Merits of expanding the Utstein case definition for out of hospital cardiac arrest

Abstract

Background

The Utstein population is defined by non-traumatic, bystander-witnessed out-of-hospital cardiac arrest (OHCA) presenting with ventricular fibrillation (VF). It is used to compare resuscitation performance across emergency medical services (EMS) systems. We hypothesized a system-specific survival correlation between the current Utstein population and other VF populations defined by unwitnessed VF OHCA and VF OHCA after EMS arrival (EMS-witnessed). Expanding performance metrics to this more comprehensive population would make the Utstein definition more representative of the actual community burden and response to VF OHCA.

Methods

We performed a cohort investigation of all non-traumatic, VF OHCA in the Cardiac Arrest Registry to Enhance Survival from 1/1/2013-12/31/2018 among EMS agencies that treated > = 100 VF OHCA. We evaluated sample size and survival with the addition of the new VF populations. We used Pearson coefficient to assess whether there was a correlation of agency-specific survival outcomes between the current Utstein population and unwitnessed and EMS-witnessed VF OHCA.

Results

A total of 107 EMS agencies treated 38,836 VF arrests: 22,918 current Utstein, 11,297 unwitnessed VF, and 4621 EMS-witnessed VF OHCA. Overall, survival was 29.8% (11,567/38,836): 33.9% (7774/22,918) among current Utstein, 17.2% (1942/11,297) among unwitnessed VF, and 40.1% (1851/4621) among EMS-witnessed VF. For agency-specific survival outcome, the Pearson correlation was 0.52 between the current Utstein population versus combined unwitnessed and EMS-witnessed groups. For survival with Cerebral Performance Category 1–2, the Pearson correlation was 0.61.

Conclusion

Expanding the Utstein population to include unwitnessed and EMS-witnessed VF OHCA achieves a simpler, more inclusive case definition that minimizes variability in case determination and increases the number of survivors and eligible population by ∼50%, while still achieving a distinguishing metric of system-specific performance.

Introduction

The Utstein case definition for out-of-hospital cardiac arrest (OHCA) was proposed at an international conference in 1990 held in the Utstein Abbey, near Stavanger, Norway.¹ Its purpose was to provide a uniform, structured framework with common definitions and a defined patient population by which OHCA care and outcome could be reported and compared across communities. Originally, the Utstein patient population was defined as persons with OHCA presumed to be of cardiac etiology, whose collapse was witnessed by a bystander, and who presented with an initial arrest rhythm of ventricular fibrillation (VF). Outcomes included admission alive to hospital and survival to hospital discharge. The case definition for inclusion in Utstein was narrow, in the belief that this group was the most likely to respond to available interventions and thus could serve as a barometer of the effectiveness of the community response. This framework was widely adopted and became the primary framework to evaluate and compare the performance of prehospital systems in the management of OHCA. Since first proposed, the Utstein approach has been cited by thousands of scientific publications involving OHCA.

In 2005, the Utstein case definition was broadened from its focus on presumed cardiac etiology to include all medical etiologies, excluding traumatic cardiac arrest.² This change in case definition was driven by concerns over the consistency and reliability of ascribing a VF OHCA to a cardiac cause, given the different approaches and available information sources used to make such a determination across communities. By avoiding the potential variability and bias related to classifying cardiac etiology, this modification provided a more straightforward classification across communities. The change also modestly expanded the Utstein population by approximately 5%, providing a larger base among whom to assess system metrics and outcome.

Despite this refinement, inconsistencies in case determination for Utstein classification persist. For example, classification of witness status varies across systems, with some variability likely due to subjective methods in its assessment rather than true differences in whether or how the OHCA was initially recognized.3, 4 What if the Utstein eligibility were expanded to encompass the totality of patients presenting with non-traumatic OHCA due to VF regardless of witness circumstance? Such a change might further simplify classification and produce a more consistent definition of the population while still serving to measure differences in system performance. Moreover, the inclusion of all non-traumatic VF regardless of witness status (like that of all medical etiologies of cardiac arrest) would increase the population under evaluation and may provide a more robust and representative assessment of a community’s resuscitation performance in the context of the total burden of VF OHCA.

The purpose of this study was to evaluate and compare outcomes from OHCA due to VF across a broad spectrum of communities using the current Utstein patient cohort and an expanded cohort to include unwitnessed VF OHCA and EMS-witnessed VF OHCA. We hypothesized there would be a system (EMS agency)-specific correlation in outcome between these VF population groups so as to justify a meaningful expansion of the Utstein criteria that more comprehensively measures a community’s burden and response to VF OHCA cardiac arrest.