Objectives: It is unclear whether scene time interval (STI) is associated with better neurological recovery in the emergency medical service (EMS) system with intermediate service level.
Methods: Adult out-of-hospital cardiac arrest (OHCA) patients with presumed cardiac etiology (2012 to 2014) were analyzed, excluding patients not-resuscitated, occurred in ambulance/medical/nursing facility, unknown STI or extremely longer STI (>60 min), and unknown outcomes. STI was classified into short (0.0-3.9 min), middle (4.0-7.9 min), long (8.0-11.9 min), and very-long (12.0-59.9 min), respectively. The end point was a good cerebral performance category (CPC) 1 or 2. Multivariable logistic regression by STI group (reference=short) was performed to calculate adjusted odds ratios (AORs) with 95% confidence intervals (95% CIs) for outcomes with or without interaction term (STI∗prehospital return of spontaneous circulation, (PROSC)).
Results: Of 79,832 OHCA patients, 41,054 cases were analyzed; good CPC in the short (3.0%), middle (3.2%), long (3.0%), and very-long (2.9%) STI groups were similar, respectively (p=0.55). The AORs (95% CI) for good CPC in the final model without interaction term were 0.74 (0.58-0.95) for the middle, 0.51 (0.39-0.67) for the long, and 0.45 (0.33-0.61) for the very-long STI group (reference=short STI). The AORs in PROSC group were 1.18 (0.97-1.44) for middle STI group, 0.72 (0.57-0.92) for long group, and 0.56 (0.42-0.77) for very-long group. The AORs in non-PROSC group were 1.22 (1.06-1.40) for middle STI group, 0.82 (0.70-0.96) for long group, and 0.70 (0.57-0.85) for very-long group.
Conclusion: The middle STI (4-7min) was associated with the highest odds of neurological recovery for patients who could not be restored in the field. The STI may be a clinically useful predictor of good neurology outcome in victims of cardiac arrest.
Keywords: Cardiac arrest; Cardiopulmonary resuscitation; Emergency medical service; Scene time intervals.
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