Broadly, we do not encourage more than small snacks during dialysis … and there is a physiological ‘reason’ for this …
It all has to do with the ‘splanchnic circulation’. The splanchnic circulation (splanchnic comes from the ancient Greek word to describe the ‘visceral organs’) is that circulation that supplies the gut and the abdominal organs.
When (or after) we eat, blood is diverted into the splanchnic circulation to aid in the absorption of nutrients from our bowel as the food we have eaten is munched up and acid-dissolved by our stomachs, squirted with bile and enzymes from the gallbladder (bile) and pancreas (enzymes) to break down the fats and sugars released by the munching and dissolving of the stomach, and then is milked by a muscular squeezing process along the many feet of intestine where the nutrients are absorbed into the blood stream of the splanchnic circulation. Finally, water reabsorption and mucous secretion in the large bowel formulates our final stool (poo) for elimination at the rectum and anus.
Phew … there’s our bowel function in a single paragraph!
Eating triggers a diversion of a significant dollop of our total blood volume to this circulation … a circulation that almost runs as a parallel but ‘segregated’ circulation from our ‘systemic’ blood flow … the blood that wooshes down into our legs and arms and that supplies our kidneys (if they are there!), our brains, our lungs etc.
Eating ‘compartmentalizes’ a significant volume of our blood for absorption … and makes it relatively unavailable for the systemic circulation.
This means that the blood volume that has been redirected to the gut is less available for dialysis! Dialysis can access the systemic circulation … but not the splanchnic circulation!
You may begin to see now that this reduces the potential efficiency of the dialysis treatment as a means to ‘cleanse’ the total blood volume.
There are also blood pressure implications that can arise from splanchnic diversion, with hypotension a more likely complication of dialysis therapy delivered to a patient who has eaten on dialysis than if no eating had been permitted.
A snack? … let’s be fair … a snack is ok – but make it very light, and make it of easily digestible food. If the patient isn’t desperate to eat, then not eating is ideal. If eating is essential (some patients just can’t hang that long without something to eat) … then small amounts.
As for a full breakfast? I’d not be so thrilled, if I were your physician, to encourage that. Anyway, I reckon it’d be more enjoyable to have a full breaky after dialysis, in the sun, together, with the morning paper, and without a bunch of tubes hanging from the arm!
As for your question of whether he should have his legs down or up during dialysis … this is a question that is of enormous interest to me. We published on this – or a parallel issue – back in around 2004 (in ‘Nephrology’) and again in 2007 (in HDI) … looking at the effects on the serum albumin and on volume of recumbent versus erect (seated) dialysis. It’s a complex issue. So complex, indeed, that it is a little over-complex to deal with here … suffice to say, it is a fascinating academic ‘ride’ to delve into this murky subject.
From a practical stand-point, while there do appear to be some circualtory ‘advantages’ from recumbent dialysis, I’d not be at all worried if he wants to plonk his feet down!
In Australia, almost all conventional dialysis is semi-recumbent, at best … and many dialyse seated with their feet down. I suspect (no, I know) that this is also the case elsewhere around the world.
If he wants to sit up a while … go for it. But … as his blood volume has been changing through dialysis, he may be more easily prone to a postural change (a fall) in his blood pressure when he sits up … so do it slowly … don’t make a too-sudden change. It may help avert an unexpected ‘flat’.
Im a bit concerned for his blood tests we drew today as he had his hefty-er breakfast during treatment. 