Association of prior beta-blocker treatment and outcome in patients with out-of-hospital cardiac arrest

Background The impact of chronic beta-blocker (BB) therapy on outcomes after out-of-hospital cardiac arrest (OHCA) remains uncertain. Previous studies relied on prescription data rather than verified drug exposure. We investigated whether measured BB plasma concentrations on admission are associated with resuscitation outcomes and in-hospital mortality. Purpose To evaluate the association between admission BB plasma concentrations and defibrillation requirements, initial rhythm and survival in patients with OHCA. Methods We enrolled consecutive OHCA patients with return of spontaneous circulation (ROSC) in a prospective resuscitation-registry. BB plasma concentrations were measured upon admission and analyzed in relation to the number of defibrillations required to achieve ROSC, initial cardiac rhythm and in-hospital mortality. Multivariable regression adjusted for age, sex, bystander CPR, and initial shockable rhythm was used to assess associations. Models for in-hospital death also included eGFR and admission lactate. Results Among 207 enrolled patients (median age 68 years, 71% male, 45% shockable rhythm), 65 (31.4%) had detectable BB plasma concentrations. Detectable BB concentrations, irrespective of β1-selectivity, were not associated with the likelihood of an initial shockable rhythm (adjusted odds ratio [OR] 0.99 [95% confidence interval [CI], 0.52-1.91]; P=0.99; Figure 1), number of defibrillations (adjusted incidence rate ratio 0.93 [95% CI 0.63-1.37], P=0.72) or doses of epinephrine (adjusted mean 7.4 vs. 6.7 mg, P=0.29) and amiodarone (adjusted mean 99.3 vs. 93.9 mg, P=0.83) administered to achieve ROSC. When analyzed as a continuous variable, BB concentration on admission was not associated with in-hospital death (adjusted OR 0.85 [95% CI 0.67-1.08]; P=0.18). However, patients with plasma concentrations above the median had lower odds of death compared to those with undetectable levels or those below the median (adjusted OR 0.36 [95% CI 0.13-0.96]; P=0.042, Figure 2). Conclusion In OHCA patients with ROSC, detectable BB plasma concentrations on admission were not associated with defibrillation requirements or initial cardiac rhythm. While any detectable BB level was not linked to overall mortality, levels above the median were associated with lower odds of death.