How does dialysis work?

The simplest description, if you remember your high school chemistry is, Osmosis. Wikipedia describes Osmosis as, “the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides.”

Basically the dialysis machine creates a disalate solution comprised of acid (very mild and smells like vinegar) mixed with Sodium Bi-carbonate and warm (body temperature) water (pure H2O having been purified by a water filter. The solution is then fed into the cylindrical filter that you can see on the side of the machine. The filter contains thousands of micro-fibres which form the membrane with the blood on the other side of the fibres. The toxins in the blood then pass through the membrane and into the solution which then gets flushed away into the waste system. The good stuff in the blood like calcium and iron etc do not get filtered out as those molecules are of a different size. The purified blood then continues on through the blood lines and back into my arm. The blood is mixed with a very slow drip dose of Heparin to thin the blood and prevent it from clotting. The Heparin is in a syringe connected at the front of the machine.

The disalate solution continues being fed into the machine as the blood continues to be pumped into the filter at a rate of 300ml per minute. This continues for five hours. If my maths are correct that means the dialysis is processing some 90 litres of blood each 5 hour session three times per week. That’s a lot of blood but it still doesn’t fully replace the function of the kidneys that work 24 x 7.

In addition to the above process I have a few other things that need to be done during dialysis:

1.     Each month I need to take a blood sample for tissue typing. This is fairly easy once I have the cannula connected to my arm I simply draw off a syringe of blood and inject it into a vacuum tube. I then deliver it to the Red Cross where they perform a white blood cell count and this is then ready for comparison with any potential transplant donor.

2.     Most dialysis patients also suffer a lack of iron and because they cannot absorb iron through the stomach or intra muscular the only way to get the iron is to infuse it direct into the blood stream. Each month I add a small vile of liquid iron into a 100ml saline bag which I hang on the machine and control the drip rate as it infuses into the blood line.

3.     The latest issue is my lack of energy caused by inability to create red blood cells. The red blood cells carry oxygen and without that I run out of puff very quickly. So I now need to stimulate the creation of red blood cells by, you guessed it, a weekly injection. Again the injection of Eprex can be done directly into the blood lines so that is quite easy. So far I have noticed any difference but its early days.

As you can see a 5 hour dialysis session is never dull and in the next post I will explain what happens when things go wrong.

When will you get a Transplant?

This is the most often asked question by people who know that I am a dialysis patient. The truth is I don’t know. Those on the waiting list don’t get a number in the queue and just wait your turn. Its not that simple.

Firstly, you have to get on the waiting list. Only those that the medical profession consider a good candidate get on the list. That’s about 10% of all patients doing dialysis. So let’s do the maths; about 15,000 dialysis patients Australia wide at any one time and growing means about 1,500 patients on the waiting list (and growing). With about 350 transplants performed Australia wide each year (growth rate not matching the growth in patients) that means about a 4-5 year on average. However, children under 18 years of age get preference and compatibility is the major criteria. I started Dialysis in Oct 2009 so Oct 2013 will mark four years.

To get on the list requires that you pass a battery of tests including blood tests, x-rays, ultrasound to ensure vascular system is ok and a heart stress test. Of course you have be a non smoker, not a diabetic and not obese. If you are on the list for more than two years they will probably repeat the tests to ensure you are still fit enough. Its worthwhile remembering that the expectation is that a kidney transplant will last 15 years and doctors like to achieve their KPIs just like other professionals. Many people are excluded from the waiting list because of other illnesses and while there is no official age cutoff, transplants after age 68 are rare.

Once on the list it then comes down to compatibility. Firstly the compatibility of blood type A, B, AB or O. It doesn’t have to be an exact match of A to A and B to B etc because it will also depend on a patient’s tolerance for the donor’s antibodies. So for example an A type can be compatible with an AB as long as there is a tolerance for the antigens. Also an O type donor is considered the “Universal donor” meaning they can donate to anyone. But because O type is rare such donors usually only get matched to O type patients. After blood type matching the next compatibility test is for Tissue Type (this is the white blood cells) and this is where my studies fail me as I don’t know how they compare white blood cells. For anyone who’s interested my blood type is A.

An increasing number of transplants in Australia are done from live donors. Either family or friends making an exceptional gift to a CKD patient. In these circumstances the live donor is thoroughly tested for general health and especially kidney health to ensure that a kidney donation will not have an impact on their health. Generally a person can live quite comfortably with just one kidney and most live donors have longer than average life span because their health is so good. Australia is also pioneering a cross donation approach where a family is willing and passes all the medical tests but is not compatible. They may find another willing donor in the same situation and but who is compatible with their patient and a cross donation can be arranged.  However, by far the most common transplant situation is where a donor is a deceased donor. So if you haven’t yet signed up as a organ donor please consider it now. Also don’t rely on just ticking the box on your driver’s licence. Log onto the Medibank web site and register formally as a donor and get an organ donor card to carry in your wallet.