Response by Baekgaard et al to Letters Regarding Article, “The Effects of Public Access Defibrillation on Survival After Out-of-Hospital Cardiac Arrest: A Systematic Review of Observational Studies”
Authors: Josefine S. Baekgaard, Søren Viereck, Thea Palsgaard Møller, Annette Kjær Ersbøll, Freddy Lippert, Fredrik Folke
Journal: Circulation (2018)

We thank Chertoff et al, Karam et al, and El-Battrawy et al for their interest in our recently published systematic review. 1 Chertoff et al suggest analyzing whether the choice of initial intervention, bystander CPR compared with direct defibrillation, has an effect on survival.Although we agree this would be of great interest, the heterogeneity of our included studies does not allow such a comparison.However, a recent large study by Kragholm et al 2 showed that 1-year survival and neurological outcomes among 30-day survivors of out-of-hospital cardiac arrest (OHCA) significantly improved if the patient had received early bystander defibrillation or CPR compared with no bystander resuscitation, with the absolute 1-year risk of death being lowest in the group of patients who received early bystander defibrillation.Indeed this supports the findings in our systematic review.Early CPR and use of automated external defibrillators seem to be associated with higher short-and long-term survival as well as neurological intact survival.Karam et al mention that lay first responders who get involved in public access defibrillation are more likely to be trained in basic life support and thus able to recognize the OHCA early, call the emergency medical services, and perform more efficient CPR than the average bystander.Therefore, Karam et al argue that an accurate comparison of the intrinsic effect of defibrillation by a lay first responder versus an Emergency Medical Dispatch Center-dispatched professional first responder is unobtainable through our study.While we agree that our review cannot answer this question, it is noteworthy that a large, randomized study found that Emergency Medical Dispatch Center-dispatched trained lay first responders were able to arrive before the emergency medical services and start CPR in 25% of all OHCAs, but with no significant effect on survival. 3This study only looked at bystander CPR and did not include automated external defibrillators.However, studies have shown that survival increases significantly with early use of automated external defibrillators, 2 thus confirming the importance of early defibrillation found in our review.El-Battrawy et al also pointed out an important issue: prehospital efforts are just 1 step in the chain of survival.We certainly agree that other factors such as in-hospital care are important for OHCA survival as well as for neurological intact outcome.However, the studies included in the current review were carried out between 1997 and 2013, during which in-hospital treatment has improved.For example, in targeted temperature management, the optimal target temperature as well as the length of cooling are still debated. 4Furthermore, studies have shown improved survival if patients with OHCA are admitted to a tertiary center compared with a nontertiary center. 5Nevertheless, the study by Kragholm et al elegantly showed that prehospital interventions such as bystander CPR and defibrillation be-