Abstract 244: Defibrillation Efficacy Is Not Influenced by Duration of Preshock Pause
A prior small study reported a strong relationship between pre-shock pause duration (PreSP) and 1st shock defibrillation efficacy during cardiac arrest resuscitation. We examined the relationship between PreSP and defibrillation efficacy across all shocks in a large cohort of out-of-hospital cardiac arrest (OHCA) resuscitations.
In an observational study of prospectively collected data, we enrolled all patients with cardiac cause OHCA presenting with VT/VF during calendar year 2009 in five EMS systems. Continuous ECG and impedance recordings from all defibrillators used during resuscitation were reviewed to measure PreSP and determine outcome for all shocks. Defibrillation success was defined as removal of VF for at least 5 seconds post-shock.
Of 902 analyzable biphasic shocks to 281 patients, 763 successfully terminated VF (85%). The median (IQR) PreSP did not differ significantly between successful and failed shocks [8 (4,17) vs 7 (5, 15) sec, p=0.34]. No significant differences were found when analyzing just first shocks [9 (4,18) vs 7 (4,15), p=0.33], just AED shocks [20 (17,23) vs 19 (15,21), p=0.31], or just manual shocks [7 (4,15) vs 7 (4,13), p=0.97]. When grouped by PreSP duration in 10-sec increments, there was no significant trend in shock efficacy with increasing pause duration (Figure, p=0.06). In a univariate regression, there was no significant relationship between first-shock PreSP duration and successful VF termination [OR = 1.15 for every 5-second increase (0.91, 1.47)].
Defibrillation success is not associated with pre-shock pause duration.
- © 2012 by American Heart Association, Inc.