Kidney Dialysis Vascular Access Management

VASCULAR ACCESS FOR HAEMODIALYSIS

Vascular access refers to the method in which kidney failure patients can undergo haemodialysis.  The vascular access is used to remove the patient’s blood so that it can be filtered through a dialyzer machine to cleanse the blood and remove excessive fluid.   There are 3 types of vascular access:  an implanted Central Venous Catheter, an ArterioVenous Fistula (AV) or an ArterioVenous Graft (AVG).  

CENTRAL VENOUS CATHETER/PERMANENT CATHETER

Catheter access, sometimes called a Permanent Catheter or CVC (central venous catheter), consists of a plastic catheter with two lumens which is inserted into a large vein (usually the internal jugular vein or the femoral vein) to allow large flows of blood to be withdrawn from one lumen, to enter the dialysis circuit, and to be returned via the other lumen. 

There are 2 types of CVCs, tunnelled and non-tunnelled: 

  1. Non-tunnelled catheter access is for short-term access (up to about 14 days) and the catheter emerges from the skin at the site of entry into the vein.
  2. Tunnelled catheter access (Permanent Catheters), involves a longer catheter, which is tunnelled under the skin from the point of insertion in the vein to an exit site some distance away. It is usually placed in the internal jugular vein in the neck and the exit site is usually on the chest wall. The tunnel acts as a barrier to invading bacteria.  Although called a Perm Cath, such tunnelled catheters are designed for short- to medium-term access because infection is still a frequent problem. We do not recommend placing a Perm Cath for more than 6 months.

CENTRAL VEIN STENOSIS (CVS)

  1. CVS is a serious problem associated with the long- term use of Perm Caths. 
  2. The catheter is a foreign body in the vein and often provokes an inflammatory reaction in the vein wall. This results in scarring and narrowing of the vein, often to the point of occlusion. This can cause problems with severe venous congestion and swelling in the face, neck and chest and the upper limbs.

Treatment of CVS requires a procedure known as a Venoplasty.  In this procedure, a vein in the arm or in the leg is accessed and a sheath (tube) placed.  Through the sheath, a wire is passed across the CVS and a balloon used to dilate the narrowing thus improving the vein drainage.  Sometimes if the narrowing is very resistant to simple balloon dilatation, then a stent (metal supporting strut) may be placed across it to keep the vein open.  The Venoplasty and Stenting can be done under local anaesthesia or mild sedation and as a day surgery procedure.

ARTERIOVENOUS FISTULA (AVF)

  1. AVFs are recognised as the preferred access method. 
  2. To create a fistula, a Vascular Surgeon joins an artery and a vein together using stitches. 
  3. Fistulas are usually created in the nondominant arm and may be situated on the hand, the forearm, or the elbow. 
  4.  A fistula will take a number of weeks to mature, on average perhaps 8-12 weeks.
  5. The advantages of the AV fistula use are lower infection rates, because no foreign material is involved in their formation, higher blood flow rates (which translates to more effective dialysis), and a lower incidence of thrombosis. The complications are fewer than with other access.
  6. Creation of an AVF is usually done under local anaesthesia and as a day surgery. 

ARTERIOVENOUS GRAFT (AVG)

  1. AVGs grafts are created when an artificial vessel is used to join the artery and vein.
  2. AVGs are inserted when the patient’s native veins are too small or blocked and does not permit an AVF creation.
  3.  AVGs mature faster than fistulas, and may be ready for use as early as 48 hrs post creation.   
  4. AVGs are made of synthetic material and are at greater risk of becoming infected.