A comparison of biphasic and monophasic waveform defibrillation after prolonged ventricular fibrillation

Study objective: To compare the effects of biphasic defibrillation waveform s and conventional monophasic defibrillation waveforms on the success of in itial defibrillation, postresuscitation myocardial function, and duration o f survival after prolonged duration of untreated ventricular fibrillation ( VF), including the effects of epinephrine. Design: Prospective, randomized, animal study. Setting: Animal laboratory and university-affiliated research and education al institute. Participants: Domestic pigs. Interventions: VF was induced in 20 anesthetized domestic pigs receiving me chanical ventilation. After 10 min of untreated VF, the animals were random ized. 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 wa veform shocks. When reversal of VF was unsuccessful, precordial compression was performed for 1 min, with or without administration of epinephrine. Th e protocol was repeated until spontaneous circulation was restored or for a maximum of 15 min. Measurements and results: No significant differences in the success of init ial resuscitation or in the duration of survival were observed. However, si gnificantly less impairment of myocardial function followed biphasic shocks . Administration of epinephrine reduced the total electrical energy require d for successful resuscitation with both biphasic and monophasic waveform s hocks. Conclusions: Lower-energy biphasic waveform shocks were as effective as con ventional higher-energy monophasic waveform shocks for restoration of spont aneous circulation after 10 min of untreated VF. Significantly better postr esuscitation myocardial function was observed after bipbasic waveform defib rillation. Administration of epinephrine after prolonged cardiac arrest, de creased the total energy required for successful resuscitation.