Smartphone dispatch of volunteer responders may not increase bystander use of automated external defibrillator in out-of-hospital cardiac arrest – the SAMBA trial

1. This randomized controlled trial evaluating the effect of Heartrunner, a smartphone application, demonstrated no significant increase in bystander-attached automated external defibrillator (AED) among volunteer responders who received instructions to collect nearby AED compared to those instructed to report to the patient and begin cardiopulmonary resuscitation (CPR).

2. Future studies to evaluate the efficacy of this application should include larger sample sizes and clinical-based outcomes, such as patient morbidity and mortality rates.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Prompt cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) use are critical in improving survival for out-of-hospital cardiac arrest (OHCA). A previous trial demonstrated that a mobile phone dispatch of volunteer responders increased bystander CPR rates. Recently, a mobile phone application called Heartrunner, was developed to remind users to use AEDs. The SAMBA randomized clinical trial investigated if the Heartrunner application improved the use of AEDs by bystanders during OHCA. This trial was conducted between December 7, 2018, and January 31, 2020. Volunteer responders were randomized 1:1. During a suspected case of OHCA, volunteer responders within a 1.3 km radius received a request via their smartphone application to accept or decline the alert. The intervention group received instructions to collect the nearest AED available, whereas the control group was instructed to go directly to the patient and begin CPR. Emergency calls for OHCA between 7:00 AM and 10:59 PM were eligible. The primary outcome was bystander-attached AED, which was the proportion of patients that had AED attached by any bystander (this included volunteer responders in the study and other lay volunteers not part of the study). During the study period, the response rate by volunteer responders was 72%. 13.2% of patients had bystander-attached AED in the intervention group compared to 9.5% in the control group (difference: 3.8% [95% CI: -0.3 to 7.9], p = 0.08; risk ratio [RR]: 1.40 [95% CI: 0.97-2.01]). Most bystanders that attached the AEDs were not volunteer responders in the study. No significant difference was observed between groups among bystander CPR (RR: 0.96 [95% CI: 0.89-1.05]) and bystander defibrillation (RR: 0.94 [95% CI: 0.50-1.79]). Overall, this randomized clinical trial demonstrated a non-significant 3.8% increase in bystander-attached AED in the intervention group compared to the control. However, this study was limited by the lack of clinical outcomes, such as the effect on patient morbidity and mortality. Currently, the efficacy of this application in improving OHCA is unclear and requires further evaluation.

Click to read the study in JAMA Cardiology

Click to read an accompanying editorial in JAMA Cardiology

Relevant Reading: Mobile-phone dispatch of laypersons for CPR in out-of-hospital cardiac arrest

Image: PD

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