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).

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 >60 min, defined as the time from EMS arrival at the patient's 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.

outcome.

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 < 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 < 0.001. Restricted cubic spline analysis showed increased risk of poor outcome after approximately 20 min.

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.