LAUSR

Dear Editor, I commend de Graaf et al. for exploring the effect of continuing resuscitation at the scene versus transporting to the hospital for patients in cardiac arrest in a rigorous and structured manner. However, I do have concern about the conclusion of the paper which was published in the March/April 2021 issue of Prehospital Emergency Care (1). The paper presents an analysis of patients who had return of spontaneous circulation (ROSC) prior to hospital arrival and looks at the 30-day survival relationship to the time interval from EMS arrival until ROSC. The paper includes a receiver operating characteristic (ROC) curve of 30-day survival, which shows 8minutes as “best test performance timepoint.” This depicts the likelihood of survival in patients who achieved ROSC, not the likelihood of survival of patients still in cardiac arrest if EMS transports by this timepoint. The results presented in this paper do not support the assertion that EMS should transport between 8 and 15minutes of arrival. There are no data on patients without ROSC prior to transport, and so this study does not inform whether those without ROSC in this timeframe would have better or worse survival if EMS would have started transport during that timeframe. An example of a more robust approach to the question of whether continued on-scene resuscitation or intra-arrest transport is more beneficial is found in the paper by Grunau et al (2). In this paper, the authors use a time-dependent propensity score matching approach, which allows for a more appropriate comparison of the study groups. This paper found that on-scene resuscitation was associated with higher survival to discharge, in contradistinction to the deGraaf paper. I invite the authors to provide better clarity on their interpretation of the data and how the data support their conclusion. Sincerely,