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| Image Source: barwonvascular.com.au |
• An arteriovenous graft (AVG) is an artificial blood
vessel used to connect an artery and a vein.
• Grafts can be long enough to connect vessels in very
different parts of the body, if needed.
• Many materials can be used for AVGs. These materials can be divided into biologic and synthetic categories.
Graft Material
Biologic
• Some human biologic AVGs were made from a vein from a patient's leg.
• Veins from the umbilical cords of newborn infants were also used.
• But they have high risk of infection and aneurysms.
• Bovine (cow) and ovine (sheep) carotid arteries used for grafts were treated to remove proteins that would cause the human body to reject them.
• These grafts also had high rates of infection and aneurysms.
• Veins from the umbilical cords of newborn infants were also used.
• But they have high risk of infection and aneurysms.
• Bovine (cow) and ovine (sheep) carotid arteries used for grafts were treated to remove proteins that would cause the human body to reject them.
• These grafts also had high rates of infection and aneurysms.
Synthetic
• Synthetic materials are now used for nearly all grafts.
• The most widely used synthetic graft material today is expanded polytetrafluoroethylene, or PTPE.
• Collagen is another material that is used to make grafts.
• Grafts may be straight, curved, or looped. .
• Some designs provide a larger surface area for needle insertion.
Graft Procedure
• Construction of a graft is a surgical procedure that bridges an artery and a vein.
• During the surgery, incisions are made over the vessel entry sites.
• The vein is checked to ensure that there is enough blood flow.
• A tunnel is then made under the skin, and the graft is attached to one vessel, passed through the tunnel, and attached to the other vessel (anastomosis)
• Straight grafts are usually placed in the forearm (radial artery to basilic vein).
• Loop grafts are placed in either the forearm (brachial artery to basilic vein), in the upper arm, or the thigh,
• The most common graft in the upper arm is curved from the brachial artery to either the basilic or axillary vein.
• A new graft should be placed at least 3-6 weeks before use, unless a graft material is used that can be cannulated right away.
Graft Pros and Cons
Pros
• Graft take less time to mature before the first cannulation
• Graft size and blood flows don't depend on the maturation
• Grafts may also have larger cannulation areas than fistula.
• Grafts are often used in patients who are not good candidates for native fistula due to advanced age or other health problems, like diabetes, that dammage blood vessels.
• The biggest problems with all grafts are infection and thrombosis.
• Grafts develop stenosis at the venous anastomosis most commonly, and clot at a much higher rate than native fistula.
• No graft material now exists that is as good as a native vessel.
Starting Dialysis with a Graft
Wash your Hands
• Washing your hands is always the first step before you touch any dialysis access.
• Clean hands and gloves help keep bacteria on the skin's surface from being pushed into the patient's bloodstream by the needle.
Graft Assessment
• General outline for assessing graft:
• Look for:
• Swelling and redness
• Pain and tenderness
• Drainage from puncture sites, or from the skin around the graft
• Bruises
• Healing at previous cannulation sites
• Localized warmth and fever
Graft Assessment
• General outline for assessing graft:
• Listen for:
• Bruit- should be low-pitched and continuous
• Feel for:
• Pulse - feel for a soft compressible pulse
• Thrill-continuous (feel without compression only)
• Skin temperature - should be normal, not hot
• Hardness or pain
Confirm the Direction of Blood Flow
• To find the direction of the blood flow, feel the entire length of the graft
• Compress the middle of the graft with two middle ringers and feel for the pulse and/or thrill on both sides of the area to be compressed.
• You will feel the strongest pulse on the arterial side.
• The pulse or thrill will be faint or not palpable at the venous end.
Assess Blood Flow
• Every graft should have a strong flow of blood from the artery through the access and into the vein.
• The pulse of a graft feels like a pounding or buzzing with each heartbeat, as arterial blood is pumped by the heart to the rest of the body.
• This pulse, or thrill, should be strong, and you should be able to palpate it over the entire length of the access.
• The thrill should decrease over the venous portion of the graft.
• The sound should be strong and steady
• Like the thrill, the bruit should decrease over the venous portion of the graft.
Preparing to use a Graft
• The steps for preparing access skin, reducing pain from injection, applying tourniquets, and inserting needles use for grafts are exactly the same as in the fistula
Inserting Needles
Selecting a Cannulation Site
• Select a site that is at least a half inch away from any previous needle side.
• Do not cannulate near anastomoses
• The site should be at least one inch from an anastomosis, obstructions, or restrictions.
• Keep arterial and venous needles at least 2 inches apart.
Site Rotation of a Straight Graft
• To decide the needle site rotation in a straight graft, first divide the graft into equal halves at its middle. Use the middle as a reference.
• Cannulate the arterial half of the graft by moving toward the arterial anastomosis. Cannulate the venous half by moving towards the venous anastomosis.
• Each time you use a graft, space the needle sites equally along the length of the graft. Each needle insertion should be 0.25-0.5 inches from the last site. Place needles along three sides of a graft, not just along lie top.
Site Rotation of a Loop Graft
• To decide the needle site rotation in a loop graft, first divide the graft into equal halves at its middle. Use the middle as a reference.
• Cannulate the arterial half of the graft by moving toward the arterial anastomosis. Cannulate the venous half by moving towards the venous anastomosis.
• Rotate sites by equally spacing the sites along the graft. The space should be between 0.25-0.5 inches away from last site.
•Place needles along all three sides of the graft, not just along the top.
Needle Direction
• The venous needle is inserted in antegrade (in the direction of the blood flow) placement.
• This is needed to prevent excessive venous return pressure and damage to the blood cells.
• The arterial needle can be placed antegrade or retrograde (against the direction of blood flow)
• Retrograde placement of the arterial needle is preferred.
Graft Care Postdialysis
Postdialysis graft care is the same as postdialysis fistula Care.
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