Use of a proactive duplex ultrasound protocol for hemodialysis access

Doppler ultrasound surveillance of recently formed haemodialysis arteriovenous fistula: the SONAR observational cohort study

Background

Arteriovenous fistulas are considered the best option for haemodialysis provision, but as many as 30% fail to mature or suffer early failure.

Objective

To assess the feasibility of performing a randomised controlled trial that examines whether, by informing early and effective salvage intervention of fistulas that would otherwise fail, Doppler ultrasound surveillance of developing arteriovenous fistulas improves longer-term arteriovenous fistula patency.

Design

A prospective multicentre observational cohort study (the 'SONAR' study).

Setting

Seventeen haemodialysis centres in the UK.

Participants

Consenting adults with end-stage renal disease who were scheduled to have an arteriovenous fistula created.

Intervention

Participants underwent Doppler ultrasound surveillance of their arteriovenous fistulas at 2, 4, 6 and 10 weeks after creation, with clinical teams blinded to the ultrasound surveillance findings.

Main outcome measures

Fistula maturation at week 10 defined according to ultrasound surveillance parameters of representative venous diameter and blood flow (wrist arteriovenous fistulas: ≥ 4 mm and > 400 ml/minute; elbow arteriovenous fistulas: ≥ 5 mm and > 500 ml/minute). Mixed multivariable logistic regression modelling of the early ultrasound scan data was used to predict arteriovenous fistula non-maturation by 10 weeks and fistula failure at 6 months.

Results

A total of 333 arteriovenous fistulas were created during the study window (47.7% wrist, 52.3% elbow). By 2 weeks, 37 (11.1%) arteriovenous fistulas had failed (thrombosed), but by 10 weeks, 219 of 333 (65.8%) of created arteriovenous fistulas had reached maturity (60.4% wrist, 67.2% elbow). Persistently lower flow rates and venous diameters were observed in those fistulas that did not mature. Models for arteriovenous fistulas' non-maturation could be optimally constructed using the week 4 scan data, with fistula venous diameter and flow rate the most significant variables in explaining wrist fistula maturity failure (positive predictive value 60.6%, 95% confidence interval 43.9% to 77.3%), whereas resistance index and flow rate were most significant for elbow arteriovenous fistulas (positive predictive value 66.7%, 95% confidence interval 48.9% to 84.4%). In contrast to non-maturation, both models predicted fistula maturation much more reliably [negative predictive values of 95.4% (95% confidence interval 91.0% to 99.8%) and 95.6% (95% confidence interval 91.8% to 99.4%) for wrist and elbow, respectively]. Additional follow-up and modelling on a subset (n = 192) of the original SONAR cohort (the SONAR-12M study) revealed the rates of primary, assisted primary and secondary patency arteriovenous fistulas at 6 months were 76.5, 80.7 and 83.3, respectively. Fistula vein size, flow rate and resistance index could identify primary patency failure at 6 months, with similar predictive power as for 10-week arteriovenous fistula maturity failure, but with wide confidence intervals for wrist (positive predictive value 72.7%, 95% confidence interval 46.4% to 99.0%) and elbow (positive predictive value 57.1%, 95% confidence interval 20.5% to 93.8%). These models, moreover, performed poorly at identifying assisted primary and secondary patency failure, likely because a subset of those arteriovenous fistulas identified on ultrasound surveillance as at risk underwent subsequent successful salvage intervention without recourse to early ultrasound data.

Conclusions

Although early ultrasound can predict fistula maturation and longer-term patency very effectively, it was only moderately good at identifying those fistulas likely to remain immature or to fail within 6 months. Allied to the better- than-expected fistula patency rates achieved (that are further improved by successful salvage), we estimate that a randomised controlled trial comparing early ultrasound-guided intervention against standard care would require at least 1300 fistulas and would achieve only minimal patient benefit.

Trial Registration

This trial is registered as ISRCTN36033877 and ISRCTN17399438.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR135572) and is published in full in Health Technology Assessment; Vol. 28, No. 24. See the NIHR Funding and Awards website for further award information.

ACR Appropriateness Criteria® Dialysis Fistula Malfunction

The creation and maintenance of a dialysis access is vital for the reduction of morbidity, mortality, and cost of treatment for end stage renal disease patients. One's longevity on dialysis is directly dependent upon the quality of dialysis. This quality hinges on the integrity and reliability of the access to the patient's vascular system. All methods of dialysis access will eventually result in dialysis dysfunction and failure. Arteriovenous access dysfunction includes 3 distinct classes of events, namely thrombotic flow-related complications or dysfunction, nonthrombotic flow-related complications or dysfunction, and infectious complications. The restoration of any form of arteriovenous access dysfunction may be supported by diagnostic imaging, clinical consultation, percutaneous interventional procedures, surgical management, or a combination of these methods. This document provides a rigorous evaluation of how variants of each form of dysfunction may be appraised and approached systematically. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Standardized Methodology for Duplex Ultrasound Examination of Arteriovenous Access for Hemodialysis: A Proposal of the French Society of Vascular Medicine and the French-Speaking Society of Vascular Access

Duplex ultrasound (DUS) is an essential tool for characterizing and monitoring arteriovenous (AV) access for hemodialysis. The aim of the work described here, requested by the French Society of Vascular Medicine in collaboration with the French-Speaking Vascular Access Society, is to propose a standardized methodology for performing and documenting DUS, taking into account the variety of AV access techniques and the problems routinely encountered. A steering committee reviewed the literature and selected the relevant references. A draft was prepared, and all items with missing or conflicting data were submitted to a Delphi consensus. The final document was discussed and approved by all participants. The principles of DUS evaluation of AV access consist of examination of the afferent artery, the anastomosis and the entire venous drainage system. DUS uses B-mode ultrasound, color flow, pulsed wave and power Doppler analysis. DUS can be used in a variety of clinical situations, which can directly influence the methodology of the examination and the interpretation of the results. Blood flow should be assessed as it correlates with the risk of thrombosis. The measurement should be adapted to the different anatomical and hemodynamic conditions encountered. Characterization of stenosis should take into account the residual diameter of the drainage vein and its hemodynamic consequences. Other complications can be assessed with a standardized DUS examination. When performed according to a rigorous methodology, DUS of the AV access allows a comprehensive assessment of its functionality and eliminates the need for further invasive diagnostic procedures.

Surgical creation of upper extremity arteriovenous fistula and grafts: a narrative review

Background and Objective

Surgical creation of arteriovenous fistulas (AVF) and grafts (AVG) continues to be the mainstay access for hemodialysis (HD). Avoidance of dependence on dialysis catheters continues to be a worldwide mission in dialysis access. Importantly, there is no one-size-fits-all approach to hemodialysis access and each patient should undergo access creation that is patient-centered. The aim of this paper is to review the literature, current guidelines, and discuss the common types of upper extremity hemodialysis access and their reported outcomes. We will also share our institutional experience regarding the surgical creation of upper extremity hemodialysis access.

Methods

The literature review incorporates twenty-seven relevant articles from 1997 to present and one case report series from 1966. Sources were gathered from electronic databases including PubMed, EMBASE, Medline, and Google Scholar. Only articles written in the English language were considered and study designs varied from current clinical guidelines, systematic and meta-analyses, randomized controlled trials, observational studies, and two main vascular surgery textbooks.

Key Content and Findings

This review exclusively focuses on the surgical creation of upper extremity hemodialysis accesses. Creating a graft versus fistula ultimately is decided by the existing anatomy, and is centered around the need of the patient. Preoperatively, the patient should undergo a thorough history and physical exam, with special attention to any previous central venous access, as well as, delineating the vascular anatomy with ultrasound imaging. The major tenets of access creation are choosing the most distal site of the non-dominant upper extremity whenever possible; and ideally creation of an autogenous access is preferred over a prosthetic graft. Described in this review are multiple surgical approaches for upper extremity hemodialysis access creation and associated institutional practices performed by the surgeon author. In the postoperative period, follow up care and surveillance are imperative to preserve a functioning access.

Conclusions

The most recent guidelines regarding hemodialysis access still favor arteriovenous fistula as the primary goal for patients with suitable anatomy. Preoperative evaluation including patient education, intraoperative ultrasound assessment, meticulous technique, and careful postoperative management are all paramount for successful access surgery. Dialysis access remains quite challenging, but with diligence the great majority of patients can be dialyzed without catheter dependence.

Arteriovenous fistula maturation: Physical exam versus flow study

PURPOSE

The purpose of this study was to determine the utility of routine duplex flow study 4 to 6 weeks after primary AVF creation and to compare physical exam against a duplex flow study in predicting fistula maturation. A surveillance algorithm was established to evaluate the naïve fistula after primary creation.

METHODS

This was a single institution retrospective review of 155 veterans with primary autogenous AVF creation from 2016 to 2018. All patients received a duplex flow study evaluation after primary creation. A comparison was made between physical exam (PE) and flow study at 4 to 6 weeks post creation. Sensitivities and specificities of physical exam and duplex flow study were compared head-to-head in predicting unassisted fistula maturation. A mature AVF was defined as a fistula that could be repetitively cannulated and provided adequate flow for dialysis. Failure of maturation was defined as an AVF that was never usable for dialysis. An abnormal duplex included thrombosis, stenosis (> 50% on gray scale imaging), inadequate vein diameter (< 4 mm), inadequate vein length or superficialization, or poor flow (< 500 ml/min). Bivariate comparisons were conducted using Pearson's χ², Fishers exact test, and Wilcoxon test depending on distribution. Significance was defined as P < 0.05.

RESULTS

There were 53 patients with radiocephalic (RC) fistulas, 41 patients with brachiocephalic (BC) fistulas, and 6 patients with brachiobasilic (BB) fistulas. Of patients with a confirmed abnormal duplex ultrasound, 53% had an abnormal PE (sensitivity 53%; PPV 96.3%, P < 0.001). Of the patients with a confirmed normal duplex, 98% had a normal PE (specificity 98%; NPV 68.5%, P < 0.001). An abnormal duplex flow study had a 67% sensitivity for predicting AVF failure or need for reintervention while an abnormal physical examination had a 42% sensitivity in predicting AVF failure or need for reintervention (P < 0.001). In total, 48 fistulas needed reintervention, however only 20 (42%) were associated with an abnormal physical examination. Of those 48 reinterventions, 20 (42%) fistulas exhibited primary assisted maturation (P < 0.001). On duplex flow study alone, 32 patients had hemodynamically significant lesions necessitating reintervention, which went on to afford 9 (28%) primary assisted mature fistulas (P = 0.69).

CONCLUSION

Abnormal duplex flow studies have a better sensitivity for detecting AVF failure or the need for reintervention compared to physical exam alone. An abnormal duplex correlates more with needing a reintervention to achieve maturation than physical exam. Therefore, we advocate routine use of a postoperative duplex flow study to identify potentially correctable issues and optimize fistula maturation.

Arteriovenous Fistula Surveillance Using Tomographic 3D Ultrasound

OBJECTIVE

A well functioning arteriovenous fistula (AVF) is essential for haemodialysis. Despite regular duplex ultrasound (DUS) a significant number of AVFs fail. Tomographic 3D ultrasound (tUS) creates a 3D image of the AVF that can be interpreted by the clinician. DUS, tUS, and fistulograms were compared for the identification and measurement of flow limiting stenosis.

METHODS

Patients with AVF dysfunction on routine Transonic surveillance, defined as (1) > 15% reduction in flow on two consecutive occasions, (2) > 30% reduction in flow on one occasion, (3) flow of < 600 mL/sec, (4) presence of recirculation, underwent DUS. AVF tUS imaging was performed prior to fistulography. All fistulograms were reported by the same consultant radiologist and tUS images by the same vascular scientist blinded to the fistulogram results. Maximum diameter reduction in all stenoses were measured using all three imaging techniques.

RESULTS

In 97 patients with 101 stenoses, the mean (± standard deviation [SD]) severity of stenosis was 63.0 ± 13.9%, 65.0 ± 11.6%, and 64.8 ± 11.7% for the fistulograms, DUS, and tUS respectively. The mean (± SD) time between ultrasound and fistulography imaging was 15.0 ± 14.5 days. Assuming the fistulogram as the "gold standard", Bland-Altman agreement for DUS was -1.9 ± 15.5% (limit of agreement [LOA] -32.2 - 28.4) compared with -1.7 ± 15.4% (LOA -31.9 - 28.4) for tUS. Median (± interquartile range) time to complete the investigation was 09:00 ± 03:19 minutes for DUS and 03:13 ± 01:56 minutes for tUS (p < .001).

CONCLUSION

DUS and tUS were equally accurate at detecting AVF complications but tUS investigation requires less skill and was significantly quicker than DUS.

The influence of a doppler ultrasound in arteriovenous fistula for dialysis failure related to some risk factors

INTRODUCTION

The increasing prevalence of chronic kidney disease has increased the demand for arteriovenous fistula (AVF) care. The objective of this study was to assess the relationship between some risk factors for AVF failure (advanced age, female sex, diabetes, obesity, central venous catheter, previous fistula, and hospitalization) and having a Doppler ultrasound performed preoperatively.

METHODS

A prospective study was performed with 228 dialysis patients from Imperatriz, Maranhão. Half of the sample was randomly selected to receive preoperative Doppler ultrasound and the other half did not, from the period of October 2016 to September 2018.

RESULTS

There were 53 total failures corresponding to 23.2% of our sample, which is almost double that of the patients in the clinical group. Considering the failures and risk factors associated with the overall sample, there was a statistically significant association between a central venous catheter on the same side of the AVF with P = 0.04 (Odds Ratio 1.24) and obesity with P = 0.05 (Odds Ratio 1.36), which was not repeated in the Doppler ultrasound group individually. There was no statistically significant difference between the Doppler group and clinical group with respect to the amount of days of previous AVF hospitalization and failure.

CONCLUSIONS

We concluded that the reduction of failures with an introduction of the Doppler was statistically significant in the overall sample, but establishing a relationship between specific risk factors and failure was only possible with two of the risk factors in the study - obesity and central venous catheter on the same side of the AVF.

Outcomes of post-operative duplex ultrasound following arteriovenous fistula formation: A pragmatic single-centre experience

BACKGROUND

Duplex ultrasound surveillance with pre-emptive treatment of an identified stenosis is increasingly being utilised to help maintain arteriovenous fistula patency. This study aims to determine whether post-operative duplex ultrasound surveillance can improve fistula patency at 12 months and improve the proportion of 'pre-haemodialysis' patients commencing haemodialysis via a usable fistula.

METHODS

All arteriovenous fistulae formed between 1st January 2015 and 31st August 2017 in a single, tertiary vascular centre were included. Primary and secondary patency at 12 months, along with the proportion of pre-haemodialysis patients commencing haemodialysis via a usable arteriovenous fistula, were compared between the fistulae undergoing duplex ultrasound surveillance and 'standard practice'.

RESULTS

Two hundred forty-one arteriovenous fistulae were created in 216 patients. A higher proportion of brachiobasilic transposition arteriovenous fistula and patients undergoing arteriovenous fistula creation following a previously failed access were identified in the duplex ultrasound surveillance group. Primary patency at 12 months (hazard ratio = 0.43, 95% confidence interval = 0.30-0.61, p < .001) was significantly lower in the duplex ultrasound surveillance group compared with the 'standard practice' group. Despite this, no difference was identified in secondary patency at 12 months (hazard ratio = 1.82, 95% confidence interval = 0.87-3.80, p = .112). No difference was also identified in the proportion of pre-haemodialysis patients starting haemodialysis with a usable arteriovenous fistula (duplex ultrasound surveillance = 65.0% vs standard practice = 77.8%; odds ratio = 0.53, 95% confidence interval 0.58-1.19, p = .279).

CONCLUSION

Post-operative duplex ultrasound surveillance following arteriovenous fistula formation is associated with higher rates of post-operative intervention; however, this does not translate into improved secondary patency or the proportion of pre-haemodialysis patients commencing HD via their fistula.

Surveillance arterioveNous fistulAs using ultRasound (SONAR) trial in haemodialysis patients: a study protocol for a multicentre observational study

INTRODUCTION

Arteriovenous fistulas (AVFs) are considered the best and safest modality for providing haemodialysis in patients with end-stage renal disease. Only 20% of UK centres achieve the recommended 80% target for achieving dialysis of the prevalent dialysis population via permanent access (as opposed to a central venous catheter). This is partly due to the relatively poor maturation rate of newly created fistulas, with as many as 50% of fistulas failing to mature.The Surveillance Of arterioveNous fistulAe using ultRasound study will examine whether a protocolised programme of Doppler ultrasound (US) surveillance can identify, early after creation, potentially correctable problems in those AVFs that subsequently fail to mature.

METHODS AND ANALYSIS

This is a multicentre observational study that will assess newly created AVFs by Doppler US performed at 2, 4, 6 and 10 weeks after creation. The primary outcome measure will be primary fistula patency at week 10. Secondary outcome measures include: successful use of the fistula; clinical suitability for dialysis; creation of new fistula or radiological salvage; fistula thrombosis; secondary fistula patency rate and patient acceptability.

ETHICS AND DISSEMINATION

The study has been approved by the Cambridgeshire and Hertfordshire Research Ethics Committee and by the Health Research Authority (REC 18/EE/0234). The results generated from this work will be published as open access, within 3 years of trial commencement. We will also present our findings at key national/international renal meetings, as well as support volunteers at renal patient groups to disseminate the trial outcome.

TRIAL REGISTRATION NUMBER

ISRCTN36033877.

Inter-observer agreement of color duplex ultrasound of central vein stenosis in hemodialysis patients

Purpose

To assess the inter-observer agreement of color duplex ultrasound of central vein stenosis in hemodialysis patients.

Patients and methods

This prospective study was conducted on 35 hemodialysis patients with suspected central vein stenosis. All patients underwent color flow duplex examination of the subclavian, internal jugular and brachiocephalic veins in hemodialysis patients. Image analysis was performed by two reviewers for diameter reduction, peak venous velocity ratio, post-stenotic turbulent flow, waveform changes, and thrombus formation.

Results

There was no significant difference between both observers for diameter reduction ( p = 0.105) and for the mean peak systolic velocity ratio ( p = 0.515). The overall inter-observer agreement of color duplex ultrasound of central vein stenosis was excellent ( k = 0.84, percent agreement = 89.7%, P = 0.001). There was excellent inter-observer agreement of both reviewers for diameter reduction ( k = 0.928, percent agreement = 97.14%), peak venous velocity ratio ( k = 0.7, percent agreement = 85.7%), waveform changes ( k = 0.62, percent agreement = 77.14%), post-stenotic turbulent flow ( k = 0.866, percent agreement = 88.6%), thrombus formation ( k = 1, percent agreement = 100%).

Conclusion

We concluded that color duplex ultrasound is a reliable and reproducible method for diagnosis of central vein stenosis in hemodialysis patients.

A Methodology for Non-Invasive 3-D Surveillance of Arteriovenous Fistulae Using Freehand Ultrasound

OBJECTIVE

Surveillance techniques for arteriovenous fistulae are required to maintain functional vascular access, with two-dimensional duplex ultrasound the most widely used imaging modality. This paper presents a surveillance method for an arteriovenous fistula using a freehand three-dimensional (3-D) ultrasound system. A patient-case study highlights the applicability in a clinical environment.

METHODS

The freehand ultrasound system uses optical tracking to determine the vascular probe location, and as the probe is swept down a patient's arm, each B-mode slice is spatially arranged to be post-processed as a volume. The volume is segmented to obtain the 3-D vasculature for high detail analysis.

RESULTS

The results follow a patient with stenosis, undergoing surgery to have a stent placement. A surveillance scan was taken pre-surgery, postsurgery, and at a two-month follow-up. Vasculature changes are quantified using detailed analysis, and the benefits of using 3-D imaging are shown through 3-D printing and visualization.

CONCLUSION AND SIGNIFICANCE

Non-invasive 3-D surveillance of arteriovenous fistulae is possible, and a patient-specific geometry was created using ultrasound and optical tracking. Access to this non-invasive 3-D surveillance technique will enable future studies to determine patient-specific remodeling behavior, in terms of geometry and hemodynamics over time.

Sonography of Arteriovenous Fistulas and Grafts

Arteriovenous fistulas (AVFs) and arteriovenous grafts (AVGs) are the vascular accesses of choice for long-term hemodialysis. Strategies to establish and maintain functioning AVFs and AVGs are essential. In addition to clinical evaluation, ultrasound plays a critical role in the evaluation and maintenance of AVFs and AVGs. AVFs have a high rate of failure to mature which can be reliably diagnosed with ultrasound. Treatable etiologies of the failure to mature can often be diagnosed with ultrasound. Causes of secondary AVG failure can also be diagnosed with ultrasound and treated. AVGs have a relatively short functional life expectancy due to a high rate of AVG thrombosis. Ultrasound is a safe, noninvasive way to diagnose vascular stenosis in both AVFs and AVGs prior to thrombosis, potentially saving the access. Routine surveillance ultrasound of asymptomatic AVFs and AVGs is controversial with conflicting studies on its benefit. Routine surveillance ultrasound of AVFs and AVGs is not common practice.