Final answer:
The nurse should first take measures to prevent injury when a client is having a tonic-clonic seizure, such as cushioning the head and removing nearby hazards.
Step-by-step explanation:
When a client is having a tonic-clonic seizure, the nurse's first priority should be to take measures to prevent injury. This includes actions such as cushioning the client's head, moving any harmful objects out of the way, and gently guiding the client to the floor if they are not already on a safe surface. It is also important for the nurse to maintain a calm demeanor and ensure the safety of the surrounding environment.
It is a common misconception that a tongue blade should be placed in the mouth during a seizure; however, this is not only unnecessary but can also cause harm. Similarly, restraining the client's arms and legs or elevating the head of the bed are not appropriate initial actions during a seizure.