Waking up after cardiac arrest? please answer!?

my uncle had to get surgery on his stomach for internal bleeding. after surgery he woke up and they took him off his breathing tube even though he still needed it. he went into cardiac arrest and they had to revive him. its been 4 days and he hasnt woke up. he has shown signs of movement and every once in a while he opens his eyes. he wakes up to cough and this happens pretty often. i noticed that when his daughter was talking to him that he started to open his eyes. the doctors said that they dont know if he will wake up. they said some people do and some people dont. do you know any ways that we can try to wake him up? he is on a ventilator and feeding tube. his heart rate and blood pressure are good. i just wanna wake him up. some doctors say that he should have woken up by now and some say that they put so much sleeping medicine in him that it takes 3-4 days to wear off and we are on day 4. how can we try to wake him up? we have been going everyday he has been there and staying all day. we talk to him and we dont leave him alone. could this be helping in letting him know that he is loved and that he is wanted here so he will try harder to wake up?