Vascular access for hemodialysis

Personalized decision-making for vascular access creation in hemodialysis

Selecting the appropriate kidney replacement therapy (KRT) is crucial in order to secure optimal care for chronic kidney disease (CKD) patients with end-stage renal disease (ESRD). Next to renal transplantation, the choice of dialysis modality directly affects patient well-being, treatment effectiveness, and long-term outcomes. Therefore, clinical decision-making must take into account a range of factors to tailor decisions to each patient's unique needs. Previously, when the dialysis population was less diverse and resources more limited, straight-forward algorithms could be effectively implemented both for selection of KRT as well as for hemodialysis (HD) vascular access (VA). Recently, the growing ESRD population with more elderly being considered for dialysis care together with improved treatment opportunities have resulted in more challenging decision-making where on-size-fits-all strategies are being replaced by more tailored and personalized strategies aimed to ensure "the right dialysis access - to the right patient - at the right time - for the right reason." In this review, recent trends enforcing a more personalized approach in the selection of VA for HD are summarized and discussed, where these concerns have become especially relevant.

Comparison of the use of standard heparin and 0.9% saline as lock solution in hemodialysis catheter: Importance of closure technique

BACKGROUND

Bleeding and thrombotic occlusion are complications of Central venous catheters. When selecting a catheter lock solution, factors such as bleeding, thrombotic occlusion, infection, and cost-effectiveness must be considered.

METHODS

The study included 35 patients who used heparin as a locking solution and 35 patients who used 0.9% saline, retrospectively. In our center, after injecting the solution equal to the catheter lumen volume from the syringe, approximately 1 cc of locking solution is left in the syringe, the catheter is locked and the syringe is removed from the catheter after locking. Intergroup complications were observed.

RESULTS

No significant difference was observed between the groups concerning the catheter insertion site (p = 0.143 and 0.143). Additionally, no significant differences were found between the groups in terms of thrombosis and bleeding complications (p = 0.314 and 0.239, respectively).

CONCLUSION

Our study concluded that heparin locking is not superior to normal saline locking in terms of catheter dysfunction. We aimed to emphasize that the technique of catheter locking is more important than the type of lock solution used.

Identification of key potential risk areas and key potential failure modes in hemodialysis rooms by the FMEA method following routine prevention and control of the COVID-19 pandemic

Hemodialysis is an important part of nosocomial infection prevention and control (IPC). This study aimed to identify the key potential risk areas and failure modes in hemodialysis rooms in hospitals and put forward a series of improvement measures to prevent and control the spread of the coronavirus disease 2019 (COVID-19). Hemodialysis patients are highly susceptible to COVID-19 and usually have a high incidence of severe illness and mortality after infection with COVID-19. Therefore, IPC in hemodialysis patients is of crucial strategic significance. Based on 30 domain experts' interviews and careful analysis of prevention and control documents, we constructed a comprehensive failure system for a model that identifies the potential risks for nosocomial COVID-19 infection in the hemodialysis room. Subsequently, a thorough risk assessment of the potential failure factors identified in our model was conducted. The failure key factors corresponding to the human element in medical waste (garbage) disposal (C2) are verified to be the highest risk factors. They are as follows: The cleaning staff did not dispose of different types of medical waste (garbage) (C21), did not wear masks according to the regulations (C22), and lacked knowledge and norms of nosocomial IPC (C23). This study provides valuable insights for hospital decision-makers on the potential failure factors related to COVID-19 infections in hemodialysis rooms. By working with hospital infection specialists, the suggested improvement measures can help reduce the risk of virus exposure among hospital medical staff, patients, and cleaning staff.

The application of blood flow sound contrastive learning to predict arteriovenous graft stenosis of patients with hemodialysis

End-stage kidney disease (ESKD) presents a significant public health challenge, with hemodialysis (HD) remaining one of the most prevalent kidney replacement therapies. Ensuring the longevity and functionality of arteriovenous accesses is challenging for HD patients. Blood flow sound, which contains valuable information, has often been neglected in the past. However, machine learning offers a new approach, leveraging data non-invasively and learning autonomously to match the experience of healthcare professionas. This study aimed to devise a model for detecting arteriovenous grafts (AVGs) stenosis. A smartphone stethoscope was used to record the sound of AVG blood flow at the arterial and venous sides, with each recording lasting one minute. The sound recordings were transformed into mel spectrograms, and a 14-layer convolutional neural network (CNN) was employed to detect stenosis. The CNN comprised six convolution blocks with 3x3 kernel mapping, batch normalization, and rectified linear unit activation function. We applied contrastive learning to train the pre-training audio neural networks model with unlabeled data through self-supervised learning, followed by fine-tuning. In total, 27,406 dialysis session blood flow sounds were documented, including 180 stenosis blood flow sounds. Our proposed framework demonstrated a significant improvement (p<0.05) over training from scratch and a popular pre-trained audio neural networks (PANNs) model, achieving an accuracy of 0.9279, precision of 0.8462, and recall of 0.8077, compared to previous values of 0.8649, 0.7391, and 0.6538. This study illustrates how contrastive learning with unlabeled blood flow sound data can enhance convolutional neural networks for detecting AVG stenosis in HD patients.

Malnutrition: A risk factor for vascular access problems

BACKGROUND

Vascular access problems are leading causes of morbidity, hospitalization, and impaired quality of life in chronic hemodialysis patients. Native arteriovenous fistula is the gold standard of vascular access. Geriatric nutritional risk index (GNRI), has recently been shown to be an easy and objective instrument for assessing nutritional status in these patient groups. Considering the association between arteria-venous fistula patency and inflammation, as well as the fact that inflammation is a component of malnutrition, the objective of this study was to determine the relation of malnutrition identified by GNRI with fistula patency.

METHODS

This is a single-center, retrospective, observational study. Hemodialysis patients with AVF were included in the research. Preoperative and postoperative GNRI values were computed and laboratory data were recorded. The patients were analyzed in two groups as the ones without thrombosis history (Group 1) and with thrombosis history (Group 2). According to GNRI, patients were investigated in four groups: G0 (non-risk group, >98), G1 (low risk, 92-98), G2 (moderate risk, 82-91), and G3 (high risk, 82).

RESULTS

Of the 331 patients, 60.1% (199) were male and the average age was 55 ± 15 years. Preoperative GNRI levels were significantly higher in group 1. In correlation analysis, patency time was positively correlated with preoperative GNRI values. Among the preoperative GNRI groups, the G3 group had a patency duration of 6 months (4.9-7.04), whereas the G0 group had a patency length of 37.59 (35.5-39.65) months. By linear regression analysis, preoperative GNRI and postoperative albumin level were determined to be the significant indicators of patency time.

CONCLUSION

GNRI a new tool for detecting malnutrition was strongly associated with fistula patency in hemodialysis patients. Detection of malnutrition before fistula operation may be helpful for the future follow up of the patients in terms of fistula patency.

Outcomes of upper arm axillary artery and brachial artery arteriovenous grafts

BACKGROUND

We compared the outcomes of upper arm arteriovenous grafts (AVGs) in a large, prospectively collected data set to determine if there are clinically significant differences in axillary artery-based and brachial artery-based AVGs.

METHODS

Patients who received upper arm AVGs within the Society of Vascular Surgery Vascular Quality Initiative (VQI) dataset were identified. The primary outcome measures were primary and secondary patency loss at 12-month follow-up. Other outcomes included were wound infection, steal syndrome, and arm swelling at 6-month follow-up. The log-rank test was used to evaluate patency loss using Kaplan-Meier analysis, and Cox proportional hazards models were used to examine adjusted association between inflow artery (brachial artery vs axillary artery) and outcomes, adjusting for configuration (straight vs looped).

RESULTS

Among 3637 upper extremity AVGs in the VQI (2010-2017), there were 510 upper arm brachial artery AVGs and 394 upper arm axillary artery AVGs. Patients with axillary artery AVGs were more likely to be female (72% vs 56%, p < 0.001) and underwent general anesthesia (61% vs 57%, p < 0.05). In univariable analysis, the 12-month primary patency (54% vs 63%, p = 0.03) and secondary patency (81% vs 89%, p = 0.007) were lower for axillary artery AVGs than upper arm brachial artery AVGs. In multivariable analysis, although wound infection and arm swelling were similar at 6-month follow up, axillary artery AVGs were more likely to have steal syndrome (adjusted Hazard Ratio (aHR) = 2.6, 95% Confidence Interval (CI) 1.2,5.6, p = 0.017). In addition, axillary artery AVGs were associated with higher rates of 12-month primary patency loss (aHR = 1.6, 95% CI 1.2-2.2, p = 0.002) and 12-month secondary patency loss (aHR = 2.0, 95% CI 1.3-3.3, p = 0.005).

CONCLUSIONS

From this observational study analyzing the outcomes of upper extremity hemodialysis access, axillary artery AVGs were associated with significantly lower patency rates and higher risk of steal syndrome than brachial artery AVGs.

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.

HD, Sarma P, Srikanth L, V. SK. Thrombophilic risk factors and ABO blood group profile for arteriovenous access failure in end stage kidney disease patients: a single-center experience

INTRODUCTION

Thrombosis of fistula occurs most frequently in end-stage kidney disease (ESKD) patients receiving hemodialysis. However, the role of thrombophilia in arteriovenous fistula (AVF) failure has not been well established. Hence, this study was aimed at assessing the roles of hereditary and acquired thrombophilic factors in association with AVF failure among patients with ESKD undergoing hemodialysis.

METHODS

A cross-sectional study was conducted on 100 ESKD patients, of whom 50 patients with well-functioning AVFs with no fistula failures earlier were enrolled as Group 1, and 50 patients who have had AVF failure were enrolled as Group 2. The hereditary factors as factor V Leiden, factor XIII, prothrombin, and methylene tetrahydrofolate reductase and the acquired factors as lipoprotein (a), fibrinogen, homocysteine, and anticardiolipin antibodies IgG and IgM were studied.

RESULTS

Among the hereditary factors, no statistically significant difference was observed in relation to factor V Leiden and Prothrombin (p > 0.05). However, for factor XIII and methylene tetrahydrofolate reductase, a statistically significant difference was observed between patients with well-functioning AVFs and patients who have had AVF failure (p < 0.05). We found a statistically significant increase in all the acquired factors in patients who have had AVF failure in comparison with patients with well-functioning AVFs (p < 0.001). Association between ABO blood groups and thrombophilic factors showed significant association between factor V Leiden, anticardiolipin antibody IgG and IgM and ABO blood groups (p < 0.05), whereas none of the other thrombophilic factors showed significant association (p > 0.05).

CONCLUSION

Thus, our study suggests significant role of acquired factors in causing AVF failure.

Shared decision-making in hemodialysis vascular access practice

Shared decision-making (SDM) is a process of collaborative deliberation in the dyadic patient-physician interaction whereby physicians inform the patients about the pros and cons of all available treatment options and reach an agreement with the patients on their preferred treatment plan. In hemodialysis vascular access practice, SDM advocates a deliberative approach based on the existence of reasonable alternatives-that is, arteriovenous fistula, arteriovenous graft, and central venous catheter-so that patients are able to form and share preferences about access options. In spite of its ethical imperative, SDM is not broadly applied in hemodialysis vascular access planning. Physicians and surgeons commonly deliver prescriptive fistula-centered recommendations concerning the approach to vascular access care. This paternalistic approach has been shaped by directions from long-held clinical practice guidelines and is reinforced by financial payment models linked with the prevalence of arteriovenous fistula in patients on hemodialysis. Awareness is growing that what may have initially seemed a medically and surgically appropriate approach might not always be focused on each individual's goals of care. Clinician's recommendations for vascular access often do not sufficiently consider the uncertainty surrounding the potential benefits of the decision or the cumulative impact of the decision on patient's quality of life. In the evolving health care landscape, it is time for the practice of hemodialysis vascular access to shift from a hierarchical doctor-patient approach to patient-centered care. In this article we review the current state of vascular access practice, present arguments why SDM is necessary in vascular access planning, review barriers and potential solutions to SDM implementation, and discuss future research contingent on an effective system of physician-patient participative decision-making in hemodialysis vascular access practice.

Sharp Needle Recanalization Technique for Peripheral Hemodialysis Arteriovenous Fistula Occlusion

PURPOSE

To determine the efficacy of a percutaneous sharp needle recanalization technique for the treatment of peripheral hemodialysis arteriovenous fistula (AVF) occlusion.

MATERIALS AND METHODS

This study included 13 patients (14 procedures) between May 2010 and February 2020 with non-thrombotic AVF occlusion wherein guidewire passage through the occluded segment had failed. We successfully passed the guidewire through the occluded segment using a sharp needle recanalization technique with Chiba or Colapinto needles, under ultrasound or fluoroscopic guidance. The type of AVF, site and length of occlusion, technical success, complications, and long-term patency were analyzed.

RESULTS

Technical success was achieved in 12 (85.7%) out of 14 procedures. The procedure failed in two patients due to the poor angle of approach in the axillary area and diffuse severe stenosis in the draining cephalic vein. In eight procedures, sharp needle recanalization was performed under ultrasound guidance, while the other six procedures were performed under fluoroscopic guidance. Chiba and Colapinto needles were used in five and nine procedures, respectively. The mean length of occlusion was 2.7 cm (range 1.8-4.2 cm). There was one case of mild complication, that is, mild contrast extravasation, which was treated by stent deployment. The post-intervention primary patency rates at 6 months, 1 year, and 2 years were 81.8%, 36.4%, and 18.2%, respectively.

CONCLUSION

The results of this limited series suggest that the sharp needle recanalization technique is a simple and effective method for the treatment of peripheral non-thrombotic AVF occlusion.

Effectiveness and safety of repeated percutaneous intervention in an office-based endovascular center in maintaining hemodialysis access

OBJECTIVES

Percutaneous dialysis access interventions are routinely used to maintain the patency of dialysis access despite the lack of data regarding their long-term effectiveness. This retrospective study was undertaken to study the effectiveness and safety of percutaneous dialysis access interventions in arm fistulas and bridge grafts in an office-based endovascular center.

METHODS

Patients who had a percutaneous dialysis access intervention in their upper extremity access site, performed at a single office-based endovascular center over a nine-year period (2007-2016) were included in this study. The patients' demographic factors, patency, and complications were analyzed. Patients were entered in the study after first percutaneous dialysis access intervention.

RESULTS

A total of 298 limbs in 259 patients had 913 procedures carried out over a nine-year period. There were 190 access arteriovenous fistulas and 108 arteriovenous grafts. The two most common arteriovenous fistulas were the brachiocephalic fistula (n = 74, 39%) and radio cephalic fistula (n = 69, 36%). Arteriovenous grafts were most commonly placed in the upper arm (n = 66, 61%) followed by the forearm (n = 42, 39%). The mean overall patency for all limbs was 50.86 months. Arteriovenous fistulas had a significantly longer patency than arteriovenous grafts (51.65 vs. 42.09 months; P = 0.01). In addition, patients with two or more percutaneous dialysis access intervention in their arteriovenous fistula had significantly greater patency than those with only one percutaneous dialysis access intervention (58.5 vs. 7.6 months; hazard ratio 0.41; P = 0.0008). This was not true for the arteriovenous graft group. Women represented 49% of the patient group. Their accesses had shorter patency than men (39.8 vs. 60 months; P = 0.0007).

CONCLUSIONS

This data support the use of repeated percutaneous dialysis access intervention to maintain long-term patency of dialysis access sites in an office-based endovascular center. Overall, fistulas have longer patency than grafts and women have poorer outcomes as compared to men.

Vascular access cannulation and haemostasis: a national observational study of French practices

BACKGROUND

We report the results of an observational study of arteriovenous fistula (AVF) cannulation and haemostasis practices in France.

METHODS

The study (sponsored by Brothier Pharmaceutical Inc.) was conducted in 150 dialysis units. Data obtained from 150 supervisory nurses, 1538 nurses and 3588 patients with an AVF were analysed.

RESULTS

The nurses reported using rope-ladder, area or buttonhole cannulation techniques in 68, 26 and 6% of cases, respectively. Metal needles were used most frequently (64%), with mainly a diameter of 15 G or 16 G. The needle was introduced with the bevel up in 56% of cases. Compression applied using dressings (in particular, pure calcium alginate dressings) was the method of choice for haemostasis of the puncture sites and was assessed as being strong by most of the nurses and very strong in cases of prolonged bleeding. Most (82%) of the patients reported the use of local anaesthetic before cannulation and 23% reported an allergic skin reaction to the anaesthetic. Bleeding of the puncture sites lasted for >10 min for 48% of the patients and it reappeared between two sessions for 29% of the patients. Whereas the nurses appeared to have a good understanding of AVF, more than half of the patients did not know how to care for it, with 55% requiring more information.

CONCLUSIONS

This study underlines the lack of national consensus concerning AVF cannulation practices. It suggests that haemostasis methods of the puncture sites can be improved and it highlights the need to improve patient knowledge.

Controlling the Poly(ε-caprolactone) Degradation to Maintain the Stemness and Function of Adipose-Derived Mesenchymal Stem Cells in Vascular Regeneration Application

Biodegradable poly(ε-caprolactone) (PCL) scaffolds with adipose-derived mesenchymal stem cells (ADSCs) have been used in vascular regeneration studies. An evaluation method of the effect of PCL degradation products (DP) on the viability, stemness, and differentiation capacities of ADSCs is established. ADSCs are cultured in medium containing different concentrations of PCL DP before evaluating the effect of PCL DP on the cell apoptosis and proliferation, cell surface antigens, adipogenic and osteogenic differentiation capacities, and capacities to differentiate into endothelial cells and smooth muscle cells. The results demonstrate that PCL DP exceed 0.05 mg mL^-1 may change the stemness and differentiation capacities of ADSCs. Therefore, to control the proper concentration of PCL DP is essential for ADSCs in vascular regeneration application.

A Novel Hybrid Silk Fibroin/Polyurethane Arteriovenous Graft for Hemodialysis: Proof-of-Concept Animal Study in an Ovine Model

To solve the problem of vascular access failure, a novel semi-degradable hybrid vascular graft, manufactured by electrospinning using silk fibroin and polyurethane (Silkothane), has been previously developed and characterized in vitro. This proof-of-concept animal study aims at evaluating the performances of Silkothane grafts in a sheep model of arteriovenous shunt, in terms of patency and short-term remodeling. Nine Silkothane grafts are implanted between the common carotid artery and the external jugular vein of nine sheep, examined by palpation three times per week, by echo-color Doppler every two weeks, and euthanized at 30, 60, and 90 days (N = 3 per group). At sacrifice, grafts are harvested and submitted for histopathology and/or scanning electron microcopy (SEM). No cases of graft-related complications are recorded. Eight of nine sheep (89%) show 100% primary unassisted patency at the respective time of sacrifice (flow rate 1.76 ± 0.61 L min^-1 , one case of surgery-related thrombosis excluded). Histopathology and SEM analysis evidence signs of inflammation and pseudointima inside the graft lumen, especially at the venous anastomosis; however, endoluminal stenosis never impairs the functionality of the shunt and coverage by endothelial cells is observed. In this model, Silkothane grafts grant safety and 100% patency up to 90 days.

Outcome of Percutaneous Intervention in Dysfunctional Loop versus Straight Arteriovenous Grafts in Hemodialysis Patients

Objective:

To compare the patency control of dysfunctioning forearm arteriovenous graft (AVG) using percutaneous transluminal angioplasty (PTA) in patients with loop versus straight grafts.

Materials and Methods:

Between January 2012 and March 2017, hemodialysis patients with forearm AVG were treated with PTA at two hospitals. We reviewed technical and clinical success rates of each procedure. Procedure time and patency of the graft were compared for all patients as well as for subgroups of stenosis only and thrombosis using paired-sample t-test and Kaplan-Meier analysis.

Results:

Sixty-six patients (mean age, 62.11 ± 11.85 years) underwent PTA. Thirty-eight patients (58%) had loop grafts and 28 (42%) had straight grafts. Among 66 patients, 54 (82%) had thrombosis. Technical success rate was 95.5% (only stenosis: 100%; thrombosis: 94%) and the mean procedure time was 48.00 ± 16.75 minutes in all patients. Although there was a tendency towards shorter procedure time in patients with loop grafts (45.24 ± 20.24 minutes) than those with straight grafts (51.85 ± 22.76 minutes), the difference was not statistically significant (p = 0.217), with or without thrombi. There was no statistical significance in primary and assisted primary patency (log rank 0.78, p = 0.38 in primary patency; log rank 0.88, p = 0.35 in assisted primary patency).

Conclusion:

Our study suggests there is no different patency outcome between straight and loop arteriovenous grafts after PTA.

What family physicians should know about interventional radiology?

Interventional radiology (IR) is a rapidly evolving specialty. The minimally invasive nature of the procedures has led to a paradigm shift in treating many disease processes from conventional surgery to interventional techniques that have become the first choice and the preferred method for the treatment of peripheral vascular disease, many aortic pathologies, and venous diseases. Interventional oncology procedures have become widely available for the treatment of solid hepatic and renal tumors. This includes palliative techniques for many advanced malignancies, and fluid drainage that is exclusively performed by interventional radiologists in many hospitals all around the world. Women's health-related procedures such as uterine fibroid embolization, fallopian tube recanalization, and embolization for pelvic congestion syndrome have become attractive choices for many patients. Family physicians (FPs) are the main source of patient referral to hospitals. However, there is a notable knowledge deficiency of IR among FPs in Saudi Arabia. This may be due to poor communication between FP and IR or the lack of FP's awareness of IR procedures. This is a nonsystematic review to introduce some IR procedures to FPs pertinent to their practice to optimize patient referral and management with the use of IR services. We focused on the most commonly performed IR procedures paying special attention to their clinical indications, benefits, and alternatives.

Possible Roles of Periostin in the Formation of Hemodialysis Vascular Access Stenosis after Polytetrafluoroethylene Graft Implantation in Dogs

Periostin, a recently found matricellular protein, has been implicated in neointima formation after balloon injury. However, the relationship between periostin and hyperplastic intima formation after PTFE graft implantation is unclear. Under mixed anesthesia, PTFE grafts were implanted between the canine carotid artery and jugular vein, and PTFE graft samples were harvested 1, 2, and 4 months after implantation. Intima formation started on the luminal surface of PTFE grafts at the venous anastomotic region 1 month after implantation. Thereafter, the increase in intimal volume was not only observed in the venous and arterial anastomotic regions, but also in the middle region of the PTFE grafts. In accordance with the increased intimal formation, time-dependent increases in mRNA expressions of periostin and transforming growth factor beta 1 (TGF-β1), as well as a strong positive correlation between periostin and TGF-β1, were observed. These findings suggest that periostin may play a very important role in the pathogenesis of hemodialysis vascular access stenosis through the acceleration of intimal formation. Thus, periostin may be a very important therapeutic target for the treatment of vascular access graft dysfunction in hemodialysis patients.

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.

A retrospective comparison analysis of results of drug-coated balloon versus plain balloon angioplasty in treatment of juxta-anastomotic de novo stenosis of radiocephalic arteriovenous fistulas

BACKGROUND

Juxta-anastomotic stenosis is a common issue of arteriovenous fistulas. We aimed to evaluate the results of percutaneous transluminal angioplasty with drug-coated balloon versus plain balloon for the treatment of juxta-anastomotic stenoses of mature but failing distal radiocephalic arteriovenous fistulas.

METHODS

A total of 80 patients with a juxta-anastomotic stenosis of distal radiocephalic arteriovenous fistula in our clinic between January 2016 and September 2017 were retrospectively analyzed. Patients were divided into two groups according to the type of treatment as drug-coated balloon - percutaneous transluminal angioplasty (n = 44) and plain balloon - percutaneous transluminal angioplasty (n = 43). Intra- and post-procedural data were recorded. Target lesion primary patency rate was evaluated at 6 and 12 months. Of all patients, 48 were females and 39 were males with a mean age of 56.3 ± 10.4 (range, 24-75) years. Both groups had mature fistulas, and the mean age of fistula was 11.3 ± 9.1 months in the drug-coated balloon - percutaneous transluminal angioplasty group and 10.3 ± 8.8 months in the plain balloon - percutaneous transluminal angioplasty group (p = 0.24).

RESULTS

There was no significant difference in the target lesion stenosis rate and the median lesion length between the groups. Technical and clinical success were achieved in both groups. Target lesion primary patency was similar at 6 months between the two groups (93.1% vs 81.3%, respectively; p = 0.14) but significantly higher for the drug-coated balloon - percutaneous transluminal angioplasty group at 12 months (81.8% vs 51.1%, respectively; p = 0.01).

CONCLUSION

Our study results suggest that the use of drug-coated balloon combined with percutaneous transluminal angioplasty is an effective treatment for juxta-anastomotic stenoses of mature but failing distal radiocephalic arteriovenous fistulas with significantly improved target lesion primary patency rates and reduced need for juxta-anastomotic reinterventions.

Outcomes of endovascular salvage of clotted arteriovenous access and predictors of patency after thrombectomy

OBJECTIVE

This study aimed to report the outcomes of endovascular salvage of clotted arteriovenous (AV) accesses and to determine potential predictors of poor patency rates after thrombectomy.

METHODS

Records of hemodialysis patients who underwent endovascular salvage of clotted AV access were reviewed retrospectively. Technical and clinical success rates, complication rates, and 3- and 6-month patency rates were determined. Multivariate analysis was performed to determine the predictors of patency after thrombectomy.

RESULTS

A total of 294 patients underwent endovascular salvage of clotted AV access during the study period; 156 patients had arteriovenous fistula, whereas the remaining 138 were arteriovenous grafts (AVGs). The technical and clinical success rates were 96.3% and 93.2%; the major and minor complication rates were 0.7% and 9.9%. Post-thrombectomy primary, assisted primary, and secondary patency rates were 62.9%, 76.2%, and 77.6% at 3 months and 43.9%, 59.5%, and 61.6% at 6 months. The patency rates were significantly better for arteriovenous fistula than for AVG except for 6-month assisted primary and secondary patency. Multivariate Cox regression analysis showed that prior thrombosis within 90 days was significantly associated with loss of primary patency (hazard ratio [HR], 1.90; 95% confidence interval [CI], 1.21-2.98; P < .01), assisted primary patency (HR, 2.42; 95% CI, 1.42-4.13; P < .01), and secondary patency (HR, 2.52; 95% CI, 1.40-4.53; P < .01). Having an AVG was also negatively associated with primary patency.

CONCLUSIONS

Most clotted AV accesses can be salvaged by endovascular technique. Recurrent thrombosis within 90 days is associated with poor short- and long-term patency even after successful endovascular reinterventions.

Forearm loop arteriovenous grafts preserve and may create new upper arm access sites

INTRODUCTION

This study evaluated the mid-term patency of forearm loop arteriovenous grafts and the dilation of previously inadequate upper arm basilic and cephalic veins after failed forearm loop arteriovenous graft.

METHODS

All access procedures from September 2009 to December 2015 were reviewed. Vein mapping measurements were used to determine whether there was "adequate" upper arm cephalic and/or basilic vein, defined as ⩾3 mm by duplex ultrasound, at the time of forearm loop arteriovenous graft creation. Outcomes of forearm loop arteriovenous graft were compared with upper arm arteriovenous fistula, and primary and cumulative patencies were evaluated.

RESULTS

Thirty-eight forearm loop arteriovenous grafts and 278 upper arm arteriovenous fistulas were created. In the forearm loop arteriovenous graft cohort, nine were inserted with adequate upper arm vein, group A, and 29 were inserted with inadequate upper arm vein, group B. Cumulative patency was lower for forearm loop arteriovenous graft compared with upper arm arteriovenous fistula at 6 months, 1 year, and 2 years (67% vs 91%, 61% vs 85%, and 49% vs 80%, respectively, P < .01). Comparison of group A forearm loop arteriovenous graft and upper arm arteriovenous fistula did not show a statistical difference in cumulative patency at 6 months, 1 year, and 2 years (P = .80, .62, and .70, respectively). Of group B with failed forearm loop arteriovenous graft, 36% became candidates for upper arm arteriovenous fistula with dilation of ipsilateral upper arm cephalic or basilic vein to ⩾3 mm.

CONCLUSION

In this study, forearm loop arteriovenous graft with adequate upper arm vein did not show a statistical difference in mid-term patencies compared with upper arm arteriovenous fistula. For those forearm loop arteriovenous grafts with inadequate upper arm vein, approximately one-third of patients became candidates for upper arm arteriovenous fistula demonstrating the benefits forearm loop arteriovenous graft.

Treatment of juxta-anastomotic stenoses for failing distal radiocephalic arteriovenous fistulas: Drug-coated balloons versus angioplasty

The aim of our study is to report the results of two types (type A, type B) paclitaxel drug-coated balloon compared with standard percutaneous transluminal angioplasty in the treatment of juxta-anastomotic stenoses of mature but failing distal radiocephalic hemodialysis arteriovenous fistulas. Two groups of 26 and 44 patients treated with two different drug-coated balloon are compared with a control group of 86 treated with standard percutaneous transluminal angioplasty. A color Doppler ultrasound was performed to evaluate stenosis and for treatment planning. We assess primary patency, defined as the absence of dysfunction of the arteriovenous fistulas, patent lesion or residual stenosis < 30% and no need for further reintervention of target lesion. Primary patency and secondary patency are evaluated after 12 months with color Doppler ultrasound for the whole arteriovenous fistulas, defined as absolute (absolute primary patency, absolute secondary patency) and target lesion. Postprocedural technical and clinical success was 100%. After 12 months, absolute primary patency is 81.8% for type A, 84.1% type B, and 54.7% for standard percutaneous transluminal angioplasty; target lesion primary patency is 92% type A, 86.4% type B, and 62.8% standard percutaneous transluminal angioplasty; absolute secondary patency is 95.4% type A, 95.5% type B, and 80.7% standard percutaneous transluminal angioplasty; target lesion secondary patency is 100% type A, 97.7% type B, and 80.7% standard percutaneous transluminal angioplasty. All the patients treated with drug-coated balloon (type A + type B) have an absolute primary patency of 83.3%, a target lesion primary patency of 87.9%, an absolute secondary patency of 95.5%, and a target lesion secondary patency of 98.4%. Our study confirms that the use of drug-coated balloon, indiscriminately among different brands, improves primary patency with statistically significant difference in comparison with standard percutaneous transluminal angioplasty and decreases reintervention of target lesion in juxta-anastomotic stenoses of failing distal arteriovenous fistulas maintaining the radiocephalic fistula as long as possible.

Vitamin K in Chronic Kidney Disease

Vitamin K is a composite term referring to a group of fat-soluble vitamins that function as a cofactor for the enzyme γ-glutamyl carboxylase (GGCX), which activates a number of vitamin K-dependent proteins (VKDPs) involved in haemostasis and vascular and bone health. Accumulating evidence demonstrates that chronic kidney disease (CKD) patients suffer from subclinical vitamin K deficiency, suggesting that this represents a population at risk for the biological consequences of poor vitamin K status. This deficiency might be caused by exhaustion of vitamin K due to its high requirements by vitamin K-dependent proteins to inhibit calcification.

A one-sheath inverse method in vascular access intervention therapy for hemodialysis patients

•

We describe a one-sheath inverse method in vascular access intervention therapy (VAIVT) for hemodialysis patients.

•

It allows VAIVT to be performed using one sheath with one approach site in cases in which lesions are present on the upstream and downstream sides.

•

Because vascular access location is usually superficial, the technique can be utilized with relative ease.

Introduction

Vascular access intervention therapy (VAIVT) is an essential interventional therapy in the field of hemodialysis therapy that allows for the long-term vascular access functionality to be maintained. The venous approach is often performed in VAIVT for arteriovenous fistula. When lesions are present on the upstream and downstream sides from the approach site, it is likely that two sheaths will be inserted from two facing punctures. However, we have adopted a one-sheath inverse method using a guidewire in such cases.

Case presentation

We herein describe the steps of the technique that we have performed and report the successful treatment of a 77-year-old woman who developed arteriovenous fistula failure.

Discussion

To the best of our knowledge, the concrete and detailed technique has not been reported in the English literature to date. The merit of the technique is that it allows VAIVT to be performed using one sheath with one approach site in cases in which lesions are present on the upstream and downstream sides from the approach site. The other benefits include pain reduction, a shortened operation time, and reduced costs. Because vascular access location is usually superficial, the technique can be utilized with relative ease.

Conclusion

A one-sheath inverse method is useful. We hope that the technique will be more widely recognized, allowing the technique to be applied to more cases.

Disruptive technological advances in vascular access for dialysis: an overview

End-stage kidney disease (ESKD), one of the most prevalent diseases in the world and with increasing incidence, is associated with significant morbidity and mortality. Current available modes of renal replacement therapy (RRT) include dialysis and renal transplantation. Though renal transplantation is the preferred and ideal mode of RRT, this modality may not be available to all patients with ESKD. Moreover, renal transplant recipients are constantly at risk of complications associated with immunosuppression and immunosuppressant use, and posttransplant lymphoproliferative disorder. Dialysis may be the only available modality in certain patients. However, dialysis has its limitations, which include issues associated with lack of vascular access, risks of infections and vascular thrombosis, decreased quality of life, and absence of biosynthetic functions of the kidney. In particular, the creation and maintenance of hemodialysis vascular access in children poses a unique set of challenges to the pediatric nephrologist owing to the smaller vessel diameters and vascular hyperreactivity compared with adult patients. Vascular access issues continue to be one of the major limiting factors prohibiting the delivery of adequate dialysis in ESKD patients and is the Achilles' heel of hemodialysis. This review aims to provide a critical overview of disruptive technological advances and innovations for vascular access. Novel strategies in preventing neointimal hyperplasia, novel bioengineered products, grafts and devices for vascular access will be discussed. The potential impact of these solutions on improving the morbidity encountered by dialysis patients will also be examined.

Effect of arteriovenous graft flow rate on vascular access hemodynamics in a novel modular anastomotic valve device

PURPOSE

Perturbed vascular access hemodynamics is considered a potential driver of intimal hyperplasia, the leading cause of vascular access failure. To improve vascular access patency, a modular anastomotic valve device has been designed to normalize venous flow between hemodialysis periods while providing normal vascular access during hemodialysis. The objective of this study was to quantify the effects of arteriovenous graft flow rate on modular anastomotic valve device vascular access hemodynamics under realistic hemodialysis conditions.

METHODS

Modular anastomotic valve device inlet and outlet flow conditions and velocity profiles were measured by ultrasound Doppler in a vascular access flow loop replicating arteriovenous graft flow rates of 800, 1000, and 1500 mL/min. Fluid-structure interaction simulations were performed to identify low wall shear stress regions on the vein wall and to characterize them in terms of temporal shear magnitude, oscillatory shear index, and relative residence time. The model was validated with respect to the Doppler measurements.

RESULTS

The low wall shear stress region generated downstream of the anastomosis under low and moderate arteriovenous graft flow rates was eliminated under the highest arteriovenous graft flow rate. Increase in arteriovenous graft flow rate from 800 to 1500 mL/min resulted in a substantial increase in wall shear stress magnitude (27-fold increase in temporal shear magnitude), the elimination of wall shear stress bidirectionality (0.20-point reduction in oscillatory shear index), and a reduction in flow stagnation (98% decrease in relative residence time). While the results suggest the ability of high arteriovenous graft flow rates to protect the venous wall from intimal hyperplasia-prone hemodynamics, they indicate their adverse impact on the degree of venous hemodynamic abnormality.

Effects of N-acetylcysteine on arterial neo-intimal hyperplasia in rat model of arteriovenous fistula

INTRODUCTION:

Arteriovenous fistula is the best choice for vascular access in hemodialysis patients. However, arteriovenous fistula dysfunction is a major clinical issue. The most common cause of arteriovenous fistula failure is intimal hyperplasia. In this study, we have investigated the effect of N-acetylcysteine on neo-intimal hyperplasia after arteriovenous fistula creation in rats.

METHODS:

This study was conducted in 24 rats which were randomly divided into two groups: control and N-acetylcysteine groups. An end-to-side anastomosis was made between the femoral artery and vein. The control group received distilled water intraperitoneally while the animals in N-acetylcysteine group received 300 mg/kg/day of N-acetylcysteine via the same route. After 28 days, the thickness of intima and media was measured using hematoxylin and eosin.

RESULTS:

There was no significant difference between the two groups regarding age ( p = 0.6) and weight ( p = 0.1). The mean intima thickness in N-acetylcysteine group was significantly less than control group (17 ± 20 and 119 ± 46 µm, respectively; p < 0.001). The mean intima/media thickness in the N-acetylcysteine group was significantly less than control group (0.5 ± 0.63 vs 2.05 ± 1.17 µm; p < 0.001).

CONCLUSION:

N-acetylcysteine is effective in inhibiting neo-intimal hyperplasia in a rat model of arteriovenous fistula.

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.

Placement of tunneled cuffed catheter for hemodialysis: Micropuncture kit versus Angiocath IV catheter

INTRODUCTION

Tunneled cuffed catheters provide stable, instantaneous, long-term intravenous access for hemodialysis. Because catheterization is often performed in emergency situations, speed and accuracy are emphasized.

METHODS

We retrospectively compared the Micropuncture kit with the standard 18-gauge Angiocath IV catheter for tunneled cuffed catheter insertion in the right jugular vein. From June 2016 to May 2017, 31 tunneled cuffed catheters were successfully inserted via the Micropuncture kit and another 31 via the Angiocath IV catheter. All patients underwent the same ultrasound-guided procedure performed by a single experienced interventionalist. Procedure time was the time from draping of the patient to the completion of povidone dressing after the catheterization. In our center, the Angio Lab nurse maintains records, including procedure time and method for every procedure. All patient records were retrospectively tracked through electronic medical record review. The primary outcome was procedure time and the secondary outcomes were complications and cost-effectiveness.

RESULTS

There were no significant differences in the patients' demographic data between the two groups. However, procedure time was significantly shorter in the Angiocath group than in the Micropuncture group (12.4 ± 3.5 vs 17.6 ± 6.9 min, p = 0.001); there were no serious complications, such as hemorrhage, pneumothorax, or hematoma, in both groups. Moreover, cost-effectiveness was better in the Angiocath group than in the Micropuncture group (0.34 vs 52 US$, p < 0.01).

CONCLUSIONS

Using the Angiocath IV catheter can reduce procedure time and cost with no severe complications. Moreover, experienced practitioners can reduce the risk of complications when using Angiocath. There are several limitations to this study. First, it was retrospective; second, it was not randomized; and finally, it was conducted by only one experienced interventionalist.

Quickening: Translational design of resorbable synthetic vascular grafts

Traditional tissue-engineered vascular grafts have yet to gain wide clinical use. The difficulty of scaling production of these cell- or biologic-based products has hindered commercialization. In situ tissue engineering bypasses such logistical challenges by using acellular resorbable scaffolds. Upon implant, the scaffolds become remodeled by host cells. This review describes the scientific and translational advantages of acellular, synthetic vascular grafts. It surveys in vivo results obtained with acellular synthetics over their fifty years of technological development. Finally, it discusses emerging principles, highlights strategic considerations for designers, and identifies questions needing additional research.

Differential gene expression patterns in vein regions susceptible versus resistant to neointimal hyperplasia

Arteriovenous hemodialysis graft (AVG) stenosis results in thrombosis and AVG failure, but prevention of stenosis has been unsuccessful due in large part to our limited understanding of the molecular processes involved in neointimal hyperplasia (NH) formation. AVG stenosis develops chiefly as a consequence of highly localized NH formation in the vein-graft anastomosis region. Surprisingly, the vein region just downstream of the vein-graft anastomosis (herein termed proximal vein region) is relatively resistant to NH. We hypothesized that the gene expression profiles of the NH-prone and NH-resistant regions will be different from each other after graft placement, and analysis of their genomic profiles may yield potential therapeutic targets to prevent AVG stenosis. To test this, we evaluated the vein-graft anastomosis (NH-prone) and proximal vein (NH-resistant) regions in a porcine model of AVG stenosis with a porcine microarray. Gene expression changes in these two distinct vein regions, relative to the gene expression in unoperated control veins, were examined at early (5 days) and later (14 days) time points following graft placement. Global genomic changes were much greater in the NH-prone region than in the NH-resistant region at both time points. In the NH-prone region, genes related to regulation of cell proliferation and osteo-/chondrogenic vascular remodeling were most enriched among the significantly upregulated genes, and genes related to smooth muscle phenotype were significantly downregulated. These results provide insights into the spatial and temporal genomic modulation underlying NH formation in AVG and suggest potential therapeutic strategies to prevent and/or limit AVG stenosis.

Near-Infrared Fluorescence Imaging of Matrix Metalloproteinase 2 Activity as a Biomarker of Vascular Remodeling in Hemodialysis Access

PURPOSE

To establish the capability of near-infrared fluorescence (NIRF) imaging for the detection of matrix metalloproteinase 2 (MMP-2) activity as a biomarker of vascular remodeling (VR) in arteriovenous fistulae (AVFs) in vivo.

MATERIALS AND METHODS

AVFs were created in the right groins of Wistar rats (n = 10), and sham procedures were performed in the contralateral groins. Fistulography via a left common carotid artery approach confirmed stenosis (> 50%) in a subset of animals (n = 5) 4 weeks after AVF creation. After administration of MMP-2-activated NIRF probe, near-infrared imaging was performed in vivo and ex vivo of both the AVF and the sham-treated vessels to measure radiant efficiency of MMP-2-activated NIRF signal over background. Histologic analyses of AVF and sham-treated vessels were performed to measure VR defined as inward growth of the vessel caused by intimal thickening.

RESULTS

AVFs demonstrated a significantly higher percentage increase in radiant efficiency over background compared with sham vessels (45.5 ± 56% vs 16.1 ± 17.8%; P = .008). VR in AVFs was associated with increased thickness of neointima staining positively for MMP-2 (161.8 ± 45.5 μm vs 73.2 ± 36.7 μm; P = .01). A significant correlation was observed between MMP-2 activity as measured by relative increase in radiant efficiency for AVFs and thickness of neointima staining positively for MMP-2 (P = .039).

CONCLUSIONS

NIRF imaging can detect increased MMP activity in remodeled AVFs compared with contralateral sham vessels. MMP-2-activated NIRF signal correlates with the severity of intimal thickening. These findings suggest NIRF imaging of MMP-2 may be used as a biomarker of the vascular remodeling underlying stenosis.

Substitution-rate based screening model to assess stenosis progression in experimental stenotic arteriovenous grafts

An arteriovenous graft (AVG) has a higher patency rate in stenosis progression at the venous anastomosis site, which causes coexisting inflow and outflow stenoses. This leads to increases in blood pressure, flow velocity, and flow resistance, resulting in hemodialysis (HD) vascular access dysfunction from early clots and thrombosis to the progression of coexisting stenoses. To prevent vascular access complications such as inflow or outflow stenoses, this study proposes a novel examination method in an experimental AVG system using a substitution-rate based screening model. In our practical measurements, we found that inflow and outflow channeled through a narrowed access indicated both pressure and resistance differences as the degree of stenosis (DOS) gradually increased. A substitution-rate matrix was conducted to replace bilateral pressure variations, while a transition probability matrix was calculated. Differences in transition probabilities were then used to distinguish between normal conditions and flow instabilities using the distance estimation method. The joint probability decayed from < 0.81 to 0.00 could be specified to identify the progression in stenosis levels from a DOS% = 50.0-95.0%. Average joint probabilities were found to be inversely related with the DOS using a non-linear regression (R>2 0.90). Hence, the joint probability could be specified as a critical threshold, < 0.81, to identify the severity stenosis level, DOS% ⩾ 70%, in the assessment of coexisting inflow and outflow stenoses. Experimental results suggest that the proposed model is superior to hemodynamic analysis and traditional intelligent method, and can be used for dysfunction screening during HD treatment.

Percutaneous intervention for restoration of patency of occluded lower limb arteriovenous dialysis access

Background

Arteriovenous (AV) fistula thrombosis is a serious complication in patients undergoing hemodialysis, often presenting with symptoms of venous hypertension, failure to dialysis and uremic symptoms. Treatment is aimed to provide symptomatic relief and to maintain hemodialysis access site patency.

Aim

To describe our initial experience in the endovascular treatment of lower limb AV dialysis access (AV fistula) thrombosis and/or obstruction in patients undergoing hemodialysis.

Settings and design

This was a retrospective study carried out in a tertiary care center. Study duration was 24 months. Follow-up was variable.

Materials and methods

Two patients with chronic kidney disease with stage 5 renal failure undergoing hemodialysis presented with lower limb arteriovenous dialysis access (arteriovenous fistula) failure between July 2014 and September 2016. Both the patients underwent endovascular treatment and were analyzed retrospectively.

Results and conclusion

Both the patient underwent successful endovascular treatment for the failure of the lower limb AV dialysis access thrombosis and/or obstruction. One patient had minimal dye extravasation during manipulation of the guide wire, which ceased spontaneously. On follow-up, both patients maintained patency of the dialysis access and are undergoing successful hemodialysis. One patient had a recurrence of the thrombosis of the fistula at 9^th month of the follow-up. Endovascular treatment was tried but we could not succeed. However, we found endovascular treatment safe and effective in treating AV fistula failures.

Restoration of Autologous Arteriovenous Fistula by Removal of the Occluded Short Venous Part and Venovenous End-To-End Anastomosis in a Hemodialysis Patient

Standard salvage procedures for occuluded autologous arteriovenous fistula (AVF) in a hemodialysis patient are endovascular and/or surgical therapy. When endovascular therapy and thrombectomy prove unsuccessful, it is most likely that creating a new AVF or arteriovenous graft will be considered. However, if the occuluded venous part is short, we have adopted an operative technique for repair of AVF by removal of the occluded short venous part and venovenous end-to-end anastomosis. To our knowledge, the efficacy and clinical course of restoration of AVF by the technique have not been reported to date. Here, we describe the technique and report the successful treatment of a hemodialysis patient who developed AVF occlusion.

Planning and evaluation for vascular access in the elderly

Vascular access is of vital importance for patients requiring dialysis therapies. AV fistulas have been endorsed by many professional societies as the access of choice, however, subsequent creation does not go without consequences. As the population ages and patients become more medically complex, access failure has become a major cause of treatment complication. For the elderly, this is especially true and there are multiple decision points that require careful reflection before an AVF is placed. This article reviews access considerations for AVF placement in the elderly population and considers the possibility that the fistula first approach to vascular access should not be an absolute.

Cross-Talk between Inflammation, Coagulation/Fibrinolysis and Vascular access in Hemodialysis Patients

This work aimed to study the association between fibrinolytic/endothelial cell function and inflammatory markers in chronic kidney disease (CKD) patients undergoing hemodialysis (HD) and recombinant human erythropoietin (rhEPO) therapies, and its relationship with the type of vascular access (VA) used for the HD procedure. As fibrinolytic/endothelial cell function markers we evaluated plasminogen activator inhibitor type-1 (PAI-1), tissue plasminogen activator (tPA) and D-dimers, and as inflammatory markers; C-reactive protein (CRP), soluble interleukin (IL)-2 receptor (s-IL2R), IL-6 and serum albumin levels. The study was performed in 50 CKD patients undergoing regular HD, 11 with a central venous dialysis catheter (CVC) and 39 with an arteriovenous fistula (AVF), and in 25 healthy controls. Compared to controls, CKD patients presented with significantly higher levels of CRP, s-IL2R, IL-6 and D-dimers, and significantly lower levels of PAI-1. The tPA/PAI-1 ratio was significantly higher in CKD patients. We also found statistical significant correlations in CKD patients between D-dimers levels and inflammatory markers: CRP, albumin, s-IL2R and IL-6. When comparing the two groups of CKD patients, we found that those with a CVC presented statistically significant lower levels of hemoglobin concentration and albumin, and higher levels of CRP, IL-6, D-dimers and tPA. Our results showed an association between fibrinolytic/endothelial cell function and increased inflammatory markers in CKD patients. The increased levels of D-dimer, tPA and inflammatory markers in CKD patients using a CVC, led us to propose a relationship between the type of VA chosen for HD, and the risk of thrombogenesis.

Vascular access for Chronic Dialysis using the Superficial Femoral Vein

Purpose

We report our experience in using the superficial femoral vein to create hemodialysis (HD) arteriovenous (AV) fistulas. Surgery was performed on six patients (four female, two male). Indications for surgery included previous fistula loss, graft infection and exhaustion of typical shunt sites.

Methods

The femoral vein was evaluated preoperatively, by Doppler ultrasound, harvested by one long incision on the anteromedial surface of the thigh, followed by suction drainage. In four patients, harvested veins were transplanted in the arm between the brachial artery and axillar vein, followed by an end-to-side anastomosis. In two patients, the venous graft remained on the anterior surface of the thigh. In those patients, they were extended with either a piece of polytetrafluoroethylene (PTFE) graft or the saphenous vein.

Results

Follow-up ranged between 14 months and 2 yrs, ensuring proper dialysis. Two patients presented with complications, including lower leg swelling and axillary lymphorrhea, which subsided spontaneously.

Conclusions

We recommend this type of AV fistula, especially in difficult cases, where all other classical vascular approaches have been used. However, the procedure is time consuming and requires experience in vascular surgery.

Risk of Vascular access Thrombosis in Patients with Systemic Lupus Erythematosus on Hemodialysis

Introduction

Anticardiolipin antibody is associated with increased risk of vascular access thrombosis (VAT) in hemodialysis (HD) patients. Systemic lupus erythematous (SLE) patients have a high prevalence of anticardiolipin antibodies, but it is not clear whether these patients are at high risk of developing vascular access thrombosis.

Methods

Thirty six SLE patients on HD, who had either an arterio-venous (AV) graft or AV fistula as vascular access, and were not on anticoagulation treatment, were retrospectively identified at Henry Ford Hospital. A similar number of patients without SLE, matched for age, sex, race and type of vascular access were selected as a control population. Vascular access thrombosis rate at one year was compared between two groups.

Results

Mean age at dialysis was 36±10 years in 36 SLE patients (28 females, 8 males) and was 38±6.4 years in 36 non-SLE patients (29 females, 7 males). Of all patients, 29/36 (80.5%) SLE and 27/36 (75%) non-SLE patients had AV grafts, whereas the rest had AV fistulas as vascular access (19.5% SLE and 25% non-SLE patients). Out of 36 SLE patients, 24 (66.6%) patients developed VAT at one year as compared to 14 (38.9%) patients in non-SLE group (p<0.05). The odds ratio of VAT in SLE patients was 3.1 (95% CI 1.2–8.2).

Conclusion

SLE patients on hemodialysis are more likely to develop vascular access thrombosis as compared to non-SLE patients.

Increased use of Catheters as Vascular Access: Is it Justified by Patients' Clinical Conditions?

Background

Over the last years many technical improvements have been made in hemodialysis treatment. Vascular access (VA) still remains an important problem. Although the use of indwelling vascular catheters is discouraged, in Europe there is an increasing use of them. The K/DOQI Guidelines recommend a native arteriovenous fistula (AVF) as VA of choice. As reported by DOPPS, there is considerable geographic variation in the distribution of type of VA used amongst hemodialysis patients. The aim of this study was to evaluate the time patients in four European countries have to wait before undergoing their first surgery for VA (AVF or graft).

Methods

All incident patients admitted to HD clinics located in Turkey, Italy, the UK and Portugal of the European FME clinics network between October 1, 2002 and September 30, 2004 were considered. Data were gained from the Clinical Database EuCliD®.

Results

2,152 patients (males 55.9%, mean age 62.5±15.7 years, diabetics 27%) were selected. Italy and Portugal had a higher proportion of elderly patients. At time of admission, the proportion of patients starting dialysis with AVF ranged between 23% and 60% from Turkey to Italy respectively. Patients with an indwelling catheter at admission are expected to undergo VA surgery as soon as possible. After 3 months of follow-up, about 75% of all patients had undergone surgery, however in the UK less than 50% of the patients had had a VA procedure. Overall, males have significantly higher probability of undergoing surgery, whilst elderly patients have a lower probability (27% and 14% respectively).

Conclusion

Significant differences exist between countries in the time interval from referral to creation of VA. Health care system related problems seem to be the major reason to explain such differences. Patients in the UK have longer waiting times than the other countries studied.

A porcine Model of Intimal-Medial Hyperplasia in Polytetrafluoroethylene Arteriovenous Grafts

Purpose

Vascular access polytetrafluoroethylene (PTFE) graft failure is a major cause of morbidity in the hemodialysis population. The most common cause of graft failure is thrombosis secondary to stenosis at the venous outflow tract. Venous outflow stenosis is characterized by intimal-medial hyperplasia. We have developed a porcine arteriovenous (AV) graft model that may be used to investigate this proliferative response and aid in the development of new therapies to prevent intimal-medial hyperplasia and improve graft patency.

Methods

Left carotid to right external jugular vein PTFE (6 mm) grafts were implanted in the necks of swine. Immediately following anatomosis, flow rates were recorded. In one group of animals (n = 4) the venous outflow tract was harvested after 7 days and morphometric analysis of intimal and medial area was performed. In a second group (n = 8) the graft patency was monitored until 28 days.

Results

All porcine PTFE fistula grafts were patent at 7 days and 100% patency was maintained until 14 days. After 28 days, 75% of the grafts failed due to thrombosis. The venous outflow tract developed a significant proliferative response. After 7 days the intimal and medial areas were 469 ± 9 μm2 and 875 ± 26 μm2 respectively. At 28 days the intimal and medial areas were 913 ± 55 μm2 and 1437 ± 182 μm2 respectively. Luminal flow rate of the venous outflow tract was reduced significantly (344 ± 11 ml/min at Day 0 to 129 ± 14 ml/min at Day 7, p < 0.05).

Conclusions

This porcine model rapidly, reliably and robustly reproduces the flow reducing stenosis and intimal-medial hyperplasia at the venous outflow tract of PTFE arteriovenous fistula. It represents a promising tool for investigating the mechanisms of intimal-medial hyperplasia, evaluating therapeutic interventions and new graft materials.

Factors Influencing Permanent Catheter Performance

Permanent dual lumen catheters (PDLC) provide an alternative vascular access in patients considered unsuitable for arteriovenous fistula, graft or peritoneal dialysis. However, the use of PDLC is often complicated by inadequate blood flow. The aim of this study was to identify catheter dysfunctions. We studied prospectively 57 chronic hemodialyzed patients, 73±11 years of age, with PDLC for 18±14 (1–48) months. Catheters were tunneled in silicone (MedComp Tesio n= 40) or in polyurethane (Permcath Quinton n = 11, GamCath Gambro n = 6) in left or right internal jugular (n = 49), in left or right subclavian (n = 3) and in right femoral vein (n = 5). We studied the blood viscosity indices (hematocrit, total protein, cholesterol and triglycerides), catheter intra-dialytic parameters (pre-pump and venous pressure), localization of the catheter tip (superior vena cava = SVC, right atrium = RA, inferior vena cava = IVC), blood pressure before and after hemodialysis during the 3 last dialyses, use of anticoagulant (ACT) or antiaggregant therapy (AAT) and previous infectious episodes. The mean blood flow was 269±37 ml/min (median 280 ml/min). The patients were divided according to the median value into groups I (Qb < 280, n = 28) and group II (Qb > 280, n =29). Results: Blood viscosity, patients’ mean arterial pressure and venous catheter line pressure did not differ between the two groups. Pre-pump pressure, at the start and at the end of treatment, was higher in group I. ACT, AAT and previous infectious episodes could not explain the low-performance. Blood flows of catheters localized in RA, SVC, and in IVC were respectively 287±20, 268±39, 244±27 ml/min. In the first case the Qb was significantly higher than IVC (p = 0.03) and SVC (p = 0.04).

In conclusion, the most important factor influencing blood flow rates seems to be the position of the catheter tip in the venous system. The best blood flows were found in catheters with the tip localized in the right cardiac cavities, while PLDC placed in inferior vena cava showed lower blood flow.

Spontaneous Re-Canalization of Thrombosed Polytetrafluoroethylene (PTFE) Grafts

Fibrinolysis is an important hemostatic process initiated either by tissue plasminogen activator (tPA) or pro-urokinase (pro-UK) released from endothelial cells. These agents act preferentially on plasminogen by converting it to the active molecule plasmin. This initiates the clot lysis process, which may take several days for completion. Most patients with end-stage renal disease (ESRD) have PTFE grafts for chronic hemodialysis. When these grafts are thrombosed, they are either surgically revised or percutaneously thrombolysed. When these measures fail another access is created without removing the clotted graft. However, it is possible that de-clotting of these thrombosed PTFE grafts can occur spontaneously. Once the graft develops an endothelial lining, these cells can contribute to the fibrinolytic process by secreting tPA or pro-UK. Because this endothelial lining may be less developed than that of a normal vessel, the fibrinolytic process may occur at a slower rate or not at all. Frequent cannulation during hemodialysis can denude existing endothelium, further contributing to the inadequacy of the graft to initiate thrombolysis. In practice, once the PTFE is clotted, the graft is ignored if it is not considered for declotting. In such circumstances the re-canalization process could be overlooked, resulting in the unnecessary placement of additional accesses. Presented here are three patients with clotted grafts in which re-canalization occurred without intervention.

The Role of the Staphylococcus Aureus Nasal Carriage and Type of Vascular Access in the Outcome of High-Risk Patients on Hemodialysis

Background

Populations of elderly and type-II diabetics are increasing worldwide. Therefore elderly diabetics on hemodialysis (HD), known to have higher nasal carriage rates, are also increasing. These patients are more often dialyzed through central venous catheters (CVCs). They represent the high-risk groups for Staphylococcus aureus linked vascular access-related septicemia (VRS) and ensuing mortality. The outcome of VRS in terms of mortality was studied in the three high-risk groups: elderly; type-II diabetics; elderly diabetics, following optimization of arteriovenous fistula (AVF) prevalence to at least 50%.

Methods

Persistent nasal carriage was defined by two or more positive standardized nasal swab cultures performed on 187 ESRD patients undergoing HD from July 1997 to July 2000. Peripheral blood samples were collected for culture and sensitivity on clinical suspicion of septicemia. Overall, AVF prevalence of over 50% was achieved through joint efforts of nephrology and vascular surgery departments.

Results

A nasal carriage rate of 47.6% was observed in this HD cohort. This included nasal carriage rates of 16.4% in <65 years non-diabetic (reference) group, 55.8% in elderly and 70.7% among type-II diabetics along with that of 75.5% in elderly-diabetic group. We achieved an overall AVF prevalence of 72.7% inclusive of 66.17% in elderly, 65.5% in type-II diabetics and 86.8% in reference group along with 37.7% in elderly-diabetic group. We recorded a mortality due to S. aureus nasal carriage-related VRS of 6.86% in elderly (RR-1.50, p-NS), 10.91% in type-II diabetics (RR-1.52, p<0.02) and 13.20% in the elderly-diabetic group (RR-2.87, p<0.0004) as compared to that of 4.4% per year in the reference group (assigned RR of one) with overall mortality of 7.3% per year.

Conclusions

AVF prevalence of over 50% is achievable in all the high-risk groups except among elderly-diabetics due to the predominance of peripheral vasculopathy. Optimizing AVF placement is a physiological and safer approach for achieving significant reductions in mortality associated with S. aureus nasal carriage-related VRS among high-risk groups.

Internal Jugular Vein Thrombosis after Positioning CVC in Dialysis Patients: The Most Common Ultrasound Patterns

Frequently patients are started on hemodialysis after the placement of a central venous catheter (temporary or tunneled) in the internal jugular vein (IJV). Currenty this procedure is facilitated by ultrasound probes that improve the rate of success of catheter placement in vessels and diminishes the possible complications, minimizing the gap between nephrologists with wide surgical expertise and those with limited surgical experience. Stenosis and thrombosis of the subclavia vein are well documented complications derived from the placement of the venous catheter. Internal jugular vein thrombosis is not seen very often due to scarce clinical evidence. In our paper we have been able to systematically document various extrinsic thrombotic complications outside the central venous catheter, by use of ultrasound (periluminar or related to the vessel).

Central Venous Catheter and the Hemodialysis Patient: A Difficult Symbiosis

In the last ten years, tunneled central venous catheters (pCVCs) have been increasingly utilized in chronic hemodialysis patients, sometimes in the place of fistulas. They have gained popularity for their unquestioned advantages, such as the possibility for immediate use. However, several problems have emerged following their diffusion. In this paper we review the main complications of pCVCs. Complications connected with insertion are generally due to an inaccurate approach to the vein. Ultrasonographic guidance has partially solved this problem and EC-ECG (endocavitary ECG) allows an accurate positioning of the tip. Infections, venous and/or pCVCs) thrombosis and dysfunctions are the most important catheter-related complications. Infections may occur with and without symptoms of systemic illness. Early diagnosis and appropriate antibiotic treatment are essential for saving the catheter. The pathogenesis of infections and strategies for prevention are discussed. Thrombosis and stenosis are well known complications of subclavian and jugular catheterization. In uremic patients, for temporary use, we suggest using the femoral position. Protocols for application of thrombolytic agents in pCVCs are considered. Dysfunction, defined as the failure to maintain a blood flow of at least 250 ml/min, remains the Achilles’ heel of the system. Adequate look therapy and tip position are only two basic aspects. In conclusion, a pessimistic outlook on the matter could lead us to consider that the advantages of catheter use are far outweighed by the disadvantages. However, we cannot avoid using central venous catheters in our dialysis units and a great challenge awaits both physicians and manufactures in the coming years.

Comparison of access blood flow and venous pressure measurements as predictors of arteriovenous graft thrombosis

Purpose

The purpose of the present study was to prospectively compare the predictive accuracy of static venous pressure (SVP); dynamic venous pressure (DVP) and access blood flow (ABF) in determining subsequent graft thrombosis and/or failure.

Methods

This study included 43 patients with functional arteriovenous grafts (AVG's) who underwent monthly serial measurements of SVP, DVP and ABF for 3 consecutive months. Patients were then followed for an additional 6 months. The primary end point was graft thrombosis.

Results

Six patients were excluded from the final analysis. Of the 37 patients completing the study, 7 episodes of graft thrombosis occurred within 6 months of follow up. Neither SVP nor DVP exhibited satisfactory sensitivity or specificity for graft thrombosis. Ten patients either began with or developed an ABF < 600 during the 3 months of measurements, but only 5 clotted. Δ ABF of >20% provided the best combination of sensitivity (86%) and specificity (90%) for graft thrombosis. In AVG's that have an ABF<600, it is those grafts with falling ABF that appear most likely to clot in the short term.

Conclusion

The study supports the concept that it is a falling level of access flow rather than the absolute level that is the most potent predictor of graft thrombosis.