Hemodialysis arteriovenous fistula maturity: US evaluation

Ultrasound Measurement of Vascular Distensibility Based on Edge Detection and Speckle Tracking Using Ultrasound DICOM Data

This study presents an edge detection and speckle tracking (EDST) based algorithm to calculate distensibility as percentage of change of vessel diameter during cardiac cycles. Canny edge detector, Vandermonde matrix representation, Kanade Lucas Tomasi algorithm with pyramidal segmentation, and penalized least squares technique identifies the vessel lumen edge, track the vessel diameter, detrend the signal and find peaks and valleys when the vessel is fully distended or contracted. An upper extremity artery from 10 patients underwent an ultrasound examination as part of preoperative evaluation before arteriovenous fistula surgery. Three studies were performed to evaluate EDST with automatic peak and valley selection versus manual speckle selection of expert users using manual peak and valley selection. Results demonstrate the effectiveness of the proposed methodology, to obtain comparable results as those obtained by expert-users, and considerably reducing the variability associated with external factors such as excessive motion, fluctuations in stroke volume, beat-to-beat blood pressure changes, breathing cycles, and arm-transducer pressure.

Nitric oxide releasing nanomatrix gel treatment inhibits venous intimal hyperplasia and improves vascular remodeling in a rodent arteriovenous fistula

Vascular access is the lifeline for hemodialysis patients and the single most important component of the hemodialysis procedure. Arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis patients, but nearly 60% of AVFs created fail to successfully mature due to early intimal hyperplasia development and poor outward remodeling. There are currently no therapies available to prevent AVF maturation failure. First, we showed the important regulatory role of nitric oxide (NO) on AVF development by demonstrating that intimal hyperplasia development was reduced in an overexpressed endothelial nitric oxide synthase (NOS3) mouse AVF model. This supported the rationale for the potential application of NO to the AVF. Thus, we developed a self-assembled NO releasing nanomatrix gel and applied it perivascularly at the arteriovenous anastomosis immediately following rat AVF creation to investigate its therapeutic effect on AVF development. We demonstrated that the NO releasing nanomatrix gel inhibited intimal hyperplasia formation (more than 70% reduction), as well as improved vascular outward remodeling (increased vein diameter) and hemodynamic adaptation (lower wall shear stress approaching the preoperative level and less vorticity). Therefore, direct application of the NO releasing nanomatrix gel to the AVF anastomosis immediately following AVF creation may enhance AVF development, thereby providing long-term and durable vascular access for hemodialysis.

Rationale and Trial Design of MesEnchymal Stem Cell Trial in Preventing Venous Stenosis of Hemodialysis Vascular Access Arteriovenous Fistula (MEST AVF Trial)

Background

Hemodialysis arteriovenous fistulas (AVFs) are the preferred vascular access for patients on hemodialysis. In the Hemodialysis Fistula Maturation Study, 44% of the patients achieved unassisted maturation of their fistula without needing an intervention. Venous neointimal hyperplasia (VNH) and subsequent venous stenosis are responsible for lack of maturation. There are no therapies that can prevent VNH/VS formation. The goal of this paper is to present the background, rationale, and trial design of an innovative phase 1/2 clinical study that is investigating the safety of autologous adipose-derived mesenchymal stem cells delivered locally to the adventitia of newly created upper extremity radiocephalic (RCF) or brachiocephalic fistula (BCF).

Methods

The rationale and preclinical studies used to obtain a physician-sponsored investigational new drug trial are discussed. The trial design and end points are discussed.

Results

This is an ongoing trial that will complete this year.

Conclusion

This is a phase 1/2 single-center, randomized trial that will investigate the safety and efficacy of autologous AMSCs in promoting maturation in new upper-extremity AVFs.Clinical Trial registration number: NCT02808208.

Anaesthesia Choice for Creation of Arteriovenous Fistula (ACCess) study protocol : a randomised controlled trial comparing primary unassisted patency at 1 year of primary arteriovenous fistulae created under regional compared to local anaesthesia

INTRODUCTION

Arteriovenous fistulae (AVF) are the 'gold standard' vascular access for haemodialysis. Universal usage is limited, however, by a high early failure rate. Several small, single-centre studies have demonstrated better early patency rates for AVF created under regional anaesthesia (RA) compared with local anaesthesia (LA). The mechanistic hypothesis is that the sympathetic blockade associated with RA causes vasodilatation and increased blood flow through the new AVF. Despite this, considerable variation in practice exists in the UK. A high-quality, adequately powered, multicentre randomised controlled trial (RCT) is required to definitively inform practice.

METHODS AND ANALYSIS

The Anaesthesia Choice for Creation of Arteriovenous Fistula (ACCess) study is a multicentre, observer-blinded RCT comparing primary radiocephalic/brachiocephalic AVF created under regional versus LA. The primary outcome is primary unassisted AVF patency at 1 year. Access-specific (eg, stenosis/thrombosis), patient-specific (including health-related quality of life) and safety secondary outcomes will be evaluated. Health economic analysis will also be undertaken.

ETHICS AND DISSEMINATION

The ACCess study has been approved by the West of Scotland Research and ethics committee number 3 (20/WS/0178). Results will be published in open-access peer-reviewed journals within 12 months of completion of the trial. We will also present our findings at key national and international renal and anaesthetic meetings, and support dissemination of trial outcomes via renal patient groups.

TRIAL REGISTRATION NUMBER

ISRCTN14153938.

SPONSOR

NHS Greater Glasgow and Clyde GN19RE456, Protocol V.1.3 (8 May 2021), REC/IRAS ID: 290482.

Evaluation of Factors Affecting Wrist Radio-Cephalic Arteriovenous Fistula Maturation: A Single Institutional Observational Study

Background: Chronic renal failure is the most common indication for which arterio-venous (AV) fistula creation surgery is being performed. Various studies have found that native arteriovenous fistulas are the best in long-term patency with lower complications. We conducted this study to find out the role of preprocedural duplex ultrasound (DUS) in predicting outcomes of radio-cephalic fistula in the wrist in the North-Karnataka population. Methods: This prospective study was conducted from May 2019 to July 2020 on 50 patients who were hemodialysis-dependent and underwent AV fistula creation with age from 20 to 70 years. All the patients underwent preoperative DUS and were followed up post-operatively after one, two, and six weeks. Hemodialysis was initiated through the constructed fistula once it was mature, and the maximum blood flow through the fistula was measured. SPSS version 20.0 was used for statistical analysis. Results: Among 50 subjects, the overall cumulative success of AVF maturation was 86% (43), and failure to mature rate was 14% (7). Logistic regression of maturation outcome in the wrist autologous arteriovenous fistula for individual factors showed statistically significant results (P < 0.05) for the diameter of the radial artery > 1.6 mm and the distensibility of the cephalic vein > 0.4 mm. Conclusions: Vein distensibility and radial artery diameter are key factors in predicting successful AVF maturation. The use of intraoperative papaverine instillation directly on vessels can improve arteriovenous fistula outcomes.

Maturation and survival of arteriovenous fistula: The challenge starts from the preoperative assessment stage

BACKGROUND

It is necessary to assess the association between the preoperative indicators and the maturation and survival of arteriovenous fistula (AVF).

METHODS

We retrospectively identified 236 patients with a new AVF created between 2016 and 2018 in our Dialysis Center.

RESULTS

Multivariate Logistic regression showed that preoperative arterial diameter (odds ratio [OR] = 1.452, 95% confidence interval [CI] [1.233, 1.710], p < 0.001), preoperative venous diameter (OR = 1.296, 95% CI [1.166, 1.477], p < 0.001), left ventricular ejection fraction (LVEF) (OR = 1.187, 95% CI [1.103, 1.277], p < 0.001), and diabetes mellitus (OR = 0.245, 95% CI [0.107, 0.560], p = 0.01) were independent influential factors for AVF maturation. Two years after the AVF surgery follow-up, multivariate Cox proportional-hazards model showed that the preoperative arterial diameter (OR = 0.510, 95% CI [0.320, 0.813], p = 0.005), preoperative venous diameter (OR = 0.940, 95% CI [0.897, 0.985], p = 0.010) and diabetes mellitus (OR = 1.785, 95% CI [1.117, 2.855], p = 0.016) was prognostic factors of AVF survival. The Kaplan-Meier method showed that the primary survival of AVF in patients with different preoperative arterial diameter was statistically significant (log-rank χ²  = 15.415, p < 0.001), while the secondary survival was not statistically significant (log-rank χ²  = 0.131, p = 0.717).

CONCLUSION

In our cohort, the preoperative arterial and venous diameter and diabetes mellitus were independent influential factors for AVF maturation and prognostic factors of AVF survival. However, the preoperative LVEF only associated with the maturation of AVF. Meanwhile, smaller arterial diameter (≤2.15 mm) was associated with AVF maturation failure, but did not impact secondary survival of AVF.

Basics for performing a high-quality color Doppler sonography of the vascular access

In the last years, the systematic use of ultrasound mapping of the upper limb vascular network before the arteriovenous fistula (AVF) implantation, access maturation, and clinical management of late complications is widespread and expanding. Therefore, a good knowledge of theoretical outlines, instrumentation, and operative settings is undoubtedly required for a thorough examination. In this review, the essential Doppler parameters, B-Mode setting, and Doppler applications are considered. Basic concepts on the Doppler shift equation, angle correction, settings on pulse repetition frequency, operative Doppler frequency, gain are reported to ensure adequate and correct sampling of blood flow velocity. A brief analysis of the Doppler inherent artefacts (as random noise, blooming, aliasing, and motion artefacts) and the adjustment setting to minimize or eliminate the confounding artefacts are also considered. Doppler aliasing occurs when the pulse repetition frequency is set too low. This artefact is particularly frequent in vascular access sampling due to the high velocities range registered in the fistula's different segments. Aliasing should be recognized because its correction is crucial to analyse the Doppler signals correctly. Recent advances in instrumentation are also considered about a potential purchase of a portable ultrasound machine or a top-of-line, high-end, or mid-range ultrasound system. Last, the pulse wave Doppler setting for vascular access B-Mode and Doppler assessment is summarized.

Percutaneous Arteriovenous Fistula Creation with the 4 French WavelinQ™ EndoAVF System

BACKGROUND

Percutaneous devices for creation of native arteriovenous fistulae offer an alternative to traditional open surgical techniques. The 4 Fr WavelinQ EndoAVF System was developed as a lower profile alternative to facilitate access through smaller vessels and minimize access site complications; The current report is the original first experience of this device, assessing outcome in 120 patients followed for 6 months.

METHODS

The use of the 4 Fr WavelinQ system in three studies, EASE (32 patients), EASE-2 (24 patients), and the EU post-market clinical follow-up study (64 patients) was aggregated and analyzed. Patients were followed with duplex ultrasound at discharge and follow-up visits at 1, 3, and 6 months. Primary, assisted primary, and secondary patency rates were evaluated as Kaplan-Meier (KM) estimates and standard errors. Time to maturity and time to successful cannulation were defined as the mean ± SD days from the procedure in patients enrolled on dialysis.

RESULTS

Procedural success was achieved in 116 patients (96.7%). Primary, assisted-primary, and secondary 6-month patency rates were 71.9%±4.5%, 80.7%±4.1%, and 87.8%±3.3%, respectively. Time to maturity averaged 41±17 days. Time to successful cannulation averaged 68±51 days. Device-related serious adverse events were reported in 3/120 patients (2.5%) and procedure-related serious adverse events occurred in 7/120 patients (5.8%). Arterial or venous access complications were not reported in any of the patients. Access circuit reinterventions were performed in 23 patients (19.2%), split between those performed for EndoAVF maturation (13/120, 10.8%) and maintenance (11/120. 9.2%).

CONCLUSIONS

Percutaneous creation of native dialysis fistulae with the 4 Fr WavelinQ EndoAVF System is safe and effective, with favorable durability and a low rate of serious complications and reinterventions through 6-month follow-up. Utilization of the 4F device allows for percutaneous fistula creation between the radial artery and radial vein or the ulnar artery and ulnar vein. These findings suggest that the 4 Fr device is a useful percutaneous alternative to open surgical AVF or endovascular AVF with larger-bore devices.

Arteriovenous Fistula-induced Cardiac Remodeling Shows Cardioprotective Features in Mice

Objective

Arteriovenous fistulae (AVF) placed for hemodialysis have high flow rates that can stimulate left ventricular (LV) hypertrophy. LV hypertrophy generally portends poor cardiac outcomes, yet clinical studies point to superior cardiac-specific outcomes for patients with AVF when compared with other dialysis modalities. We hypothesize that AVF induce physiologic cardiac hypertrophy with cardioprotective features.

Methods

We treated 9- to 11-week-old C57Bl/6 male and female mice with sham laparotomy or an aortocaval fistula via a 25G needle. Cardiac chamber size and function were assessed with serial echocardiography, and cardiac computed tomography angiography. Hearts were harvested at 5 weeks postoperatively, and the collagen content was assessed with Masson's trichrome. Bulk messenger RNA sequencing was performed from LV of sham and AVF mice at 10 days. Differentially expressed genes were analyzed using Ingenuity Pathway Analysis (Qiagen) to identify affected pathways and predict downstream biological effects.

Results

Mice with AVF had similar body weight and wet lung mass, but increased cardiac mass compared with sham-operated mice. AVF increased cardiac output while preserving LV systolic and diastolic function, as well as indices of right heart function; all four cardiac chambers were enlarged, with a slight decrement in the relative LV wall thickness. Histology showed preserved collagen density within each of the four chambers without areas of fibrosis. RNA sequencing captured 19 384 genes, of which 857 were significantly differentially expressed, including transcripts from extracellular matrix-related genes, ion channels, metabolism, and cardiac fetal genes. The top upstream regulatory molecules predicted include activation of angiogenic (Vegf, Akt1), procardiomyocyte survival (Hgf, Foxm1, Erbb2, Lin9, Areg), and inflammation-related (CSF2, Tgfb1, TNF, Ifng, Ccr2, IL6) genes, as well as the inactivation of cardiomyocyte antiproliferative factors (Cdkn1a, FoxO3, α-catenin). The predicted downstream effects include a decrease in heart damage, and increased arrhythmia, angiogenesis, and cardiogenesis. There were no significant sex-dependent differences in the AVF-stimulated cardiac adaptation.

Conclusions

AVF stimulate adaptive cardiac hypertrophy in wild-type mice without heart failure or pathologic fibrosis. Transcriptional correlates suggest AVF-induced cardiac remodeling has some cardioprotective, although also arrhythmogenic features. (JVS–Vascular Science 2021;2:110-28.)

Clinical Relevance

Arteriovenous fistulae (AVF) are commonly used as access for hemodialysis in patients with end-stage renal disease. AVF induce a high-output state that is associated with long-term structural cardiac remodeling, including left ventricle hypertrophy, but this element has uncertain clinical significance. Although left ventricle hypertrophy has traditionally been associated with an increased risk of cardiovascular disease, clinical studies have suggested that cardiac-specific outcomes of patients with end-stage renal disease were better with AVF compared with other dialysis modalities. This study uses a mouse model of AVF to study the structural, functional, and molecular correlates of AVF-induced cardiac remodeling. It finds that AVF causes an adaptive cardiac hypertrophy without functional decline or fibrosis. Transcriptional correlates suggest an electrical remodeling and the upregulation of proangiogenic, procardiogenic, and prosurvival factors, implying that AVF-induced cardiac hypertrophy is potentially cardioprotective, but also arrhythmogenic.

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.

Study on prediction of arterio-venous fistula maturation by flow mediated dilatation and AVF blood flow

BACKGROUND

The physiology and pathology of AVF maturation depends on the vessels characteristics and its ability to remodel. Outcome of AVF using flow mediated dilatation (FMD), AVF blood flow and diameter has been studied.

METHODOLOGY

Present observational study included single stage AVF (both Radiocephalic and Brachiocephalic) in consecutive CKD five patients (n = 158) prospectively over 1 year. Demographic and Doppler ultrasound parameters of upper limb (for vessel diameter and FMD) at baseline were recorded. Blood flow, diameter and depth of AVF were studied at 2, 6 and 12 weeks and their association with clinical maturation (usage of fistula with two needles for 75% of dialysis sessions during 15 day period) was studied (n = 129, after excluding lost to followup and expired patients; accordingly cohort was divided in matured (M) or non-matured (NM) groups. Clinical and radiological parameters between both groups were compared; receiver operator curve (ROC) and correlation of Doppler parameters were analysed.

RESULTS

Of 129 AVF, 67.4% were matured and 32.5% non-matured. Mean age was 40 years with male predominance75% in both the groups. The mean arterial diameter for distal (NM = 1.96 ± 0.58 and M = 2.02 ± 0.41) and proximal AVF (NM = 3.37 ± 0.82 and M = 3.36 ± 0.75) was not statistically different in both the groups. The matured fistula group had a mean FMD of 11.67 ± 4.09 as against FMD value of 9.365 ± 3.55 in the failed fistula group (p value 0.01). For maturation prediction, sensitivity and specificity of blood flow at 2 weeks were 86.2% and 59.5% and at 6 weeks 96.6% and 64.3%, respectively. In multivariate analysis predictors for AVF maturation were FMD (adjusted odds ratio (AOR) = 1.15) and blood flow (AOR = 1.67).

CONCLUSION

Second and Sixth week AVF blood flow was found to be predicting AVF maturation. Higher baseline FMD correlated with the AVF maturation, but not with vessel diameter.

Access flow volume (Qa) and survival in a hemodialysis population: An analysis of 5208 Qa measurements over a 9-year period

BACKGROUND

Aim of the study was to determine associations between characteristics of arteriovenous access (AVA) access flow volume (Qa, mL/min) and four year freedom from cardiovascular mortality (4yr-CVM) in hemodialysis (HD) patients.

METHODS

HD patients who received a primary AVA between January 2010 and December 2017 in one center were analyzed. Initial Qa was defined as the first Qa value obtained in a well-functioning AVA by a two-needle dilution technique. Actual Qa was defined as access flow at a random point of time. Changes in actual Qa were expressed per 3-month periods. CVM was assessed according to the ERA-EDTA classification. The optimal cut-off point for initial Qa was identified by a receiver operating characteristic curve. A joint modelling statistical technique determined longitudinal associations between Qa characteristics and 4yr-CVM.

RESULTS

A total of 5208 Qa measurements (165 patients, male n = 103; age 70±12 years, autologous AVA n = 146, graft n = 19) were analyzed. During follow-up (Dec 2010-Jan 2018, median 36 months), 79 patients (48%) died. An initial Qa < 900 mL/min was associated with an increased 4y-CVM risk (HR: 4.05; 95% CI [1.94-8.43], P<0.001). After 4 years, freedom from CVM was 34% lower in patients with a Qa < 900 mL/min (53 ±7% vs. Qa ≥ 900 mL/min: 87 ±4%, P <0.001). An association between increases in actual Qa over 3-month periods and mortality was found (HR: 4.48 per 100mL/min, 95% CI [1.44-13.97], P =0.010) indicating that patients demonstrating increasing Qa were more likely to die. By contrast, actual Qa per se was not related to survival.

CONCLUSIONS

Studying novel arteriovenous access Qa characteristics may contribute to understanding excess CVM in HD patients.

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.

Role of Doppler ultrasonography in the evaluation of hemodialysis arteriovenous access maturation and influencing factors

The goal of vascular access creation is to achieve a functioning arteriovenous fistula (AVF) or arteriovenous graft (AVG). An autologous fistula has been shown to be superior to AVG or to central venous catheters (CVCs) with lowest rate of re-intervention, but vessel obstruction or immaturity accounts for 20 % to 54% of cases with primary failure of AVF. This review is focused on the factors influencing maturation; indication and timing of preoperative mapping/creation of vascular access; ultrasound parameters for creation AVF/AVG; early postoperative complications following creation of a vascular access; ultrasound determinants of fistula maturation and endovascular intervention in vascular access with maturation failure. However, vascular accesses that fail to develop, have a high incidence of correctable abnormalities, and these need to be promptly recognized by ultrasonography and managed effectively if a high success rate is to be expected. We review approaches to promoting fistula maturation and duplex ultrasonography (DUS) of evaluating vascular access maturation.

Brief overview of surgical aspect of autologous arterio-venous fistula for dialysis access

Patients with the end-stage renal disease require renal replacement therapy in renal transplant, peritoneal dialysis, and intermittent hemodialysis. Hemodialysis remains the primary modality for renal replacement therapy. Excellent vascular access is a mainstay for performing hemodialysis. Here we present a brief review of the various surgical aspects of AV fistula creation. Preoperative physical examination and judicious use of the imaging modalities to define the artery and venous mapping provide a good outcome of the fistula formation. Surgical creation of RC-AVF is preferred for the end-stage renal disease patient. The end-to-side anastomosis between the radial artery and cephalic vein has shown very good results.

Comparison of one-year patency rates of end-to-side and side-to-side anastomosis technique in proximal forearm region radial-cephalic fistulas

OBJECTIVES

In this study, the effects of anastomosis techniques on the results of patients with autogenous radial-cephalic proximal forearm fistula were investigated.

METHODS

Patients who underwent radial-cephalic proximal forearm fistula surgery (arteriovenous fistula) between April 2015 and August 2017 at the Department of Cardiovascular Surgery of Ordu University were compared retrospectively in terms of the results of anastomosis techniques. The study included 131 patients who had arteriovenous fistulas created by side-to-side and end-to-side anastomosis technique.

RESULTS

There was no significant difference in demographic data, comorbidities, radial artery, and cephalic vein diameters in patients undergoing radial-cephalic proximal forearm fistula surgery. However, it was observed that fistula maturation was earlier in the group with end-to-side anastomosis technique, and the one-year patency rates were higher in the group with side-to-side anastomosis technique.

CONCLUSION

In Arteriovenous fistulas created in the proximal forearm region, the one-year patency rate of the side-to-side anastomosis technique was higher, while the maturation of the end-to-side technique observed earlier.

Point-of-care Vascular Ultrasound: Of Fistulas and Flows

Point-of-care ultrasound (POCUS) is increasingly being used in nephrology as a diagnostic tool, and there is a growing interest among physicians and nursing staff to learn how to use POCUS for the evaluation of the dialysis vascular access (DVA). The goal of POCUS is to extend the physical examination and more closely evaluate the DVA at bedside. Typically, POCUS quickly answers yes-no questions (ie, Is the vein too deep? Y/N). It is not the goal of POCUS of the vascular access to extensively investigate the entire fistula or graft. In conjunction with a good physical examination, brightness-mode ultrasound alone can answer most questions regarding the DVA, such as depth and diameter of the vessel. With some additional training, a limited color Doppler can be added to the standard evaluation to check flow direction and pseudoaneurysms. With more extensive training and an understanding of Doppler physics, access flow volumes can also be determined using spectral Doppler-mode ultrasound.

Monitoring the Patient Following Radio-Cephalic Arteriovenous Fistula Creation: Current Perspectives

Autogenous radial–cephalic direct wrist arteriovenous fistula (RC-AVF) in the non-dominant arm is the gold standard for dialysis vascular access. However, the RC-AVF non-maturation rate is significant (≃ 40%) due to an increasingly elderly and comorbid population incidence. A detailed identification of the biological cascade underlying arteriovenous fistula (AVF) maturation could be the key to clinical research aimed at identify the group of patients at risk of primary AVF failure. Currently, careful post-operative monitoring remains the most crucial aspect to overcome the problem of impaired maturation. Up to 80% of patients with immature RC-AVF have problems potentially solvable with early endovascular or surgical correction. Physical examination by experienced practitioners in conjunction with duplex ultrasound examination (DUS) can identify physical signs of non-maturation, understand the underlying cause, and drive for a tailored early planning to treat the complication. New approaches for the early assessment of AVF maturation are under study. Techniques to promote RC-AVF maturation performed through the administration of pre-or peri-operative drugs have missed up to now to prove an efficacy in improving fistula success. The new techniques tested after surgery appear to hold future promise for improving fistula maturation.

Multicentre Study on the Efficacy of Brachial Artery Transposition Among Haemodialysis Patients

OBJECTIVE

Brachial artery transposition (BAT) is not a well known method for obtaining vascular access (VA) for maintenance haemodialysis. This study evaluated the outcomes of BAT.

METHODS

This multicentre retrospective cohort study included 233 consecutive patients who underwent BAT between January 2012 and December 2013. The indications were inadequate vessels for obtaining VA, severe heart failure, hand ischaemia, central vein stenosis/occlusion, or a history of catheter/graft infection. The transposed brachial artery was used only for arterial inflow and other routes were used for outflow.

RESULTS

BAT was successful in 227 patients, and adequate blood flow was achieved during dialysis sessions. The first successful cannulation was after a median of 18 days. BAT was performed using superficial veins as the return route in 127 patients and arteriovenous fistula (AVF) creation in 63 patients to prevent maturation failure. In 41 patients with central venous catheterisation, the transposed brachial artery was used for arterial inflow. The complications of BAT were impaired wound healing in 14 patients, including skin necrosis in two; large aneurysms in six, including a mycotic pseudo-aneurysm in one; arterial thrombosis in five; hand ischaemia in five; lymphorrhoea in four; and haematoma/bleeding in three. The transposed brachial artery was abandoned in four, three, three, and one case of arterial thrombosis/stenosis, haematoma/bleeding, skin necrosis, and large aneurysm, respectively. Access to the return routes failed in 48 cases because of vein damage caused by cannulation in 22, AVF thrombosis/stenosis in 14, catheter infection in six, and catheter occlusion in six. At two years, the primary patency rates of the transposed brachial artery and access circuit were 88% and 54%, respectively.

CONCLUSION

BAT is a safe and effective technique. The patency was high for the transposed brachial artery but adequate for the access circuit. BAT can be considered for patients with an unobtainable standard arteriovenous access.

Factors Affecting the Patency of Radiocephalic Arteriovenous Fistulas Based on Clinico-Radiological Parameters

Arteriovenous fistulas are an important means of vascular access for long-term haemodialysis in patients with end-stage renal disease (ESRD). We evaluated the outcome of radiocephalic arteriovenous fistulas (RCAVFs) in 55 patients operated upon in our hospital in southern India. We studied the outcome of RCAVF surgery with the demographic factors, duration of diabetes, the diameter of the radial artery and cephalic vein, and any signs of atherosclerosis in the radial artery. We found that a small cephalic vein size of ≤ 2 mm, a negative cephalic vein tap test, a thickened, non-compressible, calcified radial artery on palpation, and evidence of atherosclerosis on radiological investigations were associated with a significant chance of RCAVF failure. A clinico-radiological grading of atherosclerosis for peripheral arteries is also proposed. Any patient presenting to the microsurgeon with a small cephalic vein size, a negative cephalic vein tap test, a thickened, non-compressible, calcified vessel on palpation, and tram-track calcification or whole vessel calcification or severely atherosclerotic vessel on radiological evaluation must be approached with caution regarding RCAVF creation and must be prepared for an arteriovenous fistula (AVF) creation at a higher level.

Comparison of surgical versus percutaneously created arteriovenous hemodialysis fistulas

OBJECTIVE

The aim of the present study was to compare the results between percutaneous arteriovenous fistulas (p-AVFs) created with the Ellipsys device (Ellipsys Vascular Access System; Avenu Medical, San Juan Capistrano, Calif) and surgical arteriovenous fistulas (s-AVFs).

METHODS

A single-center retrospective comparative study of the first 107 patients who had undergone p-AVF creation with the Ellipsys system from May 2017 to May 2018 with an equal number of consecutive patients who had undergone s-AVF creation in our center during the same period. The primary endpoints included the maturation and patency rates. The secondary endpoints were reintervention, risk of infection, and the incidence of steal syndrome and aneurysm formation.

RESULTS

The demographic, hypertension, and diabetes data were similar for both groups. The only difference between the two groups was that more p-AVF patients had already been receiving hemodialysis (61% vs 47%; P < .05). The p-AVFs showed superior maturation rates at 6 weeks (65% vs 50%; P = .01). The primary patency rates were greater for the s-AVFs at 12 months (86% vs 61%; P < .01). However, primary patency was comparable between the two groups at 24 months (52% vs 55%; P = .48). No significant difference was found in the secondary patency rates at 12 (90% vs 91%) and 24 (88% vs 91%) months. At the 2-year follow-up point, the rate of percutaneous reintervention was similar; however, the s-AVFs had required more frequent surgical revision (36% vs 17%; P = .01). Issues with wound healing and infection were also more frequent with s-AVFs (9% vs 0.9%; P < .01).

CONCLUSIONS

Fistulas created percutaneously with the Ellipsys system showed superior maturation rates and similar patency with s-AVFs created in an experienced high-volume vascular surgery practice. p-AVFs had a lower risk of wound healing issues, infection, and surgical revision. Larger, prospective, randomized multicenter studies are needed to confirm these findings.

Effectiveness of Flow Volume Measurement Training Using a Custom-Made Doppler Flow Simulator

INTRODUCTION

This study was conducted to analyze the effectiveness of a custom-made Doppler ultrasound (DUS) flow simulator, vascular phantom, and Doppler test fluid in the training of dialysis staff in flow volume (FV) measurements for arteriovenous (AV) access in hemodialysis (HD) patients.

METHODS

A DUS flow simulator was constructed using a continuous renal replacement therapy machine. Vascular phantoms were constructed using a rubber enema tube and keyboard cleaning gel. The Doppler test fluid consisted of freeze-dried instant coffee granules and 0.9% saline. This easy and affordable simulator was used to train 12 dialysis staff members, with no previous experience in DUS FV measurement. After a 3-day lecture course, the staff members performed DUS analyses on the AV access of HD patients. Thereafter, they underwent a 3-day training course using the simulator and then performed the DUS analyses of the AV access again. Each staff member assessed the FV 3 times, and the mean values of the measurements pretraining and posttraining were analyzed using paired t tests.

RESULTS

The difference in the mean value of FV measurements and the reference value decreased from 131.6 mL/min to 62.5 mL/min (95% confidence interval = 30.0-108.0, P = 0.002), and the standard deviation of the FV measurements decreased from 96.9 mL/min to 47.0 mL/min (95% confidence interval = 7.9-91.8, P = 0.023) after DUS training with the simulator.

CONCLUSIONS

The accuracy and reproducibility of FV measurements markedly improved after training with the simulator; it may be helpful for medical practitioners involved in AV access for HD treatment.

PATENCY-2 trial of vonapanitase to promote radiocephalic fistula use for hemodialysis and secondary patency

OBJECTIVE

Arteriovenous fistulas created for hemodialysis often fail to become usable and are frequently abandoned. This prospective trial evaluated the efficacy of vonapanitase, a recombinant human elastase, in increasing radiocephalic fistula use for hemodialysis and secondary patency.

METHODS

PATENCY-2 was a randomized, double-blind, placebo-controlled trial in patients on or approaching the need for hemodialysis undergoing radiocephalic arteriovenous fistula creation. Of 696 screened, 613 were randomized, and 603 were treated (vonapanitase n = 405, placebo n = 208). The study drug solution was applied topically to the artery and vein for 10 min immediately after fistula creation. The primary endpoints were fistula use for hemodialysis and secondary patency (fistula survival without abandonment). Other efficacy endpoints included unassisted fistula use for hemodialysis, primary unassisted patency, fistula maturation and unassisted maturation by ultrasound criteria, and fistula procedure rates.

RESULTS

The proportions of patients with fistula use for hemodialysis was similar between groups, 70% vonapanitase and 65% placebo, (p = 0.33). The Kaplan-Meier estimates of 12-month secondary patency were 78% (95% confidence interval [CI], 73-82) for vonapanitase and 76% (95% CI, 70-82) for placebo (p = 0.93). The proportions with unassisted fistula use for hemodialysis were 46% vonapanitase and 37% placebo (p = 0.054). The Kaplan-Meier estimates of 12-month primary unassisted patency were 50% (95% CI, 44-55) for vonapanitase and 43% (95% CI, 35-50) for placebo (p = 0.18). There were no differences in the proportion of patients with fistula maturation or in fistula procedure rates. Adverse events were similar between groups. Vonapanitase was not immunogenic.

CONCLUSIONS

Vonapanitase treatment did not achieve clinical or statistical significance to meaningfully improve radiocephalic fistula surgical outcomes. Outcome in the placebo group were better than in historical controls. Vonapanitase was well-tolerated and safe.

TRIAL REGISTRATION

clinicaltrials.gov: NCT02414841 (https://clinicaltrials.gov/ct2/show/NCT02414841).

Preoperative assessment for percutaneous and open surgical arteriovenous fistula creation in patients for haemodialysis

Preoperative assessment prior to surgical arteriovenous fistulas (AVFs) including ultrasound-guided mapping has been shown to have beneficial effects on their immediate success as well as early outcomes. This has led to their wide acceptance and adoption however clinical practice criteria is variable and is reflected in variabilities in practice. When transposing this to percutaneously created endovascular AVFs (endoAVFs), variable preoperative assessment criteria could equally result in variable practice and potentially subsequent and expectant outcomes. We aimed to review literature on reported validated methodologies and workflows of preoperative assessment for surgical AVF creation as reported in highest levels of available evidence, specifically randomized controlled trials. Published practice recommendations and guidelines on best clinical practice as well as systematic reviews and meta-analyses of published studies were also reviewed. Data on practice methodology from identified trial publications and protocols was collated and a summative narrative synthesis was carried out which compared these methodologies to additional assessments that may be required when targeting assessment for percutaneous endoAVF formation, based on our units experience as part of an international multicentre trial. In this review we present a brief overview of published literature and guidelines and propose a unified and uniform workflow for preoperative assessment for surgical AVFs and endoAVFs to aide clinical and imaging practice.

Role of early postoperative ultrasonography in prediction of AV fistula failure in hemodialysis patients

Background

Doppler ultrasonography (US) is the main imaging modality of hemodialysis AV fistula as it is safe non-invasive accurate modality. This study is to measure the arteriovenous (AV) fistula blood flow during early postoperative period (7–14 days) and assess its predictive role in AV fistula failure in hemodialysis patients. Color Doppler ultrasonography (CDU) was used to estimate the blood flow in the AV fistula of 100 patients at (7–14 days) after the fistula creation. The performance of fistula blood flow during early postoperative periods for predicting fistula failure was evaluated, and optimal cutoff value was determined.

Results

During the follow-up period (6 months), we classified the fistulas as 82 mature, and 18 failed. The blood flow was considerably lower in the failure group than that in the mature group at the early postoperative period (P value = 0.001). The areas under the curves (AUC) were 0.952, and the cutoff value was 200.5 ml/min. The sensitivity of CDU in prediction of fistula failure is 99% with negative predictive value 94% and accuracy 97%, and with specificity 89% and positive predictive value 98%.

Conclusion

Measuring blood flow of the AV fistula at the early postoperative period probably has a predictive role in the AV fistula failure. There is risk of failure if the blood flow less than 200 ml/min at (day 7–14)

Implanted blood vessel external support device (VasQ™) for creation of hemodialysis arteriovenous fistula: A single-center experience

INTRODUCTION

the external support device VasQ is intended to promote arteriovenous fistula (AVF) maturation by maintaining the optimal anastomotic angle in order to minimize blood flow disturbances around the anastomotic area. The aim of the study is to assess efficacy and safety of the VasQ device both in brachiocephalic and radiocephalic fistulae.

METHODS

a single institution prospective study was conducted with implantation of the VasQ device during AVF creation. Clinical and Doppler ultrasounds evaluations were performed at day-1, 1, 6, and 12 months for assessment of device-related adverse events, AVF maturation and patency. Moreover, volume flow rate and diameter of outflow vein were measured. A total of 16 patients were enrolled. Ten brachiocephalic and 6 radiocephalic AVFs were created with VasQ. Preoperatively cephalic vein diameter was 3.6 ± 0.9 mm.

RESULTS

our population included 13 male and 3 females patients, 9 end stage kidney disease in conservative therapy, 4 dialysis treated patients, and 3 transplanted patients; mean age was 74.0 ± 8.1 years; no severe device-related adverse events were observed. Primary patency at 1, 6, and 12 months was 100%, 87.5%, and 67.7%, respectively, while secondary patency was 100%, 100%, and 78.3%, respectively. Comparing brachiocephalic to radiocephalic AVFs no significant differences in patency rates were seen. Overall maturation rate was 94% (15/16). Mean vein diameter measured with Doppler ultrasound at postoperative day-1 and at 1, 6, and 12 months was 5.0 ± 1.0, 5.9 ± 0.9, 7.2 ± 1.6, and 7.9 ± 1.4 mm, respectively, with a mean flow rate at the brachial artery of 841 ± 176, 1052 ± 224, 1261 ± 490, and 1348 ± 477 ml/min, respectively.

CONCLUSIONS

in our limited experience VasQ was safe, with high maturation and patency rates. Positive results suggest a potential benefit for VasQ in AVF.

Soluble vascular endothelial growth factor receptor-1 as a novel marker of arteriovenous fistula stenosis in hemodialysis patients

INTRODUCTION

Arteriovenous fistula (AVF) stenosis is one of the most important clinical problems in hemodialysis patients. The histopathological findings of neointimal hyperplasia and impaired angiogenesis have been well established in stenotic AVFs. Soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) has been implicated in pathological angiogenesis. Thus, we aimed to investigate the association between sVEGFR-1 and AVF stenosis in hemodialysis patients.

METHODS

This prospective cohort study included 70 patients with end-stage renal disease. Forty-five patients were included in the final analysis, and the median follow-up period was 36 months. Venous stenosis was detected by physical examination and documented by fistulography. Blood samples were analyzed a day before the fistula operation, and serum levels of sVEGFR-1 were measured.

FINDINGS

The median sVEGFR-1 level was higher in the stenosis group than in the nonstenosis group (17 pg/mL [89.5%] vs. 5 pg/mL [19.2%], respectively; P < 0.001]. According to body mass index (BMI) categories, obese patients (BMI > 30 kg/m² ) had the shortest stenosis-free survival (20 months [9.35-30.65]). Multivariate Cox analysis showed that sVEGFR-1, serum creatinine, and parathyroid hormone levels were associated with AVF stenosis risk. Kaplan-Meier survival curves showed that patients with less than the median value of sVEGFR-1 (<6093.07 pg/mL) had longer cumulative stenosis-free survival than patients with sVEGFR-1 levels above the median value (P < 0.001).

DISCUSSION

Increased levels of sVEGFR-1 and obesity were found to be associated with AVF stenosis in hemodialysis patients.

Sex differences in the vascular access of hemodialysis patients: a cohort study

Background

We describe differences for probability of receiving a fistula attempt, achieving fistula use, remaining catheter-free and the rate of access-related procedures as a function of sex.

Methods

Prospectively collected vascular access data on incident dialysis patients from five Canadian programs using the Dialysis Measurement Analysis and Reporting System to determine differences in fistula-related outcomes between women and men. The probability of receiving a fistula attempt and the probability of fistula use were determined using binary logistic regression. Catheter and fistula procedure rates were described using Poisson regression. We studied time to fistula attempt and time to fistula use, accounting for competing risks.

Results

We included 1446 (61%) men and 929 (39%) women. Men had a lower body mass index (P < 0.001) and were more likely to have coronary artery disease (P < 0.001) and peripheral vascular disease (p < 0.001). A total of 688 (48%) men and 403 (43%) women received a fistula attempt. Women were less likely to receive a fistula attempt by 6 months {odds ratio [OR] 0.64 [95% confidence interval (CI) 0.52-0.79]} and to achieve catheter-free use of their fistula by 1 year [OR 0.38 (95% CI 0.27-0.53)]. At an average of 2.30 access procedures per person-year, there is no difference between women and men [incidence rate ratio (IRR) 0.97 (95% CI 0.87-1.07)]. Restricting to those with a fistula attempt, women received more procedures [IRR 1.16 (95% CI 1.04-1.30)] attributed to increased catheter procedures [IRR 1.50 (95% CI 1.27-1.78)]. There was no difference in fistula procedures [IRR women versus men 0.96 (95% CI 0.85-1.07)].

Conclusion

Compared with men, fewer women undergo a fistula attempt. This disparity increases after adjusting for comorbidities. Women have the same number of fistula procedures as men but are less likely to successfully use their fistula.

ASDIN white paper: Assessment and management of hemodialysis access-induced distal ischemia by interventional nephrologists

Although not common, hemodialysis access-induced distal ischemia is a serious condition resulting in significant hemodialysis patient morbidity. Patients with signs and symptoms suggestive of hand ischemia frequently present to the general and interventional nephrologist for evaluation. In order to care for these cases, it is necessary to understand this syndrome and its management. Most cases can be managed conservatively without intervention. Some cases requiring intervention may be treated using techniques within the scope of practice of the interventional nephrologists while other cases require vascular surgery. In order for the interventional nephrologists to evaluate and manage these cases in a timely and appropriate manner, practice guidelines are presented.

Patency Rates After Successful Arteriovenous Fistula Thrombectomy: Relevance of the Flow/d-Dimer Ratio in the Decision-Making

OBJECTIVES

Surgical thrombectomy for acute arteriovenous fistula (AVF) thrombosis is one of the primary salvage intervention. The independent risk factors affecting the patency of AVF after a successful thrombectomy are yet unknown. Here, the author aimed to report the results of surgically corrected AVFs and the independent risk factors which may cause early failure following the surgical salvage.

METHODS

The study cohort comprised 24 patients who had acute AVF thrombosis and underwent successful surgical thrombectomy in the first 24 to 48 hours between January 2016 and April 2020 in our center. The study group was divided into patients with recurrent AVF thrombosis (n = 11, 45.8%) and without recurrent AVF thrombosis (n = 13, 54.1%) following surgical thrombectomy with a follow-up of 22.4 ± 6.8 months. Postthrombectomy primary and secondary patency of AVF were also evaluated.

RESULTS

The mean age of the cohort was 58.1 ± 15.2 years. A simple thrombectomy was performed for all cases. Only 2 cases have required a revision at the anastomosis due to severe intimal hyperplasia. Postthrombectomy primary patency rate was 45.5% for 18 months. Receiver operating characteristic analysis was performed with a resulting area under the curve value of 0.81 (95% CI: 0.35-0.94, P = .006) for flow (mL)/d-dimer (ng/mL) <0.63 in predicting recurrent AVF thrombosis following surgical thrombectomy.

CONCLUSIONS

Flow (mL)/d-dimer (ng/mL) <0.63 was independent predictor of recurrent thrombosis (RT) of a surgically salvaged AVF. The patients at risk for RT or who may benefit from further intervention should be identified with predictive parameters.

Preliminary balloon dilation of both saphenous fascia and the saphenous vein increases the below-knee fistula patency, but not maturation

OBJECTIVE

There is no reliable secondary site for fistula creation in patients with preclusions for further use of upper extremity vessels as viable hemodialysis access. Below-knee vessels resemble the forearm vascular anatomy and, therefore, methods to improve the outcomes of fistula creation at this level would also help to improve the quality of life for those patients. The aim of the present study was to examine the efforts to improve the functionality of below-knee fistulas in a sample of dialysis patients.

METHODS

We retrospectively evaluated the results of ankle fistulas created following preliminary balloon dilatation of both the saphenous fascia and the saphenous vein in 11 patients who were considered eligible if they did not have concomitant venous or arterial lower extremity disease. We assessed the changes in fistula flow within 6 months as well as patency and maturation rates.

RESULTS

Though the patency rate at 6 months was 63.6% (seven patients), only three fistulas (27.3%) were used for routine dialysis. All mature fistulas were observed in patients with a preoperative posterior tibial artery flow of more than 35 mL/min.

CONCLUSION

Saphenous vein dilation throughout the below-knee promotes fistula patency, but the posterior tibial artery shows inadequate response as an inflow supplier at the ankle level. More proximal connection of saphenous vein after balloon dilation may be used in the future to achieve adequate flow from leg arteries.

Sonographer’s Role in the Screening, Diagnosis, and Treatment of Dialysis Fistula Pseudoaneurysms

Pseudoaneurysm (PSA) formation, in an arteriovenous fistula (AVF) undergoing hemodialysis, can occur as a result of frequent venipunctures and can lead to a weakened vessel wall. Since many dialysis patients’ lives depend on their weekly hemodialysis sessions, complications that result from dialysis require treatment. A PSA can be a life-threatening complication, especially for these patients. Sonography has been demonstrated to be a useful modality of choice in the screening, diagnosis, and treatment of a PSA. The sonographic appearance of a PSA using gray-scale, color, and spectral Doppler can play a significant role in ruling out other diagnoses. A case study is presented of a dialysis-dependent patient who developed a PSA in his dialysis access site. Sonography played a key role in the diagnosis and follow-up for this specific case. Due to the risks involved with these patients, there is an essential need for sonographers to be competent in performing these examinations. Evaluation of the AVF to check for patency and a thorough assessment of the PSA are required.

Arteriovenous fistula maturation and the influence of fluid dynamics

Arteriovenous fistula creation is the preferred vascular access for haemodialysis therapy, but has a large failure rate in the maturation period. This period generally lasts 6 to 8 weeks after surgical creation, in which the vein and artery undergo extensive vascular remodelling. In this review, we outline proposed mechanisms for both arteriovenous fistula maturation and arteriovenous fistula failure. Clinical, animal and computational studies have not yet shown a definitive link between any metric and disease development, although a number of theories based on wall shear stress metrics have been suggested. Recent work allowing patient-based longitudinal studies may hold the key to understanding arteriovenous fistula maturation processes.

Early Predictors of Arteriovenous Fistula Maturation: A Novel Perspective on an Enduring Problem

BACKGROUND

Preoperative ultrasound mapping is routinely used to select vessels meeting minimal threshold diameters for surgical arteriovenous fistula (AVF) creation but fails to improve AVF maturation rates. This suggests a need to reassess the preoperative ultrasound criteria used to optimize AVF maturation.

METHODS

We retrospectively identified 300 catheter-dependent patients on hemodialysis with a new AVF created between 2010 and 2016. We then evaluated the associations of preoperative vascular measurements and hemodynamic factors with unassisted AVF maturation (successful use for dialysis without prior intervention) and overall maturation (successful use with or without prior intervention). Multivariable logistic regression was used to identify preoperative factors associated with unassisted and overall AVF maturation.

RESULTS

Unassisted AVF maturation associated with preoperative arterial diameter (adjusted odds ratio [aOR], 1.50 per 1-mm increase; 95% confidence interval [95% CI], 1.23 to 1.83), preoperative systolic BP (aOR, 1.16 per 10-mm Hg increase; 95% CI, 1.05 to 1.28), and left ventricular ejection fraction (aOR, 1.07 per 5% increase; 95% CI, 1.01 to 1.13). Overall AVF maturation associated with preoperative arterial diameter (aOR, 1.36 per 1-mm increase; 95% CI, 1.10 to 1.66) and preoperative systolic BP (aOR, 1.17; 95% CI, 1.06 to 1.30). Using receiver operating curves, the combination of preoperative arterial diameter, systolic BP, and left ventricular ejection fraction was fairly predictive of unassisted maturation (area under the curve, 0.69). Patient age, sex, race, diabetes, vascular disease, obesity, and AVF location were not associated with maturation.

CONCLUSIONS

Preoperative arterial diameter may be an under-recognized predictor of AVF maturation. Further study evaluating the effect of preoperative arterial diameter and other hemodynamic factors on AVF maturation is needed.

Association between initial dialytic modalities and the risks of mortality, infection death, and cardiovascular events: A nationwide population-based cohort study

To date, few studies have been conducted to pairwise compare the prognosis of peritoneal dialysis (PD), unplanned PD, and unplanned hemodialysis (HD). We analyzed longitudinal data from Taiwan’s National Health Insurance Research Database. We included 45,165 patients whose initial dialytic modality was PD or unplanned HD between January 1, 2001 and December 31, 2013. We divided the patients into three groups according to their initial dialytic modalities. The primary outcomes were all-cause mortality and death from infection during 1-year follow up. The risks of all-cause mortality and infection death were higher in the unplanned PD group than in the planned PD group (hazard ratio [HR] 1.43, 95% confidence interval [CI] 1.28–1.60; HR 1.54, 95% CI 1.32–1.80). Likewise, the risks of all-cause mortality and infection death were higher in the unplanned HD group (HR 1.64, 95% CI 1.48–1.82; HR 1.85, 95% CI 1.61–2.13). Furthermore, the risks of all-cause mortality and infection death were also higher in the unplanned HD group than in the unplanned PD group (HR 1.15, 95% CI 1.07–1.23; HR 1.20, 95% CI 1.09–1.32). In conclusion, our study demonstrates that patients whose initial modality was planned PD or unplanned PD may have better clinical outcomes than those whose initial modality was unplanned HD.

Pre-operative Patient Specific Flow Predictions to Improve Haemodialysis Arteriovenous Fistula Maturation (Shunt Simulation Study): A Randomised Controlled Trial

OBJECTIVE

An arteriovenous fistula (AVF) needs to mature before it becomes suitable to cannulate for haemodialysis treatment. Maturation importantly depends on the post-operative flow increase. Unfortunately, 20-40% of AVFs fail to mature (FTM). A patient specific computational model that predicts immediate post-operative flow was developed, and it was hypothesised that providing information from this model for planning of fistula creation might reduce FTM rates.

METHODS

A multicentre, randomised controlled trial in nine Dutch hospitals was conducted in which patients with renal failure who were referred for AVF creation, were recruited. Patients were randomly assigned (1:1) to the control or computer simulation group. Both groups underwent a work up, with physical and duplex ultrasonography (DUS) examination. In the simulation group the data from the DUS examination were used for model simulations, and based on the immediate post-operative flow prediction, the ideal AVF configuration was recommended. The primary endpoint was AVF maturation defined as an AVF flow ≥500 mL/min and a vein inner diameter of ≥4 mm six weeks post-operatively. The secondary endpoint was model performance (i.e. comparisons between measured and predicted flows, and (multivariable) regression analysis for maturation probability with accompanying area under the receiver operator characteristic curve [AUC]).

RESULTS

A total of 236 patients were randomly assigned (116 in the control and 120 in the simulation group), of whom 205 (100 and 105 respectively) were analysed for the primary endpoint. There was no difference in FTM rates between the groups (29% and 32% respectively). Immediate post-operative flow prediction had an OR of 1.15 (1.06-1.26; p < .001) per 100 mL/min for maturation, and the accompanying AUC was 0.67 (0.59-0.75).

CONCLUSION

Providing pre-operative patient specific flow simulations during surgical planning does not result in improved maturation rates. Further study is needed to improve the predictive power of these simulations in order to render the computational model an adjunct to surgical planning.

A prospective cohort study of predictors of upper extremity arteriovenous fistula maturation

BACKGROUND

A substantial proportion of arteriovenous fistulas fail to function adequately for hemodialysis. Existing studies on arteriovenous fistula failure prediction assess patency rather than the more clinically relevant outcome of arteriovenous fistula function. We hypothesized that preoperative demographic and ultrasound characteristics, and postoperative assessment by an experienced vascular access nurse would predict which arteriovenous fistulas will not function adequately for hemodialysis.

METHODS

Prospective cohort study of chronic kidney disease patients at a tertiary care center in Vancouver, Canada, with arteriovenous fistula creation between 2009 and 2013. Pre and postoperative clinical assessment and ultrasound blood vessel mapping were performed by an experienced vascular access nurse. The primary outcome was failure to achieve a fistula used successfully for hemodialysis (FUSH).

RESULTS

Outcomes were assessed in 200 patients; 123 (61.5%) arteriovenous fistulas were radiocephalic. Overall, 26.5% of arteriovenous fistulas had FUSH failure (34.1% of lower arm vs 14.3% of upper arm, p = 0.002). Univariate predictors of FUSH failure included older age (p = 0.03), female sex (p = 0.05), smaller arterial diameter (p ⩽ 0.001), lower artery volume flow (p = 0.04), and smaller vein diameter (p = 0.01). In multivariable analysis, artery diameter (odds ratio: 0.44, 95% confidence interval: 0.28-0.68) most significantly predicted FUSH failure. Vascular access nurse assessment 6 weeks postoperatively correctly predicted outcome in 83.8% of FUSH and 65.0% of FUSH failure.

CONCLUSION

Smaller artery diameter most strongly predicted FUSH failure. Early postoperative nursing assessment was more useful to predict FUSH than FUSH failure, and as such was insufficient in determining which arteriovenous fistulas should be abandoned as many predicted to fail could be salvaged with further intervention.

Point-of-care ultrasound for assessing arteriovenous fistula maturity in outpatient hemodialysis

BACKGROUND

Point-of-care ultrasound in end-stage renal disease is on the rise. Presently the decision to cannulate an arteriovenous fistula is based on its duration since surgery and physical exam. This study examines the effects of point-of-care ultrasound on decreasing the time to arteriovenous fistula cannulation, time spent with a central venous catheter, and the complications and infections that arise.

METHODS

Prospective point-of-care ultrasound patients were recruited between January 2015 and January 2018, while retrospective data (non-point-of-care ultrasound) were collected via chart review from patients who had fistula creation between November 2011 and May 2014. Patients had point-of-care ultrasound within 3 weeks after arteriovenous fistula creation and were followed for 1 year. Arteriovenous fistula cannulation was initiated when the following parameters were met: diameter > 6 mm (with no depreciable narrowing of more than 20% throughout), depth < 6 mm, and length > 6 cm. Demographic data, as well as time to cannulation and central venous catheter removal, number of infections, complications, and interventions were compared between point-of-care ultrasound and non-point-of-care ultrasound groups using unpaired t-test, chi-square, and Fisher exact test statistical analysis.

RESULTS

A total of 37 patients with new arteriovenous fistulas were followed by point-of-care ultrasound compared to 29 non-point-of-care ultrasound patients. Point-of-care ultrasound patients had earlier cannulations (35.5 vs 63.3 days, p < 0.05), shorter central venous catheter duration (68.2 vs 98.3 days, p < 0.05), and less infections (12 vs 19) without differences in complication compared to the non-point-of-care ultrasound.

CONCLUSION

Point-of-care ultrasound facilitates early and safe arteriovenous fistula cannulation leading to a reduction in central venous catheter time and risk of infection. Point-of-care ultrasound may also aid in earlier identification of complications and difficult cannulations.

Vascular access in children requiring maintenance haemodialysis: a consensus document by the European Society for Paediatric Nephrology Dialysis Working Group

BACKGROUND

There are three principle forms of vascular access available for the treatment of children with end stage kidney disease (ESKD) by haemodialysis: tunnelled catheters placed in a central vein (central venous lines, CVLs), arteriovenous fistulas (AVF), and arteriovenous grafts (AVG) using prosthetic or biological material. Compared with the adult literature, there are few studies in children to provide evidence based guidelines for optimal vascular access type or its management and outcomes in children with ESKD.

METHODS

The European Society for Paediatric Nephrology Dialysis Working Group (ESPN Dialysis WG) have developed recommendations for the choice of access type, pre-operative evaluation, monitoring, and prevention and management of complications of different access types in children with ESKD.

RESULTS

For adults with ESKD on haemodialysis, the principle of "Fistula First" has been key to changing the attitude to vascular access for haemodialysis. However, data from multiple observational studies and the International Paediatric Haemodialysis Network registry suggest that CVLs are associated with a significantly higher rate of infections and access dysfunction, and need for access replacement. Despite this, AVFs are used in only ∼25% of children on haemodialysis. It is important to provide the right access for the right patient at the right time in their life-course of renal replacement therapy, with an emphasis on venous preservation at all times. While AVFs may not be suitable in the very young or those with an anticipated short dialysis course before transplantation, many paediatric studies have shown that AVFs are superior to CVLs.

CONCLUSIONS

Here we present clinical practice recommendations for AVFs and CVLs in children with ESKD. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system has been used to develop and GRADE the recommendations. In the absence of high quality evidence, the opinion of experts from the ESPN Dialysis WG is provided, but is clearly GRADE-ed as such and must be carefully considered by the treating physician, and adapted to local expertise and individual patient needs as appropriate.

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.

Altered hemodynamics during arteriovenous fistula remodeling leads to reduced fistula patency in female mice

Objective

The arteriovenous fistula (AVF) is the preferred method of dialysis access because of its proven superior long-term outcomes. However, women have lower rates of AVF patency and utilization than men. We used a novel mouse AVF model that recapitulates human AVF maturation to determine whether there are differences in AVF patency in female and male mice.

Methods

Aortocaval fistulas were created in female and male C57BL/6 mice (9-10 weeks). At days 0, 3, 7, and 21, infrarenal inferior vena cava (IVC) and aortic diameters and flow velocity were monitored by Doppler ultrasound and used to calculate the vessel diameter, blood flow, and shear stress. AVF were harvested, and expression of proteins was examined by proteomic analysis and immunofluorescence and of messenger RNA by quantitative polymerase chain reaction analysis.

Results

At baseline, female mice weighed less and had lower IVC velocity and smaller magnitudes of shear stress, but there was no significant difference in IVC diameter and thickness. After AVF creation, both female and male mice had similar IVC dilation and thickening with no significant differences in IVC wall thickness at day 21. However, female mice had diminished AVF patency by day 42 (25.7% vs 64.3%; P = .039). During fistula remodeling, female mice had lower IVC mean velocity and shear stress magnitude and increased spectral broadening (days 0-21). Messenger RNA and protein expression of Krüppel-like factor 2, endothelial nitric oxide synthase, and vascular cell adhesion molecule 1 was similar at baseline in female and male mice but increased in the AVF only in male mice but not in female mice (day 21). Proteomic analysis of female and male mice detected 56 proteins expressed at significantly higher levels in the IVC of female mice and 67 proteins expressed at significantly higher levels in the IVC of male mice (day 7); function-specific analysis showed that the IVC of male mice overexpressed proteins that belong to pathways implicated in the regulation of vascular function, thrombosis, response to flow, and vascular remodeling.

Conclusions

AVF in female mice have diminished patency, preceded by lower velocity, reduced magnitudes of shear stress, and less laminar flow during remodeling. There is also sex-specific differential expression of proteins involved in thrombosis, response to laminar flow, inflammation, and proliferation. These findings suggest that hemodynamic changes during fistula maturation may play an important role underlying the diminished rates of AVF utilization in women.

Women have lower rates of arteriovenous fistula (AVF) utilization than men. Using a mouse AVF model that recapitulates human AVF maturation, we show that female mice have similar AVF remodeling but diminished patency. AVF remodeling in female mice is associated with reduced shear stress and laminar flow; lack of increased transcription and translation of several anti-inflammatory, antiproliferative, and laminar flow response proteins (endothelial nitric oxide synthase, Krüppel-like factor 2, and vascular cell adhesion molecule 1); and different patterns of expression of pathways that regulate thrombosis and venous remodeling. Identifying downstream targets involved in these mechanisms may improve AVF outcomes in female patients.

Vascular access cannulation in hemodialysis patients: technical approach

INTRODUCTION

The vascular access cannulation technique varies among clinics, and guidelines on vascular access give little importance to cannulation techniques. The objective of this study was to evaluate the cannulation technique and to determine which factors are associated with each detail of the technique.

MATERIAL AND METHODS

The vascular access cannulation was evaluated in 260 patients undergoing hemodialysis. The type and anatomical location of the vascular access, the cannulation technique, direction, gauge, and distance between needles, besides bevel direction and needle rotation were registered.

RESULTS

The arteriovenous fistula was the most frequent vascular access (88%), the most used cannulation technique was area (100%), the needle direction was anterograde in most cases (79.5%), and the mean distance between the tips of needles was 7.57±4.43 cm. For arteriovenous grafts, the proximal anatomical location (brachial artery) and cannulation with 16G needles in anterograde position were more predominant. For arteriovenous fistulas, the distal anatomical location (radial artery) and cannulation through 15G needles were more common. Cannulation of vascular access in retrograde direction was associated with a greater distance between needles (13.2 ± 4.4 vs 6.1 ± 3 cm, p < 0.001). Kt/V was higher when the distance between needles was higher than 5 cm (1.61 ± 0.3 vs. 1.47 ± 0.28, p < 0.01).

CONCLUSIONS

The vascular access cannulation technique depends on the vascular access characteristics and expertise of cannulators. Clinical trials are required for the formulation of guidelines for vascular access cannulation.