Automated external defibrillators and in-hospital cardiac arrest: Patient survival and device performance at an Australian teaching hospital

Abstract

Aims

To evaluate the effect of automated external defibrillators (AEDs) on patient survival and to describe the performance of AEDs after in-hospital cardiac arrest.

Methods

Prospectively collected data were analysed for cardiac arrests in the general patient care areas of a teaching hospital during the 3 years before and the 3 years after the deployment of AEDs. The association between availability of an AED and survival to hospital discharge was assessed using multivariate logistic regression. AED performance during automated management of the initial rhythms was assessed using information captured by the AEDs.

Results

There were 84 cardiac arrests in the AED period and 82 in the pre-AED period. Patient and event characteristics were similar in each period. The initial rhythm was shockable in 16% of cases. Return of spontaneous circulation was higher in the AED period (54% vs. 35%, P = 0.02) but the proportion of hospital survivors in each period was similar (22% vs. 19%, P = 0.56). The adjusted odds ratio for hospital survival when an AED was available was 1.22 (95% CI 0.53–2.84, P = 0.64). An AED was applied in 77/84 (92%) possible cases. Median interruption to chest compressions was 12 s (inter-quartile range 12–13). An automated shock was delivered in 8/13 (62%) possible cases.

Conclusions

Availability of AEDs was not independently associated with hospital survival. Shockable presenting rhythms were not common and, in keeping with the manufacturer's specifications, the AEDs did not shock all potentially shockable rhythms. The hands-off time associated with automated rhythm management was considerable.

Introduction

Automated external defibrillators (AEDs) can analyse the cardiac rhythm, charge automatically if a shockable rhythm (i.e. ventricular fibrillation [VF] or ventricular tachycardia [VT]) is recognised and provide the operator with audible and/or visual prompts for the safe delivery of an electrical shock.¹ According to the recently updated guidelines of the Australian Resuscitation Council, the use of AEDs as a component of managing in-hospital cardiac arrest is acceptable.2, 3, 4, 5, 6

The benefits to patients of using AEDs during cardiac arrests in certain out-of-hospital settings have been demonstrated.7, 8 However, there has never been a randomised controlled trial of AEDs for in-hospital cardiac arrest and recent observational studies have cast doubt on the effectiveness of AEDs in hospitals. A single-centre study found that replacing manual defibrillators with AEDs made no difference to survival to hospital discharge after in-hospital cardiac arrest when the initial rhythm was shockable (31% vs. 29%, P = 0.80), and survival to hospital discharge was significantly reduced if the rhythm was not shockable (15% vs. 23%, P = 0.04).⁹ A study of almost 12,000 patients from over 200 hospitals found AED use during in-hospital cardiac arrest was independently associated with a reduction in survival to hospital discharge (16.3% vs. 19.3%; adjusted rate ratio 0.85, P < 0.001).¹⁰ The accompanying editorial advocated a cautious approach to introducing AEDs into the hospital setting.¹¹

There are factors that may count against the use of AEDs for in-hospital cardiac arrest. Automated rhythm management is associated with longer interruptions to chest compressions compared to non-automated management12, 13 and, in out-of-hospital settings where AEDs have improved patient outcomes, the initial cardiac arrest rhythm was shockable in more than half the cases and the response times of advanced life support providers were relatively long,7, 8 but in the hospital setting the initial rhythm is shockable in only about one out of five cases and the response times of advanced life support providers are relatively fast.9, 10, 14, 15

We have previously reported that there was no change in survival to hospital discharge after in-hospital cardiac arrest in the first year following the deployment of AEDs to the general patient care areas of our hospital.¹⁵ We now present cardiac arrest data for the 3 years before and the 3 years after the AED deployment. The use and performance of AEDs and the effect on patient outcomes is assessed.