As a dialysis patient, you should be knowledgeable about your vascular access and your options.  The word "access" refers to the method or manner in which blood is removed from the body to flow through the dialyzer.  There are different types of vascular access from which you may choose.  The selection of vascular access is made by you, along with your family, the nephrologist, and the surgeon.  The surgeon will utimately decide what can or cannot be done.  It is highly preferable that the access be placed long before dialysis is necessary.  In cases where dialysis is required in an emergency situation, some of the choices below will be limited.

 

There are four basic types of vascular acess:

     1.  Arteriovenous Fistula (AVF)

     2.  Arteriovenous Graft (AVG)

     3.  Venous Catheter (of which there are several types and locations)

     4.  Venous Catheter Port (a device which utilizes a catheter and two valves which is implanted under the skin.)

 

1.     An AV fistula (AVF) is a vessel constructed by connection of an artery   with a vein.  It can be surgically created in the forearm or upper arm and utilizes your own veins.  It has the longest life span (usually measured in years) and has the lowest risk for infection and septicemia (infection of the bloodstream).  It also has the lowest blood clotting rate of any access.  Creation of the AVF is usually the easiest, simplest and safest procedure.  It is performed as outpatient surgery and is the least painful.  A disadvantage is that it must be placed early enough before dialysis begins to allow time for the vein to enlarge and for healing to occur.  In older patients, patients with diabetes or overweight patients, this process may take months.  In addition, sometimes AV fistulas cannot be created because previous venous needlesticks and placement of IV lines may have caused damage to veins.  During the dialysis treatment, two needles are placed in the AV fistula-one to remove blood and one to replace blood.

 

The surgeon will play a major role in deciding if a fistula can be created.  There are special helpful studies with ultrasound with which your veins can be studied (called "mapping")  You should ask your nephrologist to refer you to a surgeon who has placed many AV fistulas and is experienced.  It is estimated that approximately 70% of patients could (should) have AV fistula.  From a medical perspective, the AVF is by far the most preferable access.

 

2.  An AV graft (AVG) is an artificial blood vessel which is surgically inserted in the forearm, upper arm or thigh.  Unlike an AV fistula which used the body's own veins, this device utilizes a synthetic material, usually polytetrafluoethylene (PTFE).  The life span of this device is significantly less than the AV fistula and is usually measured in months to years.  The AV graft carries a moderate risk of infection in speticemia-roughtly 2 times greater than that of the Av fistula.  There is a greater degree of pain associated with the creation of the AV graft, since the PTFE material must be surgically tunneled under the skin.  This access cannot be used until the swelling has receded, which usually requires 3-6 weeks.  During dialysis treatment two needles are inserted into the graft-one to remove blood and one to replace blood.

 

In general, the time between placement and when the AV graft can be used is somewhat less than the AV fistula.  The AVG is most often used when the surgeon has determined that you do not have an adequate vein and he/she cannot create an AV fistula.  From a medical perspective, it is the acess of second choice.

 

3.  Venous Catheters are hollow tubes-somewhat smaller than a drinking straw and 1-2 feet in length - which are placed in the jugular vein in the neck. This is done in such a way that one end of the catheter is tunneled under the skin to come out in the upper chest wall.  The other end of the catheter is placed in the large vein at the opening of your heart.  This is called a "tunneled" venous catheter.

 

Venous catheters can also be placed in a vein at the shoulder (subclavian vein) or the groin (the femoral vein) without tunneling.  These are called "percutaneous" catheters and they generally are used in the hospital and sometimes in an out-of-the hospital dialysis unit for a very short period of time-usually 2 to 6 dialysis treatments.  These are not recommended to be used longer than 2 to 4 weeks.  There is a very high rate of blood infection and destruction (stenoisis or narrowing) of the veins with these particular types of hemodialysis catheters.

 

The tunneled AV catheter (discussed above) is preferred over the percutaneous catheter but still has a higher rate of infection and blood clotting than does the AV fistula or AV graft.  However, the tunneled catheter has the advantage of immediate use in emergency situations.  It does not require the placement of needles into the skin during dialysis.

 

You should be aware, however, that the infection rate for catheters is roughtly 5-7 times greater than that of the AV fistulas.  In fact, over half of cuffed catheters must be removed within one year due to infection.  These infections may lead to complications such as heart valve infections which may result in deazth.  The use of a venous dialysis catheter requires very careful handling by a trained technician, nurse and/or physician.  The blood clotting rate is high, and though they may sometimes be de-clotted in the facility, there are times when the patient must return to the hospital for catheter de-clotting and/or replacement.

 

From a medical perspective, this is the least desirable acess but will be necessary if the surgeon or radiologist believe there is no possiblility of an AVF or AVG.  Whenever possible, you should urge your nephrologist, surgeon or radiologist to search for a means and a site to place an AV fistula or AV graft.  Before committing to a permanent catheter, you should request your nephrologist to seek a second opinion from a surgeon with experience in placing AVF's or AVG's.

 

4.  Venous Catheter Ports.  This is a new device involving two catheters, similar to those described above, and also consisting of an injection site made up of two valves which are connected to the catheters.  This device is inplanted entirely under the skin on the chest wall and the catheters enter the same neck or jugular vein as would the tunneled catheter noted above.  Again, the catheter tip is positioned just at the entry to the heart.  During dialysis treatment, two needles are placed through the skin, one into each valve-one to remove t=blood and one to replace blood.  These devices were created to avoid having catheters exit directly from veins to the outside of the body.  It is intended to be a temporary acess until an AVF or AVG can be created, but in some patients, may be considered a permanent device when an AVF or AVG is not possible.

 

These devices have only been in use for approximately six to eight months.  Infection and blood clotting rates in early studies provided to the FDA showed aceptable reates that were similar to or better than infection rates in catheters.  Since not as much is known about  how these devices perform in practice compared to other forms of acess, wer are carefully monitoring complications such as infection and blood clotting with these new devices.

 

 

Information provided by Fresenius Medical Care:

 FMCNA CS-1-145 01/02