Dialysis And Artificial kidney

Dialysis And Artificial kidney Dialysis

Dialysis is the procedure to remove waste materials and toxic substances and to restore normal volume and composition of body fluid in severe renal failure. It is also called hemodialysis.

Artificial Kidney

An artificial kidney is a machine that is used to carry out dialysis during renal failure.

Conditions When Artificial Kidney Is Required

Artificial kidney is used to treat patients suffering from:

1. Acute renal failure that occurs due to circulatory shock or mercury poisoning
2. Chronic or permanent renal failure.

Read And Learn More: Medical Physiology Notes

Mechanism Of Function Of Artificial Kidney

• The term dialysis refers to the diffusion of solutes from an area of higher concentration to an area of lower concentration through a semipermeable membrane. This forms the principle of the artificial kidney.
• The patient’s arterial blood is passed continuously or intermittently through the artificial kidney and then back to the body through the vein. Heparin is used as an anticoagulant while passing the blood through the machine.
• Inside the artificial kidney, the blood passes through a dialyzer called hemofilter, which contains minute channels interposed between two cellophane membranes.
• The cellophane membranes are porous in nature The outer surface of these membranes is bathed in the dialyzing fluid called dialysate. The used dialysate in the arched-T kidney is constantly replaced by fresh dialysate.
• Urea, creatinine, phosphate, and other unwanted substances from the blood pass into the dialysate by a concentration gradient.

The essential substances required by the body diffuse from the dialysate into the blood.

• Almost all the substances except plasma proteins are exchanged between the blood and dialysate through the cellophane membranes.
• In addition to the dialyzer, the dialysis machine has several blood pumps with pressure monitors which enable easy flow of blood from the patient to the machine and back to the patient.
• It also has pumps for the flow of fresh dialysate and for the drainage of used dialysate.
• The total amount of blood in the dialysis machine at a time is about 500 mL. The rate of blood flow through the dialysis machine is about 200-300 mL/minute. The rate of dialysate flow is about 500 mL/minute.

Frequency And Duration Of Dialysis

The frequency and duration of dialysis depends upon the severity of renal dysfunction. Dialysis is done usually thrice a week in severe uremia. Each time the artificial kidney is used for about 6 hours.

Dialysate

• The concentration of various substances in the dialysis is adjusted in accordance with the needs of the patient’s body.
• The fluid does not contain urea, urate, sulfate, phosphate, or creatinine, so that, these substances move from the blood to the dialysate.
• The fluid has a low concentration of sodium, potassium, and chloride ions than in the uremic blood.
• But the concentration of glucose, bicarbonate, and calcium ions is more in the dialysate than in uremic blood.

Peritoneal Dialysis

• Peritoneal dialysis is the technique in which the peritoneal membrane is used as a semipermeable membrane. It is also used to treat patients suffering from renal failure.
• A tube is inserted into the peritoneal cavity through the anterior abdominal wall.
• The dialyzing fluid is passed through this tube under gravity. Urea, creatinine, phosphate, and other unwanted substances diffuse into the dialyzing fluid.
• The dialyzing fluid is replaced regularly for the continuous exchange of materials. Peritoneal dialysis is a simple, convenient, and less expensive technique compared to hemodialysis.
• The patients themselves can change the fluid on an outpatient basis. However, it has a few drawbacks. It is less efficient in removing some of the toxic substances and it may lead to complications by infections.

Uremia

• Uremia is a condition that is characterized by the excess accumulation of products of protein metabolism.
• The blood level of urea, nitrogen, and creatinine increases. There is also an accumulation of other toxic substances like organic acids and phenols, which produce the symptoms of uremia.
• The artificial kidney can excrete more than double the or o; oi of urea that could be excreted by both the Normal kidneys.
• About 200-250 mL of plasma could be observed off urea per minute by the artificial kidney.
• But, the urea clearance by a normal kidney is only about 70 rnL/minute.

Complications Of Dialysis

The complications of dialysis depend upon the patient’s condition, age, the existence of diseases other than renal failure, and many other factors.

The common complications of dialysis in individuals having only renal dysfunction are:

1. Sleep disorders
2. Anxiety
3. Depression.