What Causes A Mild Stroke?

My husband just suffered a mild stroke. He has been on suboxone for 3 years now. He has not been given this medication in ICU and he's extremely anxious and antsy. I've told the dr and ICU nurse about this but I'm not sure they really understand what it is. He suffered the stroke on Friday, the ER doc gave it to him on Sat a.m. and said he didn't need to go thru withdrawals while trying to recover from a stroke. Then, when we were admitted, the hospitalist and ICU nurses say no suboxone. Please advise