When a patient has been diagnosed with chronic kidney disease he or she is staged according to the national kidney foundation staging system. If they are staged as 4 to 5 then preparation is made for dialysis in the medium to short term. If the patient chooses hemodialysis as the preferred method of renal replacement therapy then the next step is an access procedure.Q: Why is access necessary?
A: Hemodialysis requires blood to flow through a filter known as a dialyser. Toxins leave the blood in the dialyser by travelling across a semi permeable membrane and entering another fluid known as the dialysate. The dialysate and blood generally flow in opposite directions. The rate of flow of blood and dialysate is very important to the rate of removal of toxins. Blood must therefore be able to flow from the body very quickly at up to rates of 450 to 500 ml/min. The blood needs also to be returned at the same rate to prevent a fall in blood pressure. The dialysis access is the means by which blood is removed from and returned to the body.
Q: Are there different types of access?
A: Yes. There are two broad methods of gaining access to the blood stream for dialysis. One is known as a catheter which consists of a semi rigid tube with two lumen one for blood going to and the other blood going away from the patient. The other access type is known as an AV fistula which is fashioned from the veins found within your body.
Q: Is any one form of access superior to another?
A: An AV fistula is produced by a surgical procedure on the native blood vessels of your own body. This is therefore superior and more durable than a catheter. A catheter being a foreign body resides partially inside the blood stream and partly outside in order to attach to the tubing of the dialysis machine. This produces a ready site for direct infection of the blood stream and significant illness can result.
Q: How do i take care of my access.
A: The access is the lifeline of the dialysis patient without it dialysis cannot be done. Patients should make every effort to protect the access site from moisture trauma and pressure. An AV fistula is very delicate even the simple act of taking your blood pressure on the arm that has an AV fistula may be enough to destroy it. Patients should always be mindful of their access and report any changes in colour loss of pulsatility or sudden pain or swelling at the access site as an emergency.
[...] Catheters are a form of dialysis access that are grossly inferior to other methods of accessing the blood stream for the purposes of dialysis. The use of catheters at first dialysis are associated with increased risk of life threatening infection and decreased dialysis adequacy and thus decreased survival and quality of life. The choice to place a catheter as a form of first access should only be made when no other access is possible. However discussing the types of possible access and the pros and cons in a manner that allows the patient an educated choice will take time hence the need for early refferal. [...]
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