Can Person With Reflex Rate 3 And Dead Brain Cells Survive?

My friend drowned in swimming pool and he was inside water for 3 minutes. He was taken to urgent care center. For the first few hours, his body was responding but now he is in coma. The doctors say his reflex rate is 3. His brain is not responding to anything. Doctors fear that many of his brain cells are dead due to lack of oxygen. It is now almost 40 hours over. Please give me some suggestions. Is there any hope?