Hemodialysis - Causes, symptoms and treatment. MF.

Hemodialysis is a method of purifying blood through the selective removal of toxins through an artificial semipermeable membrane. It is used in patients with acute and chronic renal failure.

The "father" of hemodialysis is the Scottish chemist Graham, who in 1856 described the diffusion process, which he called "dialysis."Under the diffusion process, he understood the movement of water-soluble substances with a small molecular mass through a semipermeable membrane from a more concentrated solution( urine) to less concentrated( distilled water).For the first time in a person, a haemodialysis session was conducted by Georg Haas in 1911 in Strasbourg. As filters for blood purification, colloidal membranes were used in the form of thin tubes. As a means of diluting the blood, first used was giruidine( a drug obtained from the secretion of the salivary glands of a medical leech), and then heparin( extract from the liver of cattle).The Haas dialysis machine was impressive in size. It consisted of eight cylindrical containers filled with dialyzing fluid, inside of which were tubes through which blood flowed.

Haas hemodialysis machine.

In the period from 1926 to 1928 he conducted about 20 sessions of hemodialysis for patients with acute renal failure. Each hemodialysis session lasted about 60 minutes. Unfortunately, all patients died in a short time from intoxication and contamination of blood.

In 1943 W. Kolff first applied cellophane membranes as filters. Fifteen patients with acute kidney damage after the hemodialysis sessions passed away. And only the sixteenth patient after two sessions of dialysis survived, renal failure was cured. This method of treatment was sharply criticized by members of the scientific community. And only the invention of J. Merril flame photometry - a method for assessing the chemical composition of blood, has significantly reduced the mortality of patients from violations of water and electrolyte balance.

At present, the widespread use of hemodialysis in medicine has saved millions of patients with acute and chronic renal failure.

Indication of hemodialysis procedure

Conducting a hemodialysis session is indicated under the following conditions.

• signs of uremic( due to accumulation of harmful substances in the blood that are not excreted in case of kidney disease) intoxication: nausea, repeated vomiting, weakness, slight increase in temperature, unstable pressure.

• excess fluid that manifests itself in the form of treatment-resistant edema, as well as an increase or decrease in blood concentrations of potassium, sodium, chlorine.

• marked renal dysfunction: the glomerular filtration rate is below 10 ml / min( in children and in patients with diabetes less than 15 ml / min).

• Decompensated acidosis - a condition associated with an increase in the acidity of the blood( pH) of less than 7.35.

• Life-threatening edema of the brain and lungs, associated with intoxication of the body.

Contraindications of hemodialysis

For chronic hemodialysis, the following contraindications are distinguished:

• a marked decrease in blood pressure associated with significant blood loss or the release of a large amount of urine, for example, in the initial period with nephrotic syndrome.

• bleeding disorder with a high likelihood of profuse bleeding

• cardiovascular disease in the decompensation stage, in which the conduct of a hemodialysis session can dramatically complicate the patient's condition.

• an active inflammatory process, for example, tuberculosis of internal organs, sepsis.

• Oncological diseases with metastasis

• Mental illness of the patient.

In an emergency situation for conducting a session of acute hemodialysis, there are no contraindications.

Procedure for hemodialysis

Acute hemodialysis session is indicated for patients with acute renal failure who are in critical condition. As a rule, it is conducted in the intensive care unit. The number and multiplicity of procedures is determined by the severity of the patient's condition. As a rule, these are daily long sessions. Under favorable conditions it is possible to restore the function of the kidneys with a defect or completely, or, in severe cases, the development of chronic renal failure.

Chronic hemodialysis is performed in patients with terminal stage of chronic renal failure. To conduct it there is no need for hospitalization. Patients travel from home to outpatient centers or dialysis units at the hospital. After the procedure, they return home, that is, their quality of life is practically not reduced.

To conduct a hemodialysis session, the patient must be connected to the "artificial kidney" device. Previously, the patient formed a permanent or temporary vascular access. Temporary vascular accesses, such as catheterization of large veins( subclavian, jugular, femoral veins) in modern conditions are applicable only for carrying out emergency procedures.

Central catheter in subclavian vein.

It is forbidden to use them for a long time because of their possible suppuration at a long standing and the development of catheter-associated sepsis.

Currently, the gold standard of adequate vascular access is the formation of arteriovenous fistula. As a rule, during the operation, the radial artery stitches( forearm fistula) or the brachial artery( fistula of the shoulder) are sewn with the saphenous vein. As a result, the vein discharges blood from the artery under high pressure. The wall of the vein thickens, its lumen becomes wider, the vein does not subside at a high blood sampling rate.

Arteriovenous fistula.

This process is called arterial vein. Thanks to this, it becomes possible to puncture the vein with thick needles for hemodialysis.

Constant vascular access includes setting a permanent( permanent) catheter and bypass. Permanent catheters are specially treated to prevent the development of infection, and when used correctly, they serve for several years. When bypass, the artery and vein are connected by a synthetic prosthesis. Constant catheters and arteriovenous shunts are preferred in the case of the impossibility of forming a natural arteriovenous fistula, for example, in a loose type of vessel structure or a very thin arterial artery.

The device "artificial kidney" is a product in the form of a small unit, saturated with electrical and hydraulic systems, which guarantee a safe and efficient process of purifying the blood of toxins.

Modern device "artificial kidney".

Modern mobile phones are characterized by easy operation and maintenance. Each device "artificial kidney" consists of several blocks. The circulatory unit includes pumps that provide blood flow to the dialyzer. The standard hemodialysis session is performed at a blood flow velocity of 250-350 ml / min. In the dialysate block, mixing of ultrapure water and salt concentrate in a certain proportion to prepare a ready dialysis solution is provided. The correct composition of the dialysis solution plays an essential role in ensuring patient safety during dialysis. The extracorporeal block includes a dialyzer and blood lines. The dialyzer is the filter in which the process of purifying the blood from toxins and saturation with its beneficial substances takes place.

Appearance of capillary dialyzer.

The main characteristics of the dialyzer are the area of ​​the active surface, on the value of which the cleaning ability depends directly, and the dialyzer sterilization method. Currently, dialyzers sterilized with gamma irradiation or hot steam are preferred. According to current recommendations, re-use of dialyzers is not recommended. The most safe and effective at the present time are capillary dialyzers with synthetic membranes made of polysulfone, helixon, polyamix etc.

The blood purification control and monitoring system consists of a number of sensors whose main task is to provide an efficient process of blood purification and patient safety.

Currently, it is recommended to conduct chronic hemodialysis sessions 3 times a week for at least 4 hours. Dialysis time, blood flow velocity and dialyzer type are calculated on the basis of body weight, age, presence of residual kidney function in the patient.

With the ambulance crew, special transport or on their own, the patient comes to the place of hemodialysis. In the locker room he leaves his outer clothes, he changes into clean changeable clothes and shoes, climbs into the dialysis hall. Before each procedure, the medical staff weighs the patient( for estimating the increase of fluid in the interdialysis period), measures blood pressure, heart rate, estimates some other physical characteristics. If the patient is in a stable state, the doctor decides to start a hemodialysis session.

Conducting a hemodialysis session in the dialysis room.

For connection to the "artificial kidney" apparatus, the vein is punctured in the area of ​​the fistula, prosthesis, or in the presence of a catheter, the connection of the blood lines to the ports of the catheter. When filling the blood lines to prevent the formation of blood clots, heparin is injected. During the hemodialysis session, the medical staff assess the patient's condition( blood pressure, heart rate, body temperature) and, if necessary, adjust the treatment program.

After the session, the patient is weighed( to estimate the volume of fluid intake and determine the "dry" weight, that is, the weight without excess fluid), receives the doctor's recommendations for the interdialysis period, and goes home.

Once a month, the patient takes blood for analysis, which allows you to assess the degree of blood purification and, if necessary, adjust the hemodialysis program. Also, the blood test determines the concentration of hemoglobin, erythrocytes, hematocrit, the exchange of iron in the body to determine the further tactics of treatment of anemia, as well as the level of calcium, phosphorus, parathyroid hormone and metabolites of vitamin D to correct violations of phosphorus-calcium metabolism. Every 6 months, hepatitis B, C, HIV and pale treponema are detected in the blood of patients. All patients who receive hemodialysis treatment must be vaccinated against the hepatitis B and C. If necessary, other laboratory and instrumental analyzes, as well as specialist consultations, are possible.

Possible complications of hemodialysis

Despite the apparent simplicity, each hemodialysis session is a serious procedure that can easily lead to serious complications.

• A drop in blood pressure is one of the most common complications of a hemodialysis session. Predisposing factors are elderly age and concomitant diseases of the cardiovascular system. Typically, the reduction in blood pressure is associated with a large volume or rate of fluid intake during dialysis. Treatment is carried out by reducing the parameters of intake and recovery of fluid deficiency.

• Increased blood pressure is also a serious complication, which, without treatment, can lead to a heart attack or stroke. In the treatment of hypertension, adequate intake of fluid and the use of hypertensive drugs become a priority.

• Muscle cramps are usually associated with excessive fluid intake. Treatment consists in stopping the selection of fluid and the introduction of solutions that are hypertensive with respect to blood plasma.

• Nausea and vomiting are associated with a drop in blood pressure, as well as impaired function of the gastrointestinal tract. Treatment should be aimed at increasing blood pressure, the introduction of antiemetics, treatment of concomitant diseases of the gastrointestinal tract.

• Often, the headache associated with dialysis is associated with high or low pressure. Treatment consists in correction of arterial pressure and administration of anesthetics.

• Increased temperature is usually associated with an infection or a biocompatibility reaction. When suspected of an infectious disease, antibacterial drugs are indicated.

• The biocompatibility reaction is the response of the human body to blood contact with the components of the "artificial kidney" apparatus. It appears as an allergic reaction by the type of anaphylactic shock, or pyrogenic reaction, which is accompanied by an increase in temperature, a decrease in the number of blood leukocytes, pain in the back. Anaphylactic shock is characterized by a marked drop in pressure, difficulty breathing and requires immediate cessation of dialysis and emergency care. When pyrogenic reaction is shown, continuation of dialysis with the use of symptomatic treatment. Subsequently, it was recommended to identify the material on which the patient reacts and replace it with a safer analog.

• Patients with severe complications such as disketlavirium syndrome, arrhythmias, edema of the brain and lungs, should be in the intensive care unit under the supervision of specialists.

The life expectancy of patients during hemodialysis sessions is on the average 10-15 years with the observance of water and drinking regimen adequate for vascular access and proper treatment tactics.

Physician therapist, nephrologist Sirotkina EV