Abstract 56: The Association Between Early Hyperoxemia and Oxygen Exposure with Development of Pulmonary Dysfunction, Survival and Neurological Outcomes After Cardiac Arrest

Abstract

Introduction: Prior studies inconsistently report an association between hyperoxemia and worse outcomes after cardiac arrest (CA), but are methodologically limited. We used a high-resolution CA-specific database to control for cumulative early oxygen exposure, disease-specific covariates and care processes to test if rigorous adjustment would eliminate any association between hyperoxemia and outcomes. We also tested if exposure to higher inspired oxygen (FiO2) was associated with development of lung dysfunction. Methods: We included patients surviving and ventilated for >24 hours after ROSC. To test the association between hyperoxemia and outcomes, we categorized PaO2 hourly for 24h as severe hyperoxemia (>300mmHg), moderate hyperoxemia (101-299mmHg), normoxia (60-100mmHg) or hypoxia (<60mmHg). We controlled for CA-specific covariates and markers of potentially less attentive care (time to first FiO2 wean, number of weans, etc). We used multiple logistic regression to test the association between PaO2 and survival and discharge CPC. To test for development of lung dysfunction, we calculated oxygen exposure as the area under the curve of the FiO2 x hour (FiO2AUC) for each patient over 24h. Our main outcomes in this analysis were change in the respiratory SOFA score (SOFA-R) and change in dynamic lung compliance from baseline to 48h. Results: Of 184 patients overall mortality was 54% and 36% had severe hyperoxemia. The first PaO2:FiO2 ratio was 241±137, and at baseline 85% had pulmonary failure and 55% had cardiovascular failure as assessed by SOFA. Only severe hyperoxemia was independently associated with decreased survival to hospital discharge (adjusted OR 0.83 per hour, P=0.04) and worse discharge CPC. Higher FiO2AUC was not associated with worsened SOFA-R or lung compliance over 48h but was associated with decreased survival to discharge and worse discharge CPC. This was driven by 50% decreased survival in the highest quartile of FiO2AUC (FIO2>80%/24h) compared to other quartiles. Conclusion: Despite rigorous adjustment, severe hyperoxemia was independently associated with decreased survival to hospital discharge and discharge CPC. We did not observe toxicity at lower levels. High FiO2 was not associated with pulmonary toxicity.