Comparative analysis of RADAR vs. conventional techniques for AVF maturation in patients with blood viscosity and vessel elasticity-related diseases through fluid-structure interaction modeling: Anemia, hypertension, and diabetes

PURPOSE

This study aims to compare two surgical techniques, the standard Vein-to-Artery and the newer Artery-to-Vein (Radial Artery Deviation And Reimplantation; RADAR), for enhancing the success of Arterio-Venous Fistula maturation in end-stage renal disease patients. The impact of diseases like anemia, diabetes, hypertension, and chronic kidney disease were considered. The goals are to advance Arterio-Venous Fistula (AVF) surgery, improve patient outcomes, and contribute to evidence-based surgical guidelines.

METHODS

Fluid-structure interaction modeling was employed to investigate how hemodynamic and mechanical stresses impact arteriovenous fistula maturation, with a particular focus on the role of wall shear stress in determining maturation outcomes. The critical threshold for vessel injury was identified as wall shear stress values exceeding 35 N/m2, while stenosis formation was projected to occur at levels below 1 N/m2. This work introduced a novel approach by considering disease-related factors, including blood viscosity (anemia), and vessel elasticity (diabetes, hypertension, and chronic kidney diseases), which directly influence hemodynamics and the generation of wall shear stress. Furthermore, the model was designed to incorporate varying thicknesses and elasticities for both the vein and artery, accurately representing authentic vascular anatomy.

RESULTS

The RADAR technique has demonstrated superior performance compared to the standard technique by providing appropriate wall shear stress in critical regions and minimizing the risk of wall damage. Its use of a thicker vessel also reduces the risk of vessel injury, making it particularly effective for patients with Chronic Kidney Disease (CKD), hypertension, anemia, and diabetes, ensuring optimal blood flow and fewer complications. However, there are minor concerns about stenosis formation in hypertension and anemia cases, which could be mitigated by adjusting the anastomosis angle to be lower than 30°.

CONCLUSION

Diabetes and hypertension have significant physiological effects that increase the risks associated with arteriovenous fistula maturation. The anemic condition resulting from CKD may help reduce vessel injury but raises concerns about potential stenosis formation. Despite these co-morbidities, the RADAR technique has demonstrated its ability to induce more favorable hemodynamic changes, promoting arteriovenous fistula maturation.

A comparison of arteriovenous fistula failure between Malaysian and Australian and New Zealand participants enrolled in the FAVOURED trial

AIM

To describe and compare de novo arteriovenous fistula (AVF) failure rates between Australia and New Zealand (ANZ), and Malaysia.

BACKGROUND

AVFs are preferred for haemodialysis access but are limited by high rates of early failure.

METHODS

A post hoc analysis of 353 participants from ANZ and Malaysia included in the FAVOURED randomised-controlled trial undergoing de novo AVF surgery was performed. Composite AVF failure (thrombosis, abandonment, cannulation failure) and its individual components were compared between ANZ (n = 209) and Malaysian (n = 144) participants using logistic regression adjusted for patient- and potentially modifiable clinical factors.

RESULTS

Participants' mean age was 55 ± 14.3 years and 64% were male. Compared with ANZ participants, Malaysian participants were younger with lower body mass index, higher prevalence of diabetes mellitus and lower prevalence of cardiovascular disease. AVF failure was less frequent in the Malaysian cohort (38% vs 54%; adjusted odds ratio (OR) 0.53, 95% confidence interval (CI) 0.31-0.93). This difference was driven by lower odds of cannulation failure (29% vs 47%, OR 0.45, 95% CI 0.25-0.80), while the odds of AVF thrombosis (17% vs 20%, OR 1.24, 95% CI 0.62-2.48) and abandonment (25% vs 23%, OR 1.17, 95% CI 0.62-2.16) were similar.

CONCLUSIONS

The risk of AVF failure was significantly lower in Malaysia compared to ANZ and driven by a lower risk of cannulation failure. Differences in practice patterns, including patient selection, surgical techniques, anaesthesia or cannulation techniques may account for regional outcome differences and warrant further investigation.

The role of vacuum-assisted mechanical thrombectomy in the management of acutely thrombosed arteriovenous fistulas and grafts

PURPOSE

The purpose of this study is to evaluate the safety and efficacy of the mechanical thrombectomy with the Indigo System in the treatment of thrombosed arteriovenous fistulas and grafts.

METHODS

A retrospective search of endovascular procedures performed from November 2018 to June 2020 was conducted. Inclusion criteria were: acute arteriovenous fistula or graft thrombosis that underwent endovascular mechanical thrombectomy with Indigo System. The following information was collected from each case: sex, age, fistula modality, fistula location, treatment modality, and outcomes. Endpoints evaluated were: technical and clinical success rates; primary, assisted primary, and secondary patency rates; complication rates.

RESULTS

Twenty-six mechanical thrombectomy procedures for declotting of arteriovenous fistula thrombosis, using the Indigo System, were performed in 22 patients. Technical and clinical success was achieved in 23/26 cases (88%). Mean follow-up was 9 months (range 11-539 days). The 6-month primary, primary assisted, and secondary patency rates were 71%, 86%, 93% and the 12-month primary, primary assisted, and secondary patency rates were 71%, 72%, 80%, respectively. No technical or device-related complications were observed during thrombectomy, however two venous ruptures occurred on the angioplasty of the underlying stenosis.

CONCLUSION

In conclusion, vacuum-assisted thrombectomy of acutely thrombosed arteriovenous fistulas and grafts with Indigo System is safe and effective, providing good short term patency rates.

Arteriovenous fistula creation with VasQTM device: A feasibility study to reveal hemodynamic implications

BACKGROUND

Arteriovenous fistula (AVF) is the preferred vascular access (VA) for hemodialysis, but it is still affected by high non-maturation and early failure rates due to stenosis development. Increasing evidence suggests that the presence of turbulent-like flow may play a key role, therefore, to stabilize the flow in the venous segment, an external support device (VasQTM) has been designed. The aim of this study was to provide preliminary evidence of VasQTM impact on AVF hemodynamics as compared to AVFs created with conventional surgery.

METHODS

In this pilot single-center prospective randomized study six patients were enrolled, three in the VasQ group and three in the control group. Contrast-free magnetic resonance imaging (MRI) scans were acquired at 3 days, 3 months and 1 year after AVF surgery and were used to generate 3D patient-specific models. Computational fluid dynamic (CFD) simulations were performed using pimpleFoam, imposing patient-specific flow waveforms derived from ultrasound (US) examinations at the inlet of the proximal and distal artery, and a traction-free condition at the venous outflow. Morphologic and hemodynamic changes occurring over time were compared between VasQ and control AVFs.

RESULTS

Our MRI protocol provided high-quality images suitable for reliable segmentation and reconstruction of patient-specific 3D models of AVFs at all three timepoints in four out of six patients. The VasQTM device maintained the angle between the artery and the vein almost unchanged over time, with a more stable flow in the AVFs supported by the device. In contrast, one of the AVFs of the control group evolved to an extreme dilatation of the vein and highly disturbed flow, while the other developed a stenosis in the juxta-anastomotic region.

CONCLUSIONS

This study demonstrated the feasibility of characterizing the morphological and hemodynamic changes occurring over time in AVFs created using the VasQTM device and provided preliminary evidence of the potential hemodynamic benefits of its use.

Successful 8-year use of Venous Window Needle Guide for deep arteriovenous fistula cannulation

We describe the case of a patient who had been on hemodialysis for 8 years using a native arteriovenous fistula cannulated through the Venous Window Needle Guide™ device (VWING). The overall outcome was excellent and complication-free with intact state of the underlying vessel and a high degree of patient satisfaction. The patient was able to carry out self-cannulation without any difficulty almost from the very beginning. The current unavailability of VWING is a missed opportunity in the field of vascular access.

Strategies to Mitigate Bleeding in Shoulder Arthroplasty in the Setting of an Arteriovenous Fistula: A Report of 3 Cases

CASE

Arteriovenous (AV) fistula in the ipsilateral extremity for hemodialysis presents unique challenges during shoulder arthroplasty. We describe 3 cases of shoulder arthroplasty performed through a deltopectoral approach on the ipsilateral side of an AV fistula. In all cases, the cephalic vein was found to be arterialized with increased diameter and thickness. All procedures were successfully performed without injury to the arterialized cephalic vein.

CONCLUSION

This report highlighted strategies to mitigate catastrophic bleeding from an arterialized cephalic vein during shoulder arthroplasty, which includes preoperative cross-matching, expeditious vascular surgery availability, meticulous surgical dissection, and careful retractor placement.

Effect of exercises on the maturation of newly created arteriovenous fistulas over distal and proximal upper limb: A systematic review and meta-analysis

The aims of our review were: (i) to evaluate the effect of post-operative upper extremity exercise on maturation of AVFs, stratified by their locations. (ii) To evaluate the effect of pre-operative arm exercise on patients' superficial vein caliber of patients. Literature search was performed on PubMed, Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and China National Knowledge Infrastructure (CNKI) to identify eligible articles. The quality of the randomized controlled trials (RCTs) were assessed using the Cochrane Risk of Bias tool 2.0. In the Meta-analysis, Risk ratios (RRs) of clinical maturation and ultrasonographic maturation were pooled from studies focused on post-operative exercise program; Mean difference (MD) of venous caliver was pooled from those studied pre-operative exercise. Nine studies (six for post-operative exercise; three for pre-operative exercise) were included in the review. Among the AVFs created in distal region (158 patients in exercise group and 144 patients in control group), there was a significantly superior clinical maturation (RR: 1.28; 95% CI: 1.10-1.48, p = 0.001; I2 = 0), and ultrasonographic maturation (RR: 1.30; 95% CI: 1.07-1.59, p = 0.009; I2 = 0) in the exercise group in comparison to the control group. For the AVFs created in proximal region (93 and 96 patients in exercise group and control group respectively), there is no significant difference in clinical maturation (RR:1.25, 95% CI: 0.88-1.78, p = 0.27, I2 = 74%) and ultrasonographic maturation (RR: 1.17, 95% CI: 0.97-1.40, p = 0.11, I2 = 43%) between the exercise group and controls. For pre-operative exercise, the mean difference of 0.34 mm (95% CI: 0.23-0.46, p < 0.001, I2 = 87% ) was found for vein size. In conclusion, existing upper extremity exercise programs appear to be useful in facilitating maturation of AVFs created in distal region, while its effect on fistulas created in proximal region is less certain. However, more robust trials are warranted to establish these findings.

Exercise guide to help on arteriovenous fistula maturation and maintenance

BACKGROUND

The arteriovenous fistula is the main vascular access in hemodialysis. Arteriovenous fistula access is generally evaluated by a vascular surgeon after 2 weeks of its surgery, however, exercise programs may begin earlier for improving outcomes. Therefore, we propose this guide with simple, but potentially effective exercises, using low-cost materials that can be safely performed by the patients at home or in the dialysis center. It also provides to the dialysis staff team a starting point for implementing an upper-limb exercise program that may facilitate arteriovenous fistula maturation and maintenance.

METHODS

This exercise routine for arteriovenous fistula maturation can be performed three to four times a day, every day, from 2 to 4 weeks. After its maturation, it can be performed on every non-dialysis day for conventional treatment and every other day, before dialysis, for short daily treatment.

CONCLUSIONS

Based on the available evidence, we have gathered some exercises, in a very easy and understandable language, that may potentially help arteriovenous fistula maturation and maintenance for hemodialysis patients.

Effects of endothelial nitric oxide synthase on mouse arteriovenous fistula hemodynamics

Newly created arteriovenous fistulas (AVFs) often fail to mature for dialysis use due to disturbed blood flow at and near the AVF anastomosis. The disturbed flow inhibits the endothelial nitric oxide synthase (NOS3) pathway, thus decreasing the production of nitric oxide, a vasodilator. Previously, our group reported that NOS3 expression levels affect AVF lumen size in a mouse model. In this study, we performed MRI-based computational fluid dynamics simulations to investigate the hemodynamical parameters (velocity, wall shear stress (WSS), and vorticity) in a mouse AVF model at day 7 and day 21 post-AVF creation using three NOS3 strains: overexpression (OE), knockout (KO), and wild-type (WT) control. This study is the first to reveal hemodynamics over time in mouse AVFs, consider spatial heterogeneity along the vein, and reveal the effect of NOS3 on the natural history of mouse AVF hemodynamics. From day 7 to day 21, OE has smoother streamlines and had significantly lower vorticity and WSS than WT and KO, suggesting that WSS was attempting to return to pre-surgery baseline, respectively. Our results conclude that the overexpression of NOS3 leads to desired optimal hemodynamics during AVF remodeling. Future studies can investigate enhancing the NOS3 pathway to improve AVF development.

The reasons for comparative effectiveness clinical trials of arteriovenous fistula versus graft strategy in older adults on hemodialysis with a catheter

Clinicians and patients are guided by observational studies to make one of the most consequential decisions for patients with advanced kidney disease: the selection of the "right" hemodialysis vascular access. More than a decade ago, a call for randomized clinical trials was made to equitably compare clinical outcomes between arteriovenous (AV) fistulas (AVFs) and AV grafts (AVGs). Mounting evidence suggests that trade-offs between AVF- and AVGrelated outcomes are context dependent. In this article, we summarize four streams of evidence that collectively underpin the burden of equipoise between the two types of AV access in older adults with comorbidities who are on hemodialysis with a central venous catheter.

Inflow Artery Aneurysmal Degeneration After Long Term Native Arteriovenous Fistula for Haemodialysis

OBJECTIVE

Inflow arterial aneurysms are a rare but serious complication after long term arteriovenous fistulae (AVF), probably due to arterial wall remodelling after an increase in flow and shear stress, and kidney transplantation with immunosuppressive therapy. This study aimed to describe the outcomes of surgical treatment and long term follow up in a large cohort.

METHODS

This prospective cohort study collected data from patients with a true inflow artery aneurysm after AVF creation that was surgically repaired between 2010 and 2022. Anastomotic and infected aneurysms or post-puncture pseudoaneurysms were excluded. Demographic data, access characteristics, symptoms, treatment strategies, and long term follow up were recorded; patency was estimated using Kaplan-Meier survival analysis.

RESULTS

During the study period, 28 patients (64% men, mean age 60.1 years) were treated surgically for aneurysmal degeneration of the axillary or brachial (n = 23) or radial (n = 5) artery after an AVF (10 distal, 18 proximal) performed a mean of 18.3 ± SD 7.9 years previously. Most AVFs were ligated or thrombosed, while all patients except one had previously received kidney transplants. Most of the cases (n = 18) were symptomatic: 13 with pain or swelling, four with distal embolisation, and one rupture. They were repaired by aneurysm partial excision and graft interposition (11 great saphenous vein, six ipsilateral basilic vein, three cephalic vein, and two PTFE graft), ligation (n = 3), or direct end to end anastomosis (n = 3). No major complications occurred before discharge, after a mean hospital stay of 2.4 days. After a mean follow up of 4.8 ± 3.3 years, three cases presented complications: two recurrent proximal brachial aneurysms were repaired with an additional proximal interposition graft (one with further late infected pseudoaneurysm) and an asymptomatic post-traumatic graft thrombosis. Five year primary and secondary patency was 84% and 96%, respectively.

CONCLUSION

Aneurysmal degeneration of the inflow artery is an unusual complication during long term follow up of AVFs. Aneurysm excision and, in general, autogenous graft interposition using the saphenous or ipsilateral arm vein is a safe and effective strategy.

Transvenous Embolization of Dural Arteriovenous Fistulas Through the Galenic (Deep Venous) System: Multicenter Case Series and Meta-Analysis

BACKGROUND AND OBJECTIVES

Arteriovenous fistulas involving the deep venous system have often been treated with microsurgery or transarterial embolization. Increasing familiarity with transvenous navigation and improved endovascular access systems may facilitate transvenous embolization (TVE) for these rare and challenging lesions.

METHODS

We performed a retrospective study of neurointerventional databases of 6 high-volume centers. We identified all cases of arteriovenous fistulas with deep transvenous embolizations for arteriovenous fistula. Details regarding demographics, fistula characteristics, treatment considerations, clinical outcomes, and fistula occlusion were obtained and analyzed. The meta-analysis used the same inclusion criteria.

RESULTS

Seventeen cases of TVE were identified. The most common reasons for TVE included prior treatment failure with microsurgery (n = 2) or transarterial embolization (n = 3) or inaccessible arterial pedicles (n = 4). For patients with full clinical outcome data (n = 14), 2 patients had worsened modified Rankin Scale, 8 patients had no change, and 4 were improved at a median clinical follow-up of 3.5 months. Angiographic obliteration was achieved in 15/17 cases (88.2%). In 1 case, catheterization around a sharp turn in the basal vein of Rosenthal could not be performed. In another case, despite successful TVE, there was residual lesion which was treated 1 year later by microsurgical clipping and excision.

CONCLUSION

Transvenous approaches for embolization of deep arteriovenous fistulas have become possible with modern endovascular catheter systems and liquid embolics. These lesions can be treated safely and effectively through endovascular approaches, which may spare patients the traversal of deep structures needed for microsurgical approaches to these regions. The outcomes of TVE are comparable with published outcomes of microsurgical interruption.

Increased expression of the P2Y12 receptor is involved in the failure of autogenous arteriovenous fistula caused by stenosis

OBJECTIVE

This study investigated the role of the P2Y12 receptor in autogenous arteriovenous fistula (AVF) failure resulting from stenosis.

METHODS

Stenotic venous tissues and blood samples were obtained from patients with end-stage renal disease (ESRD) together with AVF stenosis, while venous tissues and blood samples were collected from patients with ESRD undergoing initial AVF surgery as controls. Immunohistochemistry and/or immunofluorescence techniques were utilized to assess the expression of P2Y12, transforming growth factor-β1 (TGF-β1), monocyte chemotactic protein 1 (MCP-1), and CD68 in the venous tissues. The expression levels of P2Y12, TGFβ1, and MCP-1 were quantified using quantitative reverse transcription-polymerase chain reaction and western blot analyses. Double and triple immunofluorescence staining was performed to precisely localize the cellular localization of P2Y12 expression.

RESULTS

Expression levels of P2Y12, TGFβ1, MCP-1, and CD68 were significantly higher in stenotic AVF venous tissues than in the control group tissues. Double and triple immunofluorescence staining of stenotic AVF venous tissues indicated that P2Y12 was predominantly expressed in α-SMA-positive vascular smooth muscle cells (VSMCs) and, to a lesser extent, in CD68-positive macrophages, with limited expression in CD31-positive endothelial cells. Moreover, a subset of macrophage-like VSMCs expressing P2Y12 were observed in both stenotic AVF venous tissues and control venous tissues. Additionally, a higher number of P2Y12+/TGF-β1+ double-positive cells were identified in stenotic AVF venous tissues than in the control group tissues.

CONCLUSION

Increased expression of P2Y12 in stenotic AVF venous tissues of patients with ESRD suggests its potential involvement in the pathogenesis of venous stenosis within AVFs.

Juan Bi Tang, a traditional Chinese medicine, for alleviating pain related to arteriovenous fistula in maintenance hemodialysis patients: An interventional pilot study with brief review

Myofascial pain around an arteriovenous fistula (AVF) during hemodialysis (HD) can affect a patient compliance with HD and quality of life. Prolonged use of analgesics is often associated with increased adverse events. Juan Bi Tang (JBT) is an ancient decoction of Chinese traditional medicinal plants commonly used to treat spasms and pain in the shoulder and upper arm, and it is popularly believed to have favorable outcomes in Asian populations. This interventional prospective pilot study was worked to demonstrate the potential of JBT for fistula-associated myofascial pain in HD patients and to prepare for future randomized controlled trials. Eligible patients were enrolled in this study and took JBT to treat fistula-associated myofascial pain for 4 weeks. Pain scores on a visual analogue scale (VAS) were reported at baseline, after a 4-week intervention, and 2 weeks after completion of treatment. The Kidney Disease Quality of Life 36-Item Short Form and a safety laboratory monitor were statistically compared between different time points. A total of 20 patients were selected as eligible participants and completed the intervention and questionnaires. The mean VAS score was significantly reduced after JBT treatment (P < .01). Participants reported improved physical (P < .01) and mental health (P < .05) after treatment. However, only improvements in mental health were preserved 2 weeks after the end of treatment (P < .05). In this study, complementary JBT for HD patients with fistula-related myofascial pain was viable and well tolerated, and it demonstrated the expected effects on pain control.

Perineural low dexamethasone dose as adjuvant in supraclavicular brachial plexus block for arteriovenous fistula creation in end stage renal disease: a randomized controlled trial

BACKGROUND AND AIMS

Dexamethasone as adjunct to local anesthetic solution improves the quality of brachial plexus block (BPB). However, evidence for its efficacy at low doses (< 4 mg) is lacking. This study was designed to evaluate the duration of analgesia attained with low dose dexamethasone as adjuvant to local anesthetic for creation of arteriovenous fistula (AVF) under BPB.

METHODS

Sixty-six patients scheduled for AVF creation were randomly allocated to receive either saline (control) or 2 mg dexamethasone, together with 0.5% ropivacaine and 0.2% lignocaine. The primary outcome was duration of analgesia, defined as time from performing the block to the first analgesic request. The secondary outcomes were time from injection to complete sensory block, time from injection to complete motor block, duration of motor block, postoperative analgesic consumption, and fistula patency at three months.

RESULTS

All the blocks were effective. In the group that received dexamethasone, the time to first analgesic request was significantly delayed (432 ± 43.8 minutes vs. 386.4 ± 40.2 minutes; p < 0.01). The onset of sensory and motor blockade occurred faster in dexamethasone group and overall analgesic consumption was also reduced. However, dexamethasone addition did not prolong the duration of motor block. There was no statistically significant difference in the patency of fistulas between the two groups at three months. (p = 0.34).

CONCLUSION

Addition of low-dose perineural dexamethasone to local anesthetic solution significantly prolonged the duration of analgesia. Further trials are warranted to compare the adverse effects between dexamethasone doses of 4 mg and lower.

Salvage of infected autogenous arteriovenous fistulas, is it possible?

BACKGROUND

Infection in autogenous arteriovenous fistulas (AVFs) is a critical situation in patients with end stage renal disease (ESRD) that can lead to life threatening rupture or septicemia. To date, no standard guidelines regarding the surgical repair of the infected AVFs is available.

AIM

To evaluate the safety and efficacy of the surgical repair in the infected autogenous AVFs.

METHODS

This prospective study involved 64 ESRD patients who presented with infected autogenous AVFs. Repair of the infected autogenous AVFs was done in 50 cases, while ligation was needed in the other 14 cases. Aneurysmorrhaphy was done in the 26 cases of puncture site infection over venous aneurysms. In 20 cases of AVFs with anastomotic disruption, higher recreation in a proximal clean field (AVF loop anastomosis) was performed, while abscess drainage was done in the remaining four cases presented with non-communicating abscess over the vein. The 14 cases of ligated AVFs included 9 cases of infected ruptured AVFs with active bleeding and 4 cases with non-reconstructable puncture site infection.

RESULTS

After 1 year of follow up, 41 cases (82%) of the repaired AVFs (n = 50) remained patent and functioning as re-infection occurred in 9 cases. Six tunneled permanent catheters were implanted in the 14 cases with ligated AVFs, while the remaining 8 cases had new AVFs established (7 cases of them retained patent AVFs during the follow up period).

CONCLUSION

Surgical repair of the infected AVFs is an effective procedure that achieves many goals, such as saving patients' lives, maintaining the patency of the native fistula, and avoidance of creation of new AVFs in another site with exhaustion the available veins.

Comparison of wound complications between one-stage and two-stage brachiobasilic arteriovenous fistula: A meta-analysis

Research assessing the outcome of brachiobasilic arteriovenous fistulas (BB-AVF) after a one- and two-stage technique was conducted. A strict review of the comprehensive literature up to May 2023 was carried out using four databases-PubMed，Embase, Cochrane Library and web of science. Inclusion and exclusion criteria developed for the study were then applied to assess the quality of the literature, it was decided to review 12 interrelated studies.95% confidence intervals (Cl) and odds ratios (OR) were calculated using fixed effects models. The data were meta-analysed using RevMan 5.3 software. The results showed that two-stage technique with BB-AVF reduced surgical site haematoma (SSH) formation, (OR, 2.28; 95% CI, 1.24-4.17, p = 0.008), and also reduced surgical site wound infection (SSWI) (OR, 1.86; 95% CI, 1.17-2.94, p = 0.008). There are, however, several small sample sizes in the selected studies for this meta-analysis, so caution should be used when processing their values. There are more high-quality studies with large sample sizes that should be considered for future meta-analyses.

Anesthetic effect of ultrasound-guided block of the musculocutaneous nerve during endovascular treatment of dysfunctional radiocephalic arteriovenous fistulas

BACKGROUND

Delivering requisite and minimal anesthesia for endovascular treatment (EVT) of dysfunctional arteriovenous fistulas (AVFs) under the target nerve block can achieve reasonable analgesia. We evaluated the anesthetic efficacy of ultrasound (US)-guided selective block of the musculocutaneous nerve (MCN) during the EVT of runoff venous strictures in the forearm through the radiocephalic (RC)-AVF at the wrist or the anatomical snuff box and analyzed the factors inhibiting the analgesia achieved under the MCN block.

METHODS

We enrolled 30 adult patients undergoing hemodialysis who had received 78 EVT sessions in an outpatient clinic mainly for long and/or multiple outflow-venous strictures in the forearm under US-guided blocks of the MCN, which provides sensory innervation to the anterolateral forearm where the cephalic vein courses. We assessed patients' pain during balloon dilations using the Wong-Baker FACES® Pain Rating Scale (WBFRS) and evaluated the factors increasing the pain (WBFRS score ⩾4), including patient characteristics, dilated strictures, additional nerve blocks, and types of balloon catheters.

RESULTS

In 25 EVT sessions (32.1%) out of 78 sessions, patients complained of stronger pain (WBFRS score ⩾4), while in the other 53 sessions (67.9%), presented with no pain and slight pain (WBFRS score = 0 or 2). Univariate analysis clarified that dilation of the AVF anastomosis, presence of dilated stenosis >4 cm, and a single block of the MCN or its sensory terminal significantly triggered more pain (p < 0.05). Consequently, multivariate analysis of all the factors with p < 0.1 in the univariate analysis, including multiple dilated stenosis sites, demonstrated that dilation of the AVF anastomosis significantly caused severe pain despite the anesthesia of the MCN block (p < 0.05).

CONCLUSION

US-guided selective block of the MCN could be a leading anesthetic option for EVT for multiple long stenoses of the cephalic vein draining through the RC-AVF in the wrist or anatomical snuff box.

Automated 3D ultrasound enables novice users to measure arteriovenous fistula maturation parameters with comparable accuracy to conventional duplex by trained sonographers: Results of a benchtop study

BACKGROUND

Arteriovenous fistulae (AVF) are considered the preferred hemodialysis access but up to 50% of all AVF created in the United States never mature. Doppler ultrasound (DUS) is useful for predicting fistula maturity and impending fistula failure. DUS is resource-intensive and is associated with poor compliance rates in dialysis patients, ranging from 12% to 33%.

METHODS

EchoSure is an FDA-cleared 3D Doppler ultrasound device that automatically delivers quantitative blood flow and anatomic vascular information. The technology can be used at the bedside by personnel without formal sonographic training, nullifying limitations of traditional Duplex ultrasound imaging. This study compared the EchoSure system in the hands of inexpert personnel to a traditional expert-operated DUS for rapid assessment of a benchtop model vascular system with flow, diameter, and depth expected in a human AVF.

RESULTS

Both Duplex and EchoSure performed within the expected tolerance of ultrasound readings (35%) for volume flow, with the average error (AE) between the observed measurement and the ground truth being 8% for Duplex and 8% for EchoSure. However, the average coefficient of variation (CV) for Duplex pooled over all flow rate measurements was 17% versus 4% for EchoSure. Regarding diameter, Duplex measurements had AE of 15% with an average CV of 6% across all measurements versus EchoSure AE of 4% and average CV of 2%. Duplex and EchoSure measurements over all depths had the same AE of 2%. The two modalities were not statistically different for depth measurement (p = 0.05) but EchoSure measured closer to the ground truth for flow rate and vessel diameter (flow: p = 0.028, ρ = -0.07; diameter: p < 0.001, ρ = 0.69). The inexpert personnel using EchoSure acquired data 62% faster than the expert sonographers using the Duplex ultrasound (141 min for Duplex vs 87 min for EchoSure).

CONCLUSIONS

EchoSure may offer an accurate and convenient alternative for imaging fistulas in the clinic.

A new hope for vascular access, modifying a new technique: The Surfacer® Inside-Out Access Catheter System and sharp recanalization

Vascular access (VA) for hemodialysis (HD) continues to be the keystone of the technique's success. The first option should be an arteriovenous fistula (AVF) or arteriovenous graft (AVG), although in some scenarios the only possibility available is a central venous catheter, which could lead to an increase in vascular complications such as thoracic central vein occlusion (TCVO), becoming a challenge for physicians. If conventional therapies cannot be performed, a new device called the Surfacer® Inside-Out® Access Catheter System (IOA) (Bluegrass Vascular Technologies, San Antonio, TX, USA) arises as a promising alternative. Here we describe the case of a patient in which we performed a combination of two techniques: sharp recanalization plus Surfacer® Inside-Out® Access Catheter System.

Predictors of Arteriovenous Fistula Maturation among Patients with Severe Obesity

BACKGROUND

There is an increasing prevalence of obesity among patients who develop end-stage renal disease and require dialysis. While referrals for arteriovenous fistulas (AVFs) among patients with class 2-3 obesity (i.e., body mass index [BMI] ≥ 35) are increasing, it is unclear what type of autogenous access is most likely to mature in this patient population. This study was designed to evaluate factors that impact maturation of AVF among patients with class ≥2 obesity.

METHODS

We retrospectively reviewed AVFs created at a single center from 2016 to 2019 for patients who had undergone dialysis within the same healthcare system. Ultrasound studies were used to evaluate factors that defined functional maturation, including diameter, depth, and volume flow rates through the fistula. Logistic regression models were used to evaluate the risk-adjusted association between class ≥2 obesity and functional maturation.

RESULTS

A total of 202 AVFs [radiocephalic (24%), brachiocephalic (43%), and transposed brachiobasilic (33%)] were created during the study period, of which 53 (26%) patients had a BMI >35. Functional maturation was significantly lower among patients with class ≥2 obesity undergoing brachiocephalic (58% obese versus 82% normal-overweight; P = 0.017), but not radiocephalic or brachiobasilic AVFs. This was primarily a result of excessive AVF depth in severely obese patients (9.6 ± 4.0 mm obese versus 6.0 ± 2.7 mm normal-overweight; P < 0.001), whereas there was no significant difference found in average volume flow or AVF diameter between groups. In risk-adjusted models, a BMI ≥35 was associated with a significantly lower likelihood of achieving AVF functional maturation (odds ratio: 0.38; 95% confidence interval: 0.18-0.78; P = 0.009) after controlling for age, sex, socioeconomic status, and fistula type.

CONCLUSIONS

Patients with a BMI >35 are less likely to mature AVFs after creation. This principally affects brachiocephalic AVFs and occurs because of increased fistula depth as opposed to diameter or volume flow parameters. These data can help guide decision-making when planning AVF placement in severely obese patients.

Hybrid Revision of Dysfunctional Aneurysmal Arteriovenous Fistulas

Endovascular therapy has become the first-line treatment for failing hemodialysis arteriovenous fistulas (AVFs). However, open revision remains an important modality for vascular access maintenance and the recommended approach for AVF aneurysms. This case series describes a hybrid approach for aneurysmal access revision. Three patients were referred for second opinion after failure of endovascular therapy to establish a functioning access. The medical history is briefly described to highlight the limitations of endovascular therapy and the technical advantages of the hybrid approach in these clinical scenarios.

A snapshot of early venous remodeling in a 7-day-old arteriovenous fistula

Early remodeling of the arteriovenous fistula (AVF) determines maturation outcomes. However, the cellular response of the venous wall early after AVF creation remains largely enigmatic because of the lack of venous biopsies obtained shortly after anastomosis. This report presents a detailed immunohistochemistry analysis of a pre-access cephalic vein and the resulting seven-day-old AVF that required ligation due to steal syndrome. We test for markers of mature and progenitor endothelial cells (CD31, CD34, VWF), contractile smooth muscle cells and myofibroblasts (MYH11, SMA), and immune cell populations (CEACAM8, CD3, CD20, CD11b, CD45, CD68, CD163, tryptase). We demonstrated near complete endothelial coverage of the fistula at 7 days, a high degree of wall neovascularization, pronounced loss of myofibroblasts and smooth muscle cells, and significant infiltration of mast cells, neutrophils, monocytes, and macrophages. Of interest, the presence of CD163+ macrophages in the AVF suggests a reactive response to increased intramural oxygenation. In conclusion, these images provide for the first time a glimpse of early remodeling in a human AVF by immunohistochemistry. This case demonstrates the possibility to obtain additional precious samples of this early stage through future multicenter collaborative efforts.