Section 3: Surgical Technique – Tips and Tricks for the Wrist AVF
Pre-operative planning is important in dialysis access. A hand drawn picture outlining surgical anatomy with specific details is recommended as part of the mapping protocol and to improve safety. Re-marking is recommended again on the day of surgery, ideally with ultrasound guidance and reenforced after prepping as the marking fades from sterile prepping of the arm. The dotted line represents the skin incision, that may vary depending on the cephalic vein location and branching (Figure 22).
Figure 17
Skin incision is marked preoperatively at the time of surgery planning. The dotted line is the planned skin incision. It is the authors strong opinion that preoperative planning and physical exam including ultrasound seldom requires intraoperative changes in the planned procedure.
Following skin incision the tissues are divided to expose the vessels. This should be done with minimum dissection and tissue trauma (Figure 18). The vein should be assessed and mobilised prior to arterial dissection. Once the vein is slooped the artery is mobilised. The artery lies beneath a fascial layer and often the superficial local anesthesia does not reach beneath this and further anaesthetic infiltration is required. The paired concommitans veins travel alongside the lateral aspects of the artery and a useful technique is to approach the artery directly in the midline to avoid bleeding from these veins which can be bothersome (Figure 18) and (Figure 19).
Figure 18
Subcutaneous tissue is dissected using a mosquito hemostat and sharp knife techniques or fine scissors (i.e. small Metzenbaum or the so called Littler scissors). Minimal tissue trauma occurs this way.
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Figure 19
The radial artery is exposed from the top, where there are no branches. Optimal exposure is obtained using Vessel loops and small retractors (i.e. the Senn or eyelid static retractors.)
Figure 20
This transerse image depicts the radial artery being mobilized by gently pushing the peri-adventitial tissue and the concomitant veins sideways exposing the small usually paired arterial side branches (Note: the paired veins and arteries produce the mickey mouse sign on transverse view ultrasound).
When the artery is looped and a length dissected suitable for clamping and arteriotomy, the vein can be divided and prepared for anastomosis. Small arterial side branches may need dividing and securing with a suture or tie (Figure 25).
In preparing the vein the use of two branches being made into a cuff or patch is ideal. (Figure 21). Corner stitches can be used early to control the vein and minimize handling. Keeping the vein attached to its distal connection, for example the dorsal branch, keeps the vein in place and prevents inadvertent rotation (Figure 20).
Figure 21
The often-paired side branches are ligated (5-0 Vicryl) 1-2 mm away from the radial artery to prevent waist formation when the artery in spasm later dilates.
Figure 22
There are a few ‘tricks’ helpful in preparing the vein for an AVF depicted in this image. First, by placing the corner stitches the vein is stabilized and easier to ‘control’. Second, by not completely dividing the vein from its distal connection, in this case the dorsal branch further keeps the vein in place. Third the distal branch Is intentionally left slightly longer to avoid kinking when it is turned toward the artery.
Figure 23
Preparing the vein patch includes placing corner stitches, opening the patch by cutting the vein from each open lumen and trimming excess vein tissue. By leaving the vein connected to one of the distal vein branches, it helps stabilize the vein during these steps and prevents inadvertent twisting. In preparing the vein patch, the distal (dorsal branch) is left slightly longer, the shorter cephalic branch prevents an angling of the vein at the anastomosis site that otherwise would occur as the cephalic vein is turned toward the radial artery.
Figure 24
This image depicts the prepared vein patch in relation to the radial artery. Heifetz vascular clips are now placed on the radial artery above and below the intended ateriotomy site. A soft clamp may be needed on the cephalic vein to prevent back bleeding. Note the slightly shorter vein patch directed upwards. The shoulder direction is to the right in this image, the hand to the left.
The an longitudinal arteriotomy is made using a microknife or #11 blade and the artery flushed with heparin saline (Figure 24).
Figure 25
A small arteriotomy is made with a #11 blade (upper panel) to allow an #18 – 22 Fr angiocatheter flushing the artery while the vascular clips are sequentially opened (middle panel). Alternatively a smooth ‘christmas-tree’ is used. With either technique the artery in spasm is gently dilated under hydro-pressure using a smooth angled “christmas tree” shown in (Figure 9) and also in video clips later in this chapter. The arteriotomy, about 45 degrees on the radial side or lateral is approximatley extended to match the venous path, usually 8-10 mm (bottom panel).
Sutures for the anastamosis are non absorbable monofilament. Polypropylene (prolene) 6-0/7-0 on a BV-1 needle and PTFE CV6 on TTc9 or TTc12 needles are the standard used sutures (Figure 25).
Figure 26
A polypropylene (prolene) (lower panel) 7-0 on a BV-1 needle (lower panel) and PTFE CV6 on TTc9 or TTc12 needles (top panel) are commonly used suture in vascular access surgery. The PTFE suture has the same diameter as the threads resulting in minimal or no post-anastomosis bleeding. The PTFE sutures leaves no space in the vessel wall (right panel in this image).
Standard technique is to use double-needled 6-0 or 7-0 polypropylene or a PTFE suture CV6 on a TTc9 or TTC12 needle corner sutures are placed inside out to at the proximal arterial and vein patch corners.
As Figure 25 shows the assistant (or the surgeon with his/her other hand) dilates the artery if required using a small pair of forceps to enable exact suture placement. The corner bites should be small (or about 1 mm). The suture is tied in 7 square knots. Correctly placed, both threads and the tied knot are on the outside the vessels. The distal corner stitch may also be placed at this time but not tied as this facilitates the back-wall suturing.
The back wall is sutured in a continuous suture and the “toe” is tied down. The front wall is then completed with the remaining sutures (Figures 27 to 30). This standard may need different approaches based on anatomy (Figure 31).
Figure 27
Using the double-armed 6-0 or 7-0 polypropylene or the ePTFE CV6 TTc9 or TTc12 sutures, corner sutures are place inside out to at the proximal arterial and vein patch corners. As this image shows, the assistant dilates the artery if required using a small pair of forceps to enable exact suture placement. The corner bites should be small or about 1 mm). The suture is tied in 7 square knots. Correctly placed, the knots of corner stitches are on the outside the vessels. The distal corner stitch may also be placed at this time but not tied as this facilitates the back-wall suturing.
Figure 28
Suturing techniques vary. Here the back wall is sutured first. The very first stitch is placed from outside in on the vessel closest to the surgeon, in this case into the artery (top panel). The purpose of this first stitch is just to get inside the vessel with the needle passing close to the corner knot. Alternatively, the stitch is passed between the vessels and then outside-into the artery (middle panel). Next the (right-handed) surgeon will perform a forehand running suture of the back wall. The very first running stitch goes inside vein to the artery in one single bite (bottom panel). This technique is accomplished by exposing the back wall corner using the distal corner suture traction, pulling the artery and vein slightly apart with small micro-forceps grabbing only the adventitial tissues.
Figure 29
The back wall is completed in a running fore-hand suturing fashion. Small exact placed sutures will maximize lumen as the fistula will need a volume flow of about 800 ml/min when matured.
Figure 30
The last back wall running suture goes inside out on the vessel closest to the assistant in this example the distal vein patch. (Note that the eye-forceps are used to “open” -expose the anastomosis facilitating suturing, by only grabbing peri vessel adventitial tissue.
Figure 31
This image Is crucial to understand corner tying principels.The previously placed corner stitch (A and B) is now tied seven square knots. One of these (in this case thread B) is then tied to the just finished back wall running thread C, also seven square knots. Suture A is next use to run the front wall. (If the assistant is doing this in a forehand fashion, the thread A goes outside in on the vessel closest to the surgeon, in this case the radial artery. The proximal corner stitch can be run to meet the distal suture and tied mid-way. Variations of this can be used when and if the operator is confident. It is always safter to always tie 6 square knots.
Figure 32
The front wall anastomosis may be completed with both corner stitches meeting and tied midway. Again, as mentioned above, the proximal vein patch is slightly shorter to avoid the cephalic vein kinking as the vein curves the first 2-3 cm from the anastomosis. (panel b). During suturing, vesseloops are used to stabilize the vessels in desired positons.
Figure 33
In cases of no available dorsal branch the cephalic vein is anastomoses end to side usually with added spatulation. The cephalic vein is clamped at the appropriate level. Approximately 2/3 of the vein facing the artery is cut with an # 11 blade (panel a, the vein is dilated with fine forceps and spatulated for 5-6 mm (panel c) and the proximal (panel c) and distal (panel d) corner stitches placed. Excessive vein corners may be trimmed to optimize suturing. The suture techique is then similar to that described above for the pach anastomosis described in figures 31-32.
Endovascular technique for creating arteriovenous fistulae.
Recent endovascular innovations have developed two minimally invasive techniques to create AVF fistula using one or two catheter techniques respectively. Both techniques use preoperative vascular mapping of the antecubital vessels to determine suitability for respective techniques (1-5). For details on endovascular AVFs the reader is referred to a later dedicated to Minimal Invasive Dialysis Access (MIDA) chapter for both hemo- and peritoneal dialysis access.
Figure 34
The artists drawing of the antecubital fossa vascular anatomy. This is used as a roadmap for percutaneous endovascular AVF placement. Not everyone would be eligible for an endovascular AVF. Both techniques rely on the ability to approximate an artery and a vein for the devices to create an anastomosis, and the prescence of a perforating vein.
(BV PFA = Basilic Vein Peripheral Forearm; MV PFA=Median Ven Peripheral Forearm; CV PVA= cephalic Vein Peripheral Forearm).
The antecubital superficial veins are best understood by having an archetypal roadmap of single veins made up of five essential veins: the perforating vein, medial cubital vein (MCV), the cephalic vein, the median basilic vein (MBV), basilic vein (Figure 34).
The anastomosis is created with radiofrequency power, and electrocautery across vessels aligned by opposing magnets to create the AVF anastomosis for the single and dual catheter technique respectively. Both devices have CE mark status in Europe and FDA approvals in the United States (3,4).
Preliminary results report near 100 % technical success and a fistula maturation rate approaching 90%, better than usual is reported for surgically created AVFs (4,6). The real-world performance of these devices will take another few years. The one wire device is already being withdrawn for financial reasons. Others are under development.
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