The Fistula: A Feisty Lifeline to Longevity

This blog post was made by Ant de Villiers on April 6th, 2017.
The Fistula: A Feisty Lifeline to Longevity

The tiny section of modified circulation known as a fistula, when rightly cared for, provides vital access for good dialysis for many years. This article summarises an online discussion on "needle spacing and angle/direction of needle entry, and will be of interest to those of us committed to ladder cannulation."

Spacing of Needles
For some who have a very short functional or accessible length of fistula, it is
re-assuring to learn that the standard 2 inches (5 cm) between needles, universally endorsed by clinics, is by no means necessary. This distance, it was believed, ensured that no dialysed blood entering the arm at the venous needle would be “sucked back” by the pump to travel again superfluously through the arterial loop of the machine (recirculated).

An investigation by Rothera et.al (2011) found by experiment that needles only 2.5 cm apart did not result in any re-circulation between blood returning and blood being withdrawn. Further, Fresenius needle packs come with detailed instruction how to use the needles. Their figure for needle spacing is minimum 1.5 cm.

Sharing these figures drew interest from ladder cannulators, but also from expert instructor Stuart Mott, who confirmed that in a well-functioning fistula (with a flow of 500) the needles can be virtually on top of each other. This was supported by nephrologist John Agar, who added that the fistula’s health was paramount and should be monitored by Transonic surveillance every 4 – 6 months. Dr. Agar advised that recirculation might only be an issue in the case of stenoses or other structurally limiting factors plaguing the vessel.

Mine is an upper arm fistula, and the legitimacy of close needle spacing is good news. Working on a craft during dialysis, I find that widely spaced needles do not respond uniformly to my arm movements, especially when the arterial needle is down near my elbow. Infiltration risk is greatly increased. By having the needles close together their ‘action’ during arm movement can be closely monitored. Importantly, the needles can be taped and secured side by side so that they respond virtually as a unit.

Angle and Direction of Needle Insertion
Once again a range of opinions emerged from an online search. Clinics tend to favour that the needle should enter at 25 degrees, while the Fresenius pamphlet asserts that 25 – 40 degree entry is acceptable. John Agar recommends a 45 degree angle.

After 10 months of self-cannulating, I still get all-too-frequent blood spurts at the arterial needle entry site, probably from too shallow an angle. I suspect the friction along the edges of the needle gliding in over a greater area of skin (because of the shallow angle) opens the lumen of the vessel or the surrounding capillaries prematurely. A deft thrust at 40 – 45 degrees, with a watchful eye on the flashback, makes more sense. I trialled this angle recently with promising results.

Finally the old "standard" of placing the arterial needle retrograde (against the direction of blood flow) has been put to bed. Early cannulators failed to visualise that the withdrawal of a retrograde needle left a flap of endothelium (inner lining of the vessel) facing into the blood current, forming thereby an efficient little scoop to direct blood out of the vessel into the surrounding tissue. You can easily visualise that a flap facing the other direction (in the case of the venous needle) would naturally be assisted to close as the blood current pushed it back into position.

Comments

  • Stuart mott

    Apr 6, 6:33 PM

    One other thing to consider is an aneurysm formations instead of cannulating on top of the aneurysm can you lay on the side at a 50 to 80 degree angle flat cannulation this will increase the life of the aneurysm it also help to reduce the size of it this was done by myself and by dr. Shenoy with the University of Washington in st. Louis developed this technique it increases the life of the accesss this is the same thing that is true for graphs instead of cannulating The graft on top all the time come in on the side if you need any further information on this please feel free to call me at area code 573-826-8237 thank you for allowing me to have this time

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    • Leong Seng Chen

      Apr 12, 5:50 PM

      I know nothing about 'aneurysm formation' as I am a rather new kidney failure patient about 29 months with AV Graft on my left hand upper arm in Singapore of South East Asia. I am on HD at Singapore National Kidney Foundation.

      I find very interesting when you are talking about the angular degrees of entering for needling schedule. I tried to encourage the nurses to do so as I am a technical man with reasonable tolerance of body-mind pain. They are quite firm & also lack of confidence may be. My AV Graft loop form is close 12 inches long but the nurses only confined to certain repeating areas causing the wear & tear with puncture on my AV Graft system. I still feel okay however I did my first ever angioplasty balloon without stent last year merely lasting for 2 years.

      I agree with you as our local hospital AV Graft specialists also encourage that there is no reason just to confine certain area of the whole loop AV Graft in order to increase the life of the access flow rate. Thank you!

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  • Amy Staples

    Apr 6, 4:08 PM

    The very first sentence could be misconstrued. I am currently on my 11th arm access, a bovine graft. Two of my fistulas failed almost immediately. The others worked for a while but eventually clotted off due to chronic low blood pressure. I recall one time when I called my support clinic telling them I needed a fistulagram and her response was "well, what did you do to make that happen?" The statement you make "The tiny section of modified circulation known as a fistula, when rightly cared for, provides vital access for good dialysis for many years." falsely leads the reader to believe that should they rightly care for a fistula it will be there to sustain them for many years. This is not so for some. Regardless of how carefully they attend to the health and vitality of their fistula or graft it still may fail. For those of us who suffer from chronic low blood pressure (12 years for myself), have repeated stenosis, and generally the vessels just react to the large blood volume, we will always struggle. There is no blame to the patient. No blame to the doctor or surgeon. Many times losing an access just happens. This article however provides wonderful tips on caring for a fistula in hopes that it WILL be long-lasting. For those of us whom require constant revisions or interventions remember you are not to blame. Thanks for the great write-up. Blessings

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    • Leong Seng Chen

      Apr 12, 6:05 PM

      I am new patient in Singapore under HD with AV Graft. I believe it got something to do with needling schedule or cannulation. This is quite a medical of technical aspect that no one can predict the outcome straight away. As regard to back flow of pressure on AV Graft system, yes, I do feel the stress & strain on my AV Graft during the 4 hours dialysis treatment with machines keep giving alarms etc especially around or toward the elbow portion or the extreme upper arm area. However it is tolerable stress & strain & it is off & on conditional factors.

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    • Ant

      Apr 6, 7:44 PM

      Thanks Amy, -you've had it rough with that lousy blood pressure!

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