Future research directions to improve fistula maturation and reduce access failure

With the increasing prevalence of end stage renal disease there is a growing need for hemodialysis. Arteriovenous fistulae (AVF) are the preferred type of vascular access for hemodialysis but maturation and failure continue to present significant barriers to successful fistula use. AVF maturation integrates outward remodeling with vessel wall thickening in response to drastic hemodynamic changes, in the setting of uremia, systemic inflammation, oxidative stress and preexistent vascular pathology. AVF can fail due to both failure to mature adequately to support hemodialysis, as well as development of neointimal hyperplasia (NIH) that narrows the AVF lumen, typically near the fistula anastomosis. Failure due to NIH involves vascular cell activation and migration and extracellular matrix remodeling with complex interactions of growth factors, adhesion molecules, inflammatory mediators, and chemokines, all of which result in maladaptive remodeling. Different strategies have been proposed to prevent and treat AVF failure, based on current understanding of the modes and pathology of access failure; these approaches range from appropriate patient selection and use of alternative surgical strategies for fistula creation, to the use of novel interventional techniques or drugs to treat failing fistulae. Effective treatments to prevent or treat AVF failure requires a multidisciplinary approach involving nephrologists, vascular surgeons and interventional radiologists, allowing careful patient selection and the use of tailored systemic or localized interventions to improve patient-specific outcomes. This review provides contemporary information on the underlying mechanisms of AVF maturation and failure and discusses the broad spectrum of options that can be tailored for specific therapy

Brachial vein transposition arteriovenous fistulas for hemodialysis access

BackgroundAn arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis, offering lower morbidity, mortality, and cost compared with grafts or catheters. Patients with a difficult access extremity have often lost all superficial veins, and even basilic veins may be obliterated. We have used brachial vein transposition AVFs (BVT-AVFs) in these challenging patients and review our experience in this report.MethodsThe study reviewed consecutive patients in whom BVT-AVFs were created from September 2006 to March 2009. Most BVT-AVFs were created in staged procedures, with the second-stage transposition operations completed 4 to 6 weeks after the first-stage AVF operation. A single-stage BVT-AVF was created when the brachial vein diameter was ≥6 mm.ResultsWe identified 58 BVT-AVF procedures, comprising 41 women (71.0%), 28 diabetic patients (48.3%), and 29 (50.0%) had previous access surgery. The operation was completed in two stages in 45 operations (77.6%) and was a primary transposition in 13 patients. However, five of these were secondary AVFs with previous distal AV grafts or AVFs placed elsewhere; effectively, late staged procedures. Follow-up was a mean of 11 months (range, 2.0-31.7 months). Primary patency, primary-assisted patency, and cumulative (secondary) patency were 52.0%, 84.9%, and 92.4% at 12 months and 46.2%, 75.5%, and 92.4% at 24 months, respectively. Harvesting the brachial vein was tedious and more difficult than harvesting other superficial veins. No prosthetic grafts were used.ConclusionBVT-AVFs provide a suitable option for autogenous access when the basilic vein is absent in patients with difficult access extremities. Most patients required intervention for access maturation or maintenance. Most BVT-AVFs were created with staged procedures. Cumulative (secondary) patency was 92.4% at 24 months

Hemodialysis Access: Initial Considerations and the Difficult Patient

The population requiring hemodialysis (HD) in the United States continues to grow, with recent studies reporting over 370,000 Americans with end stage renal disease (ESRD) who are HD-dependent. The creation of functional HD access is often the limiting step in utilization of renal replacement therapy (RRT). Since the 1960s, the creation of hemodialysis access has become one of the most commonly performed procedures in the United States with over 500,000 vascular access procedures performed per year. This represents approximately 8% of the annual Medicare budget allocated to patients with ESRD. The magnitude of the associated economic and human costs is further exemplified by the fact that up to 25% of patients with ESRD will die due to inadequate hemodialysis access. This clinical situation and societal burden makes understanding the basic management steps and options for hemodialysis access of key importance to all healthcare professionals involved in the care of patients who require HD

Ultrasound evaluation of access complications: Thrombosis, aneurysms, pseudoaneurysms and infections

: Arteriovenous fistula (AVF) complications are classified based on fistula outcomes. This review aims to update colour Doppler (CD) and pulse wave Doppler (PWD) roles in managing early and late complications of the native and prosthetic AVF. Vascular access (VA) failure occurs because inflow or outflow stenosis activates Wirchow's triad inducing thrombosis. Therefore, the diagnosis of the tributary artery and outgoing vein stenosis will be the first topic considered. Post-implantation complications occur from the inability to achieve AVF maturation and dialysis suitability due to inflow/outflow stenosis. Late stenosis is usually a sequence of early defects repaired to maintain patency. Less frequently, in the mature AVF or graft, complications are acquired 'de novo'. They derive either from incorrect management of vascular access (haematoma, pseudoaneurysm, prosthesis infection) or wall pathologies (aneurysm, myxoid valve degeneration, kinking, coiling, abnormal dilation from defects of elastic structures). High-resolution transducers (10-20 MHz) allow the characterization of the wall damage, haemodynamic dysfunctions, early and late complications even if phlebography remains the gold standard for the diagnosis for its sensitivity and specificity

Diagnostic accuracy of Color Doppler Ultrasound in determining arteriovenous fistula stenosis

Objective: To determine the diagnostic accuracy of color Doppler ultrasound in determining arteriovenous fistula stenosis.Methodology: A descriptive, Cross-sectional study was conducted at Radiology Department, Jinnah Hospital, Lahore from November 2014 to March 2016. A total 105 patients with 20-70 years of age having recent mature fistulas of more than 12 weeks were included. Patients with acute hemodialysis, receiving hemodialysis through AV graft and hemodynamically unstable patients were excluded. All the patients underwent blood flow and luminal diameter measurement of AV fistula by color Doppler ultrasound. After this, Digital Subtraction Angiography (DSA) was performed and results of Color Doppler Ultrasound (CDS) were correlated with DSA which was taken as the gold standard. Linear regression was used for analysis. P and r2 values calculated for each of these.Results: Mean age of the patients was 42.08 ± 11.90 years. Out of these 105 patients, 73 (69.52%) were males and 32 (30.48%) were females with a ratio of 2.28:1. CDS detected AVF stenosis in 64 (60.95%) patients, out of which, 58 were True Positive and 06 were False Positive. Among 41 CDS negative patients, 30 were False Negative and 11 were True Negative. Overall sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CDS for the detection of AVF stenosis, taking DSA as the gold standard was 84.06%, 83.33%, 90.62%, 73.17%, and 83.81% respectively. Conclusion: Color Doppler ultrasonography is a highly sensitive and accurate non-invasive modality for detecting AVF stenosis, and should be used routinely in order to reduce invasive digital subtraction angiography

Long-term functional patency and cost-effectiveness of arteriovenous fistula creation under regional anesthesia: a randomized controlled trial

BACKGROUND:Regional anesthesia improves short-term blood flow through arteriovenous fistulas (AVFs). We previously demonstrated that, compared with local anesthesia, regional anesthesia improves primary AVF patency at 3 months. METHODS:To study the effects of regional versus local anesthesia on longer-term AVF patency, we performed an observer-blinded randomized controlled trial at three university hospitals in Glasgow, United Kingdom. We randomly assigned 126 patients undergoing primary radiocephalic or brachiocephalic AVF creation to receive regional anesthesia (brachial plexus block; 0.5% L-bupivacaine and 1.5% lidocaine with epinephrine) or local anesthesia (0.5% L-bupivacaine and 1% lidocaine). This report includes findings on primary, functional, and secondary patency at 12 months; reinterventions; and additional access procedures (primary outcome measures were previously reported). We analyzed data by intention to treat, and also performed cost-effectiveness analyses. RESULTS:At 12 months, we found higher primary patency among patients receiving regional versus local anesthesia (50 of 63 [79%] versus 37 of 63 [59%] patients; odds ratio [OR], 2.7; 95% confidence interval [95% CI], 1.6 to 3.8; P=0.02) as well as higher functional patency (43 of 63 [68%] versus 31 of 63 [49%] patients; OR, 2.1; 95% CI, 1.5 to 2.7; P=0.008). In 12 months, 21 revisional procedures, 53 new AVFs, and 50 temporary dialysis catheters were required. Regional anesthesia resulted in net savings of £195.10 (US$237.36) per patient at 1 year, and an incremental cost-effectiveness ratio of approximately £12,900 (US$15,694.20) per quality-adjusted life years over a 5-year time horizon. Results were robust after extensive sensitivity and scenario analyses. CONCLUSIONS:Compared with local anesthesia, regional anesthesia significantly improved both primary and functional AVF patency at 1 year and is cost-effective. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER:Local Anaesthesia versus Regional Block for Arteriovenous Fistulae, NCT01706354

The Optimisation of Arteriovenous Fistula Vascular Access Outcomes for Haemodialysis

End Stage Renal Failure, requiring renal replacement therapy, is delivered most commonly via haemodialysis (HD). The gold standard Vascular Access (VA) for HD is the arteriovenous fistula (AVF). However, it can be difficult to establish and maintain a mature AVF. A comprehensive vascular access service model was established with the aim of streamlining AVF care, allowing for the introduction of innovative solutions (over the subsequent years) to AVF pathologies and close observation of AVF experimental outcomes. This service resulted in an improvement in multiple VA outcomes and a reduction in VA expenditure. Innovative solutions focused on improving the reliability of the AVF through addressing known inflow, cannulation zone and outflow AVF pathologies were developed. We implanted an interwoven nitinol stent to approximate the optimal fluid dynamic geometry to treat stenoses of the inflow juxta-anastomosis (JXAS). We found acceptable patency results with no loss of AVFs in the long term results. A dynamic banding (DYBAND) technique was developed to treat excessive AVF inflow, allowing for band adjustment in concert with flow rate measurement, thus achieving the optimal band diameter for every individual AVF. The dysfunctional cannulation zone was addressed with cannulation zone stenting, allowing immediate puncture for dialysis. In a multi-centre study, we found acceptable outcomes and patency of AVFs to 4 years follow up, with a low rate of re-intervention. A pilot study with drug eluting stents in the AVF cannulation zone was performed to improve patency results. Whilst we were able to determine acceptable patency results, cessation of dual antiplatelet therapy in the medium-term post implantation was associated with stent thrombosis, hence limiting widespread adoption. During the study, a meta-analysis (Katsanos et al), determined a significant mortality risk associated with a commonly applied AVF first line therapy, drug eluting balloons (DEB). We performed a meta-analysis and demonstrated no such effect was present in AVF patients receiving a DEB. With increasing confidence from the aforementioned therapies, we combined these treatments as an adjuvant to AVF formation. The study demonstrated that timely, near universal AVF maturation was achieved, with all AVFs maintained utilising a low rate of re-intervention. The methods and results presented in this thesis demonstrates that for incident dialysis dependency, under the supervision of an RVAC, patients can have an AVF formed, matured and maintained for long term access