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Vascular Access
 
 Your life vein
 

Hemodialysis works by running your blood through a circuit of tubing into an artificial kidney or dialyzer. As it is a closed and continuous circuit, it is necessary to remove blood and return it at the same time. The whole circuit including the tubing and the dialyzer contains less than 200 milliliters of blood. Blood must be pumped within the circuit at a minimum speed of 400 milliliters/minute.

 

Whatever type of vascular access you have, it is essential to understand how best to take care of it. Without your access you will be unable to dialyze. This is why many patients refer to their access as their 'lifeline'.

 

These are three types of hemodialysis access:

•    The arterio-venous fistula

•    The arterio-venous graft

•    A venous catheter (with two separate channels)

 

No matter what type of access you have, as a hemodialysis patient, it is important to take great care of the veins in both of your arms. Repeated cannulation of these veins for blood tests, or insertion of drips, will cause progressive scarring to veins that may be needed in the future for your dialysis. You must alert any non-dialysis nurses or doctors to this fact so that they can use alternative blood vessels. Any essential blood tests can be taken from the veins of either hand. Blood tests or blood pressure should never be taken from your fistula arm.


 
The Arterio-Venous Fistula

 
A fistula is without doubt the best way to ensure adequate and problem-free dialysis, and is considered the gold standard of vascular access for patients. For adequate dialysis it is necessary to pump the blood at a minimum speed of 400 milliliters/minute. To do this we create a special vein in your arm, called a fistula. The fistula is created by making a small incision in both the artery and the vein in your wrist (or sometimes your leg) and joining them together. Once joined, the blood from the artery is diverted into the vein and this is called a fistula.

 
 

Having a fistula created is a minor surgical procedure carried out by a surgeon. It is usually carried out under local anesthetic but occasionally a general anesthetic is required.

 

Once the fistula has been created it cannot be used immediately, and is usually left to heal and develop for a few weeks. If you place your hand lightly over the incision you will feel a buzzing sensation in your wrist. This is called a 'thrill'. If you ask your nurse, you can use a stethoscope to listen to the whooshing or buzzing sound. This is called the 'bruit'. This is the arterial blood being diverted into the vein and is a very good sign that tells you that your fistula is working well. If you notice that this buzzing stops, you should contact the unit immediately as it may be a sign that the fistula has stopped working. It is also important to ensure that your fistula is used by only dialysis-trained health professionals.

 

Once created, your fistula will need to develop and mature. You may notice that the veins in that arm become larger and more prominent. This is exactly what is supposed to happen. Your nurse may show you some gentle arm exercises to do, such as squeezing a rubber ball, to help develop the veins further. The idea is to encourage the veins to increase in size to enable easy insertion of the dialysis needles for your dialysis treatment. Usually it takes at least six weeks before we will use the fistula for dialysis.

 

If your fistula is too new to use and you need dialysis, it may be necessary to insert a venous catheter in your neck to use for dialysis until your fistula is ready.


 

 
Arterio-Venous Graft (AV Graft, Graft)
 
If your surgeon decides that your own blood vessels are not ideal to provide adequate vascular access, they may advise the insertion of a graft. Like an AV fistula, a graft works by joining an artery to a vein. However, instead of your own blood vessels a small piece of synthetic tubing is used to make the connection. This can be done in your arm or your leg. The graft feels a little bit firmer than a fistula. Once created, the graft will be cannulated in the same way as a fistula.
 

Both access placements are done by a doctor in an operating theater. Having good vascular access is the basis for high-quality hemodialysis treatment, and subsequently a major contributor to your well-being – that's why it is very often called 'your life vein'!

 

You can lengthen the life of your AVF by taking care of your life vein. This is done by following hygiene guidance and regularly monitoring your vascular access (eg, by listening to the sound of the bloodstream) and using surveillance programs for further assessment of the vascular access.

 

Inserting needles (cannulation) into your AV fistula or graft: whether you have an AV fistula or graft, two needles must be inserted each time you dialyze. Nobody likes the idea of having needles put in, and it is this part that many patients dread the most. However, your dialysis nurse is highly skilled and experienced and will ensure that the procedure is as quick and pain-free as possible. Often patients say that it is not nearly as bad as they had feared, and they quickly get accustomed to it. Occasionally a needle may be poorly positioned and need to be removed and replaced

.

Venous Catheter
 
If you do not have a fistula or a graft, or if either has failed, you will need a venous catheter. The catheter is inserted via a large vein in your neck. The catheter usually has two lumens or compartments. Blood is removed via the arterial lumen and returned via the venous lumen.


 
 
A venous catheter is considered a temporary measure to allow you to dialyze until you have a functioning AV fistula. Although a catheter may seem at first to be preferable to having needles inserted at each dialysis, the use of venous catheters has several disadvantages. These include:

 
Infection

In the environment there are millions of microbes and bacteria. Most of the time, these bacteria do not harm us because they cannot get into our bodies – our skin is a vital protective barrier.

 

In hospitals, patients often undergo surgical procedures where the skin is punctured – as in surgical wounds or insertion of catheters etc. These devices immediately compromise the body's defenses by providing direct access for bacteria to get into the body. Having a catheter as your vascular access significantly increases your risk of exposure to these bacteria.

 

A patient with a catheter is about 10 times more likely to suffer a serious bloodstream infection than a patient with a fistula, and spend many more days in hospital each year than patients with a fistula.

 

Therefore, the following need special care:

•    The entry site of your catheter in your neck. Keep this area clean and dry, and covered with a clean dressing. Do not wear clothes that may rub around this area and cause soreness or inflammation, which in turn may become infected. If you notice any redness or pus in this area, inform your healthcare professional immediately.

•    Both lumens: Keep both ends of the catheter clean and secured. If the caps come loose or come off, ask your nurse to replace them.


 
 
Basic guidelines

•    Always wash your hands before touching your catheter

•    Always contact the clinic if you have a temperature or feel unwell

•    Always ask your nurse for advice on how to care for our catheter

•    Always inform non-dialysis health professionals that you have a catheter

•    Never let anyone (other than dialysis professionals) to handle your catheter

•    Never let health professionals to use your catheter to take blood, or administer drugs or IV drips

•    Don't be afraid to insist that health professionals wash their hands before handling your catheter

 


Clotting

Blood within the smooth blood vessels is liquid and constantly moving within the circulation. When blood is exposed to the outside environment through a cut or graze, or to foreign substances such as a catheter, it begins what is called the 'clotting process'. Chemicals in the blood act on the blood cells to make them clump together to form a clot or a scab.

 

When you have a venous catheter, a common complication is clotting and obstruction of the catheter. To try to prevent this, a drug called heparin is injected into the lumens of the catheter when it is not being used for dialysis. The heparin is just enough to sit within the lumen of the catheter and does not enter your bloodstream. Sometimes, however, a small amount of blood still backflows into the catheter and forms a clot.

 

If you get a clot inside your catheter, your nurse will try to suck it out with a syringe. If that does not work, the catheter may be flushed with a clot-dissolving drug, which usually clears it. Sometimes, however, the clot cannot be dissolved and the catheter will need to be replaced.


 
Poor positioning, poor flow and inadequate dialysis
At the time of insertion, your doctor will carefully check that the catheter is accurately placed with the tip sitting in the upper right chamber of your heart. This is the ideal position to produce the best blood flows for dialysis.