Thread by @aishaikh

💥”Can’t Cannulate a Dialysis AV Fistula - How to Troubleshoot?”
#Tweetorial

⚡️Difficultly in AVF Cannulation can be due to:

☄️Stenosis
☄️AVF Depth
☄️Collateral Veins
☄️Tortuous & Aneurysmal AVF
☄️Cannulation-related Pain
☄️Skin conditions

@ASDINNews
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💥AVF infiltration causes:

⚡️Pain
⚡️⬆️es CVC dependence
⚡️Results in additional interventional & surgical procedures
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💥So how to troubleshoot?

⚡️Think of AVF as a circuit & NOT just an anastomosis b/w an artery & vein
⚡️ Problems anywhere in👇🏽 circuit can cause cannulation problems

⚡️Circuit:
☄️Heart (Pump)
☄️Artery (Inflow)
☄️Body of AVF (Conduit)
☄️Vein (Outflow)
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💥Stenosis in the inflow or outflow segment of the AVF can cause difficulty in cannulation👇🏽

⚡️Inflow Stenosis: Poor flow,
Negative Arterial Pressure, Poor Pulse Augmentation

⚡️Outflow Stenosis: Prolonged Bleeding, ⬆️ Venous Pressure,
Hyper-pulsatility
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💥Use Physical Examination to detect the location of the stenosis in the AVF

⚡️Physical Examination has excellent sensitivity & specificity to detect both inflow & outflow stenosis in an AVF
👇🏽👇🏽👇🏽
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💥What about the AVF depth?

⚡️AVF cannulation can be difficult if the AVF is too deep (no matter how good the AVF flow is)

⚡️The HFM study showed that the probability of successful AVF use declines with progressive increase in AVF depth👇🏽
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💥What about the Rule of 6s?
- it is not supported by evidence

⚡️The HFM study showed that successful AVF use declines as the depth of the AVF increases👇🏽, therefore one should not use a hard cut-off of 6mm to define the ‘ideal’ depth of an AVF
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💥If AVF is deep then cannulation with a longer needle can be attempted

⚡️Needle lengths available in the HD units in 🇺🇸 are:
💉3/5 inch
💉1 inch
💉1 1/4 inch

Rx for deep AVF include:
⚡️AVF superficialization
⚡️Liposuction
⚡️Buttonhole cannulation
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💥So far we have discussed Stenosis and Depth of the AVF as causes for difficult cannulation
⚡️ Collateral vein can cause cannulation problems BUT one must recognize that a collateral vein by itself is ‘rarely’ the cause of difficult AVF cannulation👇🏽
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💥Collateral Vein is usually the result of a stenotic lesion & it tends to disappear once the stenotic lesion is angioplastied as shown👇🏽
⚡️So a collateral vein by itself is usually NOT the reason for difficult AVF cannulation
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💥Another reason to avoid ligation or coiling of the collateral vein is that a well-developed collateral vein can be used for cannulation if the main body of the AVF is no longer usable as shown here👇🏽
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💥Aneurysmal & Tortuous AVF can cause problems w/ cannulation
⚡️Despite the fact that an Aneurysmal AVF is large, one can easily see in this image by @wasse_m how cannulation of this AVF can result in back wall infiltration & hematoma formation👇🏽
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💥Cannulation of Aneurysmal & Tortuous AVF:
⚡️US-guided cannulation can help
⚡️Buttonhole cannulation can be utilized
⚡️In some cases surgical intervention is needed👇🏽 (jump graft, aneurysmorrhaphy)
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💥Now let’s discuss a few rare causes of difficult AVF cannulation
⚡️Pain associated with AVF cannulation
⚡️Skin conditions affecting the AVF cannulation zone
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💥Pain-associated with AVF cannulation is an under-appreciated problem
⚡️Most common strategy is application of a local anesthetic cream (EMLA) over the AVF cannulation site a few minutes before cannulation
⚡️Some other interventions are shown👇🏽
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💥Skin conditions affecting the AVF cannulation zone can pose a significant challenge in cannulation of an AVF
A few scenarios are:
⚡️Allergic contact dermatitis
⚡️Keloid formation
⚡️Koebner phenomenon
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💥Allergic Contact Dermatitis over the AVF cannulation site can pose a diagnostic challenge
⚡️It can result from several causes & one has to meticulously consider all of these causes & avoid use of the likely culprit👇🏽
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💥Keloid formation over the AVF cannulation zone can occur as shown here👇🏽
⚡️Buttonhole cannulation can be a short-term solution
⚡️Seek the help of your dermatology colleagues in management of this condition
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💥Koebner’s Phenomenon: Skin lesions over lines of trauma (trauma from needles) can occur over the AVF cannulation zone
⚡️Can be seen in psoriasis & other conditions
⚡️Seek dermatology consult as systemic Rx may be needed (Steroids,CNIs,Anti-TNF agents)
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💥Summary:
⚡️AVF cannulation can be challenging
⚡️AVF stenosis & AVF depth are the most common causes of AVF infiltration
⚡️Utilize Physical Examination & Ultrasound to determine the cause of difficult AVF cannulation
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💥Here is the link to the Tweetorial on “Physical Examination of the Dialysis Vascular Access”
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https://twitter.com/aishaikh/status/1147682194732789765