The reason dialysis patients are advised to limit their fluid intake (we can't force them) has to due with one of the main goals of dialysis; why do we do dialysis?
It's not uncommon for diabetics to become hypoglycemic during dialysis. The glucose is not dialyzed off so we're not really sure why this happens. I think one theory has been that the erythrocytes "eat up" excessive glucose due to the pH changes that occur during dialysis.
The reason the patients have a fluid restriction is firstly a lot of dialysis patients do not urinate or if they do it is a small amount. There is a build up of fluid within the body.
If patients drink excessively or eat foods which contain a lot of fluid then the fluid has no where to go, except to stay within the body causing problems.
You see a lot of patients with Congested Cardiac Failure if there fluid is not removed, this increases the problems their heart already has to deal with.
Think of your systems, what happens if fluid builds up within the body? Obviously the heart suffers first but excess fluid can effect so much more. Go back to your basic A&P
Fluid restriction is because, as madwife stated, they do not urinate or very little. They come to us to have it taken off. No that does not mean on dialysis days they can drink more before going or during. And yes, some patients come back and request more fluid to be taken off because they want to drink more.
I'm not sure about the diabetic one. There is glucose in our dialysate, so blood glucose levels can actually go up, if they are low on HD. I know some have to eat because they received coverage by the floor nurse anticipating that the patient was going to eat. I wouldn't do it, but I've seen it happen.