Thanks for writing in.
I am a qualified and certified cardiologist. I read your mail with diligence. Good points are he is responding to painful stimuli and on CT there are no clots. Is there cerebral edema
(raised pressure within the skull) then he would be on treatment for the same. This type of complication is not unknown after open heart surgery when supply to brain is interrupted for some time during surgery and with the available facts it appears that he should come out of this stage. I am sure the treating staff will be taking good care to prevent infection and bed sores for that is one complication one has to prevent. Good Luck.
With Best Wishes
Dr Anil Grover