Research paper
Surviving out-of-hospital cardiac arrest: The important role of bystander interventions

https://doi.org/10.1016/j.auec.2019.12.003Get rights and content

Abstract

Background

Substantial variations exist in relation to the characteristics and outcomes of out-of-hospital cardiac arrest (OHCA). As such, an understanding of region-specific factors is essential for informing strategies to improve OHCA survival.

Methods

Analysis of a large state-wide OHCA database of the Queensland Ambulance Service, Australia. Adult patients, attended by paramedics between January 2000 and December 2018 for OHCA of medical origin, where the arrest was not witnessed by paramedics, and resuscitation was attempted, were included. Factors associated with survival were investigated. The number needed to treat (NNT) for bystander interventions was estimated.

Results

Across a total of 23,510 patients, event survival, survival to discharge and 30-day survival was 22.6%, 11.9% and 11.5%, respectively. The corresponding figures for the Utstein patient group (initial shockable rhythm, bystander-witnessed) were 38.9%, 27.2% and 26.3%, respectively. Bystander cardiopulmonary resuscitation (CPR) and defibrillation substantially improved the likelihood of survival. The NNT for bystander CPR was 41, 63 and 64 for event survival, survival to discharge, and 30-day survival, respectively. The NNT for bystander defibrillation for these survival outcomes was 10, 14 and 14, respectively.

Conclusions

Bystander interventions are critical for OHCA survival. Effort should be invested in strategies to improve the uptake of these interventions.

Introduction

Out-of-hospital cardiac arrest (OHCA) is a public health concern in Australia, with approximately 22,000 cases attended by paramedics every year [1,2]. Despite advances in emergency medicine and resuscitation technology, survival from OHCA remains very low [3]. The outcomes after OHCA are highly time-dependent; accordingly, early interventions are crucial [4]. The chain-of-survival strategy for OHCA treatment emphasises a system-of-care approach, in which bystander-initiated interventions (bystander cardiopulmonary resuscitation [CPR], bystander defibrillation) prior to paramedic arrival are pivotal to improving patient outcomes [3,5]. Despite the proven benefits and substantial efforts to improve the rate of bystander interventions, less than half of OHCA patients globally receive bystander CPR, and less than 2% receive bystander defibrillation [6,7].

Although the reported survival rate is consistently low, previous studies have found significant variations in survival outcomes across countries and regions [1,8,9]. Such variations reflect differences in regional circumstances, patient characteristics, and clinical practices [10]. As such, policies and practice protocols need to reflect upon regional characteristics. An understanding of region-specific patient characteristics, outcomes and determinants of outcomes is critical for informing strategies to improve survival from OHCA in the region.

This present study aimed to investigate patient characteristics and survival from OHCA in the state of Queensland, Australia, using data from a large prospective, state-wide, population-based database. Factors associated with survival were also investigated, with a focus on bystander interventions. Furthermore, the average number of patients needed to receive a bystander intervention to save one life (i.e. number needed to treat) was estimated.

Section snippets

Study setting

The Queensland Ambulance Service (QAS) is a single, state-wide, government-funded emergency ambulance service that serves a population of approximately five million people geographically dispersed over 1.7 million square kilometres across the state of Queensland, Australia [11]. Relative to other Australian states, Queensland has a high proportion of its population residing outside major cities, with 38% of Queenslanders living in regional or remote areas (compared to 23–27% in other states) [11

Patient characteristics and outcomes

Between January 2000 and December 2018, the database captured a total of 79,949 OHCA patients; of these, 23,510 met the study inclusion criteria (Fig. 1). The majority (76.4%) of arrests occurred in private residential. Table 1 shows the characteristics and overall survival outcomes of the included patients. For all patients, event survival, survival to hospital discharge, and survival to 30-days were 22.6%, 11.9% and 11.5%, respectively. The corresponding figures for the Utstein patient group

Discussion

We conducted an analysis of a large prospective, state-wide, population-based database of OHCA patients. Our survival to hospital discharge of 11.9% is superior to international outcomes reported in previous studies that used the same inclusion criteria (Singapore 6.2%, Canada 9.4%, the United States 10%) [[20], [21], [22]]. Our figure compares favourably to that for other Australian states, which reported survival to hospital discharge between 9% and 13% [1]. We observed very few deaths

Author contributions

TD and EB conceived and designed the study. TD and BS acquired and analysed the data. EB and SR supervised data acquisition and analysis. All authors interpreted the data. All authors prepared and approved the manuscript.

Funding

There was no funding related to this study.

Conflict of interest

None to declare.

What is known about the topic?

Substantial regional variations exist in relation to the characteristics and outcomes of out-of-hospital cardiac arrest (OHCA). As such, an understanding of region-specific factors is essential for informing strategies to improve OHCA survival.

What this paper adds or contributes?

  • This study provides an insight into Queensland-specific patient characteristics, outcomes and determinants of outcomes of OHCA.

  • Bystander interventions substantially improve the likelihood of survival from OHCA.

  • The number needed to treat

Acknowledgements

We thank paramedic personnel for the care provided to these patients and submission of the clinical data, and Ms Louise Sims for data coding and management.

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