Etiology affects predictors of survival for out-of-hospital cardiac arrest

In the United States, hundreds of thousands of individuals each year die from cardiac arrest [1]. Cardiac arrests can be precipitated by a multitude of events, including cardiac dysfunction, drug overdose, asphyxiation, and trauma [2,3]. Emergency medical services (EMS) are typically the first responders to cardiac arrest in the out-of-hospital set- ting [4]. Data from the EMS perspective has uncovered important find- ings and trends in the incidence of cardiac arrest, as well as shed light on the optimal strategies for managing cardiac arrest patients [5-7]. Studies suggesting links between pre-EMS CPR (bystander CPR) and shockable rhythms and patient survival have led to a consensus that cardiac arrest survival can be predicted by: 1) whether or not the arrest was witnessed by a bystander or EMS; 2) whether CPR was adminis- tered by a bystander; 3) whether the patient was in a shockable cardiac rhythm; and 4) whether return of spontaneous circulation (ROSC) was achieved in the field [6]. The term etiology is used to describe the cause or the origin of a cardiac arrest [3,5,7]. Localized analyses suggest that different arrest etiologies are associated with different rates of survival in both adult and pediatric patients [3,8,9]. Aside from meta-analyses, there has not been significant literature examining how arrest etiology specifically affects patient outcomes with a large sample population, on a national scale [10]. To understand how arrest etiology affects three key predictors of cardiac arrest survival on a broad scale (pre-EMS CPR, first monitored arrest rhythm, and ROSC achievement), we queried the National Emer- gency Medical Services Information System (NEMSIS), a database of millions of EMS runs in the United States [11]. Inclusion criteria were out-of-hospital cardiac arrests between January 2017 and December 2019 where EMS providers documented the suspected cardiac arrest etiology, whether or not pre-EMS CPR was performed, the first monitored arrest rhythm, and whether or not any return of spontane- ous circulation (ROSC) was achieved. Arrests were compared using the Presumed Cardiac etiology as a benchmark: two-proportion Z-tests helped establish statistical significance. Arrests from 2020 to 2021 were excluded because reports suggest variations in the rates of pre-EMS CPR and ROSC achievement have taken place as a result of the COVID-19 pandemic [12,13]. A total of 242,799 arrests met inclusion criteria. 77.9% of arrests were Presumed Cardiac, followed by Respiratory/Asphyxia (10.3%), Trauma (6.4%), Drug Overdose (4.2%), Drowning/Submersion (0.7%), Exsangui- nation (0.5%), and Electrocution (0.1%). Using the Presumed Cardiac eti- ology as a benchmark, first monitored arrest rhythms, rates of pre-EMS CPR, and rates of ROSC achievement varied significantly across the other arrest etiologies (Table 1). Presumed Cardiac arrests (54.5%) and Drug Overdose arrests (55.0%) received comparable rates of pre-EMS CPR. Arrests involving Drowning/ Submersion (68.8%) and Electrocution (71.8%) received significantly higher rates of pre-EMS CPR, and arrests involving Respiratory/As- phyxia (48.44%), Trauma (40.2%), and Exsanguination (39.8%) received significantly lower rates of pre-EMS CPR (p < .01). Nearly one-fifth of Presumed Cardiac arrests (17.7%) were initially shockable. Electrocution-related arrests were significantly more likely to be initially shockable (49.1%), while all other etiologies were signifi- cantly less likely to be initially shockable (p < .01). Finally, ROSC achievement rates also varied significantly among arrests. Presumed Cardiac arrests (26.0%) and Drowning/Submersion arrests (28.0%) had comparable rates of ROSC achievement. However, Electro- cution arrests (42.6%), Respiratory/Asphyxia arrests (41.4%), and Drug Overdose arrests (30.3%) had significantly higher rates of ROSC achieve- ment, while Exsanguination arrests (22.6%) and Trauma arrests (15.1%) and had significantly lower rates of ROSC achievement (p < .01). Our data show that categorizing out-of-hospital cardiac arrests by etiology reveals significant differences in incidence, initial treatment, and outcomes. For instance, patients facing electrocution-related car- diac arrests were associated with the highest rates of pre-EMS CPR, were the most likely to be found with a shockable rhythm, and had the highest rates of ROSC achievement. This could be due to the circum- stances surrounding electrocution-related arrests being more favorable to factors shown to increase cardiac arrest survival (eg. electrocution ar- rests happening on job sites where multiple CPR-trained individuals are present). On the other hand, arrests classified by EMS as being caused by trauma or exsanguination were associated with the lowest rates of ROSC achievement. Among other things, one contributing factor could be low pre-EMS CPR due to bystanders being hesitant to perform CPR on victims of traumatic injury or exsanguination due to a lack of scene safety or isolation from body substances or victims. Our study is limited by the fact we do not have data on rates of neurologically-intact survival or survival to hospital discharge since EMS patient care reports rarely link with hospital data. Further studies should closely examine specific arrest etiologies and report salient factors that accompany each type of cardiac arrest.

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Shekhar AC, Campbell T, Mann NC, Blumen I. Etiology affects predictors of survival for out-of-hospital cardiac arrest. The American Journal of Emergency Medicine. 2022 Feb 9.

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Shekhar, Aditya C; Campbell, Teri; Mann, N Clay; Blumen, Ira. (2022). Etiology affects predictors of survival for out-of-hospital cardiac arrest. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/250342.

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Etiology affects predictors of survival for out-of-hospital cardiac arrest

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