DIALYSIS
According to a medical educator the three most important organs in
the sustenance of life are, the Brain, the Adrenal cortex and the KIDNEY.
The kidneys are a pair of bean shaped organs located at either
sides of the spine. They are the primary excretory organs in the body which are
responsible for the removal of wastes and excess water.
Like all the other organs the kidney is susceptible to damages but
worst still is that the damage of the kidney is life threatening. It is life
threatening because when the kidneys progressively damage to an extent that
they can only perform about 5% or less of their original functions; a condition
referred to as Chronic Kidney Disease (CKD), toxins accumulates in the body and
this leads ultimately to death. A CKD patient’s hope for a longer life
expectancy is DIALYSIS or Kidney transplantation.
Dialysis is an artificial process for removing metabolic wastes
and excess water from the blood and it is primarily a replacement for a diseased
or injured kidney. Dialysis anyways is not a cure for failed kidneys but rather
is the use of some specialized procedures to perform the excretory functions of
the kidneys. Inasmuch as dialysis alleviates the danger the vitiation of the
kidneys may have caused to the excretory system, the endocrine functions of the
kidneys still remain deficient. This deficiency of the endocrine functions of
the Kidneys is only compensated for by the exogenous administration of the
hormones that were naturally synthesized and secreted by the Kidneys; with
erythropoietin being the most important.
Principle of Dialysis
Dialysis works basically on two principles; the diffusion of
solutes and ultrafiltration of solvents through a semi permeable membrane.
Diffusion is the movement of molecules from areas where they are highly
concentrated to areas where they in low concentration. Ultrafiltration is the
passage of small molecules through a semi permeable membrane. It is worth
noting that in the Kidney, the first stage of urine formation is Glomerular
filtration (a.k.a Ultrafiltration), while the other two stages (Tubular
reabsorption and Selective reabsorption) are hugely dependent on the principle
of diffusion. In dialysis, blood flows through one side of the semi permeable membrane
while the dialysate (the dialysis fluid) flows through the other side of the
semi permeable membrane. The semi permeable membrane is a thin layered
perforated material and its pores are of varied sizes. This perforated membrane
permits the passage of solvents (mostly water) and smaller solutes but occludes
the passage of larger molecules (e.g. large proteins, formed elements of the
blood, etc).
Types of Dialysis
There are two main types of dialysis; Hemodialysis and Peritoneal
dialysis and they use different method (though the same principle) in the
cleansing and removal of excess water from the blood.
Hemodialysis
Hemodialysis is the type of dialysis that uses a special filtering
mechanism to remove the waste of metabolism and excess water from the blood. It
does this by circulating blood through a filter outside the body called
dialyzer (which contains the semi permeable membrane) via a plastic tube. The
dialyzer is a part of the dialysis machine. This treatment often requires a
surgical procedure in order to connect an artery and a vein in one limb (this
is referred to as arteriovenous fistula or graft depending on the specificity
of the procedure) or to tunnel a catheter in the neck. This is important
because this type of dialysis must be performed with a fistula, graft or
catheter. So in other words this surgical procedure is used to create what is
referred to as Access. When a patient is being prepared for the treatment, two
needles are placed into the access, these needles are then connected to the
tubes that carries blood to the dialyzer. The dialysis machine functions such
as to allow only a small amount of blood outside the body per given time and it
controls the timing, temperature, pressure and the excretion of wastes and
excess water from the blood as it pumps it through the dialysis system. After
the blood might have passed through the filter of the dialysis machine it is
returned to the body via another plastic tube. Hemodialysis treatments are
mostly done in an outpatient dialysis center though it can also be performed at
home and on the average it is done two or three times per week and each
treatment lasts about two and half hours.
Peritoneal Dialysis
In this type of dialysis a sterile solution containing glucose
(referred to as the dialysate) is introduced into the peritoneal cavity and
abdominal cavity using a tube. It is the peritoneal membrane here that acts as
the semi permeable membrane. The peritoneal membrane is a layer of tissue that
contains the blood vessels that lines the peritoneal cavity, abdominal cavity
and which supplies the internal abdominal organs. Through the process of
diffusion and osmosis (as a result of the difference in the osmolarity of
dialysate compared to the body fluid (blood)) waste products are drove from the
peritoneal membrane into the dialysate until it nears equilibrium and then the
dialysate is drained and replaced by a fresh one. This treatment is done
repeatedly about 4-5 times a day. Peritoneal dialysis does not equal the
efficiency of hemodialysis but the longer duration of this method of dialysis
gives it the same net effect as the hemodialysis. Peritoneal dialysis seems to
be more convenient since it does not require a routine appointment with the
clinic and it is a procedure the patients are taught to carry out by
themselves.
Author:
Orji Emmanuel
Physiologist
Comments
Post a Comment