Study 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
Design: Prospective, randomized, animal
Setting: Animal laboratory and
university-affiliated research and educational institute.
Participants: Domestic pigs.
Interventions: 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
Measurements and 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