Association Between Duration of Resuscitation and Favorable Outcome After Out-of-Hospital Cardiac Arrest: Implications for Prolonging or Terminating Resuscitation

Abstract

Background: Little evidence guides the appropriate duration of resuscitation in out-of-hospital cardiac arrest, and case features justifying longer or shorter durations are ill defined. We estimated the impact of resuscitation duration on the probability of favorable functional outcome in out-of-hospital cardiac arrest using a large, multicenter cohort.

Methods: This was a secondary analysis of a North American, single-blind, multicenter, cluster-randomized, clinical trial (ROC-PRIMED [Resuscitation Outcomes Consortium Prehospital Resuscitation Using an Impedance Valve and Early Versus Delayed]) of consecutive adults with nontraumatic, emergency medical services-treated out-of-hospital cardiac arrest. Primary exposure was duration of resuscitation in minutes (onset of professional resuscitation to return of spontaneous circulation [ROSC] or termination of resuscitation). Primary outcome was survival to hospital discharge with favorable outcome (modified Rankin scale [mRS] score of 0-3). Subjects were additionally classified as survival with unfavorable outcome (mRS score of 4-5), ROSC without survival (mRS score of 6), or without ROSC. Subject accrual was plotted as a function of resuscitation duration, and the dynamic probability of favorable outcome at discharge was estimated for the whole cohort and subgroups. Adjusted logistic regression models tested the association between resuscitation duration and survival with favorable outcome.

Results: The primary cohort included 11 368 subjects (median age, 69 years [interquartile range, 56-81 years]; 7121 men [62.6%]). Of these, 4023 (35.4%) achieved ROSC, 1232 (10.8%) survived to hospital discharge, and 905 (8.0%) had an mRS score of 0 to 3 at discharge. Distribution of cardiopulmonary resuscitation duration differed by outcome (P<0.00001). For cardiopulmonary resuscitation duration up to 37.0 minutes (95% confidence interval, 34.9-40.9 minutes), 99% with an eventual mRS score of 0 to 3 at discharge achieved ROSC. The dynamic probability of an mRS score of 0 to 3 at discharge declined over elapsed resuscitation duration, but subjects with initial shockable cardiac rhythm, witnessed cardiac arrest, and bystander cardiopulmonary resuscitation were more likely to survive with favorable outcome after prolonged efforts (30-40 minutes). After adjustment for prehospital (odds ratio, 0.93; 95% confidence interval, 0.92-0.95) and inpatient (odds ratio, 0.97; 95% confidence interval, 0.95-0.99) covariates, resuscitation duration was associated with survival to discharge with an mRS score of 0 to 3.

Conclusions: Shorter resuscitation duration was associated with likelihood of favorable outcome at hospital discharge. Subjects with favorable case features were more likely to survive prolonged resuscitation up to 47 minutes.

Clinical trial registration: URL: http://clinicaltrials.gov. Unique identifier: NCT00394706.

Keywords: cardiopulmonary resuscitation; heart arrest; resuscitation.

Figure 1

Study cohort and exclusions. CPR: cardiopulmonary resuscitation.

Figure 2

Distribution of CPR duration for all patients with attempted resuscitation, stratified by outcome (p<0.00001). Point estimates and 95% confidence interval for percentiles of CPR duration are provided in the accompanying Table. The upper bound of the 95% confidence interval for the 99^th percentile of CPR duration could not be estimated for mRS 4-5, since it exceeded the values of this dataset. ROSC: return of spontaneous circulation. mRS: modified Rankin scale.

Figure 3

Dynamic probability (black lines) with 95% confidence intervals (gray lines) of survival to hospital discharge with mRS 0-3 as a function of CPR duration, stratified by initial shockable rhythm (A), witnessed cardiac arrest (B), bystander CPR (C), and quartile of elapsed interval from 911 dispatch to onset of professional resuscitation (D). mRS: modified Rankin scale. CPR: cardiopulmonary resuscitation.

Figure 4

Dynamic probability (black lines) with 95% confidence intervals (gray lines) of survival to hospital discharge with mRS 0-3 as a function of CPR duration, for those with (A) and without (B) shockable initial cardiac rhythms, stratified by patient phenotype with different combinations of case features. mRS: modified Rankin scale. CPR: cardiopulmonary resuscitation.