Joe (not his real name) has just been through what we all dread: an infected fistula, with complications.
Most of his fistula is in his upper arm, and over the last couple of weeks it became sore, larger and more difficult and painful to needle. Joe started antibiotics, but unbeknown to him, it had also developed a clot that grew in size until the blood flow through it was minimal. So, though he was on the machine for the same time each session, less blood being cleaned meant he was actually getting less and less dialysis and becoming less and less well. Realising that it was not just because of the infection, he was referred to his kidney specialist for treatment.
The treatment for a fistula blockage can be complex and usually involves several steps:
- Joe goes to hospital where they to put in a permcath to replace the fistula. A permcath is a flexible tube that is connected into a vein in his neck; it has two inner tubes, one to take blood to the dialysis machine the other to return the blood to Joe
- The unit dialyses Joe via the permcath
- Once he is healthy enough, Joe returns to the hospital so that the vascular surgeon (the guy who created the fistula) fixes the problem by opening it up, cleaning out the blockage and closing it up again
- Joe then returns to the dialysis unit, where they continue using the permcath until his fistula is healed and ready to resume duty
- Joe then has the permcath removed.
However, Joe couldn’t get a permcath fitted immediately because his blood chemistry had fallen to a point made that made surgery unsafe (too much potassium, endangering his heart). The only solution was for Joe to have more dialysis until his blood chemistry was OK to proceed. Since not being able to dialyse properly was the problem in the first place, it sounds like Joe was caught in the crazy circle of Catch22.
But there was a solution: Joe would dialyse using the Single Needle Dialysis technique (What? Sounds like a quiz question for medical geeks: How can you dialyse with only one needle?)
The Single Needle Dialysis technique is a fiendishly clever system where only one needle is inserted into the fistula. The needle is connected to a Y-shaped tube, with the tops of the ‘Y’ outlet connected to the arterial and venous dialysis lines respectively (see the picture of Joe’s arm).
Most of the clever stuff is then done by the Dialysis machine, which uses two pumps (rather than the usual single pump in traditional Two Needle Dialysis) and a holding chamber. One pump is for the arterial line, the other for the venous line. They operate in sequence over a cycle (a little like a car engine) this way (see the video):
- In the first part of the cycle, the venous line is clamped shut and the arterial pump draws blood from the body, passes it through the dialyser cell and into the holding chamber. It does this for 10 seconds
- Then the arterial line is clamped shut and the venous pump draws the blood from the chamber and returns it to the body at a slightly faster pump speed, for a little under 10 seconds (the faster the blood is returned, the less recirculation and the sooner a new arterial phase can begin)
Then the cycle starts again.
Single Needle Dialysis works so well that for many people (especially small people and children) recirculation is less than 10 per cent (the same as traditional dialysis) and there is minimal reduction in dialysis efficiency. For this reason it is often used for children when they only need dialysis short term. It reduces the level of invasion into their bodies, as well as the mental trauma.
Not many units around here can do Single Needle Dialysis, but our unit can (it is pretty simple using the new Gambro Artis machines), so Chris arranged for Joe to move to our unit for the treatment (hence the photo and video!).
After about two weeks Joe’s potassium level fell to where it was safe to have the permcath put in and his fistula surgery. Now, normal dialysis via the permcath is going well and he is slowly recovering his health. Once the fistula has healed, all will be back to normal. Not a pleasant experience, but Joe is an upbeat guy the and worst is over.
Single Needle Dialysis is interesting. It was first attempted 50 years ago, in Holland, using a single pump and a time-activated switch opening and closing a double clamp. It was complex and difficult to set up and its use was limited to highly trained staff during emergencies. Then in 1980, a couple of Belgian doctors developed a double pump system, the precursor of the one used for Joe.
In his 2013 paper, Dr Guy Rostoker, MD, PhD wrote that tests using the double pump Single Needle system showed “…that dialysis efficiency was at least as good as with conventional double-needle (DN) hemodialysis. However Single Needle dialysis has failed to gain popularity, except in Belgium, the Netherlands, Luxembourg and recently Asia, because many nephrologists and dialysis nurses are reluctant to use it, even in cases of difficult fistula access, for fear of incidents or under dialysis.”
With the new generation dialysis machines like the Artis, the potential for Single Needle dialysis incidents is falling rapidly. However, the potential for under dialysis is still there, since during each dialysis session, the blood is being filtered for only a little more than half the session time, because the arterial line is clamped each time the venous line returns our blood to us. This implies that to move to a single needle, we would need either longer sessions or a session every day.
So I won’t be pushing to move to Single Needle dialysis any time soon, but I’m very glad to know it exists as a backup during emergencies. And I think Joe is too.