Sleep Aids and Kidney Dialysis

My husband is on Kidney Dialysis. About 6 weeks ago he started taking a sleep aid before Dialysis in an effort get through it easier. Lately his blood pressure has been dropping dangerously low and they have to discontinue treatment. He is also sweating alot more than he used to during the treatment.at night he is having a hard time breathing while laying down. He had a heart attack and triple bypass a year ago. he hasn't mentioned the sleep aid to his doctor because he didn't think it was important. Could this be causing his difficulties?