Dialysis (cont.)
When do patients require dialysis?
Patients usually require dialysis
when the waste products in their body become so high that they start to become
sick from them. The level of the waste products usually builds up slowly.
Doctors measure several blood chemical levels to help decide when dialysis is
necessary. The two major blood chemical levels that are measured are the
"creatinine level" and the "blood urea nitrogen" (BUN) level. As
these two levels rise, they are indicators of the decreasing ability
of the kidneys to cleanse the body of waste products.
Doctors use a urine test, the "creatinine clearance," to
measure the level of kidney function. The patient saves urine in a special
container for one full day. The waste products in the urine and in the blood are
estimated by measuring the creatinine. By comparing the blood and urine level of
this substance, the doctor has an
accurate idea of how well the kidneys are working. This result is
called the creatinine clearance. Usually, when the creatinine
clearance falls to 10-12 cc/minute, the patient needs dialysis.
The doctor uses other indicators of the patient's status to decide
about the need for dialysis. If the patient is experiencing a major
inability to rid the body of excess water, or is complaining of
problems with the heart, lungs, or stomach, or
difficulties with taste or sensation in their legs, dialysis may be indicated even
though the creatinine clearance has not fallen to the 10-12 cc/minute
level.
What types of dialysis are there?
There are two main types of dialysis: "hemodialysis" and "peritoneal dialysis."
Hemodialysis uses a special type of filter to remove excess waste products and
water from the body. Peritoneal dialysis
uses a fluid that is placed into the patient's stomach cavity through
a special plastic tube to remove excess waste products and fluid from
the body.
During hemodialysis, blood passes from the patient's body through a
filter in the dialysis machine,
called a "dialysis membrane." For this procedure, the patient has a specialized
plastic tube placed between an artery and a vein in the arm or leg (called a
"gortex graft"). Sometimes, a direct connection is made between an artery and a
vein in the arm. This procedure is called a "Cimino fistula."
Needles are then placed in the graft or fistula, and blood passes to
the dialysis machine, through the filter, and back to the patient.
In the dialysis machine, a solution on the other side of the filter
receives the waste products from the patient.
Peritoneal dialysis uses the patients own body tissues
inside of the belly (abdominal cavity) to act as the filter. The intestines lie in
the abdominal cavity, the space between the abdominal wall and the
spine. A plastic tube
called a "dialysis catheter" is placed through
the abdominal wall into the abdominal cavity. A special fluid is
then flushed into the abdominal cavity and washes around the
intestines. The intestinal walls act as a filter between this fluid
and the blood stream. By using different types of solutions, waste
products and excess water can be removed from the body through this
process.
Next: What does the patient do during dialysis? »
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