Final answer:
In the case of a 4-year-old patient with no spontaneous ventilations and pulseless wide complex tachycardia, while CPR is being administered, the next step is to use an AED for defibrillation.
Step-by-step explanation:
Your 4-year-old patient is unresponsive, has no spontaneous ventilations, and is in pulseless wide complex tachycardia. Given that CPR is already being provided, the next step in the treatment would involve the use of an automated external defibrillator (AED) to deliver a controlled electrical shock in an attempt to restore a normal heart rhythm. Since the patient shows a pulseless electrical activity (PEA) with a wide complex tachycardia, it's critical to continue chest compressions and seek advanced life support intervention with equipment and medications as per pediatric advanced life support (PALS) protocols.