Hemodialysis is one of the methods of renal replacement therapy in patients with end-stage chronic or acute renal failure, which removes the end products of metabolism – creatinine and urea, as well as free water. The method is based on the principle of diffusion and convection of substances with small and medium molecular weights through a semipermeable membrane, which makes it possible to remove toxic substances and metabolic products from the blood.
Hemodialysis is performed using an artificial kidney machine. The device consists of the following components: a device for blood supply, a device for preparing and supplying dialysis solution, a monitor, a dialyzer. The most important function is performed by a dialyzer. It contains a semipermeable membrane based on cellulose or artificial polymers. The membrane has an area of 0.2 to 2 m², a thickness of 8, 11, 15 or 30 microns, and a pore diameter of 0.5 to 5 nm. It divides the internal space of the dialyzer into two parts (for blood and solution), each of which has its own entrance and exit. Blood taken from the patient’s vessels enters the dialyzer and is located on one side of the membrane, on the other side there is a solution that is similar in electrolyte composition to the composition of blood. Substances with a small molecular weight are removed by diffusion of a lower concentration through the membrane (electrolytes, urea, creatinine, uric acid, etc.). Ultrafiltration removes excess water and substances with a large molecular weight (up to 30,000). Purified blood returns to the patient’s blood vessels.
The need for hemodialysis occurs with severe kidney diseases, or when a large amount of toxic substances enters the blood. The method is used when the glomerular filtration rate of the kidneys decreases to 15-10 mL/min, accompanied by an increase in the concentration of blood urea <30 mmol/L, creatinine – <700 mmol/L, as well as when patients have hyperkalemia, metabolic acidosis. This condition can be accompanied by symptoms such as nausea, vomiting, swelling, and fatigue. However, even if the patient does not yet have these symptoms, there may still be high levels of metabolic products in the blood that can be toxic.
Common causes of kidney failure include:
In addition, the kidneys may suddenly stop (acute kidney damage) after a serious illness, complex surgery, heart attack, or other serious problem. Some medications can also cause kidney damage.
Your doctor will help you determine when to start hemodialysis based on several factors, including:
In general, hemodialysis helps the body control blood pressure and maintain a proper balance of fluids and electrolytes, such as potassium and sodium. Usually, hemodialysis begins long before kidney function is disrupted so much that it causes life-threatening complications.
Most people who need hemodialysis have various health problems. Hemodialysis prolongs the life of many people, but the life expectancy of people on hemodialysis is still shorter than in the general population.
Although hemodialysis treatment may be effective in replacing some of the lost kidney function, patients may experience some of the comorbidities listed below, although not everyone faces all of these problems
There are three types of access:
During the procedures, the patient sits or lies on the couch while their blood flows through a dialyzer – a filter that acts as an artificial kidney to purify the blood. The patient can use this time to watch TV or a movie, read or sleep.
Preparation. The patient’s weight, blood pressure, pulse, and temperature are checked. The skin at the access point is cleaned.
Beginning. During hemodialysis, two needles are inserted into the arm through the access point and fixed with a patch. Each needle is attached to a flexible plastic tube that connects to the dialyzer. With a single tube, the dialyzer filters the blood, allowing metabolic products and fluids to pass from the blood to a cleansing fluid called dialysate. The filtered blood returns to the body through a second tube.
Symptoms. The patient may experience nausea and abdominal cramps when removing excess fluid, especially if HD is performed only three times a week, and not more often.
Monitoring. Since blood pressure and heart rate can fluctuate when excess fluid is removed, these indicators are constantly monitored during the procedure.
Completion. After hemodialysis is completed, the needles are removed from the access point and a tight bandage is applied to prevent bleeding. The patient’s weight is recorded again.
The duration of one hemodialysis session depends on the technique, and on average is 4-6 hours.