How Dialysis Works: Fluids and Wastes (Part 1)

If I have to say so myself, I think last night’s inaugural webinar was terrific. Although there were only about 45 people in attendance, everybody seemed quite engaged. We even had a couple of prominent nephrologists in attendance; one who will be recommending the series and the use of our platform to the International Society of Hemodialysis (ISHD).

In addition to getting other attendees’ opinions, I would like to see a discussion on the subject matter. Dr. Agar will be participating in any discussion we have. So if you have any questions you want directed to him, he will be happy to oblige. This is truly a great opportunity to learn more about the dialysis process and what it does inside the cells of our bodies.

Thise who weren’t able to attend can still see it HERE.

I agree Rich…all went very smooth and the implications and potential of such a format is actually mindboggling. Well done !!

Would like to know, if it was possible to compare a SDD tx with a nocturnal tx in terms of how much fluid one can comfortably remove, would nocturnal, given the longer, slower dialysis remove more fluid? For ex. let’s say I can remove 2.O with a SDD tx. Might I be able to remove .1 - .5 or even more additional fluid with a nocturnal tx considering the longer, slower tx with more time for the fluid to transport to the bloodstream?

Is a nocturnal tx comparable to Critline technology which in another kind of way helps stored fluid to release?


I dont want to prempt the 2nd half of the ‘How dialysis works’ series ‘Fluid and Waste’, the 1st half of which was ‘Wastes’ … or ‘Solutes’.

The 2nd half will be coming up sometime in June (date to be announced as it needs to avoid my leave later in June and early in July) and is titled ‘Fluid’.

Can I answer your question then - indeed it is the prime basis of the 2nd part of the whole talk and is aimed at providing you with a clear understanding of fluid dynamics and how this is very different in ‘fast’ (SDD) and ‘slow’ (NHD) dialysis.

So … this is NOT ducking the question, simply whetting your appetite for Part 2!

Actually, we may slot another topic in for late June and do part 2 in late July. :slight_smile: I had a question, though, John–does nocturnal HD remove P-cresol as well as PD does? If not, why not?

Dori & John,
I was not able to attend last night Webinar so watched it today.
Wow-- It was wonderful.
I can not wait for the next one.

Hi Pat,

That archive function is pretty handy, isn’t it? The next best thing to being there. :slight_smile: Glad you enjoyed it–and even folks who were there can go back as often as they like and refresh their knowledge.

Dori … the time slots changes are fine by me - whatever suits.

As for p-cresol … no. NHD wont remove p-cresol better than conventional dialysis … you see, p-cresol (a phenol(ic) waste) is a protein-bound waste. There are heaps of these with p-cresol only being a relatively easily measurable one which has had most of the airplay to date. Ray Vanholder and his team of very smart guys from Belgium has been the most active ‘player’ in this area Other examples of these tricky metabolic customers include the indoles and hippuric acid.

… Some may wish to google pprotein bound uremic toxins and will find the abstract of his paper in Kidney International (2001) 59, S266–S270 called “Protein-bound uremic solutes: The forgotten toxins” …

As current - emphasis on current - and commonly available dialyser membranes are designed and constructed specifically to prevent protein losses, anything that is naturally linked to (bound to the surface of) protein cant pass across the membrane. Its thus not dependent on time, frequency, blood or dialysate flow rate etc but on the properties of the actual MEMBRANE that separates blood from dialysate. In PD, that is a living membrane (the peritoneum) which allows the free passage of albumin (with a molecular size of 67000 dalton … thats big) while most HD dialyser membranes really really struggle to allow the passage of molecules even 1/6th that size. In PD, something bound to protein can pass through the peritoneum and away but in HD membranes - no such luck.

As I said, protein-leaky membtranes made with the help of nano-technology and purpose-made membranes by design are out there (I am not sure that your FDA has allowed you access yet in the US) and this may alter the p-cresol story in the future. We have trialled these in Oz and have been impressed with the ability to achieve some controlled protein-bound toxin clearance … but this is still early days.

For the moment, this protein-bound toxin issue may yet be one significant advantage PD’ers have over Hd’ers - but our knowledge remains scant and our experience even scanter!

One brief addendum to my last post … some protein bound substances do have a ‘free’ component … that means some BUT NOT ALL of the substance is protein-bound. In that event, the ‘free component’ may be removable and so SOME may be removable by current techniques … and there - depending on the substance - longer and more dialysis may be helpful (but only to an extent).

So, you see, it gets quite complicated! Depending on the ratio of ‘free’ to bound’ and depending on the size and transfer characteristics of the free molecule etc etc etc …

Ohhh, that’s very helpful! Some of the folks I know who’ve done the best with kidney failure for decades have switched back and forth between transplant, PD, and some form (usually home) of HD. This helps explain why that might be a good strategy–at least until better HD membranes are on the US market. Thanks–I learned something new!

I tried watching the recording but for some reason, the video which has Dr. Agar is out of sync with the slides.

I’m using Firefox on the Mac. Is this supported?


[COLOR=“Indigo”]It is 2AM and I am watching this recording in its entirety. It was fantastic to say the least. I can’t wait for the next one and I will do my best to be[ in attendance. Fantastic Job!/COLOR]

I must say that it is 2AM est. and I am watching this recording in its entirety. My opinion is that it was FANTASTIC and I am now upset with myself for missing it. I will do my best to be apart of the next one. It was wonderful! Very informative.