Optimal Scene Time to Achieve Favorable Outcomes in Out-of-hospital Cardiac Arrest: How Long Is Too Long?

Abstract

BackgroundDespite advances in resuscitation science and public health, out-of-hospital cardiac arrest (OOHCA) cases have an average survival rate of only 12% nationwide, compared to 24.8% of cases occurring in hospital. Many factors, including resuscitation interventions, contribute to positive patient outcomes and have, therefore, been studied in attempts to optimize emergency medical services (EMS) protocols to achieve higher rates of return of spontaneous circulation (ROSC) in the field. However, no consensus has been met regarding the appropriate amount of time for EMS to spend on scene.AimA favorable outcome is defined as patients that achieved the combination of ROSC and a final disposition of “ongoing resuscitation in the emergency department (ED).” The primary purpose of this preliminary study was to determine the scene time interval (STI) in which American urban EMS systems achieved the highest rates of favorable outcomes in non-traumatic OOHCAs.MethodsAll EMS-related data, including demographics, presenting rhythm, airway management, chemical interventions, and ROSC were recorded using a standardized EMS charting system by the highest-ranking EMS provider on the ambulance. The reports were retrospectively collected and analyzed.ConclusionOur data suggest that the optimal 20-minute STI for OOHCA patients in an urban EMS system is between 41 and 60 minutes. Interestingly, the 10-minute interval within the 41-60 minute cohort that provided the highest rate of ROSC was between 41 and 50 minutes. Generally, the longer the STI, the greater the percentage of favorable outcomes up to the 50-minute mark. Once past 50 minutes, a phenomenon of diminishing return was observed and the rates of favorable outcomes sharply declined. This suggests a possible “sweet spot” that may exist regarding the optimal scene time in a cardiac arrest encounter. Significant differences between the average number of interventions per patient were found, however, many confounding factors and the limited data set make the results difficult to generalize.

Impact of emergency medical service with advanced life support training for adults with out-of-hospital cardiac arrest in the Republic of Korea: A retrospective multicenter study

“…In another study, the optimal STI was reported to be 8-15 min because 90% of survivors achieved a prehospital ROSC within the first 15 min of EMS resuscitation [24]. Depending on the initial ECG rhythm, whether the termination of resuscitation rule is applied at the scene, and the primary outcome, the optimal STI in OHCA varies from 4 to 50 min [25][26][27].…”

Assessment of Ambulance Response Time: A Study of Tabriz Emergency Medical Center, Tabriz City, Iran

“…Since a long time ago, many efforts have been made to evaluate and improve the quality of EMS [6]. The effective and confident services must be based on standards [4,7,8]. EMS system focuses on a wide range of cardiovascular, trauma, and other emergencies, and many variables such as ambulance response time are used to monitor and evaluate the quality of EMS services [9].…”