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Prompt defibrillation is critical for termination of ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) in out-of-hospital cardiac arrest (OHCA). For ethical reasons, the real impact of not shocking OHCA patients with an initially shockable rhythm is unlikely to be investigated in clinical trials and thus remains unknown. In this study, we described demographics, prehospital characteristics, field interventions, and outcomes in OHCA patients with an initially shockable rhythm who were and were not shocked in the field in ROC PRIMED study.
We included non-traumatic OHCA cases ≥18 years old with VF/VT as initial rhythm, who were treated in the field by EMS providers from June 2007 to November 2009 with completed case report of data concerned within PRIMED study. We report return of spontaneous circulation (ROSC) in the field and survival to hospital discharge for victims with and without shock delivered in the field. Multivariate regression analysis assessed the association between shock delivery and ROSC in the field as well as survival.
Included were 2229 adult non-traumatic OHCA cases with VF/VT as initial rhythm; 52.5% (1170) had ROSC in the field, 25.3% (564) survived to hospital discharge; 98.9% (2204) were shocked, while 1.1% (25) were not. Of the 1.1% (25) who were not shocked, 8.0% (2) achieved ROSC in the field and 4.0% (1) survived to hospital discharge. For those not shocked in the field, the unadjusted and adjusted odds ratios for ROSC were 0.077(95%CI 0.018-0.328, p=0.001) and 0.070 (95%CI 0.016-0.307, p=0.001), respectively; and for survival to hospital discharge they were 0.121(95%CI 0.044-0.377, p=0.039) and 0.066(95%CI 0.008-0.564, p=0.013), respectively.
In PRIMED study, 1.1% of OHCA victims with an initially shockable rhythm did not receive any shock on the scene, which was significantly associated with decreased ROSC in the field and survival to hospital discharge.