Artificial kidney is the common name for the entire hemodialysis machine. One of its parts is the dialyzer. It's a device that people with kidney failure couldn't live without. It was invented over 100 years ago, and work is constantly being done to improve it. Scientists are constructing ever more efficient and smaller dialyzers. How does an artificial kidney work and what types of dialyzers are there?

Artificial kidney , ordialyzeris a device whose task is to replace the functions of this organ in people with chronic or acute renal failure. The kidneys play an extremely important role in the body: they remove excess water and are a filter that cleans the blood of unnecessary metabolic products, primarily urea, creatinine, and drugs. They also maintain acid-base and electrolyte balance, regulate blood pressure and even secrete hormones (erythropoietin). When the kidneys are sick, the whole body becomes sick. If they stop working, a person will be able to survive for a few days at most, because the concentration of the toxic substances will become more and more difficult to bear, the blood pressure will increase, the person will go blind, eventually fall into a coma and die. To live, he must have at least one functional kidney.

How was an artificial kidney discovered?

For patients with renal failure, a kidney transplant offers hope for a normal life. Waiting for him are reliant on the so-called artificial kidney. It all started in 1913 with three Americans named Abel, Rowntree, and Turner. They wanted to construct a blood filter device, but did not have the material. It was not discovered until the Second World War by a young Dutch physician, Willem Kolff - this material was cellophane, which made it possible to separate two substances, provided that one was larger than the other. Kolff placed blood with urea in a cellophane bag, and the bag in an aqueous solution of s alt with a concentration similar to that in the human body. Then he shook the bag, and after 15 minutes he checked the urea content in the blood. It turned out that all the urea penetrated the s alt water solution! It was a breakthrough discovery that led to the construction of the first dialyzers. Initially, they worked on a trial and error basis and were not without victims inover time, however, artificial kidneys became the basic tool that saved the lives of people whose own organs stopped working.

How does an artificial kidney work?

Modern hemodialysis devices obviously differ significantly from those designed by Kolff, but their basic principle of operation has not changed. The patient develops a venous-arterial fistula surgically or a catheter is inserted through which blood is introduced into the apparatus. There, blood pressure is stabilized and a special anticoagulant is added so that the blood does not clot. The dialyzer has the shape of a cylinder, inside which there are approx. 11 thousand. fine capillaries, i.e. thin tubes with a diameter of about 200-300 micrometers, made of a translucent film, e.g. cellulose, but also of other materials. Blood flows inside them (it can hold about 50 ml at a time), and outside there is dialysis fluid, prepared individually for each patient.

Urea and creatinine flow from the blood, where their concentration is high, to the fluid, where their concentration is low (initially zero), while the other properties of the blood remain unchanged, e.g. nothing important for life is lost proteins, ions and, above all, blood cells (because, according to the principle of diffusion, they should also try to be in a solution with a lower concentration). Water and electrolytes can travel through semipermeable membranes in both directions, so that their blood concentration remains unchanged. It is also important to remove excess water from the body. This is done through a phenomenon called ultrafiltration. Due to the increased pressure inside the tubes, the water is forced outwards and expelled.

Finally, the purified blood goes back to the patient's body, but before that, you need to stabilize its temperature and pressure and check for air bubbles. If detected, the system clamps the line and stops the pump. This is to prevent life-threatening air embolism. Dialysis takes about 3-5 hours and the patient has to report to the dialysis center 3 times a week. In addition, he can lead an almost normal life, work and study. Travel may be a limitation, although this can also be de alt with (the only issue is to locate the dialysis station and schedule the time for the procedure). People on dialysis must also follow an adequate diet based on low water and low sodium levels.

Worth knowing

Peritoneal dialysis

The dialyzer described above is used to perform extracorporeal dialysis, i.e. hemodialysis. But there is also the so-called peritoneal dialysis. The peritoneal membrane is used to filter the blood - thin and smooththe serosa that lines the abdominal cavity and covers the organs within it. Using the Tenckhoff catheter, which is placed permanently in the abdominal cavity of the patient (most preferably at the bottom of the peritoneal cavity - the so-called Douglas cavity), dialysis fluid (about 2 liters) is introduced into the peritoneal cavity and left for about 20-30 minutes. The contaminated fluid is then removed back through the same catheter. Most importantly, a person is not immobilized, and with proper hygiene, peritoneal dialysis can be performed alone, at home. Often, however, patients struggle with troublesome complications, such as peritonitis, infections in the catheter area and hernias. In addition, the filtration capacity of the peritoneal membrane decreases over time, and at some point you will have to switch to classical dialysis anyway. On the other hand, peritoneal dialysis saves blood vessels that will be needed later when hemodialysis is started.

Portable artificial kidney and other modern dialyzers

In Poland, over a dozen thousand people (in the world it is 13 million) live and function normally thanks to the fact that they report to a dialysis station for a procedure several times a week. It is tedious and exhausting. It should also be added that due to the increasing prevalence of diabetes and hypertension, the number of such people is still growing. Therefore, scientists are working on the improvement and minimization of dialyzers in order to improve the patients' quality of life as much as possible. There are already such devices, although still in the testing phase, that you can put on like a tool belt and walk with it. And scientists from the University of California are working on an artificial kidney the size that allows it to be implanted in the human body. They use live kidney cells, grown and tissue engineered into the device. They play a metabolic role and participate in the regulation of water and electrolyte balance. In this way, the artificial kidney performs the same function as the transplanted organ. The entire process is driven by the pressure of the blood flowing in the vessels. No additional pumps or external energy sources are needed. In addition, the patient is not forced to take immunosuppressive drugs. Let's hope that an implantable artificial kidney will soon become a viable solution for patients with kidney failure.

Category:

Urology and Nephrology