Methods for purification of colloidal systems: dialysis, electrodialysis, ultrafiltration. Physical and chemical principles of functioning of an artificial kidney

artificial kidney

A few years ago, a tragedy broke out at the Institute of Chemistry at the University of Vienna. The student complained to his friend about a severe headache.

So take your headache medicine," said his comrade, "I have a pill, swallow it.

The student followed the advice, took a pill, and soon became seriously ill. A friend gave not a remedy for a headache, but a sublimate tablet, which he happened to have. As you know, the mercury compound, sublimate, is an extremely strong poison. It affects the kidneys, and if a person has taken a significant amount of this substance, with severe mercury poisoning, he soon dies of kidney failure, as they lose the ability to remove substances harmful to the body from the blood. But now, in cases of severe mercury poisoning, a person can be saved if an artificial kidney is turned on in a timely manner. For several years, medicine has had equipment that is quite rightly called an artificial kidney, since for a certain time it can replace a kidney and do what a natural kidney does: remove toxins from the blood - toxic substances that arise in the process of life. Every student knows that semi-permeable biological membranes have the ability to pass substances dissolved in a liquid, salts, if there is another liquid separated only by the membrane, in which there are fewer salts than in the first, until an equilibrium is established in the concentration of both solutions. In the body, the network of the smallest blood vessels and the network of the smallest urinary tubules are at the same time receptacles for fluids and membranes. On one side there is blood in small blood vessels (capillaries), on the other - the thinnest urinary tubules. Only substances harmful to the body, that is, primarily urea and uric acid, pass from one network to another, while useful substances, such as blood sugar, are retained under normal conditions. Such is the biophysics of the kidney, and if due to some disease this filtering system stops working, in our time it is possible to turn on another, artificial kidney, which has already won an important place in medicine.

The artificial kidney is built according to the pattern given by nature. Creating a suitable model, of course, was not easy. The main task was to be able to free the blood from harmful substances without harming itself. It was necessary to remove the blood from its channel, free it from urea and other harmful substances, and then again direct it along the channel. After all, the blood had to continue to circulate in the body and deliver to the organs, primarily the brain and heart, the substances necessary for life, without coagulating in this artificial kidney and without forming clots.

Based on these basic requirements, scientists set about creating an artificial kidney. This happened several decades ago. As early as 1913, Abel, Rowntree, and Turner were experimenting on animals and testing the apparatus they had built. Shortly thereafter, in 1928, Haas applied a similar model to humans. Satisfactory results were obtained when French scientists took up this problem.

In the famous Parisian hospital "Hotel Dieu" they used an apparatus equipped with a drum, which was built during the Second World War by the Dutchman W. Kolff. It consists of an enameled metal vessel with a capacity of one hundred liters. A wooden cylinder rotates in it, wrapped with tubes, the total length of which is 40 meters. The tubes are made of cellophane, and it must be said that the solution to the problem of an artificial kidney could only be approached after cellophane appeared. It is a material suitable for the manufacture of membranes: it is impervious to liquids and permeable to salts almost to the same extent as natural membranes, like capillary blood vessels and renal tubules, like the peritoneum of animals and humans, which at one time was tried to be used to create an artificial kidney. .

Cellophane is used in all the latest artificial kidney models. The model built by the Americans Schatz and Bergman, doctors from St. Louis, has a thin cellophane tube more than 20 meters long and with a capacity of about 0.75 liters. This tube is wrapped around a wire cylinder with fine loops. The cylinder is immersed in a plastic vessel filled with a solution of salts and sugars intended to replace the toxic substances contained in the blood. Blood is usually extracted from the large veins of the thigh and distilled with a pump into a plastic tube, and then reintroduced into the vein of the patient's arm. The entire blood purification procedure lasts about ten minutes.

To prevent clotting, heparin, a substance extracted from the liver, is added to the blood.

A little sugar is also added to the diffusion solution so that it passes into the blood when toxic substances leave the blood through the smallest pores in the cellophane. This exchange occurs until the same concentration of salts and sugar is established on both sides of the membrane, that is, in the blood and in the diffusion fluid.

It is rarely possible to get by with one procedure for such an exchange; in most cases, several procedures are necessary to free the blood from poisons.

Further, it is important that the cellular elements of the blood are not damaged. Red blood globules are very sensitive, easily stick together in piles or simply collapse. Practice has shown that cellophane tubes do not destroy red blood cells. The washing liquid, in addition to sugar, of course, must also contain salts of sodium, potassium, calcium and others. If this condition is not observed, the blood would be depleted of salts, since the essence of dialysis is that the same concentration of salts is achieved on both sides of the membrane.

At present, the artificial kidney has become an indispensable auxiliary device in the clinic. It is needed in cases of acute kidney failure, when the doctor's task is only to keep the patient alive for a few days, until his kidneys, hopefully, recover and can again take over their function. This happens primarily with certain poisonings, but kidney failure, which threatens the life of the patient, also occurs with some other diseases.

Here is a case of kidney failure due to poisoning. The young doctor made experiments on himself, investigating salt metabolism. Once he made a mistake and took the highly poisonous sodium chlorate instead of table salt (sodium chloride). A few hours later, his condition deteriorated rapidly, and a blood smear showed red blood globules sticking together and dissolving. The next day, an artificial kidney was used to save the patient and dialysis was performed (the exchange described above is called that).

This procedure was repeated twice more, since the patient's kidneys began to function only after ten days. He began to recover rapidly and made a full recovery after a month's stay in the hospital.

In Vienna, a few years ago, another very instructive case was observed. The kidneys suddenly stopped working in a man who was bitten by a rat. He was saved with an artificial kidney.

Treatment with an artificial kidney was first performed in Vienna in the spring of 1953. Then this method was just beginning to be used, and it took some time for this method to take root. But its value for a large hospital is clear from the fact that in the Vienna clinic for ten months (1962-1963) an artificial kidney was used in 16 cases. Eight patients were saved, eight died, despite the repetition of this procedure, but it is certain that without the use of an artificial kidney, all 16 people would have died.

In Western Europe, one of the first artificial kidneys appeared in Freiburg. It was built by engineer Halstrup in collaboration with doctors. At the beginning of 1954, it was first used in the medical clinic of Professor Sarre on a twenty-year-old patient. He was admitted to the clinic for poisoning; his kidneys soon began to function and he was saved. In reporting this case, Prof. Sarré stressed that an artificial kidney should only be used in acute kidney failure; in chronic shrinkage of the kidneys, it cannot help, the process continues, and the exchange and removal of toxic substances from the blood do not help the patient. At present, this is known to everyone, but such a limitation in no way detracts from the value and value of an artificial kidney. Suffice it to recall the many unfortunate people whose kidneys were so damaged by the poison that they suddenly stopped working, but were still able to recover, thanks to which their lives were saved.

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Kidney right Pain from the side of the kidney with light tapping with fingers, white coating in the urine (sometimes with blood), sweating of the palms of the hands and feet (especially the fingers of the right hand), the right hand sweats more than the left, her palm is more red. Excessive sweating of the body after eating and during sleep,

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Kidney left Pain from the side of the kidney with light tapping with fingers in the place where it is located; a white coating appears in the urine, sometimes blood; palms and feet sweat, especially of the left arm and left leg. The edematous sac under the left eye is more pronounced than under the right; left


Undoubtedly, the creation of the "Artificial Kidney" device is a real revolutionary breakthrough in the creation of perfect methods for the treatment of CRF, but patients on hemodialysis, alas, cannot live a full life. They have to go through this complex procedure for life and quite often (and sometimes daily), which means that they are forced to be "tied" to the city that has special equipment for dialysis and experienced specialists.

Connecting to an "artificial kidney" and dialysis procedure

For some patients, the only way to prolong life is treatment with the Artificial Kidney, but many have no idea what this type of treatment is.

"Artificial kidney" is a machine weighing about 80 kg, which works like a pump, taking blood from the patient and returning it back after cleaning.

Purification is carried out when blood passes through a special device - a dialyzer.

The principle of operation of the "artificial kidney" is as follows:

  • The dialyzer consists of a large number of tubes (capillary type), through which the patient's blood flows, outside these tubes are washed by a special dialysis solution. The wall of these tubes consists of a semi-permeable membrane, through which harmful substances and excess trace elements from the blood enter the dialysis solution by osmosis and diffusion.
  • After that, the dialysate is drained and continuously replaced with new one.

With the help of an “artificial kidney”, the hemodialysis procedure (the name of one of the common blood purification methods) usually takes from 3 to 5-7 hours.

If the patient suffers from CRF, then usually the dialysis procedure with an “artificial kidney” is performed 3-4 times a week all the time. If the patient has developed (acute kidney injury), then the procedures can be carried out even daily until the symptoms of intoxication are eliminated and the independent functioning of the kidneys is restored.

When connected to an "artificial kidney", hemodialysis procedures are carried out in special departments and centers of nephrology and hemodialysis.

The procedure is performed by a nephrologist, sometimes a resuscitator. The selection of patients for treatment on the device "Artificial kidney" is carried out carefully. This method of treatment is revolutionary in the treatment of chronic renal failure, however, not all patients have a cloudless life on hemodialysis.

Lifelong attachment to the device and drugs, the severity of comorbidity, as well as the emergence of new complications associated with hemodialysis, sometimes create serious problems in the quality of life of these patients. Often they are hardly accepted for the treatment of concomitant pathology by doctors of other specialties, who, due to the uniqueness of the pathology and the method of treatment, are not always informed about the features of the treatment of these patients.

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An artificial kidney is a device for purifying blood plasma. It is used when a person's own organs cannot cope with such a function.

artificial kidney

The process of hardware blood filtration is called hemodialysis.

This procedure is extremely important. It allows you to gain time for the selection of the optimal treatment regimen, with its help it is possible to increase the life of a patient with chronic renal failure by decades.

human kidney

The functions of the kidneys are diverse, they affect the vital activity of the entire human body. They carry out:

  • purification of blood plasma from metabolic products and decay of foreign compounds that have entered the body, for example, drugs;
  • maintaining a constant concentration of all electrolytes (potassium, sodium, chlorine, magnesium, carbonates, calcium);
  • regulation of blood pressure by removing excess fluid and electrolytes from the body;
  • maintaining a constant level of intercellular and intracellular fluid in all tissues of the body, this ensures the constant and stable operation of organs and systems;
  • the secretion of biologically active substances of renin, which is part of the renin-angiotensin-aldosterone system and is involved in maintaining a constant blood pressure, and erythropoietin, which plays a key role in the formation of red blood cells - erythrocytes.

The kidney can maintain its functions even if only a fifth of the total number of cells in it - nephrons - work.

If one kidney “failed”, then the other is able to almost completely compensate for it.

The situation develops much worse when both organs are affected. At the same time, to maintain life, a person needs a hemodialysis machine, which is also called an artificial kidney.

The syndrome of chronic or acute renal failure can lead to such an outcome.

kidney failure

According to the nature of the course, two forms of this syndrome are distinguished: acute and chronic.

Acute occurs against the background of:

  • abrupt cessation of blood circulation as a result of acute bleeding, heart failure, traumatic shock and similar conditions;
  • fleeting autoimmune lesions of the structure of the renal nephrons;
  • poisoning with toxic substances, such as mercury compounds, bismuth, alcohol, barbiturates, mushrooms;
  • acute allergy to drugs, usually such a reaction of the body occurs after taking antibacterial agents;
  • spontaneous obstruction of both ureters by stones, blood clots, the risk increases many times if a person has only one functioning kidney.

This syndrome threatens the life of the patient and requires immediate medical attention. Time to determine the diagnosis and start therapy gives a hemodialysis machine or an artificial kidney.

Subsequently, the manifestations of this condition are stopped by medications and the underlying disease is treated.

The device for artificial dialysis is widely used to prevent irreversible systemic disorders in the development of chronic renal failure. This syndrome occurs against the background of such pathologies:

  • prolonged inflammatory processes in the kidneys (glomerulonephritis or pyelonephritis), which affect the renal parenchyma and the nephrons located there;
  • diabetes;
  • congenital or acquired disorders of kidney development, for example, hypoplasia, polycystic, oncological formations;
  • long-term chronic congestion in the pyelocaliceal system due to hydronephrosis, nephrolithiasis, tumors of the urinary tract;
  • systemic connective tissue diseases that cause kidney damage.

This is a two-way process, in addition, the disease that caused chronic renal failure is often not treated. Therefore, the only way to prolong the patient's life as much as possible is with an artificial hemodialysis machine.

Artificial dialysis is the purification of blood plasma from excess fluid, electrolytes and toxic compounds. It can be carried out both in a hospital setting and at home.

For this, a special device is used, which is called an artificial kidney.

The operation of this device is based on the interaction of fluids on both sides of a partially permeable membrane, which is washed by blood flow on one side and a special solution on the other.

Due to the pressure difference on both sides of the membrane, excess liquid, slag and other compounds are removed. The necessary substances enter the blood from the dialysis solution.

artificial kidney

The component composition of the solution with which the hemodialysis machine is filled is determined by the attending physician, depending on the general condition of the patient.

An artificial kidney consists of three main elements. These are blood supply equipment, a device for preparing and supplying dialysis solution, and a dialyzer.

Blood enters the dialyzer through special tubes using a pump. Devices for determining blood flow velocity and pressure are connected to this system.

The pre-prepared solution enters the apparatus from the reservoir. It flows in the direction opposite to the flow of blood. This solution is very similar in composition to plasma, if necessary, the concentration of electrolytes in it is changed.

This regulates the level of fluid excreted from the body of the patient.

Scheme of the procedure

The frequency and duration of artificial hemodialysis is determined separately for each patient.

The apparatus for artificial dialysis is designed in such a way that it is possible to install various types of membranes into it. Depending on this, daily short-term dialysis can be carried out, which lasts about 2 hours.

Carrying out procedures

With partial functioning of the kidneys, two procedures per week for 5-6 hours are sufficient. However, the most common is the scheme in which the patient is connected to the device 3 times a week for 4-5 hours.

The patient is connected to the artificial kidney through a specially formed fistula. Its formation is carried out during a surgical operation on the vessels.

Contraindications for hemodialysis

There are quite a few contraindications to blood filtration on an artificial kidney. So, hemodialysis is not performed on patients older than 80 years.

Contraindications

This procedure is dangerous for coronary heart disease, cerebral circulation disorders, viral liver diseases, pathologies of the hematopoietic system, diseases of the nervous system, mental disorders, incurable cancerous lesions of the body.

Patients older than 70 years with concomitant diabetes mellitus are also excluded from the hemodialysis program.

With caution, the procedure should be carried out if a person has tuberculosis or other obstructive pulmonary diseases, as well as at the risk of developing spontaneous bleeding.

Complications

After hemodialysis on an artificial kidney, jumps in blood pressure, nausea, vomiting, and heart rhythm disturbances are possible.

Usually after the first procedures there is a feeling of deafness, confusion. In more rare cases, muscle cramps begin.

The most formidable consequences of the procedure are associated with open access to the patient's vascular system. Therefore, the condition of the fistula and installed catheters is monitored with particular care.

In parallel with hemodialysis, obligatory observance of a sparing diet is shown. The use of foods high in potassium and phosphorus is not recommended. These are dried fruits, dairy products.

To correct electrolyte metabolism, appropriate medications are usually prescribed.

Drawing up a diet, the decision to take various multivitamin complexes must be agreed with the doctor without fail.

It should be noted that the hemodialysis procedure is used relatively recently. In our country, it has been used only since the late 50s.

Currently, the device and functions of dialysis equipment are adapted to support not only life, but also the preservation of the patient's ability to work.


With proper implementation of all the doctor's recommendations on an artificial kidney, a patient with chronic renal failure can live 25-30 years of a full life.

Severe renal disorders often force doctors to turn to modern technologies and methods of treatment. An artificial kidney is a unique device that can qualitatively improve the patient's condition with severe chronic or.

The introduction of this technology into the body makes it possible to eliminate poisonous toxins, excesses of alcohol intoxication and even narcotic elements from this fluid without disturbing the blood volume.

general information

Violations provoke a massive attack of foreign harmful substances for the body - toxins, decay products, external poisons and other irritants. With the accumulation of these negative elements, a severe irreversible condition often sets in, the human body is not capable of overcoming it on its own. The end result of prolonged poisoning is death.

What does a hemodialysis machine look like?

The achievement of medicine in 1913 was the invention of an artificial apparatus, reminiscent of the functionality of a healthy paired organ. The treatment process was called hemodialysis.

A modern reflection of this technological miracle of medicine is an automated universal system for restoring the qualitative composition of blood, and the device is characterized by a complex effect on harmful blood elements.

Functionality of hemodialysis

A gradual increase in the concentration of negative substances in the blood provokes the extinction of the brain, this is due to a strong decrease in the ability of red blood cells to deliver oxygen. To save human life, doctors connect artificial kidneys to the patient.

The hemodialysis procedure resembles the usual filtering of fluid through a specific membrane, the composition of which is very similar to the structure of a normal kidney.

An artificial kidney does an excellent job of removing the following elements from the blood:

  • substances of protein metabolism - various compounds of their urea;
  • creatinine is the simplest chemical breakdown product that occurs in muscle tissue;
  • all kinds of toxic compounds: mercury molecules, chlorine, poisonous arsenic, toxic compounds;
  • composition of the pharmacological and narcotic group;
  • alcohols;
  • excess fluid.

In medical practice, both complex professional devices and devices of a narrow focus are actively used, however, the principle of operation of various models is based on general provisions.

The device must consist of the following elements:

  • detailed monitor with many modes;
  • dialyzer - used filter;

What does the dialyzer look like?

  • advanced technological models are equipped with a perfusion module, it is responsible for the movement of blood inside the dialyzer;
  • the artificial kidney is additionally equipped with a device for preparing and delivering a filter solution to the dialyzer.

The subtleties of the artificial filtration procedure

The appointment of an innovative method of blood purification involves the obligatory specific preparation of the patient. Sometimes the stage of the disease is so advanced that it limits the possibility of installing an apparatus for introducing, as well as extracting fluids from the circulatory system.

Preparatory measures before blood purification:

  • The specialist forms a fistula from several vessels. In humans, the usual location of the fistula is on the forearm. It contributes to the thickening of the walls of blood vessels in this area, this has a beneficial effect on the long and frequent use of the hemodialysis procedure.
  • Using local anesthesia, a catheter is sewn into the venous vessel - devices for easy extraction and injection of liquid formulations. Located in the groin area.
  • A prerequisite for patients who have undergone this training is the limitation of physical activity, even the simple lifting of heavy objects is prohibited.

Catheter sewn into a vein

Hemodialysis is preceded by standard evaluation analyzes of pulse rate and blood pressure, the patient is additionally weighed, this makes it possible to exclude the development of edema.

The procedure itself takes approximately 5 hours. Systematic filtering repetitions up to 3 times per week. An artificial kidney is installed by a whole professional team of medical workers, this avoids blood poisoning.

Filtration is carried out due to the different osmotic pressure of the membrane and the creation of a diffusion effect. These two factors cause the rapid removal of toxic compounds.

Blood through a system of tubes and a catheter enters the filter tank, where the cellophane membrane is located. Its purpose is to separate slag compounds from the structural elements of the blood. After passing through the dialyzer with all the tubes and cleaning glasses, membranes, the blood returns to the patient's body.

When undergoing the filtration procedure, the patient is allowed to do normal activities while in a horizontal position.

Limitations and Side Effects

Before prescribing a hemodialysis procedure, the attending specialist is obliged to conduct a complete examination of the nervous system, to identify the slightest complications and disorders of the cardiovascular system and other important organs. The presence of any abnormalities is a factor limiting the appointment.

Even an expensive artificial kidney is characterized by the following side symptoms:

  • the appearance of hypertension, the development of hypotension;
  • spontaneous vomiting, nausea;
  • involuntary muscle cramps;
  • systematic shortness of breath;
  • spread of itching;
  • limb anemia.

Preventive prescription of medications will help to neutralize the symptoms from the operation of the device. The procedure is accompanied by a mandatory adherence to a strict diet, but for greater effectiveness of the treatment, it is simply necessary.

In addition to the planned preliminary measures, before the installation of an artificial filtering organ, there are several pathological conditions and complications that limit this possibility:

  • cessation of blood supply for various reasons;
  • the appearance of bleeding;
  • severe injuries and earlier condition after them;
  • infectious diseases after abortion;
  • the use is limited with the development of an inflammatory process in the kidneys, this provokes the outflow of urine;
  • with the appearance of a blockade of any degree of the urinary canals.

Carrying out hemodialysis at home

A common stereotype of many conservative doctors and uninformed patients is the belief that the hemodialysis procedure is performed exclusively in a medical institution. Modern devices and the level of provision with the necessary elements for filtration make it possible to carry out it not in a clinic, but in a normal home environment.

The private environment involves the use of extremely expensive equipment, but this minimizes the percentage of blood infection with hepatitis B and C groups, and in hospitals this situation is common.

Carrying out hemodialysis in people suffering from severe forms of kidney failure at home is a common technique today. Since severe forms of the disease often significantly reduce immune protection, any contact in the hospital with potential carriers becomes a serious risk to life. Each performed filtration at the patient's home carries extremely positive feedback and increases the effectiveness of treatment.

An artificial kidney is an apparatus for removing toxic metabolic products from the patient's blood that accumulate in severe kidney damage (acute and chronic). The operation of the device is based on the principle - the removal of low molecular weight substances from colloidal solutions due to diffusion and the difference in osmotic pressure on both sides of a semi-permeable cellophane membrane. Ions of potassium, sodium, molecules of urea, creatinine, ammonia, etc. freely penetrate through the pores of cellophane. At the same time, larger protein molecules, blood cells and bacteria cannot overcome the cellophane barrier. There are two main types of artificial devices: devices with a cellophane tube with a diameter of 25-35 mm and devices with a lamellar cellophane membrane. Domestic artificial kidney refers to dialyzers with lamellar cellophane membrane. Its scheme is shown in the figure. Blood from the patient enters through the catheter using a pump into the dialyzer, which is mounted on a tank containing 110 liters of dialysis solution. Passing between the cellophane plates of the dialyzer, the patient's blood through the cellophane membrane comes into contact with the dialysis solution flowing towards. After the dialyzer, the blood enters the performance meter and then returns through the filter and air trap along the catheter to the patient's venous system. The flowing dialysis fluid is standard and contains all the main blood ions (K·, Na·, etc.), glucose in a concentration corresponding to the concentration of those in the blood of a healthy person. The solution is automatically heated to a temperature of 38°C and saturated with carbogen to pH=7.4. The clearance (purification factor) of the apparatus for urea is 140 ml/min.

A plate of organic glass is placed on the metal base of the dialyzer in a horizontal position. Two cellophane sheets are laid on it, which are covered with the next plate on top. Thus, 12 plates are laid, which are fastened with metal bolts. Cellophane membranes are perforated through special holes, as a result of which the inter-cellophane spaces are interconnected. The manometer checks the tightness of the apparatus assembly. Next, a dialyzer pump is assembled, to which a blood supply catheter is attached, and on the other side a tube attached to the dialyzer inlet. The dialyzer outlet is connected to the performance meter, to the upper end of which the blood return hose to the patient is attached. After that, the device is sterilized with diacid, washed with sterile saline and filled with blood or polyglucin. The device is connected to the patient either by arteriovenous or veno-venous method. In the first case, after exposure of the radial artery, blood is taken into the apparatus with a vascular catheter inserted into its lumen. The return flow of blood from the device goes through a catheter inserted into a superficial vein. In the second method, by exposing a large vein on the thigh, probing of the inferior vena cava is achieved, from the lumen of which blood is taken. The blood returns to the cubital vein. To quickly connect the device and conduct multiple dialysis, a shunt (vessel prosthesis) is placed between the catheterized radial artery and a nearby vein. After connecting the device, heparin is injected into the blood stream to reduce and prevent thrombosis. Hemodialysis is carried out within 4-12 hours, depending on the disease and the patient's condition.

An artificial kidney cannot completely replace kidney function, especially for a long time. However, for many months it is possible to maintain the viability of the organism at a sufficient level. An artificial kidney in some cases is a preliminary stage of a kidney operation.

artificial kidney. The operation of the artificial kidney apparatus is based on the principle of dialysis due to diffusion and the difference in osmotic pressures on both sides of a cellophane plate, which has the properties of a semipermeable membrane. Small molecules of Mg··, K·, Na·, Ca·, Cl·, HCO 3 ions and such simple organic compounds as urea, creatinine, phenol derivatives freely penetrate through the pores of cellophane. At the same time, protein molecules, blood cells on the one hand, and possible bacteria on the other cannot overcome the cellophane barrier.

Among the many models of artificial kidney devices, two main types can be distinguished: devices with a cellophane membrane shaped like a tube with a diameter of 25-35 mm, and devices with a lamellar cellophane membrane. The Kolff-Wochinger two-coil artificial kidney is most widely used abroad (Fig. 1). An important advantage of this artificial kidney model is that the spools with wound plastic hoses come from the factory in a sterile condition and can be used immediately if necessary. Ease of installation and handling, large dialysis surface (19,000 cm1) have made this model very popular. The disadvantages of the apparatus are a large capacity for blood and a significant resistance to blood flow due to the tight winding of the two dialysis hoses.

Fig.1. Scheme of the Kolff-Watchinger kidney connected to the patient: 1 - blood filter; 2 - blood pump; 3 - dialyzer; 4 - dialysis solution; a - artery, v - vein.

Therefore, a pump is installed at the inlet to the dialyzer.

The Soviet model of an artificial kidney, designed at the Scientific Research Institute of Surgical Equipment and Instruments (NIIKhAI), belongs to the type of dialyzers with a lamellar cellophane membrane.

Extensive clinical experience of Soviet and foreign clinicians shows the high efficiency of hemodialysis in the treatment of patients with renal insufficiency.

However, an artificial kidney does not replace other therapeutic measures. It is one of the most important parts of complex therapy. An artificial kidney cannot completely replace the multifaceted function of diseased kidneys, moreover, for a long time.

In the USSR, an artificial kidney began to be used since 1958 in the urological clinic of the 2nd MMI on the basis of the 1st City Hospital. Currently, more than 50 departments of clinical hospitals are equipped with an artificial kidney.

The connection of the device with the patient is usually carried out by two methods: arterial-venous or veno-venous. In the first case, after exposure of the artery (often radial), blood sampling into the apparatus is carried out with a vascular catheter inserted into its lumen. The reverse flow of blood from the apparatus to the patient occurs through a probe inserted into any superficial vein (usually the cubital). With the veno-venous method of connection by puncture or exposure of a large vein on the thigh, probing and blood sampling from the inferior vena cava is achieved. The reverse flow of blood occurs through any vein of the forearm.

Currently, the puncture method of vascular catheterization has become widespread. The femoral artery and vein are punctured under the pupart ligament and appropriate catheters are inserted into the vessels along the conductor, which are connected to the apparatus with the help of switching lines. If during the treatment of the patient multiple use of hemodialysis is supposed, then a permanent arteriovenous shunt according to Scribner (VN Scribner) is installed on the forearm. The essence of the method lies in probing the radial artery and a nearby vein on the forearm. These probes are connected by special devices, and blood flows from the artery directly into the vein. For hemodialysis, changing the connector allows you to connect the patient's circulatory system with the artificial kidney apparatus in a few minutes. After hemodialysis, the shunt is restored again using a semicircular connector.

Artificial hemophilia is carried out by periodic administration of heparin (2 mg/kg). After hemodialysis, the effect of heparin in the patient's blood is neutralized by the introduction of a solution of protamine sulfate. All parts of the apparatus that come into contact with the patient's blood must be siliconized and sterilized.

The scheme of the Soviet model of an artificial kidney is shown in fig. 2. The patient's blood flows through the catheter (1) using the pump (2) to the dialyzer (3). Passing between the cellophane plates of the latter (in each of its 11 sections), the patient's blood through the cellophane plate comes into contact with the dialysis solution flowing towards. Its composition is usually standard and contains all the main blood ions (K·, Na·, Ca··, Mg·, Cl·, HCO 3) and glucose in concentrations necessary to correct the electrolyte composition of the patient's blood. After the dialyzer, the blood enters the performance meter (4), where blood clots and air are trapped. The blood is then returned to the patient's veins through the catheter. The dialysis solution is brought to t° 38° using an automatic heater (8) and saturated with carbogen so that its pH is 7.4. The pump (9) pumps the dialysate into the dialyzer. The blood flow rate in the dialyzer is usually 250-300 ml/min. The clearance of the apparatus is 140 ml/min for urea.


Rice. 2. Scheme of the Soviet model of the apparatus "artificial kidney": 1 - catheter; 2 - blood pump; 3 - dialyzer; 4 - performance meter; 5 - air trap; 6 - filter; 7 - catheter for returning blood to the patient; 8 - heater; 9 - pump for dialysis fluid; 10 - tank for dialysis solution; 11 - rotameter for oxygen; 12 - carbon dioxide rotameter; 13 - hydraulic drive of the perfusion pump.

At present, a new model of an artificial kidney has been constructed (Fig. 3). The basic principle of its work remains the same. The apparatus has two independent sections with a dialysis surface area of ​​8000 cm 2 each, with two independent pumps; it is equipped with a special device for regional heparinization and is more convenient for the treatment of patients with chronic renal failure due to the possibility of reducing the dialysis surface area.


Rice. 3. General view of the new model of the Soviet apparatus "artificial kidney" designed by NIIKHAI.

The most effective and convenient for clinical use are those artificial kidney models that meet the following basic requirements: high intensity of blood dialysis, ease and safety of handling the apparatus, and a small amount of blood. These are the devices of NIIKHAI (USSR), Kolff-Watchinger (USA) and Dogliotti (Italy). They are especially good in the treatment of patients with acute renal failure. With the most convenient devices, the modernized Kolff model and the two-plate artificial kidney of the Carina system are considered to be the most convenient. Kaden (W. Kaden, GDR) proposed an original model of an artificial kidney device for the treatment of chronic renal failure. Its main advantage is portability and low cost.

The use of chronic hemodialysis in modern conditions is an important task. According to the data of the III International Congress of Nephrologists, in some countries (USA), up to 50,000 patients with chronic renal failure of various etiologies annually need chronic hemodialysis per 100 million people. Applying an artificial kidney to a patient with chronic renal failure twice a week, it is possible to maintain the level of azotemia, normal water and electrolyte balance and a satisfactory general condition of the patient at subnormal levels. Thus, the life of patients in the terminal stage of chronic renal failure can be extended for many months and even years. An artificial kidney is beginning to be used at home, though so far in rare cases. Multiple repeated hemodialysis in patients with chronic renal failure is associated with a number of significant difficulties and various complications. These primarily include thrombosis of arteriovenous shunts. The use of Teflon-silastic material made it possible to extend the service life of the shunt up to 6-9 months. Some patients often suffer from severe peripheral nephropathy. Calcium metabolism is disturbed, which is manifested by metastatic calcification and osteoporosis. Anemia requires constant blood transfusions. Frequent complications are intermittent infection and hypertension. Testicular atrophy (in men) and amenorrhea (in women) are quite common. Finally, during repeated hemodialysis, hypercalcemia, severe anemia, septicemia, and pyrogenic reactions may develop.

It is more expedient to use chronic hemodialysis in patients in truly terminal stages of chronic renal failure, given the possible homo- and heterotransplantation of the kidney during treatment.

In patients with acute renal failure, hemodialysis allows achieving a significant clinical effect in a few hours due to the release of the body from nitrogenous slags, normalization of water and electrolyte balance, elimination of acidosis. This sometimes may be a temporary effect allows the body to enhance the regenerative processes in the kidneys and liver, contributing to the restoration of their function. Therefore, in most etiological forms of acute renal failure, the use of an artificial kidney is indicated. These include conditions in which kidney function is often deeply impaired: collapse of the peripheral circulation due to severe operations, trauma, bleeding, post-abortion infection, incompatible blood transfusion, poisoning with nephrotoxic poisons, acute anuric glomerulonephritis, urinary tract occlusion. In chronic renal failure in the acute stage, repeated hemodialysis can significantly improve kidney function.

Important in determining indications for hemodialysis is taking into account the state of the nervous system, respiratory organs, cardiovascular system and the functional state of the liver.

The use of an artificial kidney in patients in a state of uremic coma should be considered as a late event, and, of course, the success of treatment is not always positive.

Among biochemical disorders, the leading indication for hemodialysis is
hyperazotemia, when the residual nitrogen in the blood serum is 150-200 mg% (urea content 350-400 mg%), creatinine content 12-15 mg%. An increase in the content of potassium in the blood serum up to 7 meq / l and above, a decrease in the alkaline reserve to 10 meq / l, in combination with other water and electrolyte disorders, are indications for urgent hemodialysis.

Among patients with acute renal failure, 35-45% of the disease is not too severe. Despite the presence of anuria, azotemia and other disorders, the treatment of these patients can be carried out without the use of hemodialysis.

Among the contraindications, one should take into account decompensation of the cardiovascular system, liver failure, an active septic process in the body in the phase of intermittent bacteremic shock. A fresh focus of bleeding is not considered an absolute contraindication to hemodialysis. The use of regional (only in the artificial kidney apparatus) heparinization with the help of special equipment makes it possible to avoid increased bleeding.

The use of an artificial kidney according to strict indications with the implementation of all precautions and careful monitoring of the patient during and after dialysis is practically safe and does not threaten with any complications.