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

Aim: The aim of this study was to analyze the relationship between the partial pressure of arterial oxygen (PaO<inf>2</inf>) 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 PaO<inf>2</inf> 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 PaO<inf>2</inf> and IH mortality after ROSC. This was analyzed for three hyperoxia cutoff values, and for three time intervals using the cumulative PaO<inf>2</inf> 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 PaO<inf>2</inf> and IH mortality. However, analysis of the MTH-group showed a lower IH mortality in children with high cumulative PaO<inf>2</inf> 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 PaO<inf>2</inf> analysis showed that the IH mortality is significantly lower in MTH-treated children with high PaO<inf>2</inf> levels. The effects of cumulative PaO<inf>2</inf> on the outcome need to be studied further, and this will help us to achieve individualized goal-directed therapy.

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