Arteriovenous graft creation for hemodialysis and its complications

INTRODUCTION — An arteriovenous (AV) graft is a deliberate connection between an artery and vein that is created by interposing graft material between them. A decision to choose an AV graft over another type of hemodialysis access is individualized based upon anatomy and life expectancy, among other factors. (See "Approach to the adult patient needing vascular access for chronic hemodialysis".)

Definitions for the hemodialysis access time points used in this topic (eg, primary patency, assisted primary patency, postintervention patency) are provided in the figure (figure 1 and table 1).

The creation of AV grafts for hemodialysis and their complications are reviewed here. An overview of the different types of chronic hemodialysis access and creation of AV fistulas for hemodialysis are presented separately. (See "Arteriovenous fistula creation for hemodialysis and its complications" and "Approach to the adult patient needing vascular access for chronic hemodialysis".)

GENERAL CHARACTERISTICS — AV grafts are constructed by interposing a graft between an artery and vein. The graft material is typically either manufactured from a synthetic material, like polytetrafluoroethylene or polyester (eg, Dacron), or can be taken from a decellularized biologic source, like bovine carotid artery or cadaveric human tissues. The main benefit of AV grafts is that they can be used for hemodialysis in as little as 24 hours after creation depending upon the type of graft that is used [1,2]. Prosthetic grafts are widely commercially available, have a long shelf life, and generally do not require special handling.

For patients who require a chronic hemodialysis vascular access, an AV graft may be an appropriate choice as initial hemodialysis access, or as a secondary access if an AV fistula has failed to develop. As a primary access, an AV graft may be selected for a variety of reasons, including patient preference, limited life expectancy or medical comorbidities, or following a determination that the patient is not a good candidate for an AV fistula (ie, high risk for AV fistula failure). (See "Risk factors for hemodialysis arteriovenous fistula failure".)

AV grafts can be created with minimal patient morbidity. The surgical procedure is relatively straightforward and generally can be quickly accomplished under local anesthesia with or without sedation, though use of general anesthesia may be more comfortable for many patients. Prosthetic grafts are also easily palpable when placed subcutaneously and are easily punctured for hemodialysis.

On the other hand, AV grafts generally possess other less desirable characteristics.

●In general, AV grafts have shorter patency compared with AV fistulas. This is particularly true in younger dialysis populations. However, a patency discrepancy has not been consistently found. Data from the Dialysis Morbidity and Mortality Study (DMMS) found no patency advantage for AV fistulas compared with AV grafts in older adults (>65 years) [3]. Also, a study from the United States Renal Data System (USRDS) linked with Medicare claims showed that in incident hemodialysis patients aged ≥67 years, there was no significant mortality difference between patients who had an AV graft placed as first access compared with those who had an AV fistula [4].

●The AV graft is a high-flow, low-resistance system that can result in a steal phenomenon in the distal extremity, also termed dialysis access-associated steal syndrome, and other complications related to the increased flow into the venous system (eg, heart failure, pulmonary hypertension). The onset of these problems after AV grafts is more common in the acute postoperative period since the AV graft serves as a large-diameter circuit as soon as it is opened [5]. (See 'Cardiopulmonary problems' below and "Evaluation and management of heart failure caused by hemodialysis arteriovenous access" and "Pulmonary hypertension in patients with end-stage kidney disease".)

●Due to the nonautogenous nature of AV grafts, AV grafts have higher risk for infection, with up to four times the incidence of infection compared with AV fistulas [6]. (See 'Graft infection' below.)

Requirements for AV graft use — The requirements for an AV graft are similar to those of an AV fistula, except that an AV graft does not require maturation (see 'Timing of AV graft creation' below). These include the following, which are discussed in more detail elsewhere:

●The AV graft must be accessible with the patient in a sitting position.

●In the forearm, the AV graft should be on the volar surface.

●In the upper arm, the AV graft should be on the anterior or lateral surface.

●The AV graft must be able to be reliably cannulated repeatedly.

●The AV graft should be within 6 mm of the skin surface.

●A relatively straight segment needs to be available for cannulation.

●Blood flow must be adequate to support the dialysis prescription.

For AV grafts, needles need to be placed 3 cm apart and access sites need to be able to be rotated. Ideally, there should be a 6- to 8-cm straight segment of AV graft for this purpose. Adequate blood flow for an AV graft generally means a minimum flow rate in the range of 600 to 700 mL/minute. The actual flow in an AV graft can vary widely based upon where it is placed. Grafts with radial or ulnar inflow have lower flow rates than grafts with brachial or axillary inflow. Tapered grafts limit the inflow, and for this reason they are usually used with brachial or axillary inflow and not in radial or ulnar inflow.

EVALUATION AND PLANNING

Physical evaluation — An adequate evaluation of the predialysis patient with chronic kidney disease enhances the opportunity to place a functioning arteriovenous (AV) access. The anatomic requirements for hemodialysis AV access and the evaluation of the patient for placement of hemodialysis arteriovenous access are discussed in detail separately. (See "Patient evaluation prior to placement of hemodialysis arteriovenous access".)

Timing of AV graft creation — In contrast to AV fistulas, AV grafts do not require maturation time, and, depending on the type of conduit used, AV grafts can be accessed in as little as 24 hours for dialysis. Because AV grafts also have shorter patency and increased risk of infection, there is a marked disadvantage to creating an AV graft that is not going to be used. As such, AV grafts should be created when the patient is expected to be starting hemodialysis within a short period of time (ie, two to four weeks). This will allow for tissue ingrowth and resolution of surgical inflammation/edema if a traditional expanded polytetrafluoroethylene (ePTFE) graft is used.

Anatomic location and configuration — AV graft nomenclature should refer to anatomical designations that describe their inflow artery, outflow vein, graft material, and graft configuration. A suitably sized artery can be used as the inflow for an AV graft, and likewise a suitably sized vein can be used as the outflow, typically 4 mm or larger [7]. Common graft locations are looped forearm (brachial artery to cephalic vein), straight forearm (radial artery to cephalic vein), looped upper arm (axillary artery to axillary vein), and straight upper arm (brachial artery to axillary vein). Lower extremity grafts, looped chest grafts, axillary-axillary (necklace) grafts [8], and axillary-atrial grafts have also been constructed but are uncommon [9,10].

Forearm — The most common configuration for AV grafts in the forearm is the loop configuration with arterial inflow from the antecubital brachial artery and outflow through the median cubital vein, cephalic vein, brachial vein, or basilic vein. The radial or ulnar artery can also be used as inflow to any of the aforementioned outflow veins. The graft can be configured straight when using the distal radial or ulnar artery as inflow, and the graft can be configured in a loop when using the proximal radial or ulnar artery as inflow. There are little data to support the use of one configuration over the other.

Upper arm — The most common configuration for AV grafts in the upper arm is straight, using inflow from the antecubital brachial artery to axillary vein outflow. The graft can also be configured as a loop using the proximal brachial artery as inflow. The cephalic, basilic, and brachial veins can be used as outflow as well. Again, there are little data to support the use of one configuration over the other.

Chest — The most common configuration for chest AV grafts is an axillary artery to contralateral axillary vein or "necklace" graft. Chest AV grafts can also be constructed as a loop from the axillary artery to the ipsilateral axillary vein. Published studies describing outcomes of chest wall grafts have small sample sizes, but, in the available data, the patencies of loop grafts and necklace grafts appear to be comparable [8,11,12]. Some authors have reported that in their experience with the loop configuration, they received a number of complaints from dialysis nurses regarding difficulty in accessing the graft [12]. The same authors also use the axillary loop as a rescue procedure for an occluded necklace graft. Others have stated that they have received no complaints about accessing the loop configuration [8].

Lower extremity — In the lower extremity, AV grafts are most commonly constructed in a loop configuration either in the upper thigh or the mid-thigh. In the upper thigh, the common femoral or superficial femoral artery is used for inflow, and the femoral vein or saphenous vein is used for outflow [13]. In the mid-thigh, the superficial femoral artery supplies the inflow, and the femoral vein is used for outflow. A systematic review of lower extremity access found that the primary and secondary patency rates (figure 1 and table 1) of upper-thigh and mid-thigh grafts were comparable at one year [14].

Atypical locations and other options — When all of the typical anatomic access sites have been exhausted, cases of AV grafts being created in atypical anatomic configurations have been reported. Some examples include the axillary artery to right atrium in a patient with central venous occlusion, the axillary artery to common iliac vein in a patient with occluded thoracic central veins and inadequate femoral veins, and the brachial artery to jugular vein in patients with exhausted upper-arm superficial veins [15-17].

The pipeline technique is a percutaneous method that can be used to create an arteriovenous graft de novo or to extend or bypass an existing AV graft or fistula [18,19].

Order of AV graft preference — The preferred AV graft site types are the antecubital forearm loop graft and the upper-arm curved graft. Preservation of more proximal sites for new access creation are encouraged. Chest wall grafts or lower extremity grafts can be considered when all upper extremity sites are exhausted.

Similar to AV fistulas, in planning the creation of an AV graft, attention should be directed to the nondominant arm first. While the patient is on dialysis, having the dominant hand free allows the patient to engage in desired activities more easily.

Once upper extremity sites are exhausted, the decision regarding which type of access to create next can be challenging. While it is widely accepted that the incidence of infection of thigh grafts is higher compared with upper extremity grafts, up to 35 percent in some series [20], relative to the option of a tunneled catheter, infection rates with a thigh graft are lower [20]. Another option for patients with end-stage vascular access is the chest wall graft. Chest wall grafts have lower infection rates compared with thigh grafts or tunneled catheters [8].

For patients with no upper extremity options due to thoracic central venous stenosis/occlusion, whether to choose a Hemodialysis Reliable Outflow (HeRO) or thigh graft first is unclear (see 'HeRO grafts' below). There are data both in support and against HeRO over a thigh graft [21,22]. Furthermore, it is unclear if the rate of infection between the two differs [21,22]. It does seem clear that the HeRO graft extends the use of the upper extremity and preserves the thigh for future use. It has been suggested that the HeRO be considered first in younger, healthier patients with longer life expectancies and that the thigh graft be considered first in older patients with shorter life expectancies [21]. A decision analysis comparing HeRO, tunneled catheter, or thigh graft, which took into account infection, thrombosis, and ischemic events, found that HeRO was the least costly method of vascular access option in this circumstance [23].

TYPES OF AV GRAFTS — Numerous prosthetic and biologic graft materials are available for arteriovenous (AV) graft creation. AV grafts are typically made of expanded polytetrafluoroethylene (ePTFE) with a diameter of typically 6 mm (range: 4 to 8 mm). AV grafts can also be constructed from biologic materials [24-27]. The AV graft can be straight or looped. Prosthetic graft designs include those that are tapered (7 or 8 mm on the venous end and 4 mm on the arterial side [28]), thinner-walled [29], or reinforced with rings for added support [30]. Data demonstrating clear superiority in performance of one graft material over another do not exist. In choosing graft material, consideration should be made for the timing in which the graft will need to be accessed for dialysis, the presence of/risk for infection, the experience of the surgeon, and cost.

The upper extremity is the most common location for an AV graft; however, an AV graft can be created between virtually any arterial inflow and venous outflow. The most common graft material used for AV grafts is polytetrafluoroethylene (PTFE); however, numerous prosthetic, xenograft, and homograft materials have also been used.

Prosthetic grafts — The most commonly used prosthetic material for AV grafts is ePTFE. Most surgeons have abandoned Dacron as a graft material for AV grafts due to poor patency, issues with bleeding, and poor wall integrity. ePTFE grafts have undergone various modifications to improve their performance. Unfortunately, the outcomes for ePTFE AV grafts remain disappointing. A meta-analysis demonstrated a primary patency (figure 1 and table 1) at two years for AV grafts of 40 percent and a secondary patency of 60 percent [31].

Standard versus thin-walled — ePTFE grafts are available in a standard thickness (0.64 mm) and a thin-wall version (0.37 mm). The thin-wall configuration is more flexible and hence somewhat easier to handle. The data to support one configuration being superior to another are minimal. One study (performed early when the thin-wall configuration was first introduced) randomly assigned 108 patients to standard-wall or thin-wall AV grafts. The standard thickness group demonstrated significantly longer mean primary patency (18.2 versus 12.1 months), secondary patency (20.9 versus 13.7 months), and cumulative patency (22.2 versus 15.2 months) (figure 1 and table 1) [29].

Heparin-bonded grafts — Luminal surface heparin-bonded ePTFE was introduced in 2006. A 2016 review of heparin-bonded ePTFE for hemodialysis access identified five studies evaluating heparin-bonded grafts [32]. The first two retrospective studies that were performed demonstrated significantly higher patency in the heparin-bonded group compared with the conventional group [33,34]. Subsequently, two additional retrospective studies found no significant difference in patency between the two groups [35,36]. One trial involving 160 patients showed a nonsignificant trend toward improved patency for heparin-bonded grafts, which had a significantly lower early thrombosis rate that was sustained only for the first five months [37].

Although the benefits of using heparin-bonded grafts are not well supported, the risk of using a heparin-bonded graft is overall low. The risk of heparin-induced thrombocytopenia (HIT) is less than 0.1 percent in over 130,000 implanted grafts [38]. Among those with HIT, there are reports of platelet counts returning to normal with and without explantation [38,39].

Externally supported grafts — ePTFE grafts are available in an externally supported version that has plastic rings encircling the outer surface of the graft. External support is thought to provide resistance to kinking and incompressibility. While externally supported grafts are not commonly used for AV grafts in the United States (US), largely due to concerns surrounding puncturing the graft and posthemodialysis hemostasis, there are reports of externally supported grafts having good success with no difficulty in puncture or hemostasis in other geographic regions [40].

A large retrospective study performed at a non-US institution found significantly higher one-, two-, and three-year patency for externally supported AV grafts compared with nonsupported AV grafts (49.4 versus 31.9 percent, 31.6 versus 17.4 percent, and 20.2 versus 10.8 percent, respectively) [41].

Early cannulation grafts — Standard ePTFE grafts typically require two to three weeks of tissue ingrowth prior to puncture to reduce the incidence of puncture site bleeding and hematoma. However, a number of early cannulation grafts have become commercially available that allow for graft puncture in as early as 24 hours after implantation. These grafts typically use a multilayer structure that allows the puncture site to "self-seal."

Systematic reviews have demonstrated that early cannulation grafts have similar patency and complication rates as standard cannulation grafts [1,42]. However, most of the included studies are small retrospective reviews with no evidence to suggest any early cannulation graft is better than another. One trial that compared early cannulation grafts with tunneled hemodialysis catheters for urgent dialysis reported reduced mortality and lower rates of bacteremia for early cannulation grafts [43]. In a later trial, 477 patients were randomly assigned to standard AV grafts or early cannulation AV grafts; primary, primary assisted, and secondary patency rates at 6 and 12 months were similar between the groups [44]. As expected, patients with early cannulation grafts had a significantly earlier time to cannulation compared with those with standard grafts (median time 3 days versus 19 days).

At 12 months, for the standard and early cannulation groups, respectively:

●Primary patency was 53.8 and 56.4 percent

●Primary assisted patency was 59.3 and 61 percent

●Secondary patency was 67.8 and 69.7 percent

Tapered grafts — Typically, AV grafts are created using a 6-mm straight graft. Tapered grafts are available that have one end with a smaller diameter, which is used for the arterial anastomosis. Commercially available tapered grafts transition from 4 to 6 or 7 mm. Tapered grafts are designed to reduce the flow volume through the graft and thus reduce the incidence of high-flow-related complications, including dialysis access-associated steal syndrome (DASS) and high-output heart failure. However, this has not been proven.

In a randomized trial of forearm loop grafts, there was no difference in patency or restenosis. The rate of DASS and high-output cardiac failure was very low, with no significant difference between the groups [45]. Of note, the study was powered to detect differences in patency but not DASS. In a review of over 3000 grafts, tapered grafts did not appear to affect primary patency, development of steal, or need for reintervention compared with nontapered grafts [46].

Some authors have also reported using a self-modified graft that goes from 6 to 8 mm [47]. In a small trial of 70 patients comparing 6-mm straight grafts with 6- to 8-mm tapered grafts in the straight brachial-axillary configuration, primary patency was higher in the tapered graft group, but there was no difference in secondary patency. However, more procedures were required in the straight graft group to maintain secondary patency. No DASS requiring intervention developed in either group.

HeRO grafts — The Hemodialysis Reliable Outflow (HeRO) graft consists of two parts: a 6-mm ePTFE graft and a nitinol-reinforced silicone single-lumen outflow catheter, termed the venous outflow component (VOC). The intent of the HeRO graft is to provide outflow for patients with central venous stenosis or occlusion. The HeRO is generally considered one of the options of last resort for patients who have exhausted conventional upper extremity AV fistula and AV graft sites. The use of the HeRO graft preserves thigh access sites for future use only after the HeRO graft has failed.

The ePTFE graft is anastomosed proximally to the brachial artery or other inflow artery. The outflow end of the ePTFE graft is then connected to the VOC, which typically enters the central venous circulation through the internal jugular vein. The distal tip of the catheter is positioned in the right atrium. The ePTFE portion of the HeRO graft requires two weeks for tissue ingrowth prior to puncture, just as any other standard ePTFE graft. An early access graft can also be used, with the use of an adapter [48]. This is useful in patients who have a central venous catheter in place and the presence of a known central venous stenosis/occlusion. The catheter can be exchanged for the HeRO, and the patient can resume his/her normal hemodialysis schedule.

In a trial comparing 52 HeRO grafts with 20 standard ePTFE graft controls, there were no significant differences in bloodstream infections, primary patency, assisted primary patency, or secondary patency during the 19 month follow-up period [49]. There was also no significant difference in the rate of interventions required. Of note, the study was stopped early and did not enroll to its full-power calculation due to concerns that the appropriate comparison would have been between a HeRO graft and tunneled catheter.

A prospective study of HeRO implants in 36 patients demonstrated a HeRO-related bacteremia rate of 0.7/1000 days, which was significantly lower compared with a tunneled dialysis catheter literature control rate of 2.3/1000 days [50].

A review comparing HeRO grafts to thigh grafts determined that the patency of thigh grafts was higher than the patency of HeRO grafts, with comparable infection risks [21]. In a later review of 409 HeRO grafts from eight studies, the primary and secondary pooled patency rates were found to be 21.9 and 59.4 percent, respectively [51].

Other grafts

Allografts — Allografts are also available as AV access conduits. Cryopreserved femoral vein is the allograft option that has most often been used to replace infected ePTFE [52].

Studies have demonstrated that the primary and secondary patency of cryopreserved vein is equivalent to that of ePTFE at one and two years [53,54]. Rates of reinfection are generally low [55,56]; however, in one series of 20 cryopreserved femoral veins placed in actively infected fields, in patients with multiple previous access infections, or in the thigh position, there was a 55 percent incidence of reinfection, and, more importantly, 55 percent of the grafts that became reinfected ruptured, resulting in one patient death [57].

Xenografts — Bovine carotid artery, mesenteric vein, and ureter have all been used as conduits for AV grafts. The purported advantage of these grafts over ePTFE is improved material compliance and resistance to infection.

Of these, bovine carotid artery is the most commonly used. Initial reports of outcomes for bovine carotid artery grafts demonstrated high rates of aneurysmal degeneration and rupture. With changes in the preparation methods of bovine carotid artery grafts, the incidence of aneurysmal degeneration and/or rupture appears to have decreased. In a prospective randomized trial comparing standard ePTFE with bovine carotid artery, there was no significant difference in secondary patency rates, but primary and primary assisted patency rates (figure 1 and table 1) were significantly higher at one year with the bovine carotid artery (60.5 versus 10.1 percent, and 60.5 versus 20.8 percent, respectively) [58]. There were no aneurysms/pseudoaneurysms or ruptures in the bovine carotid artery group at one year. Another small series of bovine carotid AV grafts demonstrated similar patency rates and no aneurysms/pseudoaneurysms or ruptures [59].

A multicenter trial conducted to evaluate the safety and effectiveness of bovine mesenteric vein for AV grafts found no difference in primary patency at one year compared to ePTFE; however, secondary patency was higher for bovine mesenteric vein, with a lower incidence of interventions [60]. There was a significantly lower incidence of infection in the bovine mesenteric vein group and no difference in the incidence of pseudoaneurysm.

A randomized trial comparing bovine ureter for AV grafts to ePTFE demonstrated no significant difference at one year in primary patency, primary assisted patency, or secondary patency (figure 1 and table 1) [61]. There was also no difference in freedom from infection at one year of the number of interventions required to maintain patency.

Tissue-engineered grafts — A number of tissue-engineered grafts have been tested in humans, but none is commercially available in the United States. These grafts demonstrate some promise for allowing repopulation and remodeling with host cells, which could potentially reduce the risk of infection and improve patency [24,62].

PROCEDURE

Anesthesia — Arteriovenous (AV) grafts can usually be constructed under local anesthesia, though regional block or general anesthesia can also be used [63]. There is some evidence that brachial plexus blocks may be beneficial for vascular access operations by causing regional sympathetic blockade, which results in arterial and venous vasodilation. (See "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Anesthesia'.)

Antimicrobial prophylaxis — Antibiotic prophylaxis is indicated at the time of the surgical creation or revision of an AV hemodialysis access (table 2 and table 3).

COMPLICATIONS OF AV GRAFT PLACEMENT — Complications related to arteriovenous (AV) graft placement can be categorized as local issues related to the access, vascular stenosis leading to graft dysfunction or failure (thrombosis), and ischemia or other systemic complications related to the physiologic changes imposed by the graft.

Malignancy (eg, angiosarcoma, others) has been reported at the site of hemodialysis AV access but far more commonly with AV fistulas; however, there has been one report case associated with an AV graft [64]. (See "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Complications of AV fistula placement'.)

Local problems

Bleeding — Excessive bleeding related to defects in hemostatic mechanisms in patients with end-stage kidney disease can cause bleeding in association with the creation of the AV graft but also during routine use with prolonged needle puncture bleeding. Issues related to the use and care of the AV graft before and after dialysis are discussed separately. (See "Overview of hemodialysis arteriovenous graft maintenance and thrombosis prevention".)

Intraoperative bleeding after the anastomoses of the AV graft have been created is usually related to needle hole bleeding from the graft material. The diameter of the needle on a typical 6-0 or 7-0 Prolene suture is larger than the diameter of the suture. For most graft material, except for the self-sealing early puncture grafts, this can result in some continued bleeding that can require a few extra minutes to control but is generally easily controlled using hemostatic agents such as cellulose products or thrombin. Once the needle holes seal, it is very uncommon for them to bleed again in the postoperative period.

Active bleeding with an expanding hematoma in the postoperative period is generally related to a technical error and should prompt return to the operating room to be corrected. A mild amount of swelling and minor hematoma around the anastomoses or in the graft tunnel is to be expected and will resolve on its own.

Seroma — Ultrafiltration of plasma across a prosthetic graft made of polytetrafluoroethylene (PTFE), also known as "weeping syndrome," occurs occasionally and forms a pocket of serous fluid that can become firm and gelatinous over time [65]. Seromas typically form in the arterial limb of the graft where intraluminal pressure is higher, although the same process can occur in the venous limb if there is significant central venous obstruction [66]. Seromas usually form slowly, beginning within 30 days after implantation of the graft; however, a more acute presentation mimicking a hematoma has been reported. Graft revision may become necessary.

Pseudoaneurysm — A pseudoaneurysm represents a focal disruption of the graft with blood collecting outside the vessel wall and contained by fibrous tissue. Pseudoaneurysms usually result from repeated cannulation in the same area of the access and are particularly problematic with AV grafts, occurring with increasing frequency over time as the graft material deteriorates. Cannulation through a pseudoaneurysm should be avoided. Pseudoaneurysms can be prevented by rotating the sites of needle insertion. (See "Overview of hemodialysis arteriovenous graft maintenance and thrombosis prevention", section on 'Cannulation and decannulation'.)

AV grafts with degenerative changes may require repair to prevent rupture. If a pseudoaneurysm is small (<5 mm), it may be possible to occlude the pseudoaneurysm using compression under ultrasonic guidance with or without the local injection of thrombin [67]. Grafts with more severe degenerative changes, such as those listed below, will require revision/repair , which may involve open surgical techniques, or possibly endovascular stent-grafting (in the absence of infection) [68-70].

The indications for revision/repair of pseudoaneurysm include:

●Pseudoaneurysm that is symptomatic

●Pseudoaneurysm that is ≥4 cm in diameter

●Pseudoaneurysm that threatens the viability of the overlying skin, regardless of diameter

●Evidence of infection

●Pseudoaneurysm that is expanding

●Large or multiple pseudoaneurysms that limit the number of cannulation sites.

Neuropathy — Median nerve dysfunction in long-term dialysis patients is most often due to local amyloid deposition, leading to carpal tunnel syndrome. (See "Dialysis-related amyloidosis".)

The vascular access also may contribute to this neuropathy in some cases via compression of the median nerve (due to the extravasation of blood or fluid) or via ischemic injury from a vascular steal effect (ischemic monomelic neuropathy) [71-74]. (See 'Vascular steal' below.)

Graft infection — Infection accounts for approximately 20 percent of hemodialysis AV access loss. Although antibiotic prophylaxis is indicated at the time of the surgical creation or revision of an AV hemodialysis access (table 2 and table 3), antibiotic administration with routine use of the access during hemodialysis has been unsuccessful in preventing infection. Staphylococcus aureus and, less commonly, Staphylococcus epidermidis are the predominant pathogens [75-79].

Risk factors for AV graft infection include pseudoaneurysms, hematomas (often due to inappropriate graft cannulation), severe pruritus and scratching over needle sites, the use of hemodialysis fistulas as a route of access for injection drug abuse, and manipulation of the access during secondary surgical procedures [80].

An underappreciated infective complication is the clinically silent infection of a clotted AV graft that is no longer being used. One study addressed this issue by performing indium scans in dialysis patients with nonfunctional grafts, 20 with fever and/or sepsis but without localizing signs, and 21 asymptomatic control patients [81]. Indium scans showed uptake in the graft in all patients with clinical infection and in 15 of the controls. Graft removal revealed infected clot in all patients, including 13 of the 15 controls with positive scans. The most commonly cultured organisms were S. aureus or S. epidermidis. Graft infection, even if clinically silent, must be entertained in the dialysis patient presenting systemic symptoms and signs of infection and positive localization on a nuclear study [82,83].

Infected AV grafts require surgical intervention [84]. Depending upon the extent of the infection, treatment involves graft exploration with partial excision of the affected graft material (if localized), subtotal graft excision, or complete (total) removal of the graft (algorithm 1) [85,86]. As an example, minimal infection that develops in an area of exposed graft can often be treated with intravenous antibiotics, excision of the exposed graft segment, and rerouting the graft through uninvolved tissue. Any skin overlying the graft that is compromised is excised [87]. The graft that remains must have adequate soft tissue and skin antimicrobial coverage. The graft should be evaluated frequently to ensure that the infection has been adequately controlled. Partial graft excision successfully manages the infection in 60 to 80 percent of patients and preserves the access, but meta-analyses of observational studies showed a higher risk of recurrent infection (26.6 versus 4.8 percent) and reoperation (20.1 versus 3.3 percent) for partial graft excision compared with total graft excision (infection [eight studies]: relative risk [RR] 0.23, 95% CI 0.13-0.41; reoperation [four studies]: RR 0.14, 95% CI 0.03-0.58) [86]. Mortality rates were similar between the groups.

Persistent fever or bacteremia following complete removal of an infected AV access should prompt the search for another source (eg, endocarditis, osteomyelitis) or metastatic infection. Metastatic infection is much more common with cuffed hemodialysis catheters but can occur with AV fistulas or grafts. Overall patient outcome appears to be much worse when an AV access is the source of metastatic infection [88]. (See "Clinical manifestations of Staphylococcus aureus infection in adults".)

Access flow-related problems — The AV graft is a high-flow, low-resistance system that results in increased flow to the extremity, leading to extremity swelling (usually temporary) and other complications related to the increased return flow (eg, heart failure, pulmonary hypertension). The diversion of flow through the AV graft away from the distal extremity can also cause a steal phenomenon (dialysis access-associated steal syndrome [DASS]).

Extremity swelling — Extremity swelling or swelling of the shoulder, chest wall, or breast can occur following AV access surgery. Mild-to-moderate extremity swelling is common initially following AV graft placement, and it usually subsides. If the problem persists beyond two weeks, an underlying problem will be found in approximately 25 percent of cases. This is most commonly central vein stenosis, which may not have been appreciated preoperatively. The diagnosis and treatment of central vein stenosis is reviewed separately [89]. (See "Central vein obstruction associated with upper extremity hemodialysis access".)

Swelling can also be due to venous valvular incompetence, which results in chronic elevation of the venous pressure in the extremity. The resulting venous hypertension can lead to skin discoloration, access dysfunction, and ulceration.

Cardiopulmonary problems — The rate of cardiopulmonary decompensation associated with AV grafts is similar to that of patients with an AV fistula. These issues are discussed separately. (See "Evaluation and management of heart failure caused by hemodialysis arteriovenous access" and "Pulmonary hypertension in patients with end-stage kidney disease".)

Coronary ischemia from symptomatic steal from an internal mammary artery coronary artery bypass from an ipsilateral upper extremity dialysis access can occur but is more commonly reported in association with AV fistulas. (See "Overview of hemodialysis arteriovenous graft maintenance and thrombosis prevention" and "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Coronary steal'.)

Vascular steal — Placement of an AV graft can reduce perfusion of the more distal extremity as a result of shunting ("steal") of arterial blood flow into the graft [90]. This is also called DASS. Symptomatic steal occurs in up to 20 percent of patients receiving an upper extremity access [91,92], with severe manifestations requiring intervention in 4 percent [93]. Although the presence of a significant arterial stenosis increases the likelihood, steal can occur in the absence of stenosis. (See "Hemodialysis access-induced distal ischemia", section on 'Dialysis access steal syndrome'.)

Vascular steal typically manifests a median of two days after the placement of an AV graft [93]. Severe ischemic symptoms, characterized by loss of sensation or weakness, may be more common among patients with diabetes and those of advanced age [71]. Less severe symptoms and signs, such as paresthesias and a sense of coolness with retained pulses, are more common and usually improve over a period of weeks with the development of collateral blood flow. Careful, frequent clinical evaluation and an alert nursing staff are necessary in this setting. Symptoms often worsen during dialysis sessions.

Physical examination can confirm a diagnosis of vascular steal by manually compressing the access and noting an improvement in the patient's symptoms. However, physical examination alone may not be accurate in identifying the anatomic cause of the vascular steal [94]. Thus, among patients presenting with symptoms of extremity ischemia, there should be a low threshold to obtain noninvasive vascular evaluation using duplex ultrasound, which may identify the presence of arterial stenosis and/or flow reversal, and physiologic tests such as digital waveforms and pressures with and without fistula compression, which are sensitive for a diagnosis of steal [95-97]. If noninvasive studies are unrevealing and ischemic symptoms persist, arteriography of the extremity may identify an anatomic problem [94].

Severe or persistent ischemic symptoms warrant treatment to prevent the development of permanent injury. If revascularization is not possible, the AV graft will require ligation. Percutaneous catheter-based intervention may be an option in patients with inflow arterial stenosis or progressive arterial occlusive disease in the extremity distal to the arteriovenous anastomosis [94,98]. If surgical intervention is required and preservation of the AV graft is a high priority, the procedure with the longest history and that has been most studied is the Distal Revascularization-Interval Ligation (DRIL) procedure (figure 2). With this procedure, the artery is ligated distal to the anastomosis to prevent retrograde flow and persistent steal, and perfusion to the hand is restored with a distal bypass procedure [99-107]. The ligation and bypass procedures can be performed at a single surgery; staged procedures are rarely needed [101,102]. Other surgical interventions that avoid having distal perfusion dependent upon the bypass graft include the Proximalization of Arterial Inflow (PAI) [108], Revision Using Distal Inflow (RUDI), and the Minimally Invasive Limited Ligation Endoluminal-assisted Revision (MILLER) procedures (figure 2) [109,110]. There are few direct comparisons between these procedures.

Ischemic monomelic neuropathy — Ischemic monomelic neuropathy (IMN) is a rare complication that is likely in the spectrum of ischemic steal but has distinct characteristics from the typical presentation. The incidence of IMN is difficult to determine from the literature but is in the range of less than 1 percent of vascular access creations [74]. IMN is characterized by immediate onset after the vascular access operation and is significantly more likely to occur in patients who have AV access creation with brachial artery inflow. In contrast to typical steal, patients with IMN have profound motor and sensory deficits without other associated manifestations of tissue ischemia such as tissue loss or loss of pulses. Electromyography performed on patients with IMN demonstrates signs of acute denervation, which can result in permanent neurologic damage. The treatment for IMN is immediate ligation of the vascular access [74]. (See "Hemodialysis access-induced distal ischemia", section on 'Ischemic monomelic neuropathy'.)

AV graft dysfunction and failure — AV graft dysfunction and failure related to stenotic vascular lesions is the most common complication of AV grafts. This issue is discussed elsewhere. (See "Hemodialysis arteriovenous graft dysfunction and failure".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Dialysis" and "Society guideline links: Hemodialysis vascular access" and "Society guideline links: Acute extremity ischemia".)

SUMMARY AND RECOMMENDATIONS

●All arteriovenous (AV) grafts possess similar characteristics. These generally include very low patient morbidity related to the procedure for most types of AV graft, but lower patency rates and increased rates of vascular steal and infection compared with AV fistulas. (See 'General characteristics' above.)

●For patients who require a chronic hemodialysis vascular access, an AV graft may be an appropriate choice as initial hemodialysis access (rather than an AV fistula), or as a secondary access if an AV fistula has failed to develop. (See 'General characteristics' above.)

●To be usable, the AV graft must provide adequate blood flow, be reliably cannulated, and be accessible in a seated position. (See 'Requirements for AV graft use' above.)

●Adequate preoperative evaluation prior to AV graft creation includes a history, physical examination, and arterial and venous evaluation. (See 'Physical evaluation' above.)

●Numerous prosthetic and biologic graft materials are available for AV graft creation. AV grafts should be referred to using anatomical designations that include the donor artery and outflow in their description and the type of conduit used. Data demonstrating clear superiority in performance of one graft material over another do not exist. In choosing graft material, consideration should be made for the timing in which the graft will need to be accessed for dialysis, the presence of/risk for infection, the experience of the surgeon, and cost. (See 'Types of AV grafts' above.)

●Among the possible AV grafts, we start as distal as possible on the upper extremity and exhaust the use of one upper extremity before moving to the contralateral upper extremity. (See 'Order of AV graft preference' above.)

●Complications associated with AV grafts include local problems associated with graft creation and use, such as hematoma, seroma, pseudoaneurysm formation, neuropathy, and graft infection. Changes in flow to the extremity can lead to extremity ischemia, and augmented venous return can have detrimental cardiopulmonary effects. (See 'Complications of AV graft placement' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Karen Woo, MD, who contributed to earlier versions of this topic review.