My father recently had open heart surgery of blockage of four arteries, it took last about 5 1/2 hrs. he is 69 year with 36 years of diabetic history, also had past history of stroke and attack. but after surgery nearly 40 hrs later we have noticed chan

Ur post got cut shor: From your topic tags, i suspect that you've noticed a change in your dad's memory after his surgery. Given his history of stroke complicated by heart disease, it's very common to report memory loss after open heart surgery since small clots can fly off into brain. Or he might be suffering from delirium due to anesthesia, medications, infection, blood clot to lung, uncontrolled pain, etc.

Delirium: Fluctuating level of attention and confusion is very common given his medical history , age and recent surgery.