The PIRO concept: P is for predisposition

[Derek C Angus] As you know, in 1991 the American College of Chest Physicians and the Society of Critical Care Medicine convened a consensus panel to come up with some operational definitions for sick septic patients that would, in particular, facilitate the standardized enrolment of patients into clinical trials. At that time it was proposed to be 'infection' plus two or three out of the four systemic inflammatory response syndrome (SIRS) criteria that were believed to be related to the infection. If you also had acute organ dysfunction, it was believed that you had severe sepsis. That was published in 1992 and served as the basis for enrolment entry criteria into about 30 large randomized, controlled trials, but it rarely did much in terms of patient management – people were not necessarily using it to care for patients.In December 2001, the American College of Chest Physicians, the Society of Critical Care Medicine, the European Society of Intensive Care Medicine, and several other sponsoring organizations – the American Thoracic Society – decided to convene another conference with at least one of the purposes being to explore how people felt about the robustness of the existing severe sepsis criteria. During that meeting SIRS came under heavy attack, and it was largely disbanded as not being very useful because the criteria identified lots of patients who were not sick and because there were sick patients who did not necessarily have SIRS.At the same time, during that meeting there was considerable discussion about a new concept that had been proposed predominantly by John Marshall, from Toronto. He suggested that we could think about severe sepsis in a way that might be analogous to cancer – where you stage cancers by tumors/nodes/metastases, the TNM classification, and perhaps you can consider thinking of sepsis in the same way.This gave birth to the concept of PIRO, which is thinking about severe septic patients across four domains. P for 'predisposition', pr