How Long Does It Take For A Dialysis Patient To Recover From Coma?

Hi there, my brother who is a dialysis patient for more than 2 years is suddenly in coma this time it's been 5 days in the hospital, his doctor said we need to let my brother to on dialysis everyday to recover, my question is the doctor saying the right thing, and how long would it takes for a person who is in coma to wake up if this is his case?
I beg thee to let me know about this, thank you!