I’m sorry to hear your father and your family are going through this.
My father had his aorta rupture when he was 59. To fix that, the body is super-cooled, & blood flow to the brain was cut off for 30 minutes, that apparently is the max amount of time blood flow can be cut off to the brain.
Friends and family would talk around his beside when he was in ICU. One friend said there were so many wires in him it looked liked he could pick up Radio Moscow. Someone else mentioned something about Dallas, Texas.
When he had recovered somewhat he was convinced he was in a hospital in Moscow. Other times he was convinced he was in Dallas. Either way, he kept insisting he wanted to go home to Little Rock.
The only way he would believe he was actually in Little Rock was if a friend of the family, John Barr, came and showed him on the map. John Barr was a fellow professor, maybe of geography, or just really into maps, I don’t recall.
So, “Honest John Barr”, as my Dad started referring to him, came to the hospital and showed him a map and told him he was indeed in Little Rock. My Dad finally believed he was in Little Rock. It was probably a full six months before the confusion went away.
He later had a bypass and valve surgery. I don’t recall the memory problems being as bad after that as it was for the aorta surgery. My point is my dad came back to being my dad. It just took some time.