A practical review of barriers and challenges to a definitive randomised trial of grafts versus fistula

A definitive randomised controlled trial of arteriovenous fistula (AVF) versus arteriovenous grafts (AVG) has been advocated for more than a decade, but as yet, none has been completed. The aim of this article is to summarise the theoretical barriers, review the difficulties in trial design and practicalities that have thus far prevented this from occurring.

Realtime monitoring of thrombus formation in vivo using a self-reporting vascular access graft

BACKGROUND

Chronic kidney disease (CKD) affects 10% of the global population costing over a hundred billion dollars per annum and leading to increased risk of cardiovascular disease. Many patients with CKD require regular haemodialyses. Synthetic arteriovenous grafts (AVG) are increasingly used to provide rapid vascular connection for dialysis. Initially, they have excellent patency rates but are critically limited by neointimal hyperplasia at the venous anastomosis, which drives subsequent thrombosis, graft failure and death.

METHODS

Here, we describe a system in which electrical impedance spectroscopy sensors are incorporated circumferentially into the wall of a synthetic arteriovenous graft. This is combined with an implantable radiotelemetry system for data transmission outside the patient. The system was tested using monolayers of endothelial and smooth muscle cells as well as swine blood and clots with explanted human carotid artery plaques. Sensor testing was then performed in vitro and the device was implanted in vivo in female swine.

RESULTS

The device can wirelessly report the accumulation of biological material, both cells and blood. Differences are also detected when comparing controls with pathological atheroma. In swine differences between blockage formation in a graft were remotely obtained and wireless reported.

CONCLUSIONS

Combining electrical impedance spectroscopy and an implantable radiotelemetry system enables graft surveillance. This has the potential to be used for early detection of venous stenosis and blood clot formation in real-time in vivo. In principle, the concept could apply to other cardiovascular diseases and vascular implantable devices.

Patient-Centred, Technology-Based Interventions for High Treatment Burden: An Overview of the State of the Art

This study provides an overview of recent efforts to develop technology-based interventions for patients with high treatment burden. Adoption of a technological intervention for high treatment burden will depend on a range of factors, including: the reliability and accessibility of the technology, patient factors including age, socio-economic factors, technology literacy, overall health status and personal priorities - as well as the perceived benefits provided by the technology intervention, from the perspectives of both patients and clinicians.

What are the observed procedural costs of vascular access surgery? Protocol for a systematic review

INTRODUCTION

A central component in the introduction of a novel surgical procedure or technique is an evaluation of its cost efficiency when compared with a benchmark standard of care. Accurate assessment of costs is thus essential in ensuring appropriate allocation of resources within a healthcare system. The treatment of kidney failure requires a significant volume of resources, and vascular access provision is the main modifiable cost. The costs of providing this service are obscured by generic NHS reference costs, which lack adequate granularity to allow meaningful comparisons between treatments. The aim of this systematic review will be to assess the reporting of procedural costs in all published economic analyses of vascular access surgery and perform a comparison of the reported procedural costs involved in arteriovenous fistula (AVF) and arteriovenous graft (AVG) creation. This will provide an estimate as to the accuracy of the NHS reference costs in this field.

METHODS AND ANALYSIS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines will be followed. A systematic search will be performed of the MEDLINE, Embase and Cochrane databases to identify full-text economic analyses of vascular access for haemodialysis in which the procedural cost of AVF or AVG creation is reported. Publications in English from 1 January 2000 to 30 August 2023, will be eligible for inclusion. Studies will be selected by title and abstract review, followed by a full-text review using inclusion and exclusion criteria. Studies not reporting the procedural costs of surgery will be excluded. Data collected will pertain to procedural costs of AVF and AVG creation. Costs will be adjusted to a common currency using a gross domestic product (GDP) deflator index and conversion rates based on purchasing power parities for GDP. Comparison with NHS reference costs will indicate their reliability for use in future economic analyses in this field.

ETHICS AND DISSEMINATION

Ethical approval is not required for this systematic review. Findings will be disseminated through peer-reviewed publications and conference presentations.

PROSPERO REGISTRATION NUMBER

CRD42023458779.

Cephalic arch stenosis: an analysis of outcome by type of first intervention

BACKGROUND

Cephalic arch stenoses (CAS) occur in near 70% of elbow arteriovenous fistulas. Percutaneous transluminal angioplasty (PTA) remains first-line treatment despite documented stent-grafts (SG) efficacy. The study aim is to report long-term outcomes based on initial treatment of CAS.

METHODS

Retrospective review of 12-year data in single tertiary centre. Outcomes included technical success, rupture rate, primary patency (PP), dialysis performance; categorical variables assessed via χ2 or Fisher's; nonparametric tests used for skewed data. Kaplan-Meier analysis used for PP and cumulative patency. Cox proportional hazard regression model to assess explanatory variables in PP.

RESULTS

One hundred one brachio- and radiocephalic fistulas with CAS were included. SG as first intervention had higher success than PTA (85% vs 61%, p = 0.003). Rupture occurred in 9/85 (10.6%) PTA vs 0% in SG (p = 0.046). In a subgroup with poor urea reduction rate (URR), both PTA and SG improved dialysis performance post-intervention (p = 0.002). SG demonstrated better PP than PTA (79,73,60% patency at 3, 6, 9 months; versus 71,51,47%; p = 0.195) and cumulative patency (73,61,61% at 1, 2, 3 years; versus 60,34,26%; p < 0.001). Of the variables analyzed, technical success of PTA was the only discriminating factor (coeff.-1.01; RR 35%, p = 0.035). Accesses that underwent secondary stenting performed better than primarily stented CAS (p = 0.01).

CONCLUSIONS

SG superiority is confirmed in CAS, particularly when angioplasty is unsuccessful. While PTA has short-lived benefits, it can improve dialysis performance. Other than higher success rate, primary CAS stenting did not have advantages compared to post-PTA stenting in our study. Other factors related to inflow, outflow, conduit characteristics are presumed to be involved in access longevity.

A national co-design workshop of a mobile-based application for vascular access as a patient decision aid

BACKGROUND

Increasing options for vascular access have increased the need for more effective communication to optimize patient engagement and ensure effective consent. An advanced prototype of the mobile application (VA App) was developed over 3 years as a patient decision aid. For the first time, entry to the 2021 UK Kidney Week was opened to all professions and patients and was held online. The VA App was presented in an inter-active session. This report summarizes the findings.

METHODS

A 30-min interactive session was allocated with the session delivered in four sections: (1) demographic data was collected; (2) an overall opinion was obtained about current patient information sources and satisfaction with these; (3) the participants were asked a series of eight questions regarding the main problem areas previously identified; (4) following a 6-min demonstration video, the participants were then re-asked the same questions to determine if the VA App would improve/worsen these areas.

RESULTS

Completed data from 30 participants showed great variation in all demographics. The most cited source was verbal and rated the best, whilst all other sources were felt to be poor by 90%. All eight aspects of current information sources rated poorly. There was a unanimous agreement that the VA App could make this better. Interestingly, when the eight aspects were ranked by order of the worst to best, this matched the order of the benefits of the VA App.

DISCUSSION

This is the first report of an on-line, multi-professional co-design workshop. With a unanimous view that current systems are very limited and that better patient information systems are required, the VA App was found to be a potential solution as a patient decision aid. Interestingly, paper leaflets were widely viewed as the least used and the least effective mechanism for communicating information to patients. Funding for a commercially produced mobile application has been secured and will be further tested in the near future.

Study protocol of a prospective single-arm multicenter clinical study to assess the safety and performance of the aXess hemodialysis graft: The pivotal study

BACKGROUND

Arteriovenous grafts (AVGs) are used for patients deemed unsuitable for the creation of an autogenous arteriovenous fistula (AVF) or unable to await maturation of the AVF before starting hemodialysis. However, AVGs are prone to infection and thrombosis resulting in low long-term patency rates. The novel aXess Hemodialysis Graft consists of porous polymeric biomaterial allowing the infiltration by cells and the growth of neotissue, while the graft itself is gradually absorbed, ultimately resulting in a fully functional natural blood vessel. The Pivotal Study will examine the long-term effectiveness and safety of the aXess Hemodialysis Graft.

METHODS

The Pivotal Study is a prospective, single-arm, multicenter study that will be conducted in 110 subjects with end-stage renal disease who are not deemed suitable for the creation of an autogenous vascular access. The primary efficacy endpoint will be the primary patency rate at 6 months. The primary safety endpoint will be the freedom from device-related serious adverse events at 6 months. The secondary endpoints will include the procedural success rate, time to first cannulation, patency rates, the rate of access-related interventions to maintain patency, the freedom from device-related serious adverse events and the rate of access site infections. Patients will be followed for 60 months. An exploratory Health Economic and Outcomes Research sub-study will determine potential additional benefits of the aXess graft to patients, health care institutions, and reimbursement programs.

DISCUSSION

The Pivotal study will examine the long-term performance and safety of the aXess Hemodialysis Graft and compare the outcome measures with historical data obtained with other graft types and autogenous AVFs. Potential advantages may include superior long-term patency rates and lower infection rates versus currently available AVGs and a shorter time to first cannulation compared to an autologous AVF. As such, the aXess Hemodialysis Graft may fulfill an unmet clinical need in the field of hemodialysis access.

The impact of renal artery stenting on therapeutic aims

Renal artery stenosis manifests as poorly-controlled hypertension, impaired renal function or pulmonary oedema, therefore the success of treatment is dependent on indication. This study aims to determine the outcomes of patients undergoing renal artery stenting (RASt) based on therapeutic aim compared to criteria used in the largest randomised trial. Retrospective case-note review of patients undergoing RASt between 2008-2021 (n = 74). The cohort was stratified by indication for intervention (renal dysfunction, hypertension, pulmonary oedema) and criteria employed in the CORAL trial, with outcomes and adverse consequences reported. Intervention for hypertension achieved significant reduction in systolic blood pressure and antihypertensive agents at 1 year (median 43 mmHg, 1 drug), without detrimental impact on renal function. Intervention for renal dysfunction reduced serum creatinine by a median 124 μmol/L, sustained after 6 months. Intervention for pulmonary oedema was universally successful with significant reduction in SBP and serum creatinine sustained at 1 year. Patients who would have been excluded from the CORAL trial achieved greater reduction in serum creatinine than patients meeting the inclusion criteria, with equivalent blood pressure reduction. There were 2 procedure-related mortalities and 5 procedural complications requiring further intervention. 5 patients had reduction in renal function following intervention and 7 failed to achieve the intended therapeutic benefit. Renal artery stenting is effective in treating the indication for which it has been performed. Previous trials may have underestimated the clinical benefits by analysis of a heterogenous population undergoing a procedure rather than considering the indication, and excluding patients who would maximally benefit.

Recruitment into randomised trials of arteriovenous grafts: A systematic review

Although randomised controlled trials (RCT) are considered the optimal form of evidence, there are relatively few in surgery. Surgical RCT are particularly likely to be discontinued with poor recruitment cited as a leading reason. Surgical RCT present challenges over and above those seen in drug trials as the treatment under study may vary between procedures, between surgeons in one unit, and between units in multi-centred RCT. The most contentious and debated area of vascular access remains the role of arteriovenous grafts, and thus the quality of the data that is used to support opinions, guidelines and recommendations is critical. The aim of this review was to determine the extent of variation in the planning and recruitment in all RCT involving AVG. The findings of this are stark: there have been only 31 RCT performed in 31 years, the vast majority of which exhibited major limitations severe enough to undermine the results. This underlines the need for better quality RCT and data, and further inform the design of future studies. Perhaps most fundamental is the planning for a RCT that accounts for the intended population, the uptake of a RCT and the attrition for the significant co-morbidity in this population.

Patients' and Clinicians' Perspectives on the Acceptability of Completing Digital Quality of Life Questionnaires During Routine Haemodialysis Clinics: A Mixed-Methods Study

Advanced chronic kidney disease is a serious and common medical condition with significant treatment choices incurring varying high treatment burdens. Better understanding on how to best collect quality of life (QoL) in this unique situation may help guide critical decisions. This study investigates the acceptability of digital QoL questionnaires completed during routine haemodialysis sessions. Qualitative data was collected from patient (n=23) and clinical researcher (n=2) interviews alongside analysis of data from questionnaires completed by patients (n=101) during a 6-week validation study. Interviews refined the content and format of digital QoL questionnaires and provided novel insights regarding how patients assessed and completed QoL questions. This study suggests collecting QoL data using digital tablet technology during routine haemodialysis clinics is both feasible and acceptable to patients and has provided novel insights that are not routinely available with traditional methods.

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

INTRODUCTION

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

METHODS AND ANALYSIS

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

ETHICS AND DISSEMINATION

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

TRIAL REGISTRATION NUMBER

ISRCTN14153938.

SPONSOR

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

A critical review of surgical strategies to minimise venous stenosis in arteriovenous grafts

It is inevitable that complications arising from surgical procedures are ascribed to surgical technique, and this applies to venous stenosis (VS) in arteriovenous grafts. However, despite a wide range of cellular studies, computer modelling, observational series and clinical trials, there remains uncertainty on whether surgical technique contributes to VS. This article reviews evidence from basic science, fluid dynamics and clinical data to try and rationalise the main surgical options to modify the occurrence of venous stenosis. There is sufficient data from diverse sources to make recommendations on clinical practice (size of target vein, shape of anastomosis, angle of approach, distance from venous needling, trauma to the target vein) whilst at the same time this emphasises the need to carefully report the practical aspects of surgical technique in future clinical trials.

Living donor kidney transplant following nephrectomy for renal artery stenosis with arterial reconstruction and viability assessment using ex vivo normothermic perfusion

Ex vivo normothermic perfusion (EVNP) is increasingly recognised as a viability tool to increase organ utilisation in deceased donor transplantation. We report the use of EVNP to assess graft perfusion quality following indication nephrectomy and back-bench arterial reconstruction in a case of renal artery stenosis, unamenable to endovascular treatment. Once explanted, it was not possible to effectively cold perfuse the graft through the main renal artery or collaterals. An arterial reconstruction was performed with patch angioplasty using the largest collateral creating a single common stem. EVNP was used to assess organ perfusion and, therefore, viability. Excellent global perfusion was evident alongside urine production, demonstrating that the arterial reconstruction was satisfactory. A patient with end-stage renal disease was consented with particular attention to the uncertainty of the underlying donor disease process and long-term outcome of the reconstruction. Primary function was achieved and recipient estimated glomerular filtration rate (eGFR) remains stable at 58 mL/min/1.73 m² at 6 months.

First Clinical Results of the Merit WRAPSODY™ Cell-Impermeable Endoprosthesis for Treatment of Access Circuit Stenosis in Haemodialysis Patients

PURPOSE

This prospective, observational first in human study evaluated the safety and effectiveness of WRAPSODY^TM Cell-impermeable Endoprosthesis (Merit Medical Systems, Inc.) in the treatment of arteriovenous fistula and arteriovenous graft access circuit stenosis.

MATERIALS AND METHODS

Investigators conducted a prospective analysis of 46 patients with access circuit stenosis from three centres. Treatment sites included the peripheral outflow veins (e.g. cephalic arch, basilic vein swing point; 16 fistula and 10 graft patients); the graft-vein anastomosis (9 patients); and the central veins (up to, but not including the SVC; 11 patients). Primary outcome measures included 30-day freedom from access circuit-related safety events and 30-day target lesion primary patency. Secondary outcome measures included procedural success; device- and procedure-related adverse events; target lesion primary patency; access circuit primary patency; and secondary patency. In-person follow-up was scheduled at 1, 3, 6, and 12 months. An independent data monitoring/clinical event committee adjudicated all reinterventions and device/procedure-relatedness for adverse events.

RESULTS

All initial procedures were successful. All but one patient was free from safety events through the first 30 days (97.8% (45/46)). This event was not device-related. Over the remainder of the study, one adverse event was adjudicated as possibly device-related. Six- and 12-month target lesion primary patency rates were 97.7% (42/43) and 84.6.% (33/39), respectively. Six- and 12-month access circuit primary patency rates were 84.4% (38/45) and 65.9% (29/44), respectively.

CONCLUSION

Results suggest that the study device is safe and effective for treatment of stenoses in the peripheral and central veins of arteriovenous access circuits.

LEVEL OF EVIDENCE

Level 2b, cohort study.

Early-cannulation arteriovenous grafts are safe and effective in avoiding recurrent tunneled central catheter infection

Objective

Tunneled central venous catheter infection (TCVCi) is a common complication that often necessitates removal of the TCVC and a further TCVC. Theoeretically, insertion of an early-cannualtion graft (ecAVG) early after TCVC infection is possible but not widely practiced with concerns over safety and infection in the ecAVG. With 8 years of ecAVG experience, the aim of this study was to compare the outcomes following TCVC infection, comparing replacement with TCVC (TCVCr) versus immediate ecAVG (ecAVGr).

Methods

Retrospective comparison of two cohorts, who underwent replacement of an infected TCVC either by an early cannulation graft (n = 18) or by a further central catheter (n = 39).

Data were abstracted from a prospectively completed electronic patient record and collected on patient demographics, TCVC insertion, duration and infection, including culture proven bacteriaemia and subsequent access interventions.

Results

18/299 patients identified from 2012-2020 had an ecAVG implanted as treatment for a TCVCi. In a one-year time-period (1/1/2015 -31/12/2015) out of 222 TCVC inserted, 39 were as a replacement following a TCVCi. No patient with an ecAVGr developed an immediate infection, nor complication from the procedure. The rate of subsequent vascular access infection was significantly more frequent for those with TCVCr than with an ecAVGr (0.6 vs. 0.1/patient/ 1000 HD days, p &lt; 0.000). The number of further TCVC required was significantly higher in the TCVCr group (7.1 vs. 0.4/patient/ 1000 HD days, p = 0.000).

Conclusion

An ecAVG early following a TCVC infection is safe, reduces the incidence of subsequent infectious complications and reduces the number of TCVC required, with a better functional patency.

A pilot study evaluating GSK1070806 inhibition of interleukin-18 in renal transplant delayed graft function

INTRODUCTION

Delayed graft function (DGF) following renal transplantation is a manifestation of acute kidney injury (AKI) leading to poor long-term outcome. Current treatments have limited effectiveness in preventing DGF. Interleukin-18 (IL18), a biomarker of AKI, induces interferon-γ expression and immune activation. GSK1070806, an anti-IL18 monoclonal antibody, neutralizes activated (mature) IL18 released from damaged cells following inflammasome activation. This phase IIa, single-arm trial assessed the effect of a single dose of GSK1070806 on DGF occurrence post donation after circulatory death (DCD) kidney transplantation.

METHODS

The 3 mg/kg intravenous dose was selected based on prior studies and physiologically based pharmacokinetic (PBPK) modeling, indicating the high likelihood of a rapid and high level of IL18 target engagement when administered prior to kidney allograft reperfusion. Utilization of a Bayesian sequential design with a background standard-of-care DGF rate of 50% based on literature, and confirmed via extensive registry data analyses, enabled a statistical efficacy assessment with a minimal sample size. The primary endpoint was DGF frequency, defined as dialysis requirement ≤7 days post transplantation (except for hyperkalemia). Secondary endpoints included safety, pharmacokinetics and pharmacodynamic biomarkers.

RESULTS

GSK1070806 administration was associated with IL18-GSK1070806 complex detection and increased total serum IL18 levels due to IL18 half-life prolongation induced by GSK1070806 binding. Interferon-γ-induced chemokine levels declined or remained unchanged in most patients. Although the study was concluded prior to the Bayesian-defined stopping point, 4/7 enrolled patients (57%) had DGF, exceeding the 50% standard-of-care rate, and an additional two patients, although not reaching the protocol-defined DGF definition, demonstrated poor graft function. Six of seven patients experienced serious adverse events (SAEs), including two treatment-related SAEs.

CONCLUSION

Overall, using a Bayesian design and extensive PBPK dose modeling with only a small sample size, it was deemed unlikely that GSK1070806 would be efficacious in preventing DGF in the enrolled DCD transplant population.

TRIAL REGISTRATION

NCT02723786.

Application and implications of a standardised reporting system for arteriovenous access graft infection

INTRODUCTION

The perception that arteriovenous graft infection (AVGi) is frequent and severe is not based on contemporary data from large units using modern AVG. Furthermore, older reports compounded misperceptions by using non-standardised reporting that prevents easy comparison against the alternative modalities. The aim of this article is to use a recently published reporting scheme to analyse the frequency, management and outcome of AVGi in a large series of sequential early-cannulation AVG with long-term follow-up.

METHODS

A single-center series analysis was performed of 277 early-cannulation AVG with minimum 1-year follow-up (total 120,082 days). Infections relating to the AVG were classified, root-cause analysed and the outcomes presented.

RESULTS

Sixteen percent of all AVG implanted (51 episodes) developed infection related to the AVG. Primary AVGi (related to the insertion procedure or within 28 days) occurred in 9 (3%); secondary AVGi (related to AVG in use) occurred 33 times (rate 0.27/1000 haemodialysis days), at a mean of 382 days, and tertiary AVGi (in AVG no longer in use) occurred nine times. Only 1/3 of all AVGi led to bacteraemia, and ½ did not lead to loss of functional access.

SUMMARY

AVG infection is not common, caused a systemic infection in only one-third, did not lead to metastatic infection, and importantly, was treatable without loss of access in one-half of all cases. Using an objective system that discriminates between aetiology and outcome allows a more complete objective understanding of relative infection risks and outcomes for AVG that can inform discussions with patients requiring vascular access for haemodialysis.

P1322EFFECTS OF HAEMODIALYSIS ARTERIOVENOUS FISTULA CREATION ON CARDIAC STRUCTURE AND FUNCTION

Background and Aims

Arteriovenous fistula (AVF) is considered the preferred type of access for maintenance haemodialysis. The creation of an AVF may contribute to maladaptive cardiovascular remodelling. We conducted a study to evaluate the effect of AVF creation on cardiac structure and function in patients with end-stage renal disease (ESRD).

Method

In this prospective cohort study, patients with ESRD listed for AVF creation underwent cardiac magnetic resonance imaging at baseline and at 6 weeks. All participants had ultrasound measurements of AVF blood flow at 6 weeks. The primary outcome was the change in left ventricular (LV) mass. Secondary outcomes included changes in LV volumes, left atrial volume, LV ejection fraction, LV global longitudinal strain, cardiac output/index, and septal thickness.

Results

A total of 65 patients were enrolled, of whom 40 had an AVF creation and completed both scans. Patients were divided into 2 groups based on AVF blood flows: 22 in the high flow group (≥ 600mL/min) and 18 in the low flow group (&lt; 600mL/min). On the second cardiac magnetic resonance scan, a mean increase of 7.4 g (95% CI, 1.1–13.7, P=0.02) was observed in LV mass; in the high flow group the mean increase was 15.5 g (95% CI, 7.3–23.8) compared with a small decrease of 2.5 g (95% CI, −10.6 to 5.6) in the low flow group (P=0.003). Significant increases in LV end-diastolic volumes, cardiac output, and cardiac index were also seen after AVF creation (P&lt;0.04). No significant changes were observed in LV ejection fraction (P=0.52), LV end-systolic volumes (P=0.12), and LV global longitudinal strain (P=0.21).

Conclusion

Creation of AVF in adults with ESRD resulted in significant increase of LV myocardial mass early after surgery.

Endovascular Retrieval of Intracaval Cement: A Fishing Net Technique

PURPOSE

To describe a novel endovascular technique for intracaval cement retrieval after spinal surgery.

TECHNIQUE

We produced a replica of the intracaval cement fragment and a 3D print to plan the endovascular procedure. A woven caval filter was modified with two drawstring sutures to be used as fishing net. We used a 10F sheath in the right internal jugular vein to place the caval filter proximal to the floating fragment, and a 24F sheath in the right femoral vein was the working access. After the deployment of the caval filter, the following steps were performed through the 24F sheath: (A) The drawstring sutures were snared and retrieved to the skin surface in the groin; (B) the fragment was secured with two snare catheters from the femoral access and one through the lumen of the caval filter; (C) the fragment was broken off with a snared guide wire at the base; (D) the smallest fragment was removed directly with the snare; (E) the larger dislodged fragment was controlled within the periprocedural caval filter by tightening the drawstring and removed through the 24F sheath.

CONCLUSION

Cement fragments located in the inferior vena cava after cement-augmented spinal surgery procedures can be safely removed by the described fishing net technique.

The Role of Qutenza® (Topical Capsaicin 8%) in Treating Neuropathic Pain from Critical Ischemia in Patients with End-Stage Renal Disease: An Observational Cohort Study

Objective

Current treatment strategies for painful critical ischemia in patients with end-stage renal disease (ESRD) are suboptimal. A drug that is non-renally excreted has minimal systemic absorption and does not require dose adjustment in renal failure is attractive. The aim of this study was to evaluate the safety and efficacy of Qutenza® (topical capsaicin 8%) for chronic neuropathic pain from critical ischemia in patients with ESRD.

Design and Setting

A prospective cohort study was conducted in a single-center, university teaching hospital.

Patients

Twenty patients with ESRD were treated with Qutenza® for neuropathic pain from critical limb ischemia.

Methods

Patients were followed-up at 1, 6 and 12 weeks post-treatment. The primary end point was the difference in visual analog scale (VAS) between baseline and week 12. Secondary end points were Brief Pain Inventory questionnaire (BPI) scores, quality of life assessment (EQ-5D) and patient global impression of change (PGIC). Safety and tolerability data were also collected. The trial was prospectively registered with clinical trials databases (EudraCT: 2012-001586-32; NCT01704313).

Results

There was significant reduction in VAS from baseline to week 12 (-20+/-7%; P = 0.02). There was a significant reduction in all seven domains of the BPI. Quality of life also improved at 12 weeks following treatment in two of the EQ-5D domains (mobility and pain). Qutenza® was well tolerated with no significant side effects in this patient cohort, which included 20% diabetics.

Conclusions

In this small, observational study Qutenza® treatment has been shown to be effective and well-tolerated to treat neuropathic pain from critical ischemia in patients with ESRD.

A unique case of acute embolus in a renal transplant with salvage by catheter-directed thrombolysis

INTRODUCTION

Acute renal transplant emboli can be disastrous and result in loss of the renal transplant. This case was successfully treated with thrombolysis.

CASE PRESENTATION

A 66-year-old female underwent a right-sided deceased heart-beating donor renal transplant. She had excellent transplant function but presented acutely three years later with pain in the transplanted kidney, an acute rise in serum creatinine and new onset atrial fibrillation. Bedside ultrasound scan demonstrated absent transplant perfusion. Emergency angiogram confirmed acute emboli in the transplant renal artery with some kidney perfusion. Thrombolysis with alteplase and anticoagulation with heparin was commenced. Serial imaging at 24 and 36 h demonstrated significant improvement in transplant perfusion. Following a period of supportive therapy, her transplant function recovered, although not to pre-morbid baseline levels.

CONCLUSION

Consider acute embolus in a renal transplant patient with acute kidney injury, transplant tenderness and cardiac arrhythmia. Early thrombolysis may salvage renal transplants and good transplant function may be regained.

Immediate access arteriovenous grafts versus tunnelled central venous catheters: study protocol for a randomised controlled trial

BACKGROUND

Autologous arteriovenous fistulae (AVF) are the optimal form of vascular access for haemodialysis. AVFs typically require 6 to 8 weeks to "mature" from the time of surgery before they can be cannulated. Patients with end-stage renal disease needing urgent vascular access therefore traditionally require insertion of a tunnelled central venous catheter (TCVC). TCVCs are associated with high infection rates and central venous stenosis. Early cannulation synthetic arteriovenous grafts (ecAVG) provide a novel alternative to TCVCs, permitting rapid access to the bloodstream and immediate needling for haemodialysis. Published rates of infection in small series are low. The aim of this study is to compare whether TCVC ± AVF or ecAVG ± AVF provide a better strategy for managing patients requiring immediate vascular access for haemodialysis.

METHODS/DESIGN

This is a prospective randomised controlled trial comparing the strategy of TCVC ± AVF to ecAVG ± AVF. Patients requiring urgent vascular access will receive a study information sheet and written consent will be obtained. Patients will be randomised to receive either: (i) TCVC (and native AVF if this is anatomically possible) or (ii) ecAVG (± AVF). 118 patients will be recruited. The primary outcome is systemic bacteraemia at 6 months. Secondary outcomes include culture-proven bacteraemia rates at 1 year and 2 years; primary and secondary patency rates at 3, 6, 12 and 24 months; stenoses; re-intervention rates; re-admission rate; mortality and quality of life. Additionally, treatment delays, impact on service provision and cost-effectiveness will be evaluated.

DISCUSSION

This is the first randomised controlled trial comparing TCVC to ecAVG for patients requiring urgent vascular access for haemodialysis. The complications of TCVC are considered an unfortunate necessity in patients requiring urgent haemodialysis who do not have autologous vascular access. If this study demonstrates that ecAVGs provide a safe and practical alternative to TCVC, this could instigate a paradigm shift in nephrology thinking and access planning.

TRIAL REGISTRATION

This study has been approved by the West of Scotland Research Ethics Committee 4 (reference no. 13/WS/0087, 28 August 2013) and is registered with the International Standard Randomised Controlled Trial Number Register (reference no. ISRCTN80588541 , 27 May 2014).

Delayed graft function is a syndrome rather than a diagnosis

OBJECTIVES

Delayed graft function is a significant prognostic indicator after renal transplantation. We hypothesized that delayed graft function is not a single entity, and different patterns of delayed graft function reflect various underlying pathological processes.

MATERIALS AND METHODS

An analysis of 762 renal transplants was performed, showing serum creatinine was charted serially for the first 30 days after transplant. Measurements were obtained: time on hemodialysis; time to peak creatinine; time for creatinine to half; time for creatinine to within 10% of baseline.

RESULTS

Four patterns of delayed graft function were identified. There was no association between pattern of delayed graft function, and 1-year graft survival or serum creatinine at 1 year. Time for creatinine to > 15 days was associated with a higher creatinine level at 1 year than it was with patients with time for creatinine to half < 5 days (300.6 ± 54.3 vs 211.3 ± 26.0 μmol/L; P < .01). Patients with 1-year creatinine concentrations > 180 μmol/L had longer time on hemodialysis and time for creatinine to half than did those with 1-year creatinine concentrations ≤ 180 μmol/L (9.2 ± 1.3 μmol/L vs 7.0 ± 0.7 μmol/L; P = .03; and 11.6 ± 1.7 μmol/L vs 6.0 ± 0.4 μmol/L; P < .001). Time for creatinine to half of 6.5 days (sensitivity 67.3%; specificity 79.4%; area under the curve, 0.70) was the best predictor of a 1-year creatinine concentration ≤ 180 μmol/L.

CONCLUSIONS

Delayed graft function is not a single entity; rather; it is the most common presentation of a heterogeneous variety of pathologies. Its rate of resolution of renal function is the best predictor of long-term graft outcome.

Renal function, uraemia and early arteriovenous fistula failure

BACKGROUND

Guidance varies regarding the optimal timing of arteriovenous fistula (AVF) creation. The aim of this study was to evaluate the association between uraemia, haemodialysis and early AVF failure.

METHODS

Immunoblotting and cell proliferation assays were performed on vascular smooth muscle cells (VSM) cells isolated from long saphenous vein samples to evaluate the cells' ability to proliferate when stimulated with uraemic (post-dialysis) and hyperuraemic (pre-dialysis) serum. Clinical data was collected prospectively for 569 consecutive radiocephalic (RCF) and brachiocephalic (BCF) fistulae. The primary outcome was AVF failure at 6 weeks. Dialysis status (haemodialysis (HD); pre-dialysis (Pre-D)), eGFR and serum urea were evaluated to determine if they affected early AVF failure.

RESULTS

Human VSM cells demonstrated increased capacity to proliferate when stimulated with hyperuraemic serum. There was no significant difference in early failure rate of either RCF or BCF depending on dialysis status (pre-D RCF 31.4% (n=188); pre-D BCF 22.4% (n=165); HD RCF 29.3% (n=99); HD BCF 25.9% (n=116); p=0.34). There was no difference in mean eGFR between those patients with early AVF failure and those without (11.2+/-0.2 ml/min/1.73 m2 vs. 11.6+/-0.4 ml/min/1.73 m2; p=0.47). Uraemia was associated with early AVF failure (serum urea: 35.0+/-0.7 mg/dl vs. 26.6+/-0.3 mg/dl (p<0.001)).

CONCLUSIONS

We present the first in vivo evidence of an association between adverse early AVF outcomes and uraemia. This is supported mechanistically by in vitro work demonstrating a pro-mitogenic effect of hyperuraemic serum. We hypothesise that uraemia-driven upregulation of VSM cell proliferation at the site of surgical insult in contributes to higher early AVF failure rates.

Abstract 554: Rabbit Arteriovenous Fistula Model and Identification of a Therapeutic Agent to Increase Fistula Patency

An arteriovenous fistula (AVF) is a vein graft which is created to permit vascular access allowing haemodialysis to be performed in renal failure patients. AVF using native tissues is the preferred surgical option; however AVF are associated with failure rates as high as 50% at 6 months. Failure is principally due to vascular cell proliferation, leading to the development of neointima causing stenosis and impaired blood flow. The aims of this study were to 1) develop a rabbit model of AVF remodelling, 2) investigate the contribution of cannulation injury in AVF remodelling and 3) identify a potential therapeutic which could be delivered topically to reduce AVF stenosis.

The proposed model was an AVF created between the femoral artery and vein of a New Zealand white rabbit. Briefly, the fistula was fashioned by creating a side to side anastomosis, followed by occlusion of the distal vein. Over phase I of the study (days 1-28) maturation of the vein was evident by the presence of a pulsatile flow in the venous branch of the AVF, as well as a significant increase in venous blood velocity from 55.2± 6.0cm/s at day 10 to 68.4± 3.1cm/s by day 28 (p<0.05). A degree of medial/adventitial thickening was also evident at this time point. Rabbits were assigned to 3 groups for phase II of the study (days 29-56). The control group received no intervention, the injury group received cannulation to the AVF every 48-72 hrs, and the injury plus diclofenac group received the same frequency of injury and topical diclofenac (1.16% of diclofenac diethylammonium) twice a day, 5 days a week. In the control group, vein wall width increased significantly from 10.5± 0.9μM in the counter lateral vein to 16.6± 1.6μM in the AVF (p<0.05). Cannulation injury caused vein wall thickness to significantly increase to 46.8± 5.7μM (p<0.05). With diclofenac treatment, vein wall width decreased significantly to 15.8± 1.8μM (p<0.05).

These results show for the first time that cannulation injury significantly contributes to AVF remodelling in vivo . Topical treatment with diclofenac, which has anti-inflammatory as well as anti-proliferative properties, appears to reduce injury driven remodelling within AVF. Therefore, topical diclofenac could be used as a prophylactic treatment to reduce vascular stenosis in AVF.

Acute kidney injury: outcomes and quality of care

BACKGROUND

Deficiencies in management have been highlighted as contributory factors in the death of many patients with acute kidney injury (AKI). However, there is little evidence addressing the quality of care provided to patients with milder AKI.

AIM

The aim of this study is to evaluate the quality of care provided to a non-select cohort of patients with AKI and evaluate discrepancies in causation, recognition and management.

DESIGN

Retrospective inception cohort study.

METHODS

Demographic data were collected for all 1577 patients admitted to a University Teaching Hospital during a 1-month period. Baseline, admission and peak creatinine were correlated with mortality and length of hospital admission. AKI was classified according to Kidney Disease Improving Global Outcomes criteria. A retrospective case note review of all patients with AKI was carried out to evaluate quality of documentation and clinical management of AKI. Multivariate analysis was undertaken to determine risk factors for AKI.

RESULTS

Incidence of AKI on admission was 4.6%. A further 10.3% developed AKI while in hospital. All cause mortality was 4-fold higher among patients with AKI compared with those without (19 vs. 3.8%; P < 0.001). Mortality was significantly higher in those patients who developed AKI while an in-patient compared with those with AKI on admission (27.3 vs. 11.8%; P < 0.001). Diabetes, clinician perception of frailty, age and treatment with angiotensin-converting enzyme inhibitor prior to admission were found to be independent risk factors for AKI. AKI was unrecognized in 23.5% of patients, two-thirds of whom were discharged without resolution of renal function. Significant weaknesses in management were poorly kept fluid balance charts (48.2%), failure to withhold nephrotoxic drugs (38.8%) and failure to act upon abnormal biochemistry (41%) in a timely fashion.

CONCLUSION

AKI is common in hospitalized patients and associated with a significant increase in hospital stay and mortality. AKI is often found in conjunction with other organ failure and in many cases is not preventable. Nevertheless clinicians need to be more vigilant of small creatinine rises to permit early intervention particularly among elderly and frail patients.

The prognostic significance of iliac vessel calcification in renal transplantation

BACKGROUND

Peripheral vascular disease and major extremity amputation are common in patients with established renal failure and are associated with considerable morbidity. Several studies have shown high rates of amputation following simultaneous pancreas-kidney transplantation, but there is minimal literature on the incidence of amputation following renal transplantation. Furthermore, there is little evidence regarding the best method of predicting which patients might be at risk of developing peripheral vascular complications after transplantation.

METHODS

We undertook a 5 year follow-up on the cohort of patients who were on our renal transplant waiting list 5 years ago (January 2007). At this time, it was standard practice within our unit for all patients to have routine pelvic x-rays to assess for vascular calcification of the iliac vessels at the time of activation onto the transplant waiting list. Any patients with moderate/severe calcification on x-ray, which may complicate transplantation, were referred for computed tomography angiogram (CTA) of their aorto-iliac vessels. Mortality, transplantation outcomes, and amputation rates at 5 years were correlated with the severity of calcification on preoperative imaging.

RESULTS

One hundred eighty-seven patients were on the waiting list for renal transplantation in January 2007 (92 men; mean age, 58.3 +/- 6.2 years). Ninety-three patients received a transplant during the subsequent 5 years. By January 2012, 82 patients had a functioning transplant, 45 remained on the waiting list (5 suspended), 40 patients had died, and 20 were alive but no longer on the waiting list. Seventy-three (39.5%) had moderate or severe calcification on plain x-ray and went on to have CTA. Of these patients, 16 (21.9%) had extensive calcification affecting all the iliac vessels and were removed from the waiting list as a result. Preoperative imaging was useful in determining the side for surgery in a further 18 patients (24.3%). Twenty-two patients developed vascular complications. Nineteen (86.4%) had moderate-severe vascular calcification on imaging. Four of the patients with vascular complications (18.2%) underwent transplantation (2 had below knee amputation (BKA) prior to transplantation; 1 developed distal ischemia on the same side as the transplantation 2 years postoperatively; 1 had bilateral above knee amputation (AKA) approximately 2 years after transplantation). Eleven (50%) of the patients with vascular complications were dead at 5 years of follow-up. Mortality and amputation rates were higher in patients with moderate-severe calcification than minimal calcification (30.1% vs 16.6%; P = .02 and 10.9% vs 1.8%; P = .003, respectively). There was no difference in rates of delayed graft function (DGF), biopsy-proven acute rejection (BPAR), or creatinine at 1 year between patients who underwent transplantation with moderate-severe calcification and those without, however, intraoperative vascular complications (26.7% vs 3%; P < .001), graft loss (28.1% vs 3.4%; P = .01), and death with a functioning transplant (9.7% vs 1.6%; P = .04) rates were higher in patients with extensive calcification compared with those without.

CONCLUSIONS

Plain x-ray of the pelvis is a useful screening tool to identify those patients who may require further detailed vascular imaging prior to transplantation. Amputation rates following renal transplantation are low and peripheral vascular disease (PVD) in isolation should not preclude transplantation. Nevertheless, significant vascular calcification is predictive of mortality both with and without transplantation and graft loss in patients with a renal transplant.

Five-year outcomes after a change from a cyclosporin-based to a 'low-dose' tacrolimus-based primary immunosuppression regimen for incident kidney transplants--the Glasgow experience

In January 2007, our centre changed from a cyclosporin (CyA)/azathioprine (Aza)/ prednisolone (Pred) primary immunosuppression regimen (with basiliximab induction and mycophenolate mofetil [MMF] for those at immunologically high risk) to a tacrolimus (Tac) (low dose)/MMF/Pred regimen with basiliximab induction, following presentation of Symphony trial results. This analysis assesses the impact of this change on 5-year outcomes. Three hundred consecutive renal-only transplants were identified: 140 from the 2005-06 era and 160 from the 2007-08 era. The proportions of living donor (37.5 vs. 22.9%; p = 0.04) and donors after circulatory death (11.9 vs. 5.0%; p = 0.03) were higher in the 2007-08 cohort. Five-year actuarial patient survival was higher in the 2007-08 cohort (96.8 vs. 87.1%; p = 0.003), with a trend toward higher 5-year transplant survival (84.7 vs. 76.3%; p = 0.08). Estimated glomerular filtration rate (eGFR) was higher than in the 2005-06 era at 1 (53.5 vs. 44.5 ml/min/1.73m2; p = 0.0006) and 3 years (50.9 vs. 43.4 ml/min/1.73m2; p = 0.02), with a trend toward higher eGFR at 5 years (41.8 vs. 49.6 ml/min/1.73m2; p = 0.09). Differences were consistent when living donor and deceased donor transplants were analysed separately. In a "real world" population, a change from a CyA-based to a Tac (low-dose)/MMF/Pred primary immunosuppression regimen has been associated with better 5-year outcomes.

Cellular senescence in pretransplant renal biopsies predicts postoperative organ function

Older and marginal donors have been used to meet the shortfall in available organs for renal transplantation. Post-transplant renal function and outcome from these donors are often poorer than chronologically younger donors. Some organs, however, function adequately for many years. We have hypothesized that such organs are biologically younger than poorer performing counterparts. We have tested this hypothesis in a cohort of preimplantation human renal allograft biopsies ( n = 75) that have been assayed by real-time polymerase chain reaction for the expression of known markers of cellular damage and biological aging, including CDKN2A, CDKN1A, SIRT2 and POT1. These have been investigated for any associations with traditional factors affecting transplant outcome (donor age, cold ischaemic time) and organ function posttransplant (serum creatinine levels). Linear regression analyses indicated a strong association for serum creatinine with pre-transplant CDKN2A levels ( p = 0.001) and donor age ( p = 0.004) at 6 months post-transplant. Both these markers correlated significantly with urinary protein to creatinine ratios ( p = 0.002 and p = 0.005 respectively), an informative marker for subsequent graft dysfunction. POT1 expression also showed a significant association with this parameter ( p = 0.05). Multiple linear regression analyses for CDKN2A and donor age accounted for 24.6% ( p = 0.001) of observed variability in serum creatinine levels at 6 months and 23.7% ( p = 0.001) at 1 year posttransplant. Thus, these data indicate that allograft biological age is an important novel prognostic determinant for renal transplant outcome.