High cumulative oxygen levels are associated with improved survival of children treated with mild therapeutic hypothermia after cardiac arrest

Abstract

Aim: The aim of this study was to analyze the relationship between the partial pressure of arterial oxygen (PaO2) and in-hospital (IH) mortality in children after cardiac arrest (CA) using the conventional cutoff analysis, which was compared with the cumulative analysis, a new method in PaO2 analysis. Additionally, we analyzed this relationship for children with and without mild therapeutic hypothermia (MTH; 32-34 °C).

Methods: This observational cohort study included all children (aged >28 days) with CA and return of spontaneous circulation (ROSC) between 2002 and 2011. The first research question was the association between PaO2 and IH mortality after ROSC. This was analyzed for three hyperoxia cutoff values, and for three time intervals using the cumulative PaO2 determined with the area under the curve (AUC). For the second research question, these analyses were repeated for children with and without MTH.

Results: Of the 200 patients included (median age 2.6 years), 84 (42%) survived to hospital discharge. Fifty-eight children (29%) were treated with MTH. With the cutoff analysis and the AUC analysis we found no relationship between PaO2 and IH mortality. However, analysis of the MTH-group showed a lower IH mortality in children with high cumulative PaO2 levels on two of the three time intervals. Multivariable analysis showed significantly higher odds of survival (0.643 (95% confidence interval (CI) 0.424-0.976), 0.554 (95% CI 0.335-0.916)).

Conclusions: Cumulative PaO2 analysis showed that the IH mortality is significantly lower in MTH-treated children with high PaO2 levels. The effects of cumulative PaO2 on the outcome need to be studied further, and this will help us to achieve individualized goal-directed therapy.

Keywords: Area under curve; Heart arrest; Hyperoxia; Hypothermia; Induced; Pediatrics.