What is the initial energy setting for biphasic defibrillation in ventricular fibrillation or pulseless VT?

• A. 120–200 J
• B. 50–100 J
• C. 360 J
• D. 200 J

Answer: (A)

For biphasic defibrillation in ventricular fibrillation or pulseless ventricular tachycardia, you start with a mid-range energy, 120–200 joules. The biphasic waveform is more efficient than older monophasic shocks, so you can achieve successful defibrillation at lower energies. Using this lower range helps terminate the chaotic electrical activity while reducing myocardial injury and post-shock dysfunction. If the first shock doesn’t restore a perfusing rhythm, you follow the device’s protocol to repeat or escalate energy within the recommended limits (often up to the device’s maximum, which can vary). Lower initial energy is favored because it’s effective and gentler on the heart, whereas going too low would risk failure, and going too high isn’t necessary with biphasic devices.