Early oxygenation and ventilation measurements after pediatric cardiac arrest: lack of association with outcome.

Cardiac arrest (CA) affects approximately eight per 100,000 children in North America annually and causes high mortality and morbidity (1). Out-of-hospital (OH) CA has reported survival to hospital discharge of 2% to 12%, with intact neurological function in only 2% to 4% (1–3). In-hospital (IH) CA has slightly better outcomes with reported survival of approximately 25% and favorable neurological outcome in approximately 18% (4, 5). Treatment after CA is largely supportive and directed toward minimizing end-organ injury. Aside from rapid, effective cardiopulmonary resuscitation (CPR) and application of extracorporeal membrane oxygenation (ECMO) in select populations, no specific therapy has been shown to improve survival or outcomes after CA in children. Supplemental oxygen therapy remains central to care during and after resuscitation. An association between hypoxia and poor outcome after CA has long been accepted. However, more recently, concerns about potentially detrimental effects of hyperoxia have been raised. Neonatal resuscitation reports show worse long-term outcomes with greater inspired concentrations of oxygen and higher oxygen saturations during resuscitation (6, 7). Similarly, some adult studies link hyperoxia with poorer outcomes (8, 9), although others do not (10). The 2010 American Heart Association (AHA) Neonatal Resuscitation Guidelines recommend beginning resuscitation with room air for term infants (or a blended mixture of oxygen and air for preterm infants) with subsequent titration of inspired oxygen fraction based on pulse oximetry values (11). Similarly, the 2010 AHA Adult Advanced Cardiac Life Support Guidelines recommend initial resuscitation with 100% oxygen and then titration of inspired oxygen fraction after return of circulation (ROC) to target oxygen saturation greater than or equal to 94% (12, 13). Although investigations of hyperoxia and outcomes after CA in children are lacking, the 2010 AHA Pediatric Advanced Life Support Guidelines similarly recommend initial resuscitation with 100% oxygen and consideration of titrating oxygen delivery after ROC to achieve oxygen saturation greater than or equal to 94% (14). Ventilatory support, another mainstay of resuscitation and supportive care, has also been linked with altered outcomes after CA. Hyperventilation reduces cerebral blood flow and is associated with hypotension during resuscitation (15). The 2010 AHA Adult Advanced Cardiac Life Support and Post-Cardiac Arrest Care Guidelines advocate avoiding hypocarbia (12, 13). Similarly, the 2010 AHA Pediatric Advanced Life Support Guidelines state that hyperventilation has no benefit and may be harmful (14). Reports of hyperventilation after CA in children are lacking; however, hyperventilation has been associated with adverse outcomes in children after stroke or traumatic brain injury (16–18) and in neonates after resuscitation from birth asphyxia (19). In this study, we explore oxygenation and ventilation status early after CA in infants and children. Our primary hypothesis is that hyperoxia is common and associated with worse outcome. To test this hypothesis, we conduct a retrospective cohort study involving children who suffered CA yet survived for at least 20 mins after ROC.