What are the joule dosages for synchronized cardioversion in children with unstable SVT or VT?

• A. First 0.5-1 J/kg; Second 2 J/kg
• B. First 1-2 J/kg; Second 4 J/kg
• C. First 2-4 J/kg; Second 6 J/kg
• D. First 0.5 J/kg; Second 0.5 J/kg

Answer: (A)

When a child with unstable SVT or VT needs emergency rhythm restoration, the energy for synchronized cardioversion is given in a weight-based, stepwise way to balance effectiveness with safety. The best approach is to start with a low dose and then increase if needed. A first shock of 0.5 to 1 J/kg is chosen to minimize potential myocardial injury while still aiming to terminate the tachyarrhythmia. If the rhythm persists and the child remains unstable, a second synchronized shock at 2 J/kg is delivered. This progression—low initial dose, higher second dose—provides a reliable chance to restore a normal rhythm without overexposing the heart to energy. Some guidelines allow higher maximums (up to 4 J/kg per shock) or additional shocks if necessary, but the commonly tested sequence is first 0.5–1 J/kg, then 2 J/kg. Other patterns that start with a higher first dose or fail to escalate appropriately are less aligned with the safety and effectiveness balance for pediatric patients.