Tailoring of arteriovenous graft-to-vein anastomosis angle to attenuate pathological flow fields.

Arteriovenous grafts are routinely placed to facilitate hemodialysis in patients with end stage renal disease. These grafts are conduits between higher pressure arteries and lower pressure veins. The connection on the vein end of the graft, known as the graft-to-vein anastomosis, fails frequently and chronically due to high rates of stenosis and thrombosis. These failures are widely believed to be associated with pathologically high and low flow shear strain rates at the graft-to-vein anastomosis. We hypothesized that consistent with pipe flow dynamics and prior work exploring vein-to-artery anastomosis angles in arteriovenous fistulas, altering the graft-to-vein anastomosis angle can reduce the incidence of pathological shear rate fields. We tested this via computational fluid dynamic simulations of idealized arteriovenous grafts, using the Bird-Carreau constitutive law for blood. We observed that low graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically low shear rates, and that high graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically high shear rates. Optimizations predicted that an intermediate  ([Formula: see text]) graft-to-anastomosis angle was optimal. Our study demonstrates that graft-to-vein anastomosis angles can significantly impact pathological flow fields, and can be optimized to substantially improve arteriovenous graft patency rates.

A call to optimize haemodialysis vascular access care in healthcare disrupted by COVID-19 pandemic.

The COVID-19 pandemic has resulted in major disruption to the delivery of both routine and urgent healthcare needs in many institutions across the globe. Vascular access (VA) for haemodalysis (HD) is considered the patient's lifeline and its maintenance is essential for the continuation of a life saving treatment. Prior to the COVID-19 pandemic, the provision of VA for dialysis was already constrained. Throughout the pandemic, inevitably, many patients with chronic kidney disease (CKD) have not received timely intervention for VA care. This could have a detrimental impact on dialysis patient outcomes in the near future and needs to be addressed urgently. Many societies have issued prioritisation to allow rationing based on clinical risk, mainly according to estimated urgency and need for treatment. The recommendations recently proposed by the European and American Vascular Societies in the COVID-19 pandemic era regarding the triage of various vascular operations into urgent, emergent and elective are debatable. VA creation and interventions maintain the lifeline of complex HD patients, and the indication for surgery and other interventions warrants patient-specific clinical judgement and pathways. Keeping the use of central venous catheters at a minimum, with the goal of creating the right access, in the right patient, at the right time, and for the right reasons, is mandatory. These strategies may require local modifications. Risk assessments may need specific "renal pathways" to be developed rather than applying standard surgical risk stratification. In conclusion, in order to recover from the second wave of COVID-19 and prepare for further phases, the provision of the best dialysis access, including peritoneal dialysis, will require working closely with the multidisciplinary team involved in the assessment, creation, cannulation, surveillance, maintenance, and salvage of definitive access.

Quality indicators of vascular access procedures for hemodialysis.

Improved quality of surgical procedures can minimize complications, the morbidity and mortality of patients, and in addition decrease costs. Quality indicators in angioaccess surgery are, however, not clearly defined. The aim of this review article is therefore to find the most important factors affecting quality in vascular access procedures. Even though autogenous arteriovenous fistula has been recognized as the best vascular access for hemodialysis, the high percentage of unsuccessful attempts associated with it raises the question about quality assessment in angioaccess procedures. Unfortunately, quality indicators in vascular access surgery are difficult to define and measure. Among those that can be obtained are: the time between the presentation of patients to a vascular access surgeon and the construction of a fistula, the percentage of autogenous fistulas, the percentage of functional fistulas in prevalent and incident hemodialysis patients, the percentage of creation of a functional fistula in the first attempt, and durability of an access. Organizational improvement and educational programs are also necessary at institutions with inferior quality indicators of vascular access care, as even small increase in quality may mean the survival of an individual patient. Quality indicators in angioaccess surgery can also serve as a helpful tool in choosing the best vascular access surgeon or vascular access center. The choice can consequently reflect on increased survival and quality of life in patients needing hemodialysis.

Managing Access by Generating Improvements in Cannulation: A national quality improvement project.

Cannulation is essential for haemodialysis with arteriovenous access, but also damages the arteriovenous access making it prone to failure, is associated with complications and affects patients' experiences of haemodialysis. Managing Access by Generating Improvements in Cannulation is a national UK quality improvement project, designed to improve cannulation practice in the United Kingdom, ensuring it reflects current needling recommendations. It uses a simple quality improvement method, the Model for Improvement, to structure improvement to cannulation practice. It assists units in the practical implementation of the British Renal Society and Vascular Access Society of Britain and Ireland needling recommendations, ensuring actual cannulation practice reflects what is defined as best practice in cannulation. An eLearning package and awareness materials have been developed, to assist units in changing their cannulation practice. The Kidney Quality Improvement Partnership provides a structure for Managing Access by Generating Improvements in Cannulation that promotes development and dissemination. It is hoped that Managing Access by Generating Improvements in Cannulation will raise an understanding about the cannulation of arteriovenous access and change behaviours and beliefs around correct cannulation practice, to ensure longevity of this lifeline.

Guía de práctica clínica: Utilidad de los ultrasonidos en la creación y mantenimiento de los accesos arteriovenosos. Capítulo de Diagnóstico Vascular. Sociedad Española de Angiología y Cirugía Vascular / Clinical practice guide: utility of ultrasound in the creation and maintenance of arteriovenous access Vascular Diagnosis Chapter. Spanish Society of Angiology and Vascular Surgery

El acceso vascular en los pacientes en programa de hemodiálisis condiciona de forma significativa la calidad de las sesiones de diálisis, su morbimortalidad, complicaciones y necesidad de nuevos procedimientos a lo largo del tiempo, además de importantes implicaciones técnicas y económicas. Se trata de pacientes frágiles, muchas veces reintervenidos, que van a requerir un acceso vascular durante largos periodos de tiempo o para el resto de su vida, por lo que estamos ante una piedra angular que debemos tratar de la mejor forma posible. Y en este campo, los ultrasonidos ofrecen, más que en ninguna otra localización, una inestimable ayuda en todas las etapas del acceso vascular: desde su planificación, creación, seguimiento, o como herramienta intraoperatoria

Vascular access in patients on hemodialysis significantly affects the quality of life, morbidity, mortality, complications and the need for new procedures over time. In addition, they have important technical and economic implications. These are fragile patients, often with many reinterventions, who will require vascular access for long periods of time or for the rest of their lives, so we are facing a big health problem that we must treat in the best possible way. In this framework, ultrasounds offer, more than in any other location, an invaluable help in all stages of vascular disease: from planning the arteriovenous access, creation, follow-up or as intraoperative tool. This document tries to provide an update and help to clinical practice

Interventional Nephrology: Opportunities and Challenges.

The nephrologist has a pivotal role as the leader of multidisciplinary teams to optimize vascular access care of the patient on dialysis and to promote multidisciplinary collaboration in research, training, and education. The continued success of interventional nephrology as an independent discipline depends on harnessing these efforts to advance knowledge and encourage innovation. A comprehensive curriculum that encompasses research from bench to bedside coupled with standardized clinical training protocols are fundamental to this expansion. As we find ourselves on the threshold of a much-awaited revolution in nephrology, there is great opportunity but also formidable challenges in the field - it is up to us to work together to realize the enormous potential of our discipline.

Hemodialysis Vascular access maintenance in the Covid-19 pandemic: Positioning paper from the Interventional Nephrology Committee of the Brazilian Society of Nephrology.

Vascular accesses for hemodialysis are considered the patient's lifeline and their maintenance is essential for treatment continuity. Following the example of institutions in other countries affected by the Covid-19 pandemic, the Brazilian Society of Nephrology developed these guidelines for healthcare services, elaborating on the importance of carrying out procedures for the preparation and preservation of vascular accesses. Creating definitive accesses for hemodialysis, grafts and arteriovenous fistulas are non-elective procedures, as well as the transition from the use of non-tunneled catheters to tunneled catheters, which cause less morbidity. In the case of patients with suspected or confirmed coronavirus infection, one may postpone the procedures for the quarantine period, to avoid spreading the disease.

Project of the Health Policy Program: Access to Vessels in Renal Replacement Therapy - Fistula First/Catheter Last.

INTRODUCTION: The number of patients with end-stage renal failure (ESRF) that require inclusion in the renal replacement therapy program (RRT) is steadily increasing. This fact caused an increase in vascular operations involving the production of vascular access. According to the current guidelines, the best and safest option for a patient with chronic kidney disease (CKD) is the early creation of arteriovenous fistula (AVF). An efficient vascular access to haemodialysis determines the procedure and directly affects the quality of life of a patient with CKD. AIM: The aim of this paper is to present the author's project of the health policy program "Vascular access in renal replacement therapy - fistula first/catheter last", the essence of which is to assess the practical effectiveness and develop an optimal model of CKD patient care organization qualified for the chronic RRT program. MATERIAL AND METHODS: The target population of the program consists of all patients diagnosed with CKD, qualified for the RRT program. The basic measures of the program's effectiveness include: (1) reduction in the number of re-hospitalizations related to vascular access, (2) reduction in the number of complications associated with haemofiltration surgery, (3) reduction in general mortality among patients undergoing dialysis in a 12-month perspective, (4) increasing knowledge in the field of self-care and self-care of arteriovenous anastomosis, and (5) creating a register of vascular access in Poland. CONCLUSIONS: To sum up, health policy programme "Vascular access in renal replacement therapy - fistula first/catheter last" covering health care services provided in the scope and on the conditions specified in the regulations issued on the basis of article 31d of the Act of 27 August 2004 on health care benefits financed from public funds, is to check whether planned changes in the organization and delivery of services will improve the situation of patients with CKD eligible for chronic RRT and whether it will be effective the point of view of the health care system.

[Linee guida di pratica clinica sulla cura peri- e post-operatoria delle fistole e delle protesi arterovenose per emodialisi negli adulti. Sintesi delle raccomandazioni delle "European Renal Best Practice (ERBP)"].

Questo documento è stato tradotto dall'inglese a nome dell'ERBP (European Renal Best Practice), un organo ufficiale dell'ERA-EDTA (European Renal Association - European Dialysis and Transplant Association), e si basa su una pubblicazione ufficiale edita su Nephrology, Dialysis and Transplantation (NDT). ERBP si assume la piena responsabilità solo per la versione completa delle linee guida in originale e in lingua inglese pubblicate su NDT: Gallieni M, Hollenbeck M, Inston N, et al. Clinical practice guideline on peri- and postoperative care of arteriovenous fistulas and grafts for haemodialysis in adults. Nephrol Dial Transplant 2019; 34(S_2):ii1-ii42. https://doi.org/10.1093/ndt/gfz072.

Causes of the delay in creating permanent vascular access in hemodialysis patients.

Majority of the chronic kidney disease (CKD) patients undergo hemodialysis (HD) with central venous catheter which has multiple complications. This study aims to identify the physicians' perspectives regarding the reasons of delayed arteriovenous fistula (AVF) creation in the Kingdom of Saudi Arabia to improve the quality of CKD patients' care and prognosis and prevent complications. A cross-sectional descriptive study was conducted on KSA nephrologists using a questionnaire which includes factors associated with delay in AVF creation, which were categorized into patient, physician, and hospital factors. The optimal timing of starting dialysis was also assessed. In a total of 212 participants, 131 (61.8%) were of consultant level, with the largest numbers being from the Central region (52.4%). The most important patient factors associated with delay in AVF creation were denial of kidney disease or the need of AVF (76.4%), dialysis fears and practical concern (75.9%), and patient refusal (73.1%). The most important physician and hospital factors were insufficient conduction of predialysis care and education (63.7%) and late referral to a nephrologist (56.6%). Participants would create AVF when the patient reaches Stage 4 CKD (69.3%) or Stage 5 (27.4%), and 88.7% of the participants would do so 3-6 months before the anticipated start of HD. Over two-thirds of the participants (68.4%) chose patient as the main factor contributing to the delay of permanent vascular access. A validated approach to patient selection, patient-centered predialysis care, and referral to vascular access creation that could be applied on different types of patients in different regions is required.

Quality assessment of vascular access procedures for hemodialysis: A position paper of the Vascular Access Society based on the analysis of existing guidelines.

Quality assessment in vascular access procedures for hemodialysis is not clearly defined. The aim of this article is to compare various guidelines regarding recommendation on quality control in angioaccess surgery. The overall population of end-stage renal disease patients and patients in need for hemodialysis treatment is growing every year. Chronic intermittent hemodialysis is still the main therapy. The formation of a functional angioaccess is the cornerstone in the management of those patients. Native (autologous) arteriovenous fistula is the best vascular access available. A relatively high percentage of primary failure and fistula abandonment increases the need for quality control in this field of surgery. There are very few recommendations of quality assessment on creation of a vascular access for hemodialysis in the searched guidelines. Some guidelines recommend the proportion of native arteriovenous fistula in incident and prevalent patients as well as the maximum tolerable percentage of central venous catheters and complications. According to some guidelines, surgeon's experience and expertise have a considerable influence on outcomes. There are no specific recommendations regarding surgeon's specialty, grade, level of skills, and experience. In conclusion, there is a weak recommendation in the guidelines on quality control in vascular access surgery. Quality assessment criteria should be defined in this field of surgery. According to these criteria, patients and nephrologists could choose the best vascular access center or surgeon. Centers with best results should be referral centers, and centers with poorer results should implement quality improvement programs.

Quality improvement in vascular access: The role of patient-reported outcome measures.

Quality improvement initiatives should be aimed to enhance clinical outcomes, service delivery and quality of life for patients. For patients reliant on haemodialysis, vascular access is a lifeline. Survival differences relating to the type of vascular access are evident and many initiatives have focussed on increasing absolute rates of arteriovenous fistulas and/or decreasing central venous catheter use. While these have achieved some success quantitatively, the qualitative effects are less obvious. The aims of this review article are to explore the concepts of quality of care in vascular access. There is a paucity of studies into the effects of vascular access on the quality of life of dialysis patients, and where studies have been performed, generalised patient-reported outcome measures have been used. To facilitate the implementation of quality improvement programmes specifically for vascular access requires suitable tools. While existing patient-reported outcome measures may be applicable to vascular access, it is likely that these will require further evaluation, and the development of vascular access-specific patient-reported outcome measures may be required.

Hemodialysis Vascular access maintenance in the Covid-19 pandemic: Positioning paper from the Interventional Nephrology Committee of the Brazilian Society of Nephrology / Manutenção de acessos vasculares para hemodiálise na pandemia da Covid-19: posicionamento do Comitê de Nefrologia Intervencionista da Sociedade Brasileira de Nefrologia

ABSTRACT Vascular accesses for hemodialysis are considered the patient's lifeline and their maintenance is essential for treatment continuity. Following the example of institutions in other countries affected by the Covid-19 pandemic, the Brazilian Society of Nephrology developed these guidelines for healthcare services, elaborating on the importance of carrying out procedures for the preparation and preservation of vascular accesses. Creating definitive accesses for hemodialysis, grafts and arteriovenous fistulas are non-elective procedures, as well as the transition from the use of non-tunneled catheters to tunneled catheters, which cause less morbidity. In the case of patients with suspected or confirmed coronavirus infection, one may postpone the procedures for the quarantine period, to avoid spreading the disease.

RESUMO Os acessos vasculares para hemodiálise são considerados a linha da vida do paciente, e sua manutenção é essencial para o seguimento do tratamento. A exemplo de instituições de outros países atingidos pela pandemia da Covid-19, a Sociedade Brasileira de Nefrologia elaborou estas orientações para os serviços de saúde, esclarecendo a importância da realização dos procedimentos de confecção e preservação de acessos vasculares. Consideramos como não eletivos os procedimentos de confecção de acessos definitivos para hemodiálise, próteses e fístulas arteriovenosas, bem como a transição do uso de cateteres não tunelizados para cateteres tunelizados, os quais acarretam menor morbidade. Nos casos de pacientes com infecção suspeita ou confirmada por coronavírus, é aceitável o adiamento dos procedimentos pelo período de quarentena, para evitar disseminação da doença.

Two-Year Outcomes of Early Cannulation Arteriovenous Grafts for End-Stage Renal Disease.

BACKGROUND: Almost 80% of patients with end-stage renal disease (ESRD) initiate dialysis via a central venous catheter (CVC). CVCs are associated with multiple complications and a high cost of care. The purpose of our project is to determine the impact of early cannulation arteriovenous grafts (ECAVGs) on quality of care and costs. METHODS: The dialysis access modality, complications, secondary interventions, hospital outcomes, and detailed costs were tracked for 397 sequential patients who underwent access creation between July 2014 and October 2018. Complications were grouped into deep vein thrombosis, line infections, sepsis, pneumothorax, and other. Secondary interventions included angioplasty, angioplasty and stent grafting, thrombectomy, surgical revision, and explantation. Hospital outcomes included length of stay, inpatient mortality, 30-day readmission, and discharge disposition. Costs included supplies, medications, laboratory tests, labor, and other direct costs. All variables were measured at the time of the index procedure, 30 days, 90 days, 180 days, 270 days, 1 year, 18 months, and 2 years. RESULTS: There were 131 patients who underwent arteriovenous fistula (AVF) and 266 who received ECAVG for dialysis access. The total cost of care per patient was $17,523 for AVF and $5,894 for ECAVG at 1 year (P < 0.01). Primary-assisted patency for AVF was 49.3% versus 81.4% for ECAVG (P = 0.027), and secondary-assisted patency for AVF was 63.8% versus 85.4% for ECAVG at 1 year (P = 0.011). There was a survival advantage for ECAVGs at 1 year (78.6% for AVF vs 85.0% for ECAVG, P = 0.034). Patients who received ECAVG had fewer CVC days (2.3% vs 19.1% for AVF, P < 0.001), fewer complications (1.6% vs. 21.5% for AVF, P < 0.001), and fewer secondary interventions (17.0% vs 52.5% for AVF, P < 0.001). CONCLUSIONS: This is the first study on patients with ESRD to report detailed outcomes and cost analysis as it relates to AVF versus ECAVG. ECAVGs have an advantage over AVFs due to lower overall cost and better clinical outcomes at 1 year. Implementation of an urgent start dialysis access program centered around ECAVGs may help achieve the national goal of better health care at a lower cost for patients with ESRD.

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

BACKGROUND: There are three principle forms of vascular access available for the treatment of children with end stage kidney disease (ESKD) by haemodialysis: tunnelled catheters placed in a central vein (central venous lines, CVLs), arteriovenous fistulas (AVF), and arteriovenous grafts (AVG) using prosthetic or biological material. Compared with the adult literature, there are few studies in children to provide evidence based guidelines for optimal vascular access type or its management and outcomes in children with ESKD. METHODS: The European Society for Paediatric Nephrology Dialysis Working Group (ESPN Dialysis WG) have developed recommendations for the choice of access type, pre-operative evaluation, monitoring, and prevention and management of complications of different access types in children with ESKD. RESULTS: For adults with ESKD on haemodialysis, the principle of "Fistula First" has been key to changing the attitude to vascular access for haemodialysis. However, data from multiple observational studies and the International Paediatric Haemodialysis Network registry suggest that CVLs are associated with a significantly higher rate of infections and access dysfunction, and need for access replacement. Despite this, AVFs are used in only ∼25% of children on haemodialysis. It is important to provide the right access for the right patient at the right time in their life-course of renal replacement therapy, with an emphasis on venous preservation at all times. While AVFs may not be suitable in the very young or those with an anticipated short dialysis course before transplantation, many paediatric studies have shown that AVFs are superior to CVLs. CONCLUSIONS: Here we present clinical practice recommendations for AVFs and CVLs in children with ESKD. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system has been used to develop and GRADE the recommendations. In the absence of high quality evidence, the opinion of experts from the ESPN Dialysis WG is provided, but is clearly GRADE-ed as such and must be carefully considered by the treating physician, and adapted to local expertise and individual patient needs as appropriate.

Pro: Vascular access surveillance in mature fistulas: is it worthwhile?

Guidelines recommend regular screening of mature arteriovenous fistulas (AVFs) for preemptive repair of significant stenosis (≥50% lumen reduction) at high risk of thrombosis, identifiable from clinical signs of access dysfunction (monitoring) or by measuring access blood flow (Qa surveillance), which also enables stenosis detection in functional accesses. To compare the value of Qa surveillance versus monitoring, a meta-analysis was performed on the randomized controlled trials (RCTs) comparing the two screening strategies. It emerged that correcting stenosis identified by Qa surveillance significantly halved the risk of thrombosis [relative risk (RR) = 0.51, 95% confidence interval (CI) 0.35-0.73] and access loss (RR = 0.47, 95% CI 0.28-0.80) in comparison with intervention prompted by clinical signs of access dysfunction. One small RCT aiming to identify an optimal Qa threshold showed that stenosis repair at Qa >500 mL/min produced a significant 3-fold reduction in the risk of thrombosis (RR = 0.37, 95% CI 0.12-0.97) and access loss (RR = 0.36, 95% CI 0.09-0.99) in comparison with intervening when Qa dropped to <400 mL/min as per guidelines. To test the real-world benefits of Qa surveillance, the expected RCT-based thrombosis and access loss rates with Qa surveillance were compared with the rates with monitoring reported in observational studies: the expected thrombosis and access loss rates with surveillance were only lower than with monitoring when a Qa >500 mL/min was considered (2.4, 95% CI 1.0-4.6 and 2.2, 95% CI 0.7-5.0 versus 9.4, 95% CI 7.4-11.3 and 10.3, 95% CI 7.7-13.4 events per 100 AVFs-year, P ≤ 0.024), suggesting that in clinical practice adopting Qa surveillance may only be worthwhile at centres with high thrombosis and access loss rates associated with monitoring, and adopting Qa thresholds >500 mL/min for elective stenosis repair.

Optimal Cutoff Values for Radial Artery Diameter in Secondary Patency Rates and Risk Factors Affecting of Arteriovenous Fistulas.

BACKGROUND: Radial artery diameter on preoperative ultrasound has previously been investigated as a risk factor for the primary patency rate of arteriovenous fistulas. However, the cutoff values for long-term secondary patency rates have not been reported in detail. The present study verified the cutoff values that predict long-term secondary patency. METHODS: This was a single-center retrospective study. Among the arteriovenous fistula operations performed at our hospital from March 2008 to April 2013, 204 patients who underwent ultrasonography prior to the operation and whose secondary patency data were available were enrolled in this study. Secondary patency rates were calculated at 1, 3, and 5 years. Risk factors, including radial artery diameters (divided into quartiles), age, sex, diabetes mellitus, calcification, right versus left radial artery, and operative time (divided into quartiles) were examined using the log-rank test. Next, we performed multivariate Cox proportional hazard analysis using risk factors that were significant in the log-rank test. Further studies using time-dependent receiver operating characteristic curves were conducted to examine the cutoff values for radial artery diameters. RESULTS: The 1-, 3-, and 5-year secondary patency rates were 78.9%, 69.8%, and 67.4%, respectively. Significant risk factors included radial artery diameter and age ≥65 years. The cutoff value was 2.0 mm. CONCLUSIONS: A radial artery diameter cutoff value of 2.0 mm may increase the secondary patency rate of arteriovenous fistulas. This result agrees with the radial artery diameter reported for primary patency rates and is a clinically significant indicator.