What is the most dangerous thing to do for patient with head injury and nonreactive pupils?

The most dangerous thing to do for a patient with a head injury and nonreactive pupils is to move their neck. This can damage the spinal cord and worsen the patient's condition. If the patient needs to be moved, it is important to keep their head and neck immobilized. This can be done by using a cervical collar or by placing the patient on a stretcher with their head and neck in a neutral position.