HDF – A new and better dialysis?

There is a change blowing through the dialysis world.  Until recently, we BigD club members have belonged to either the haemodialysis branch, or the peritoneal dialysis branch.  But for some time now, there has been a third branch, HaemoDiaFiltration, or HDF and it may just be the leap in technology we have been waiting for.

HDF is a souped-up version of haemodialysis.  It has been around in Europe for many years, but until recently, it has been fiddly to set up and expensive.  But things are changing and most new machines will do either haemodialysis of HDF.

What’s the difference?

First a little theory.  We kidney-challenged individuals experience a constant build up of toxins as a part of everyday life (eating, drinking, exercising, etc,).  These would normally be extracted and excreted by our kidneys, but because they have left the building, we use dialysis machines to do much of this job for us.  The toxins come in two broad sizes: large molecule and small molecule.

A haemodialysis machine works by using pressure to filter water from our blood through a membrane (the “artificial kidney” on the front of each machine).  Once through the membrane, the water mixes with dialysate fluid on the other side.  At the same time, many of the small toxin molecules in the blood diffuse through the membrane into the dialysate liquid.  The dialysate is then discarded (and those little toxins with it).

Unfortunately, the large toxin molecules are too big to go through the membrane.  So they hang around, eventually doing damage.  One of the most famous is beta-2-microglobulin which builds up in the blood, forming a few very large molecules.  This is relatively common in older BigD members, who have been on dialysis for more than 5 years.  The result is pain, stiffness, and fluid in the joints (like my knee!).  About 50 percent also develop carpal tunnel syndrome.  No news there.

So what of HDF?  A HDF machine works in two ways.  First, like a haemodialysis machine, it removes small toxin molecules.  Second, it uses a more porous membrane to filter the blood, and a higher water flow on the other side of the membrane.  This has two effects: the membrane filters larger toxin molecules from the blood and the faster water flow draws more of the water from the blood, removing even more toxins.  It is a complex process because it removes a lot more water from the blood than is required to reach dry weight.  To offset this, the machine calculates and adds the required amount of replacement fluid into the arterial line before it reaches the membrane.  The new HDF – dialysis machines do this automatically.

The benefits of HDF are not immediate, and some medicos are sceptical, but if I have the choice between storing up large toxin molecules on haemodialysis or dumping them on HDF, I choose HDF.  Unfortunately, no treatment can get rid of the large molecules already embedded on my bones, joints and tissue.  But it will slow or stop more being added.  And people starting HDF BigD today, they may never have the problem.

HDF went out of fashion for the last decade or so because of the complexity and cost.  Technology improvements mean it is now on the rise many countries through Europe and in Australia (though not in the US where being more expensive that dialysis, it is virtually unavailable).

While it is more expensive, some dialysis organisations and units are beginning to offer it because it has the potential to dramatically improve the quality of life for BigD-ers.

My Diaverum unit is now offering it to everyone who meets what are fairly simple criteria: patients should be relatively young and be facing the prospect of long-term dialysis (ie, not getting a transplant within a year or two).  Most of us meet these criteria.  Currently they have only two HDF machines, so we will be sharing, but all replacements machines will be HDF capable.  So in a year or two, everyone will be able to have HDF on every run.

I have had all of one run on HDF, and all is well so far.  One big benefit is that HDF is much gentler on the heart, I had less of the last-hour nerves and didn’t feel quite so hyped up when I come off –  I slept well only an hour after I finished.   Some others in the unit have been on it for weeks and say they feel much improved, lower blood pressure, no jiggly legs and generally feeling healthier.  Whether this is real or imaginary, based on what they expect to happen, who knows?

I don’t know if this is a leap in technology, or a small step forward, but I look forward to finding out.

Dialysis: how often and for how long?

I’m still working on the BigD holiday arrangements. It’s slow, but looking good.  More soon.

In the interim, some news about dialysis times.

When I started the BigD in 1995, the standard was to dialyse three times a week for 5 hours per time.  I had known that dialysis was on the cards for me since 1972, when I damaged my left kidney in rough seas in the navy, and then discovered that I had only one (the right was missing in action since birth).

I hung on to my dwindling kidney function (via diet and good management by my nephrologist, John Dawborn) for 23 more years.  But I thought my life was over when I began treatment.  Five hours per time, three times per week was a real pain.  All that lost opportunity to do other things, getting restless and feeling unwell after the fourth hour and losing the rest of the day while I recovered.

Like everyone, I desperately wanted to reduce my hours.  My nephrologist held firm.  He was a great believer in the more dialysis I had, the healthier I would be, and 15 hours per week was his absolute minimum.

I regret to report that a new paper published in Medscape Nephrology on 27 December 2011, backs him up with evidence.  Written by Joel D. Glickman, MD, with the electrifying title Nephrologists Unite: Time to Put the ‘t’ back in Kt/V, it has some really interesting news for us BigD-ers.

What is Kt/V?  It’s a ratio indicating the efficiency of each dialysis session.  Put simply, it uses the speed your blood is pumped through the dialyser, and the length of time it is flowing, versus the amount of blood in your body (calculated by your weight) to estimate when you had have enough dialysis to remove the excess urea.  Completely clean blood throughout your body would be a Kt/V of 1.0, where the amount of blood cleaned equals the amount of blood in your body.  If you want to know more, see Wikipedia here.

But there are a couple of things wrong with using the Kt/V ratio to set dialysis time.

Firstly, kidney failure results in a lot of other toxins besides urea (including the so-called middle molecules).  Most can be removed, but efficiency of removal cannot be measured by Kt/V.

Secondly, for a range of reasons the theoretical 1.0 ratio cannot be achieved.  However many kidney organisations and specialists use Kt/V as an indicator dialysis efficiency.  For example, the US National Kidney Foundation Kt/V target is 1.3.

Unfortunately, over time the idea of this ratio has been reversed to:  “If you achieve a Kt/V of 1.3 over three hours, three times per week then you only need 3 three-hour sessions per week.”  Obviously BigD patients grabbed this news with both hands, because it meant shorter times on the machine.

But some nephrologists (like mine and JD Glickman) were sceptical.  Observational data clearly indicated there were benefits in longer treatment times.  Could this be proven?  Along comes the Glickman paper, with some alarming research stats.  Read the paper for details, but in summary, patients whose dialysis sessions were less than 3 hrs had a 60% increase in mortality. And life expectancy improves dramatically as the length of BigD time increases.

Pretty hard to argue with that: shortening your dialysis time shortens your life.  Or to take the positive view, more time on dialysis, more time on planet earth.

Glickman’s absolute minimum is 4 hrs, three times per week, a total of 12 hours – and longer if you can arrange it.

These findings make John Dawborn look pretty smart.  I have been on 15 hrs per week since I started.  And as I said, I really didn’t like it.

But then, a couple of years later he offered an alternative, which actually meant that we could both be happy.  I moved onto 5 days per week dialysis, with only 3 hours each time.  I have written elsewhere about the benefits of more frequent dialysis (which is also backed up by a steadily growing body of research).

I still dialyse for 15 hours per week.  But I can tolerate it, and I am well most of the time.  I still have things I would rather do, but with some planning, I can often do them while I am dialysing.

So, the bad news is that your BigD session isn’t going to get shorter any time soon.  The good news is (1) that you will live longer (for some people it will just feel longer), and (2) there is a way around those long hours and the roller coaster of three times a week.

Maybe it’s time you revisited how long and how often you dialyse?