About Hemodialysis
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Why do I need hemodialysis?
Hemodialysis is often started when symptoms or
signs of kidney failure appear. These may include:
- Nausea, vomiting, anorexia, and fatigue due
to "uremia", a buildup of urea and other waste
products in the blood that occurs when the kidneys
are unable to eliminate wastes from your body.
These wastes are poisonous to you when they
reach high levels.
- High levels of potassium in the blood ("hyperkalemia")
- Fluid overload
- High levels of acid in the blood
Hemodialysis is sometimes used for people who
have acute (sudden) kidney failure.
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Are
there any risks associated with hemodialysis?
Dialysis is always used with extra caution in
people who have acute kidney failure. Dialysis
can cause low blood pressure, an irregular heart
rhythm (cardiac arrhythmia) and other problems
that can sometimes make acute kidney failure worse.
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What
is a hemodialysis access?
Because of the need to remove blood from the body
and replace it during hemodialysis, a means for
accessing the patient's blood circulation - called
"vascular access" -- is necessary. There are three
different techniques for this, some of which are
used interchangeably: dialysis fistula, graft
and catheter. All of these techniques are able
to withdraw and replace large amounts of blood
at the same time - about one quart per minute.
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What
is a fistula?
The most desirable form of hemodialysis vascular
access is called a fistula. To make a fistula,
a surgeon connects an artery to a vein in the
forearm or upper arm. With time, usually one to
three months, the vein enlarges and becomes ready
to receive the needles used to withdraw and replace
blood during dialysis. A fistula can last for
many years if the vein enlarges and the fistula
"develops". About three-quarters of fistulas develop
or mature. During the time that a fistula is developing,
if hemodialysis is necessary, another form of
vascular access will be necessary, usually a catheter.
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What
if my fistula does not develop?
A non-developing or non-maturing fistula occurs
in up to one fourth of patients. There are two
causes for a non-maturing fistula: narrowing of
a vein or too many competing veins. Interventional
radiologists can either open up the narrowed vein
with a balloon (balloon angioplasty) or close
off the competing veins using several techniques.
About three quarters of people with non-maturing
fistulae will benefit from one or both of these
treatments and have their fistula develop so it
can be used. These procedures are done as an outpatient
and take about an hour.
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Protect
your veins!
In order to make a fistula you must have good
arteries and good veins. While you generally cannot
do much about your arteries, you are in control
of your veins. As soon as a diagnosis of kidney
failure is made you should be very careful not
to let anyone puncture the veins of your forearm
or upper arm for blood draws, intravenous medications,
or for any other reason. The hand veins should
serve this purpose. By doing so, you protect your
important veins so the surgeon will have a better
chance of making a fistula. Even after a hemodialysis
access is created in one arm, you should protect
the veins of the opposite arm.
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What
is a dialysis graft?
In some patients, the arteries and/or veins are
not suitable for making a fistula. In these patients,
a shunt (or graft) can be used as an alternative
form of dialysis access. A graft is a piece of
plastic tubing that is inserted by a surgeon and
connects the artery to the vein. Unlike fistulas,
grafts do not need to "develop" and are ready
for use in most instances by four weeks after
placement. A catheter may be necessary for dialysis
during this waiting period. The disadvantage of
grafts is that they do not last nearly as long
as fistulas and can develop narrowing and clotting
more frequently. In addition, grafts can get infected
-- something which does not happen very often
with fistulas.
Just as with fistulas, narrowing veins with grafts
can be detected before they clot if the appropriate
screening techniques are used. These include self-examination,
measuring flows during dialysis with a special
machine, and checkups by an interventional radiologist.
Once an abnormality is detected, you need to be
scheduled to have it treated by Interventional
Radiology as quickly as possible. It is very important
that patients keep their appointments with Interventional
Radiology so that clotting does not occur. If
clotting does occur it can be treated by an interventional
radiologist.
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What
is a dialysis catheter?
Catheters are considered the least desirable form
of dialysis access. Catheters come in two forms:
a short-term (non-tunneled) and longer-term (tunneled)
form. The best use of catheters is to provide
short-term access for dialysis for patients whose
kidney function is expected to recover, or for
patients whose kidney function is not expected
to recover but who have a graft or fistula in
place and are waiting for it to mature.
A catheter is inserted by an interventional radiologist
or a nephrologist (kidney doctor) through one
of the large veins -- usually the jugular -- into
the larger veins in the center of the chest near
the heart. This procedure can be done as an outpatient
and lasts less than an hour. The best results
with catheter placement are achieved when imaging
guidance is used, including ultrasound to place
a needle into the vein and X-rays to guide correct
positioning of the catheter.
Catheters have the advantage that they can be
used for dialysis immediately after they are placed.
Patients also tend to find them attractive because
needle sticks are not necessary to remove and
replace blood during dialysis, as occurs with
a graft or fistula. However, catheters have significant
disadvantages and risks. These include:
- Risk of infection -- approximately half of
all patients with catheters develop a life-threatening
infection during the first year the catheter
is in place.
- Catheters do not provide flow rates for dialysis
that are as good as grafts or fistulas. This
can result in patients not receiving enough
dialysis or requiring a longer dialysis session.
- Catheters can cause the veins they are placed
into to clot off or develop narrowing (stenosis).
In fact, with certain chest veins called the
subclavian veins (just under the collarbone),
the risk of clotting or narrowing is approximately
50%. Therefore, subclavian veins should never
be used for catheters except in very rare instances
when all other veins have been used up. Patients
can help to prevent this complication by not
allowing their doctors to use the subclavian
veins for dialysis catheters, rather insisting
on the jugular veins where this complication
is quite uncommon (less than 10%).
- Many patients find catheters uncomfortable
and/or unsightly.
Despite all of the problems with catheters, patients
may need to have them in place for a short period
of time while a fistula develops or a graft heals.
Generally, this should be less than three months
for a fistula and one month for a graft. Some
patients will need to have a catheter placed while
they are waiting for a visit to the surgeon for
a graft or fistula. It is very important that
patients in this situation make and keep their
appointments with the surgeon so there is no delay
in getting the graft or fistula made. The sooner
the catheter comes out, the better.
Besides inserting dialysis catheters, interventional
radiologists also treat problems with catheters,
including infection and clotting. These problems
are most commonly treated by exchanging the catheter
for a new one in a brief outpatient procedure
lasting less than an hour.
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Detecting
problems with grafts and fistulas
While a fistula is considered the best kind of
access, problems can occur, including vein narrowing,
or "stenosis," and clotting, or "thrombosis".
Both of these problems can be treated by an interventional
radiologist with excellent results. Treating the
vein while it is narrowed but not clotted yields
the best results and takes the least amount of
time. There are a number of ways to detect narrowing
in the vein before thrombosis occurs, through
"screening" by your Dialysis Unit. Once an abnormality
is detected it is essential that you be seen by
the interventional radiologist as soon as possible
to treat the problem.
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What
if my dialysis access is clotted?
If the graft or fistula is clotted, interventional
radiologists use a variety of procedures to dissolve
or remove the clot. First, X-ray pictures (fistulogram)
are taken which show the area(s) of narrowing
(stenosis). Then, a balloon is inserted to open
up the clogged area(s) in the vein, in a procedure
called an "angioplasty". A clot can be removed
either with drugs that dissolve it or mechanical
devices that remove it or break it up into very
small pieces.
These procedures are all done as an outpatient
using conscious sedation and local anesthesia
(numbing medicine). In conscious sedation, medicines
to relieve anxiety and discomfort are given through
an intravenous tube. In order to receive conscious
sedation, you must not have had anything to eat
or drink six hours before your procedure. Also,
you may not drive home after receiving conscious
sedation, so be sure to arrange a ride home after
the procedure.
After angioplasty, your self-examination should
return to normal. Screening tests should be repeated
in the Dialysis Unit to ensure that they too have
returned to normal. While balloon angioplasty
is effective in dialysis access it may need to
be repeated periodically, usually every six months.
When angioplasty is unsuccessful, interventional
radiologists have other alternatives available
to them. Generally, the first of these is to repeat
the angioplasty. If this is unsuccessful, depending
upon the location of the narrowing, a small metal
tube called a "stent" can be inserted in the same
outpatient procedure as the angioplasty. This
is done quite uncommonly and more often in the
chest than the arms. When angioplasty is unsuccessful,
a patient may be referred to a surgeon for a procedure
called a "revision of the graft or fistula".
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What
is dialysis access self-examination?
Your dialysis graft or fistula should feel like
a cat purring when it is functioning well. You
can feel this best by putting the palm of your
hand over your graft or fistula. You should examine
at least three different points on the access.
If you feel the access pulsing (beating like a
drum), this is abnormal and you should inform
the Dialysis Unit staff immediately so a fistulogram
and angioplasty can be scheduled. The best way
to detect problems with your graft or fistula
is to examine it on a regular basis (such as on
your dialysis days) and note changes from the
last self-examination. If you cannot feel a pulse
or a thrill, your access is probably clotted and
you may wish to call the Dialysis Unit to inform
them so you can get it treated.
Arm swelling is also abnormal and may be an indication
of a problem in the veins in the chest. Some swelling
after a surgical procedure may be normal but this
should get progressively better. Swelling that
lasts more than a few weeks after surgery should
be investigated with a fistulogram.
Tenderness or redness over a graft is a sign
of infection and should be reported to the Dialysis
Unit staff immediately. In a clotted fistula,
some tenderness or redness may be normal, but
never in a clotted graft.
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What
are the screening tests for a failing dialysis
access?
Screening for a failing dialysis access can be
done in several ways. The simplest is self-examination.
Other techniques available during dialysis include
flow measurement (using a special machine connected
to your dialysis tubing) and pressures (measured
by the dialysis machine). When a graft or fistula
is failing, the flow goes down and generally the
pressure goes up. Other signs that an access is
failing include prolonged bleeding after needle
removal and trouble puncturing the access. Any
of these abnormalities should prompt a visit to
Interventional Radiology for a fistulogram and
balloon angioplasty as needed.
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Reviewed by:
Scott Trerotola, MD
January, 2003
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