and extend of the insult, the nature and magnitude of the host response, and the degree of the concomitant organ dysfunction. Conceptually, it was modeled on the TNM classifi cation, which has been successfully used to defi ne prognostic indicators in clinical oncology. PIRO was introduced as a hypothesis-generating model for future research, but its practical applications were limited. In this chapter we propose a new paradigm for the management of CAP based on the PIRO system (Table 1).