title: A comparison of biphasic and monophasic waveform defibrillation after prolonged ventricular fibrillation.
abstract: OBJECTIVE
  To compare the effects of biphasic defibrillation waveforms and conventional monophasic defibrillation waveforms on the success of initial defibrillation, postresuscitation myocardial function, and duration of survival after prolonged duration of untreated ventricular fibrillation (VF), including the effects of epinephrine.
  
  
  METHODS
  Prospective, randomized, animal study.
  
  
  METHODS
  Animal laboratory and university-affiliated research and educational institute.
  
  
  METHODS
  Domestic pigs.
  
  
  METHODS
  VF was induced in 20 anesthetized domestic pigs receiving mechanical ventilation. After 10 min of untreated VF, the animals were randomized. Defibrillation was attempted with up to three 150-J biphasic waveform shocks or a conventional sequence of 200-J, 300-J, and 360-J monophasic waveform shocks. When reversal of VF was unsuccessful, precordial compression was performed for 1 min, with or without administration of epinephrine. The protocol was repeated until spontaneous circulation was restored or for a maximum of 15 min.
  
  
  RESULTS
  No significant differences in the success of initial resuscitation or in the duration of survival were observed. However, significantly less impairment of myocardial function followed biphasic shocks. Administration of epinephrine reduced the total electrical energy required for successful resuscitation with both biphasic and monophasic waveform shocks.
  
  
  CONCLUSIONS
  Lower-energy biphasic waveform shocks were as effective as conventional higher-energy monophasic waveform shocks for restoration of spontaneous circulation after 10 min of untreated VF. Significantly better postresuscitation myocardial function was observed after biphasic waveform defibrillation. Administration of epinephrine after prolonged cardiac arrest decreased the total energy required for successful resuscitation.
authors.affiliation: Institute of Critical Care Medicine, Palm Springs, CA 92262-5309, USA.
authors.forename: W
authors.initials: W
authors.lastname: Tang
authors.forename: M H
authors.initials: MH
authors.lastname: Weil
authors.forename: S
authors.initials: S
authors.lastname: Sun
authors.forename: H P
authors.initials: HP
authors.lastname: Povoas
authors.forename: K
authors.initials: K
authors.lastname: Klouche
authors.forename: T
authors.initials: T
authors.lastname: Kamohara
authors.forename: J
authors.initials: J
authors.lastname: Bisera
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D004554:Electric Countershock / Q000379:methods*; D008297:Male; D009200:Myocardial Contraction; D011446:Prospective Studies; D011897:Random Allocation; D013552:Swine; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left