title: A high peak current 150-J fixed-energy defibrillation protocol treats recurrent ventricular fibrillation (VF) as effectively as initial VF.
abstract: OBJECTIVE
  We tested the hypothesis that the frequency of shock success differs between initial and recurrent episodes of ventricular fibrillation (VF).
  
  
  METHODS
  Out-of-hospital cardiac arrest patients presenting with VF from December 1996 to February 2007 defibrillated using an AED with a fixed-energy protocol (150 J) (Philips Medical Systems, Seattle, WA) were included for analysis. We defined shock success as termination of VF within 5s post-shock (either asystole or organized rhythm). Generalized estimating equation (GEE) analysis was used to adjust for the interrelatedness of shocks within each patient.
  
  
  RESULTS
  One hundred and three events occurred during the study period. Patient characteristics included: mean age 64.4 years, 82.5% male, and 81.6% bystander witnessed. Synchronized call-to-shock time was 6.4+/-2.3 min (mean+/-S.D.). VF recurred in 64 (62.1%) patients. Two hundred and fifty-seven shocks delivered for initial (101) or recurrent (156) VF were available for analysis. Initial shocks terminated VF in 93/101 (92.1%); subsequent shocks terminated recurrent VF in 140/156 (89.7%). GEE odds ratio for shock type (initial versus refibrillation) was 1.10 (95% CI 0.37-3.24, p=0.87). After adjusting for potential confounders, shock type remained insignificant (OR 1.14, 95% CI 0.41-3.2, p=0.80). We observed no significant difference in ROSC (34.4% versus 46.2%, p=0.23) or survival (37.5% versus 41.0%, p=0.72) between those with and without VF recurrence.
  
  
  CONCLUSIONS
  We observed no significant difference in the frequency of shock success between initial and recurrent episodes of VF using this AED with a 150 J fixed-energy protocol. VF recurrence is common and does not adversely affect shock success, ROSC or survival.
authors.affiliation: Department of Emergency Medicine, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
authors.forename: Erik P
authors.initials: EP
authors.lastname: Hess
authors.forename: James K
authors.initials: JK
authors.lastname: Russell
authors.forename: Ping-Yu
authors.initials: PY
authors.lastname: Liu
authors.forename: Roger D
authors.initials: RD
authors.lastname: White
mesh_terms: D000368:Aged; D016887:Cardiopulmonary Resuscitation; D016009:Chi-Square Distribution; D004554:Electric Countershock / Q000379:methods*; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D015996:Survival Rate; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000209:etiology / Q000628:therapy*