Vascular access in haemodialysis: strengthening the Achilles' heel

Fibroblast growth factor 21 predicts arteriovenous fistula functional patency loss and mortality in patients undergoing maintenance hemodialysis

BACKGROUND

Arteriovenous fistula (AVF) dysfunction is a common complication in patients undergoing maintenance hemodialysis (MHD). Elevated serum levels of fibroblast growth factor 21 (FGF21) are associated with atherosclerosis and cardiovascular mortality. However, its association with vascular access outcomes remains elusive. The present study evaluated the relationship of serum FGF21 levels with AVF dysfunction and all-cause mortality in patients undergoing MHD.

METHODS

We included patients undergoing MHD using AVF from January 2018 to December 2019. FGF21 concentration was detected using enzyme-linked immunosorbent assay. Patients were followed up to record two clinical outcomes, AVF functional patency loss and all-cause mortality. The follow-up period ended on April 30, 2022.

RESULTS

Among 147 patients, the mean age was 58.49 ± 14.41 years, and the median serum level of FGF21 was 150.15 (70.57-318.01) pg/mL. During the median follow-up period of 40.83 months, the serum level of FGF21 was an independent risk factor for AVF functional patency loss (per 1 pg/mL increase, HR 1.002 [95% CI: 1.001-1.003, p = 0.003]). Patients with higher serum levels of FGF21 were more likely to suffer from all-cause mortality (per 1 pg/mL increase, HR 1.002 [95% CI: 1.000-1.003, p = 0.014]). The optimal cutoffs for FGF21 to predict AVF functional patency loss and all-cause mortality in patients undergoing MHD were 149.98 pg/mL and 146.43 pg/mL, with AUCs of 0.701 (95% CI: 0.606-0.796, p < 0.001) and 0.677 (95% CI: 0.595-0.752, p = 0.002), respectively.

CONCLUSIONS

Serum FGF21 levels were an independent risk factor and predictor for AVF functional patency loss and all-cause mortality in patients undergoing MHD.

Association of anesthetic modality and other variables on 1-year functional patency of cephalic-based arteriovenous fistulae

OBJECTIVE

Some studies suggest that regional anesthesia provides better patency for arteriovenous fistula (AVF) for hemodialysis access as compared to local and general anesthesia. This study evaluates the impact of anesthetic modality on long term fistula function at 12 months.

METHODS

A retrospective review of patients undergoing cephalic vein-based hemodialysis access in consecutive cases between 2014 and 2019 was conducted from five safety net hospitals. The primary endpoint was functional patency at 12 months. Subset analysis individually evaluated cephalic-based lower forearm and wrist vs upper arm AVFs. Bivariate and multivariate logistic regression models evaluated the relationship between anesthetic modality and fistula function at 12 months.

RESULTS

There were 818 cephalic-based fistulas created during the study period. The overall 12-month functional patency rate was 78.7%, including an 81.3% patency for upper arm AVF and 73.3% for wrist AVF (P = .009). There was no statistically significant difference among patients with functional and nonfunctional AVFs at 12 months with respect to anesthetic modality when comparing regional, local, and general anesthesia (P = .343). Multivariate regression analysis identified that history of AVF/arteriovenous graft (odds ratio [OR], 0.24; P = .007), receiving intraoperative systemic anticoagulation (OR, 2.49; P < .001), and vein diameter (OR, 1.85; P = .039) as independently associated with AVF functional patency at 12 months.

CONCLUSIONS

There was no association between anesthetic modality and functional patency of cephalic-based AVFs at 12 months. Further studies are needed to better define which patients may benefit from regional anesthesia.

Safety and Performance of a Cell-Impermeable Endoprosthesis for Hemodialysis Vascular Access Outflow Stenosis: A Brazilian Multicenter Retrospective Study

PURPOSE

To evaluate the safety and performance of Wrapsody™, a cell-impermeable endoprosthesis (CIE), for treating hemodialysis vascular access outflow stenosis.

MATERIALS AND METHODS

Investigators retrospectively analyzed 113 hemodialysis patients treated with a CIE (11/2021-12/2022) across four centers in Brazil. De novo or restenotic lesions were treated. The primary efficacy outcome measure was target lesion primary patency (TLPP) at 1, 3, 6, and 12 months; the primary safety outcome measure was the absence of serious local or systemic adverse events within the first 30 days post-procedure. Secondary outcome measures included technical and procedural success, access circuit primary patency (ACPP), and secondary patency at 1, 3, 6, and 12 months post-procedure.

RESULTS

Thirty-nine patients (34.5%) had thrombosed access at the initial presentation, and 38 patients (33.6%) presented with recurrent stenosis. TLPP rates at 1, 3, 6, and 12 months were 100%, 96.4%, 86.4%, and 69.7%, respectively. ACPP rates were 100% at 1 month, 89.2% at 3 months, 70.9% at 6 months, and 56.0% at 12 months. The target lesion secondary patency rates at 1, 3, 6, and 12 months were 100%, 97.3%, 93.6%, and 91.7%, respectively. In the adjusted multivariate Cox regression analysis, male sex and endoprosthesis with diameters of 10, 12, 14, and 16 mm were associated with improved primary patency rates. No localized or systemic serious adverse event was observed through the first 30 days post-procedure.

CONCLUSION

The CIE evaluated in this study is safe and effective for treating peripheral and central outflow stenoses in hemodialysis vascular access.

LEVEL OF EVIDENCE

Level 2b, cohort study.

Lumen diameter is associated with the patency after percutaneous angioplasty of arteriovenous fistulas

AIM

To assess the value of lumen diameter after percutaneous angioplasty (PTA) to predict functional dialysis use (FDU) of arteriovenous fistulas (AVF).

METHODS

We performed a retrospective study of all patients who underwent first PTA because of AVF stenosis between March 2019 and March 2021. The outcome was FDU of AVF at 6 months follow up. Independent factors of FDU were identified using multivariate regression analyses. Receiver operating characteristic (ROC) curve was performed to investigate the predictive ability of lumen diameter for FDU.

RESULTS

A total 68 patients were included into this study and the AVF of 53 cases (77.9%) were good for FDU after 6 months. The AVF age was younger in failure group than that in success group (16.1 ± 9.1 months vs 28.3 ± 20.0 months, p = 0.026). Compared with failure group, the post-PTA minimum luminal diameter (MLD) was bigger in success group (4.5 [4.0-4.5 mm] vs 5.5 mm [4.5-5.5 mm], p < 0.001). Meanwhile, the gain of lumen diameter in success group was also bigger than that in failure group (2.5 mm [2.0-3.0 mm] in failure group vs 3.0 mm [2.75-3.5 mm] in success group, p = 0.012). The residual stenosis was higher in failure group than that in success group (30% [10%-40%] vs 10% [0%-20%], p = 0.003). Logistic regression showed that AVF age and post-PTA MLD were independent predictors of FDU. ROC analysis showed that the gain of lumen diameter, post-PTA MLD and improvement of stenosis were comparable to predict FDU. For post-PTA MLD, the area under ROC curve was 0.804 (95% CI, 0.681-0.927, p < 0.001). The best cutoff is 4.75 mm, with the sensitivity and specificity was 71.7% and 80.0%, respectively.

CONCLUSIONS

AVF age and post-PTA MLD were independently predictors for FDU of AVF after PTA. To get the best performance, a minimum vein diameter of 4.75 mm should be obtained after angioplasty.

Knowledge of arteriovenous fistula care in patients with end-stage kidney disease in south Asian countries: A systematic review and meta-analysis

OBJECTIVES

To find the prevalence of knowledge of arteriovenous fistula (AVF) self-care, its characteristics, and associated factors among hemodialysis patients and summarize the findings of various domains of AVF self-care in south Asian countries.

METHODS

The systematic literature search was performed on online databases and additional sources to retrieve published articles on AVF self-care. We estimated the pooled prevalence using a random effects model in meta-analysis. Additionally, thematic knowledge regarding various aspects of AVF self-care was narratively summarized.

RESULTS

Among the articles retrieved seven studies met our inclusion and exclusion criteria. The prevalence of AVF self-care in individual studies ranged from 59% to 99%, with an overall random pooled prevalence of 81% (95% CI, 68% to 94%). Major factors associated with self-care of AVF knowledge included patients' educational status, age, vintage of hemodialysis, and healthcare personnel's advice.

DISCUSSION

Knowledge scarcity regarding potential measures of AVF self-care obligates the need for continuous education in hemodialysis patients. A multidisciplinary approach is vital to enhance self-care from pre- to post-creation of AVF in hemodialysis patients as well as their caregivers in order to prolong the patency rates and decrease the subsequent morbidity and mortality due to failure of AVF.

Safety and efficacy of a new covered stent in hemodialysis vascular access outflow stenosis: A Brazilian multicenter retrospective study

BACKGROUND

Vascular stenosis commonly leads to dysfunction in hemodialysis vascular access. Although percutaneous transluminal angioplasty is an established treatment, stent utilization has increased in the last decade as an alternative solution to extend the access function. This study evaluated the safety and initial results of a new impermeable covered stent for treating vascular access outflow stenosis.

METHODS

Investigators retrospectively analyzed 114 hemodialysis patients treated with polytetrafluorethylene-covered stents from September 2018 to September 2022 across four centers. Lesions treated were de novo or restenotic and located in the venous graft anastomosis, outflow segment, cephalic arch, and basilic swing point. Patients were followed by in-person physical examination at 1, 3, and 6 months, and Duplex ultrasound was performed to evaluate the vascular access circuit and in-stent restenosis. The primary efficacy endpoint was target lesion primary patency at 1, 3, and 6 months. Secondary endpoints included access circuit primary patency and secondary patency at 1, 3, and 6 months. The primary safety endpoint was freedom from local or systemic serious adverse events through 30 days post-procedure.

RESULTS

Forty-four patients had thrombosed access at the initial presentation, and 41 patients presented with recurrent stenosis. The target lesion primary patency rates at 1, 3, and 6 months were 100%, 89.4%, and 74%, respectively. The access circuit primary patency rates were 100% at 1 month, 85% at 3 months, and 62.7% at 6 months. The secondary patency rates at 1, 3, and 6 months were 100%, 96.4%, and 94.6%, respectively. In the adjusted multivariate Cox regression analysis, only recurrent lesions and female gender were associated with reduced primary patency rates. No serious adverse event was observed through the first 30 days post-procedure.

CONCLUSION

In this retrospective analysis, a new covered stent was shown to be safe and effective for treating peripheral outflow stenosis in vascular access.

Hemodialysis Access: US for Preprocedural Mapping and Evaluation of Maturity and Access Dysfunction

Patients with kidney failure require kidney replacement therapy. While renal transplantation remains the treatment of choice for kidney failure, renal replacement therapy with hemodialysis may be required owing to the limited availability and length of time patients may wait for allografts or for patients ineligible for transplant owing to advanced age or comorbidities. The ideal hemodialysis access should provide complication-free dialysis by creating a direct connection between an artery and vein with adequate blood flow that can be reliably and easily accessed percutaneously several times a week. Surgical arteriovenous fistulas and grafts are commonly created for hemodialysis access, with newer techniques that involve the use of minimally invasive endovascular approaches. The emphasis on proactive planning for the placement, protection, and preservation of the next vascular access before the current one fails has increased the use of US for preoperative mapping and monitoring of complications for potential interventions. Preoperative US of the extremity vasculature helps assess anatomic suitability before vascular access creation, increasing the rates of successful maturation. A US mapping protocol ensures reliable measurements and clear communication of anatomic variants that may alter surgical planning. Postoperative imaging helps assess fistula maturation before cannulation for dialysis and evaluates for early and late complications associated with arteriovenous access. Clinical and US findings can suggest developing stenosis that may progress to thrombosis and loss of access function, which can be treated with percutaneous vascular interventions to preserve access patency. Vascular access steal, aneurysms and pseudoaneurysms, and fluid collections are other complications amenable to US evaluation. ©RSNA, 2023 Supplemental material is available for this article. Test Your Knowledge questions for this article are available through the Online Learning Center.

Long-term mortality and patency after drug-coated balloon angioplasty in the hemodialysis circuit: A systematic review and meta-analysis of randomized controlled trials

PURPOSE

To compare all-cause mortality and primary patency with drug-coated balloon angioplasty (DCBA) compared with plain balloon angioplasty (PBA) in people with hemodialysis-related stenosis.

MATERIALS AND METHODS

PubMed, Embase, and Cochrane Library databases were searched from November 1966 to February 2021 to identify randomized controlled trials (RCTs) that assessed the use of DCBA versus PBA for stenosis in hemodialysis circuits. Data extracted from the articles were integrated to determine all-cause mortality, target lesion primary patency (TLPP), circuit access primary patency (CAPP), 30-day adverse events, and technical success for the two approaches. We performed meta-analysis on these results using a fixed-effects model to evaluate odds ratios (ORs) and 95% confidence intervals (CIs) where I2 < 50% in a test for heterogeneity, or a random-effect model if otherwise. Sensitivity and subgroup analyses were also performed.

RESULTS

Sixteen RCTs of 1672 individuals were included in our meta-analysis, of which 839 individuals received DCBA and 833 received PBA. The pooled outcome showed no statistical difference between DCBA and PBA in all-cause mortality at 6 months (OR = 1.29, 95% CI = 0.72-2.32, p = 0.39, I2 = 4%), 12 months (OR = 1.02, 95% CI = 0.68-1.53, p = 0.91, I2 = 0%), and 24 months (OR = 1.50, 95% CI = 0.87-2.57, p = 0.15, I2 = 0%), 30-day adverse events (OR = 1.09, 95% CI = 0.30-3.98, p = 0.90, I2 = 66%), and technical success (OR = 0.18, 95% CI = 0.02-1.92, p = 0.16, I2 = 65%). The DCBA had significantly better outcomes versus PBA in TLPP at 6 months (OR = 2.37, 95% CI = 1.84-3.04, p < 0.001, I2 = 44%) and 12 months (OR = 1.77, 95% CI = 1.22-2.56, p = 0.002, I2 = 56%), and CAPP at 6 months (OR = 2.07, 95% CI = 1.21-3.54, p = 0.008, I2 = 67%) and 12 months (OR = 1.66, 95% CI = 1.29-2.15, p < 0.001, I2 = 0%).

CONCLUSION

In hemodialysis circuit stenosis, DCBA appears to have similar safety but greater efficacy than PBA.

A Comparative Study of Continuous Versus Interrupted Suturing Technique in Creating a Vascular Access for Hemodialysis: An Institutional-Based Experience

Background Arteriovenous fistulas (AVFs) are considered the first and best access for patients with end-stage renal disease who need permanent vascular access for hemodialysis over arteriovenous grafts and central venous catheters for reasons that have been well-established. Poor early patency rates pose the biggest challenge in creating vascular access as they cause increased morbidity and economic/psychological concerns among patients. To minimize such effects, it is critical to use a patient-centered approach and carefully choose patients for AVF access creation. This study aimed to compare the primary patency of distal vascular access provided by continuous suturing versus that provided by interrupted suturing. Methodology This prospective study was conducted in the urology department of a superspecialty, tertiary care center from November 2021 to November 2022. Patency was assessed immediately after surgery (on the table), one month later, and six months later by palpating thrill and auscultating bruit. A total of 50 patients between the ages of 18 and 70 years who met the inclusion criteria were randomly assigned to two groups of 25 each. Results The baseline characteristics of both groups were comparable. At six months (p = 0.09), the continuous suturing group was observed to be somewhat better than the interrupted suturing group, with no significant difference in immediate and one-month patency rates. When compared to the continuous suturing group, the primary patency failure rate was significantly higher in the interrupted suturing group. Conclusions Thus, under appropriate circumstances, continuous sutures can be performed with greater ease, resulting in anastomosis that is as patent as that performed with interrupted sutures.

The role of stents in hemodialysis vascular access

Vascular access is the Achilles' heel of dialysis therapy among patient with end stage kidney disease. The development of neointimal hyperplasia and subsequent stenosis is common in vascular access and is associated with significant morbidity. Percutaneous transluminal angioplasty using balloon inflation was the standard therapy of these lesions. However, the balloon-based approaches were associated with poor vascular access patency rate necessitating new inventions. It is within this context that different types of stents were developed in order to improve the overall dialysis vascular access functionality. In this article, we review the available literature regarding the use of stents in treating dialysis vascular access stenotic lesions. Further, we review the major clinical trials of stent use in different anatomic locations and in different clinical scenarios.

Health insurance provider and endovascular treatment availability are associated with different hemodialysis vascular access profiles: A Brazilian national survey

In Brazil, most hemodialysis (HD) patients are treated by the country's public health system. However, accessibility to healthcare is different for public and private patients. This study aimed to identify the profile of vascular access in a Brazilian HD sample. Additionally, it aimed to examine the influence of public and private health insurance, accessibility to endovascular treatments, and timely arteriovenous access creation on the prevalence of tunneled catheters (TCs), non-tunneled catheters (NTCs), and arteriovenous (AV) access. We conducted a cross-sectional electronic survey across 834 centers. Centers were inquired about the number of patients with public and private health insurance, the profiles of vascular access, time for AV access creation, accessibility to TC insertion and endovascular treatments, and the availability of peritoneal dialysis and kidney transplantation. Logistic regression and multilevel logistic regression were performed to evaluate possible interactions between the independent variables. A total of 7,973 patients across 47 HD centers were included in the survey. Public health patients accounted for 77% of the study sample. The overall vascular access profiles of the public and private insurance groups were significantly different (p < 0.001). For patients with public health insurance, the prevalence of any catheter was 25%, while that for private patients was 31.8% (p < 0.001). The prevalence of TCs was more common in private patients (15.3% vs. 23.1%, p < 0.001). AV accesses were more common in public health patients (75% vs. 68.2%, p < 0.001), as were fistulas (72.4% vs. 63.1%, p < 0.001). AV grafts were more prevalent among patients with private insurance (2.6 vs. 5.1%, p < 0.001). The availability of endovascular treatments increased the chance of having a TC by 2.3-fold (OR = 2.33, 95% CI = 1.30-4.18); however, it did not reduce the chance of having any catheter. A high chance of having a catheter was found when the time to AV access creation exceeded 60 days. The differences between public and private patients may be explained by underpayments and the decreased accessibility to care infrastructure in the public system, especially for endovascular treatments. In this sample, public health patients had a decreased risk of having a TC over an NTC. Differences in care accessibility and insurance type might influence the type of vascular access.

[Contribution of hemostatic dressings in the hemostasis of arteriovenous fistula? A quality improvement program in our center]

INTRODUCTION

In haemodialysis patients the length of bleeding times after fistula cannulation is an easy and fairly used method of monitoring vascular access. In the most cases, compression is performed manually by nurses and the use of haemostatic dressing is common. As data in the literature are scares, we have decided to develop a quality improvement program in our hemodialysis center to manage this issue.

MATERIAL AND METHODS

After informed consent, 35 hemodialysis outpatients were selected in order to study the bleeding time using haemostatic dressing or not during two weeks in a cross over schema. The dialysis schedule was unchanged and comparative analysis of parameters such as blood flow rate or anticoagulant treatment were done between the groups.

RESULTS

Compression times with and without hemostatic dressing were not different (12.6 min and 12.9 min, respectively). Patients with an anticoagulation during the dialysis session greater than 0.35 IU/kg/session had a longer bleeding time (12.75 min vs 11.75 min; P=0.008).

CONCLUSION

In our evaluation, the use of haemostatic dressings is not associated with a real shorter bleeding time. Their use generate an additional cost estimated on average at 164 euros/year/patient. Patients and team realized that compression time is important for fistula monitoring and using compresses does not really increase this time.

Oxidative stress: An essential factor in the process of arteriovenous fistula failure

For more than half a century, arteriovenous fistula (AVFs) has been recognized as a lifeline for patients requiring hemodialysis (HD). With its higher long-term patency rate and lower probability of complications, AVF is strongly recommended by guidelines in different areas as the first choice for vascular access for HD patients, and its proportion of application is gradually increasing. Despite technological improvements and advances in the standards of postoperative care, many deficiencies are still encountered in the use of AVF related to its high incidence of failure due to unsuccessful maturation to adequately support HD and the development of neointimal hyperplasia (NIH), which narrows the AVF lumen. AVF failure is linked to the activation and migration of vascular cells and the remodeling of the extracellular matrix, where complex interactions between cytokines, adhesion molecules, and inflammatory mediators lead to poor adaptive remodeling. Oxidative stress also plays a vital role in AVF failure, and a growing amount of data suggest a link between AVF failure and oxidative stress. In this review, we summarize the present understanding of the pathophysiology of AVF failure. Furthermore, we focus on the relation between oxidative stress and AVF dysfunction. Finally, we discuss potential therapies for addressing AVF failure based on targeting oxidative stress.

Association of Permanent Vascular Access Dysfunction with Subsequent Risk of Cardiovascular Disease: A Population-Based Cohort Study

A functional permanent vascular access (VA) is required to perform a successful hemodialysis procedure. Hemodialysis VA dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population. Cardiovascular disease (CVD) is the leading cause of death in patients receiving chronic hemodialysis. Information about CVD associated with hemodialysis VA dysfunction is unclear. We analyzed the association between dialysis VA dysfunction and the risk of developing CVD in hemodialysis patients. This nationwide population-based cohort study was conducted using data from the National Health Insurance Research Database in Taiwan. One million subjects were sampled from 23 million beneficiaries and data was collected from 2000 to 2013. Patients with end-stage renal disease who had received permanent VA construction and hemodialysis and were aged at least 20 years old from 2000 to 2007 were included in the study population. The primary outcome was CVD, as defined by ICD-9-CM codes 410–414 and 430–437. A total of 197 individuals with permanent VA dysfunction were selected as the test group, and 100 individuals with non-permanent VA dysfunction were selected as the control group. Compared with the control group, the adjusted hazard ratio of CVD for the VA dysfunction group was 3.05 (95% CI: 1.14–8.20). A Kaplan–Meier analysis revealed that the cumulative incidence of CVD was higher in the permanent VA dysfunction group than in the comparison group. Permanent VA dysfunction is significantly associated with an increased risk of subsequent CVD.

Evaluation of simulation models in neurosurgical training according to face, content, and construct validity: a systematic review

BACKGROUND

Neurosurgical training has been traditionally based on an apprenticeship model. However, restrictions on clinical exposure reduce trainees' operative experience. Simulation models may allow for a more efficient, feasible, and time-effective acquisition of skills. Our objectives were to use face, content, and construct validity to review the use of simulation models in neurosurgical education.

METHODS

PubMed, Web of Science, and Scopus were queried for eligible studies. After excluding duplicates, 1204 studies were screened. Eighteen studies were included in the final review.

RESULTS

Neurosurgical skills assessed included aneurysm clipping (n = 6), craniotomy and burr hole drilling (n = 2), tumour resection (n = 4), and vessel suturing (n = 3). All studies assessed face validity, 11 assessed content, and 6 assessed construct validity. Animal models (n = 5), synthetic models (n = 7), and VR models (n = 6) were assessed. In face validation, all studies rated visual realism favourably, but haptic realism was key limitation. The synthetic models ranked a high median tactile realism (4 out of 5) compared to other models. Assessment of content validity showed positive findings for anatomical and procedural education, but the models provided more benefit to the novice than the experienced group. The cadaver models were perceived to be the most anatomically realistic by study participants. Construct validity showed a statistically significant proficiency increase among the junior group compared to the senior group across all modalities.

CONCLUSION

Our review highlights evidence on the feasibility of implementing simulation models in neurosurgical training. Studies should include predictive validity to assess future skill on an individual on whom the same procedure will be administered. This study shows that future neurosurgical training systems call for surgical simulation and objectively validated models.

Weight-Based Assessment of Access Flow Threshold to Predict Arteriovenous Fistula Functional Patency

Introduction

The 2019 Kidney Disease Outcome Quality Initiative (K/DOQI) guideline recommended evaluating arteriovenous fistula (AVF) malfunction risks primarily based on clinical monitoring, which can be assisted with the value of vascular access flow (Qa). Nevertheless, Qa thresholds recommended by different guidelines vary, ranging from 300 to 500 ml/min. This study investigated the optimal Qa threshold to predict future functional patency in AVFs with Qa <500 ml/min.

Methods

Both the clinical indicators of access dysfunction and the Qa value were monitored in patients receiving hemodialysis by the radiocephalic AVF. Routine access flow surveillance was performed by the ultrasound dilution method (HD03, Transonic Inc.). The development of clinically significant indicators of access dysfunction, which necessitated percutaneous transluminal angiography (PTA) to maintain functional patency, was analyzed in this cohort.

Results

Among the enrolled 302 patients, Qa of 52 patients was under 500 ml/min. These 52 patients received 2 Qa measurements during the follow-up period. Of these 52 patients, serial Qa of 17 patients varied trivially and their AVF remained functional. Multivariable logistic regression analysis revealed that a low Qa per ideal body weight (IBW) is an independent predictor of AVF functional loss. Receiver operating characteristic curve analysis of Qa/IBW in predicting future AVF functional loss revealed that the best cutoff value of Qa is 7.1 times the IBW.

Conclusion

For radiocephalic AVFs with Qa <500 ml/min, the minimally required Qa to maintain access function is associated with individual IBW. The IBW-based Qa threshold assessment would allow more flexibility in the treatment of patients and reduce unnecessary invasive measures.

Procedure and Clinical Success of Drug-Coated Balloon Fistuloplasty of the Drainage Vein in Dysfunctional Native Arteriovenous Fistulas

Purpose

Native arteriovenous fistulas (AVFs) are the most effective vascular access (VA) for haemodialysis. We aimed to evaluate the results of balloon angioplasty (fistuloplasty) from drainage vein performed for the treatment of AVF dysfunction in haemodialysis patients and examine potential patient and AVF-associated factors that might affect such results.

Methods

This is a nonrandomized, retrospective, and single-centred study. A total of 105 balloon fistuloplasties were performed for dysfunctional AVFs of 82 haemodialysis patients. Patients were treated with a drug-coated balloon according to standard procedures. Evaluations were performed by physical examinations and if needed by color Doppler imaging in every 6 months. The primary endpoint was patency by balloon fistuloplasty. Patency was evaluated clinically by detecting the thrill in AVF and by the adequacy of the dialysis. Multidimensional scaling (MDS) technique was used as a method for the statistical analysis.

Results

The success of the procedure after the first attempt was 85.3% with 70 patients. Patency in the 6th, 12th, 18th, and 24th months were 63 (76.8%), 60 (73.1%), 53 (64.6%), and 44 (54%), respectively. The procedure was considered successful when the thrill was detected in AVF and when dialysis was adequate. The statistical analysis by MDS revealed that patients' age was the most effective factor acting on the procedure success followed by the age of AVF. Other patient-associated and AVF-associated factors were not found as effective statistical evaluation.

Conclusions

Haemodialysis through native AVFs with restored functionality contributes positively to the life span and the quality of life of the patient. Probably, advanced age and high fistula age are unfavourable factors leading to the development of neointimal hyperplasia and venous stenosis. Balloon fistuloplasty of the draining vein is an effective and safe method regardless of patient age and the age of AVF.

Receiver operating characteristic curve analysis of arteriovenous dialysis access flow using ultrasound

BACKGROUNDS

Despite numerous studies investigating the use of ultrasound (US) in assessing arteriovenous fistulas (AVF), there are no universally agreed threshold flow velocities in diagnosing significantly abnormal flow that are useful in predicting thrombotic flow-related dysfunction. This study evaluates a predictive model using receiver operating characteristic curve (ROC) analyses to establish threshold velocities.

METHODS

Five hundred and eleven US scans were analysed. ROC curves were used to determine the optimal threshold time average mean velocity (TAMV), peak systolic velocity (PSV) and end diastolic velocity (EDV) of the brachial artery supplying the AVF in determining the need for intervention or thrombosis within 3 months of the scans. Estimated flow volume (FV) ROC was used as an evaluative comparison.

RESULTS

There were 356 negative and 155 positive scan results in relation to the need for intervention or thrombosis. Empirical flow velocity parameters of TAMV, EDV and PSV were analysed using ROC curves, yielding an area under the curve (AUC) of 0.95, 0.92 and 0.86, respectively. FV ROC analysis yields a comparative AUC of 0.90. A TAMV cut-off at 48.6 cm/s yielded the highest AUC. Subgroup analysis yielded an optimal TAMV cut-off of 45 cm/s for forearm and 49 cm/s for arm AVF. The EDV was also highly predictive of outcomes. PSV has the lowest accuracy.

CONCLUSION

The TAMV of inflow brachial artery to AVF is highly predictive of outcomes of thrombotic flow-related dysfunction. Our study confirms TAMV cut-offs of 45 cm/s for forearm and 49 cm/s for arm AVF. These results require prospective validation.

Early Adventitial Activation and Proliferation in a Mouse Model of Arteriovenous Stenosis: Opportunities for Intervention

Background: Arteriovenous fistula (AVF) stenosis remains an important cause of AVF maturation failure, for which there are currently no effective therapies. We examined the pattern and phenotype of cellular proliferation at different timepoints in a mouse model characterized by a peri-anastomotic AVF stenosis. Methods: Standard immunohistochemical analyses for cellular proliferation and macrophage infiltration were performed at 2, 7 and 14 d on our validated mouse model of AVF stenosis to study the temporal profile, geographical location and cellular phenotype of proliferating and infiltrating cells in this model. Results: Adventitial proliferation and macrophage infiltration (into the adventitia) began at 2 d, peaked at 7 d and then declined over time. Surprisingly, there was minimal macrophage infiltration or proliferation in the neointimal region at either 7 or 14 d, although endothelial cell proliferation increased rapidly between 2 d and 7 d, and peaked at 14 d. Conclusions: Early and rapid macrophage infiltration and cellular proliferation within the adventitia could play an important role in the downstream pathways of both neointimal hyperplasia and inward or outward remodelling.

Safety and efficacy of arteriovenous fistula angioplasties performed by nephrologists: report from a Brazilian interventional nephrology center

Introduction:

Arteriovenous fistulas (AVF) are the first choice vascular access for hemodialysis. However, they present a high incidence of venous stenosis leading to thrombosis. Although training in interventional nephrology may improve accessibility for treatment of venous stenosis, there is limited data on the safety and efficacy of this approach performed by trained nephrologists in low-income and developing countries.

Methods:

This study presents the retrospective results of AVF angioplasties performed by trained nephrologists in a Brazilian outpatient interventional nephrology center. The primary outcome was technical success rate (completion of the procedure with angioplasty of all stenoses) and secondary outcomes were complication rates and overall AVF patency.

Findings:

Two hundred fifty-six angioplasties were performed in 160 AVF. The technical success rate was 88.77% and the main cause of technical failure was venous occlusion (10%). The incidence of complications was 13.67%, with only one patient needing hospitalization and four accesses lost due to the presence of hematomas and/or thrombosis. Grade 1 hematomas were the most frequent complication (8.2%). The overall patency found was 88.2 and 80.9% at 180 and 360 days after the procedure, respectively.

Conclusion:

Our findings suggest that AVF angioplasty performed by trained nephrologists has acceptable success rates and patency, with a low incidence of major complications as well as a low need for hospitalization.

Immuno-regenerative biomaterials for in situ cardiovascular tissue engineering - Do patient characteristics warrant precision engineering?

In situ tissue engineering using bioresorbable material implants - or scaffolds - that harness the patient's immune response while guiding neotissue formation at the site of implantation is emerging as a novel therapy to regenerate human tissues. For the cardiovascular system, the use of such implants, like blood vessels and heart valves, is gradually entering the stage of clinical translation. This opens up the question if and to what extent patient characteristics influence tissue outcomes, necessitating the precision engineering of scaffolds to guide patient-specific neo-tissue formation. Because of the current scarcity of human in vivo data, herein we review and evaluate in vitro and preclinical investigations to predict the potential role of patient-specific parameters like sex, age, ethnicity, hemodynamics, and a multifactorial disease profile, with special emphasis on their contribution to the inflammation-driven processes of in situ tissue engineering. We conclude that patient-specific conditions have a strong impact on key aspects of in situ cardiovascular tissue engineering, including inflammation, hemodynamic conditions, scaffold resorption, and tissue remodeling capacity, suggesting that a tailored approach may be required to engineer immuno-regenerative biomaterials for safe and predictive clinical applicability.

Distress Analysis of Mice with Cervical Arteriovenous Fistulas

Simple Summary

Functional hemodialysis access is essential for the survival of patients with end-stage renal disease. Although various guidelines recommend autologous arteriovenous fistula as the first choice for hemodialysis, it is still the Achilles heel for patients. Several in vivo models have been used to study and improve the mechanisms of vascular remodeling of arteriovenous fistula. However, some models have the disadvantage of having anatomical features or a hemodynamic profile different from that of the arteriovenous fistula in humans. In the presented cervical arteriovenous fistula model, these disadvantages were eliminated. It resembles the human physiology and is an ideal animal model for arteriovenous fistula research. Moreover, in order to understand the impact of this model on animal welfare, the distress of this new animal model was analyzed. Body weight, faecal corticosterone metabolites, burrowing activity, nesting behaviour and distress scores were analysed after fistula creation and during the following three weeks. The physiological, behavioural, and neuroendocrine assessments all indicated that this model causes only moderate distress to the animals. This not only meets the need for animal ethics but also improves the quality of scientific research. Therefore, this cervical model is suitable for arteriovenous fistula research and should be used more frequently in the future.

Abstract

The welfare of laboratory animals is a consistent concern for researchers. Its evaluation not only fosters ethical responsibility and addresses legal requirements, but also provides a solid basis for a high quality of research. Recently, a new cervical arteriovenous model was created in mice to understand the pathophysiology of arteriovenous fistula, which is the most commonly used access for hemodialysis. This study evaluates the distress caused by this new animal model. Ten male C57B6/J mice with cervical arteriovenous fistula were observed for 21 days. Non-invasive parameters, such as body weight, faecal corticosterone metabolites, burrowing activity, nesting activity and distress scores were evaluated at each time point. Six out of ten created arteriovenous fistula matured within the observation time as defined by an increased diameter. The body weight of all animals was reduced after surgery but recovered within five days. In addition, the distress score was significantly increased during the early time point but not at the late time point after arteriovenous fistula creation. Neither burrowing activity nor nesting behaviour were significantly reduced after surgical intervention. Moreover, faecal corticosterone metabolite concentrations did not significantly increase. Therefore, the cervical murine arteriovenous fistula model induced moderate distress in mice and revealed an appropriate maturation rate of the fistulas.

Development and validation of a risk score to prioritize patients for evaluation of access stenosis

Background

Access flow dysfunction, often associated with stenosis, is a common problem in hemodialysis access and may result in progression to thrombosis. Timely identification of accesses in need of evaluation is critical to preserving a functioning access. We hypothesized that a risk score using measurements obtained from the Vasc‐Alert surveillance device could be used to predict subsequent interventions.

Methods

Measurement of five factors over the preceding 28 days from 1.46 million hemodialysis treatments (6163 patients) were used to develop a score associated with interventions over the subsequent 60 days. The score was validated in a separate dataset of 298,620 treatments (2641 patients).

Results

Interventions in arteriovenous fistulae (AVF; n = 4125) were much more common in those with the highest score (36.2%) than in those with the lowest score (11.0). The score also was strongly associated with interventions in patients with an arteriovenous graft (AVG; n = 2,038; 43.2% vs. 21.1%). There was excellent agreement in the Validation datasets for AVF (OR = 2.67 comparing the highest to lowest score) and good agreement for AVG (OR = 1.92).

Conclusions

This simple risk score based on surveillance data may be useful for prioritizing patients for physical examination and potentially early referral for intervention.

Drug Coated Balloons for Dysfunctional Haemodialysis Venous Access: A Patient Level Meta-Analysis of Randomised Controlled Trials

OBJECTIVE

To perform an individual patient data level meta-analysis of randomised controlled trials comparing drug coated balloon angioplasty (DCB) against conventional percutaneous transluminal angioplasty (PTA) in the treatment of dysfunctional haemodialysis venous access.

METHODS

A search was conducted from inception to 13 November 2020. Kaplan-Meier curves comparing DCB with PTA by target lesion primary patency (TLPP) and access circuit primary patency (ACPP) were graphically reconstructed to retrieve patient level data. One stage meta-analyses with Cox models with random effects shared frailties were conducted to determine hazard ratios (HRs). Dynamic restricted mean survival times (RMST) were conducted in view of violation of the proportional hazards assumption. Conventional two stage meta-analyses and network meta-analyses under random effects Frequentist models were conducted to determine overall and comparative outcomes of paclitaxel concentrations used. Where outliers were consistently detected through outlier and influence analyses, sensitivity analyses excluding those studies were conducted.

RESULTS

Among 10 RCTs (1 207 patients), HRs across all models favoured DCB (one stage shared frailty HR 0.62, 95% CI 0.53 - 0.73, p < .001; two stage random effects HR 0.60, 95% CI 0.42 - 0.86, p = .018, I² = 65%) for TLPP. Evidence of time varying effects (p = .005) was found. TLPP RMST was + 3.54 months (25.0%) longer in DCB treated patients compared with PTA (p = .001) at three years. TLPP at six months, one year, and two years was 75.3% vs. 58.1%, 51.1% vs. 37.1%, and 31.4% vs. 26.0% for DCB and PTA, respectively. The P-Scores within the Frequentist network meta-analysis suggest that higher concentrations of paclitaxel were associated with better TLPP and ACPP. Among six RCTs (854 patients), the one stage model favoured DCB (shared frailty HR 0.72, 95% CI 0.60 - 0.87, p < .001) for ACPP. Conversely, the two stage random effects model demonstrated no significant difference (HR 0.76, 95% CI 0.35 - 1.67, p = .41, I² = 81%). Sensitivity analysis excluding outliers significantly favoured DCB (HR 0.61, 95% CI 0.41 - 0.91, p = .027, I² = 62%).

CONCLUSION

Overall evidence suggests that DCB is favoured over PTA in TLPP and ACPP.

Ultrasound guided interventional procedures on arteriovenous fistulae

Autogenous (AVF) and prosthetic (AVG) arteriovenous fistulas are the vascular accesses (VA) of choice for hemodialysis thanks to their improved patency, reduced costs, and lower rate of infections relative to catheters.

In an effort to maximize the number of primary AVF and AVG, shorten maturation times for AVF, and reduce the number of indwelling catheters, several new techniques have been developed within the context of an overall program designed to optimize access care.

This approach includes: (a) Primary Intraoperative Balloon Angioplasty on the vessels selected for AV creation whether small-sized or altered by pre-existing lesions; (b) Percutaneous Transluminal Angioplasty (PTA) on AVF and AVG stenosis, performed under ultrasonographic (UG) or fluoroscopic guide (FG).

We report the experience of two Center in performing the above mentioned procedures on even complex VA. The wise adoption of these techniques may avail to meet the stringent demands for reliable VA placement as defined by KDOQI and, thereby, expand the duration and quality of life for hemodialysis patients.

Surgical repair of a special category of arteriovenous fistula outflow stenosis caused by venous valve hyperplasia

OBJECTIVE

This study evaluated a special category of arteriovenous fistula outflow stenosis caused by venous valve hyperplasia and explored the effectiveness of surgical repair in dealing with this kind of stenosis.

STUDY DESIGN

This retrospective cohort study was conducted from February 2016 to January 2020 in our center. Patients with arteriovenous fistula dysfunction, including flow rate insufficiency, venous hypertension, thrombosis, and aneurysm dilation enlargement, were selected. Stenosis lesions presenting with venous valve hyperplasia were selected after ultrasound screening. All patients underwent surgical repair and were followed up every 6 months after surgery.

RESULTS

Forty-three patients (median age, 54.5 ± 11.2 years; 65.1% men) were included. All procedures were technically successful. Based on intraoperative exploration, 56.5% were reconstructed via autologous vein patch, 17.4% of patients were reconstructed with end-to-end reconstruction after cutting the stenotic segment, 13.0% of cases simply had the valve resected, and 13.0% of cases involved a longitudinal incision and transverse suture. All patients returned to routine dialysis the following day and avoided catheter insertion. The mean follow-up time was 22.5 ± 14.0 (range, 1.3-49.8) months. The patency rates at 2 and 4 years were 92.2% and 79.0%, respectively. Valves harvested from patients were analyzed via Masson staining and immunohistochemical staining, indicating collagen fiber and myofibroblast hyperplasia in outflow venous valve hyperplasia (OVVH).

CONCLUSIONS

Outflow venous valve hyperplasia can lead to fistula dysfunction. Ultrasound is the main method to diagnosis OVVH. Special surgical repair can preserve valuable vascular resources and relieve stenosis, is safe and effective, and has a high patency rate.

Changes in duplex ultrasound parameters during maturation according to arteriovenous access types in incident hemodialysis patients

BACKGROUND

Little is known about the changes in hemodynamic parameters during arteriovenous (AV) access maturation using duplex ultrasound according to radiocephalic fistula (RCF), brachiocephalic fistula (BCF), and AV graft (AVG) in incident hemodialysis (HD) patient. The objective of this study was to evaluate changes and differences in brachial artery flow rate (BAFR) and related parameters affecting maturation by duplex ultrasound in incident HD patients according to access type.

METHODS

This study was an observational study conducted from March 2019 to October 2020. During the study period, 109 incident patients underwent new AV access creation, of which 100 were included in the study. The duplex ultrasound was performed on the day prior to access creation, further, day 1, 2 weeks, and 4 weeks later after access creation in incident HD patients.

RESULTS

Among all the patients, 38 (38%) received BCF, while 26 (26%) underwent RCF. Of the patients with AVG, 18 (50%) had a forearm loop AVG. The overall mean age was 62.2 ± 13.8 years (range, 32-89). The BAFR increased about 6.9 times in the RCF, 17.4 times in the BCF, and 19.5 times in the AVG at day 1. The median BAFR measured on day 1 was 580.4 mL/min for RC, 1029.0 mL/min for BC, and 1133.0 mL/min for AVG. Relative to the values measured in week 4, the BAFR on day 1 was 69.5% in RCF, 90.6% in BCF, and 93.9% in AVG. The acceleration decreased most significantly on day 1(p < 0.05). The acceleration time increased significantly on day 1 (p < 0.05) and beyond during maturation in the RCF and BCF. The BAFR of the RCF had a significantly negative correlation with the pulsatility index. The BAFR of the BCF showed a significantly positive correlation with the systolic and diastolic blood pressure but negatively correlated with pulse rate. The BAFR of the AVG showed a significant positive correlation with the diameter of the outflow vein.

CONCLUSIONS

There were differences in the clinical and duplex parameters during maturation according to access type. The most dramatic changes of duplex parameters were on the day after AV access creation regardless of AV access types. Though RCF had a lower BAFR rate compared to BCF and AVG, it already had a sufficient BAFR required for adequate HD treatment the day after creation. The BAFR of BCF was not different from that of AVG.

Simulator-based hemodialysis cannulation skills training: a new horizon?

In accordance with the recently released Kidney Disease Outcomes Quality Initiative  (KDOQI) guidelines, there is a significant need for focused efforts on improving hemodialysis cannulation outcomes. Toward this, structured and meaningful training of our clinical personnel who cannulate in dialysis clinics is a priority. With the availability of advanced sensors and computing methods, simulators could be indispensable tools for standardized skills assessment and training. In this article we present ways in which sensor data could be used to quantify cannulation skill. As with many other medical specialties, implementation of simulator-based training holds the promise of much-needed improvement in end-stage kidney disease patient outcomes.

Utility of Blood Flow/Resistance Index Ratio (Qx) as a Marker of Stenosis and Future Thrombotic Events in Native Arteriovenous Fistulas

Objective: The resistance index (RI) and the blood flow volume (Q_a) are the most used Doppler ultrasound (DUS) parameters to identify the presence of stenosis in arteriovenous fistula (AVF). However, the reliability of these indexes is now matter of concern, particularly in predicting subsequent thrombosis. In this study, we aimed at testing the diagnostic capacity of the Q_a/RI ratio (Q_x) for the early identification of AVF stenosis and for thrombosis risk stratification.

Methods: From a multicentre source population of 336 HD patients, we identified 119 patients presenting at least one “alarm sign” for clinical suspicious of stenosis. Patients were therefore categorized by DUS as stenotic (n = 60) or not-stenotic (n = 59) and prospectively followed. Q_a, RI, and Q_X, together with various clinical and laboratory parameters, were recorded.

Results: Q_a and Q_x were significantly higher while RI was significantly lower in non-stenotic vs. stenotic patients (p < 0.001 for each comparison). At ROC analyses, Q_x had the best discriminatory power in identifying the presence of stenosis as compared to Q_a and RI (AUCs 0.976 vs. 0.953 and 0.804; p = 0.037 and p < 0.0001, respectively). During follow-up, we registered 30 thrombotic events with an incidence rate of 12.65 (95% CI 8.54–18.06) per 100 patients/year. In Cox-regression proportional hazard models, Q_x showed a better capacity to predict thrombosis occurrence as compared to Q_a (difference between c-indexes: 0.012; 95% CI 0.004–0.01).

Conclusions: In chronic haemodialysis patients, Q_x might represent a more reliable and valid indicator for the early identification of stenotic AVFs and for predicting the risk of following thrombosis.

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).

Predictors associated with early and late restenosis of arteriovenous fistulas and grafts after percutaneous transluminal angiography

BACKGROUND

The objective of this study was to assess postintervention patency and analyze the predictive factors associated with early and late restenosis after intervention in hemodialysis arteriovenous fistulas (AVF) and arteriovenous grafts (AVG).

METHODS

This study retrospectively analyzed 284 hemodialysis patients who underwent percutaneous transluminal angioplasty (PTA) due to AVF and AVG stenosis. A total of 350 PTA procedures were performed. Clinical, anatomical, biochemical, and technical variables were analyzed. Using univariate and multivariate analyses, we assessed the postintervention patency of PTA by follow-up, and identified the predictive factors taking into account competing risks.

RESULTS

Postintervention patency rates at 3, 6, 12, and 24 months were 86.5%, 66.4%, 42.6%, and 29.8%, respectively, with a median patency duration of 11±0.71 months. Kaplan-Meier analysis showed that the patency rate of the AVF group (n=271) was dramatically higher than the AVG group (n=79) at 3, 6, and 12 months after PTA, respectively (88.9% vs. 78.5%, 69.0% vs. 57.4%, 48.8% vs. 20.0%, P<0.01). Cox survival analysis revealed that the factors associated with postintervention patency of AVF included age of fistulas, serum albumin (ALB) levels, location of stenoses, lesion length longer than 2 cm, multiple stenoses, and maximal pressure of dilatation lower than 16 atm. In addition, factors related to postintervention patency of AVG included the presence of diabetes and hypertension, and serum ALB.

CONCLUSIONS

This study demonstrated that the risk factors associated with postintervention patency of AVF included age of fistulas, lower levels of serum ALB, location of stenoses, lesion length longer than 2 cm, multiple stenoses, and maximal pressure of dilatation lower than 16 atm. In addition, risk factors related to postintervention patency of AVG included the presence of diabetes and lower levels of serum ALB, while the presence of hypertension was found to be a protective factor for reducing patency loss of AVG. Among all these factors, serum ALB and multiple stenoses tended to predict early restenosis, while pressure of dilatation tended to predict late restenosis.

Periadventitial Delivery of Simvastatin-Loaded Microparticles Attenuate Venous Neointimal Hyperplasia Associated With Arteriovenous Fistula

Background

Venous neointimal hyperplasia and venous stenosis (VS) formation can result in a decrease in arteriovenous fistula (AVF) patency in patients with end‐stage renal disease. There are limited therapies that prevent VNH/VS. Systemic delivery of simvastatin has been shown to reduce VNH/VS but local delivery may help decrease the side effects associated with statin use. We determined if microparticles (MP) composed of cyclodextrins loaded with simvastatin (MP‐SV) could reduce VS/VNH using a murine arteriovenous fistula model with chronic kidney disease.

Methods and Results

Male C57BL/6J mice underwent nephrectomy to induce chronic kidney disease. Four weeks later, an arteriovenous fistula was placed and animals were randomized to 3 groups: 20 μL of PBS or 20 μL of PBS with 16.6 mg/mL of either MP or MP‐SV. Animals were euthanized 3 days later and the outflow veins were harvested for quantitative reverse transcriptase–polymerase chain reaction analysis and 28 days later for immunohistochemistical staining with morphometric analysis. Doppler ultrasound was performed weekly. Gene expression of vascular endothelial growth factor‐A (Vegf‐A), matrix metalloproteinase‐9 (Mmp‐9), transforming growth factor beta 1 (Tgf‐β1), and monocyte chemoattractant protein‐1 (Mcp‐1) were significantly decreased in MP‐SV treated vessels compared with controls. There was a significant decrease in the neointimal area, cell proliferation, inflammation, and fibrosis, with an increase in apoptosis and peak velocity in MP‐SV treated outflow veins. MP‐SV treated fibroblasts when exposed to hypoxic injury had decreased gene expression of Vegf‐A and Mmp‐9.

Conclusions

In experimental arteriovenous fistulas, periadventitial delivery of MP‐SV decreased gene expression of Vegf‐A, Mmp‐9, Tgf‐β1 and Mcp‐1, VNH/VS, inflammation, and fibrosis.

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.

The outcomes of carbon dioxide digital subtraction angiography for percutaneous transluminal balloon angioplasty of access circuits and venous routes in hemodialysis patients

The outcomes of carbon dioxide digital subtraction angiography (CO2-DSA) for performing percutaneous transluminal balloon angioplasty (balloon PTA) in hemodialysis patients has not been fully clarified. The purpose was to compare the outcomes of balloon PTA of hemodialysis shunts in terms of vessel patency between patients treated using CO2-DSA and conventional digital subtraction angiography using iodine contrast medium (C-DSA).We retrospectively evaluated 76 patients (38 males and 38 females, mean age: 65.0 ± 14.0 years). They were under hemodialysis and treated with balloon PTA using CO2-DSA or C-DSA at our institution between 2009 and 2016. Mean duration of the follow-up period was 25.59 ± 21.45 months. We compared the patency rates obtained after CO2-DSA-based balloon PTA with those after C-DSA-based balloon PTA. Secondary patency, which was defined as the duration of patency after all further endovascular interventions until surgical repair, was considered as the endpoint in this study.Overall, 19 and 57 patients underwent CO2-DSA- and C-DSA-based balloon PTA, respectively. CO2-DSA- and C-DSA-based balloon PTA produced clinical success rates of 100% and 96.5%, respectively. Blood vessel injury occurred in one patient who underwent C-DSA-based balloon PTA. No major complications occurred in CO2 group. At 24 months, the post-PTA secondary patency rates of CO2-DSA- and C-DSA-based balloon PTA were 94.1% and 93.9%, respectively (P = .9594).CO2-DSA is safe for hemodialysis patients. Compared with C-DSA, CO2-DSA-based balloon PTA produces have a similar secondary patency rate.

Comparison of regional and local anesthesia for arteriovenous fistula creation in end-stage renal disease: a systematic review and meta-analysis

Background

Arteriovenous fistulae (AVF) are the hemodialysis access modality of choice for patients with end-stage renal disease. However, they have a high early failure rate. Good vascular access is essential to manage long-term hemodialytic treatment, but some anesthesia techniques directly affect venous diameter as well as intra- and post-operative blood flow. The main purpose of this meta-analysis was to compare the results of regional and local anesthesia (RA and LA) for arteriovenous fistula creation in end-stage renal disease.

Methods

We conducted a systematic review and meta-analysis to synthesize evidence from 7 randomized controlled trials (565 patients) and 1 observational study (408 patients) with the aim of evaluating the safety and efficacy of RA versus LA in surgical construction of AVF.

Results

Pooled data showed that RA was associated with higher primary patency rates than LA (odds ratio [OR], 1.88; 95% confidence interval [CI]: 1.24–2.84; P = 0.003; I² = 31%). Additionally, brachial artery diameter was significantly increased in the RA versus LA group (mean difference [MD], 0.83; 95% CI: 0.75–0.92; P < 0.001; I² = 97%) and the need for intra- as well as post-operative pain killers was significantly less (RA, P = 0.0363; LA, P = 0.0318). Moreover, operation duration was significantly reduced using RA versus LA (MD, − 29.63; 95% CI: − 32.78 - -26.48; P < 0.001; I² = 100%).

Conclusions

This meta-analysis suggests that RA is preferable to LA in patients with end-stage renal disease in guaranteeing AVF patency and increasing brachial artery diameter.

Paclitaxel-Coated Balloon versus Plain Balloon Angioplasty for Dysfunctional Autogenous Radiocephalic Arteriovenous Fistulas: A Prospective Randomized Controlled Trial

Objective

To report the mid-term results of a single-center randomized controlled trial comparing drug-coated balloon angioplasty (DBA) and plain balloon angioplasty (PBA) for the treatment of dysfunctional radiocephalic arteriovenous fistulas (RCAVFs).

Materials and Methods

In this prospective study, 39 patients (mean age, 62.2 years; 21 males, 18 females) with RCAVFs failing due to juxta-anastomotic stenosis were randomly assigned to undergo either both DBA and PBA (n = 20, DBA group) or PBA alone (n = 19, PBA group) between June 2016 and June 2018. Primary endpoints were technical and clinical success and target lesion primary patency (TLPP); secondary outcomes were target lesion secondary patency (TLSP) and complication rates. Statistical analysis was performed using the Kaplan-Meier product limit estimator.

Results

Demographic data and baseline clinical characteristics were comparable between the groups. Technical and clinical success rates were 100% in both groups. There was no significant difference between the groups in the mean duration of TLPP (DBA group: 26.7 ± 3.6 months; PBA group: 27.0 ± 3.8 months; p = 0.902) and TLSP (DBA group: 37.3 ± 2.6 months; PBA group: 40.4 ± 1.5 months; p = 0.585). No procedural or post-procedural complications were identified.

Conclusion

Paclitaxel-coated balloon use did not significantly improve TLPP or TLSP in the treatment of juxta-anastomotic stenosis of dysfunctional RCAVFs.

Long-Term Functional Patency and Cost-Effectiveness of Arteriovenous Fistula Creation under Regional Anesthesia: a Randomized Controlled Trial

BACKGROUND

Regional anesthesia improves short-term blood flow through arteriovenous fistulas (AVFs). We previously demonstrated that, compared with local anesthesia, regional anesthesia improves primary AVF patency at 3 months.

METHODS

To study the effects of regional versus local anesthesia on longer-term AVF patency, we performed an observer-blinded randomized controlled trial at three university hospitals in Glasgow, United Kingdom. We randomly assigned 126 patients undergoing primary radiocephalic or brachiocephalic AVF creation to receive regional anesthesia (brachial plexus block; 0.5% L-bupivacaine and 1.5% lidocaine with epinephrine) or local anesthesia (0.5% L-bupivacaine and 1% lidocaine). This report includes findings on primary, functional, and secondary patency at 12 months; reinterventions; and additional access procedures (primary outcome measures were previously reported). We analyzed data by intention to treat, and also performed cost-effectiveness analyses.

RESULTS

At 12 months, we found higher primary patency among patients receiving regional versus local anesthesia (50 of 63 [79%] versus 37 of 63 [59%] patients; odds ratio [OR], 2.7; 95% confidence interval [95% CI], 1.6 to 3.8; P=0.02) as well as higher functional patency (43 of 63 [68%] versus 31 of 63 [49%] patients; OR, 2.1; 95% CI, 1.5 to 2.7; P=0.008). In 12 months, 21 revisional procedures, 53 new AVFs, and 50 temporary dialysis catheters were required. Regional anesthesia resulted in net savings of £195.10 (US$237.36) per patient at 1 year, and an incremental cost-effectiveness ratio of approximately £12,900 (US$15,694.20) per quality-adjusted life years over a 5-year time horizon. Results were robust after extensive sensitivity and scenario analyses.

CONCLUSIONS

Compared with local anesthesia, regional anesthesia significantly improved both primary and functional AVF patency at 1 year and is cost-effective.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Local Anaesthesia versus Regional Block for Arteriovenous Fistulae, NCT01706354.

Efficacy of Regional Anesthesia in Secondary Procedures or Revisions of Arteriovenous Fistula

BACKGROUND

Several factors affect the outcomes of arteriovenous fistula (AVF) and end-stage renal disease (ESRD). This study aimed to evaluate the efficacy of regional anesthesia in secondary procedures or revisions of AVF.

METHODS

Medical records of patients who underwent treatment for AVF secondary procedures or revisions under brachial plexus block (BPB) between March 2016 and June 2019 were retrospectively analyzed. Patient characteristics and clinical outcomes were evaluated.

RESULTS

In total, 375 patients (mean age 65.6 ± 12.74; males 210, 56.0%) were enrolled in the study and 770 procedures were performed under BPB for AVF secondary procedures or revisions. The procedures included endovascular treatment (385, 50.0%), surgical treatment (105, 13.6%), and hybrid treatment (280, 36.4%). In 180 procedures (23.4%) for AVF lesions, the operative field included a single segment of the arm, whereas in 590 procedures (76.6%), the operative field included multiple segments. In total, 37 (4.8%) cases of 30-day postoperative complications were observed, of which 33 (4.3%) were surgery-related complications, 2 (0.3%) were BPB-related complications (neurapraxia), and 2 (0.3%) were contrast agent allergic reactions; 34 (4.4%) reinterventions of the total 201 (26.1%) reinterventions were performed within 30 days postoperatively. The mean operation time was 87.5 ± 55.35 min. The pain score for all patients was 0 (no pain), and no patient demanded opioids postoperatively.

CONCLUSIONS

Ultrasound-guided BPB is safe and effective for AVF secondary procedures or revisions in ESRD patients.

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

INTRODUCTION

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Paclitaxel drug-coated balloon angioplasty for the treatment of failing arteriovenous fistulas: a single-center experience

Objectives: To report our experience of angioplasty with Lutonix (Bard Peripheral Vascular, Inc., Tempe, AZ) drug-coated balloon (DCB) for the treatment of failing arteriovenous fistulas (AVF).Materials and methods: Retrospective, single-center analysis consisting of 14 patients treated with Lutonix paclitaxel DCBs in the period from July 2015 through April 2017. We analyzed technical success, clinical success, primary patency of the target lesion, primary patency of the dialysis circuit, and the rate of complications. Regular follow-up of AVF patency was realized by clinical examination and duplex ultrasonography. The Kaplan-Meier survival method was applied to determine the cumulative primary patency of the target lesion and the dialysis circuit.Results: Technical success was 100% and clinical success 92.9%. There were no major or minor complications. Cumulative target lesion primary patency after DCB was 69.2% at 6 months and 31.6% at 12 months. Cumulative vascular circuit primary patency was 61.5% at 6 months and 31.6% at 12 months.Conclusion: Compared to results reported in literature with plain old balloon angioplasty (POBA), Lutonix paclitaxel DCB angioplasty proved a short-term patency benefit in treatment of dialysis AVF stenosis.

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.

Predictors of primary patency after percutaneous balloon angioplasty for stenosis of Brescia-Cimino hemodialysis arteriovenous fistula

OBJECTIVE

Percutaneous transluminal balloon angioplasty (PTA) is recommended as the first choice to treat stenosis of Brescia-Cimino arteriovenous fistulas (B-C AVFs). The ability to predict which B-C AVFs are at risk for recurrent stenosis post-PTA would allow closer monitoring of patients, and possibly result in surgical intervention rather than repeat PTA. The purpose of this study was to identify predictive factors of primary patency after PTA in B-C AVFs.

METHODS

Patients diagnosed with B-C AVF primary stenosis and treated by PTA between November 2013 and March 2018 were included in the study. Patient and stenotic lesion characteristics and PTA procedure factors were included in the analysis. The Kaplan-Meier method was used to analyze the primary patency rate. Cox proportional hazard regression analysis was used to identify factors predictive of decreased primary patency.

RESULTS

74 patients (35 males, 39 females) with a mean age of 61.68 ± 11.44 years (range, 36-84 years) were included in the study. The mean B-C AVF age was 16.34 ± 12.93 months (range, 2-84 months), and the median primary patency time was 7.79 ± 0.48 months. Cox proportional hazard regression analysis revealed stenosis location at the inflow artery [hazard ratio (HR)=3.83, 95% confidence interval (CI): 1.46-10.09] or anastomosis (HR = 1.90, 95% CI: 1.09-3.32), dilation >2 times during PTA (HR = 2.30, 95% CI: 1.22-4.34), and residual stenosis >30% (HR = 2.42, 95% CI: 1.26-4.63) were significantly associated with decreased patency.

CONCLUSION

In conclusion, the primary patency rate of PTA for B-C AVF dysfunction is reduced by dilation >2 times, residual stenosis >30%, and stenosis located at the inflow artery or anastomosis. These results may help in tailoring surveillance programs, multiple PTA, or a proximal re-anastomosis surgery in patients with AVF dysfunction.

ADVANCES IN KNOWLEDGE

A number of studies have been conducted to examine the predictors of primary patency after PTA, however, no definitive conclusions have been reached. Our study revealed that stenosis location at the inflow artery or anastomosis, dilation >2 times during PTA, and residual stenosis >30% were the predictors of primary patency after PTA, which may help in tailoring surveillance programs, multiple PTA, or a proximal re-anastomosis surgery in patients with arteriovenous fistulas dysfunction.

Regional anaesthesia practice for arteriovenous fistula formation surgery

We conducted a survey and semi‐structured qualitative interviews to investigate current anaesthetic practice for arteriovenous fistula formation surgery in the UK. Responses were received from 39 out of 59 vascular centres where arteriovenous access surgery is performed, a response rate of 66%. Thirty‐five centres reported routine use of brachial plexus blocks, but variation in anaesthetic skill‐mix and practice were observed. Interviews were conducted with 19 clinicians from 10 NHS Trusts including anaesthetists, vascular access and renal nurses, surgeons and nephrologists. Thematic analysis identified five key findings: (1) current anaesthetic practice showed that centres could be classified as ‘regional anaesthesia dominant’ or ‘local anaesthesia/mixed’; (2) decision making around mode of anaesthesia highlighted the key role of surgeons as frontline decision makers across both centre types; (3) perceived barriers and facilitators of regional block use included clinicians’ beliefs and preferences, resource considerations and patients’ treatment preferences; (4) anaesthetists’ preference for supraclavicular blocks emerged, alongside acknowledgement of varied practice; (5) there was widespread support for a future randomised controlled trial, although clinician equipoise issues and logistical/resource‐related concerns were viewed as potential challenges. The use of regional anaesthesia for arteriovenous fistula formation in the UK is varied and influenced by a multitude of factors. Despite the availability of anaesthetists capable of performing regional blocks, there are other limiting factors that influence the routine use of this technique. The study also highlighted the perceived need for a large multicentre, randomised controlled trial to provide an evidence base to inform current practice.