Epidemiology and outcomes of anaphylaxis-associated out-of-hospital cardiac arrest

Background: Understanding the epidemiological characteristics of anaphylaxis-associated out-of-hospital cardiac arrest (OHCA) is the first step toward developing preventative strategies and optimizing care systems. We aimed to describe and compare epidemiological features and clinical outcomes among patients with anaphylaxis-associated OHCAs according to causative agent groups. Methods: We identified emergency medical service (EMS)-treated anaphylaxis-associated OHCA patients from a nationwide OHCA registry between 2008 and 2015. We compared epidemiological characteristics and outcomes according to causal agents (a natural agents group and an iatrogenic agents group) and evaluated temporal variability in incidence. Multivariate logistic regression analysis was performed to compare survival to discharge between causative agent groups. Results: During the study period (8 years), the total number of anaphylaxis-associated OHCAs was 233. A total of 224 eligible cases were included in the analysis. There were 192 patients (85.6%) in the natural agents group and 32 patients (14.3%) in the iatrogenic agents group. There was significant diurnal and seasonal variability in the frequency of anaphylaxis-associated OHCAs (p values<0.01 for both), with the highest incidences occurring during the day (7:01 am to 3 pm; 64.6%) and in summer (June to August, 48.7%). Compared with the natural agents group, the adjusted odds ratio (AOR) for survival to discharge in the iatrogenic agents group was statistically insignificant (AOR 3.61, 95% CI 0.86 to 15.06). Conclusion: The incidence of anaphylaxis-associated OHCA is considerably low, and significant temporal variability, with a peak during the day and in summer, is evident. Anaphylaxis-associated OHCA is more common by natural agents than by iatrogenic agents, but no difference in the survival-to-discharge rate is evident.