Infection of hemodialysis arteriovenous grafts

First-in-human feasibility study of the aXess graft (aXess-FIH): 6-Month results

OBJECTIVE

The creation of an arteriovenous fistula (AVF) is considered the most effective hemodialysis (HD) vascular access. For patients who are not suitable for AVF, arteriovenous grafts (AVGs) are the best access option for chronic HD. However, conventional AVGs are prone to intimal hyperplasia, stenosis, thrombosis, and infection. Xeltis has developed an AVG as a potential alternative to currently available AVGs based on the concept of endogenous tissue restoration. The results of the first 6-month follow-up are presented here.

METHODS

The aXess first-in-human (FIH) study [NCT04898153] is a prospective, single-arm, multicenter feasibility study that evaluates the early safety and performance of the aXess Hemodialysis Graft. A total of 20 patients with end-stage renal disease were enrolled across six European investigational sites.

RESULTS

At 6-months follow-up, all grafts were patent with primary and secondary patency rates were 80% and 100%, respectively. Three patients required a re-intervention to maintain graft patency, while one re-intervention was required to restore patency. One graft thrombosis and zero infections were reported.

CONCLUSION

The expected advantages of the novel aXess Hemodialysis Graft over conventional AVGs would be evaluated by the analysis on long-term safety and effectiveness during the 5-year follow-up of the currently ongoing trial.

Taurolidine Irrigation Reduces Relapse and Recurrence of Hemodialysis Access Infection

BACKGROUND

Infection of hemodialysis access is a clinically important concern and can lead to increased morbidity and mortality among patients on hemodialysis. In this study, we aimed to determine whether using taurolidine as an irrigating antiseptic after drainage of pus or removal of infected tissue and graft during surgery decreases the relapse and recurrence of infection.

METHODS

Between January 2016 and December 2023, 48 episodes in 38 patients hospitalized and treated for hemodialysis access infections were examined. Relapse, recurrence, and mortality of infection were analyzed in patients who received additional taurolidine irrigation versus those who did not. After drainage alone or after total or partial graft removal, all patients received massive irrigation with normal saline. The episodes of infection were examined consecutively during follow-up.

RESULTS

The majority (97.9%) of hemodialysis access infections was arteriovenous grafts (AVGs) or interposed grafts from native veins. In AVGs, infections occurred primarily after a median of 523 days from the first needling. All prosthetic materials that were the infection foci were removed in 58.3% of the cases, with partial resection and bypass or drainage performed in the remaining cases. The most common pathogen was Staphylococcus aureus (45.8%). After surgical intervention, relapse was observed in 12.5% of the cases and recurrence in 20.8% of the cases. The relapse occurrence was significantly reduced by taurolidine irrigation (odds ratio [OR]: 0.16, 95% confidence interval [CI]: 0.02-0.98, P = 0.05) and the total resection of prosthetic material (OR: 0.07, 95% CI: 0.01-0.70, P = 0.02). Recurrence was significantly decreased by taurolidine irrigation (OR: 0.10, 95% CI: 0.02-0.56, P = 0.01) and increased dramatically in cases with relapse history (OR: 8.50, 95% CI: 1.69-42.76, P < 0.01). Finally, male sex (hazard ratio: 7.01, 95% CI: 1.19-41.40, P = 0.03) and AVG (hazard ratio: 4.49, 95% CI: 1.01-20.01, P = 0.05) were significantly associated with increased overall mortality in infected hemodialysis access.

CONCLUSIONS

Additional taurolidine irrigation after surgical resection significantly reduced the relapse and recurrence of infection in hemodialysis access. Taurolidine appears to be a safe and useful antiseptic for the control of hemodialysis access infection.

Femoral vein translocation for complex hemodialysis access

OBJECTIVE

Vascular access is difficult in patients without suitable arm veins and prior graft infections. The use of femoral vein translocation (FVT) to the upper extremity or contralateral lower extremity for hemodialysis access may be associated with low infection rates and high patency rates. FVT is used for patients without central venous occlusion who have failed prior access either owing to graft infection or repetitive graft thrombosis. The largest case series consists of 30 cases. The objective of this study is to determine the infection incidence, primary patency, primary-assisted patency, and secondary patency rates among FVTs.

METHODS

A retrospective chart review was performed on all patients who underwent FVT by a single vascular practice over a 10-year period (2013-2023). Study variables included length to last follow-up (months), prior access, prior graft infection, comorbid conditions, primary patency, primary-assisted patency, secondary patency, postoperative steal syndrome, postoperative graft infection, postoperative harvest site complication, and postoperative lower extremity compartment syndrome.

RESULTS

A total of 131 FVTs were performed from 2013 to 2023; 126 patients (47% male, 53% female; 76% Black, 24% White) with a mean age of 52 ± 14 years and a mean body mass index of 29 ± 8 had at least 1 month of follow-up and were included for analysis. The median follow-up was 46 months (interqurtile range, 19-72 months). The mean number of prior permanent accesses was 2.5 ± 1.4. Forty-eight percent of patients had prior graft infections. The primary, primary-assisted, and secondary patency rates were 66%, 93%, and 98%, respectively, at 6 months; 43%, 85%, and 96% at 12 months; 25%, 70%, and 92% at 24 months; 16%, 61%, and 88% at 36 months; and 14%, 56%, and 82% at 48 months. Postoperative steal syndrome and postoperative access infection requiring excision was observed 16% and 5% of patients, respectively. Harvest site complications requiring an additional procedure occurred in 19% of cases. Three patients developed lower extremity compartment syndrome postoperatively, requiring fasciotomy. Six patients developed chronic lower extremity edema after femoral vein harvest. The mean procedure time and hospital length of stay were 197 ± 40 minutes and 3.5 ± 2.8 days, respectively.

CONCLUSIONS

FVT is associated with low infection rates and high long-term patency rates. Significant postoperative complications include steal syndrome and harvest site complications. FVT remains a viable option for patients who have failed prior access owing to graft infection or repetitive graft thrombosis.

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.

Comparison between transposed arteriovenous fistulas and arteriovenous graft for the hemodialysis patients: A meta-analysis and systematic review

It is challenging for a surgeon to determine the appropriate vascular access for hemodialysis patients whose cephalic vein is usually inaccessible. The purpose of the study is to compare the complications and patency rates between transposed arteriovenous fistulas (tAVF) and arteriovenous graft (AVG) for the hemodialysis patients. Studies were recruited from PubMed, Cochrane library, EMBASE, the web of science databases, and reviewing reference lists of related studies from the inception dates to September 2, 2021. Statistical analyses were conducted using the statistical tool Review Manager version5.3 (Cochrane Collaboration, London, UK). I2 > 50% was defined as a high degree of heterogeneity, and then a random-effects model was used. Otherwise, the fixed-effects model was used. Odds ratio with its 95% confidence interval (95% CI) was used. Thirty-three trials (26 retrospective studies, four randomized controlled trials, two prospective trials, and one controlled-comparative study) with 6430 enrolled participants were identified in our analysis. The results showed that tAVF was accompanied with lower thrombosis rate (103/1184 (8.69%) vs 257/1367 (18.80%); I2 = 45%; 95% CI, 0.34 (0.26, 0.45)) and infection rate (43/2031 (2.12%) vs 180/2147 (8.38%); I2 = 0%; 95% CI, 0.20 (0.14, 0.30)) than arteriovenous graft. The significantly better primary patency rates, secondary patency rates, and primary assisted patency rates during follow-up were found in tAVF. However, the failure rate and the prevalence of hematoma were significantly lower in AVG group. No evidence showed the rate of overall mortality, steal syndrome, and aneurysm reduced in tAVF. Our results showed that tAVF is a promising vascular access technique for hemodialysis patients whose cephalic vein is inaccessible. Our data showed that tAVF has less thrombosis, infection risk, and better patency rates when compared with AVG. However, more attentions need to be paid to transposed arteriovenous fistulas maturation and hematoma.

ACR Appropriateness Criteria® Dialysis Fistula Malfunction

The creation and maintenance of a dialysis access is vital for the reduction of morbidity, mortality, and cost of treatment for end stage renal disease patients. One's longevity on dialysis is directly dependent upon the quality of dialysis. This quality hinges on the integrity and reliability of the access to the patient's vascular system. All methods of dialysis access will eventually result in dialysis dysfunction and failure. Arteriovenous access dysfunction includes 3 distinct classes of events, namely thrombotic flow-related complications or dysfunction, nonthrombotic flow-related complications or dysfunction, and infectious complications. The restoration of any form of arteriovenous access dysfunction may be supported by diagnostic imaging, clinical consultation, percutaneous interventional procedures, surgical management, or a combination of these methods. This document provides a rigorous evaluation of how variants of each form of dysfunction may be appraised and approached systematically. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Guidelines on vascular access for hemodialysis from the Brazilian Society of Angiology and Vascular Surgery

Chronic kidney disease is a worldwide public health problem, and end-stage renal disease requires dialysis. Most patients requiring renal replacement therapy have to undergo hemodialysis. Therefore, vascular access is extremely important for the dialysis population, directly affecting the quality of life and the morbidity and mortality of this patient population. Since making, managing and salvaging of vascular accesses falls within the purview of the vascular surgeon, developing guideline to help specialists better manage vascular accesses for hemodialysis if of great importance. Thus, the objective of this guideline is to present a set of recommendations to guide decisions involved in the referral, evaluation, choice, surveillance and management of complications of vascular accesses for hemodialysis.

Meta-analysis of total versus partial graft excision: Which is the better choice to manage arteriovenous dialysis graft infection?

BACKGROUND

Arteriovenous graft infection (AVGI) is a major cause of hemodialysis access failure. Delayed diagnosis and inappropriate treatment may lead to increased morbidity (3-35%) and mortality up to 12%.

OBJECTIVES

Compare the postoperative outcomes of total graft excision (TGE) and partial graft excision (PGE) in the treatment of AVGI.

DESIGNS

Systematic review and meta-analysis METHODS: The dataset was defined by searching PubMed, EMBASE, Google Scholar, and the Cochrane database for articles outlining the terms arteriovenous graft infection, infected dialysis graft, TGE and PGE published between 1995-2020. The data analysis evaluated the outcomes of TGE and PGE in the management of AVGI. The meta-analysis was performed using Review Manager Software version 5.4.1.

MAIN OUTCOME MEASURES

30-day mortality, recurrent infection, and reoperation rate.

SAMPLE SIZE

Eight studies, including 555 AVGI, and 528 patients.

RESULTS

PGE showed a significant increase in recurrent graft infection rate (OR=0.23,95% CI=0.13-0.41, P<.00001) and re-operation rate for control of infection (OR=0.14,95% CI=0.03-0.58, P<.007). However, the 30-day mortality rate did not differ significantly between the groups (OR=0.92,95% CI=0.39-2.17, P=.85).

CONCLUSIONS

TGE remains a safe and effective surgical method for the management of AVGI. PGE is associated with a higher risk of graft infection and need for re-operation. As a result, PGE should only be considered in carefully selected patients.

LIMITATION

Risk of bias due to the differences in patient characteristics.

CONFLICT OF INTEREST

None.

Bioengineering Human Tissues and the Future of Vascular Replacement

Cardiovascular defects, injuries, and degenerative diseases often require surgical intervention and the use of implantable replacement material and conduits. Traditional vascular grafts made of synthetic polymers, animal and cadaveric tissues, or autologous vasculature have been utilized for almost a century with well-characterized outcomes, leaving areas of unmet need for the patients in terms of durability and long-term patency, susceptibility to infection, immunogenicity associated with the risk of rejection, and inflammation and mechanical failure. Research to address these limitations is exploring avenues as diverse as gene therapy, cell therapy, cell reprogramming, and bioengineering of human tissue and replacement organs. Tissue-engineered vascular conduits, either with viable autologous cells or decellularized, are the forefront of technology in cardiovascular reconstruction and offer many benefits over traditional graft materials, particularly in the potential for the implanted material to be adopted and remodeled into host tissue and thus offer safer, more durable performance. This review discusses the key advances and future directions in the field of surgical vascular repair, replacement, and reconstruction, with a focus on the challenges and expected benefits of bioengineering human tissues and blood vessels.

Five Year Outcome in Patients with End Stage Renal Disease Who Received a Bioengineered Human Acellular Vessel for Dialysis Access

Objective

Patients with end stage renal failure who require haemodialysis suffer morbidity and mortality due to vascular access. Bioengineered human acellular vessels (HAVs) may provide a haemodialysis access option with fewer complications than other grafts. In a prospective phase II trial from 2012 to 2014 (NCT01744418), HAVs were implanted into 40 haemodialysis patients at three sites in Poland. The trial protocol for this “first in man” use of the HAV contemplated only two years of follow up, and the trial results were initially reported in 2016. In light of the retained HAV function seen in many of the patients at the two year time point, follow up for patients who were still alive was extended to a total of 10 years. This interim follow up report, at the long term time point of five years, assessed patient and conduit status in those who continued routine dialysis with the HAV.

Methods

HAVs are bioengineered by culturing human vascular smooth muscle cells on a biodegradable polymer matrix. In this study, patients with patent HAV implants at 24 months were followed every three months, starting at month 27 through to month 60, or at least five years post-implantation. This report contains the follow up functional and histological data on 29 of the original 40 patients who demonstrated HAV function at the 24 month time point.

Results

Eleven patients completed at month 60. One patient maintained primary patency, and 10 maintained secondary patency. Secondary patency was estimated at 58.2% (95% confidence interval 39.2–73.1) at five years, after censoring for deaths (n = 8) and withdrawals (n = 1). No HAV conduit infections were reported during the follow up period.

Conclusion

This phase II long term follow up shows that the human acellular vessel (HAV) may provide durable and functional haemodialysis access for patients with end stage renal disease.

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This long term follow up assessed conduit status in patients who continued dialysis with an HAV.

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At month 60, one patient maintained primary patency, and 10 maintained secondary patency.

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Secondary patency was estimated at 58.2% at five years, after censoring for deaths and withdrawals.

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No HAV conduit infections were reported during follow up.

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The HAV provides long term, durable and functional haemodialysis access for patients with ESRD.

Vascular Smooth Muscle Cells Mechanosensitive Regulators and Vascular Remodeling

Blood vessels are subjected to mechanical loads of pressure and flow, inducing smooth muscle circumferential and endothelial shear stresses. The perception and response of vascular tissue and living cells to these stresses and the microenvironment they are exposed to are critical to their function and survival. These mechanical stimuli not only cause morphological changes in cells and vessel walls but also can interfere with biochemical homeostasis, leading to vascular remodeling and dysfunction. However, the mechanisms underlying how these stimuli affect tissue and cellular function, including mechanical stimulation-induced biochemical signaling and mechanical transduction that relies on cytoskeletal integrity, are unclear. This review focuses on signaling pathways that regulate multiple biochemical processes in vascular mesangial smooth muscle cells in response to circumferential stress and are involved in mechanosensitive regulatory molecules in response to mechanotransduction, including ion channels, membrane receptors, integrins, cytoskeletal proteins, nuclear structures, and cascades. Mechanoactivation of these signaling pathways is closely associated with vascular remodeling in physiological or pathophysiological states.

Management of Vascular Infections in Low- and Middle-Income Countries

Background: Vascular infections are rare and challenging conditions with significant deaths and morbidity. Their management necessitates a multi-disciplinary approach and substantial human and financial resources. The management selected may be influenced by the available resources in low- and middle-income countries (LMICs), where such resources may be variable. Methods: We reviewed the published literature and reviewed the management options for various vascular infections with a focus on carotid, aortic, infrainguinal, and dialysis access infections. Results: Recommendations related to prevention and treatment will be offered from the perspective of LMICs. The general principles for prevention are in compliance with established surgical site infection guidelines and minimize the use of prosthetic material. Early detection and intervention by removing all infected prosthetic material, debridement, drainage, and coverage of the infected field with vascularized tissue are essential steps in the management of the infection. Revascularization using an extra-anatomic or in situ approach is individualized based on the resources and expertise available. Conclusions: The prevention and management of vascular infections in LMICs are effective by adhering to time-proven principles even with limited resources.

Arteriovenous Grafts' Types of Indications and Their Infection Rate

BACKGROUND

Arteriovenous graft infection is a well-known and frequent complication. The objective of this study was to compare infection rates of primary and secondary indicated arteriovenous grafts (AVGs).

SUBJECTS AND METHODS

Retrospectively, we evaluated the indications for AVGs created at our institution which became infected. One hundred forty AVGs were evaluated. Of these AVGs, 33 (23.6%) were primary and 107 (76.4%) secondary indicated.

RESULTS

Infection of a primary AVG was detected in 5 patients (15.2 %). Infection of a secondary AVG was detected in 30 patients (28.0%). Primary and secondary patency were significantly lower in patients with infected AVG (P = 0.006; P = 0.0001). The effect of diabetes mellitus and age on development of infection was not confirmed.

CONCLUSIONS

Indications for AVG creation clearly influence the future risk of infection. If the indication to use the AVG is to correct a complicated arteriovenous fistula, the risk of infection is 2 times higher.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for hemodialysis vascular access since 1996. Since the last update in 2006, there has been a great accumulation of new evidence and sophistication in the guidelines process. The 2019 update to the KDOQI Clinical Practice Guideline for Vascular Access is a comprehensive document intended to assist multidisciplinary practitioners care for chronic kidney disease patients and their vascular access. New topics include the end-stage kidney disease "Life-Plan" and related concepts, guidance on vascular access choice, new targets for arteriovenous access (fistulas and grafts) and central venous catheters, management of specific complications, and renewed approaches to some older topics. Appraisal of the quality of the evidence was independently conducted by using a Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and interpretation and application followed the GRADE Evidence to Decision frameworks. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Tissue-Engineered Vascular Grafts with Advanced Mechanical Strength from Human iPSCs

Vascular smooth muscle cells (VSMCs) can be derived in large numbers from human induced pluripotent stem cells (hiPSCs) for producing tissue-engineered vascular grafts (TEVGs). However, hiPSC-derived TEVGs are hampered by low mechanical strength and significant radial dilation after implantation. Here, we report generation of hiPSC-derived TEVGs with mechanical strength comparable to native vessels used in arterial bypass grafts by utilizing biodegradable scaffolds, incremental pulsatile stretching, and optimal culture conditions. Following implantation into a rat aortic model, hiPSC-derived TEVGs show excellent patency without luminal dilation and effectively maintain mechanical and contractile function. This study provides a foundation for future production of non-immunogenic, cellularized hiPSC-derived TEVGs composed of allogenic vascular cells, potentially serving needs to a considerable number of patients whose dysfunctional vascular cells preclude TEVG generation via other methods.

Risk assessment of significant upper extremity arteriovenous graft infection in the Vascular Quality Initiative

OBJECTIVE

Infectious complications of arteriovenous grafts (AVGs) are a major source of morbidity. Our aim was to characterize contemporary risk factors for upper extremity AVG infection.

METHODS

The Vascular Quality Initiative (2011-2018) was queried for all patients undergoing upper extremity AVG creation. AVG infection was classified as an infection treated with antibiotics, incision and drainage, or graft removal. Multivariable analyses were used to evaluate risk factors for short- and long-term AVG infection.

RESULTS

Of 1758 upper extremity AVGs, 49 (2.8%) developed significant infection within 3 months, resulting in incision and drainage in 24% and graft removal in 76% of cases. None were managed with antibiotics alone in the study sample. Patients with significant AVG infection were more likely to be white, to be insured, to have a history of coronary artery bypass graft and intravenous (IV) drug use, to be undergoing a concomitant vascular procedure, and to be discharged on an anticoagulant. In multivariable analysis, significant AVG infection within 3 months was associated with IV drug use history (odds ratio [OR], 5; 95% confidence interval [CI], 1.75-14.3; P = .003), discharge to a health care facility (OR, 2.66; 95% CI, 1.07-6.63; P = .035), discharge on an anticoagulant (OR, 2.31; 95% CI, 1.13-4.72; P = .021), white race (OR, 2.3; 95% CI, 1.21-4.34; P = .011), and female sex (OR, 2.02; 95% CI, 1.06-3.85; P = .033). Kaplan-Meier analysis showed that freedom from graft site infection at 1 year was 96.4%. Longer term graft infection at 1 year was independently associated with IV drug use history (hazard ratio [HR], 1.98; 95% CI, 1.06-3.68; P = .032), initial discharge to a health care facility (HR, 1.88; 95% CI, 1.19-2.97; P = .007), and white race (HR, 1.64; 95% CI, 1.23-2.19; P = .001).

CONCLUSIONS

Although significant AVG infection was uncommon in the Vascular Quality Initiative, the majority were treated with graft removal. In select high-risk patients, extra care should be taken and alternative forms of arteriovenous access may be considered.

18F-FDG PET/CT and 99mTc-HMPAO-WBC SPECT/CT effectively contribute to early diagnosis of infection of arteriovenous graft for hemodialysis

OBJECTIVE

An arteriovenous graft (AVG) is indicated in hemodialysis patients with failed arteriovenous access. Early treatment of AVG infection is important because an advanced prosthetic infection leads to the removal of the prosthesis. The aim of this study was to evaluate the benefits of ¹⁸F-FDG PET/CT and ^99mTc-HMPAO-WBC SPECT/CT in early detection of AVG infections.

SUBJECTS AND METHODS

Fifty-one AVGs were evaluated. ¹⁸F-FDG PET/CT and ^99mTc-HMPAO-WBC SPECT/CT studies were performed at intervals of 10, 20-30, and 40-50 weeks after AVG insertion. Agreement between the imaging methods and reference parameters (i.e. clinical presentation, C-reactive protein and microbiological findings on the hemodialysis cannula extracted after hemodialysis from AVG) was evaluated.

RESULTS

The study results showed that focal accumulation of the radiopharmaceuticals can be considered a sign of AVG infection. At 10 weeks after AVG implantation, the focal ¹⁸F-FDG findings showed the best agreement with the reference parameters (agreement coefficients AC1 - clinical status: 0.693, CRP: 0.605, cannula microbiology: 0.518, respectively). At 20 to 30 weeks after AVG implantation, the diagnostic value of focal ^99mTc-HMPAO-WBC accumulation increased (AC1 coefficients: 0.658, 0.658, 0.408) and was similar to that of focal ¹⁸F-FDG uptake (AC1s: 0.656, 0.570, 0.409). Between 40 and 50 weeks since AVG implantation, the diagnostic significance of focal ^99mTc-HMPAO-WBC accumulation (AC1 coefficients: 0.771, 0.811, 0.611) slightly exceeded the diagnostic value of focal ¹⁸F-FDG accumulation (AC1 coefficients: 0.524, 0.456, 0.569).

CONCLUSION

¹⁸F-FDG PET/CT and ^99mTc-HMPAO-WBC SPECT/CT can both serve as important tools contributing to early diagnosis of AVG infection.

Spanish Clinical Guidelines on Vascular Access for Haemodialysis

Vascular access for haemodialysis is key in renal patients both due to its associated morbidity and mortality and due to its impact on quality of life. The process, from the creation and maintenance of vascular access to the treatment of its complications, represents a challenge when it comes to decision-making, due to the complexity of the existing disease and the diversity of the specialities involved. With a view to finding a common approach, the Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology [S.E.N.], vascular surgery [SEACV], vascular and interventional radiology [SERAM-SERVEI], infectious diseases [SEIMC] and nephrology nursing [SEDEN]), along with the methodological support of the Cochrane Center, has updated the Guidelines on Vascular Access for Haemodialysis, published in 2005. These guidelines maintain a similar structure, in that they review the evidence without compromising the educational aspects. However, on one hand, they provide an update to methodology development following the guidelines of the GRADE system in order to translate this systematic review of evidence into recommendations that facilitate decision-making in routine clinical practice, and, on the other hand, the guidelines establish quality indicators which make it possible to monitor the quality of healthcare.

Catheter-related complications and survival among incident hemodialysis patients in Singapore

Introduction:

Hemodialysis is the main modality of renal replacement therapy in Singapore. However, a majority of the patients in Singapore are initiated on hemodialysis via a catheter. This study examines the complication rates and factors predicting catheter-related bloodstream infections and mortality rates in patients who were initiated on hemodialysis at our institution.

Methods:

This is a single-center retrospective analysis of incident hemodialysis patients who were initiated on renal replacement therapy between 1 January 2010 and 31 December 2012. Catheter-related bloodstream infection risk factors, organisms, and associated mortality were analyzed.

Results:

The catheter-related bloodstream infection and exit site infection incidence rates were 0.75 and 0.50 per 1000 catheter days, respectively. The mean duration to first catheter-related bloodstream infection episode was 182.47 ± 144.04 catheter days. Prolonged catheter duration was found to be a risk factor for catheter-related bloodstream infection. Compared to patients initiated on dialysis via arteriovenous fistula, initiation of dialysis via catheter is strongly associated with increased mortality (6.0% vs 14.5%; p = 0.02). In particular, the presence of diabetes mellitus and development of catheter-related bloodstream infection was associated with increased mortality ( p = 0.04 and 0.05, respectively). In addition, patients who began hemodialysis before being seen by a nephrologist were associated with decreased mortality (3.4% vs 13.0%; p = 0.03).

Conclusion:

In conclusion, prolonged duration of catheter insertion is found to be a risk factor for catheter-related bloodstream infection in hemodialysis patients, and its development is associated with increased mortality. Early referral to a nephrologist and creation of arteriovenous fistula in pre-end-stage renal disease patients are pivotal in improving the outcomes of patients.

Vascular Tissue Engineering: Progress, Challenges, and Clinical Promise

Although the clinical demand for bioengineered blood vessels continues to rise, current options for vascular conduits remain limited. The synergistic combination of emerging advances in tissue fabrication and stem cell engineering promises new strategies for engineering autologous blood vessels that recapitulate not only the mechanical properties of native vessels but also their biological function. Here we explore recent bioengineering advances in creating functional blood macro and microvessels, particularly featuring stem cells as a seed source. We also highlight progress in integrating engineered vascular tissues with the host after implantation as well as the exciting pre-clinical and clinical applications of this technology.

How to treat arteriovenous graft infection: total versus partial graft excision

Introduction:

Arteriovenous graft (AVG) infection can result in life-threatening sepsis and loss of vascular access. A retrospective study was performed to establish an appropriate treatment strategy for AVG infection.

Methods:

A total of 50 cases of AVG infection were treated between January 2005 and June 2016. The surgical methods used were total graft excision (TGE) (n = 34), or partial graft excision (PGE) with interposition graft (n = 16).

Results:

Infection was noted at a puncture site (n = 22), a prior incision for surgery or endovascular therapy (n = 20), and abandoned (currently unused) grafts (n = 5). Infection occurred within 1 month after AVG creation (n = 1), or any intervention (n = 14), and more than 1 month after creation or intervention (n = 35). Simultaneous remote infection was identified in 7 patients, 2 of whom underwent an operation for infective endocarditis and spondylitis. After PGE, 5 patients (5/16, 31.2%) having recurrent infection were treated with further graft excision; however, no patient showed life-threatening complications. After TGE, a central venous catheter (CVC) was inserted and used for a median period of 90 days. Among 34 patients who underwent TGE, new vascular access was created in 18 patients at a median period of 2 months later, and 12 patients continued to use a CVC until last follow-up or death.

Conclusions:

PGE could be a treatment option for AVG infection to achieve both infection eradication and vascular access preservation in selected patients. Because of a higher risk of recurrent infection, sufficient surgical removal and careful postoperative management are warranted.

Susceptibility of ePTFE vascular grafts and bioengineered human acellular vessels to infection

BACKGROUND

Synthetic expanded polytetrafluorethylene (ePTFE) grafts are routinely used for vascular repair and reconstruction but prone to sustained bacterial infections. Investigational bioengineered human acellular vessels (HAVs) have shown clinical success and may confer lower susceptibility to infection. Here we directly compared the susceptibility of ePTFE grafts and HAV to bacterial contamination in a preclinical model of infection.

MATERIALS AND METHODS

Sections (1 cm²) of ePTFE (n = 42) or HAV (n = 42) were inserted within bilateral subcutaneous pockets on the dorsum of rats and inoculated with Staphylococcus aureus (10⁷ CFU/0.25 mL) or Escherichia coli (10⁸ CFU/0.25 mL) before wound closure. Two weeks later, the implant sites were scored for abscess formation and explanted materials were halved for quantification of microbial recovery and histological analyses.

RESULTS

The ePTFE implants had significantly higher abscess formation scores for both S. aureus and E. coli inoculations compared to that of HAV. In addition, significantly more bacteria were recovered from explanted ePTFE compared to HAV. Gram staining of explanted tissue sections revealed interstitial bacterial contamination within ePTFE, whereas no bacteria were identified in HAV tissue sections. Numerous CD45⁺ leukocytes, predominantly neutrophils, were found surrounding the ePTFE implants but minimal intact neutrophils were observed within the ePTFE matrix. The host cells surrounding and infiltrating the HAV explants were primarily nonleukocytes (CD45^-).

CONCLUSIONS

In an established animal model of infection, HAV was significantly less susceptible to bacterial colonization and abscess formation than ePTFE. The preclinical findings presented in this manuscript, combined with previously published clinical observations, suggest that bioengineered HAV may exhibit low rates of infection.

Bovine carotid artery xenografts for hemodialysis access

OBJECTIVE

Bovine carotid artery (BCA) grafts have been described as a possibly superior alternative to expanded polytetrafluoroethylene hemoaccess grafts. However, published experience remains limited, and patency rates for nonautogenous arteriovenous grafts remain unsatisfactory. We report herein the largest published experience with the current generation of BCA grafts for dialysis access and analyze subgroups to determine whether obesity, gender, or prior access surgery influences patency.

METHODS

We retrospectively reviewed 134 BCA grafts (Artegraft, North Brunswick, NJ) implanted for hemodialysis access in the upper extremities of 126 patients between January 2012 and May 2015. Patients had a mean of 1.8 prior access operations. Primary, primary assisted, and secondary patency rates were calculated using the Kaplan-Meier method, and longitudinal infection risk was tabulated. Patency differences were calculated using the log-rank method.

RESULTS

For the entire group, 1-year primary patency was 32%, primary assisted patency was 49%, and secondary patency was 78%. Ten of 133 grafts (7%) developed infection requiring graft excision between 1 and 9 months after implantation. There was no statistical difference between men and women in primary or secondary patency (P = .88, P = .69). There was no difference in primary patency or secondary patency for patients with body mass index >30 or <30 (P = .85, P = .54). Patients who had a BCA graft as their first access attempt had a higher primary and primary assisted patency than that of patients who had the graft placed after prior access failure (P = .039, P = .024).

CONCLUSIONS

This represents the largest published series of BCA grafts for arteriovenous grafts in the modern era. The primary patency of BCA grafts in this series was lower than that reported in a smaller randomized study. However, primary assisted and secondary patency were similar. Infection rates in this series appear to be somewhat lower than polytetrafluoroethylene infection rates reported in the literature. BCA grafts are a satisfactory alternative to expanded polytetrafluoroethylene for hemodialysis access, but larger controlled studies are needed to determine whether superior primary patency previously reported is a reproducible finding.

Endovascular Stent Graft Repair is an Effective and Safe Alternative Therapy for Arteriovenous Graft Pseudoaneurysms

OBJECTIVE/BACKGROUND

Pseudoaneurysm formation occurs in 2-10% of hemodialysis arteriovenous grafts (AVGs). Surgical repair often requires pseudoaneurysm resection, interposition graft placement, and insertion of a catheter as a bridge. Endovascular stent graft repair is a controversial alternative therapy. This study was performed to examine the effectiveness and mid-term outcomes of stent graft repair for AVG pseudoaneurysms.

METHODS

All patients who had undergone stent graft repair for AVG pseudoaneurysms between December 2012 and July 2015 were identified from hospital medical records for retrospective analysis. Outcome measures were technical success, early and late complications, and primary and secondary patency rates.

RESULTS

A total of 37 stent graft repairs of AVG pseudoaneurysms were performed in 35 patients (42.9% men; mean age 66.9 years). The mean time from AVG creation to pseudoaneurysm repair was 69 months. The indications of treatment (as per the institutional policy) were large pseudoaneurysm (56.7%), impending rupture (27.1%), and bleeding (16.2%). Mean pseudoaneurysm diameter was 23.0 mm. The most common diameter and length of stent graft used were 7 mm (67.6%) and 50 mm (48.6%), respectively. Technical success was 100%. Only one early complication occurred after stent graft repair, which was due to recurrence of the pseudoaneurysm as a result of a short landing zone. Late complications included infection (17.1%) and thrombosis (37.1%). The 1, 6, and 12 month primary patency rates were 89.2%, 55.5%, and 22.0%, respectively. The 1, 6, and 12 month secondary patency rates were 100%, 88.6%, and 78.6%, respectively. The median follow up was 12.3 months.

CONCLUSIONS

The study demonstrates that endovascular stent graft repair is an effective and safe alternative therapy for AVG pseudoaneurysms. However, the rate of thrombosis and infection was high and needs to be balanced against open surgery in future studies.

Bioengineered human acellular vessels for dialysis access in patients with end-stage renal disease: two phase 2 single-arm trials

BACKGROUND

For patients with end-stage renal disease who are not candidates for fistula, dialysis access grafts are the best option for chronic haemodialysis. However, polytetrafluoroethylene arteriovenous grafts are prone to thrombosis, infection, and intimal hyperplasia at the venous anastomosis. We developed and tested a bioengineered human acellular vessel as a potential solution to these limitations in dialysis access.

METHODS

We did two single-arm phase 2 trials at six centres in the USA and Poland. We enrolled adults with end-stage renal disease. A novel bioengineered human acellular vessel was implanted into the arms of patients for haemodialysis access. Primary endpoints were safety (freedom from immune response or infection, aneurysm, or mechanical failure, and incidence of adverse events), and efficacy as assessed by primary, primary assisted, and secondary patencies at 6 months. All patients were followed up for at least 1 year, or had a censoring event. These trials are registered with ClinicalTrials.gov, NCT01744418 and NCT01840956.

FINDINGS

Human acellular vessels were implanted into 60 patients. Mean follow-up was 16 months (SD 7·6). One vessel became infected during 82 patient-years of follow-up. The vessels had no dilatation and rarely had post-cannulation bleeding. At 6 months, 63% (95% CI 47-72) of patients had primary patency, 73% (57-81) had primary assisted patency, and 97% (85-98) had secondary patency, with most loss of primary patency because of thrombosis. At 12 months, 28% (17-40) had primary patency, 38% (26-51) had primary assisted patency, and 89% (74-93) had secondary patency.

INTERPRETATION

Bioengineered human acellular vessels seem to provide safe and functional haemodialysis access, and warrant further study in randomised controlled trials.

FUNDING

Humacyte and US National Institutes of Health.

Operative and perioperative management of infected arteriovenous grafts

Vascular graft infections are a particularly troublesome complication for dialysis patients, many of whom are in an already immunocompromised state. The objective of this review is to detail the risk factors, etiology, diagnosis, perioperative and operative management of vascular graft infections.

THE INFLUENCE OF USING THE NEEDLE ADAPTER TO REDUCE THE BIOMECHANICAL RISK FACTORS WITHIN HEMODIALYSIS ARTERIOVENOUS GRAFTS

Hemodialysis vascular access failure is related to increased morbidity and mortality in hemodialysis patients, representing a challenging clinical problem which results in a high percentage of hospital entrance and an important economic burden on government's disbursement. In this paper, the feasibility of using the needle adapter to reduce the biomechanical risk factors within arteriovenous grafts is considered. The three-dimensional (3D) tapered 6 to 8 mm loop graft in the presence of venous and arterial needles with and without adapter was numerically simulated. Navier–Stokes equations for incompressible Newtonian fluid are the governing equation of this problem. k – ω two equations turbulence modeling were applied to capture flow features of low Reynolds turbulent flow regions in this simulation. The physiological velocity waveform was used as an arterial inlet boundary condition. The venose outlet boundary condition was a time dependent physiological pressure waveform. The results for the dialysis without the adapter demonstrated that the graft wall experiences increased hemodynamic stresses as a result of the hitting needle jet flow. The dialysis with the adapter demonstrated that the venous anastomosis experiences lower biomechanical risk factors in comparison to the dialysis without the adapter and it reduced the vascular access failure. Using adapter caused less damage to endothelial cells during hemodialysis.

Lower limb access

Lower limb vascular access is used as an access site in patients in whom all upper limb possibilities for arteriovenous access creation are exhausted or with bilateral upper limb central vein occlusions. Autologous arteriovenous fistulae (AVF) using the greater saphenous vein have disappointing results apart from the isolated success. Autologous AVF using the femoral vein transposition have good results both in terms of long-term patency and are associated with a 10-fold reduction in infection risk compared with arteriovenous grafts (AVGs). However, a femoral vein transposition is a major undertaking and is associated with an increased risk of ischaemic complications. It is not a good option for patients with established peripheral arterial disease, but may be a good alternative for the younger patient with a high infection risk. The type of lower-extremity vascular access should be carefully tailored to the individual patient.

Arm composite autogenous vascular access using the great saphenous vein and the femoral vein: results from a single-centre study

OBJECTIVES

The objective is to report our results with the arm composite autogenous vascular access (ACAVA) using the great saphenous vein (GSV) and the femoral vein (FV) in tertiary vascular access surgery.

DESIGN

Retrospective single-centre study. Prospectively collected clinical database.

METHODS

Between August 2009 and March 2011, 17 patients with no suitable upper extremity vein, repeated prosthetic access failure and/or infection underwent the construction of an ACAVA. Outcome measures included the graft patency and complication rates.

RESULTS

The median follow-up was 25 months (5-32). Thirty-day morbidity affected 10 patients (59%): four wound-healing issues, three lower limb swelling, two early thromboses and one upper limb haematoma. No postoperative death occurred. At 3 months, the primary patency rate was 88% ± 8%. At 6 months, the assisted-primary patency rate was 82.4% ± 9.2%. At 12 months, the secondary patency rate was 81.6% ± 9.6%. Twenty-four secondary interventions were performed. Steal syndrome occurred in one patient following a secondary procedure. Swelling of the lower limb remained in two patients at the end of their follow-up. Three ACAVAs developed irreversible occlusion leading to loss of access.

CONCLUSION

With a high rate of postoperative morbidity and re-intervention, the ACAVA is a useful additional technique that should be restricted to difficult cases with limited vascular access options.