Hemodialysis (HD) is one of the modalities of renal replacement therapy for patients with acute and chronic renal failure. The blood is drained to the outside of the body through a dialyzer consisting of countless hollow fibers, where the blood and electrolyte solution (dialysate) with similar concentration in the body are exchanged inside and outside of one hollow fiber through the principles of dispersion, ultrafiltration, adsorption, and convection, to remove metabolic wastes from the body, to maintain the electrolyte and acid-base balance; and at the same time to remove the excessive water from the body and return purified blood back to the body. At the same time, it removes excessive water from the body and returns the purified blood back to the blood transfusion process called hemodialysis.
Basic introduction Chinese name: hemodialysis Foreign name: HD Indications: hypercalcemia, hypocalcemia and hyperphosphatemia Contraindications: intracranial hemorrhage or increased intracranial pressure, etc. Equipment: hemodialysis machine, water treatment system, dialysis fluid Principle, Indications, Contraindications, hemodialysis equipment, Principle 1.Solute transport(1) Diffusion: is the main mechanism for removing solutes in HD. The solutes are transported from the side of high concentration to the side of low concentration by the concentration gradient, this phenomenon is called diffusion. The energy for the diffusive transport of solutes comes from the irregular motion of the solute's molecules or particles themselves (Brownian motion).
(2) convection: the movement of solute through a semipermeable membrane along with the solvent is called convection. Unaffected by the molecular weight of the solute and its concentration gradient difference, the driving force across the membrane is the hydrostatic pressure difference between the two sides of the membrane, known as the solute traction.
(3) Adsorption: It is the selective adsorption of certain proteins, poisons and drugs (such as β2-microglobulin, complement, inflammatory mediators, endotoxin, etc.) by the interaction of positive and negative charges or van der Waals forces and hydrophilic groups on the surface of the dialysis membrane. All dialysis membrane surfaces are negatively charged, and the amount of negative charge on the membrane surface determines the amount of adsorbed heterogeneously charged proteins. During hemodialysis, certain abnormally elevated proteins, toxins and drugs in the blood are selectively adsorbed on the surface of the dialysis membrane, so that these disease-causing substances are removed, thus achieving the purpose of treatment.
2. Water transport
(1) Definition of ultrafiltration: The movement of a liquid through a semipermeable membrane under the effect of a hydrostatic pressure gradient or an osmotic pressure gradient is called ultrafiltration. In dialysis, ultrafiltration is the movement of water from the blood side to the dialysate side; conversely, if water moves from the dialysate side to the blood side, it is called anti-ultrafiltration.
(2) Factors affecting ultrafiltration: (1) purging pressure gradient; (2) osmotic pressure gradient; (3) transmembrane pressure; (4) ultrafiltration coefficient. Indications 1. Acute kidney injury.
2. Acute heart failure due to volume overload or hypertension that is difficult to control with drugs.
3. Severe metabolic acidosis and hyperkalemia that cannot be easily corrected.
4. Hypercalcemia, hypocalcemia and hyperphosphatemia.
5. Chronic renal failure combined with difficult to correct anemia.
6. Uremic neuropathy and encephalopathy.
7. Uremic pleurisy or pericarditis.
8. Chronic renal failure combined with severe malnutrition.
9. Unexplained organ dysfunction or decreased general condition.
10. Drug or poison poisoning. Contraindications 1. Intracranial hemorrhage or elevated intracranial pressure.
2. Severe shock that is difficult to correct with drugs.
3. Severe cardiomyopathy with refractory heart failure.
4. With mental disorder can not cooperate with hemodialysis treatment. Hemodialysis equipment Hemodialysis equipment includes hemodialysis machine, water treatment and dialyzer, **** with the composition of hemodialysis system.
1. Hemodialysis machine
is the most widely used therapeutic instrument in blood purification treatment, is a more complex electromechanical integration equipment, by the dialysis fluid supply monitoring device and extracorporeal circulation monitoring device.
2. Water treatment system
Because the patient's blood has to be exposed to a large amount of dialysate (120L) through the dialysis membrane in one dialysis, and the tap water in the city contains all kinds of trace elements, especially heavy metal elements, and also some disinfectants, endotoxins and bacteria, which will lead to the entry of these substances into the body when in contact with the blood. Therefore, tap water needs to be filtered, iron removal, softening, activated carbon, reverse osmosis treatment, only reverse osmosis water can be used as a concentrated dialysis solution dilution water, and a series of treatment devices for tap water that is the water treatment system.
3. Dialyzer
Also known as the "artificial kidney", by a chemical material made of hollow fibers, and each hollow fiber is distributed with countless small holes. During dialysis, the blood flows through the hollow fiber and the dialysis solution flows through the hollow fiber in the opposite direction, some small molecules of solutes and water in the blood dialysis solution are exchanged through the small holes on the hollow fiber, and the final result of the exchange is the uremic toxins in the blood and some electrolytes, the excess water into the dialysis solution is cleared, and some bicarbonate in the dialysis solution and the electrolytes enter into the blood. Thus, the purpose of removing toxins, water, maintaining acid-base balance and stability of the internal environment is achieved. The total area of the entire hollow fiber, i.e., the exchange area, determines the passing ability of small molecules, while the size of the membrane pore size determines the passing ability of medium and large molecules.
4. Dialysis fluid
Dialysis fluid is obtained by diluting the dialysis concentrate containing electrolytes and bases with reverse osmosis water in proportion, eventually forming a solution close to the electrolyte concentration of the blood in order to maintain the normal electrolyte level, and at the same time providing bases to the body through a higher concentration of bases to correct the acidosis present in the patient. Commonly used dialysis solution bases are mainly bicarbonate and also contain a small amount of acetic acid.