Hi I have gone through your post, Low blood pressure during dialysis may be due to 1. Excessive water removal, than the weight gain between dialysis 2. New onset cardiac problem 3.if the patient is having any internal infection 4. If patient is taking BP medicine before going to dialysis Clearly may be any one of them If the BP is low , dialysis may not be adequately done.

It's okay . Nothing to worry. As u remove the fluid his bp would have come down. Make sure he doesn't go into too much hypotension. Kindly have a word with your nephrologost