CARDIOPULMONARY RESUSCITATIONActivation of citizen responders to out-of-hospital cardiac arrestFolke, Fredrika,b,c; Andelius, Linna,c; Gregers, Mads Toftea,c; Hansen, Carolina Maltaa,b,c Author Information aCopenhagen Emergency Medical Services, University of Copenhagen bDepartment of Cardiology, Herlev Gentofte University Hospital, Copenhagen, Denmark cDepartment of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark Correspondence to Fredrik Folke, MD, PhD, Clinical Professor, Head of Research, Copenhagen Emergency Medical Services, University of Copenhagen, Denmark, Telegrafvej 5, 2750 Ballerup, Denmark. Tel: +45 28 18 29 78; e-mail: [email protected] Current Opinion in Critical Care: June 2021 - Volume 27 - Issue 3 - p 209-215 doi: 10.1097/MCC.0000000000000818 Buy Metrics Abstract Purpose of review To discuss different approaches to citizen responder activation and possible future solutions for improved citizen engagement in out-of-hospital cardiac arrest (OHCA) resuscitation. Recent findings Activating volunteer citizens to OHCA has the potential to improve OHCA survival by increasing bystander cardiopulmonary resuscitation (CPR) and early defibrillation. Accordingly, citizen responder systems have become widespread in numerous countries despite very limited evidence of their effect on survival or cost-effectiveness. To date, only one randomized trial has investigated the effect of citizen responder activation for which the outcome was bystander CPR. Recent publications are of observational nature with high risk of bias. A scoping review published in 2020 provided an overview of available citizen responder systems and their differences in who, when, and how to activate volunteer citizens. These differences are further discussed in this review. Summary Implementation of citizen responder programs holds the potential to improve bystander intervention in OHCA, with advancing technology offering new improvement possibilities. Information on how to best activate citizen responders as well as the effect on survival following OHCA is warranted to evaluate the cost-effectiveness of citizen responder programs. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.