Who has dealt with hospital delirium?

My dad (84) suffered from two strokes last Fall. He's made a fairly good recovery, but still has some cognitive challenges (which at this point we expect may be permanent). He fell last Friday and hit his head. Hard. He had a minor brain bleed, so the hospital wanted to keep him for a few days for observation. He was doing really well - a bit lethargic, but engaging in conversations, eating well, watching his favorite TV shows, walking around the whole hospital floor with the PT, then on the day of discharge he had a sudden onset of delirium. He's essentially been in what seems like a deep sleep now for 3.5 days. We can't rouse him. Repeat CT, MRI, chest X-rays, bloodwork, urinalysis all clear. Re-evaluated his meds. Evaluated for seizure activity. In short, we can't find an underlying cause. Has anyone dealt with this and any advice on what has worked to re-orient them? He's so weak and small - I can't imagine he can go on for much longer in this state :( We're trying to bring things he's familiar with, play familiar music, talk to him to let him know he's safe and cared for, etc. My cousin who works in palliative said we could try to bring him home (we'd have to hire an ambulance transport), but I don't think any of us are equipped to provide the level of care he needs...