Pediatric transthoracic defibrillation: biphasic versus monophasic waveforms in an experimental model.

Objective: The purpose of this study was to determine and compare the efficacy of biphasic and monophasic waveforms in a porcine model of pediatric defibrillation.

Background: The efficacy and safety of biphasic waveforms in children has not been established.

Methods: We initially studied 27 piglets: 12 weighed 3-6 kg ('infants'), and 15 weighed 7-12 kg ('children'). Ventricular fibrillation (VF) was induced by rapid right ventricular pacing and maintained for 15 s. Transthoracic shocks of 7-100 J energy were given using monophasic (5 ms truncated exponential) and biphasic (5 ms positive, 5 ms negative pulse, truncated exponential) waveforms. A second study of four 'infant' and four 'child' piglets utilized the same protocol but with a 10 ms instead of 5 ms monophasic truncated exponential shock waveform compared with the 10 ms biphasic waveform.

Results: For both biphasic and monophasic waveforms, shock success rate (termination of VF) rose steadily as energy was increased. In the first study in the 'infant' 3-6 kg group, the 10 ms biphasic waveforms were superior to 5 ms monophasic waveforms at 10, 20, and 30 J energies, and in the 'child' 7-12 kg group at 20 and 30 J energies (P<0.05). High success rates (>80%) were achieved by 20 J (4 J/kg) biphasic waveform shocks in the 'infant' piglets and 30 J (3 J/kg) biphasic waveform shocks in the 'child' piglets. In the second study using a 10 ms monophasic waveform, we found similar results. Pulseless electrical activity occurred in two animals following biphasic shocks and in two animals following monophasic shocks.

Conclusions: Biphasic waveforms proved superior to monophasic waveforms in both infant and child models. High success rates were achieved with low-energy biphasic shocks. Biphasic waveform defibrillation is a promising advance in pediatric resuscitation.