Abstract 142: Persistent Ventricular Fibrillation Is Common After Defibrillation with 150 J
Background: The recommended first shock energy setting for biphasic Philips defibrillators is based on one study, which showed 96% first shock success for converting patients out of Ventricular Fibrillation (VF) at 150J, but 2010 AHA Guidelines suggest higher doses of energy may be necessary.
Hypothesis: We hypothesized that first shock success rate for patients initially in VF would be less than 90%.
Methods: Cardiac arrest calls from the City of Pittsburgh were enrolled using a reverse chronological screen from March of 2011 to November of 2009. Cases (n=50) were included when the first analysis resulted in a shock being delivered (at the 150J energy setting). The first analysis was performed either with the Philips monitor in automatic mode by first responders or in manual mode by paramedics. Calls were then analyzed for the subsequent five minutes and the shock outcomes were recorded at the immediate post-shock and at the five-minute marks. Success was defined by the conversion of VF into a non-shockable rhythm immediately following defibrillation. Logistic regression was used to examine association between pre-shock pause and success of defibrillation immediately and after 5 minutes.
Results: Rhythm immediately post-shock was Persistent VF 24 (48%), Pulses 9 (18%), Asystole 10 (20%), or PEA 7 (14%). A total of 26 cases (52%, 95%CI 37%-67%) had termination of VF immediately by first shock. After 5 minutes their rhythms were Asystole 7(27%), PEA 4(15%), Pulses 9(35%), VF 5(19%), or Paced 1(4%). Among 24 cases with Persistent VF after first shock, 15/24 (63%) received a second shock. At 5 minutes, their rhythms were Asystole 3(12%), VF 5(21%), or PEA 1(4%). The range and mean (SD) of Peri-shock pauses in seconds were: Pre-shock 3-27, 14.2 (5.4), Post-shock 2-33, 11.2 (7.5), Peri-shock 8-51, 25.1 (9.7). There was no relation between pre-shock pause and conversion to non-shockable rhythm, immediately (OR 1.12, 0.98-1.28) or after 5 minutes (OR 1.02, 0.90-1.14).
Conclusion: This study indicates that the success rate of biphasic defibrillation at 150J is lower than previously published. Additionally, pre-shock pause had no relation with success of the shock.
- © 2012 by American Heart Association, Inc.