Julien Al Shakarchi

Revisiting the risks of MRI with Gadolinium based contrast agents—review of literature and guidelines

Gadolinium based contrast agents (GBCA) have been linked to the occurrence of nephrogenic systemic fibrosis (NSF) in renal impaired patients. The exact interaction between the various different available formulations and occurrence of NSF is not completely understood, but has been postulated. This association has triggered public health advisory bodies to issue guidelines and best practice recommendations on its use. As a result, the reported incidence of NSF, as well as the published use of GBCA-enhanced magnetic resonance imaging in renal impairment, has seen a decline. Understanding of the events that led to these recommendations can increase clinical awareness and the implications of their usage. We present a review of published literature and a brief overview of practice recommendations, guidelines and manuals on contrast safety to aide everyday imaging practice.Teaching Points• Low risk gadolinium based contrast agents should be the choice in renal insufficiency.• Higher doses have been linked to NSF development. Doses should be as low as possible.• Clear documentation of date,dose and type of formulation used should be noted.• Post-scan dialysis should be arranged as soon as possible and feasible.• Pre-existing inflammatory state is a risk factor;liver insufficiency is not a contraindication.

Early cannulation grafts for haemodialysis: a systematic review

Purpose Arteriovenous grafts have advantages compared with central venous catheters for dialysis access and guidelines suggest their use as second choice after arteriovenous fistulas. Standard practice with expanded polytetrafluoroethylene (ePTFE) grafts has been to avoid cannulation for 2 weeks following placement, but new generation grafts have been marketed for their early cannulation properties allowing use as an alternative to central venous catheters for prompt access. The aim of this review is to search the current literature for evidence of early cannulation of new generation grafts and to assess their patency and complication rates. Methods Electronic databases were searched for studies assessing the use of early cannulation grafts for dialysis in accordance with PRISMA. The primary outcomes for this study were primary patency rate, primary-assisted patency rate and secondary patency rate. Secondary outcomes were timing of first cannulation, rates of access thrombosis, steal syndrome, pseudo-aneurysm and infection. Results Following strict inclusion/exclusion criteria by two reviewers, 15 studies were included in our review and divided into the different types of graft. Flixene, Avflo, Rapidax and Acuseal grafts showed that early cannulation within 72 h was possible; there was no evidence of the use of Vectra within 2 weeks of placement. All grafts showed similar patency and complication rates as previously published data on standard ePTFE grafts. Conclusion Our review showed that early cannulation is possible without detriment, but data did not allow specific graft recommendations. Therefore, we feel that a multicentre, randomised controlled trial is necessary to compare early cannulation grafts.

Systematic review of drug eluting balloon angioplasty for arteriovenous haemodialysis access stenosis

Background Native or prosthetic arteriovenous (AV) fistulas are preferred for permanent haemodialysis (HD) access. These are marked with circuit steno-occlusive disease leading to dysfunction or even failure. Late failure rates have been reported as high as 50%. Standard angioplasty balloons are an established percutaneous intervention for HD access stenosis. Reported restenosis rates remain high and practice guidelines recommend a wide 6-month primary patency (PP) of at least 50% for any intervention. Neointimal hyperplasia is one of the main causes for access circuit stenosis. Drug eluting balloon (DeB) angioplasty has been proposed as an alternative intervention to reduce restenosis by local drug delivery and possible inhibition of this process. Purpose To systematically assess the reported efficacy and safety of DeB angioplasty in percutaneous management of prosthetic and autologous HD access stenosis. Methods Protocol for the review was developed following the PRISMA-P 2015 statement. An electronic database (Medline, EMBASE, Clinical Trials.gov and Cochrane CENTRAL) search was conducted to identify articles reporting on the use of DeB intervention in HD AV access. Backward and forward citation search as well as grey literature search was performed. The MOOSE statement and PRISMA 2009 statement were followed for the reporting of results. Data from the included studies comparing DeBs with non-DeBs were pooled using a random effects metaanalysis model and reported separately on randomised and non-randomised studies. Results Six studies reported on 254 interventions in 162 participants (mean 27 ± 10 SD). The pooled mean and median duration of follow-up was 12 and 13 months (range 6-24 months). These comprised two randomised control trials (RCTs) and four cohort studies. Participants mean age was 64 ± 5 years and 61% were male. Target lesions (TLs) ranged from under 2 mm to 5.9 mm and 51 were reported as de novo stenosis. Device failure described as wasting of the DeB was reported in two studies (55% and 92.8%). At 6 months TL PP was reported between 70% to 97% for DeBs in the RCTs and cohort studies, and 0% to 26% for non-DeBs. TLs treated with DeBs were associated with a higher primary patency at 6 months as compared to non-DeB balloons (RCTs: odds ratio [OR] 0.25, 95% CI 0.08 to 0.77 and I2 = 19%, cohort studies: OR 0.10, 95% CI 0.03 to 0.31 and an I2 = 20%). No procedure-related major or minor complications were reported. Conclusions Current literature reports DeBs as being safe and may convey some benefit in terms of improved rate of restenosis when used to treat AV access disease. However, this body of evidence is small and clinically heterogeneous. A large multicentre RCT may help to clarify the role of DeBs in the percutaneous treatment of AV HD access stenosis.

Timing of cannulation of arteriovenous grafts: are we too cautious?

Background Timing of first cannulation of an arteriovenous graft has been the subject of great debate for clinicians worldwide. In this paper, we reviewed the current literature on the timing of first cannulation of arteriovenous grafts. Methods Searches of PubMed, Medline and the Cochrane Library were performed using specific search terms to identify articles, dealing primarily with the timing of dialysis graft cannulation. Results Following strict inclusion/exclusion criteria by two reviewers, eleven studies were included and divided into subgroups for ePTFE and new generation grafts. Conclusions The current literature does not seem to support the current guidelines as there is no evidence to suggest that a delay in cannulation of grafts will improve graft survival and patency.

Surgical techniques for haemodialysis access-induced distal ischaemia

Purpose Haemodialysis access-induced distal ischaemia (HAIDI) is a significant complication of vascular access creation, and has traditionally been difficult to manage without loss of access. Current treatment options include ligation, banding, distal revascularisation with interval ligation (DRIL), proximalisation of the arterial inflow (PAI) and revision using distal flow (RUDI). The purpose of this review was to evaluate the effectiveness of the different surgical techniques in the treatment of HAIDI. Methods Electronic databases were searched for studies assessing surgical techniques in the treatment of HAIDI in accordance with PRISMA. The primary outcome for the study was symptomatic relief for each technique, defined within each study. Secondary outcomes included comparison of early thrombosis rates following each different procedure. Results Following strict inclusion/exclusion criteria by two reviewers, twenty-seven studies of surgical interventions were included and divided into subgroups for banding, DRIL, PAI and RUDI procedures. Both DRIL and banding procedures were found to have high rates of symptomatic relief. In addition, the DRIL has a significantly lower rate of early thrombosis than banding although the more recent papers seem to suggest that early thrombosis is less of a problem in banding. PAI and RUDI showed some promise but there were too few studies to be able to make any clear conclusions. Conclusions All four procedures have high success rate in relieving ischaemic symptoms with the DRIL procedure having a significantly better vascular access patency rate than other techniques, although further well designed studies are required to compare all four surgical techniques.

Efficacy of the Ulnar-Basilic Arteriovenous Fistula for Hemodialysis: A Systematic Review

BACKGROUND The fistula first initiative has promoted arteriovenous fistulas (AVFs) as the vascular access of choice. To preserve as many future access options as possible, multiple guidelines advocate that the most distal AVF possible should be created in the first place. Generally, snuff box and radiocephalic (RC) are accepted and well-described sites for AVFs; however, the forearm ulnar-basilic (UB) AVF is seldom used or recommended. The aim of this study is to assess and systematically review the evidence base for the creation of the UB fistula and to critically appraise whether more attention should be given to this site. METHODS Electronic databases were searched for studies involving the creation of UB fistulas for dialysis in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The primary outcomes for this study were 1-year primary and secondary patency rates. Secondary outcomes were rates of hemodialysis access-induced distal ischemia (HAIDI) and infection. RESULTS After strict inclusion and/or exclusion criteria by 2 reviewers, 8 studies were included in our review. Weighted-pooled data reveal 1-year primary patency rate for UB AVFs of 53.0% (95% confidence interval [CI]: 40.1-65.8%) with a secondary patency rate of 72.0% (95% CI: 59.2-83.3). HAIDI and infection rates were low. CONCLUSIONS Our review has shown that the UB AVF may be a viable alternative when a RC AVF is not possible, and dialysis is not required urgently. It has adequate 1-year primary and secondary patency rates and extremely low risk of HAIDI. While it may be more challenging for both surgeons and dialysis nurses to make it a successful vascular access it offers a further option of distal access which may be overlooked.

Cost analysis of the Hemodialysis Reliable Outflow (HeRO) Graft compared to the tunneled dialysis catheter.

BACKGROUND In end-stage renal disease patients with central venous obstruction, who have limited vascular access options, the Hemodialysis Reliable Outflow (HeRO) Graft is a new alternative with a lower incidence of complications and longer effective device life compared to tunneled dialysis catheters (TDCs). We undertook an economic analysis of introducing the HeRO Graft in the UK. METHODS A 1-year cost-consequence decision analytic model was developed comparing management with the HeRO Graft to TDCs from the perspective of the National Health Service in England. The model comprises four 3-month cycles during which the vascular access option either remains functional for hemodialysis or fails, patients can experience access-related infection and device thrombosis, and they can also accrue associated costs. Clinical input data were sourced from published studies and unit cost data from National Health Service 2014-15 Reference Costs. RESULTS In the base case, a 100-patient cohort managed with the HeRO Graft experienced 6 fewer failed devices, 53 fewer access-related infections, and 67 fewer device thromboses compared to patients managed with TDCs. Although the initial device and placement costs for the HeRO Graft are greater than those for TDCs, savings from the lower incidence of device complications and longer effective device patency reduces these costs. Overall net annual costs are £2600 for each HeRO Graft-managed patient compared to TDC-managed patients. If the National Health Service were to reimburse hemodialysis at a uniform rate regardless of the type of vascular access, net 1-year savings of £1200 per patient are estimated for individuals managed with the HeRO Graft. CONCLUSIONS The base case results showed a marginal net positive cost associated with vascular access with the HeRO Graft compared with TDCs for the incremental clinical benefit of reductions in patency failures, device-related thrombosis, and access-related infection events in a patient population with limited options for dialysis vascular access.

Predictive models for arteriovenous fistula maturation

Purpose Haemodialysis (HD) is a lifeline therapy for patients with end-stage renal disease (ESRD). A critical factor in the survival of renal dialysis patients is the surgical creation of vascular access, and international guidelines recommend arteriovenous fistulas (AVF) as the gold standard of vascular access for haemodialysis. Despite this, AVFs have been associated with high failure rates. Although risk factors for AVF failure have been identified, their utility for predicting AVF failure through predictive models remains unclear. The objectives of this review are to systematically and critically assess the methodology and reporting of studies developing prognostic predictive models for AVF outcomes and assess them for suitability in clinical practice. Methods Electronic databases were searched for studies reporting prognostic predictive models for AVF outcomes. Dual review was conducted to identify studies that reported on the development or validation of a model constructed to predict AVF outcome following creation. Data were extracted on study characteristics, risk predictors, statistical methodology, model type, as well as validation process. Results We included four different studies reporting five different predictive models. Parameters identified that were common to all scoring system were age and cardiovascular disease. Conclusions This review has found a small number of predictive models in vascular access. The disparity between each study limits the development of a unified predictive model.

End-stage vascular access failure: can we define and can we classify?

Background Renal replacement therapy using dialysis has evolved dramatically over recent years with an improvement in patient survival. With this increased longevity, a cohort of patients are in the precarious position of having exhausted the standard routes of vascular access. The extent of this problem of failed access or ‘desperate measures’ access is difficult to determine, as there are no uniform definitions or classification allowing standardization and few studies have been performed. The aim of this study is to propose a classification of end-stage vascular access (VA) failure and subsequently test its applicability in a dialysis population. Methods Using anatomical stratification, a simple hierarchical classification is proposed. This has been applied to a large dialysis population and in particular to patients referred to the complex access clinic dedicated to patients identified as having exhausted standard VA options and also those dialysing on permanent central venous catheters (CVC). Results A simple classification is proposed based on a progressive anatomical grading of (I) standard upper arm options exhausted, (II) femoral options exhausted and (III) other options exhausted. These are further subdivided anatomically to allow ease of classification. When applied to a complex group of patients (n = 145) referred to a dedicated complex access clinic, 21 patients were Class I, 26 Class II and 2 Class III. Ninety-six patients did not fall into the classification despite being referred as permanent CVC. Conclusions The numbers of patients who have exhausted definitive access options will continue to increase. This simple classification allows the scope of the problem and proposed solutions to be identified. Furthermore, these solutions can be studied and treatments compared in a standardized fashion. The classification may also be applied if patients have the option of transplantation where iliac vessel preservation is desirable and prioritization policies may be instituted.

Novel use of infrared thermal imaging to predict arteriovenous fistula patency and maturation

Objective The arteriovenous fistula (AVF) is the preferred method of long-term haemodialysis. However, it has been shown to have a substantial rate of maturation failure. The formation of an AVF creates haemodynamic changes to blood flow in the arm with diversion of blood away from the distal circulation into the low pressure venous system, in turn, leading to thermal changes distally. In this study, we aimed to assess the novel use of infrared thermal imaging as a predictor of arteriovenous maturation. Methods A prospective cohort study was conducted on 100 consecutive patients who had AVF formation from December 2015 to June 2016. Infrared thermal imaging was undertaken pre- and post-operatively on the day of surgery to assess thermal changes to the arms and to assess them as predictors of clinical patency and functional maturation. Results For clinical patency, infrared thermal imaging was found to have a positive predictive value of 88% and a negative predictive value of 86%. For functional maturation, it was found to have a positive predictive value of 84%, a negative predictive value of 95%. In addition, it was shown to have superiority to the commonly used intra-operative predictor of thrill as well as other independent pre-operative patient factors. Conclusions Infrared thermal imaging has been found to be a very useful tool in accurately predicting fistula patency and maturation.