After an initial 120–200 J shock, what energy is typically used for the next shock on a biphasic defibrillator?

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

Answer: (D)

Biphasic defibrillators are more efficient, so you can achieve defibrillation with lower energies. After the first shock in the 120–200 J range, the next shock is typically delivered at about 200 J. This provides a reliable energy boost to terminate the rhythm while minimizing myocardial injury from higher energies. If the rhythm still fails to defibrillate, follow device-specific protocols, which may involve escalating energy or moving to the device’s maximum, but 200 J is the standard next-step energy. Lower energy like 50 J would be insufficient to depolarize the myocardium, and using a higher energy like 360 J on the second attempt isn’t routinely needed and carries greater risk.