Authors' Response.

Abstract

We appreciate the opportunity to respond to Drs Wall and Naim’s comments and criticisms. We agree that understanding of current OHCA outcomes is both important and incomplete.Like Drs Wall and Naim, we also worried about residual confounding of the relationship between ED type and survival. To confound this association, a risk factor for survival in cardiac arrest would also have to be associated with ED type. We are not aware of evidence suggesting that prehospital interventions such as bystander CPR are associated with ED type, although this is theoretically possible. However, transport time is likely associated with ED type and would likely be a confounder on the basis of the urban location of the pediatric EDs in our study. To address this legitimate concern, we reanalyzed our data, restricting the sample to EDs located in all metropolitan areas and EDs located only in large, central metropolitan areas. When restricting to metropolitan areas, survival among noninjured children with OHCA was 19.2% and 33.8% among nonpediatric and pediatric EDs, respectively (P < .001). When restricting to large, central metropolitan areas, survival was 20.2% and 29.3% among nonpediatric and pediatric EDs (P = .002). Although we did not directly measure transport times, the long transport times sometimes seen in rural areas are eliminated in this analysis.It is possible that some visits for cardiac arrest in our study were misclassified as OHCA when they were truly IHCAs. However, we believe the influence of IHCA on our analysis would be minimal for several reasons. First, in the Nadkarni study,1 there were 121 pediatric in-ED cardiac arrests across 253 large hospitals (median 260 beds), or only 0.5 IHCAs per large ED. Second, reports of nontraumatic OHCA incidence (8.0 per 100 000 person-years) from a large registry study2 are similar to the incidence of nontraumatic OHCA in our study (7.9 per 100 000 person-years), suggesting that nearly all of the analyzed patients in our study experienced OHCA. Third, although IHCA versus OHCA may be associated with the likelihood of survival, we do not have evidence that it is associated with ED type. Thus, we believe that contamination of our sample with IHCA episodes is likely to be small, and its effect on the primary analysis would also likely be small.We believe our study’s limitations are outweighed by its representativeness and inclusion of EDs that do not typically participate in cardiac arrest outcomes research. For instance, Nadkarni et al’s1 important study of IHCA outcomes was focused primarily on large facilities that paid a fee to participate in a cardiac arrest outcomes registry, which may differ in important ways from nonparticipating centers.With that said, we strongly agree with Drs Wall and Naim that further study in which OHCA registries with clinical information are used will help confirm or refute our finding that ED type may influence survival. We further encourage researchers to include care settings in which outcomes are not routinely measured, such as small rural or community EDs.