Association of Intra-arrest Transport vs Continued On-Scene Resuscitation With Survival to Hospital Discharge Among Patients With Out-of-Hospital Cardiac Arrest

Abstract

Importance: There is wide variability among emergency medical systems (EMS) with respect to transport to hospital during out-of-hospital cardiac arrest (OHCA) resuscitative efforts. The benefit of intra-arrest transport during resuscitation compared with continued on-scene resuscitation is unclear.

Objective: To determine whether intra-arrest transport compared with continued on-scene resuscitation is associated with survival to hospital discharge among patients experiencing OHCA.

Design, setting, and participants: Cohort study of prospectively collected consecutive nontraumatic adult EMS-treated OHCA data from the Resuscitation Outcomes Consortium (ROC) Cardiac Epidemiologic Registry (enrollment, April 2011-June 2015 from 10 North American sites; follow-up until the date of hospital discharge or death [regardless of when either event occurred]). Patients treated with intra-arrest transport (exposed) were matched with patients in refractory arrest (at risk of intra-arrest transport) at that same time (unexposed), using a time-dependent propensity score. Subgroups categorized by initial cardiac rhythm and EMS-witnessed cardiac arrests were analyzed.

Exposures: Intra-arrest transport (transport initiated prior to return of spontaneous circulation), compared with continued on-scene resuscitation.

Main outcomes and measures: The primary outcome was survival to hospital discharge, and the secondary outcome was survival with favorable neurological outcome (modified Rankin scale <3) at hospital discharge.

Results: The full cohort included 43 969 patients with a median age of 67 years (interquartile range, 55-80), 37% were women, 86% of cardiac arrests occurred in a private location, 49% were bystander- or EMS-witnessed, 22% had initial shockable rhythms, 97% were treated by out-of-hospital advanced life support, and 26% underwent intra-arrest transport. Survival to hospital discharge was 3.8% for patients who underwent intra-arrest transport and 12.6% for those who received on-scene resuscitation. In the propensity-matched cohort, which included 27 705 patients, survival to hospital discharge occurred in 4.0% of patients who underwent intra-arrest transport vs 8.5% who received on-scene resuscitation (risk difference, 4.6% [95% CI, 4.0%- 5.1%]). Favorable neurological outcome occurred in 2.9% of patients who underwent intra-arrest transport vs 7.1% who received on-scene resuscitation (risk difference, 4.2% [95% CI, 3.5%-4.9%]). Subgroups of initial shockable and nonshockable rhythms as well as EMS-witnessed and unwitnessed cardiac arrests all had a significant association between intra-arrest transport and lower probability of survival to hospital discharge.

Conclusions and relevance: Among patients experiencing out-of-hospital cardiac arrest, intra-arrest transport to hospital compared with continued on-scene resuscitation was associated with lower probability of survival to hospital discharge. Study findings are limited by potential confounding due to observational design.

Figure 1.. Flow of Participants in a Study of Intra-arrest Transport vs On-Scene Resuscitation in Patients With Out-of-Hospital Cardiac Arrest

EMS indicates emergency medical system. Unmatched on-scene resuscitation patients were matched with the best possible intra-arrest transport patient within 1 caliper. Of the 9406 intra-arrest transport patients in the full matched set, 6025 were matched with 1 on-scene resuscitation patient, 1024 were matched with 2 on-scene resuscitation patients, and the remaining 2357 were matched with 3 or more on-scene resuscitation patients.

Figure 2.. Relationship Between Overall Survival by Study Site and the Proportion of Patients Treated With Intra-arrest Transport Using the Full Study Cohort (N = 43 969)

Study sites are ordered by overall survival, from A to J. Numbers in parentheses indicate the number of patients from each study site; error bars indicate 95% CIs for the proportion of survival at hospital discharge. Box plots display the median (solid line in the box), interquartile range (ends of the box), and range (whiskers) of unadjusted study site proportions for survival and intra-arrest transport. Point locations for E and F are minimally adjusted to avoid overlap.

Figure 3.. Adjusted Analyses Examining the Association of Intra-arrest Transport and Survival Among the Full Propensity-Matched Cohort and Subgroups

The primary outcome for all analyses is survival to hospital discharge, with the exception of the “neurological outcome” subgroup, for which the outcome variable is survival with favorable neurological outcome, defined as Modified Rankin Scale score <3. The P value for interaction is between intra-arrest transport and a subgroup. Time-based epochs include intra-arrest transport patients who were transported during that time interval (measured from the onset of EMS-commenced resuscitation) and the on-scene resuscitation patients whom they were matched to. The right end points are included in the time interval. ALS indicates advanced life support; BLS, basic life support; EMS, emergency medical systems.