I am assuming your father's operation involved being on a pump and your father's heart was not pumping during the operation. It is not unexpected for some cognitive loss following on-the-pump heart bypass surgery. It is a phenomenon known as "pump head" that is oserved in some patients following coronary bypass surgery.
Researchers from Johns Hopkins University now say that although some patients may experience declines in mental skills and motor speed immediately after surgery, such negative side effects will usually subside within a matter of months.
"A small subset of patients -- mostly those who are very old and with risk factors for vascular disease -- may suffer transient cognitive decline after surgery," said Dr. Ola A. Selnes, a Hopkins professor of neurology and study co-author. But "this cognitive decline is generally mild and reversible by three months."
Your father's mental functionality should improve in a few more months barrring any further complications. Wishing you well!
Sorry to hear this news about your father. I went through this with my mom.
Did the doctors say if his heart is working as it should after the surgery? Has he had a CT scan of his brain? Is his liver okay and intestines? Sometimes what happens is the patient goes into cardic shock after surgery. This is where the heart is not pumping as it should and the organs start to shut down. Cardiac shock needs to be treated agressively at first. Is he cold to the touch? Ask his doctors what his medical diagnosis terminology is now?
Try to get some rest. I know how stressful this is. Make sure that you are eating and drinking. I remember I forgot to drink water for a few days and got dehydrated. Take care.