A 24-year-old man is brought to the Emergency Department following a fall from a height of 2 metres, landing on his head. On initial assessment using the Glasgow Coma Scale (GCS), he opens his eyes only when spoken to (E3), is confused when speaking but uses recognisable words (V4), and obeys commands (M6). His GCS score is 13. A CT head scan is performed and shows no acute intracranial abnormalities. According to NICE guideline CG176, what is the most appropriate immediate management plan?