Final answer:
The nurse should implement the action of defibrillation with one shock immediately when a client's telemetry monitor indicates ventricular fibrillation.
Step-by-step explanation:
When a client's telemetry monitor indicates ventricular fibrillation (VF), the nurse should immediately implement the action of defibrillation with one shock. Ventricular fibrillation is a life-threatening condition where the ventricles are not effectively pumping blood. Defibrillation uses special paddles to apply a charge to the heart from an external electrical source in an attempt to establish a normal sinus rhythm. It is the most common and effective treatment for ventricular fibrillation, and prompt action is crucial to save the client's life.