The association between scene time interval and neurologic outcome following adult bystander witnessed out-of-hospital cardiac arrest

Objective: To analyze the association between Emergency Medical Services (EMS) scene time interval (STI) and survival with functional neurologic recovery following adult out-of-hospital cardiac arrest (OHCA). Methods: A retrospective analysis of prospectively collected data from the national Cardiac Arrest Registry to Enhance Survival from January 2013 to December 2018. All adult non-traumatic, EMS-treated, bystander-witnessed OHCA with complete data were included. Patients with STI times \u3e60 min, defined as the time from EMS arrival at the patient\u27s side to the time the transport vehicle left the scene, unwitnessed OHCA, nursing home events, EMS-witnessed OHCA, or patients with termination of resuscitation in the field were excluded. The primary outcome was survival with functional recovery (Cerebral Performance Category [CPC] = 1 or 2). Multivariable logistic regression was used to quantify the association of STI with the primary. Results: 67,237 patients met inclusion criteria with 12,098 (18.0%) surviving with functional recovery. Mean STI (SD) for survivors with CPC 1 or 2 was 19 (8.4) and 22.8 (10.5) for those with poor outcomes (death or CPC 3-4; p \u3c 0.001). For every 1-min increase in STI, the adjusted odds of a poor outcome increased by 3.5%; odds ratio = 1.035; 95% CI (1.027, 1.044); p \u3c 0.001. Restricted cubic spline analysis showed increased risk of poor outcome after approximately 20 min. Conclusion: Longer STI times are strongly associated with poor neurologic outcome in bystander-witnessed OHCA patients. After a STI duration of approximately 20 min, the associated risk of a poor neurologic outcome increased more rapidly. Keywords: Emergency medical services; Neurologic outcome; Out-of-hospital cardiac arrest