NxStage or Single Pass HD Machine?

Dr Agar, I have been on heamo dialysis for 4 weeks now and so far all is going well, my consultant has been very supportive and thankfully ensured my fistula was in place 9 months before use which has made it very strong. I have just started my training for home heamo in the UK.

I am to be offered a choice of a nxstage machine or a Fresenius 5008s machine. I am being trained in centre on the Fresenius machine and have preliminary been told that should I wish to use the nxstage I will need 5-6 treatments of dialysis a week. With the Fresenius machine I will have dialysis every other day. I am 107KG and do not have fluid removed at the moment. I have FSGS.

My question really is what is the difference between the two machines in terms of dialysis treatment. I know the Fresenius is HDF but I’m not too sure how this will compare with the nxstage.

I ultimately wish to do nocturnal dialysis as I have a young family and work full time. Are you able to give me any opinions on the pros and cons of each machine.

Also my local unit do provide some support with regards to the utilities cost but do you have any information on the water consumption of each machine and the electricity usage. I have searched the web but cannot find this info.

Thank you in anticipation of any information you can give me. This web site is an excellent source of information and has helped me gain a wealth of information.

Dear Steve

I am thrilled to hear you have started training for home haemodialysis … congratulations to your team for directing you to that option.

Here, in Australia/New Zealand where home HD is common, we have not, broadly, gone down the NxStage route. Indeed, after a brief flush of ‘trialling’ of the system in many patients in several states, it has been uniformly ‘shelved’ and use has stopped except in 2 or 3 patients in total.

There are a number of reasons for this … many - though not all - being contained in an answer I gave at this website to an earlier question from Kamal Shah in India along the same lines. I will copy an edited version this response below for you to read if you have not seen it …

[I]" I know some of you will have picked up that I am not fully convinced about the NxStage system … but why? Why has there been reluctance in my part of the world to accept this nice little portable machine?

Firstly, the NxStage was designed (primarily) for the US dialysis market, for a home HD market that it (the NxStage system) now has almost made its own - and spectacularly so.

There is no doubt at all that the NxStage system can take full credit for having grown home HD from ‘nothing’ to a now creditable 1-1.5% of all US dialysis. Full marks and all credit are due to the NxStage company that it has done so!

But, the NxStage was designed by a US team within the broad context of US dialysis which we here (and you over there too) believe principally provides fast (bad), hard (bad) and short (bad) dialysis. But, as the NxStage was designed for and ‘grew up’ in that environment, it was a system thus geared to also primarily deliver what we here consider as fast, hard treatment (= in my view, a bad principle). But, to be fair, it also opened up the capacity to in part offset this short dialysis profile by permitting more frequent dialysis (= a good thing) through the promotion of dialysis in the home.

To do this, but within the limitations of a small (portable) volume of bagged or batched ultra-pure dialysis fluid (the ‘ultra-pure’ bit also being a clear tick) - the NxStage system had to introduce a totally new dialysis concept that depended upon the reversal of the previously standard dialysis practice of using a high dialysis fluid flow rate (Qd) and low blood flow rate (Qb).

The NxStage system had to turn this long-standing low blood flow to high dialysis fluid flow ratio on its head … scripting instead a high blood flow to low dialysis fluid flow ratio. It named this the filtration fraction (FF).

In ‘conventional single pass’ dialysis, the blood flow rate (Qb) is commonly about half the dialysis fluid flow rate (Qd) … say, a Qb of 250 -300 ml/min paired with a Qd of 500-600 ml/ min. But, as the NxStage was (at least initially) limited to a 25-30 litre dialysis fluid batch – especially when they used the bagged dialysate fluid version in the 2004-2008 time period - and the system was RO-independent, a ratio reversal was their solution.

While the NxStage is no longer limited to a 25-30 litre dialysate fluid delivery system through bagged dialysate but has developed a now more commonly used on-line fluid generator (the PureFlow), it can still - at best - only offer a maximum dialysate volume per treatment of <60 litres. True, there has been a recent up-adjustment of that limitation to about 80 litres but that then also increases the cost of batching up 60-80 litres per treatment and this can become a quite significant issue.

To compensate for the very low dialysis fluid volumes that the system uses - and its associated low Qd - the counter-current pass of blood across the dialyser had to be ramped up! That forced a reversal of the Qb:Qd ratio such that Qb rose to be 2-3 x greater than the Qd … the very opposite of conventional dialysis where Qb is only 1/2 the rate of Qd.

The problem, for us here in ANZ, is that we think this only serves to rob Peter in order to pay Paul! While it reduces the need for a larger volume of dialysis fluid and allows bagged or batched dialysis fluid to replace RO-generated dialysate, it forces up the required blood flow rate and, by extension, the fistula blood draw and blood return rates.

To get anywhere near adequate clearance, the NxStage system and its blood/fluid flow dynamics requires a very high Qb … in turn demanding that the AVF be driven at flows that, to us here in ANZ is anathema.

We do not use or like using a high Qb. We think high Qb’s are detrimental to good AVF care. Using the kind of Qb needed to compensate for the low flow dialysis fluid rates of the NxStage simply, in our view, introduces another ‘bad’ thing into the dialysis equation.

Not only is a venous blood ‘blast’ back into the return vein of 350+ anathema to us, but to run a Qb of 350+, an arterial end ‘suck’ of the same amount is needed … with the potential (and actual) result of structural damage to the AVF the arterial end too - at BOTH ends - venous and arterial. [NB: see the later web reference (below) to my HDC blog on ‘Don’t flog the fistula’ for further reading about this]

To be plain, we don’t think that that is a good trade, if you don’t have to do it. And, in single pass systems, you don’t have to do it!

But, turning down the pump speed on a NxStage to 300-ish or, better, even lower (NB: our home patients on single pass systems run Qb’s of 225 ml/min) would cause the filtration fraction physiology of the NxStage principle to fail, and ‘adequate’ dialysis clearance would be unachievable.

So, for this, and other reasons, we have decided to stick with what we do … at least until newer, portables appear that allow low Qb’s yet provide for a high clearance by still allowing a high Qd.

Meantime, we remain comfortable in ANZ with providing good dialysis clearances yet at low pump speeds (low Qb’s) … using the single pass systems like Gambro/Baxter or Fresenius or Braun - or any number of other commercial single pass systems systems … and we are likely to continue to do so until something better is on offer.

Dialysis is, in essence, a trade off - as no current (or likely future) system is or will ever be ideal - but we believe it best to recommend to our patients to trade what is, in truth, still ‘difficult’ portability of a NxStage (for most) for better fistula care, and optimal small and middle molecular clearance. And, through recommending - wherever possible - longer dialysis (eg: not short sharp dialysis, but slow overnight dialysis), we ensure a low UFR (= a fluid removal rate that does not threaten myocardial perfusion and risk or cause myocardial stun, and which allows intra-dialytic trans-compartmental fluid equilibration …" [/I]

See here my blog on this issue … ‘Volume safe dialysis duration (VsDD)’ …at Home Dialysis Central …

See also my HDC blog on ‘The Dialysis Waterfall (Part 1)’ …

And ‘The Dialysis Waterfall (Part 2)’ …

And my HDC ‘Don’t flog the fistula’ blog…

As a final thought …

While I recognise that offering choice is important, and that the mobility of dialysis that is facilitated by the portability of dialysis equipment does matter to many. If this (mobility) is a major need … then the NxStage maybe the best and most viable option. But it is important, too, to make sure that patients who choose mobility understand that by doing so, they may sacrifice other benefits … and put additional pressures on their access.

The weakest link in life-sustaining dialysis is not the machine but the access. It is my view that access protection must be a paramount priority. I try to live and deliver that priority."

Other issues in machine choice

Other things matter!

Environmental issues clearly favour the NxStage and, if that is a major factor for you personally, the data suggests that the carbon footprint of a NxStage system used for 2-2.5 hrs x 6 times a week is about ¼ the carbon impact of a Fresenius system used for nocturnal dialysis (7-8 hrs x 5-6 nights a week) … and that ‘benefit’ will matter significantly for some.

The Fresenius 5000B HD/HDF dual mode system (= the one I think you are training on) is big. It clearly isn’t portable. It uses heaps of water = probably not a huge issue in supply in the UK(!) and power … and that may add significantly to utility costs - depending on local water and power costs etc. In ANZ, we reimburse for home HD water and power costs - in my own state, fully … in other states, variably. It depends on how successful the nephrology teams are at arguing the case with the relevant Health Department in their state.

On the issue of HD vs. HDF … we (Geelong) are currently switching our entire facility-based dialysis population off HD and onto HDF (½ are already switched and the other ½ will complete the switch by July) so, for you to have a Fresenius system that offers this capacity is, to my thinking, a forward step, even if at first you might use it in its’ HD mode.

Regarding water economy, we routinely reuse all RO reject water here – we have done so for more than a decade now. Most dialysis services in the UK also do this now and it is a huge plus in terms of water efficiency.

[I][B]Having just re-read this post for accuracy, I should qualify my last paragraph here, as many misconstrue what I mean by re-use! I find this is often misunderstood and while it is CLEARLY explained at our greendialysis.org website (see below), I will reiterate briefly here.

We re-use the reject water from the RO system … NOT the effluent from the dialysis machine, post-patient! The RO reject water, while classified as ‘grey water’, is in effect cleaner water than is the mains water that you and I drink and that is used to create the water used for dialysis.

The effluent from the dialysis machine and the patient is, as ever, sent to waste. That I have ideas around the re-use of even this currently discarded effluent fluid, these ideas remain for future research and as only a future potential.

As regards RO reject water, it is highly filtered and is - in effect - significantly improved from the mains water that is drawn by the filtration system in the 1st place. However, it does have a slightly higher conductivity than mains water. Despite this, the conductivity (effectively, it’s salt content) is still well inside the limits set by the WHO for drinking water, and many cities and populations all around the world use as their normal drinking water a water supply which has a higher baseline conductivity than does RO reject water.[/B][/I]

You will see UK data on green options - including water and power - at the NHS Green Nephrology site …

Or … you can take a look at our own Barwon Health ‘clunky’ but informative Green Dialysis site at …

NB … you will find plenty of data at our site on water consumption and power usage, among other eco-dialysis concepts that are our current interest here. Remember though that the data quoted is often dependent on local, state and national water and power regulations and pricing … so you would need to use the basic data but your local pricing structures to arrive at the right costs - for you.

Steve, that probably exhausts this answer which, while very long, will give you most of the information you seek.

Thank you very much for your reply. .