Name: Matthew Boo Han Wee (13)
Class: 1i2
The Dialysis Process
Dialysis is a process of purifying a patient’s blood whose kidney is not functioning
properly by removing waste and excess water from the blood via a machine, then returning the
purified blood to the patient. The word dialysis is actually made out of two sub-words, namely
“dia”, meaning through, and “lysis”, meaning loosening.
The first experiments with dialysis were performed using a dog in 1913. John J. Abel, L.
G. Rowntree, and B. B. Turner built a machine that pumped blood through a semi-permeable
membrane with a tube submerged in a special dialysis solution. However, there was a problem.
Since blood usually clots to stop bleeding after a while, the dialysis would soon be interrupted
as the blood of the dog would clot halfway through the process. So, not many advances in
dialysis were made until heparin, a chemical which prevents blood from clotting was discovered.
(Heparin was discovered by W. H. Howell in 1922.)
In 1943, Willem J. Kolff built the first dialysis machine that could be used by humans.
However, at that time, as resources were scarce, (as it was during the World War II) Kolff had to
improvise and build the initial machine using sausage casings, drink cans, a washing machine
and various other items that were available at the time. In the next two years, Kolff tried to
treat 16 patients with kidney failure with his improvised dialysis machine, but the results were
unsuccessful. However, in 1945, a 67 year old woman with kidney failure regained
consciousness after Kolff had used his dialysis machine on her, and lived on for another seven
years before dying of an unrelated condition. She was the first ever patient who was
successfully treated with dialysis, and modifications to the dialysis machine soon produced a
smaller, more effective dialysis machine in 1947.
Patients who go through dialysis are usually people without kidneys or people with a
kidney injury, kidney disease or kidney failure. Dialysis is generally used as a temporary
measure to keep patients with the above ailments in good health until a kidney transplant can
take place, or as a permanent measure for patients who are not in good health condition or do
not want to go through the transplant.
The kidneys play an important part in maintaining good health. When the kidneys are
healthy, they ensure that the body has enough water and minerals in the bloodstream. The
substances which the body cannot get rid of via respiration are excreted through the kidneys as
urine. The kidneys also produces a hormone called erythropoietin that makes red blood cells
and produces a substance called calcitrol that plays a role in bone formation. Even though
dialysis can purify the patient’s blood successfully, dialysis cannot completely replace all of the
functions of the human kidney as the process of dialysis does not produce erythropoietin or
calcitrol.
Dialysis is performed by bringing the blood into contact with a semi-permeable
membrane with a sterile solution on the other side by piercing a hole in the patient’s blood
vessel (usually in the arm), and pumping the blood towards the membrane. However, since the
patient’s blood will naturally clot after a while, heparin is pumped into the body to stop the
clotting and continue dialysis.
Diffusion and osmosis occur in dialysis. As substances spread from a place with a higher
concentration of itself to a lower concentrate of itself, the dialysis solution on the other side of
the semi-permeable membrane (which contains the fresh dialysate) has levels of minerals
like potassium and calcium that are similar to their natural concentration in healthy blood to
prevent these diffusible substances like water that are needed by the body are not removed by
the membrane. Also, because of diffusion, the unwanted substances in the bloodstream (like
urea) will be filtered to the other side of the membrane (in the used dialysate), and hence the
purification takes place.
However, since the body’s blood cells and platelets are too large, they will not pass
through the semi-permeable membrane. Before the purified blood is returned to the patient, a
chemical called protamine which deactivates heparin is added to the bloodstream. Dialysis is
then repeated several times a week, a few hours at a time, to ensure that the body's internal
equilibrium of water and minerals are not upset, and that the waste substances in the blood do
not accumulate in the body.
How dialysis occurs
A dialysis machine
References:
http://www.discoveriesinmedicine.com/Com-En/Dialysis-Machine.html
http://en.wikipedia.org/wiki/Dialysis
Pictures:
http://en.wikipedia.org/wiki/File:Hemodialysismachine.jpg
http://en.wikipedia.org/wiki/File:Hemodialysis-en.svg
Reflection
I feel that dialysis is very important to medical science nowadays as the dialysis machine
has saved a lot of lives. As dialysis can function as an artificial kidney, thus acting as a temporary
measure before a kidney transplant, it could save a lot of lives as finding a suitable kidney for a
transplant could take very long to find.
Our kidneys are very important to us as they purify our bloodstream. If too much
unwanted waste builds up in the bloodstream, the waste could clog up the bloodstream,
resulting in death.
I feel that it is important to know about the kidneys as if you know the function of the
kidneys and how important the kidneys are, you will value them more and take care of them
well.