Interventions for Failing Hemodialysis Access

Published on 21/06/2015 by admin

Last modified 22/04/2025

Print this page

This article have been viewed 2121 times

21 Interventions for Failing Hemodialysis Access

During the past decade, the management of failing hemodialysis accesses has shifted from surgical repair to catheter-based approaches. The advantages of endovascular approaches over surgery include the avoidance of temporary hemodialysis catheters, the preservation of venous segments for future access creation, and the prolongation of total survival time on hemodialysis. This chapter reviews the mechanisms of dialysis access failure and describes the interventional management of failing and thrombosed fistulas and grafts.

Timing of Procedure

An emergency fistulogram should be performed for refractory access-site bleeding after hemodialysis. Emergency angiography and intervention are also indicated for failing or thrombosed hemodialysis accesses in patients with hyperkalemia, volume overload, or refractory hypertension.

Urgent catheter-based treatment is indicated for patients with thrombosed hemodialysis accesses. Delays in treatment more than 24 hours after diagnosis or more than 48 hours after hemodialysis may require temporary catheter placement or increase the risks of complications. Urgent angiography should also be performed for malfunctioning but nonthrombosed dialysis accesses because thrombosis may be imminent.

Contraindications to percutaneous treatment include graft infection, a central right-to-left shunt, or pulmonary hypertension. A relative contraindication to catheter-based therapy is thrombosis of new fistula or graft within 30 days of surgical creation or revision. In this situation, thrombosis has likely arisen from a technical problem or anatomy not amenable to catheter-based therapy.

Hemodialysis Access Anatomy

An autogenous arteriovenous access is surgically created by directly anastomosing a native outflow vein (Fig. 21-1) to a native inflow artery (Fig. 21-2), usually in the form of an end-to-side anastomosis. A prosthetic arteriovenous access is constructed by surgically interposing a segment of polytetrafluoroethylene (PTFE) between a native artery and a native vein in either a straight or looped configuration. Common patterns include the brachial-cephalic configuration in the forearm or the brachial-basilic configuration in the upper arm (Fig. 21-3). For the purposes of this chapter, an autogenous arteriovenous access will be referred to as a fistula, a prosthetic arteriovenous access as a graft, and when mentioned together, both types will be referred to as accesses.

Figure 21-1 Venous anatomy of the upper extremity. Rt, right; SVC, superior vena cava; v, vein.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)

Figure 21-2 Pertinent arterial anatomy of the upper extremity. a, artery; Rt., right.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)

Figure 21-3 Access anatomy of the upper extremity. A radial-cephalic fistula is created by an end-to-side anastomosis between the cephalic vein and the radial artery, with ligation of the distal stump of the cephalic vein. A brachial-cephalic graft in the forearm (lower arm arrows) requires the surgical interposition of a polytetrafluoroethylene (PTFE) loop using end-to-side connections. A brachial-basilic graft in the upper arm (upper arm arrows) requires the surgical insertion of a PTFE loop using end-to-side connections.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)

The selection of a particular permanent hemodialysis access creation is based on the principle of “Fistula First,” which is derived from evidence favoring the creation of an autogenous fistula whenever possible before resorting to a PTFE graft. The selection of a specific location is based on the recommended sequence of using the nondominant arm before the dominant arm, the forearm before the upper arm, and the upper extremity before the lower extremity.

Mechanisms of Hemodialysis Access Failure

Although the primary patency of fistulas is low, autogenous fistulas have better long-term patency than prosthetic grafts. After surgical creation, <50% of fistulas mature adequately to support hemodialysis. When fistulas mature adequately, they remain patent for a median of 3 to 7 years. The primary patency of PTFE grafts exceeds 80%, but prosthetic accesses remain patent for only 12 to 18 months.

Two failure modes of fistulas and grafts are amenable to interventional treatment (Fig. 21-4). An inflow stenosis in newly placed fistulas may inhibit physiologic hypertrophy and maturation. An outflow stenosis in chronically used fistulas and grafts may cause high pressures and thrombosis. Although 50% of malfunctioning accesses ultimately undergo thrombosis, this is not the primary cause of failure. Instead, shear stress and fibromuscular hyperplasia of the outflow vein causes a progressively worsening stenosis, which then leads to stasis and eventual thrombosis (see Fig. 21-4).

Figure 21-4 Pathogenesis of dialysis access failure. The early appearance of an inflow (anastomotic) stenosis may lead to failure of fistula maturation. The late development of a stenosis in the outflow segment of a fistula or graft is the cause of stasis and access thrombosis.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)

Stenoses can occur anywhere in a dialysis access, but the most common location is the anastomosis between the prosthetic graft and the outflow vein. Although fistulas contain no outflow anastomosis, they are also susceptible to stenosis formation in the outflow vein.

Hemodialysis Access Monitoring, Surveillance, and Testing

Monitoring refers to regular physical examination and the assessment of dialysis adequacy. A well-functioning fistula or graft should have a prominent thrill, loud medium-pitched bruit, and minimal pulsation. A soft bruit suggests the presence of an inflow stenosis, whereas a prominent pulsation, short but high-pitched bruit, or aneurysmal dilatation suggests the presence of an outflow stenosis. Marked arm edema suggests the presence of dual venous obstruction (cephalic and basilic) or a subclavian vein stenosis or occlusion.

Surveillance entails the use of noninvasive testing. The finding of rising pressures of >150 mm Hg at a constant flow of 200 mL/min on dialysis suggests the presence of an outflow stenosis. Estimating the recirculation fraction using urea concentrations or clinical parameters such as body weight, volume status, or serum potassium concentration suggests that a malfunctioning access is causing incomplete hemodialysis. The uncertain benefits of preemptive graft intervention have tempered enthusiasm for routine noninvasive surveillance using Doppler ultrasound.

At the time of angiography and intervention, hemodynamic measurements may help to assess procedural success. An inflow stenosis may reduce access pressures to <15 mm Hg and prevent adequate filling. An outflow stenosis may increase access pressures to arterial levels. The ideal systolic pressure of an access should be <50 mm Hg, and the optimal ratio of systolic pressure in the access to systolic systemic pressure should be 0.30 to 0.40.

A significant stenosis is defined by the presence of at least a 50% diameter stenosis. A successful endovascular intervention is defined by the ability to complete at least one dialysis session.

Procedures

The term fistulogram refers to the angiographic study of either an autogenous arteriovenous fistula or a prosthetic arteriovenous graft. Before an angiographic procedure is performed, aspirin 325 mg may be given orally. Clopidogrel can be substituted in aspirin-allergic patients. During the treatment of thrombosed accesses, heparin is usually given intravenously in a dose of 5000 units. Lower doses of heparin can be used or heparin can be omitted if the risk of bleeding or perforation is increased. Antibiotic prophylaxis with cephalothin 1 g intravenously is commonly recommended. If an allergy to cephalosporins exists, vancomycin 1 g intravenously can be substituted and given over 1 hour. Warfarin is recommended for secondary prevention of access thrombosis if no stenosis is found.

Thrombosed Accesses

A four-step procedure is recommended.

1. Thrombectomy

Two 6F sheaths are placed within the access: one in the direction of the venous outflow and one in the direction of the arterial inflow (Fig. 21-5). Sheath insertion is carried out by inserting 18-gauge needles into the occluded fistula or graft near the usual entry sites, which are identified by needle tracks and induration. As the thrombosed access is entered, a “pop” may be felt as the needle penetrates the dura. Although no flashback is seen and no blood can be aspirated from a thrombosed access, intravascular entry is confirmed by smooth guidewire advancement under fluoroscopy. It is important to avoid puncturing the back wall of the graft, because an extrinsic hematoma may cause extrinsic compression. It is important to avoid injecting contrast into a thrombosed access, because thrombus may dislodge and embolize. An alternative approach is to begin with a 4F micropuncture set (Cook, Bloomington, IN).

Figure 21-5 Cross-sheath method. A 6F sheath is inserted into the access near the arterial inflow anastomosis and directed into the direction of the outflow, and a 6F sheath is inserted into the access near the venous outflow in the direction of the inflow. Guidewires are advanced in the direction of the inflow and outflow under fluoroscopic guidance. No contrast is injected into a thrombosed access. a, artery; v, vein.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)

Although the method is called the “cross-sheath” technique, the tips of the sheaths face each other but do not actually overlap (Fig. 21-5). Two 150-cm 0.018-inch V-18 hydrophilic control wires (Boston Scientific Medi-Tech, Miami, FL) are advanced through the sheaths under fluoroscopic guidance without contrast injections, one in the outflow direction and one in the inflow direction. If it is difficult to identify or advance the wire beyond the outflow stenosis or to enter the inflow artery, a 65-cm 5F multipurpose A1 catheter (Cordis, Miami Lakes, FL) can be inserted for additional maneuverability. The resistant stenosis can usually be penetrated with a 0.035-inch hydrophilic curved wire and replaced with a 0.018-inch guidewire for thrombectomy.

Several thrombectomy devices are available, including the AngioJet AVX rheolytic thrombectomy catheter (Possis Medical, Minneapolis, MN), pulse-spray infusion catheters (Cook, Bloomington, IN), pulse-spray side-slit catheters (AngioDynamics, Glens Falls, NY), the Amplatz Thrombectomy Device (Microvena, White Bear Lake, MN), the Arrow-Trerotola Percutaneous Thrombectomy Device (Arrow International, Reading, PA), and the Gelbfish Endo-Vac device (Neovascular Technologies, New York, NY).

Thrombectomy is carried out first in the outflow direction (Fig. 21-6) and then in the inflow direction (Fig. 21-7). When the blunt edge of the opposing sheath blocks advancement of the rheolytic thrombectomy catheter, transient insertion of the sheath dilator in the opposing sheath may present a smoother transition for passage of the thrombectomy catheter.

Figure 21-6 Rheolytic thrombectomy of venous outflow. a, artery; v, vein.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)

Figure 21-7 Rheolytic thrombectomy of arterial inflow. a, artery; v, vein.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)

After successful thrombectomy restores flow, the access sheaths are flushed with heparinized saline, and angiography can be safely performed to delineate the outflow stenosis.

2. Angioplasty

Venous angioplasty of the culprit outflow stenosis entails the use of 4- to 10-mm balloons (Fig. 21-8). The venous stenoses tend to be fibrotic, may be resistant to dilatation, and occasionally require pressures >20 atm. High-pressure, noncompliant balloons with rated burst pressures of 20 to 24 atm can be used (Conquest or Dorado, Bard Peripheral Vascular, Tempe, AZ). Cutting balloons can be used when high-pressure balloons are unsuccessful (Boston Scientific), but the use of peripheral cutting balloons in one study was associated with an increased risk of rupture. Stents are usually reserved for severe recoil, venous perforations, or stenoses in surgically inaccessible veins, but the use of stent grafts will likely increase in an effort to reduce restenosis.

Figure 21-8 Balloon dilatation of outflow stenosis. The outflow stenosis is commonly found at or near the venous outflow anastomosis but can be encountered anywhere in the peripheral vein. a, artery; v, vein.

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3: 1–11, with permission from Elsevier.)

3. Fogarty Thrombectomy

Fogarty thrombectomy using an over-the-wire 4F Thru-Lumen Embolectomy Catheter (Edwards Lifesciences, Irvine, CA) is recommended in almost all cases to extract resistant thrombus at the arterial inflow (Fig. 21-9). The catheter must be withdrawn forcefully to dislodge the resistant thrombus. Persistent thrombosis is most successfully treated with repeat Fogarty thrombectomy of the inflow. If this fails and the access continues to have low pressure, balloon angioplasty of the arterial inflow anastomosis with a 6-mm dilatation catheter can be tried. An approach of last resort is to perform balloon angioplasty along the entire length of the access.

Figure 21-9 Fogarty embolectomy. The balloon catheter is inflated (A), pulled back to the thrombus (B), and forcefully withdrawn to mechanically dislodge the resistant inflow stenosis (C).

(Reprinted from Bittl JA. Catheter interventions for hemodialysis fistulas and grafts. JACC Cardiovasc Interv 2010;3:1–11, with permission from Elsevier.)