Multicenter evaluation of a polyurethaneurea vascular access graft as compared with the expanded polytetrafluoroethylene vascular access graft in hemodialysis applications

Quality assurance in surgical trials of arteriovenous grafts for haemodialysis: A systematic review, a narrative exploration and expert recommendations

BACKGROUND

Introducing new procedures and challenging established paradigms requires well-designed randomised controlled trials (RCT). However, RCT in surgery present unique challenges with much of treatment tailored to the individual patient circumstances, refined by experience and limited by organisational factors. There has been considerable debate over the outcomes of arteriovenous grafts (AVG) compared to AVF, but any differences may reflect differing practice and potential variability. It is essential, therefore, when considering an RCT of a novel surgical procedure or device that quality assurance (QA) is defined for both the new approach and the comparator. The aim of this systematic review was to evaluate the QA standards performed in RCT of AVG using a multi-national, multi-disciplinary approach and propose an approach for future RCT.

METHOD

The methods of this have been previously registered (PROSPERO: CRD420234284280) and published. In summary, a four-stage review was performed: identification of RCT of AVG, initial review, multidisciplinary appraisal of QA methods and reconciliation. QA measures were sought in four areas - generic, credentialing, standardisation and monitoring, with data abstracted by a multi-national, multi-speciality review body.

RESULTS

QA in RCT involving AVG in all four domains is highly variable, often sub-optimally described and has not improved over the past three decades. Few RCT established or defined a pre-RCT level of experience, none documented a pre-trial education programme, or had minimal standards of peri-operative management, no study had a defined pre-trial monitoring programme, and none assessed technical performance.

CONCLUSION

QA in RCT is a relatively new area that is expanding to ensure evidence is reliable and reproducible. This review demonstrates that QA has not previously been detailed, but can be measured in surgical RCT of vascular access, and that a four-domain approach can easily be implemented into future RCT.

Does a small-diameter rod-type tunneler reduce postoperative swelling? An evaluation using a canine arteriovenous graft model

PURPOSE

Sheath-type tunnelers are frequently used to create vascular access using vascular grafts. However, during vascular access creation, tunnelers damage the surrounding tissues, consequently causing problems, such as swelling, failure to heal, and infection. This study evaluated a novel rod-type tunneler that was designed to prevent tunneler-related tissue damage and its sequelae.

METHODS

We developed a small-diameter rod-type tunneler that reduces injuries during subcutaneous tunnel creation. The rod diameter of this tunneler is smaller than the vascular graft diameter being implanted. It has a structure in which a vascular graft is implanted at a target site by grasping and pulling the vascular graft. Three dogs were used in the experiment, and arteriovenous grafts were created using a rod-type and a sheath-type tunneler on the left and right thighs, respectively, with a different type of commercially available graft used in each dog. The edema of the tissues surrounding the vascular graft was measured at 11 sites by ultrasonography at prespecified intervals.

RESULTS

Compared with implantation using a sheath-type tunneler, when the self-sealing Rapidax II was implanted using the small-diameter rod-type tunneler, the postimplantation edema (degree of change) decreased by 28-53% and 80-247% in the peri-vascular-graft area and within the loop, respectively. The MAXIFLO and SEALPTFE did not significantly reduce postoperative edema but exhibited a tendency for improved postimplantation tissue healing.

CONCLUSIONS

The reduced-diameter rod-type tunneler may be a useful device for vascular graft implantation.

Novel electrospun polyurethane grafts for vascular access in rats

OBJECTIVES

The purpose of this study is to develop a new and improved polyurethane (PU) graft using electrospinning and chemical modifications for hemodialysis patients, which will replace the current standard, polytetrafluoroethylene (PTFE) graft. The chemical modifications aim to improve hemocompatibility and reduce thrombogenicity and neointimal hyperplasia.

METHOD

The study population was randomized and divided equally into four groups; one control group received a PTFE graft, and three treatment groups received three different types of polyurethane grafts. Two duplex measurements were performed directly on the graft on the same locations, followed by a histologic examination.

RESULTS

In the first few days after the implantation animals lost some weight, it took a week to recover to pre-surgical weight. Throughout the 28 days, there was no significant difference between animals in wound, activity, and the general appearance. PTFE and PU A groups have lower compliance or reduced graft diameter due to neointimal hyperplasia development on Doppler interrogation. The histological analysis showed limited neointimal hyperplasia development and no excessive inflammatory response to any of the grafts.

CONCLUSION

This study demonstrates that animals with polyurethane grafts show better blood flow because the developed NIH was inconspicuous, as indicated by the different velocity measure than controls on Duplex and minimal NIH development microscopically.

A critical review of fibrous polyurethane-based vascular tissue engineering scaffolds

Certain polymeric materials such as polyurethanes (PUs) are the most prevalent class of used biomaterials in regenerative medicine and have been widely explored as vascular substitutes in several animal models. It is thought that PU-based biomaterials possess suitable hemo-compatibility with comparable performance related to the normal blood vessels. Despite these advantages, the possibility of thrombus formation and restenosis limits their application as artificial functional vessels. In this regard, various surface modification approaches have been developed to enhance both hemo-compatibility and prolong patency. While critically reviewing the recent advances in vascular tissue engineering, mainly PU grafts, this paper summarizes the application of preferred cell sources to vascular regeneration, physicochemical properties, and some possible degradation mechanisms of PU to provide a more extensive perspective for future research.

Patient characteristics predict patency of early-cannulation arteriovenous grafts

There is a new emphasis on tailoring appropriate vascular access for hemodialysis to patients and their life-plans, but there is little known about the optimal use of newer devices such as early-cannulation arteriovenous grafts (ecAVG), with studies utilising them in a wide variety of situations. The aim of this study was to determine if the outcome of ecAVG can be predicted by patient characteristics known pre-operatively. This retrospective analysis of 278 consecutive ecAVG with minimum one-year follow-up correlated functional patency with demographic data, renal history, renal replacement and vascular access history. On univariate analysis, aetiology of renal disease, indication for an ecAVG, the number of previous tunnelled central venous catheters (TCVC) prior to insertion of an ecAVG, peripheral vascular disease, and BMI were significant associates with functional patency. On multivariate analysis the number of previous TCVC, the presence of peripheral vascular disease and indication were independently associated with outcome after allowing for age, sex and BMI. When selecting for vascular access, understanding the clinical circumstances such as indication and previous vascular access can identify patients with differing outcomes. Importantly, strategies that result in TCVC exposure have an independent and cumulative association with decreasing long-term patency for subsequent ecAVG. As such, TCVC exposure is best avoided or minimised particularly when ecAVG can be considered.

Long-term outcomes of anterior chest wall arteriovenous graft with polyurethane

BACKGROUND

Anterior chest wall arteriovenous graft (ACWAVG) is one option for haemodialysis patients when vessels of the upper extremities become exhausted. We report here the long-term outcomes of ACWAVG with polyurethane.

METHODS

From April 2005 to October 2015, nine ACWAVGs with polyurethane grafts were created. We observed patients until April 2019 and evaluated graft patency, interval from operation to first cannulation, and numbers of interventions and complications.

RESULTS

Primary patency rate and secondary patency rate of 6, 12 and 24 months were 55.3%, 33.3%, 33.3% and 77.8%, 55.6%, 55.6% respectively. Mean interval from operation to first cannulation was 3 days. Infection rate and kinking formation rate were slightly higher than previous reports of ACWAVGs with expanded polytetrafluoroethylene (ePTFE). However, one patient was able to keep using a single graft for 166 months with multiple interventions.

CONCLUSIONS

Slight disadvantage are seen with patency rate and complication rate in polyurethane ACWAVG compare to ePTFE. However, when early cannulation is required, polyurethane is worth to consider for creating ACWAVG.

Traditional versus Early-access Grafts for Hemodialysis Access: A Single-institution Comparative Study

In those patients requiring urgent hemodialysis, the use of early-access grafts may reduce the need for temporary hemodialysis catheters and their resultant complications such as infection and central venous stenosis. We review a consecutive group of patients undergoing placement of a traditional polytetrafluoroethylene (PTFE) graft as compared with a cohort of patients who underwent insertion of a trilaminate PTFE vascular graft (TPVG). During the period from January 2008 to December 2009, 65 sequential patients received a traditional PTFE graft with 78 subsequent patients having a TPVG inserted. Factors examined included use of temporary hemodialysis catheters during the period of graft maturation, incidence of infection, and primary and secondary graft patency. For all patients, incidence was reported as observed during the first year after graft insertion. With the use of the TPVG, need for temporary hemodialysis catheters was reduced from 91 to 32 per cent, and 1-year overall graft patency was improved from 36 to 77 per cent ( P < 0.01). We report that the use of a trilaminate PTFE graft allowed early access, reduced the need for temporary hemodialysis catheters, decreased overall graft complication rates, and significantly improved 1-year patency.

Hemodialysis Reliable Outflow graft: A valid option in patients with central venous stenosis

INTRODUCTION

Central venous stenosis can be the main obstacle to the creation of an autologous vascular access in the upper limbs. The Hemodialysis Reliable Outflow graft was developed to provide an upper limb vascular access option to such patients, avoiding alternative, less advantageous options, such as lower limb vascular accesses or central venous catheters. Its advantages include catheter avoidance and, in case of lower limbs accesses, reduction of the ischemic risk and iliac vein thrombosis, potentially compromising a future kidney transplant.

PATIENTS AND METHODS

Revision of the clinical files of the four patients who were placed a Hemodialysis Reliable Outflow device in our Center, including demographic variables, implantation technique characteristics, surgical complications, episodes of infection and thrombosis of the access, and need to place a transitory central venous catheter to undergo hemodialysis treatment.

RESULTS

Four Hemodialysis Reliable Outflow grafts were placed, which resulted in a significant improvement in the dialysis efficacy in all patients, with a median raise in the Kt/V of 36.7%. Two cases needed thrombectomy, one of which was unsuccessful. The actual time of patency varies between 3 and 28 months.

CONCLUSION

Our experience with the Hemodialysis Reliable Outflow device showed that it was a safe option for patients with central venous stenosis and was associated with good clinical and analytic outcomes.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for hemodialysis vascular access since 1996. Since the last update in 2006, there has been a great accumulation of new evidence and sophistication in the guidelines process. The 2019 update to the KDOQI Clinical Practice Guideline for Vascular Access is a comprehensive document intended to assist multidisciplinary practitioners care for chronic kidney disease patients and their vascular access. New topics include the end-stage kidney disease "Life-Plan" and related concepts, guidance on vascular access choice, new targets for arteriovenous access (fistulas and grafts) and central venous catheters, management of specific complications, and renewed approaches to some older topics. Appraisal of the quality of the evidence was independently conducted by using a Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and interpretation and application followed the GRADE Evidence to Decision frameworks. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

A pilot study comparing bovine mesenteric artery and expanded polytetrafluoroethylene grafts as non-autogenous hemodialysis options

BACKGROUND

Many dialysis patients do not have the necessary conditions for construction of a native arteriovenous fistula (AVF). Expanded Polytetrafluoroethylene (ePTFE) vascular prostheses are the most widely-used option, but it is known that they are inferior to native vein AVFs.

OBJECTIVES

To identify a graft with superior performance to ePTFE, comparing their results with those of AVFs made from bovine mesenteric arteries treated with L-Hydro technology (Labcor Laboratories ®).

METHODS

A prospective and controlled study of 10 patients with AVFs constructed with ePTFE and 10 patients with L-Hydro bioprostheses, matched for comorbidities. The variables studied were: primary patency, assisted primary patency, and secondary patency, surgical manipulability, and prevalence of infections. The performance of prostheses was assessed by duplex-scan and repeated consultations with health professionals at hemodialysis clinics. The chi-square test was used for statistical analysis.

RESULTS

After 1 year of postoperative follow-up, secondary and primary patency rates were higher for L-Hydro than ePTFE AVFs. Fewer interventions were needed to maintain AVF patency in the L-Hydro AVF group. The most common complication was graft thrombosis, which was more frequent in the ePTFE group. While the figures indicate more favorable outcomes in the L-Hydro AVFs, this could not be confirmed with the statistical treatment employed.

CONCLUSIONS

The L-Hydro graft appears to be a valuable alternative option for AVFs, since it seems to require fewer interventions to maintain patency when compared to ePTFE grafts.

Challenges of Hemodialysis Access for High Risk Patients: Impact of Mesenteric Vein Bioprosthetic Graft

Objective

The purpose of this study is to compare in a prospective fashion the performance of a new bioprosthesis, the mesenteric vein bioprosthesis (MVB), in patients who have had multiple failed ePTFE grafts. Performance measures include primary patency rates, assisted-primary patency rates, secondary patency rates, complications, and the number of interventions required to maintain graft patency. Study: From October 1999 to February 2002, 276 hemodialysis access grafts were implanted in a multicenter study. Of those grafts, 74 were placed in patients with a prior history of ≥ 3 failed prosthetic grafts (mean = 3.5 grafts, range = 3–6 grafts). Fifty-nine grafts were constructed with MVB, and 15 grafts with ePTFE as a concomitant control. Mean follow-up was 11.5 months. In the MVB group, 79.7% were African-Americans, 61% were females, and 23.7% were hypercoagulable. Of the ePTFE group, 86.7% were African-Americans, 46.7% were female, and 13.2% were hypercoagulable.

Results

Per Kaplan-Meier curves, the primary patency rate of the MVB group at 12 months was 33% vs the ePTFE group of 18% (p=0.120); the assisted-primary patency rates at 12 months were 45% MVB vs 18% ePTFE (p=0.011). The secondary patency rates at 12 and 24 months for the MVB group were 67% and 59%, respectively, vs 45% and 15% for the ePTFE group (p=0.006). During the follow-up time period, 80% of the ePTFE grafts were abandoned compared to 34% of the MVB group. Infection and thrombosis rates in the MVB group were lower than the ePTFE group. The infection rate for the MVB group requiring intervention was 0.07 events/graft year (gt/y) compared to 0.30 events/gt-y for ePTFE (p=0.04). A thrombosis rate of 0.69 events/gt-y occurred in the MVB group whereas 2.50 events/gt-y presented in the ePTFE group (p<0.01). Conclusion: In this study, high-risk patients (defined as those having multiple failed prosthetic grafts for hemodialysis) in whom the MVB conduit for hemoaccess was implanted, showed significant improvement in assisted-primary and secondary patency rates compared to the ePTFE cohort. The MVB group, however, did not have a statistically better primary patency rate compared to the ePTFE group. The MVB patient also had fewer thrombotic and infectious events and an overall reduction in the number of interventions while maintaining a permanent access site. This new bioprosthesis should be the conduit of choice in the complex group of patients as it offers assisted-primary and secondary patency rates similar to those commonly experienced by patients without a history of multiple graft failures.

Evaluation of Gore-Tex Graft Patency in Hemodialysis Access

Aim

The purpose of this retrospective study was to analyze the patency and complications of Gore-Tex grafts used in hemodialysis (HD) access.

Methods

In the last 16 years, 1649 surgical procedures were performed on 655 patients to ensure and maintain permanent HD access. The study group consisted of 64 HD patients on whom 81 vascular synthetic PTFE Goretex grafts were performed. There were 28 males and 36 females, 3 of them were children (4.7%). Mean age was 54.2 years (range 15–77). Two types of Gore-Tex prosthesis were used: Diastat and Stretch. All grafts were implanted in the upper extremities. Kaplan-Meier survival curves were calculated to determine primary and secondary patency. Log-rank analysis was used to determine differences between curves.

Results

Primary and secondary patency at 12 months was 52.5% and 67.5%, and at 18 months respectively 41.5% and 58.2%. The Diastat graft had a lower primary and secondary patency compared with the Stretch graft (respectively p = 0.02 and p = 0.008). Factors such as gender, coexisting diabetes and hypertension did not determine graft patency. Thrombosis was one of the most frequent complications. The remaining complications included stenosis, pseudoaneurysms, infection, steal syndrome and seroma.

Conclusion

On the basis of our experience Stretch grafts appear a better option for creating vascular access for HD than Diastat grafts.

Insertion of Short Introducer Sheaths into a Polyurethane Vascular Access Graft for Immediate Hemodialysis Access

While native AV fistulae are considered the “gold standard” for hemodialysis patients in need of long-term access, synthetic grafts are the best option for patients who are not candidates for an AV fistula. While AV fistulae should be allowed to mature for 3 – 4 months prior to cannulation, PTFE grafts may be cannulated 14 days after placement. Despite the benefit of earlier cannulation in PTFE graft recipients compared to AV fistulae patients, one critical limitation is that immediate post-operative cannulation is not possible. The self-sealing nature of the polyurethane Vectra® Graft overcomes the time restriction until first cannulation, allowing much earlier vascular access than conventional PTFE grafts. We describe here a procedure for insertion of 5-French DialEase™ Introducer Sheaths into the Vectra Graft for immediate, post-operative hemodialysis access. This procedure eliminates time restrictions until first cannulation of the Vectra Graft; the sheath's large diameter side-port ensures high flow for efficient hemodialysis. Moreover, insertion of the sheath into a new or existing Vectra Graft provides vascular access for inspection of the graft anastomoses, angiography, angioplasty, venography, and declotting procedures. The post-operative introduction of DialEase Sheaths into a Vectra Graft for immediate hemodialysis was successfully performed in 35 patients. All patients then immediately received high-flow hemodialysis (400 – 500 ml) with venous pressures ≤ 125 mmHg and negative arterial pressure ∼100 mmHg. To date, there have been no infections, immediate graft thrombosis or other complications associated with this procedure, and all patients have remained free of anastomotic problems.

Early cannulation graft Flixene™ for conventional and complex hemodialysis access creation

PURPOSE

The Flixene™ (Atrium™, Hudson, NH) is a trilaminate composite polytetrafluoroethylene (PTFE) graft that allows access within 72 hours. We evaluate our initial experience with this device for conventional and complex hemodialysis access creation.

METHODS

Retrospective review in end-stage renal disease (ESRD) patients who underwent access creation with Flixene from January 2013 to July 2014. For our analysis, the patients were divided in two groups: those with complex access configurations tunneled in the chest and/or abdominal wall (thoraco-abdominal wall access [TAWA]), and those tunneled in conventional sites (extremity access [EA]). Patient's demographics, indications, complications, reinterventions, patency rates and factors influencing outcomes were evaluated.

RESULTS

In 19 patients (54% men; mean age 44 years ± 18), 24 grafts were implanted, (13 EA [54%] vs. 11 TAWA), all patent after surgery. Central venous occlusive disease (CVOD) was present in all patients with TAWA and in 7/13 (54%) EA patients (p = 0.016). Early cannulation (within 72 hours) was successful in 12 EA and 5 TAWA grafts (p = 0.044). Complication rates including infection, thrombosis, bleeding and steal syndrome were 8/11 (73%) in TAWA and 5/13 (38%) in EA (p = 0.02). At 12 months, primary patency rates for EA and TAWA were 25% and 41%; secondary patency rates were 55% and 41%, respectively.

CONCLUSIONS

Early cannulation (EC) grafts are viable alternatives for conventional and complex access creation that allowed early cannulation (<72 hours) in 17 (70%) of our cases. Primary and secondary patency rates at 12 months were equivalent to data reported on ePTFE grafts.

Lower Extremity Permanent Dialysis Vascular Access

Hemodialysis remains the most commonly used RRT option around the world. Technological advances, superior access to care, and better quality of care have led to overall improvement in survival of patients on long-term hemodialysis. Maintaining a functioning upper extremity vascular access for a prolonged duration continues to remain a challenge for dialysis providers. Frequently encountered difficulties in clinical practice include (1) a high incidence of central venous catheter-related central vein stenosis and (2) limited options for creating a functioning upper extremity permanent arteriovenous access. Lack of surgical skills, fear of complications, and limited involvement of the treating nephrologists in the decision-making process are some of the reasons why lower extremity permanent dialysis access remains an infrequently used option. Similar to upper extremity vascular access options, lower extremity arteriovenous fistula remains a preferred access over arteriovenous synthetic graft. The use of femoral tunneled catheter as a long-term access should be avoided as far as possible, especially with the availability of newer graft-catheter hybrid devices. Our review provides a summary of clinical evidence published in surgical, radiology, and nephrology literature highlighting the pros and cons of different types of lower extremity permanent dialysis access.

A two-year experience with a rapid access, self-sealing, polycarbonate urethane nanofiber vascular access graft for hemodialysis

OBJECTIVE

Evaluating the safety and efficacy of the AVflo™ graft in terms of patency and complications (early and late) over 2 years.

MATERIALS AND METHODS

Twelve end-stage renal disease (ESRD) patients (age: mean 68.5 ± 10 years) were followed up for a mean period of 946 ± 570 days after receiving an implantation of the graft for HD. The grafts were implanted at the lower arm (loop configuration), upper arm (straight configuration) and the thigh (loop configuration). First dialysis was performed at day 7 (3-21) following implantation.

RESULTS AND DISCUSSION

After a mean follow up of 24 months, the primary patency was 56% and the secondary patency was 82%. In this group, AVflo™ shows similar if not superior efficacy and safety to that of available grafts in terms of safety, complications, and long-term patency.

Arteriovenous Graft Configuration in Hemodialysis: Does it Matter?

Purpose

The current guidelines for arteriovenous graft (AVG) configuration in hemodialysis state the following sequence: forearm loop, upper arm straight or curved and upper arm looped. These recommendations are based upon literature from the 1980s. Modern patient demographics and patient treatment algorithms, i.e., the Fistula First initiative (FFI), have greatly changed the current practice environment. It is not clear if these changes alter the outcomes of AVGs based upon configuration.

Methods

The most recent National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF/K-DOQI) guidelines for vascular access were reviewed. Articles cited to support recommendations for AVG configuration were evaluated. The following search terms: arteriovenous graft configuration, access configuration, PTFE configuration in hemodialysis and straight, looped, curved graft configuration were used to search PubMed, Ovid, Medline and Google scholar. Articles that included data comparing AVG configuration were included. Citations within those articles were examined for publications overlooked in the initial search. Four articles and one abstract were reviewed and separated into pre- and post-FFI groups.

Results

Pre-FFI articles demonstrate superiority of forearm looped AVG over straight forearm grafts. Post-FFI, the literature suggests that primary patency, thrombosis and steal are not affected by configuration and location, although looped configuration may have superior secondary patency.

Conclusions

The available literature is mixed regarding the effect of configuration on AVG outcomes. Current studies illustrate the effect may be limited and that larger randomized controlled trials are necessary to draw firm conclusions. Regardless, adequate inflow and an appropriately sized outflow vein are paramount for optimal graft performance.

Long-Term Results of PTFE Grafts

Vascular surgeons are essential in “lifeline” creation for hemodialysis patients and should be the central player in any multidisciplinary access service together with nephrologists, dialysis staff and interventional radiology. In this position, access surgeons are involved in complicated clinical decision making regarding primary and secondary access selection, which throughout the last decade has been largely aided, and influenced, by national and international guidelines as well as other initiatives. These recommendations, unanimously and appropriately, advocate the placement of native fistulas over synthetic grafts (the majority grafts from expanded polytetrafluoroethylene, ePTFE, herein referred to as PTFE) based on the superiority of fistulas with respect to complications such as infections and thrombosis. Nevertheless, the use of PTFE grafts for hemodialysis access is an accepted and firmly established alternative to native fistulas where data today reveal unwanted consequences to overinterpretation of established guidelines such as increased catheter use. This information highlights a need for an adjustment of access selection strategies based on patient-centered algorithms. Here, available results on PTFE graft performance in hemodialysis access is recapitulated, with respect to both conventional grafts and technical modifications, and conclude with a modified approach to primary access selection.

A Patient with Recurrent Arteriovenous Graft Thrombosis

Arteriovenous grafts (AVGs) are prone to frequent thrombosis that is superimposed on underlying hemodynamically significant stenosis, most commonly at the graft-vein anastomosis. There has been great interest in detecting AVG stenosis in a timely fashion and performing preemptive angioplasty, in the belief that this will prevent AVG thrombosis. Three surveillance methods (static dialysis venous pressure, flow monitoring, and duplex ultrasound) can detect AVG stenosis. Whereas observational studies have reported that surveillance with preemptive angioplasty substantially reduces AVG thrombosis, randomized clinical trials have failed to confirm such a benefit. There is a high frequency of early AVG restenosis after angioplasty caused by aggressive neointimal hyperplasia resulting from vascular injury. Stent grafts prevent AVG restenosis better than balloon angioplasty, but they do not prevent AVG thrombosis. Several pharmacologic interventions to prevent AVG failure have been evaluated in randomized clinical trials. Anticoagulation or aspirin plus clopidogrel do not prevent AVG thrombosis, but increase hemorrhagic events. Treatment of hyperhomocysteinemia does not prevent AVG thrombosis. Dipyridamole plus aspirin modestly decreases AVG stenosis or thrombosis. Fish oil substantially decreases the frequency of AVG stenosis and thrombosis. In patients who have exhausted all options for vascular access in the upper extremities, thigh AVGs are a superior option to tunneled internal jugular vein central vein catheters (CVCs). An immediate-use AVG is a reasonable option in patients with recurrent CVC dysfunction or infection. Tunneled femoral CVCs have much worse survival than internal jugular CVCs.

Timing of cannulation of arteriovenous grafts: are we too cautious?

BACKGROUND

Timing of first cannulation of an arteriovenous graft has been the subject of great debate for clinicians worldwide. In this paper, we reviewed the current literature on the timing of first cannulation of arteriovenous grafts.

METHODS

Searches of PubMed, Medline and the Cochrane Library were performed using specific search terms to identify articles, dealing primarily with the timing of dialysis graft cannulation.

RESULTS

Following strict inclusion/exclusion criteria by two reviewers, eleven studies were included and divided into subgroups for ePTFE and new generation grafts.

CONCLUSIONS

The current literature does not seem to support the current guidelines as there is no evidence to suggest that a delay in cannulation of grafts will improve graft survival and patency.

Early Cannulation Prosthetic Graft (Acuseal™) for Arteriovenous Access: A useful option to provide a Personal Vascular access Solution

Purpose

Early cannulation arteriovenous grafts (ecAVGs), such as the GORE® Acuseal™, have “low bleed” properties permitting cannulation within 24 hours of insertion. They may provide an alternative to tunneled central venous catheters (and associated line complications) in patients requiring urgent vascular access.

Methods

We present our early experience of 37 patients treated with the GORE® Acuseal™ ecAVG.

Results

A total of 11 upper limb, 24 lower limb and 2 complex graft procedures were performed. Indications for ecAVG were as follows: bridge to transplantation (21.6%); bridge to arteriovenous fistula (AVF) maturation (8.1%); AVF salvage (8.1%); no native options (67.6%, including 17 patients with bilateral central vein stenosis); 36 AVGs (97.3%) were successfully cannulated. Mean time to first cannulation: 30.4±23.4 hours (range: 2–192). Primary and secondary patency rates at 3, 6 and 12 months were 64.9%, 48.6%, 32.4% and 70.2%, 59.4%, 40.5% respectively. The systemic bacteremia rate was 0.2 per 1,000 access days. There was one perioperative death. Other complications included hematoma at cannulation sites (n=9), pseudoaneurysm (n=3) and local infection at graft site (n=6). A total of 26 of 37 patients (70.6%) achieved a “personal vascular access solution”: bridge to transplantation (n=8), bridge to functioning AVF/interposition AVG (n=5), maintenance hemodialysis via ecAVG (n=13); death with functioning AVG (n=1).

Conclusions

Early experience with the GORE® Acuseal™ is encouraging. Patency and bacteremia rates are at least comparable to standard polytetrafluoroethylene grafts. ecAVGs have permitted cannulation within 24 hours of insertion and line avoidance in the majority of patients. Nearly three-quarters of patients achieved a definitive “personal vascular access solution” from their ecAVG.

Initial Experience with the Gore® Acuseal Graft for Prosthetic Vascular Access

Purpose

The purpose of this study is to report the short-term results of the Gore® Acuseal graft for prosthetic vascular access (pVA) in patients with end-stage renal disease on hemodialysis.

Methods

Between October 2011 and October 2013, all the consecutive patients who underwent implantation of a new expanded Polytetrafluoroethylene (ePTFE) tri-layer graft were included in the study. Primary and secondary patency rate, time to first cannulation, and complications were recorded. Follow-up was performed at 1, 3, 6, and 12 months after the intervention.

Results

Thirty ePTFE tri-layer heparin bonded grafts were implanted in 18 males and 12 females. The graft configuration was radial-basilic (n=12, 40%), brachial-basilic (n=10, 33.3%), femoro-femoral (n=3, 10.0%), radial-cephalic (n=2, 6.7%), radial-antecubital forearm (n=2, 6.7%), and brachial-axillary (n=1, 3.3%). No patient was lost during a mean follow-up time of 6.3±5.9 months (range, 1-24; median, 5). Mean time to first cannulation was 2.4±1.2 days (range, 1-15). Primary functional patency rate was 68.0% ± 10 at 6 and 12 months. Secondary patency rate was 93.3% ± 6 at 6 and 12 months. Pseudoaneurysm, bleeding, seroma, or graft infection was never observed.

Conclusions

In our experience, the Gore® Acuseal graft was useful and safe. Early cannulation was always performed, and structural complications did not occur. Primary functional and secondary patency rate are satisfactory in the short term.

Early Experience with a Newly Developed Electrospun Polycarbonate-urethane Vascular Graft for Hemodialysis Access

Purpose

In this pilot study, we tested a newly developed electrospun multilayered, self-sealing graft, AVflo™, specifically designed for early hemodialysis access.

Methods

Ten eligible consenting patients had a polycarbonate-urethane graft (AVflo™) implanted and were followed up prospectively for at least six months. Performance measures included graft patency, complications and time to first cannulation. Mean age of the patients was 66.7 ± 10 years. Chronic glomerulonephritis was the most common cause of renal failure. A total of 70% of the patients had a history of previous vascular access and 40% history of minimally invasive radiologic procedures for patency maintenance. In 40% of the cases the need for AV graft implantation was because of recurrent infections from permanent catheter for dialysis. Seven grafts were placed in the upper arm and three in the thigh. Mean follow up was 230 ± 75 days.

Results

There were no systemic or local reactions to the graft and we did not report any graft infections. Two grafts thrombosed because of severe bleeding post-cannulation due to an incorrect needle puncture. Both grafts were successfully thrombectomized. Primary and secondary patency rates at six months were 60% and 78%, respectively. These patency rates were comparable to those reported for other polyether-urethane and ePTFE grafts. Median time to first cannulation was seven days (3-21) and all puncture sites sealed in less than five minutes.

Conclusions

This newly developed electrospun polycarbonate-urethane graft is safe in humans, permits early access obviating the need for venous catheters, and has equivalent patency as other prosthetic grafts.

Dialysis access

Although hemodialysis access procedures are considered the most common vascular procedures performed by either general or vascular surgeons, there is a paucity of level-one evidence in the literature. Randomized controlled trials are limited, and most of these studies have small sample sizes compared with other areas of vascular surgery, that is, carotid or aneurysm studies. We summarize the results of the world's literature for arteriovenous access in table format as a tool for those specialists managing patients with arteriovenous access procedures.

Early Cannulation Prosthetic Graft (Flixene™) for Arteriovenous Access

Purpose

Preferred hemodialysis (HD) access is an autologous fistula. Vascular grafts are used in patients with vessels unsuitable to accomplish an arteriovenous fistula (AVF). It is recommended that most current grafts mature in situ for 2–3 weeks before being accessed. Graft complications occur because the structure was not designed for the trauma of repeated cannulation. This study graft has a different structure that enables early use. Its design minimizes weeping through the graft walls and is meant to endure repeated access, thus minimizing the use of HD catheters. The purpose of this study was to show that the Flixene™ graft can be safely placed in patients where fistulas have failed and can be cannulated in 24–72 hr, while maintaining patency rates similar to other polytetrafluoroethylene (PTFE) grafts on the market. Flixene™ configuration should also reduce the incidence of pseudoaneurysms and seromas.

Methods

A prospective two-center study placed 33 grafts in 33 patients; graft efficacy, post-operative complications, and patency were evaluated. Ease of cannulation and dialysis center complications related to early cannulation were documented. Six month follow-up data was analyzed.

Results

Successful access was achieved in all 33 patients within 72 hr (29 patients within 24 hr). Overall primary patency at 6 months was 49%; primary-assisted patency at 6 months was 80%. No pseudoaneurysms or seromas were documented at 6 months. Complications were typical of graft access.

Conclusion

Early cannulation was successful in all patients. Primary and secondary patency rates at 6–months were equivalent to other data reported on PTFE grafts. Flixene™ successfully prevented pseudoaneurysm and seroma formation at 6 months of prospective follow-up. This graft is a better last-resort option for patients who cannot receive a fistula, compared to double-lumen cuffed catheters.

Long-term complication and patency rates of Vectra and IMPRA Carboflo Vascular Access Grafts with aggressive monitoring, surveillance and endovascular management

The purpose of this study is to compare infection, pseudoaneurysm formation and patency rates during long-term follow-up of polyurethane and polytetrafluoroethylene (PTFE) vascular access grafts maintained with contemporary endovascular methods. During a 34-month period, 239 polyurethane and 125 carbon-impregnated PTFE vascular access grafts were placed in 324 consecutive patients. Thirty-six patients (9.9%) developed a pseudoaneurysm (anastomotic, n = 6 or at the needle-stick site, n = 30). An additional 19 patients (5.2%) required graft excision for infection. Three-year graft infection and pseudoaneurysm formation (at needle-stick site) rates were similar in polyurethane and PTFE grafts (11% versus 8%, P = 0.61, and 17% versus 23%, P = 0.72, respectively). Three-year secondary patency was better in polyurethane than PTFE grafts (69% versus 57%, respectively, P = 0.012). Straight upper arm polyurethane grafts had the best secondary patency ( P = 0.001). Contemporary long-term secondary patency of vascular access grafts is satisfactory. Further follow-up is necessary to compare late infection and pseudoaneurysm formation rates.

Safety and Efficacy of Electrospun Polycarbonate-Urethane Vascular Graft for Early Hemodialysis Access: First Clinical Results in Man

Objectives

The purpose of this study was to assess the safety and efficacy of an electrospun multilayered, self-sealing polycarbonate-urethane graft for early hemodialysis access in patients.

Method

Seventeen eligible consenting patients had a polycarbonate-urethane graft (AVflo™) implanted and followed up prospectively for 12 months or to the end of secondary patency. Performance measures included graft patency, complications, time to first cannulation, and hemostasis times after needle withdrawal.

Results

All patients were of Asian origin (mean age 57 years, range 29–78). Diabetes mellitus was the most common cause of renal failure (52.9%). There were no systemic or local reactions to the graft. Five patients (29.4%) died due to medical complications unrelated to the device. There was 1 pseudoaneurysm, 3 infected grafts that subsequently thrombosed, and 1 primary thrombosis associated with thrombophilia. One venous stenosis needed balloon angioplasty. Primary and secondary patency rates at 6 months were 72.7% and 81.8%, and at 12 months, 54.5% and 72.7%, respectively. Postimplantation vascular access needs were met entirely by the graft in every instance and prevented the need for venous catheters. Fifty-six percent were accessed within 8 days, the earliest being 48 hours. Finally, all arterial punctures and 98% of venous punctures had sealed in less than 5 minutes, with two thirds sealing off within 3 minutes of needle withdrawal.

Conclusion

The electrospun polycarbonate-urethane graft is safe in humans, permits early access obviating the need for venous catheters, and has equivalent patency to other prosthetic grafts at 1 year.

Patency rate and complications of polytetrafluoroethylene grafts compared with polyurethane grafts for hemodialysis access

BACKGROUND

The survival of hemodialysis patients requiring dialysis depends on the long-term functioning and patency of the vascular access. Prosthetic vascular grafts are inevitably used for patients whose vessels are unsuitable for an autogenous arteriovenous (AV) fistula. The purpose of this study was to compare the patency rate and associated complications using different types of grafts.

METHODS

This prospective study was conducted on patients who did not have an appropriate vein for arteriovenous fistula from January 2004 through July 2006. They were divided into two groups, sex, age, and basic data matched. Polytetrafluoroethylene (PTFE) and polyurethane (PVAG) were the two types of grafts used in this study. The functionality of the graft was assessed immediately 1 day and 2 weeks after operation. The clinical follow-up was performed each 3 months until 24 months.

RESULTS

One-year patency rate was reported to be 64% and 52% in the PTFE and PVAG groups, respectively. There was no significant difference in 1-year (64% versus 52%) and 2-year (49% versus 41%) patency rate of the PTFE and PVAG grafts used as vascular access. There was also no difference between the numbers of complications reported in the two groups.

CONCLUSION

It could be concluded that either PTFE or PVAG grafts can be used with the same expected outcomes.

Primary Arteriovenous Fistulas in the Forearm for Hemodialysis: Effect of Miscellaneous Factors in Fistula Patency

BACKGROUND

The provision and maintenance of vascular access remains a major cost to end-stage renal failure programs. In addition, vascular access occlusion, results in significant morbidity in hemodialysis patients. Age, gender, diabetes mellitus, malignancy, smoking habits, administration of heparin per hemodialysis session, previous dialysis catheter insertion, number of hemodialysis sessions and location of the fistula may be associated with survival of the primary arteriovenous fistula. We examined the effects of various factors on fistulas in 412 chronic renal insufficiency patients.

METHODS

From 1995 to 2004, 412 arteriovenous fistulas were created by the Department of Cardiovascular Surgery at the Medical Faculty of Atatürk University for hemodialysis. The mean age of the patients was 45 years (range 6 to 62 years). We evaluated the effects of various factors for patency rates in the patients who had primary arteriovenous fistulas. Primary patency was defined as the duration of fistula patency without revision. Twenty-eight patients (6.7%) with ischemic cardiac disease did not require surgical interference. Analyzed data were age, gender, smoking habits, diabetes mellitus, malignant neoplasm, previous dialysis catheter insertion, number of hemodialysis sessions, and fistula location.

RESULTS

In 298 patients, where lower-arm radiocephalic fistulas were created, the fistula patency was 74.1%, 64.2%, 49.8%, 33.7%, and 4.1% after 1, 2, 3, 4, and 5 years, respectively, in the other 114 patients, where upper-arm fistulas were created, these rates were 84.0%, 72.2%, 53.3%, 39.8%, and 12.3%, respectively. There was no significantly difference between the upper-arm fistulas and the lower-arm fistulas statistically (p = 0.069). Factors affecting the primary patency of arteriovenous fistulas were diabetes mellitus (p = 0.0001), hemodialysis counts > or =3 per week (p < 0.0005), presence of malignancy (p < 0.0005), previous catheter insertion (p < 0.0007), and administration of heparin per hemodialysis session (p = 0.0008).

CONCLUSION

While primary arteriovenous fistula patency was shortened in chronic renal insufficiency patients with diabetes mellitus, presence of malignancy, and previous catheter insertion, patency was longer in patients with heparin used for hemodialysis and hemodialysis count per week (> or =3).

Conduits for hemodialysis access

The role of prosthetic arteriovenous (AV) access is still important in the management and care of the renal dialysis patients. Multiple new modalities are available to the surgeon today and it is imperative that their role be understood so that optimum care can be delivered to this complex group of patients. This article describes significant changes in prosthetic management and newer configurations available to the surgeon.