Admission PaO2 and Mortality Among Pediatric ICU Patients and Critically Ill Subgroups
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INTRODUCTION: Studies analyzing the association between hyperoxia and mortality in critically ill pediatric patients and those admitted after cardiac arrest are conflicting and limited by small sample sizes. The aim of this study is to evaluate the association between PaO2 on admission to the pediatric ICU and mortality in a heterogeneous, multicenter cohort and among subgroups of critically ill patients.
METHODS: A retrospective cohort study was conducted using data from Virtual Pediatric Systems (VPS) database. VPS is a clinical pediatric critical care database with over 135 participating hospitals in North America. All VPS patients 18 years or younger admitted between 2015 and 2019 with an admission PaO2 were included. Cardiac patients and those admitted to a cardiac ICU were excluded. Patients were stratified into 50-point PaO2 bins based on admission PaO2. Modified PIM3 scores were calculated for all patients by excluding the PaO2 term from the PIM3 equation. ICD-9, ICD-10 codes, VPS admission data and PRISM3 results were used to classify patients into the following diagnostic subgroups: trauma, head trauma, sepsis, renal failure, hemorrhagic shock, and those admitted after cardiac arrest (post-arrest).
RESULTS: 13,071 patient encounters were included with an overall mortality of 13.5%. The relationship between admission PaO2 and mortality demonstrated a U-shaped quadratic curve, with higher mortality seen in hypoxic (PaO2 < 50 mm Hg, mortality 28.5%) and hyperoxic (PaO2 > 300 mm Hg, mortality 25.4%) patients. This relationship persisted after adjustment for illness severity using modified PIM3 scores. Similarly, a quadratic relationship was demonstrated among trauma, head trauma, sepsis, renal failure and hemorrhagic shock patients. However, among the 1,500 post-arrest patients, there was no correlation between admission PaO2 and mortality, even after controlling for modified PIM3 scores.
CONCLUSIONS: In a large multicenter pediatric cohort, admission PaO2 demonstrates a clear U-shaped quadratic relationship with mortality. The persistence of this quadratic relationship in some but not all diagnostic subgroups suggests the pathophysiology of certain disease states may modify the hyperoxia effect. Further studies are necessary to determine whether this association is causal or merely incidental.