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Abstract

Introduction: Initial studies have demonstrated an association between hyperoxia and worse outcomes in patients experiencing cardiac arrest. However, more recent data in a population with higher use of hypothermia failed to confirm this association, suggesting hypothermia may attenuate the detrimental effects of hyperoxia. Hypothesis: Higher levels of partial pressure of arterial oxygen (Pa02) are associated with increased in-hospital mortality and poor neurologic status at hospital discharge in patients treated with mild therapeutic hypothermia after sudden cardiac arrest. Methods: We conducted a retrospective analysis of a prospectively gathered cohort of 173 consecutive patients treated with 24 hours of therapeutic hypothermia (TH) following sudden cardiac arrest. Maximum Pa02 during TH was collected from the medical record. Primary outcome was survival to hospital discharge. Secondary outcome was good neurologic function at hospital discharge as defined by a Cerebral Performance Category of 1 or 2. A multivariate logistic regression was used to examine the effect of maximum Pa02 on survival and neurologic outcome. Results: Three patients were excluded due to missing data. Of 170 patients, 77 (45.3%) survived to hospital discharge. Survivors had a significantly lower maximum PaO2 (198mmHg, IQR 152.5-282) measured in the first 24 hours following cardiac arrest compared to nonsurvivors (254mmHg, IQR 172-363; p = 0.022). A multivariable analysis which adjusted for age, time to return of spontaneous circulation, the presence of shock, bystander CPR and initial rhythm showed that higher Pa02s were significantly associated with increased in-hospital mortality (OR 1.439, 95% CI 1.028-2.015; p = 0.034) and poor neurologic status and hospital discharge (OR 1.485, 95% CI 1.032-2.136; p = 0.033). Conclusions: Increased levels of Pa02 during the first 24 hours of TH after sudden cardiac arrest are significantly and independently associated with higher in-hospital mortality and poor neurologic status on hospital discharge.