A nurse is caring for a school-age child who has a new plaster cast on her right arm. Which of the following actions should the nurse take?

A. Place a warm, moist heat pack on the cast: Incorrect. Moisture can damage the integrity of a plaster cast, and heat can increase swelling. B. Position the casted arm in a dependent position: Incorrect. Keeping the arm elevated helps reduce swelling and pain. C. Move the casted arm with a firm grasp: Incorrect. A firm grasp can cause further injury or discomfort. It’s important to handle the casted limb gently. D. Administer diphenhydramine to relieve itching: Correct. Itching is common under a new cast, and diphenhydramine can help manage this symptom without risking damage to the cast.