Spatial and Temporal Boundaries of Remote Areas in the Initial Management of Out-of-Hospital Cardiac Arrest

Besides well-described patient-related and event-related factors, time intervals during the initial management of out-of-hospital cardiac arrest (OHCA) and distance from the emergency call and collapse location are additional influencing elements usually underrepresented by the widely applied prognostic models. The aim of this study is to analyze the influence of time and distance as crucial factors on the success of pre-hospital care of patients with OHCA, as well as the influence of other variables defined by the EuReCa Study protocol, observed during the study period, on the positive pre-hospital outcomes.

According to the EuReCa Study protocol accepted by the EuReCa_Serbia protocol, the data on all cases of adult patients with witnessed cardiac-cause OHCA receiving bystander cardiopulmonary resuscitation (CPR) measures were prospectively collected during the period October 1, 2014 to December 31, 2023, and analyzed to compare the degree of influence of different patient- and OHCA-related predictors, including time- and distance-related factors, on initial OHCA outcomes - first recorded heart rhythm, return of spontaneous circulation on scene (any ROSC), and survival to hospital admission.

During the follow-up period, 2,261 cases were registered. Female sex and OHCA location in the patient's residence were the main negative independent predictors, while full CPR measures were the main positive independent predictor of shockable initial heart rhythm. OHCA occurring in a public building, full CPR measures, and direct current (DC) shock delivery were the main positive predictors of any ROSC. Population size larger than 100,000 inhabitants and OHCA location in the patient's residence were the main negatives, while OHCA location on the street was the main positive predictor of survival to hospital admission. Emergency medical service response time in minutes and distance from the emergency call to the collapse location in kilometers were significant predictors of both shockable initial heart rhythm (p < 0.001, OR = 0.928, 95% CI = 0.889-0.967 and p < 0.001, OR = 0.910, 95% CI = 0.864-0.959, respectively) and any ROSC (p < 0.001, OR = 0.898, 95% CI = 0.855-0.943 and p < 0.001, OR = 0.874, 95% CI = 0.823-0.930, respectively).

Location, patient sex, and bystander CPR type play an important role in predicting shockable initial rhythm. The same factors, except the patient's sex, predicted any ROSC, while the main predictors of survival to hospital admission are population size and OHCA location. Both shorter emergency medical service response time and a shorter distance are significantly associated with a higher rate of shockable initial rhythm and any ROSC.