Hemodialysis Lecture (2)

Renal failure When the kidneys do not work well enough and fail to adequately filter toxins and waste products from the blood to maintain life, Dialysis or a kidney transplant will be needed.

- Ischemia (reduction in blood flow) ), Types of renal failure: Acute renal failure , is associated with: - Ischemia (reduction in blood flow) ), - Acute glomerulonephritis, and - Tubular necrosis or poisoning with nephrotoxins. Chronic renal failure is usually caused by: - Chronic glomerulonephritis, - Infection of the urinary tract, - Hypertension or vascular disease. 3

Artificial kidney An artificial kidney is a medical device which performs the function of a missing or damaged kidney, filtering the blood to remove waste products and returning purified blood to the body. The most well known and frequently used form of the artificial kidney is the Hemodialysis machine 4

Hemodialysis Peritoneal dialysis Types of dialysis Hemodialysis Blood is passed through an artificial kidney (hemodialyzer) to clean it. Peritoneal dialysis Uses a filtering process similar to hemodialysis, but the blood is cleaned inside the body rather than in a machine. 5

Hemodialysis Dialysis of the blood, based on extra-corporeal exchanges between blood and a dialysis solution through a semi-permeable membrane in a dialyzer (artificial kidney).

This circuit includes a hemodialyzer, where the blood is cleaned. In hemodialysis, blood is removed from the body and circulated through an extracorporeal fluid circuit (outside the body), then returned to the patient. This circuit includes a hemodialyzer, where the blood is cleaned. The hemodialyzer contains a selectively semi-permeable membrane, which is a filter that allows fluids and wastes to pass through, but prevents the exchange of blood components. 7

The fluid used to clean the blood (dialysate) flows in the opposite direction to the blood on the opposite side of the membrane, while wastes and extra fluids are removed from the blood and end up in the dialysate. 8

Scientific principles of hemodialysis 9

Dialysate Solution A solution is a mixture of a solvent and a solute. The solvent is a fluid. The solute is any substance that can be dissolved into the solvent. Dialysate is the solution that is used during dialysis. Water is the solvent. The solutes are electrolytes (e.g., potassium, calcium, sodium, magnesium, and chloride ions) and glucose (Sugar). Electrolyte levels in dialysate closely match the levels in human blood.

Semi-permeable membrane A semi-permeable membrane is a type of thin, flexible filter a barrier that allows only particles smaller than a certain size to pass through it.

In dialysis, the semipermeable membrane’s holes allow small molecules, such as water and urea, to pass through easily. Middle molecules can also pass through, but more slowly. The small size of the pores keeps larger molecules and blood cells from passing through the membrane.

Dialyzer The dialyzer lets the patient’s blood interact with dialysate through a semi-permeable membrane. It has a blood and a dialysate compartment. The semi-permeable membrane keeps the two compartments apart.

The membrane is housed in a plastic case, which holds the dialyzer together and forms pathways for blood and dialysate to flow in and out. The semipermeable membrane acts like the vessel wall of a human nephron, because it is selective.