A little puzzled, looking for some input

I had a pt for a few days last week that has just been stuck in my mind and troubling. Last I heard they are looking for an accepting hospital to actually transfer to a higher level of care. However he is self pay so I don't think he will be going anywhere else. I'm not so much looking for a diagnosis, but more so if anyone has seen anything like this before. Pt is a 33 y/o male originally admitted as a non tele pt to med/sug floor for sickle cell crisis. pt had been seen in the ER twice over the past 36 hours before being admitted for the same thing. Treated for pain and sent home. Pt's retic count is finally elevated so pt is admitted and treated with dilaudid IVP not PCA. Less than 24 hours into hospital stay the pt's wife starts reporting AMS and decreased level of consciousness. Doc's still write a d/c order for pt. It is very apparent by midmorning though that the pt is not going anywhere. He stops eating, starts sleeping more, stops talking, and finally just starts staring off and moaning. His eyes start to roll into the back of his head. He had transfer orders to ICU, just waiting on an open bed. About 17:30 I receive him as a transfer into icu. Initial O2 sat of 30's-40's, hr 120's-130's, not following commands, essentially nonresponsive, eyes rolling around and to the back of his head. We got him in Immediatley placed on nonrebreather and discussed a code for intubation and air way protection but his sats rose quickly to the 90's, HR came down with increase in O2 sat. Over the next few days his neuro status has barely improved and he ended up having to move over to bipap but never has required intubation. However if you take the bipap off for more than just a few minutes he has a seizure and desats. He desats as a result of the seizure, not before so I can't seem to tie the two together. I also can't seem to figure out how we went from sickle cell crisis to such a change in mental status. I am curious to see later on if the diagnose him with an anoxic brain injury because his wife said he was having what looked like the seizures he was having in ICU before he came to us but the floor nurse just said it was shivering and put a blanket on him. He has been started on Keppra with no change in the seizures. CT scan was negative for everything. We haven't been able to get an MRI because we don't have a Bipap that can go in there, only a vent is down there and when he comes off bipap he seizes. No other past medical hx except for a cholecystectomy, pneumonia once and a bout of food poisoning. His spleen and liver are now enlarged. Elevated lft's and ammonia increased for 48 but decreased with lactulose. The hematologist said lft's can occur with sickle cell, but it never usually affects the spleen. He is unsure if it was ever sickle cell in the first place. Have you ever seen anything like this before? Sickle cell chest syndrome has been discussed, but it doesn't account for the spleen. Pt also sits at about a temp of 100-101 with Tylenol. Again not looking for a dx, just have you seen anything happen like this before?