Hello,
I'm Stephanie and I had a kidney transplant six years ago. I experienced significant brain fog after surgery. Within a few days, I could read, but had trouble remembering what I read from one page to the next. I listened to the medicines they placed me on, but could not memorize. I could write simple texts and emails. I could watch hgtv shows, but had trouble following shows with complex story-lines.

What you are describing sounds fundamentally different than the brain fog I experienced. You may have already done these things, but I would;
* request a neuro consult. I would research which neurologist you would like him to be seen by.
* communicate you do not feel safe to take him home until some diagnosis and assessment is provided, so you can determine the level of care he is going to need. (The words: I do not feel safe taking him home...... are key alert words the hospital has to take seriously)
* request speech therapy in addition to whatever physical therapy they normally provide.
* be the very squeaky wheel.