The 2024 Phoenix Sepsis Score Criteria: Part 1, the Evolution in Definition of Sepsis and Septic Shock

The evolution in understanding sepsis signs and symptoms has been ongoing since the term was first introduced more than 2000 years ago. In adults, there have been three sepsis definition conferences focused on developing operational criteria for sepsis in 1991, 2001, and 2016 (1–3). While the first two iterations were based on criteria for the systemic inflammatory response syndrome (SIRS) with phenomenological characterization of severity using an array of expert-based criteria, the 2016 consensus conference (commonly known as Sepsis-3) defined sepsis as life-threatening organ dysfunction due to a dysregulated host response to infection and used the Sequential Organ Failure Assessment score to operationalize it (3). Sepsis-3 not only departed from the SIRS-based criteria, but it set a new standard for the development of objective, data-driven criteria for sepsis. In pediatrics, progress in defining sepsis has been slower. In 2005, using the standard methodology of the time, an international panel of 20 experts modified the 2001 adult consensus definition of sepsis based on SIRS by incorporating age-appropriate physiologic variables and other expert-based criteria for pediatric organ dysfunction to define severe sepsis and septic shock (4). Nearly 20 years of progress into pediatric sepsis research and care has led to a greater understanding of sepsis epidemiology and pathophysiology. However, by 2018, SIRS in children, as in adults, was considered an adaptive host response to infection (5), rather than a maladaptive pathologic state. In this series of five Editorial Commentaries for Pediatric Critical Care Medicine (6), we write about an original article that was published in the Journal of the American Medical Association (JAMA) in February 2024, in which we presented the Phoenix criteria for sepsis and septic shock in children (7). Here, in “Part 1,” as representatives from the Society of Critical Care Medicine (SCCM) Pediatric Sepsis Definitions Taskforce, we provide the overarching commentary—additional to what has already appeared in JAMA—on the evolution toward the 2024 Phoenix definitions and operational criteria for sepsis and septic shock in children. The other four Editorial Commentaries in this collection for PCCM focus on aspects of “using” the Phoenix criteria that generated important discussion during development, since publication in JAMA, and at the 2024 SCCM Critical Care Congress (see https://www.youtube.com/watch?v=qjfhiMOV7M0). Figure 1 provides the framework of the development of the Phoenix criteria, and the accompanying commentaries discuss aspects deserving comment, including: “Part 2,” using “interventions” as criteria for sepsis (8); “Part 3,” using “stages of sepsis” (9); “Part 4,” using “world orientated” criteria for sepsis (10); and “Part 5,” using “parsimony” in sepsis definition (11).