Commonality of Interventions in AV Accesses

Abstract

Although dialysis grafts and dialysis fistulas are fundamentally different in many ways, the interventions performed within them and the methods employed are the same. Indications for interventions and endpoints of interventions are also relatively similar. What constitutes success of the intervention performed? There are immediate anatomic, clinical, and hemodynamic endpoints for every case, while one can use anatomic and clinical endpoints only and reserve hemodynamic endpoints for equivocal cases. Hemodynamic endpoints can be determined by measuring intraprocedural blood flow using a Transonic catheter or flow measuring catheter. The clinical endpoint may be as simple as reestablishing a thrill within the access.

Appendix 1. AV Graft/AV Fistulae Thrombectomy

Pulse Spray

• The area containing the graft/fistula is prepared and draped to create a sterile field.

• For both straight and looped grafts, two puncture sites are required to access the entire circuit to remove all clot and the arterial plug. Puncture sites should be chosen to allow for access to both the ­arterial and venous portions of the graft (antegrade and retrograde access), but not so close to each other where a portion of the access is not accessible.

• Using a 25G needle, the skin at expected locations of puncture is infiltrated with 1% lidocaine.

• The graft is then punctured with either an 18/19G needle that can accommodate a 0.035 in. wire or a 21G needle from a micropuncture set at a 45–60° angle.

• The first puncture is preferably made in the arterial portion of the graft-directed antegrade towards the venous outflow.

• When performing the puncture, care should be taken to avoid puncturing the back wall of the graft. Ultrasound, if available, is a convenient tool to aid puncture.

• A wire is then advanced through the needle, and with fluoroscopy and/or palpation of the graft, intraluminal location is verified.

• If a 0.035 in. wire is used, a nonhydrophilic straight soft-tipped wire is preferred to push through the clot. For the micropuncture set, the wire provided is used and later upsized to a 0.035 in. wire.

• If access is primarily obtained towards the venous outflow, after placement of an appropriately sized sheath over a wire (6 Fr for routine PTA), a catheter is advanced beyond the clot and the venous outflow is assessed. Any venous outflow stenosis is treated with PTA. Some treat stenosis before pulse spray.

• Position pulse-spray catheter (s) in the graft. Most use two “crossing” catheters.

• Reconstitute agent. For tPA, 2 mg is reconstituted in 2 mL of sterile water for injection. Doses of 2–6 mg can be used. For urokinase, where available, 250,000–1,000,000 U can be used. A variety of 4–5 Fr pulse-spray catheters are available from Merit Medical, EV3, and Angiodynamics.

• The thrombolytic agent is then pulsed in through the catheter in 0.5–1 cc forceful injections. Use a 3-cc syringe or smaller to generate high pressure to force thrombolytic into the clot every 10–30 s.

• After pulse spray, if a second sheath has not been placed, this is now done within the venous limb of the graft directed towards the arterial plug. Care should be taken to avoid pushing the arterial plug into the feeding artery when placing this sheath (4–5 Fr).

• Depending on the length of untreated clot within the arterial limb, a pulse-spray catheter can be advanced to but not beyond the arterial plug and further thrombolytic can be delivered.

• Thrombolytic dwell time should be at least 15 min.

• The arterial plug is then removed by either suction aspiration or by using a Fogarty balloon catheter (4 Fr).

• If a Fogarty catheter is used, the catheter is passed into the feeding artery and the balloon should be inflated to the point of slightly molding along the arterial wall and in this inflated state, pulled across the arterial anastomosis.

• Gentle suction is placed on the sheath so that the arterial plug is aspirated upon withdrawal of the Fogarty catheter.

• Assess using physical examination of the graft. A thrill or pulse should be present (see endpoint determination).

• Treat residual clot in the graft with balloon maceration and/or external compression.

• After all possible clot is removed, the arterial inflow can be assessed by inflating a balloon within the outflow and refluxing contrast gently back across the arterial anastomosis to assess for stenosis and/or residual clot.

• Perform a final fistulogram from the arterial inflow to the right atrium and treat any remaining significant stenoses. Make sure to profile each anastomosis and ensure all significant stenoses have been dilated and no residual clot persists particularly at the arterial anastomosis.

Lyse and Wait

This methodology is often desirable as this technique allows for delivery of the thrombolytic agent prior to the patient arriving within the procedure room. In general, the thrombolytic is delivered 30–45 min before the procedure, and over that time interval, another procedure can be performed. By the time the patient enters the procedure room, most of the clot has dissolved thereby reducing the in-room procedure time. The methodology is very similar to the pulse spray methodology with the following exceptions:

• A small area of the access is prepared and draped in a sterile fashion within the holding or triage area.

• Access is obtained to the access with an angiocatheter or micropuncture set within the arterial limb of the graft or arterial anastomosis with the catheter directed towards the venous outflow. Intraaccess location should be verified either by attempting to aspirate clot, ­passing a wire into the access and withdrawing it and checking the wire for adherent clot, or visualizing the wire using ultrasound.

• The thrombolytic is then injected into the access with firm digital pressure applied at the arterial anastomosis to occlude it and prevent pushing clot into the artery. The venous outflow is also compressed to allow the thrombolytic to be forced throughout the clot within the access.

• When the patient is taken to the procedure room, the entire access is prepared and draped sterilely and a fistulogram is performed (very gentle injection of contrast so pressure is not introduced into the graft) through the catheter within the access.

• If outflow stenoses are found, the catheter is exchanged over a wire and exchanged for an appropriately sized sheath to accommodate the devices needed for treating the stenoses/occlusion.

• A second puncture is performed towards the arterial inflow and access is obtained to remove the arterial plug at the arterial anastomosis.

• Occasionally, the arterial plug can be removed or dislodged with external massage of the arterial anastomosis towards the outflow.

Mechanical Devices (Modify According to each Individual Device After Reviewing the IFU)

With use of mechanical devices, sterile preparation of the access is required and sheaths are placed into the access to allow access to all clot.

• Apply the mechanical thrombolytic device to the venous end of graft or fistula (some prefer this step before placing an “arterial” sheath; others find it easier to place both wires and cross them before passing the sheaths). In fistulas, external compression of aneurysms onto the thrombectomy device may aid in clearing thrombus from these areas.

• Place the “arterial” sheath.

• Apply mechanical device to arterial end of the access.

• If applicable, aspirate after each pass (PTD).

• Treat the arterial plug (Fogarty, occlusion balloon, device, adherent thrombectomy catheter).

• Assess and treat any significant peripheral venous outflow stenosis with PTA.

• After the clot is removed, the arterial inflow can be assessed by inflating a balloon within the outflow and refluxing contrast gently back across the arterial anastomosis to assess for stenosis and/or residual clot.

• Assess patency using physical exam of the access. A thrill or pulse should be present (see endpoint determination).

• Treat any residual clot with the device or balloon maceration as necessary.

• Perform a final fistulogram from arterial inflow to the right atrium.

Balloon-Assisted Thromboaspiration

• Place a 6 or 7 Fr removable hub “venous” sheath if available. Remove hub and aspirate clot if possible.

• Replace hub. If a hub removing sheath is not available, a sheath should be used where the side arm allows for aspiration. I prefer to use the Performer sheath (Cook Medical, Bloomington, IN) which has a large sidearm port.

• Place a 6 Fr “arterial sheath.”

• Pass a 5 Fr Fogarty catheter along arterial limb to near anastomosis. Inflate balloon and pull back toward sheath while aspirating on 6/7 Fr sheath with hub removed or aspirating via the sidearm. Another option is to place a 20-cc Luer lock syringe on the sheath sidearm and pull the plunger back to the point where it locks in the withdrawn position maintaining continuous suction.

• Repeat step 3, passing the balloon beyond arterial anastomosis.

• Assess the access for pulsatility to confirm inflow. If inflow is absent, repeat the balloon thrombectomy until pulsatility is restored.

• Pass the 5 Fr Fogarty catheter through venous sheath beyond central limit of remaining clot.

• Inflate the balloon and withdraw catheter while aspiring through the sidearm of sheath (s).

• Repeat steps as necessary.

• Assess residual clot burden; if large, use a mechanical device to complete the procedure or try external massage of the access to mobilize clot. If not, assess and treat venous outflow stenosis with PTA.

• Assess graft/fistula with physical exam. A thrill should be restored after successful PTA (see endpoint determination above).

• Treat any residual clot with Fogarty balloon, with all attempts to aspirate all clot. Perform final fistulogram from arterial inflow to right atrium and treat any significant stenoses.

Manual Catheter-Directed Thromboaspiration

• After insertion of a 7 or 8 Fr sheath into the dialysis access preferably near the arterial anastomosis directed towards the outflow, aspirate clots using a 7 or 8 Fr slightly angled (vertebral or multipurpose type) aspiration catheter. Perform as many passes as necessary until no additional clots are aspirated. Use a 20–50-cc Luer lock syringe.

• Leave a guide wire through the venous-directed sheath and place 7 or 8 Fr arterial-directed sheath into the access.

• Push, very gently, a slightly angled 5 Fr catheter over a hydrophilic guide wire into the artery and check the exact level of the arterial anastomosis.

• Aspirate clots starting from the sheath. If the catheter is clogged, flush it into gauze and reintroduce it further toward the anastomosis.

• Inject gently 2–5 mL of contrast medium through the arterial sheath during compression of the graft/fistula and look for residual clots.

• Push the angled aspiration catheter to contact any residual clots and aspirate with quick back and forth movements to detach the thrombi. Stop only when no residual clot is visible.

• When no residual clot is visible, dilate any underlying stenoses.

• To dilate before aspiration of all the thrombi increases the risk of pulmonary embolism.

• After clot is removed, the arterial inflow can be assessed by inflating a balloon within the outflow and refluxing contrast gently back across the arterial anastomosis to assess for stenosis and/or residual clot.

• Perform a final angiogram from arterial inflow to right atrium [27, 54, 55].