Hemodialysis is a method of extrarenal blood purification, irreplaceable under certain critical conditions, often becoming a regular procedure. Often, hemodialysis is associated with the treatment of kidney dysfunction, and their final recovery usually becomes possible only after transplantation.
What is hemodialysis?
The procedure of hemodialysis is based on the diffusion through the semipermeable membrane of toxic substances that accumulate in the blood and other biological fluids of a person in the presence of uremia. The procedure is an extrarenal blood purification and is used in the case of acute or chronic renal failure, it should not be confused with peritoneal or intestinal dialysis. Hemodialysis allows to normalize violations of water and electrolyte balance, to remove from the body toxic metabolic products, which is usually included in the function of the kidneys.
Intestinal dialysis has little to do with hemodialysis, because it is a washing of the intestinal mucosa with hypertonic solutions. In peritoneal dialysis with hemodialysis, the total is somewhat larger – this is also the purification of blood, but it is made by replacing special solutions in the abdominal cavity, here the membrane plays the role of the peritoneum
The process of dialysis is mediated by the mechanisms of diffusion of osmosis and ultrafiltration. Dialysis treatment may be inpatient or home-based.
For carrying out hemodialysis, the “artificial kidney” apparatus is used, the most effective of which allow to shorten the procedure time to 3-4 hours and they can be used for dialysis at home.
The basis of hemodialysis is the procedure for the exchange with the use of a semi-impermeable membrane, on the one hand contacting the blood, and on the other hand with the dialysis solution. Between the blood and the solution, a hydrostatic pressure gradient is created, and thus ultrafiltration is ensured-an excess of fluid is removed from the body, and harmful substances and metabolic products are removed from the blood.
- withdraw the so-called uremic poisons,
- reduce the level of urea and creatinine in the blood,
- in most cases, correct the violation of the acid-base state,
- to correct the dielectrolite,
- reduce arterial hypertension by removing sodium and water,
- mitigate the manifestations of uremic encephalopathy.
However, to reduce anemia, manifestations of polyneuropathy, osteopathy, pericarditis, intolerable itching, it is necessary to continue drug treatment, which was carried out before dialysis, and sometimes resort to hemofiltration or plasmapheresis.
The time of dialysis depends on the patient’s condition and ranges from 12 to 24 hours per week. Recently there has been a tendency to reduce the time of dialysis to 4 hours once in two days.
The mode and program of hemodialysis are determined strictly individually. The frequency of hemodialysis can be controlled by selecting membranes differing in surface area. This can be a daily two-hour dialysis, and maybe two-time a week. Even less often, hemodialysis is possible if the excretory function of the kidneys is preserved.
Hemodialysis can significantly improve the prognosis of chronic renal failure – 5-year survival of patients on ambulatory hemodialysis, in general, reaches 80%. Rehabilitation of these patients can be estimated as follows:
- excellent – working capacity is restored completely (rarely);
- good – the symptoms of uremia are eliminated, but working capacity, physical and mental activity are reduced (50% of patients);
- satisfactory – working capacity and activity reduced by more than half;
- bad – a person is completely inoperable.
Indications for hemodialysis
The quality of the patient’s blood requires the use of hemodialysis in the following pathologies:
- acute renal insufficiency;
- chronic renal failure;
- severe violations of electrolyte blood composition;
- hyperhydration, life threatening (pulmonary edema, edema of the brain, etc.), not reduced by conservative therapy;
- poisoning with poisons and drugs (able to pass through the hemodialysis membrane);
- poisoning with alcohols.
Treatment with program hemodialysis is indicated with such clinical indicators:
- reduction of glomerular filtration to 5 ml / min, which roughly corresponds to an increase in the level of creatinine to 1.1-1.3 mmol / l (if clinical manifestations are expressed, hemodialysis should be started as early as possible, even at a clearance of 10 ml / min);
- day diuresis less than 700 ml;
- appearance of initial signs of uremic osteopathy, polyneuropathy, non-corrected hyperkalemia (7 mmol / L and higher), hyperhydration, precomatosis, indomitable vomiting, intolerable itching, pericarditis, hemorrhagic diathesis.
Contraindications to hemodialysis
Absolute contraindications to treatment by program hemodialysis are:
- malignant neoplasms,
- acute and chronic leukemia,
- severe organic damage to the nervous system,
- severe mental disorders (psychosis, epilepsy, schizophrenia),
- severe cardiac and pulmonary insufficiency,
- terminal stage of chronic renal failure with irreversible severe changes in organs and systems;
- age older than 80 years or over 70 in the presence of diabetes.
Relative contraindications are:
- severe forms of diabetes,
- severe forms of amyloidosis,
- active form of pulmonary tuberculosis,
- active phase of systemic lupus erythematosus,
- systemic scleroderma,
- peptic ulcer,
- nonspecific ulcerative colitis.
With peptic ulcer and ulcerative colitis before the beginning of program hemodialysis, radical treatment of the patient, including the surgical one, is necessary.
The elderly age of patients is not a contraindication to hemodialysis, but at the age of 65 years its effectiveness is significantly reduced and in the next two years the survival rate is estimated at 50% of patients, while in young and middle age the life expectancy of patients on hemodialysis reaches 5-10 years and more.
How is hemodialysis performed?
Hemodialysis is a complex medical procedure, mostly carried out in a medical institution, but today there are also devices for home hemodialysis.
Hemodialysis will be impossible without three of its mandatory components – a device for the supply of blood, a dialyzer directly, that is, a semipermeable membrane, and a device for feeding and preparing a dialysate solution.
The classical procedure of hemodialysis requires the following:
- reverse osmosis for water purification;
- roller pump station;
- hemodialysis (the so-called “artificial kidney”), temporarily replacing the kidney function;
- an armchair / bed for placing patients in them during the procedure
- medical scales
- dialyzer – functional unit of hemodialysis, containing in its structure a semipermeable membrane;
- a blood line / blood loop for carrying the patient’s blood from the bloodstream to the dialyzer and from the dialyzer to the bloodstream.
- 2-lumen permanent and temporary central venous catheters or needles for puncture arteriovenous fistula / arteriovenous vascular prosthesis.
- acetate and bicarbonate concentrate in a suitable container for sampling;
- A sterile kit that includes napkins, tampons, ancillary tools;
- saline (for example, 0.9% sodium chloride) – 1500-2000 ml;
- aseptic and antiseptics;
- disposable syringes;
- heparin or low molecular weight heparins;
- preparations and means of emergency care.
The presence of a roller pump blood is withdrawn through the tubes in the dialyzer. On her way, the rate of blood flow and pressure is measured, the current in 300-450 ml of blood per minute is considered normal. At the same time, the dialysis solution is being prepared, it enters the dialyzer, passing the membrane at a rate of 500 ml per minute in the direction opposite to the blood flow.
The composition of the dialysis solution is usually similar to the blood plasma. Sometimes (depending on the level of electrolytes in the blood and to regulate the amount of blood removed), the composition is adjusted in the amount of potassium or sodium, and the amount of chlorine, calcium and bicarbonate usually remains unchanged.
Usually the procedure is performed on an outpatient basis, but portable devices are developed (and popular abroad) that allow you to make hemodialysis at home. Advantages of home hemodialysis are the possibility of more frequent it and the absence of the need for constant visits to the medical center, which makes it compatible with those closest to normal work, diet and lifestyle.
Adjacent to hemodialysis procedures
Hemodialysis is used to treat critical conditions, often renal failure – acute or chronic, and therefore does not exclude the combination of this procedure with others to achieve maximum effect.
Hemofiltration is based on the convector transport of the liquid part of the blood and dissolved substances in it through a membrane with a high hydraulic permeability with a partial or complete treatment of the ultrafiltrate with a sterile solution.
Hemofiltration is a method of purifying blood by filtration through dense membranes with high porosity, capable of withstanding a higher hydrostatic pressure than with conventional dialysis (200-300 mm Hg). The filtration rate of blood reaches 50-90 ml / min, due to which the body removes a large amount of fluid and toxic substances. Hemofiltration is able to correct a number of pathological conditions resistant to hemodialysis: persistent hyperhydration and arterial hypertension, as well as uremic neuropathy, hypertriglyceridemia, hyperphosphatemia, pericarditis. It is used mainly in patients with renal failure with volume overload, which does not need hemodialysis.
Hemodiafiltration combines the effects of hemofiltration and hemodialysis.
The use of peritoneal dialysis is based on the fact that the blood vessels inside the peritoneum are separated from its cavity only by a thin layer of mesothelium, the total area of which is 1-2 mg. An abdominal cavity 3-4 cm below the umbilicus is inserted with a plastic catheter of different design, the proximal part of which is displaced into the subcutaneous tunnel (10 cm long), directed upward to prevent infection of the peritoneum. After this, the end of the catheter is withdrawn through an additional opening in the skin.
In recent years, a widespread outpatient peritoneal dialysis has become widespread: in the abdominal cavity several times a day is changing
2 liters of dialysate, which is injected from a special bag. The composition of it is selected individually for each patient, depending on the nature of the disorders of homeostasis and the level of azotemia.
The use of peritoneal dialysis is limited because of the likelihood of complications:
- infection of the catheterization site and peritonitis;
- large protein losses – up to 20-25 g per day, which requires increasing its content in the diet to 1-1.4 g per 1 kg of body weight per day;
- basal atelectasis of the lung with the administration of excessively large volumes of dialysate.
Peritoneal dialysis is indicated in the terminal stage of chronic renal failure:
- patients with diabetes mellitus,
- sick with viral hepatitis,
- AIDS patients,
- elderly people suffering from heart failure,
- patients who are difficult to apply arteriovenous fistula (in particular, children),
- patients with severe anemia,
- patients with malignant hypertension.
Contraindications for peritoneal dialysis are:
- the recently transferred abdominal operation,
- a large number of surgical interventions in history,
- the presence of adhesions, co-or ileostomy, hernia,
- infection of the skin and subcutaneous tissue in the anterior abdominal wall,
- malignant neoplasms in the abdominal cavity,
- obesity III-IV degree,
- diseases of the spine, accompanied by pain in the lower back,
- severe lung diseases with bronchoobstructive syndrome,
- negative attitude of patients to this method of treatment.
Such limitations are deprived of kidney transplantation, which by its effectiveness is much superior to dialysis, since it opens the possibility for restoring all the functions of healthy kidneys and normalizing the inherent metabolic disorders of uremia.
Nutrition in hemodialysis plays far from a secondary role. The formulation of a diet should aim to minimize the accumulation of life-giving products in the blood, and therefore the following nuances are taken into account:
- the basis of the daily menu is a balanced amount of protein products, that is, chicken, meat and fish;
- careful monitoring must be made to the amount of potassium-containing products and not to abuse them (the risk of complications from the heart is increased) – they are salt substitutes, some fruits (bananas, oranges), vegetables (potatoes), chocolate, dried fruits and nuts;
- careful monitoring must be subjected to the amount of fluid consumed (increased risk of edema, hypertension, complications from the heart and lungs) – focus on increasing body weight of not more than 5% between procedures;
- limit the amount of table salt that causes thirst and delays fluid in the body;
- limit the intake of phosphorus-rich foods if the doctor has prescribed medications to normalize the exchange of calcium and phosphorus, which is often the case – liver, heart, sea fish, egg yolks, nuts and seeds, bran;
It is strongly recommended that those on hemodialysis do not conceal from their attending physician cases of diet disorders. From those, no one is immune, but awareness of this doctor will allow the hemodialysis program to be adjusted as much as possible for the patient.
Complications of hemodialysis
Hemodialysis is a procedure for which patients are forced to resort for many years. It is not devoid of a certain proportion of complications, they include:
- syndrome of imbalance – manifested headache, nausea, muscle cramps, increased blood pressure and, eventually, fainting;
- arterial hypotension – more often due to excessive ultrafiltration during dialysis;
- pyrogenic reactions – for example, an increase in body temperature during a hemodialysis session is due to bacterial contamination of the equipment and endotoxemia;
- air embolism – is a consequence of airflow into the system from different parts of the apparatus, as a result of which the clinical picture of the embolism of cerebral or pulmonary vessels develops
- bleeding – nasal and gastrointestinal hemorrhages occur more often, less often cerebral hemorrhage, pericardial cavity and subdural hematomas;
- perforation of the dialyzer membrane,
- secondary infection is associated with infection of the hepatitis B virus with both patients (7-20%) and clinic staff, with jaundice forms of 30% and HBs antigen only in 40-50% of all cases; In addition to viral hepatitis, pneumonia often develops;
- aluminum intoxication – most often a consequence of its increased concentration in water, which is used to make dialysate; increasing its concentration in the blood after 1-2 years from the beginning of the treatment with dialysis, and sometimes even earlier, leads to the so-called aluminum disease, manifested by osteopathy (joint pain, muscle weakness, bone fracture risk) and encephalopathy (speech disorders, dementia, moderate hydrocephalus).
- acquired kidney cysts – are especially often found in patients undergoing program hemodialysis for more than 2 years, are localized in most cases in a cortex, are often calcified, and in 3% of patients are combined with malignant kidney tumors.