Lidocaine Versus Amiodarone in Patients With Shockable Out-of-Hospital Cardiac Arrest: A Target Trial Emulation

Amiodarone or lidocaine are recommended for the treatment of shockable out-of-hospital cardiac arrest (OHCA). Previous comparisons between the two antiarrhythmic drugs were inconclusive.

This analysis included data from the Resuscitation Outcomes Consortium Cardiac Epidemiologic Registry 3 (2011-2015). A target trial framework was used to overcome confounding inherent in observational comparisons.

Data from patients with OHCA were prospectively collected by emergency medical services (EMS) at multiple North American sites.

Adults with nontraumatic OHCA and an initial shockable rhythm who received at least three defibrillation attempts were included. Time zero was defined as first antiarrhythmic drug administration, at which eligibility criteria had to be met.

Two antiarrhythmic treatment strategies were compared: lidocaine vs. amiodarone.

The primary outcome was survival to hospital discharge. The key secondary outcome was favorable neurologic outcome at discharge (modified Rankin scale score of 3 or less). Group differences were adjusted using inverse probability weighting (key covariates: age, sex, location of OHCA, witness status, bystander resuscitation, automated external defibrillator shock, elapsed time from call to advanced life support arrival/first EMS shock/advanced airway, intraosseous access) and a multiple logistic regression model. Of 2451 patients included, 987 received lidocaine and 1464 received amiodarone. The adjusted percentage point difference in survival to hospital discharge was 2.8% favoring lidocaine (95% CI, -0.6 to 6.2); the estimated survival probabilities were 26.2% (275/987) with lidocaine and 23.5% (329/1464) with amiodarone. No difference was observed in the estimated probability of favorable neurologic outcome at discharge between the lidocaine group (17.7%) and the amiodarone group (16.2%) (adjusted difference, 1.5%; 95% CI, -1.5 to 4.5).

No statistically significant difference in survival or favorable neurologic outcome was observed between lidocaine and amiodarone; however, the wide CIs cannot exclude a clinically meaningful benefit for lidocaine. These findings are consistent with randomized controlled trials, but residual confounding cannot be excluded.