In order to perform hemodialysis, the blood has to circulate through the dialysis machine at a rate of 200-500 milliliter per minute. Peripheral veins cannot support such high blood flow rate; hence the need to place/create a dialysis access.
There are three types of hemodialysis access:
Tunneled Dialysis Catheter.
Arteriovenous Graft (AVG).
Arteriovenous Fistula (AVF).
Tunneled Dialysis Catheter:
It is a catheter that is placed in one of the big veins in the neck (Jugular vein), under the clavicle (Subclavian vein) or in the groin (Femoral vein). The external part of the catheter is threaded (tunneled) under the skin to help reduce infection and patient's discomfort.
Can be used immediately after placement.
Can be placed with minimal sedation.
No needle sticks.
More prone to infection and malfunction.
Can damage the vein that is placed into; causing narrowing (stenosis) and potentially jeopardizing the ability to place a permanent dialysis access (AVG or AVF) on the same side of the damaged vein.
Need to be kept dry to minimize the risk of infection (no swimming or showering)
You can find more information about dialysis catheters at:
Arteriovenous Fistula (AVF):
A surgical connection is made between an artery and a vein (usually in the upper extremity). This lead to higher than normal blood flow into the vein, causing the vein to get larger and thicker. This high blood flow and vein enlargement allow the vein to be cannulated and used to get adequate blood flow to support the hemodialysis procedure.
Fistula is usually created in the non-dominant arm. When it is created at the level of the wrist, it is called radial-cephalic AVF. Fistula created at the elbow, can be either brachial-cephalic or brachial-basilic depending on the vein used.
A good and well-functioning fistula has the following advantages:
Less chance of infection.
Less chance of malfunction.
Last longer than AVG or tunneled dialysis catheter
No restriction on swimming or showering
Disadvantages/problems related to AVF:
Takes 6-12 weeks from creation, before it can be used
Some patients with peripheral vascular disease (narrowing of the arteries of the extremities), can develop pain, numbness and discoloration of the hand (Steal phenomenon) after creation, due to diversion of some of the blood flow into the fistula and away from the hand. When this occurs, the fistula may have to be closed
Not every patient can have a well-functioning AVF, due to damaged or small veins or arteries, especially elderly women and patients with peripheral vascular disease
Arteriovenous Graft (AVG):
AVG is a tube made out of artificial material that is sutured on one end to an artery and to a vein on the other end. It is completely threaded under the skin. It can have different configurations (straight AVG, Loop AVG or a partial-loop AVG) and locations (Forearm, Upper arm or upper thigh).
Advantages of AVG:
Usually can be used within 2-3 weeks, after the incision is healed and the swelling has resolved
Disadvantages of AVG:
More prone to infection
More prone to malfunction
Has a shorter life-span than a well-functioning AVF
The role of interventional nephrologist in the management of dialysis access
An interventional nephrologist is a nephrologist (Kidney specialist) who has undergone special training to be able to manage dialysis access malfunctions using interventional techniques. Interventional techniques uses minimally invasive image-guided procedures to diagnose and treat problems of the dialysis access. These procedures are usually done using local anesthetics with or without conscious sedation. Nephrologists are very familiar with the medical management and care of the dialysis patients and are therefore more qualified to handle and coordinate the dialysis patient's care before and after the access procedure.
Examples of dialysis access interventional procedures:
-Thrombectomy of clotted AVG or AVG:
Is the removal of clots from a clotted AVG or AVF in addition to correcting any narrowing in AVG/AVF, draining veins or feeding arteries using balloon inflation across these lesions (Angioplasty).
-Angioplasty of AVG/AVF:
Sometimes the AVG/AVF malfunctions cause prolonged bleeding after dialysis needle removal, inadequate dialysis, or strong access pulsation. This usually happens due to narrowing(s) in the AVG/AVF, draining veins or feeding arteries. These conditions can be managed by the interventional nephrologist using balloon angioplasty.
-Placement or exchange of tunneled dialysis catheters.
-Management of immature AVF:
Some fistulae do not develop into a working access after 6-8 weeks of creation (Immature AVF); this is usually due to narrowing(s) in the AVF, or the feeding artery. These narrwoings can be managed by balloon angioplasty. In some cases there is no stenosis, but the problem originates from the presence of accessory vein(s) that drain(s) the blood away from the main fistula. These accessory vein can be obliterated (closed) using coils or sometime ligation (suturing) after making a small incision.
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