By Chanelle Osborne- Renal Vascular Access Nurse
Between 1950 and early 1960, techniques and devices were developed that allowed repeated access to the circulation for haemodialysis. Some of these concepts were simple, like the cannulation of the iliac veins and vena cava by a double lumen plastic catheter while others were quite ingenious, such as the indwelling permanent vein Teflon cannulae. It wasn’t until 1965 that the first arteriovenous fistula was undertaken by Dr Appel in the USA.
The provision of adequate haemodialysis is dependent on repeated and reliable access to the central circulation. This access to the circulation is best provided by a primary arteriovenous fistula (AVF) and to a lesser extent arteriovenous grafts (AVG) and central venous catheters. (CVC)
The radiocephalic AVF is the most common fistula as it provides the best option for cannulation. The depth of the cephalic vein in the forearm is usually more shallow so easier to cannulate, has a longer length of vein allowing for better rotation of cannulation sites and allows for the option of a future fistula in the upper arm if another fistula is required. If the radiocephalic fistula is unable to be created due to calcified arteries and small fragile vessels then the brachiocephalic fistula is an excellent alternative.
An AVG can be made if there are issues with integrity of the native vessel, obesity (fistula too deep within the arm for cannula to reach) or a failed AVF. The most common AVG is the forearm loop; however there are many potential sites for AVG placements including the upper arm, thigh and chest wall.
If a fistula cannot be created or vascular access is required urgently then a CVC insertion can be done. The right internal jugular vein is the preferred insertion site for a CVC with respect to ease of access, shorter pathway through the vessel and it carries less risk of causing stenosis of the outflow veins of the arm.
The AVF is the ‘gold standard’ for haemodialysis vascular access as it remains the most reliable access due to its history of longer patency rates, less thrombotic events and much less infection rates. Currently in the Richmond and Clarence Health Service Group there is a ratio of 86 % AVF’S to 13% of AVG’S and 1% of CVC’S.
A functioning vascular access is paramount to the adequacy of each haemodialysis session. Establishing a good vascular access starts very early in the spectrum of care of the chronic kidney disease patient, often with education and vein preservation at stage 3 kidney disease and continuing throughout their life.
In patients with kidney disease both arms should be protected anticipating possible use for vascular access, particularly the non-dominant arm. Cannulation of the cephalic and basilic veins of both arms should be avoided. Appropriate sites for short term peripheral cannulation are the dorsum of the hands and flexor aspects of the wrists and forearms. Ideally, avoid the anticubital fossa. Venepuncture or cannulation of veins that are typically used by the vascular surgeon to form a fistula may render veins unsuitable for construction of an AVF.
The intent is to promote a culture of vein preservation in order to maximise the chance of patients with kidney disease to successfully maintain haemodialysis in the future.
Once a fistula has been constructed;
- bloods are not to be taken from the fistula
- cannulas are not be inserted into the fistula arm,
- blood pressures are not to be taken on the fistula arm
- pressure bandages are not to be applied to the fistula arm (unless advised by the vascular surgeon)
Once a fistula is created assessment of the fistula is preformed to detect the functionality of the patient’s access. The techniques of visual inspection, palpation and auscultation as the process of assessing takes a very short period of time, but is in fact the most important aspect of a patient’s care.
The thrill (a buzzing feeling created as arterialised blood is shunted into the vein) at the anastomosis is continuous and very prominent. The pulse should be soft and the fistula easy to compress. In the presence of anastomotic stenosis the thrill, which is normally continuous, is only felt during systole and a “water hammer pulse” is present at the anastomosis, as opposed to a thrill. Above the point in the fistula where a stenosis or narrowing of the vein is present, the thrill is typically weak and the vein is poorly developed.
Other complications of fistulas to be aware when assessing a fistula include steal syndrome, infection, aneurysm formation and thrombosis.
Assessment by the vascular surgeon is done at least 6 monthly. If a patient hasn’t seen their surgeon for some time a referral should be made. When making referrals if “indefinite referral” is indicated then the referral is ongoing.
Assessment of the fistula by health care workers is done from creation and throughout the patient’s dialysis life. Assessment becomes even more important in the pre dialysis population as patients are not always compliant with checking their access so early issues are not detected which can then result in a non-functioning fistula.
“Effective patient management is a critically important component of vessel management and is the responsibility of all health care providers.”