Final answer:
The first action to take when a coworker sustains a high voltage shock and is unconscious is to ensure your own safety. Call for medical help immediately and assess the scene for any potential hazards.
Step-by-step explanation:
The first action to take when a coworker sustains a high voltage shock and is unconscious is to ensure your own safety. It is crucial to not become a second victim and add to the emergency. You should call for medical help immediately by dialing emergency services.
While waiting for help to arrive, you can assess the scene for any potential hazards and make sure the power source is safely disconnected before attempting any rescue.