Dialysis
dialysis is the process of removing
waste products and excess fluids from the body.
There are a number of reasons why a person may need dialysis.
Making the decision to begin dialysis is not easy because it entails a major
change in lifestyle, including a dependency on machines to maintain life.
However, for most people, a successful dialysis program results in a reasonably
normal life. Most people undergoing dialysis are able to eat a tolerable diet,
have normal blood pressure, do not have anemia, and avoid progression of nerve
damage and other complications.
For acute kidney failure, many doctors recommend dialysis when
urine output is low, and they continue the dialysis until the person’s blood
tests indicate that adequate kidney function has been restored. Short-term or
urgent dialysis can also be used to remove certain drugs or poisons from the
body.
For chronic kidney failure, doctors may recommend dialysis when
tests indicate that the kidneys are not removing metabolic waste products
adequately or when a person can no longer perform normal daily activities.
Dialysis may be used as long-term therapy for chronic kidney failure or as an
interim measure before kidney transplantation.
Dialysis usually requires the effort of a team of people. A
doctor completes a dialysis prescription, manages complications, and monitors
the process. A nurse monitors the person’s general well-being and mental health
and educates the person about such issues as exercise. A social worker arranges
transportation and home assistance. A dietitian recommends an appropriate diet
and monitors the person’s response to dietary changes.
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Reasons for Dialysis
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- Abnormal brain
function (uremic encephalopathy)
- Inflammation of
the sac around the heart (pericarditis)
- High level of acid
in the blood (acidosis) that does not respond to other treatments
- Heart failure
- Total body fluid
overload
- Fluid overload in
the lungs (pulmonary edema) that does not respond to other treatments
- A very high level
of potassium in the blood (hyperkalemia)
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Types of Dialysis
There are two types of dialysis: hemodialysis and peritoneal
dialysis.
Hemodialysis: In hemodialysis,
blood is removed from the body and pumped by a machine outside the body into a
dialyzer (artificial kidney). The dialyzer filters metabolic waste products
from the blood and then returns the purified blood to the person. The total
amount of fluid returned can be adjusted. A person typically undergoes
hemodialysis at a dialysis center, usually outside of a hospital but sometimes
located in a hospital.
Hemodialysis requires repeated access to the bloodstream. A
doctor can achieve temporary access by inserting a large intravenous catheter
in a big vein, usually one near the neck. An artificial connection between an
artery and a vein (an arteriovenous fistula) is surgically created to make
long-term access easier. In this procedure, typically the radial artery in the
forearm is joined with the cephalic vein. As a result, the cephalic vein
subsequently enlarges and becomes suitable for repeated puncture with a needle.
When a fistula cannot be created, a synthetic graft may be surgically connected
to an artery and vein. In this situation, the synthetic graft is punctured by
the needle for hemodialysis.
Heparin, a drug that prevents clotting, is administered during
hemodialysis to prevent blood from clotting in the dialyzer. Inside the
dialyzer, a porous artificial membrane separates the blood from a fluid (the
dialysate). Fluid, waste products, and electrolytes in the blood filter through
the membrane into the dialysate. Blood cells and large proteins are unable to
filter through the small pores of the membrane and so remain in the blood. The
dialyzed (purified) blood is then returned to the person’s body.
Dialyzers have different sizes and degrees of efficiency.
Dialysis treatment time is usually about 3 to 4 hours. Most people who have
chronic kidney failure need hemodialysis 3 times a week.
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Possible Complications of Hemodialysis
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Complication
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Cause
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Fever
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Bacteria or fever-causing substances (pyrogens) in the
bloodstream
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Overheated dialysate
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Life-threatening allergic reaction (anaphylaxis)
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Allergy to a substance in the dialyzer or blood tubing
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Low blood pressure
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Removal of too much fluid
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Abnormal heart rhythms
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Abnormal levels of potassium and other substances in the
blood
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Air embolus
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Air entering blood in the machine
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Bleeding in the intestine, brain, eyes, or abdomen
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Heparin being used to prevent clotting in the machine
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Infection
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Insertion of a needle into veins for hemodialysis access
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Peritoneal Dialysis: In
peritoneal dialysis, the peritoneum—a membrane that lines the abdomen and
covers the abdominal organs—acts as a filter. This membrane has a large surface
area and a rich network of blood vessels. Substances from the blood can easily
pass through the peritoneum into the abdominal cavity. A fluid (dialysate) is
infused through a catheter inserted through the abdominal wall into the
peritoneal space within the abdomen. The dialysate must be left in the abdomen
for a sufficient time to allow metabolic waste products from the bloodstream to
pass slowly into it. Then the dialysate is drained out, discarded, and replaced
with fresh dialysate.
A soft silicone rubber or porous polyurethane catheter allows
the dialysate to flow smoothly and is unlikely to cause damage. A catheter can
be put in place temporarily at the person’s bedside, or it may be surgically
put in place permanently. One type of permanent catheter eventually forms a
seal with the skin and can be capped when not in use.
Various techniques are used for peritoneal dialysis. In the
simplest technique, manual intermittent peritoneal dialysis, bags containing
dialysate are warmed to body temperature and infused into the peritoneal
(abdominal) cavity for 10 minutes. The dialysate is allowed to remain there
(dwell time) for 60 to 90 minutes and then drained out in about 10 to 20
minutes. The entire treatment can take 12 hours. Another technique is automated
cycler intermittent peritoneal dialysis, which can reduce the need for nursing
attention.
In continuous ambulatory peritoneal dialysis, the dialysate is
kept in the abdomen for much longer intervals. Typically, the dialysate is
drained and replenished 4 or 5 times a day. Generally three of these dialysate
exchanges are performed during the day, at intervals of 4 hours or longer. Each
exchange takes 30 to 45 minutes. An exchange is performed at night with a long
dwell time of 8 to 12 hours during sleep.
Another technique, continuous cycler-assisted peritoneal
dialysis, uses an automated cycler to perform short exchanges at night during
sleep, whereas longer exchanges are performed manually—without the
cycler—during the day. This technique minimizes the number of exchanges during
the day but prevents mobility at night because of cumbersome equipment.
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Possible Complications of Peritoneal Dialysis
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Complication
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Cause
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Bleeding
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A doctor may unintentionally perforate an internal organ
during placement of the catheter, or bleeding may occur where the catheter
leaves the body or within the abdomen
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Bleeding
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The catheter did not seal to abdominal wall
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Infection
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May occur if the dialysis procedure is not sterile
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Low level of albumin (a protein) in the blood
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Albumin loss in fluid removed during peritoneal dialysis
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Scarring of the peritoneum
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Inflammation and infection, the electrolyte content of
dialysis fluid, or the use of certain drugs
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High sugar (glucose) level in the blood
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Use of a peritoneal dialysate that has a high
concentration of glucose to remove water and sodium during dialysis
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Hernias of the abdomen and groin
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Continuous fluid expansion of peritoneal (abdominal)
cavity weakens barriers that normally prevent excessive movement of organs
and other structures
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Constipation
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Poor dietary fiber intake or calcium salts used for
treatment of high phosphate levels in the blood; may interfere with
dialysate flow into and out of the abdomen
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Choosing a Type of Dialysis
Many factors, including lifestyle, must be considered in
determining which type of dialysis is best for a person. Peritoneal dialysis
can be performed at home, eliminating the need for travel to a hemodialysis
center.
Doctors recommend hemodialysis for people with recent abdominal
wounds or abdominal surgery. Peritoneal dialysis is better tolerated in people
whose blood pressure fluctuates frequently between periods of high or normal
pressure and periods of low blood pressure. With hemodialysis, blood pressure
may be controlled simply by removing a sufficient amount of fluid during
dialysis. Otherwise, drugs to lower blood pressure may be needed.
Special Considerations
People undergoing dialysis need a special diet. In people
undergoing peritoneal dialysis, appetite is generally poor, and protein is lost
during dialysis. The diet should be relatively high in protein, roughly ½ gram
of protein per pound of ideal body weight a day. Salt, both the usual salt
containing sodium and the salt containing potassium, is restricted.
For those undergoing hemodialysis, daily consumption of sodium
and potassium is even more restricted. Foods high in phosphorus also may have
to be limited. Daily fluid intake is limited for people who have a persistently
low or a decreasing sodium concentration in the blood. Daily weighing is
important to monitor weight gain. Excessive weight gain between hemodialysis treatments
indicates that the person is consuming excessive fluid.
Multivitamin supplements are needed to replace the nutrients
lost through hemodialysis or peritoneal dialysis. Erythropoietin
(Some Trade Namesor darbepoietin may be given to stimulate the production of red
blood cells. Phosphate binders, such as calcium
carbonate (Some Trade Names
or calcium acetate, are used to remove excess dietary phosphate.
A low calcium level in the blood and severe renal osteodystrophy
may be treated with calcitriol (Some Trade Names(the
active form of vitamin D) and supplemental calcium.
People undergoing dialysis may experience losses in every
aspect of their lives. The potential loss of independence can be especially
distressing; coping with disruptions in lifestyles can be difficult. Many
people undergoing dialysis become depressed and anxious. Psychologic and social
counseling is often helpful to families as well as to those undergoing
dialysis. Many dialysis centers provide psychologic and social support. Dealing
with a loss of independence is helped when people are encouraged to pursue
their previous interests. People undergoing hemodialysis need to arrange for
transportation to and from dialysis centers on a regular basis. Dialysis
sessions may interfere with work, school, or leisure activities.
More than half of the people on long-term dialysis are 60 years
of age or older. Older people often are better able to adapt to long-term
dialysis than are younger people. However, older people undergoing dialysis may
become more dependent on their grown children or may not be able to continue
living alone. Older people are more likely to experience fatigue from
treatments. Often, family roles and responsibilities must be modified to fit
the dialysis routine, creating stress and feelings of guilt and inadequacy.
Children whose growth has been stunted may feel isolated and
different from their peers (see Social
Issues Affecting Children and Their Families: Illness in Children). Young
adults and adolescents coping with identity, independence, and body image
issues may find these issues further complicated by dialysis. Diet is an important
issue for children undergoing dialysis because children must receive enough
nutrients to support their growth.
Last reviewed/revised February 1, 2003
