Admission PaO2 and Mortality in Critically Ill Children: A Cohort Study and Systematic Review

To describe the relationship between PaO2 at intensive care admission and mortality in critically ill children and to review systematically the literature describing this relationship.

Cohort study: A review of consecutive tertiary pediatric intensive care admissions (January 2004 to December 2014) in a single center. The relationship between admission Pao2 and crude and standardized mortality was explored using nonlinear regression. Systematic review: A search of MEDLINE (1950 to January 2015), EMBASE (1980 to January 2015), Cochrane and Database of Abstracts of Reviews of Effects databases was undertaken using the following terms: "hyperoxia," "hypoxia," "critically ill children," "pediatric intensive care," "mortality," and/or "survival."

Tertiary PICU.

Patients younger than 18 years of age.

The association of hyperoxia (PaO2, > 300 torr [40 kPa]) and hypoxia (PaO2, < 60 torr [8 kPa] or peripheral oxygen saturations, < 90%) to mortality in critically ill children was explored.

Cohort study: Of 14,321 admissions, 7,410 children had recorded PaO2 and FIO2 at admission. Crude mortality was 7.4% (555/7,410). This varied with admission PaO2 from 15.4% (204/1,324) in the hypoxia group (< 8 kPa) to 5.3% (287/5,385) with normoxia and 9.1% (64/701) in the hyperoxic group (> 40 kPa). Nonlinear regression displayed a "U-shaped" relationship between PaO2 and crude and case-mix adjusted mortality. Systematic review: Fourteen studies and one conference abstract were eligible for inclusion. Eleven studies (n = 5,280) relate to hypoxia with combined odds ratio for death, of 3.13 (95% CI, 1.79-5.48; p < 0.001) compared to normoxia. Six studies (n = 2,012) relate to hyperoxia and suggest no effect on mortality compared to normoxia (odds ratio, 1.15; 95% CI, 0.42-3.17; p = 0.77).

Hypoxia at admission is associated with increased mortality in critically ill children, whereas the association with hyperoxia is less clear. The cohort study demonstrated a U-shaped association between admission PaO2 and mortality. Further examination is needed to explore the effect of hyperoxia upon mortality prediction accuracy.