Effect of Epinephrine Administration on Neurological Outcomes in Patients with Out-of-Hospital Cardiac Arrest Receiving Bystander Cardiopulmonary Resuscitation

Objectives To examine whether bystander cardiopulmonary resuscitation (BCPR) is associated with the time-dependent effects of epinephrine administration on neurological outcomes in out-of-hospital cardiac arrest (OHCA) patients.Methods We conducted a retrospective cohort study using the All-Japan Utstein Registry from 2015 to 2019. Witnessed OHCA cases of presumed cardiac origin in patients aged 15–116 years who received epinephrine were included. Patients were stratified by initial cardiac rhythm (shockable or non-shockable) and categorized by time to epinephrine administration into early (0–19 min), intermediate (20–26 min), and late (27–56 min) groups. Multivariable logistic regression was performed to assess the association between BCPR and favorable neurological outcomes (CPC 1–2) at one month, adjusting for potential confounders. An interaction term between BCPR and epinephrine timing was included in the models to evaluate whether BCPR modified the time-dependent association between epinephrine administration and outcomes.Results Among 31,670 patients, 18.5% had shockable and 81.5% had non-shockable rhythms. In the shockable cohort, BCPR was significantly associated with favorable neurological outcomes overall (AOR 1.86, 95% CI 1.41–2.44), particularly in the early (AOR 1.75, 95% CI 1.30–2.34) and intermediate (AOR 2.84, 95% CI 1.75–4.61) groups. No significant interaction between BCPR and epinephrine timing was observed in this cohort. In the non-shockable cohort, BCPR was not independently associated with favorable outcomes across any time category. However, the interaction analysis indicated that the time-dependent effect of epinephrine differed slightly according to BCPR status (AOR for interaction 1.03, 95% CI 1.00–1.05, p = 0.03).Conclusions In shockable OHCA, BCPR was associated with improved outcomes, but no significant interaction with epinephrine timing was observed. In non-shockable OHCA, BCPR itself was not associated with outcomes, while the interaction analysis suggested a possible difference by BCPR status, indicating that the functional role of BCPR may vary depending on the initial rhythm.