title: Evaluation of biphasic transthoracic defibrillation in an animal model of prolonged ventricular fibrillation.
abstract: OBJECTIVE
  To determine whether a biphasic defibrillation waveform (BDW) would produce a superior rate of converting prolonged ventricular fibrillation (VF) into a perfusing rhythm and delay the occurrence of asystole and/or pulseless electrical activity (PEA) during the resuscitation attempt, when compared with a monophasic defibrillation waveform (MDW).
  
  
  METHODS
  The authors performed a prospective, randomized, blinded experiment using an established swine model of prolonged VF. Thirty-four mixed-breed domestic swine (mean mass 22.9 kg) were sedated (ketamine/xylazine), anesthetized (isoflurane), and intubated. Aortic and femoral venous catheters were placed. ECG was monitored continuously. The animals were shocked into VF (3-s, 100-mA, 60-Hz shock), and were untreated for 8 minutes. Advanced Cardiac Life Support (ACLS) began with 1 minute of standardized (Thumper) chest compressions and ventilation. The animals were randomized to treatment with either BDW or MDW. Standard ACLS protocols were followed. The energy sequence was 2.5 J/kg first, 3.5 J/kg second, and 4.5 J/kg for all subsequent shocks. Outcome variables were time to event of asystole/PEA, return of spontaneous circulation (ROSC), and one-hour survival. Data were analyzed with two-tailed Fisher's exact test and Kaplan-Meier survival plots (alpha = 0.05).
  
  
  RESULTS
  ROSC occurred more frequently in the BDW group (7/17) compared with the MDW group (1/17); p = 0.04. Survival analysis showed that the BDW significantly delayed the occurrence of asystole/PEA during the resuscitation attempt when compared with the MDW; log-ranked p = 0.02. One-hour survival rates (5/17 BDW and 1/17 MDW, p = 0.17) did not differ.
  
  
  CONCLUSIONS
  BDW resulted in a superior rate of ROSC and delay in the occurrence of asystole/ PEA during the resuscitation attempt when compared with MDW.
authors.affiliation: Department of Emergency Medicine, Allegheny General Hospital, MCP-Hahnemann University, School of Medicine, Pittsburgh, PA 15212, USA. mscheatz@aherf.edu
authors.forename: M D
authors.initials: MD
authors.lastname: Scheatzle
authors.forename: J J
authors.initials: JJ
authors.lastname: Menegazzi
authors.forename: T L
authors.initials: TL
authors.lastname: Allen
authors.forename: S B
authors.initials: SB
authors.lastname: Durham
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004554:Electric Countershock / Q000379:methods*; D005069:Evaluation Studies as Topic; D005260:Female; D008297:Male; D011897:Random Allocation; D012680:Sensitivity and Specificity; D016019:Survival Analysis; D015996:Survival Rate; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000401:mortality / Q000628:therapy*