Importance: A high Pao2, termed hyperoxemia, is postulated to have deleterious health outcomes. To date, the association between hyperoxemia during the ongoing management of critical illness and mortality has been incompletely evaluated in children. Objective: To examine whether severe hyperoxemia events are associated with mortality among patients admitted to a pediatric intensive care unit (PICU). Design, Setting, and Participants: A retrospective cohort study was conducted over a 10-year period (January 1, 2009, to December 31, 2018); all 23719 PICU encounters at a quaternary children's hospital with a documented arterial blood gas measurement were evaluated. Exposures: Severe hyperoxemia, defined as Pao2 level greater than or equal to 300 mm Hg (40 kPa). Main Outcomes and Measures: The highest Pao2 values during hospitalization were dichotomized according to the definition of severe hyperoxemia and assessed for association with in-hospital mortality using logistic regression models incorporating a calibrated measure of multiple organ dysfunction, extracorporeal life support, and the total number of arterial blood gas measurements obtained during an encounter. Results: Of 23719 PICU encounters during the inclusion period, 6250 patients (13 422 [56.6%] boys; mean [SD] age, 7.5 [6.6] years) had at least 1 measured Pao2 value. Severe hyperoxemia was independently associated with in-hospital mortality (adjusted odds ratio [aOR], 1.78; 95% CI, 1.36-2.33; P <.001). Increasing odds of in-hospital mortality were observed with 1 (aOR, 1.47; 95% CI, 1.05-2.08; P =.03), 2 (aOR, 2.01; 95% CI, 1.27-3.18; P =.002), and 3 or more (aOR, 2.53; 95% CI, 1.62-3.94; P <.001) severely hyperoxemic Pao2 values obtained greater than or equal to 3 hours apart from one another compared with encounters without hyperoxemia. A sensitivity analysis examining the hypothetical outcomes of residual confounding indicated that an unmeasured binary confounder with an aOR of 2 would have to be present in 37% of the encounters with severe hyperoxemia and 0% of the remaining cohort to fail to reject the null hypothesis (aOR of severe hyperoxemia, 1.31; 95% CI, 0.99-1.72). Conclusions and Relevance: Greater numbers of severe hyperoxemia events appeared to be associated with increased mortality in this large, diverse cohort of critically ill children, supporting a possible exposure-response association between severe hyperoxemia and outcome in this population. Although further prospective evaluation appears to be warranted, this study's findings suggest that guidelines for ongoing management of critically ill children should take into consideration the possible detrimental effects of severe hyperoxemia..
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