If you put the body and mind under enough stress, anything can happen.
After bypass surgery, I would only walk in the hospital halls with the nurses if my wife would be there and on guard to warn me about the car that I thought raced through the hallways was coming.
Yes, I'm over 70!
I do agree with everything posted, but to be on the safe side, make sure they do a blood gas to ensure there is sufficient oxygen in his bloodstream for the brain. I have seen this a few times where the usual finger sensor reads over 90% then after a blood gas test they realise the oxygen saturation is very low.
I have seen similar effects in old people, 70 or more, just due to anesthetic.
Jesus
For people who have never had any mental problems prior to an experience like this, they generally are fine once they get well and get out of the hospital and are back home and are off of major pain medication. Once their situation is back to normal, then they are back to normal too.
My guess would be, probably yes. Some people are a lot more sensitive to heavy-duty drugs than other people. My grandfather had a month-long delerium after abdominal surgery and thought he was in the catacombs under the vatican (he was in a Catholic hospital, LOL), and he came out of it and was mentally normal again after that. He was just very sensitive to anaesthetics. He had that same experience after both of the two times that he had major surgery in his life. After I had heart-valve surgery, I had some mild hallucinations the first couple of days that I was back in my hospital room. Also, I don't know your husband's age, but just being in the hospital can sometimes be very disorienting for some older folks. In addition, there is a thing called, I think, "ICU psychosis" in which people can get disoriented just from being in ICU. If you're in a place where you can't tell day from night, and you're sick or in pain, and you're on mind-altering drugs, it's rough.