What is the first action to take when using an AED?

The first action when using an AED is to turn the AED on. This is crucial because activating the device allows it to perform its self-check, guiding you through the process with verbal prompts and visual indicators. The sooner the AED is powered on, the faster it can assess the patient's heart rhythm and determine if a defibrillation shock is needed.

Although attaching pads or starting chest compressions are important steps in the ventricular fibrillation or pulseless ventricular tachycardia scenario, those actions come after ensuring the AED is operational. Additionally, calling for emergency help is essential, but this is often done simultaneously or before approaching the patient, not as the very first action in the context of using an AED.