(1) Properly functioning kidneys are vital to life. Remember the main functions of the kidneys: maintenance of electrolyte and water balance and excretion of waste products. If the kidneys do not function properly, waste products (such as excess minerals, urea, toxins, and drugs) start to accumulate in the body. These waste products must be removed for the person to continue to live. Dialysis is a technique used to remove waste products from the blood and excess fluids from the body when the kidneys are not functioning normally.
(2) Dialysis is the diffusion of dissolved molecules through a semipermeable membrane. These molecules tend to pass from an area of greater concentration to an area of less concentration. In patients who have defective kidney function, the accumulation of urea and other nitrogen waste products can be reduced by passing the patient's blood through a dialysis machine. Thus, dialysis removes waste products from the bloodstream and restores the patient's electrolyte balance. Dialysis cannot cure renal failure, but dialysis can accomplish some of the renal functions so that the patient continues to live. A patient on dialysis uses either a machine with a semipermeable filtering membrane, or his own peritoneal membrane to cleanse his blood.
b. Methods of Dialysis. Two methods of dialysis presently in use are hemodialysis and peritoneal dialysis. Both methods are based on the principle of diffusion of dissolved molecules through a semipermeable membrane.
(1) Hemodialysis. In this method, a sheet of cellophane functions as the semipermeable membrane in the dialyzer machine. A patient using this method must usually have dialysis two or three times a week. The process is as follows:
(a) Blood leaves the body through an artery.
(b) This arterial blood passes through the machine's blood pump.
(c) Blood is filtered to remove any clots.
(d) Blood passes through the dialyzer machine.
(e) The blood passes into the venous blood line.
(f) Blood is filtered again to remove any clots.
(g) The blood then flows through an air detector.
(h) Finally, the blood returns to the patient through the venous blood line.
(2) Peritoneal dialysis. In this method of dialysis, the peritoneum acts as the filtering membrane. Dialyzing fluid is introduced into the peritoneal cavity at intervals. The peritoneum is a large surface area and acts as the diffusing membrane filtering the blood in the peritoneal blood vessels. The dialyzing solution remains in the peritoneal cavity for 15 to 30 minutes. Then the solution is allowed to drain out. The severity of the patient's condition determines the length of time the dialysis process takes. Time varies from 12 to 36 hours. Those patients with chronic renal disease can learn how to do their own dialysis treatments at home. This permits patients to resume most of their normal activities.
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