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Haemodialysis: Method of removing waste products such as creatinine and urea as well as free water from the blood when kidneys are in renal failure. The main principle involved is the diffusion of a solute against a semipermeable membrane.

How does hemodialysis work?

• A dialysis machine pumps small blood out of the body, mixed with an anticoagulant, and circulated through a filter called a dialyzer.

• Inside the dialyzer, a porous artificial membrane separated blood from the dialysis fluid.

• Diffusion of extra fluid and waste from the blood into the dialysate.

• Purified blood is pumped back into the body.

• The membrane is permeable to water and small ions but impermeable to the cells, lipids, or plasma proteins.

• Pressure in dialysate compartment lower than blood compartment.

• How is blood removed and replaced?

• An intravenous catheter

• An arteriovenous fistula

• A synthetic graft.

Types of Haemodialysis access:

• For temporary access: a shunt is created in the arm with one tube inserted in an artery and another in the vein.

• Tubes are joined above the skin.

• For permanent access: an anterio venous fistula is created by a surgical procedure.

Types of hemodialysis:

• Conventional hemodialysis

• daily haemodialysis

• nocturnal hemodialysis

1. Conventional hemodialysis

• Done 3 times per week, for about 3-4 hours. For each treatment, during which patients blood is drawn out through a tube at a rate of 300-400cc/min.

• During treatment, the patient's entire blood volume circulated through the machine every 15 minutes.

2. Daily hemodialysis

• Used by patients who do their dialysis at home.

• Usually done for 2 hours, six days a week.

3. Nocturnal hemodialysis

• Performed six nights a week and sixteen hours per session while the patient sleeps.

Peritoneal hemodialysis

• Introducing dialyzing fluid into the peritoneal cavity via the catheter and after a period fluid is drained and discarded.

• Principle: osmosis and diffusion.

• This process uses the patient's peritoneum in the abdomen as a membrane across which fluids and dissolved substances ( electrolytes, urea, albumin) are exchanged from blood.

Techniques used:

1. Manual intermittent peridialysis

2. Automated cycler intermittent peridialysis

3. continuous ambulatory peridialysis

1. manual intermittent peridialysis

• Bags containing fluid are warmed to the body.

• Fluid infused for 10 min allowed to remain for 60-90 minutes and drained in 10 to 20 minutes.

2. Automated cycler intermittent peridialysis

• People set the cycler at bedtime so dialysis takes place while sleeping performed 6 to 7 nights a week.

3. Continous ambulatory peridialysis

• During the day by keeping 2 liters of fluid in the abdomen at all times.

• exchanging fluid 4 to 6 times per day.