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Arteriovenous Fistula

An Arteriovenous Fistula, is an abnormal connection between an artery and a vein. Here, blood flows directly from an artery into a vein, bypassing some capillaries. When this happens, tissues below bypassed capillaries receive diminished blood supply. It is considered as an abnormality when it happens spontaneously in the body. But for the purpose of long-term hemodialysis, this communication is deliberately created as a surgery.

Arteriovenous Fistula (AVF) - NU Hospitals

What is an Arteriovenous Fistula (AVF)?

An Arteriovenous Fistula (AVF) is direct communication between an artery and a vein. It is considered as an abnormality when it happens spontaneously in the body. But for the purpose of long-term hemodialysis, this communication is deliberately created as a surgery.

Why is it done?

During haemodialysis, blood is drawn out of the body, cleaned by the artificial kidney called dialyzer mounted on a dialysis machine and returned to the body. This process requires a supply of a fairly large quantity of blood (around 200ml per minute) to the dialyzer for efficient dialysis. The blood flow in a normal vein is very much less. By creating this surgical short circuit, more arterial blood will flow in the vein; this causes an increase in the size, thickness and blood flow in the vein. It then becomes easy to puncture this vessel for hemodialysis.

In which part of the body is it done, and will it be seen?

It is the joining of the blood vessels, under the skin. No tubes or needles are visible on the outside. It is usually performed in the non-dominant arm of the patient either at the wrist or elbow. Once the wound heals, only a thin, small scar of size 3 to 4 cm remains on the skin.

Is there any test prior to the procedure?

Your doctor will examine the hand vessels and may ask for Doppler study which accesses the vessel size and blood flow.

Is it a simple procedure?

Yes. It is usually done under local (only the area of surgery will be numb) or regional (a large part of the limb will be numb) anesthesia. The effects of anesthesia are temporary and will last for a few hours. It takes around one hour to perform this surgery. Only in cases of difficulty, does it take longer. If the blood vessels for any reason are not suitable at the distal part of the forearm or at the wrist, other sites may also be selected, like the elbow, the upper forearm or the upper arm.

Do I need to stay in the hospital?

The AVF procedure itself requires no admission. Associated medical conditions may indicate the need for hospitalization. If the blood flow through the surgical communication procedure is not optimum as felt by the doctor, you may require medications like Heparin to improve thinning of blood and blood flow through the fistula and hospital admission for observation. Otherwise, the patient will be sent home after a few hours.

Are there any precautions to be taken prior to the performing a fistula?

Once diagnosed with kidney failure, it is important to preserve the non-dominant upper limb so as to make it available for the procedure at a later date. Avoid taking any injections or giving blood samples for laboratory investigations from this upper limb.

Are there any precautions to be taken prior to performing an AV Fistula?

An antibiotic will be prescribed for 5 days if you also have a tube or catheter for dialysis at the time of this surgery; otherwise, you will be prescribed only suitable painkillers. Other than that, medications prescribed for chronic renal failure itself will need to be continued.

When do I visit the doctor after the procedure?

The first visit is scheduled on 10th post-op day for wound inspection and suture removal. Appropriate instructions will be given then.

What precautions do I need to take, once the fistula is performed on my arm?

Never wear anything tight around the fistula arm, because the blood flow may be blocked. Similarly, intravenous/intramuscular injections or blood pressure checks on that limb should NOT be done. Avoid sleeping on the arm or using it to lift unusual or unaccustomed heavy objects.

When can the fistula be used for haemodialysis?

A new fistula takes around 1 month to mature before it can be used for haemodialysis. To facilitate blood flow across the fistula, hand exercises in case of wrist AVF and straightening and bending at elbow for elbow AVF will be taught to you. These exercises increase the muscle activity in that limb.

Does the procedure always work?

Most of the time yes. Surgery may not be successful if veins are small, if the patient has diabetes related changes in the blood vessels or has received injections in the blood vessels before. You will then need a new fistula to be created at a different site.

How long does an AV Fistula work for?

If maintained well, it can work for a lifetime. There will not be good flow through AV fistula and it may not work effectively if the blood vessels are not good and there are frequent episodes of low blood pressure during dialysis or at any other time.

Will there be any complication in using the veins in the forearm for Haemodialysis?

Yes. Sometimes bleeding and haematoma can occur at the site of the puncture; rarely, infections can also occur. If there is poor flow through the AV fistula, there may be requirement for additional tests (Doppler scanning study and injection of contrast into AV fistula) to assess the cause for poor flow through the fistula; accordingly additional surgeries may be done to improve the fistula flow.

If there is a bleed from the AV Fistula site, what should I do?

Immediate compression on the bleeding area, maintained by either a thumb pressure or a tight bandage around the bleeding site is necessary. Pressure anywhere else will only serve to increase bleeding from the fistula site. Sudden bleeding can be life threatening and must therefore not be neglected.

What are the other immediate post operative problems that can occur?

There may be a watery discharge from the wound and this usually subsides on its own after a couple of weeks. This can be managed at home by keeping a clean washed and dried cloth over the wound and changing it when it gets wet. If there is swelling/edema of the arm, you may be asked to wear arm stockings for some time. Always contact your doctor if you think there is abnormal swelling, severe pain or an abnormal sensation in the forearm beyond the site of the fistula (steal syndrome).

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