This page explains about arterio-venous (AV) fistulae for haemodialysis and what to expect when your child comes to Great Ormond Street Hospital (GOSH) to have this procedure.
What is an arterio-venous (AV) fistulae?
A fistula (plural = fistulae) is made by a small operation to join an artery to a vein.
The blood vessels of the arm are chosen, either at the wrist or the elbow. The blood from the artery goes straight into the vein, which then becomes bigger and firmer. This means that it is possible to put two needles into the enlarged vein so that blood can be taken out of the body, sent through the dialysis machine and then returned through the second needle.
Why do we recommend an AV fistula?
An AV fistula is the best means of access to the blood stream for long-term haemodialysis. It means that there is no plastic dialysis line to become infected. This is particularly important as infections damage the lining of the blood vessel and cause it to become narrow. This may mean that a line cannot be placed into the same blood vessel again.
Obviously the number of blood vessels we can use is limited so we do not want them to ‘run out’ because they have been damaged. Sometimes our radiologist can rescue some vessels by putting a tube inside them (called a stent) to keep them open, but we would rather prevent this happening by creating a fistula as soon as possible. We particularly prefer to avoid putting plastic lines into the veins that are in the groin as the line then goes into the main vein that drains the body into the heart. If this gets blocked, transplantation may become difficult. Sometimes, if the main vein draining the arm becomes blocked, a fistula becomes impossible in the future. Also, if a plastic line in the heart becomes infected, it can cause infection on the heart valves causing them long-term damage.
Are any investigations needed before an AV fistula can be created?
The surgeon has to know that no narrowing has already developed in the blood vessels before he or she can do the operation. A venogram, which is a scan where dye is injected into a hand vein and its path is followed up the arm into the heart using X-rays, will show any narrowing. This also identifies the best vein to choose. If possible, the fistula is created in the non-dominant arm, that is, the one not used for writing.
What does the operation involve?
Your child will need an operation to create the fistula, which will be carried out under general anaesthetic and generally takes around two hours. The surgeon will make an incision (cut) in your child’s arm. This can either be towards the wrist or on the inside of the elbow. The incision will be about two centimetres long if the wrist is used or about four centimetres long if the inside of the elbow is used. Your child will come back to the ward with a dressing on his or her arm.
Are there any risks?
Every anaesthetic carries a risk of complications, but this is very small. Your child’s anaesthetist is an experienced doctor who is trained to deal with any complications. After an anaesthetic, some children feel sick and vomit, have a headache, sore throat or feel dizzy. These effects are usually short lived. Any surgery carries a small risk of infection or bleeding.
The fistula will not mature for about six weeks and during this time you may notice changes in the circulation in the arm. You should report any sign of loss of circulation, like blue fingernails or coldness to your doctor. The arm may also feel numb for a while after the operation.
Sometimes, the surgeon will not be able to create a fistula from the veins in your child’s arm. If this is the case, a section of vein will need to be grafted from elsewhere or an artificial blood vessel used to create the fistula. The fistula will still function in the same way, but the operation may take longer.
Looking after the AV fistula
A fistula must be looked after carefully. After surgery, the arm is wrapped in soft dressing to keep it warm. The nurses will check that the blood is flowing well through it by feeling for a ‘buzz’ or ‘thrill’ or listening to the blood flow using a stethoscope. We will increase your child’s ‘dry weight’ slightly on haemodialysis so that he or she do not become dehydrated, which can lead to the development of clots that might block the fistula. Your child may be given aspirin, which also decreases the chance of clotting in the fistula. We will teach you how to look after the fistula before you go home.
Dialysis using the AV fistula
It usually takes about four to six weeks for the vein to become big enough to use. Once the fistula has settled down, it can be used to access your child’s blood system for each dialysis session. Sometimes we start with just one needle and then use two when the fistula is ready (mature).
The nurses will put some local anaesthetic cream on your child’s arm to help minimise the discomfort when inserting the needles. These needles will then connect your child’s blood supply to the machine. At the end of the session, the needles will be removed and the access points covered up with plasters.
There are two methods used for inserting needles into a fistula:
Ladder technique: The needle sites are moved up and down the fistula each time it is used.
Buttonhole technique: The needles are inserted into the same holes each time so that a tract is formed. Once the tract has formed, we can then insert ’blunt’ needles into the fistula.
Your dialysis nurse will discuss the most appropriate technique with you and your child. In some cases, your child can be taught to insert the needles themselves if they would feel comfortable with this.
Sometimes problems can occur during the first few weeks of using the fistula. These are very common and usually nothing to worry about, but may seem quite a concern at the time.
Common problems are:
A needle is inserted but no blood can be withdrawn from the fistula, or the blood flow is not good enough. This is usually because the needle is not in quite the right place so the dialysis nurse will usually try to reposition the needle. If this does not work the needle will be removed. The nurse may need to reattempt the needle insertion, however, this will be discussed with you and your child at the time.
The needle is inserted successfully into the fistula, but the area around the fistula begins to swell and become suddenly painful. This can happen at any time during the dialysis session. The nurses will often refer to this as the fistula ‘blowing’. It is caused by blood leaking from the fistula into the surrounding tissues. This may cause severe swelling and bruising around the fistula and can be quite painful. In this case, the needle will be removed and no further attempt at inserting a needle will be made. Your child will be asked to raise their arm and an ice pack may be applied to limit the swelling.
The fistula will usually be rested until the swelling and bruising have improved. A fistula ultrasound may be requested to ensure that the swelling is not restricting the fistula in anyway. It is very important if this happens that you check the fistula regularly as outlined below and inform the hospital if the fistula seems faint or absent.
Occasionally there will be repeated unsuccessful attempts at inserting a needle into the fistula over a number of dialysis sessions. This may simply be because the fistula needs more time to mature, in which case the fistula will be rested for a few more weeks. However, it can sometimes indicate a problem within the fistula that may require surgery. An ultrasound of your child’s fistula will be organised to establish the exact cause of the problem and the options will be discussed with you.
- Take anti-clotting medicines as prescribed (aspirin).
- Avoid becoming dehydrated during illness, exercise and hot weather. Check with the hospital if you are concerned about fluid intake.
- Avoid tight clothing on the fistula arm.
- Wear jewellery or wristwatches on the other arm.
- Avoid blows and injury to the fistula.
- Good hygiene is important to prevent infections.
- Do not take part in contact sports such as rugby and judo.
- Keep the arm warm especially in cold weather.
- Gently exercise the fistula arm to promote blood flow.
- Never let anyone take blood from the fistula arm or put a cannula in it.
- Only a dialysis nurse can needle fistulae.
- Blood pressure must not be taken on the fistula arm.
Going home with an AV fistula
The fistula must be checked regularly during the day. Get into the habit of checking it on waking, at meal times and before going to bed. You will be given a stethoscope to place on the skin above the fistula where you will hear a distinct ‘whoosh’ noise. This sound should be present continually. You should also be able to ‘feel’ the pulsation of the blood as it flows through the fistula over the area where the incision was made. This is called the ‘thrill’ or ‘buzz’. The nurses will show you how to assess the fistula prior to discharge.
The needle sites begin to bleed again after dialysis – this can happen occasionally. Make sure you keep some gauze with you and use this to apply pressure directly onto the needle site in the same way that the nurses do when they remove the needles. Keep applying pressure for at least five minutes before checking to see if the bleeding has stopped. If it has, apply a new plaster. If it continues to bleed, apply pressure again until it stops. If it continues to bleed after 30 minutes, contact the hospital for advice – you may need to be seen at your local hospital for assessment.
The fistula stops buzzing – If the fistula is faint, give your child 100-200mls of fluid and then check it again. If you are in any doubt about the fistula, contact the hospital for advice straightaway, as the fistula will need immediate attention. Be prepared for an admission and possibly surgery.
The fistula becomes red or painful – This may indicate infection so contact the hospital immediately. Take your child’s temperature and be prepared to come into hospital as an infected fistula needs urgent treatment.
Your child feels dizzy, faint or ‘dry’ or has diarrhoea and/or vomiting – This may cause dehydration leading to reduced flow of blood through the fistula and possible clotting. Your child will need to increase his or her fluid intake in order to prevent dehydration. Admission for rehydration with IV fluids may be necessary.
The appearance or feel of the fistula, skin or arm alters – For example, damaged skin, any abnormal lumps, swollen or painful area, and altered sensation in the arm. Any of these signs should be reported to the hospital immediately.
You think the fistula may have been injured – If your child receives a blow to their fistula, it could cause serious damage. You should check your child’s fistula for swelling, bruising and any altered sensation in their arm and that it is still buzzing as normal. The hospital should be contacted immediately. If your child’s fistula is punctured or cut, you must call 999 immediately – it is likely to bleed very heavily and is therefore a medical emergency. While you are waiting for medical assistance, you should apply as much pressure to the wound as you can and raise the limb. If your child begins to feel faint or dizzy, make sure that they lay down.
To the child on dialysis, the fistula is a lifeline and must be looked after carefully. An AV fistula usually has a longer lifespan than other forms of permanent haemodialysis access. There are no bulky dressings and infection is rare. With good care, including an ultrasound check every six months, the fistula can last for years.
Last reviewed by Great Ormond Street Hospital: March 2013
Ref: 2012F0759 © GOSH Trust March 2013
Compiled by the Nephrology department in collaboration with the Child and Family Information Group.
This information does not constitute health or medical advice and will not necessarily reflect treatment at other hospitals. If you have any questions, please ask your doctor. No liability can be taken as a result of using this information.