Arteriovenous Fistula Creation

Dr Jason Toniolo

Arteriovenous Fistula Creation

The word fistula is a medical term for connecting two hollow organs or tubes.

An arteriovenous fistula specifies this connection between an artery and a vein.

These are surgically created to enable long term, long-term dialysis for patients with kidney failure.

Why do I need a fistula to undergo haemodialysis?

The main reason is that a fistula provides access to a vessel that has enough flow

When using haemodialysis, your blood volume is passed through a machine that washes the blood, removes waste products, and then replaces the blood into circulation.

To ensure your blood volume passes through the machine, you must have access to a vessel with a very high rate of flow that enables the machine to pump blood through the circuit quickly. If dialysis were done through veins only (for example, a vein in the forearm, similar to when you have blood taken), it would only be able to sometimes wash 20-30ml of blood per minute, depending on how big the vein was in your forearm. When undergoing proper haemodialysis, the machine typically runs at 300-400mls per minute, and it still takes 3-5 hours to wash your blood 3x a week thoroughly. If you could only wash 20-30ml per minute, you would never be able to dialyse fast enough.

Why can an artery that already exists not be used for dialysis?

Arteries have high flow rates but are extremely important as they provide segments of your body with blood. If arteries in your arms get damaged or blocked, you might not have enough blood left for your hand. They are also deep and can be hard to place needled in. Fistulas enable the veins under your skin (which you would typically get blood tests taken through) to have the same flow as the deeper arteries but with the safety of puncturing a vein

How is a fistula created

Fistulas have been made for countless years using open surgical techniques. There is a new method using minimally invasive techniques, which is discussed in the EndoAVF article.

treatment options

Procedural steps

An ultrasound is used to mark out the diameter of the veins and arteries pre-operatively
When the appropriate location is selected, you are brought into the hospital and either undergo general anaesthesia, a local anaesthetic or a regional block (injection in the shoulder to numb the whole arm).
A small cut is made between the artery and vein that is to be used
The artery and vein are attached using a series of tiny stitches
The wound is then closed with stitches, and you can go home on the same day or the next day, depending on your home situation

Post-operatively

As blood begins to rush from the artery (high pressure) to the vein (low pressure), you will feel a buzzing when you place your hand over the vein (now referred to as ‘the fistula’). The buzzing is known as a “Thrill”.
Over the following six weeks, the vein, now under high pressure, will grow in diameter, thickening its wall to accommodate the increased pressure and blood volume.
You will have an ultrasound at six weeks to ensure the fistula is ready to be used

Risks of surgery

The risks of fistula creation are low but can be severe.

Risk of infection – unless prosthetic (fabric) pieces are inserted to make the fistula, then infection is usually treated with antibiotics without issue
Risk of bleeding – sometimes, the fistula can bleed, and you may need to be taken back to the operating room to stop the bleeding
Risk of ‘steal’ syndrome – when we borrow blood from the artery and divert it to the vein, that sometimes means the fingers and hand do not have enough blood. Steal can cause pain, numbness, or even progress to death of the skin on the tissue of the hand, which requires surgery to correct. Steal can occur immediately after the fistula is created or years later if the fistula grows and starts stealing too much blood
Risk of nerves in the hand not having enough blood – this is very, very rare. It is known as ischaemic monomelic neuropathy. It is essentially blood being stolen from the nerves of the forearm by the fistula. Extreme pain is identified after the fistula is created, and without expedient occlusion of the fistula, loss of hand function will occur.
Failure of the fistula to mature – sometimes, there is not enough flow down the arteries to support fistula maturation
Blockage of the fistula – the fistula may develop clots in it and eventually block off, either straight away or years later.

Aneurysms of the fistula – after years of passing needles into the fistula, it can weaken the wall, and the fistula can bulge. It can turn from a 6mm to a 2cm diameter vessel. These can be surgically corrected if required.