The aim of Dialysis Access is to establish a circuit of high flow, high volume blood. This can be diverted though a dialysis machine and filtered of waste products.
The circuit is constructed by surgically creating a direct communication between the arterial and venous systems, short circuiting the usual pattern where the arterial blood goes down through the small capillaries in the tissues and then slowly rejoins the venous system. This communication is classically established between the radial artery at the wrist and the cephalic vein. The other common location is at the elbow between the brachial artery and the cephalic vein, although a communication can be formed in numerous places.
Mr Holdaway’s preference is to use veins for the fistulas as these are more durable and resistant to infection than an artificial vessel. After the fistula is constructed it needs to mature over a period of 6-8 weeks. During this period of time the veins dilate and the walls thicken in response to the high pressure blood. Then it can be accessed; this is generally achieved by placing 2 needles in the fistula. One of which will take blood to the machine and the other that will return it from the machine.
Surgery is generally performed under local anaesthetic where possible, with small incisions. The fistula is created using magnification and the wounds are closed with dissolvable stitches.
It is important to preserve the limb that is identified for fistula formation from unnecessary needle trauma to the veins. Hence blood tests, drips or other medical intervention should occur through the other arm. The fistula can be encouraged to mature by use of the arm, in particular squeezing balls. The fistula should be monitored each day by the patient to confirm it has a pulse or a buzz which is the feeling of the high velocity blood entering into the vein. If these are diminished compared with the previous day, the patient should contact Mr Holdaway’s office. If neither of these are present, the implication is that the fistula has blocked and is a matter of some urgency. The patient is to contact Mr Holdaway or the Vascular Registrar in the Geelong Hospital within 4 hours of noting the event, and admission to hospital will be immediately arranged.
Once the fistula is created it is subject to wear and tear as the process of placing needles in it results in damage to the fistula. This is normally well compensated as it is a living tissue and heals, however in a significant percentage of patients, narrowing will develop in the fistula which will threaten its long term function and may result in its sudden blockage. If this occurs then maintenance surgery that allows the fistula to work appropriately is required. If a fistula blocks badly and cannot be reopened, a new one may need to be formed.
Long term possible issues:
If the fistula becomes too large, the majority of the blood that is intended to go towards the hand can be diverted directly up the fistula and effectively ‘steals’ or takes blood from downstream tissues, this can result in a cold painful hand which is worse during dialysis. If this occurs the fistula may need to be surgically revised.
Information has derived from the patient education pamphlet “Vascular Access Surgery”, Royal Australasian College of Surgeons and published by Mi-tec Medical Publishing. The complete pamphlet is available from our rooms.