Civil Engineering Reference
In-Depth Information
16.2
Use of Cellulose for Treatment of Renal Failure
Cellulose is widely used for the treatment of renal failure. When the human kidney fails,
either as a consequence of disease (chronic renal disease) or following traumatic injury
or ingestion of poisons, the blood-borne metabolites of protein break down and water
that would normally be handled by the kidney accumulates and supportive therapy is
required to sustain the life. h e most widely used supportive therapy is haemodialysis.
About 1.8 million patients worldwide depend on long-term renal replacement thera-
pies. Globally the number of such patients is rising by about 6% annually. Asia, Latin
America, Africa and the Middle East are experiencing even higher proliferation rates
of up to 10%. Hemodialysis and acute dialysis belong to the category of extracorporeal
blood purii cation techniques, hemodialysis being the most widely used form of ther-
apy with an incidence of 89%. Hemodialysis used for patients who suf er from chronic
renal insui ciency and are not able to receive a kidney transplant. As an alternative to
hemodialysis, chronically ill patients can also receive peritoneal dialysis. By contrast,
patients suf ering from acute kidney failure usually receive acute dialysis.
Dialysis works on the principles of the dif usion of solutes and ultrai ltration of l uid
across a semipermeable membrane. Dif usion is a property of substances in water; sub-
stances in water tend to move from an area of high concentration to an area of low
concentration. Blood l ows by one side of a semipermeable membrane, and a dialysate,
or special dialysis l uid, l ows by the opposite side. A semipermeable membrane is a
thin layer of material that contains holes of various sizes, or pores. Fluid and molecules
(solutes) small enough to pass through the membrane, such as salt and low molecular
protein breakdown products, tend to move in the direction of decreasing concentra-
tion. Larger substances (e.g., red blood cells, large proteins. etc.) having larger dimen-
sion than the pore diameter are retained. h is replicates the i ltering process that takes
place in the kidneys, when the blood enters the kidneys and the larger substances are
separated from the smaller ones in the glomerulus; a network of capillaries that per-
forms the i rst step of i ltering blood.
h e two main types of dialysis are hemodialysis and peritonealdialysis, which remove
wastes and excess water from the blood in dif erent ways [4]. Hemodialysis is a therapy
in which the patient's blood is treated outside the body. In hemodialysis, the patient's
blood is pumped through the blood compartment of a dialyzer, exposing it to a partially
permeable membrane. During hemodialysis the patient's blood is pumped through the
blood compartment of an artii cial kidney or heamodialyzer, exposing it to a partially
permeable membrane called i lter membrane. h e dialyzer is composed of thousands
of tiny synthetic hollow i bers. h e i ber wall acts as the semipermeable membrane.
Hemodialysis removes wastes and water by circulating blood outside the body through
an external i lter, called a dialyzer, that contains a semipermeable membrane. h e blood
l ows in one direction and the dialysate l ows in the opposite. h e counter-current l ow
of the blood and dialysate maximizes the concentration gradient of solutes between the
blood and dialysate, which helps to remove more urea and creatinine from the blood.
h e concentrations of solutes (e.g., potassium, phosphorus, urea, etc.) are undesirably
high in the blood, but low or absent in the dialysis solution, and constant replacement
of the dialysate ensures that concentration of undesired solutes is kept low on this side
