Practical aspects of arteriovenous fistula formation in the pediatric population

Early-cannulation arteriovenous grafts: Multidisciplinary learning is essential to optimize outcomes

BACKGROUND

It is likely that there will be an increasing role for early-cannulation arteriovenous grafts (ecAVG) with a wider recognition of the need to tailor vascular access to avoid futile procedures and unnecessary TCVC. However, experience of these products is not common and limited to early surgical adopters, with little information on the systemic changes and multi-disciplinary care needed to optimize outcomes. The aim of this study was to report the impact of a multi-disciplinary approach on quantifiable outcomes.

METHODS

A retrospective analysis of a prospectively maintained database of 295 ecAVG implanted over an 8-year time-period was performed. Indicative outcomes were chosen to reflect nephrology (patient selection), nursing care (cannulation complications of infection and pseudoaneurysm) and radiology (thrombosis) on cumulative impact (functional patency) over three distinct time periods.

RESULTS

The incidence of ecAVG increased 10-fold over the three time periods. The use of ecAVG changed significantly from salvage tertiary access to TCVC avoidance and salvage of existing AVF. Nursing complications reduced markedly with significantly fewer over-cannulation episodes and pseudo-aneurysms. With an improved pro-active surveillance programme, the time to first thrombosis doubled and the risk of thrombosis halved. Ultimately this resulted in significantly improved functional patency with a risk of ecAVG loss less than one-third by the last time-period.

CONCLUSIONS

All aspects of ecAVG use require scrutiny and critical appraisal. Failure or success is not simply achieved by performing good technical surgery with an efficacious product, but by the care taken across a wide range of elements spanning case selection, implantation, use and maintenance.

Vascular access challenges in hemodialysis children

BACKGROUND

Hemodialysis (HD) success is dependent mainly on vascular access (VA). The aim of this study is to share the experience of Pediatric Nephrology Unit (PNU), Cairo University Children's Hospital (CUCH), with VA-related obstacles in end stage kidney disease (ESKD) HD children.

METHODS

This is a retrospective analysis of VA related data of 187 ESKD children received regular HD over 3 year duration (2019-2021). Kaplan-Meier curves were used to present arteriovenous fistula (AVF) and cuffed catheters survivals.

RESULTS

Uncuffed central venous catheter (CVC) was the primary VA for HD in up to 97.3% with 2.7% of patients had AVF performed and attained maturation before initiation of regular HD. Fifty-six (29.9%) patients have inserted 120 tunneled CVCs. AVFs & AV grafts (AVF) were performed in 79 (42.2%) and 6 (3.2%) patients respectively. There were 112 uncuffed CVCs implanted beneath the screen in Rt internal jugular vein (IJV) (44%) Lt IJV (17%), right internal mammary vein (2.7%) while Trans hepatic (TH) technique was used to place 39 uncuffed CVCs (34%) in the inferior vena cava (IVC). Catheter-related bacteremia (CRB) was the most frequent complication in uncuffed and cuffed CVCs (2.58 / 100 catheters day and 10.1 /1000 catheter days respectively). AVFs achieved a high success rate (83%) after 757.71 ± 512.3 functioning days.

CONCLUSION

Native AVF is the preferred VA for pediatric HD but its creation is limited by the small sized vessels where non-cuffed CVC could be a reasonable relatively long-term alternative. Challenging situations (occluded central veins) could benefit from TH technique of CVC insertion in IVC.

Impact of Isometric Exercise in Adolescents With End Stage Kidney Disease and Unsuitable Vessels For An Autologous Arteriovenous Fistula

INTRODUCTION

Despite the lack of calcification, to perform a native Arteriovenous Fistula (AVF) in young patients may pose a challenge due to small vessel diameter. We report a case series with no options of AVF in which vessel caliber improvement after isometric exercise allowed for radiocephalic fistula creation in all of them.

METHODS

Since 2017 to 2019, four patients were referred to our unit to create an AVF. Following a first assessment with physical examination and doppler ultrasound, none of them were eligible for AVF performance due to small vessel caliber. Once they were considered unsuitable for it, they started an isometric exercise program.

RESULTS

Age ranged from 13 to 19 years. There were three males and one female. Two were in predialysis and two in hemodialysis program. Initial diameters of the forearm cephalic vein and the radial artery respectively were: case A < 1.5/2.3 mm, case B 1.5/1.6 mm, case C < 1.5/1.6 mm and case D 2.1/1.3 mm. Median duration of exercise program was 13 weeks (range 5-23). Post-exercise vessel diameters were: case A 2.7/2.3 mm, case B 2.5/2 mm, case C 2.8/1.8 mm and case D 2.7/2 mm. Radiocephalic AVF were performed in the four cases. After a median follow up of 19 months (range 9-30 months), 75% of patients required further interventions but all of them had a functional AVF.

CONCLUSIONS

In these four cases isometric preoperative exercise allowed the creation of AVF. Without the improvement in vessel diameter observed afterwards, all of them would have been rejected for AVF performance. Despite the high rate of adjunctive interventions needed, given the safety of the program and the potential risks of Central Venous Catheters, we consider it a valuable option.

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.

Update on the creation and maintenance of arteriovenous fistulas for haemodialysis in children

Arteriovenous fistulas (AVFs) are widely used for haemodialysis (HD) in adults with stage 5 chronic kidney disease (CKD 5) and are generally considered the best form of vascular access (VA). The 'Fistula First' initiative in 2003 helped to change the culture of VA in adults. However, this cultural change has not yet been adopted in children despite the fact that a functioning AVF is associated with lower complication rates and longer access survival than a central venous line (CVL). For children with CKD 5, especially when kidney failure starts early in life, there is a risk that all VA options will be exhausted. Therefore, it is essential to develop long-term strategies for optimal VA creation and maintenance. Whilst AVFs are the preferred VA in the paediatric population on chronic HD, they may not be suitable for every child. Recent guidelines and observational data in the paediatric CKD 5 population recommend switching from a 'Catheter First' to 'Catheter Last' approach. In this review, recent evidence is summarized in order to promote change in current practices.

"Save the Vein" Initiative in Children With CKD: A Quality Improvement Study

RATIONALE & OBJECTIVE

The preferred vascular access for hemodialysis recipients is an arteriovenous fistula in the nondominant arm. Prior placement of a peripheral intravenous (PIV) catheter can lead to vascular injury and limit options for arteriovenous fistula creation, a particular problem for children, who may need hemodialysis for their entire lifetime. We instituted an initiative to increase the frequency of PIV catheter placement in the dominant arm for hospitalized pediatric patients with advanced chronic kidney disease (CKD).

STUDY DESIGN

Quality improvement initiative.

SETTING & PARTICIPANTS

Children with CKD stage 3-5, receiving dialysis, and/or following kidney transplantation who were hospitalized at one children's hospital between September 2018 and August 2020.

QUALITY IMPROVEMENT ACTIVITIES

Retrospective data on PIV catheter location for patients from January 1 to June 30, 2017, served as baseline data. Quality improvement activities consisted of: 1) education of the multidisciplinary treatment team, patients, and parents regarding importance of vein preservation; 2) placement of individualized notes in the electronic medical record identifying the preferred arm for PIV catheter placement; 3) use of "restricted extremity" arm bands; and 4) vascular access team participation to minimize attempts for PIV catheter placement.

OUTCOME

Monthly compliance with placement of PIV catheters in dominant arms.

ANALYTICAL APPROACH

Location of PIV catheter placements were determined monthly and used to create run charts describing compliance.

RESULTS

At baseline and before institution of this initiative, 34 of 72 (47%) PIV catheters were placed in patients' dominant arms, with only 2 of 8 (25%) PIV catheters placed in the dominant arm for children aged<5 years. After instituting the initiative, 345 of 371 (93%) PIV catheters were placed in the dominant arm of 93 children; in children aged<5 years, 58 of 62 (94%) PIV catheters were placed in the dominant arm. Only 38 of 371 (10%) PIV catheters were placed in the antecubital vein.

LIMITATIONS

Single-center study.

CONCLUSIONS

Education regarding the importance of vein preservation, along with implementation of a standardized process for identifying children for whom vein preservation is important, can help direct PIV catheter placement and potentially preserve vasculature in pediatric patients with CKD.

Left innominate vein creation using left internal jugular vein tunneled to right internal jugular vein

BACKGROUND

Left innominate vein occlusion is a known complication of pacemaker and central venous catheter placement. For dialysis-dependent patients with an arteriovenous fistula (AVF), this can prevent successful hemodialysis and may require surgical intervention.

CASE REPORT

An 8-month-old male was diagnosed with hemolytic uremic syndrome and became dialysis-dependent at 11 months of age. After multiple vascular access and peritoneal dialysis complications, the patient had construction of a brachiobasalic AVF in his left arm at 13 years old. While waiting for the AVF to mature, an attempt to remove a previously placed left subclavian vein port-a-cath was unsuccessful and a follow-up imaging revealed that the vessel had become occluded. The fistula remained patent, but due to arm swelling and venous obstruction, his fistula was not accessible. Multiple attempts to percutaneously cross the left innominate vein were unsuccessful and the patient was referred for surgical intervention. At 15 years old, the patient was taken to the operating room for transposition of the left internal jugular vein (LIJ) to the right internal jugular vein (RIJ). The LIJ was transected under the mandible and anastomosed to the RIJ. Subsequently the patient underwent VWING insertion rather than venous transposition for constant site dialysis. Although he has required frequent transcatheter dilation of the LIJ-RIJ anastomosis, the patient was successfully dialyzed using this fistula for 5 years. The patient received a cadaveric renal transplant at 5 years 20 days.

CONCLUSIONS

In cases of left innominate vein stenosis, transposing the LIJ can create a new left innominate vein that can alleviate venous hypertension and preserve fistula function. This procedure avoids sternotomy and only requires one anastomosis.

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.

Microsurgery for "wrist" arteriovenous fistula creation in children: a retrospective cohort study

INTRODUCTION

Creating functional arteriovenous fistulae (AVF) at the wrist is challenging in paediatric patients because of the small calibre of the blood vessels.

METHODS

We report our experience with AVF surgery in children younger than 15 years of age using microsurgical techniques. Twenty-five patients underwent AVF surgery between 2003 and 2015 (20 for haemodialysis, 4 for plasmapheresis and 1 for parenteral nutrition). Median (range) age was 9 (2-15) years and median weight was 24 (8-61) kg.

RESULTS

The one-month occlusion rate was 8%. The primary and secondary patency rates at 1, 2, 3 years were: 60%, 49%, 42%, and 82%, 72%, 54%, respectively. The median (range) maturation time was 4.53 (0.5-11.2) months. We found no statistically significant effect of patient age, body weight, type of AVF and indication for AVF creation on the primary and secondary patency rates.

CONCLUSIONS

Microsurgical AVF creation at the wrist can be performed with satisfactory results and should be the preferred technique in the paediatric population.

The molecular mechanisms of hemodialysis vascular access failure

The arteriovenous fistula has been used for more than 50 years to provide vascular access for patients undergoing hemodialysis. More than 1.5 million patients worldwide have end stage renal disease and this population will continue to grow. The arteriovenous fistula is the preferred vascular access for patients, but its patency rate at 1 year is only 60%. The majority of arteriovenous fistulas fail because of intimal hyperplasia. In recent years, there have been many studies investigating the molecular mechanisms responsible for intimal hyperplasia and subsequent thrombosis. These studies have identified common pathways including inflammation, uremia, hypoxia, sheer stress, and increased thrombogenicity. These cellular mechanisms lead to increased proliferation, migration, and eventually stenosis. These pathways work synergistically through shared molecular messengers. In this review, we will examine the literature concerning the molecular basis of hemodialysis vascular access malfunction.

Timing of first arteriovenous fistula cannulation in children on hemodialysis

BACKGROUND

Due to lower complication rates in comparison to central venous catheter (CVC) arteriovenous fistulas (AVFs) are now the preferred hemodialysis access. Recommendations for the first access cannulation range from 6 to 12 weeks, which could lead to temporary or even permanent preference for CVC while awaiting the maturation of the newly created AVF. The aim of this study was to evaluate the influence of first cannulation of AVFs on primary (PP) and secondary (SP) patency rates in children on hemodialysis (HD).

METHODS

This was a retrospective cohort study of 42 pediatric patients with a median age of 14 (range 7-17) years. At the time of surgical AVF creation 21 patients (end-stage renal disease) were still on HD via CVC or peritoneal catheter, while 21 were pre-emptive with initiation of HD expected within a few weeks. All patients received an AVF by the same experienced surgeon between February 1993 and May 2014. Primary failure (PF) was defined as the inability to use the AVF even once due to absent maturation or occlusion within 4 weeks after creation. PP was defined as the interval from time of access placement to any intervention designed to maintain or reestablish patency, to access thrombosis or the time of measurement of patency, while SP was defined as the total lifespan from creation to access abandonment, end of follow-up or loss.

RESULTS

Primary failure was observed in six (14.3 %) of 42 AVFs (all radiocephalic fistulas) within the first 10 days after cannulation. Excluding PF, the PP/SP rates at 1, 3, 6, 12, 18 and 24 months were 100/100, 91/99, 86/98, 76/95, 55/85 and 44/77 %, respectively. There was a significant decrease in PP when first cannulation was performed within the first 30 days after creation compared to first cannulation performed after 30 days (p = 0.004). In terms of PP/SP outcome and timing of the first cannulation, there was no significant difference in thee outcome of PP/SP between first cannulation within the first 45 days after creation and that after 45 days (p = 0.091/0.883).

CONCLUSIONS

The findings suggest that cannulation of AVF within 30 days after surgical creation reduces PP, while SP may be influenced less by time until cannulation. We also found no significant differences in PP after maturing periods of >45 days.

Outcomes of Arteriovenous Fistula for Hemodialysis in Pediatric and Adolescent Patients

Purpose:

This retrospective review aimed to report the outcomes of arteriovenous fistula (AVF) and to evaluate the suitability of AVF as a permanent vascular access in pediatric populations.

Materials and Methods:

Data were collected for all patients aged 0 to 19 years who underwent AVF creation for hemodialysis between January 2000 and June 2014.

Results:

Fifty-two AVFs were created in 47 patients. Mean age was 15.7±3.2 years and mean body weight was 46.7±15.4 kg. Of the 52 AVFs, 43 were radiocephalic AVFs, 7 were brachiocephalic AVFs and 2 were basilic vein transpositions. With a mean follow-up of 49.7±39.2 months, primary patency was 60.5%, 51.4%, and 47.7% at 1, 3, and 5 years, respectively and secondary patency was 82.7%, 79.2% and 79.2% at 1, 3, and 5 years, respectively. Age, body weight, AVF type, the presence of a central venous catheter, use of anticoagulation therapy, and history of vascular access failure were not significantly associated with patency rates. There were 9 cases (17.3%) of primary failure; low body weight was an independent predictor. Excluding cases of primary failure, the mean duration of maturation was 10.0±3.7 weeks. During follow-up, 20 patients (42.6%) underwent kidney transplantation, with a median interval to transplantation of 36 months.

Conclusion:

AVF creation in children and adolescents is associated with acceptable long-term durability, primary failure rate and maturation time. Considering the waiting time and limited kidney graft survival, placement of AVFs should be considered primarily even in patients expected to receive transplantation.

Future research directions to improve fistula maturation and reduce access failure

With the increasing prevalence of end-stage renal disease, there is a growing need for hemodialysis. Arteriovenous fistulae (AVF) are the preferred type of vascular access for hemodialysis, but maturation and failure continue to present significant barriers to successful fistula use. AVF maturation integrates outward remodeling with vessel wall thickening in response to drastic hemodynamic changes in the setting of uremia, systemic inflammation, oxidative stress, and pre-existent vascular pathology. AVF can fail due to both failure to mature adequately to support hemodialysis and development of neointimal hyperplasia that narrows the AVF lumen, typically near the fistula anastomosis. Failure due to neointimal hyperplasia involves vascular cell activation and migration and extracellular matrix remodeling with complex interactions of growth factors, adhesion molecules, inflammatory mediators, and chemokines, all of which result in maladaptive remodeling. Different strategies have been proposed to prevent and treat AVF failure based on current understanding of the modes and pathology of access failure; these approaches range from appropriate patient selection and use of alternative surgical strategies for fistula creation, to the use of novel interventional techniques or drugs to treat failing fistulae. Effective treatments to prevent or treat AVF failure require a multidisciplinary approach involving nephrologists, vascular surgeons, and interventional radiologists, careful patient selection, and the use of tailored systemic or localized interventions to improve patient-specific outcomes. This review provides contemporary information on the underlying mechanisms of AVF maturation and failure and discusses the broad spectrum of options that can be tailored for specific therapy.

The Biology of Hemodialysis Vascular Access Failure

Arteriovenous fistulas (AVFs) are essential for patients and clinicians faced with end-stage renal disease (ESRD). While this method of vascular access for hemodialysis is preferred to others due to its reduced rate of infection and complications, they are plagued by intimal hyperplasia. The pathogenesis of intimal hyperplasia and subsequent thrombosis is brought on by uremia, hypoxia, and shear stress. These forces upregulate inflammatory and proliferative cytokines acting on leukocytes, fibroblasts, smooth muscle cells, and platelets. This activation begins initially with the progression of uremia, which induces platelet dysfunction and primes the body for an inflammatory response. The vasculature subsequently undergoes changes in oxygenation and shear stress during AVF creation. This propagates a strong inflammatory response in the vessel leading to cellular proliferation. This combined response is then further subjected to the stressors of cannulation and dialysis, eventually leading to stenosis and thrombosis. This review aims to help interventional radiologists understand the biological changes and pathogenesis of access failure.

A dedicated vascular access clinic for children on haemodialysis: Two years' experience

BACKGROUND

Arteriovenous fistula (AVF) formation for long-term haemodialysis in children is a niche discipline with little data for guidance. We developed a dedicated Vascular Access Clinic that is run jointly by a transplant surgeon, paediatric nephrologist, dialysis nurse and a clinical vascular scientist specialised in vascular sonography for the assessment and surveillance of AVFs. We report the experience and 2-year outcomes of this clinic.

METHODS

Twelve new AVFs were formed and 11 existing AVFs were followed up for 2 years. All children were assessed by clinical and ultrasound examination.

RESULTS

During the study period 12 brachiocephalic, nine basilic vein transpositions and two radiocephalic AVFs were followed up. The median age (interquartile range) and weight of those children undergoing new AVF creation were 9.4 (interquartile 3-17) years and 26.9 (14-67) kg, respectively. Pre-operative ultrasound vascular mapping showed maximum median vein and artery diameters of 3.0 (2-5) and 2.7 (2.0-5.3) mm, respectively. Maturation scans 6 weeks after AVF formation showed a median flow of 1277 (432-2880) ml/min. Primary maturation rate was 83 % (10/12). Assisted maturation was 100 %, with two patients requiring a single angioplasty. For the 11 children with an existing AVF the maximum median vein diameter was 14.0 (8.0-26.0) mm, and the median flow rate was 1781 (800-2971) ml/min at a median of 153 weeks after AVF formation. Twenty-two AVFs were used successfully for dialysis, a median kt/V of 1.97 (1.8-2.9), and urea reduction ratio of 80.7 % (79.3-86 %) was observed. One child was transplanted before the AVF was used.

CONCLUSIONS

A multidisciplinary vascular clinic incorporating ultrasound assessment is key to maintaining young children on chronic haemodialysis via an AVF.