Association Between Arterial Hyperoxia Following Resuscitation From Cardiac Arrest and In-Hospital Mortality

CONTEXT: Laboratory investigations suggest that exposure to hyperoxia after resuscitation from cardiac arrest may worsen anoxic brain injury; however, clinical data are lacking. OBJECTIVE: To test the hypothesis that postresuscitation hyperoxia is associated with increased mortality. DESIGN, SETTING, AND PATIENTS: Multicenter cohort study using the Project IMPACT critical care database of intensive care units (ICUs) at 120 US hospitals between 2001 and 2005. Patient inclusion criteria were age older than 17 years, nontraumatic cardiac arrest, cardiopulmonary resuscitation within 24 hours prior to ICU arrival, and arterial blood gas analysis performed within 24 hours following ICU arrival. Patients were divided into 3 groups defined a priori based on PaO (2) on the first arterial blood gas values obtained in the ICU. Hyperoxia was defined as PaO (2) of 300 mm Hg or greater; hypoxia, PaO (2) of less than 60 mm Hg (or ratio of PaO (2) to fraction of inspired oxygen <300) ; and normoxia, not classified as hyperoxia or hypoxia. MAIN OUTCOME MEASURE: In-hospital mortality. RESULTS: Of 6326 patients, 1156 had hyperoxia (18%), 3999 had hypoxia (63%), and 1171 had normoxia (19%). The hyperoxia group had significantly higher in-hospital mortality (732/1156 63%; 95% confidence interval CI, 60%-66%) compared with the normoxia group (532/1171 45%; 95% CI, 43%-48%; proportion difference, 18% 95% CI, 14%-22%) and the hypoxia group (2297/3999 57%; 95% CI, 56%-59%; proportion difference, 6% 95% CI, 3%-9%). In a model controlling for potential confounders (eg, age, preadmission functional status, comorbid conditions, vital signs, and other physiological indices), hyperoxia exposure had an odds ratio for death of 1. 8 (95% CI, 1. 5-2. 2). CONCLUSION: Among patients admitted to the ICU following resuscitation from cardiac arrest, arterial hyperoxia was independently associated with increased in-hospital mortality compared with either hypoxia or normoxia.