P1707Non-business hours and cold exposure independently worsen neurological outcome after out-of-hospital cardiac arrest

Abstract

Abstract Background It has been known that survival rates after out-of-hospital cardiac arrest (OHCA) are lower at night than during the day. It may be explained by diurnal temperature changes. Purpose The purpose of the present study was to test our hypothesis that diurnal variation of the prognosis after OHCA would be independent from the ambient temperature changes. Methods We used the All-Japan Utstein Registry (2005–2010) combined with atmospheric temperature from the Automated Meteorological Data Acquisition System, and enrolled adult OHCA patients who had suffered from a witnessed cardiac arrest and who had been resuscitated. The primary outcome was a favorable neurological outcome one month after OHCA and the secondary outcome was the presence of return of spontaneous circulation (ROSC) before hospital admission. Effects of business vs. non-business hours and ambient temperature on the primary and secondary outcomes were assessed with adjustment for factors that are known to potentially affect OHCA outcomes. Sub-group analysis based on the initial cardiac rhythm (VT/Vf, PEA and Asystole) was also performed. Results Among the 263,750 witnessed OHCA patients, neurological survival and ROSC rates were significantly increased with an adjusted odds ratio (OR) of 1.13 (95% CI 1.08–1.18) and hazard ratio (HR) of 1.06 (95% CI 1.04–1.09) for non-business hours, and OR of 1.11 (95% CI 1.05–1.17) and HR of 1.05 (95% CI 1.02–1.08) for each 20°C increase in temperature. The effects were different between business vs. non-business hours and ambient temperature dependent on the initial cardiac rhythm. Conclusions These findings suggest that both the outdoor temperature and business hours are independent factors for predicting neurological outcomes after OHCA with different characteristics based on the initial cardiac rhythms. Diurnal variability of prognosis after OHCA is likely to be attributable to diurnal variation of medical resources.