How to Cannulate an EndoAVF

EndoAVFs often have multiple outflow veins for cannulation. Therefore, it is important to confirm the cannulation zones in advance. Ideally, a cannulation guide will be given to the clinic by the creating physician.3 This guide should include but is not limited to:

• Cannulation zone (see Figure 2)
• Blood flow direction
• Vessel depth below the skin

Figure 2: Surgical AV Fistula (Single Outflow) vs. EndoAVF (Multiple Outflow) Cannulation Zones (highlighted in yellow)

Figure 3: Example EndoAVF Cannulation Zone Cannulation map.
Photo courtesy of Dr. Alejandro Alvarez.

Check for cannulation sites below the elbow as well, as an endoAVF can be quite deep in the forearm. The median cephalic and median basilic veins are often used. If the treating physician did not provide a guide (see Figure 3), ultrasound can be used to find cannulation sites (see Figure 4).

Figure 4: Use of Ultrasound to Find EndoAVF Cannulation Sites
Ultrasound assessment of cephalic vein for potential cannulation sites. Photos courtesy of Dr. Neghae Mawla.

Caution: Teach your patients to refuse blood draws, blood pressure, or IVs on their fistula arm. With no anastomosis, care providers might not see an endoAVF and could damage the vessels.3 Patients also need to protect an endoAVF and use the 1-minute check (Look, Listen, Feel) each day.

Consider the patient’s comfort when choosing cannulation sites—a patient may want to be able to read, use a computer, or knit. If you do not know, ask the patient.³ A needle that crosses the elbow crease will keep a patient from bending his or her arm. As always, be gentle to avoid infiltrating the side or back wall of the vein with the needle tip. Per KDOQI guidelines, a rope-ladder technique is a preferred method for cannulation, but the buttonhole technique can be used as well, per clinic protocol.³

Rest the patient’s arm on a chairside table with a pillow or pad for cushioning, and sit down to cannulate until the needles are securely taped in place.³ A lower blood pump speed (about 350 mL/ min) may be needed until optimal flows can be reached.³ Follow your clinic’s policies and procedures for needle size and blood pump rate.

Cannulation Steps

1

Review the cannulation map provided by the creating physician, if available.

2

Wash your hands. Put on gloves.

3

Apply a tourniquet for assessment.

4

Examine the endoAVF as you would a surgical AV fistula:

• Look
• Listen
• Feel

5

Remove tourniquet when assessment is complete.

6

Remove gloves and put on new, clean gloves.

7

Prepare the access skin and let sites dry completely.

8

Apply a tourniquet.

9

Use needles that are the correct length for the endoAVF:

• Assess the fistula arm to guide your choice of needle length.
• Your clinic’s standard needle length (1-inch or 1 1/4-inch) may be acceptable. A shorter needle (3/5-inch) may be better for superficial cannulation zones and/or thinner patients.3
• Follow your clinic’s protocol for needle size progression, just as you would for a surgical AV fistula. No changes are needed for endoAVFs.

10

Place the Inflow/Arterial needle:

• Place the inflow needle (arterial) into the highest flow vessel. Most often, a 20–35° angle will be used.
• The arterial needle tip can point retrograde or antegrade, depending on unit protocol.
• An endoAVF feels softer than a surgical AV fistula when the needle tip enters the vessel. A blood flashback will occur but may be less strong than a surgical AV fistula. Wet cannulation may be helpful.3
• Consider a shallow needle angle for superficial veins. The needle angle depends on the endoAVF depth and the physical build of the patient.

11

Place the Outflow/Venous needle:

• Point the venous needle tip towards the venous return. The outflow (venous) needle can be placed into:
• The same vessel as the inflow needle, but more proximal (closer to the heart).
• A parallel vessel—if its diameter is large enough (≥ 4 mm). NOTE: The outflow needle can be more distal (closer to the wrist) than the inflow needle if it is placed into a different vein than the inflow needle. More than one outflow vessel may be arterialized with endoAVF (see Figure 5).
• Consider a shallow needle angle for superficial veins. The needle angle depends on the endoAVF depth and the physical build of the patient.

Figure 5: Inflow and Outflow Needle Placement Options in EndoAVFs

Watch the BD WavelinQ™ EndoAVF System Cannulation Inservice Video below.