Hyperoxia Early After Hospital Admission in Comatose Patients with Non-Traumatic Out-of-Hospital Cardiac Arrest

BACKGROUND The clinical effect of hyperoxia in patients with non-traumatic out-of-hospital cardiac arrest (OHCA) remains uncertain. We therefore initiated this study to find out whether there is an association between survival and hyperoxia early after return of spontaneous circulation (ROSC) in OHCA patients admitted to our hospital. MATERIAL AND METHODS All OHCA patients admitted to our hospital between 1 January 2008 and 30 June 2015 were identified by analysis of our central admission register. Data from individual patients were collected from patient health records and anonymously stored on a central database. RESULTS Altogether, there were 280 OHCA patients admitted to our hospital between 1 January 2008 and 30 June 2015, including 35 patients (12.5%) with hyperoxia and 99 patients (35.4%) with normoxia. Comparison of these 2 groups showed lower pH values in OHCA patients admitted with normoxia compared to those with hyperoxia (7.10±0.18 vs. 7.21±0.17; p=0.001) but similar rates of initial lactate (7.92±3.87 mmol/l vs. 11.14±16.40 mmol/l; p=0.072). Survival rates differed between both groups (34.4% vs. 54.3%; p=0.038) with better survival rates in OHCA patients with hyperoxia at hospital admission. CONCLUSIONS Currently, different criteria are used to define hyperoxia following OHCA, but if the negative effects of hyperoxia in OHCA patients are a cumulative effect over time, hyperoxia < 60 min after hospital admission as investigated in this study would be equivalent to a short period of hyperoxia. It may be that the positive effect of buffering metabolic acidosis early after cardiac arrest maintains the negative effects of hyperoxia in general.