A great post, William!
And, the very first thing to say in repsonse is … I am very, very glad you are doing single needle dialysis.
I wanted to try to introduce it here (in Geelong) … indeed we (briefly) tried it some years ago in our home nocturnal patients.
So … why did our single needle effort falter? … in a word, noise!
When we first considered our home patients trying to use one needle and not two, the machines we used back then used a reverse flow, click-clack, ‘push me-pull’ you system which ‘clicked and clacked’ so loudly that the patients – wishing to sleep - all said ‘no thanks, no way’ and preferred two needles to one as a trade-off for silent dialysis. And – as a thought-extension from that – maybe we should try it again as the machines are now much more silent now.
In our experience, the noise is mainly from the R/O system and not the machine … so much so that one of our patients set up a ‘cottage industry’ and made sound-proofed boxes (air-cooled to avoid over-heating) to cover the R/Os! In addition, we try to site the R/Os through a wall away, separate from the dialysis site and dialysis machine.
I would, if I were on NHHD, chose single needle if I could.
While some might cite recirculation as a factor in single needle systems (1) this is less so in more recent system designs and, more importantly, (2) there is no issue with recirculation anyway in extended hour and higher frequency programs … none!
Even if there were to be a drop of +/- 5% efficiency with single needle dialysis from recirculation (old data, old systems), with home, overnight, long hour, higher frequency dialysis regimens, the 4+ fold increase in dialysis efficacy achieved by longer, better dialysis is vast in comparison to the small efficiency increment that might still be lost by recirculation.
… so it doesnt matter a jot!
As for your question about AVF survival and AVF complications …
The data (that is, what data there is) suggests that there is less physical AVF damage from buttonholing when compared to laddering. There is really no doubt in my mind – and I think this is supported by the limited studies and literature about this.
The incidence of aneurysm formation seems more with laddering than with buttonholing … but I think this may well be more to do with the direction of needle insertion used, and not the ladder technique per se … this is entirely opinion-based, not trial-supported fact.
Can I suggest you go to the HDC home page http://www.homedialysis.org/ and scroll down to the Webinar topics towards the bottom of the homepage. Click, if you have time to watch it and to be a bit bored in the process – I do rabbit on a bit – on the top Webinar on the list titled ‘Which way should needles go’ … it takes about 1 hour … as this Webinar does deal with a little of what you ask and will help you to understand what I have just said.
But … by far the greatest Achilles heel of needling in NHHD … and this seems mainly to do with buttonholes and not ladders … is the higher risk of infection.
‘Access’ is still, in my view, the weakest link in any dialysis system. In our preferred platform of nocturnal home haemodialysis – long, overnight 8-9 hr treatments 5 times weekly – each needle is in (1) longer (2) more often (3) down the same track (if using the buttonhole technique) and (4) can, if not meticulously stablised and anchored, potentially move within the track, even subtly, during side-to-side roll-overs or other movements during sleep
One needle vs two … in my view … should, at least theoretically, halve that risk. And that applies regardless whether that risk be buttonhole-related risk or ladder-related risk!
And there is a higher infective risk with buttonhole needling than with ladder needling. We have reported this, so have our Queensland friends and so has Andreas Pierratos’ group from Canada.
It is still less than with any form of central catheter access but it does appear consistently higher than with conventional care laddering. Not, I personally think, a reason to discontinue buttonholing in the long nocturnal patients – though some might disagree with that – but a problem to solve. The Canadians now routinely use Muprirocin to the button site. We have used Medi-Honey.
Which is right? Which is best? Either, neither or something totally different? I admit I don’t know. It’s a problem I think we have to solve, but not shelve.
But, on the other side of the coin, there does appear to be a greater risk and/or incidence of fistula wall damage and, especially, aneurysm formation with the ladder needling technique than there is with buttonhole needling. Again … is this the ladder of the needle direction? … that’s another uncertainty to work on solving.
Indeed, on my sabbatical in Seattle 2006, I worked – briefly – with the then CEO of Medisystems to try to dream up, design and develop a dual lumen, side-holed peripheral needle … akin to the design now current for central catheters but, rather, for in/out NHHD use in a peripheral AVF)
Sadly, it turned out that to make both lumens big enough to achieve adequate flows, the tensile breaking point of the steel needle was low, the needle too brittle, and because there was a risk of metal fatigue and/or structural fracture and needle tip disconnection during dialysis … the idea was shelved and I (and he) turned to other things.
Still, though, it is a one-day hope …
At the end of the day and in my view, use one needle and half the risk of infection. OK … maybe trite and too simplistic? … perhaps … but it makes theoretical sense (to me, at least)!
As an ‘on-thought’ from that, use one needle and the ladder technique and with (always) only an antegrade insertion direction (why would you ever do otherwise), and you should reduce infection even more than using a single needle and a button.
So … more strength to you for using a single needle for your nocturnal dialysis. You have sparked (or, better, re-kindled) my own thoughts/interest in this … so. I’ll keep you posted!