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Peripheral Vascular Surgery Society
Patient Information with Questions and Answers about
common vascular diseases and their treatment
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Common Questions about Hemodialsis Access:
Introduction
Common Questions about Hemodialysis and its attendant
procedures.
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Introduction
Hemodialysis is therapy a nephrologist uses to treat a patient's lack of adequate
kidney function. when the kidneys fail, fluid and other body waste products
accumulate as they cannot be eliminated in the urine. It is one mode of renal
replacement therapy. You may be told that peritoneal dialysis, or renal transplantation
or viable options for chronic renal failure, but if your nephrologist determines
that you would need hemodialysis, a surgeon must create the access by which
you could be dialyzed by.
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Frequently Asked Questions: FAQ's
1. What do you mean by hemodialysis?
Answer: Hemodialysis takes patient blood and circulates it through a mean to
filter out excess fluid and waste before the blood returns to the body. Most
patients need 2-3 sessions a week to maintain their state of health. Each session
can last from two to four hours, depending on individual condition and the flow
rates their access generates
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2. How do I get hemodialysis?
Answer: Patients need a way for blood to be removed from the body to go to
the dialysis machince. Then the blood has to be returned to the body. There
are temporary catheters inserted into a vein that can be used. More durable
modes of access include creation of an ateriovenous fistula (AVF) or with a
prosthetic AV graft (AVG).
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3. Why not just leave the catheter in - like a big Intravenous?
Answer: Longterm catheters develop frequent problems that increase over times
beyond 2-4 weeks. They can lead to serious infections, central vein blockages,
and inability to generate enough flows for the machines.
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4. "Flow Rate" seems to come up frequently. What is it and how does that matter
to me?
Answer: Flow rates are how many ccs a minute can be passed
through the dialyzer. Good dialysis strives to acheive at least 400ccs a minute.
Adequate dialysis can occur with 250ccs a minute. Catheters can deliver 250-350
ccs per minute. Depending on the quality of a patient's vein used for an AVF
or AVG, a surgically created AV access can deliver over
600 ccs per minute.
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5. OK, so what is an AVF?
Answer: An AVF (arteriovenous fistula) is where a surgeon connects a small
artery to a vein that runs underneath your skin. Over time, the vein then grows
larger from the pressure and influence of carrying arterial blood. The vein
then can be punctured with needles through the skin so blood can be carried
to the dialyzer. The radial artery and cephalic vein near your wrist is a common
artery/vein pair that can support an AVF. A successful AVF must develop a vein
that is near the skin, and can grow to high flow rates. If an arm's veins near
the wrist cannot support an AVF, one can possibly be created near your elbow.
This would then let the veins in the upper arm grow for use. A good AVF can
take between 4 and 8 weeks to develop enough for good use. 70-80% of good AVFs
are working at one year, and then out to five years for many patients. Because
an AVF is natural artery and vein, infection is very inlikely.
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6. So why might I get an AVG?
Answer: Many times the superficial veins in the arm for use as a good AVF have
been damaged by intravenous therapy. An AVG typically uses a plastic tube as
a conduit placed inbetween a deeper artery and vein. The plastic part lies under
the skin, allowing the dialysis staff to place the needles needed. An AVG can
be used immediately if it s absolutely required. However, it is best to allow
10-21 days of healing. AVGs have less patency and period of use than an AVF.
Only 50% have a 12 month primary patencyin many centers. Secondary patency (after
a procedure to salvage the graft) still is around 50-60% at two years. AVGs
also can get infected, as the plastic undet the skin is a place an infection
can set up in and not be treated except by removing the AVG. Also, the vein
that the AVG plugs into can get internal scarring, or intimal hyperplasia.
As the vein outflow narrows, the graft can clot off and close up.
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7. What be done for a clotted or poorly working AVG?
Answer: At many vascular centers, a multidisciplinary approach maximizes useful
life from hemodialysis access. Interventional radiology physicians can sometimes
suck clot out from a clotted access. Many of the discovered narrowing (or stenoses)
can be dialated and enlarged with an angioplasty balloon. Other times, the graft
material has just fallen apart, or the clot cannot be removed through a catheter.
Then a surgical team can open up most grafts and clean them out under direct
vision. If the vein that was supporting the AVG is too narrow, a short bypass
to a new, larger vein can save use of the AVG. Sometimes, a whole new AVG in
a new site has to be placed. Essentially all dialysis access procedures are
done as outpatient procedures.
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We at the PVSS hope this information has answered what may be some of your
questions about hemodialysis access for the treatment of chronic renal failure.
Sincerely,
Henry C. Veldenz, M.D., F.A.C.S. for the PVSS
Last updated 10/26/2000 Copyright 2000 Peripheral Vascular Surgery Society
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