A 5-year-old child is recovering after undergoing surgery for a brain tumor. The nurse is reviewing the child's postoperative care plan. The child is alert, but the nurse notices that the child is vomiting and complaining of a headache. The nurse's priority action should be:

Encourage the child to drink fluids to stay hydrated

Position the child in a flat supine position to prevent increased intracranial pressure (ICP)

Administer an antiemetic to control vomiting

Assess the child's neurological status and check for signs of increased intracranial pressure