Divergent PICU lengths of stay despite identical phoenix sepsis scores: heterogeneity in pediatric sepsis outcomes according to system involvement profiles.

Objective: This study examined how different subsystem involvement patterns in the Phoenix Sepsis Score relate to PICU length of stay among children with sepsis, focusing on patients with identical total scores, and explored clinical factors associated with these differences. Methods: We retrospectively included 107 children with sepsis admitted to a single PICU (2024-2025). Patients were grouped by the number of affected Phoenix subsystems (respiratory, coagulation, circulatory, neurological): single-system ( Results: Respiratory and/or coagulation involvement accounted for 89.7% (96/107) of cases, with the respiratory-coagulation combination being most frequent (55.1%). The multi-system group had the highest total scores, lactate levels, and mortality (37.5%, all Conclusions: In septic children with the same Phoenix total score, different system involvement patterns yield substantially different outcomes and resource use. A respiratory subsystem score ≥2 signals high risk of prolonged PICU stay, largely explained by the greater need for invasive ventilation. The total Phoenix score alone is insufficient for resource planning; the respiratory component may provide additional information beyond the total score.