What should the nurse place under the head of a client having a tonic-clonic seizure on the floor?

Placing a pillow under the head of a client having a tonic-clonic seizure is a sound practice aimed at preventing injury. During a seizure, the individual may experience violent muscle contractions and uncontrolled movements, which can lead to head trauma if the person is lying on a hard surface. A pillow provides a cushioning effect, helping to protect the head from impact with the floor, reducing the risk of injury.

Using a rolled towel may not provide adequate support and cushioning, as it could be too firm or not stable enough to maintain its shape during the seizure. A blanket, while softer, typically lacks the firmness and structure that a pillow has to secure the head in a safe and elevated position. A chair is an unsuitable choice altogether, as it does not belong on the floor where the individual is having a seizure and can create a risk of falling or further injury if the person were to convulse.

In summary, a pillow is the most appropriate item to place under the head during a seizure due to its ability to effectively absorb shock and prevent head injuries.