Ankle-brachial index associates with arteriovenous fistula stenosis

BACKGROUND

Arteriovenous fistula (AVF) stenosis is associated with pre-existing arterial atherosclerosis of AVF and results in significant morbidity and hospitalization for hemodialysis patients. The ankle brachial index (ABI) is a noninvasive method of assessing atherosclerosis. This study was to examine whether ABI is a significant predictor for AVF stenosis.

METHODS

This was a retrospective, longitudinal cohort study. Patients with hemodialysis between 1 January 2016 and 31 December 2022 were reviewed. ABI was assessed in January 2016. AVF stenosis was diagnosed by fistulography.

RESULTS

A total of 82 patients were included. Forty-two patients experienced AVF stenosis. The univariate logistic regression analysis showed that AVF stenosis was associated with age (OR: 1.045, p = 0.033), DM status (OR: 5.529, p = 0.013), 7-year averaged cholesterol level (OR: 1.018, p = 0.034), 7-year averaged triglyceride level (OR: 1.007, p = 0.017), and ABI (OR: 0.011, p < 0.001). In multivariate logistic regression analysis, ABI was a strong predictor for AVF stenosis (OR: 0.036, p = 0.023). Then, a cut-off point of ABI with optimal sensitivity and specificity for AVF stenosis was 1.01. An analysis of time to events with adjustment for other variables showed that patients with ABI < 1.01 were significantly associated with AVF stenosis (HR: 3.859, p < 0.001).

CONCLUSIONS

ABI below 1.01 was associated with AVF stenosis. This finding may be useful in tailoring surveillance programs for monitoring AVF function.

Maintenance and Salvage of Hemodialysis Access

Many end-stage kidney failure patients require hemodialysis as a life-sustaining treatment. Hemodialysis access via arteriovenous fistula or graft creation is preferred over long-term dialysis catheters, but intervention to maintain patency and prevent access failure is common. Endovascular and open surgical techniques are both utilized to address the underlying etiology of failure. Endovascular options include balloon angioplasty, angioplasty with stenting, and drug-eluting stents. Open revision is commonly needed for recurrent stenosis, aneurysmal or pseudoaneurysmal change, hemodialysis access-induced distal ischemia, and infection. Treatment plans should be guided by patient's individualized goals of care and require a multidisciplinary approach to the management of this complex disease.

A Comparative Study of Continuous Versus Interrupted Suturing Technique in Creating a Vascular Access for Hemodialysis: An Institutional-Based Experience

Background Arteriovenous fistulas (AVFs) are considered the first and best access for patients with end-stage renal disease who need permanent vascular access for hemodialysis over arteriovenous grafts and central venous catheters for reasons that have been well-established. Poor early patency rates pose the biggest challenge in creating vascular access as they cause increased morbidity and economic/psychological concerns among patients. To minimize such effects, it is critical to use a patient-centered approach and carefully choose patients for AVF access creation. This study aimed to compare the primary patency of distal vascular access provided by continuous suturing versus that provided by interrupted suturing. Methodology This prospective study was conducted in the urology department of a superspecialty, tertiary care center from November 2021 to November 2022. Patency was assessed immediately after surgery (on the table), one month later, and six months later by palpating thrill and auscultating bruit. A total of 50 patients between the ages of 18 and 70 years who met the inclusion criteria were randomly assigned to two groups of 25 each. Results The baseline characteristics of both groups were comparable. At six months (p = 0.09), the continuous suturing group was observed to be somewhat better than the interrupted suturing group, with no significant difference in immediate and one-month patency rates. When compared to the continuous suturing group, the primary patency failure rate was significantly higher in the interrupted suturing group. Conclusions Thus, under appropriate circumstances, continuous sutures can be performed with greater ease, resulting in anastomosis that is as patent as that performed with interrupted sutures.

Demography and Outcomes of Arteriovenous Fistula: Challenges and Future Directions

The incidence and prevalence rates of treated end-stage kidney disease (ESKD) patients are on the rise worldwide. Hemodialysis remains the main modality of providing renal replacement therapy for the ESKD patients, and the preferred vascular access is an arteriovenous fistula (AVF). The objective is to assess the patency rates and primary failures of the AVF. All patients who attended the Royal Hospital in Muscat, Oman, from January 2010 to December 2014 for AVF creation were included in this study. Data were extracted from the hospital's electronic medical record system where data are entered prospectively. During the period of study from 2010 to 2014, 465 primary fistulae were created in 427 patients. The mean age of the patient was 58 years. Only 6% needed general anesthesia, while the rest were done under regional or local anesthesia. Fifty-one percent of the patients were diabetic. Preemptive AVF was constructed in only 12% of patients. Most cases (47%) had left brachiocephalic (BC) fistulae. The left radiocephalic (RC) fistulae constituted 25.7% and the left brachiobasilic fistulae 9.9%. The remaining were constructed in the right upper limb. The total patency was achieved in 80% of fistulae and the failure rate was 20% at 6 months. Whereas, at 12 months, the total patency rate was 71% and the failure rate was 29%. Thus, we can conclude that more than 50% of patients, half of them being females, were diabetics. This resulted in more fistulae being constructed in the arm, namely left BC fistulae and left RC fistulae. Furthermore, it is important to note that only a very small percentage of patients had an established preemptive AVF. These factors may be responsible for a failure rate of 20% and 29% of the AVFs at 6 months and 12 months, respectively.

The association between the locations of arteriovenous fistulas and patency rates: A systematic review and meta-analysis

BACKGROUND

The arteriovenous fistulas (AVF) continue to be the most prevalent type of vascular access for hemodialysis (HD). However, the appropriate locations of AVF are controversial. We conducted the meta-analysis to investigate the differences in patency between upper-arm and forearm AVF.

METHODS

PubMed, EMBASE, CENTRAL, and ISI Web of Science were searched to identify studies with differences in AVF patency at different locations. Reviewers searched the database, screened studies according to inclusion criteria, and conducted Meta-analysis.

RESULTS

A total of 12 studies involving 3437 patients were selected. Pooled data showed that primary patency (PP) of AVF were higher in upper-arm than forearm at 1 and 2 years (odds ratio [OR] = 1.54, p = 0.0005; OR = 2.45, p = 0.001), but the differences in cumulative patency (CP) were not statistically significant at 1 and 2 years (OR = 2.10, p = 0.08; OR = 2.16, p = 0.1). The differences in PP and CP between upper-arm and forearm AVF in patients older than 65 years were not statistically significant at 1 (OR = 1.61, p = 0.05; OR = 2.05, p = 0.17) and 2 years (OR = 3.40, p = 0.13; OR = 1.38, p = 0.16). In Asian patients, the differences in PP and CP between upper-arm and forearm AVF were not statistically significant at 1 (OR = 1.17, p = 0.41; OR = 1.02, p = 0.94) and 2 years (OR = 2.95, p = 0.08; OR = 1.23, p = 0.41).

CONCLUSIONS

In this study, the CP of upper-arm and forearm AVF was similar in overall population. There was no difference in PP and CP of AVF between upper-arm and forearm in Asian population or the elderly. The forearm AVF could be consider to be the first choice. for Asian patients or the elderly.

Inhibition of β-catenin signaling attenuates arteriovenous fistula thickening in mice by suppressing myofibroblasts

Background

Arteriovenous fistula (AVF) is the most important vascular access for hemodialysis; however, preventive treatment to maintain the patency of AVFs has not been developed. In endothelium, β-catenin functions in both the intercellular adherens complex and signaling pathways that induce the transition of endothelial cells to myofibroblasts in response to mechanical stimuli. We hypothesize that mechanical disturbances in the AVF activate β-catenin signaling leading to the transition of endothelial cells to myofibroblasts, which cause AVF thickening. The present study aimed to test this hypothesis.

Methods

Chronic kidney disease in mice was induced by a 0.2% adenine diet. AVFs were created by aortocaval puncture. Human umbilical vein endothelial cells (HUVECs) were used in the cell experiments. A pressure-culture system was used to simulate mechanical disturbances of the AVF.

Results

Co-expression of CD31 and smooth muscle alpha-actin (αSMA), loss of cell–cell adhesions, and the expression of the myofibroblast marker, integrin subunit β6 (ITGB6), indicated transition to myofibroblasts in mouse AVF. Nuclear translocation of β-catenin, decreased axin2, and increased c-myc expression were also observed in the AVF, indicating activated β-catenin signaling. To confirm that β-catenin signaling contributes to AVF lesions, β-catenin signaling was inhibited with pyrvinium pamoate; β-catenin inhibition significantly attenuated AVF thickening and decreased myofibroblasts. In HUVECs, barometric pressure-induced nuclear localization of β-catenin and increased expression of the myofibroblast markers, αSMA and ITGB6. These changes were attenuated via pretreatment with β-catenin inhibition.

Conclusions

The results of this study indicate that mechanical disturbance in AVF activates β-catenin signaling to induce the transition of endothelial cells to myofibroblasts. This signaling cascade can be targeted to maintain AVF patency.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00436-1.

The association of erythropoietin-stimulating agents and increased risk for AV-fistula dysfunction in hemodialysis patients. A retrospective analysis

BACKGROUND

Patients in maintenance hemodialysis (HD) need a patent vascular access for optimal treatment. The recommended first choice is a native arteriovenous fistula (AVF). Complications of AVF are frequent and include thrombosis, stenosis and infections leading to worsening of dialysis efficacy. Some known risk factors are age, gender and the presence of diabetes mellitus. The aim was to investigate if further risk variables are associated with dysfunctional AVF.

METHODS

This retrospective observational study included 153 chronic HD patients (Cases) referred to a total of 473 radiological investigations due to clinically suspected complications of their native AVF. Another group of chronic HD patients (n = 52) who had a native AVF but were without history of previous complications for at least 2 years were controls. Statistical analyses included ANOVA, logistic regression, parametric and non-parametric methods such as Student's T-test and Mann-Whitney test.

RESULTS

Among Cases, at least one significant stenosis (> 50% of the lumen) was detected in 348 occasions. Subsequent PTA was performed in 248 (71%). Median erythropoiesis-stimulating agent (ESA) weekly doses were higher in Cases than in Controls (8000 vs 5000 IU, p < 0.001). Cases received higher doses of intravenous iron/week than the Controls before the investigation (median 50 mg vs 25 mg, p = 0.004) and low molecular weight heparin (LMWH, p = 0.028). Compared to Controls, Cases had a lower level of parathyroid hormone (median 25 vs 20 ρmol/L, p = 0.009). In patients with diabetes mellitus, HbA1c was higher among Cases than Controls (50 vs 38 mmol/mol, p < 0.001). Multiple regression analysis revealed significant associations between Cases and female gender, prescription of doxazocin, and doses of ESA and LMWH. There was no difference between the groups regarding hemoglobin, CRP or ferritin.

CONCLUSION

In conclusion, the present study indicated that the factors associated with AVF problems were high doses of ESA, iron administration, and tendency of thromboembolism (indicated by high LMWH doses); the use of doxazocin prescription, however, requires further investigation.

Effects of cardiovascular medications on primary patency of hemodialysis arteriovenous fistula

While the patency of vascular access is essential for hemodialysis patients, optimal pharmaceutical treatment to maintain arteriovenous fistula (AVF) patency remains lacking. As cardiovascular diseases are highly prevalent in patients with end-stage renal disease, various cardiovascular medications have also been used to maintain AVF patency. However, previous studies revealed inconsistent therapeutic effects and a comprehensive evaluation of this issue is needed. The present retrospective, longitudinal cohort study included patients receiving successful AVF creation. The evaluated cardiovascular medications included antiplatelet agents, antihypertensive agents, nitrates and nitrites, statins, dipyridamole, and pentoxifylline. The outcome was AVF primary patency. All laboratory data and medication profiles were recorded at baseline and followed at 3-month interval, until the end of the 2-year study period. Cox proportional regression model with time-dependent covariates was used to evaluate the risk for AVF patency loss. A total of 349 patients were included in the present study, in which 57% were men and the mean age was 65 ± 14 years. Among the included patients, 40% used antiplatelet agents, 27% used dipyridamole and 36% used statins at baseline. Of all the evaluated cardiovascular medications, only dipyridamole showed significant association with a higher risk for loss of AVF patency. To evaluate the effect of combination of antiplatelet agents and dipyridamole, the patients were classified into four groups, I: combine use of antiplatelet agents and dipyridamole, II: antiplatelet only, III: dipyridamole only; IV: none of both were used. Of the four groups, group IV exhibited highest AVF patency (52.4%), which was followed by group III (42.7%), group II (40%), and group I (28.6%), respectively. Compared with group IV, only group I showed a significantly higher risk for AVF patency loss. None of the cardiovascular medications evaluated in the present study showed a beneficial effect on AVF patency. Furthermore, dipyridamole showed an association with a higher risk of AVF patency loss. We do not suggest a beneficial effect of dipyridamole on maintaining AVF patency, particularly in combination with antiplatelet agents.

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.

Study protocol for a prospective observational study to investigate the role of luminal pressure on arteriovenous fistula maturation

INTRODUCTION

Arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis due to its higher patency and lower infection rate. However, its suboptimal maturation rate is a major weakness. Although substantial risk factors for AVF maturation failure have been disclosed, modifiable risk factors remain unknown. During the AVF maturation process, an elevated luminal pressure is required for outward remodeling; however, excessively high luminal pressure may also be detrimental to AVF maturation, which remains to be defined. We hypothesized that higher AVF luminal pressure is harmful to its maturation, and investigate its potential as a modifiable factor to improve AVF maturation.

METHODS AND ANALYSIS

This prospective study includes patients undergoing surgical creation for a native AVF. The exclusion criteria were as follows: age <20 years, inability to sign an informed consent, and failure to create a native AVF due to technical difficulties. Demographic and laboratory profiles will be collected before AVF surgery. Vascular sonography will be performed within 1 week of AVF creation to measure the diameters, flow rates, and flow volumes of AVF and its branched veins. The pressure gradient within AVF will be estimated from the blood flow rates using the modified Bernoulli equation. The primary outcome is spontaneous AVF maturation defined as provision of sufficient blood flow for hemodialysis within 2 months of its creation without any interventional procedures. The secondary outcome is assisted AVF maturation, which is defined as AVF maturation within 2 months from its creation aided by any interventional procedure before the successful use of AVF.

DISCUSSION

While contemporary theory for AVF maturation failure focuses on disturbed wall shear stress, complicate assumptions and measurement preclude its clinical applicability. AVF luminal pressure, which may be manipulated pharmaceutically and surgically, may be a target to improve the outcome of AVF maturation.

TRIAL REGISTRATION

This study has been registered at the protocol registration and results system. The Protocol ID: NCT04017806.

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.

The forearm basilic vein looped transposition fistula as a tertiary option for upper limb vascular access

Introduction:

The forearm basilic vein can serve as an option for haemodialysis access but may not be possible in cases where the wrist arteries are unsuitable. In this setting, the forearm basilic vein can be used in a looped transposition with a brachial artery anastomosis.

Aims:

The aims of this study were to assess the outcome of forearm basilic vein looped transposition as an option for vascular access.

Material and methods:

Data from January 2007 to December 2010 were prospectively collected and analysed. Outcome measures were operative success, complications, maturation and primary and secondary patency following 5 years of follow-up.

Results:

From a total of 583 patients receiving autologous vascular access for haemodialysis, 24 (4.1%) underwent a forearm basilic vein looped transposition. The median age was 60 years (range, 27–80 years), with a slight male predominance (13 male:11 female). Mean follow-up was 34 months (1–60 months). Two patients died and other three were transplanted with subsequent fistula closure. All procedures were successful (100%); however, maturation failure occurred in one case (4.2%). No serious perioperative complications were observed. In two cases, we observed late false aneurysm formation requiring intervention. Primary patency at 1, 2, 3 and 5 years was the following: 77%, 62%, 21% and 10%, whereas secondary patency was the following: 81%, 71%, 61% and 32%, respectively.

Conclusion:

Autologous forearm basilic vein looped transposition is an effective surgical procedure for the creation of access for haemodialysis. This may be a useful option in patients with compromised peripheral arterial diameter or flow and should be considered in patients with a suitable forearm basilic vein.

Pre-Operative Vessel Mapping and Early Post-Operative Surveillance Duplex Scanning of Arteriovenous Fistulae

Purpose

To increase the proportion of dialysis patients using native arteriovenous fistulae (AVF), improved selection of the most appropriate procedure must be coupled with early access surveillance to determine which access would likely mature and when intervention might lead to access salvage. This study was aimed at auditing pre-operative vessel mapping and post-operative access surveillance against the primary outcome measure of AVF maturation.

Methods

Between January 2006 and August 2007, 113 AVF created in 101 patients were studied. Data on pre-operative vessel mapping, type of AVF, post-operative surveillance scans were analyzed against the outcome AVF.

Results

Pre-operative mapping and post-operative scanning were carried out in 86% and 91%, respectively. A maturing fistula on post-operative scan highly correlated with a satisfactory outcome (p<0.001). The sensitivity and specificity of the post-operative scan were 100% and 85%, respectively. There were 79 brachiocephalic and 34 radiocephalic fistulae with a primary failure rate of 23% and 47%, respectively, giving an overall failure rate of 30%. Nine fistulae had further intervention (angioplasty or thrombolysis) and five (56%) were salvaged. Seventy-two AVF matured satisfactorily giving a primary cumulative patency of 71% (72/102).

Conclusion

This study shows that preoperative vessel mapping provides useful information regarding the choice of AVF. Access surveillance duplex scanning at 6–8 weeks post-operatively is viable and has a high sensitivity and specificity for final outcome of fistula. Identifying AVF with potential problems early means that further intervention or surgery can be planned earlier, which will have a positive impact on patients.

A single treatment, using Far Infrared light improves blood flow conditions in arteriovenous fistula

BACKGROUND

A native arteriovenous fistula (AVF) is recommended for angio access in patients on chronic hemodialysis (HD). Fistula patency has been improved by exposure to Far Infrared light (FIR).

OBJECTIVE

To investigate whether a single FIR treatment could alter blood velocity, AVF diameter or inflammatory markers.

METHODS

Thirty patients with a native AVF in the forearm were included. Each patient was his/her own control. Ultrasound (US) examinations were performed before and after a single FIR treatment.

RESULTS

A single FIR treatment resulted in a significant increase in blood velocity over the AV fistula from a mean of 2.1 ± 1.0 m/s to 2.3 ± 1.0 m/s (p = 0.02). The diameter of the arterialized vein became wider; 0,72 cm ± 0.02 to 0,80 cm ± 0.02, (p = 0.006). The increase in fistula blood velocity correlated positively with base line serum- urate p = 0.004) and the increase in venous diameter with the base line plasma orosomucoid concentration (p = 0.005).

CONCLUSIONS

This study shows that a single FIR treatment significantly increased AVF blood velocity and vein diameter. Thus, one FIR treatment can help maturation of AVF in the early postoperative course.

Endothelial cell activation by hemodynamic shear stress derived from arteriovenous fistula for hemodialysis access

Intimal hyperplasia (IH) is the first cause of failure of an arteriovenous fistula (AVF). The aim of the present study was to investigate the effects on endothelial cells (ECs) of shear stress waveforms derived from AVF areas prone to develop IH. We used a cone-and-plate device to obtain real-time control of shear stress acting on EC cultures. We exposed human umbilical vein ECs for 48 h to different shear stimulations calculated in a side-to-end AVF model. Pulsatile unidirectional flow, representative of low-risk stenosis areas, induced alignment of ECs and actin fiber orientation with flow. Shear stress patterns of reciprocating flow, derived from high-risk stenosis areas, did not affect EC shape or cytoskeleton organization, which remained similar to static cultures. We also evaluated flow-induced EC expression of genes known to be involved in cytoskeletal remodeling and expression of cell adhesion molecules. Unidirectional flow induced a significant increase in Kruppel-like factor 2 mRNA expression, whereas it significantly reduced phospholipase D1, α4-integrin, and Ras p21 protein activator 1 mRNA expression. Reciprocating flow did not increase Kruppel-like factor 2 mRNA expression compared with static controls but significantly increased mRNA expression of phospholipase D1, α4-integrin, and Ras p21 protein activator 1. Reciprocating flow selectively increased monocyte chemoattractant protein-1 and IL-8 production. Furthermore, culture medium conditioned by ECs exposed to reciprocating flows selectively increased smooth muscle cell proliferation compared with unidirectional flow. Our results indicate that protective vascular effects induced in ECs by unidirectional pulsatile flow are not induced by reciprocating shear forces, suggesting a mechanism by which oscillating flow conditions may induce the development of IH in AVF and vascular access dysfunction.

Outcomes of initial hemodialysis access surgery in an Asian population

PURPOSE

Access-related morbidity contributes substantially to the costs of hemodialysis. The aim of this study was to examine the outcomes of initial hemodialysis access surgery at a single center in Singapore and to analyze factors which might influence survival of the surgically-created access.

METHODS

Patients undergoing their first hemodialysis access operations between January 2003 and December 2007 were retrospectively identified. Primary and assisted primary patency rates were determined by the Kaplan-Meier method. Data on age, sex, diabetic status, and prior tunneled central venous catheter (CVC) use were analyzed against the outcome of arteriovenous fistulas (AVF).

RESULTS

During the study period, 410 primary upper limb access operations were performed: 297 forearm AVF (72.4%), 91 upper arm AVF (22.2%), and 22 arteriovenous grafts (AVG; 5.4%). Men comprised 55.4%, 271 (66.1%) had diabetes, and 316 patients (77.1%) came to surgery with pre-existing CVC. Sixty-two percent of forearm AVF and 67% of arm AVF were used successfully. Age, sex, diabetes, and prior use of a CVC did not significantly affect the ability to use an AVF. Only in the female diabetic subgroup was an earlier loss of primary assisted patency of AVF recorded.

CONCLUSIONS

In our Asian population, we have demonstrated AVF patency rates equivalent to those of international centers. We now face the challenge of achieving a higher rate of pre-emptive AVF placement with a subsequent reduction in CVC use.

Preferred haemodialysis vascular access for diabetic chronic kidney disease patients: a systematic literature review

BACKGROUND

Vascular access problems are one of the main concerns in the diabetic end-stage kidney disease (ESKD) population. However, the optimal strategy for the establishment of vascular access in this population remains to be solved. We performed a systematic review in order to clarify the most advisable approach of vascular access planning in diabetic patients with ESKD.

METHODS

MEDLINE, EMBASE and CENTRAL databases were searched for English-language articles without time restriction through focused, high-sensitive search strategies. We included all studies providing outcome data on diabetics starting chronic haemodialysis treatment on the basis of the type of primary placed vascular access.

RESULTS

A total of 13 studies comprising over 2,800 participants with diabetes were reviewed in detail and included in the review. We found that diabetic patients using a dialysis catheter apparently experience a higher risk of death and infection compared with patients who successfully achieved and maintained an arteriovenous fistula as dialysis access. The comparison between the use of a graft or an autogenous fistula as dialysis access generated conflicting results. Primary patency rates appeared to be lower in diabetics versus non-diabetics.

CONCLUSIONS

Our study suggests that diabetic ESKD patients with dialysis catheters incur a higher risk of death in comparison to those who achieve an arteriovenous access. It is however unclear whether this is caused by residual selection bias or by a true advantage of native vascular access.

Vascular access in the obese: superficialisation of native radio-cephalic and brachio-cephalic fistulae

PURPOSE

The Department of Health estimates that currently in the UK, 61.3% of the population are overweight or obese (BMI >25 kg/m2). Fistulae in the obese often fail to mature or prove inadequate to needle due to excessive depth (>6 mm). This study is a summary of our experience with brachio and radio-cephalic vein superficialisation in the obese.

METHODS

From May 2008 to October 2012, 22 patients underwent superficialisation of the cephalic vein following radio-cephalic or brachio-cephalic Arterio-venous fistula (AVF) creation. Data were obtained from a prospective database (Cyberen®) and retrospectively analysed.

RESULTS

The study included 23 AVFs in 22 patients (seven males, 15 females), of which 13 were brachio-cephalic and 10 radio-cephalic. The mean age of the patients was 56 years (median 60, range 19-78 years). The mean BMI was 36.7 kg/m2 (median 32, 25-58 kg/m2). Six-week post procedure duplex ultrasonography recorded the mean fistula depth to be 7.7 mm (median 8 mm, 5-15 mm) and mean flow rates were 961 ml/min (median 800 ml/min, 320-1968 ml/min).Of the 23, 21 fistulae matured successfully. There were no procedure-related complications. During follow-up, two patients underwent transplantation prior to fistula use and three patients died of unrelated causes. The remaining 16 fistulae remain in use and under access surveillance.

CONCLUSIONS

Superficialisation of brachio/radio-cephalic fistulae is an excellent option to optimise the cephalic vein for needling, assisting primary patency. Superficialisation of the cephalic vein helps maintain long-term functional access in overweight and obese patients.

Computational model for prediction of fistula outcome

BACKGROUND

The creation and management of an autologous arteriovenous fistula (AVF) as vascular access (VA) for hemodialysis patients is still a critical procedure. The placement of a functional and long-lasting VA derives from adequate planning of the surgical procedure based on physical examination, vascular mapping and selection of the best modality for arteriovenous anastomosis. The risk of AVF non-maturation and early failure is high, even when all precautions are taken to minimize these events. In addition, AVF surgery may develop very high blood flow exposing the patient to the risk of heart failure or hand ischemia.

METHODS

The choices of the surgeons on the modalities to perform a surgical intervention for AVF should take into consideration several factors including patient clinical condition, arterial and venous vessel sizes and elasticity. However, these evaluations cannot give direct indication on VA outcome in terms of blood flow after AVF maturation. We then took advantage of theoretical models of vascular network hemodynamics and of computational fluid dynamics to develop a numerical tool for the prediction of potential blood flow of a planned VA surgery on the basis of preoperative ultrasound evaluation of arterial and venous sizes and blood flow.

RESULTS

Here we present the numerical model, previously developed and tested, and we describe the web-based application that has been developed to help during surgical planning.

CONCLUSIONS

The use of this tool in the clinical setting should allow to reduce the incidence of AVF non-maturation as well as incidence of VA complications.

Vascular Access Outcome in the Elderly Dialysis Patient in Combination With the Quality of Life

Purpose:

We performed a retrospective study on hemodialysis fistulae in patients aged 75 years and older.

Methods:

Dialysis records of 2 hospitals were searched for patients of 75 years and older who had primary autologous radiocephalic arteriovenous fistulae (RCAVFs) and brachiocephalic arteriovenous fistulae (BCAVFs). Outcome measures were primary, primary-assisted, and secondary patency rates. Also, quality of life (QOL) was measured.

Results:

A total of 107 fistulae were placed in 90 patients; 65 (61%) RCAVFs and 42 (39%) BCAVFs were created. The primary patency rate ( P = .026) and the primary-assisted patency rate ( P = .016) of BCAVFs were significantly higher than that of RCAVFs. Secondary patency rates at 1 year ( P = .01) and 2 years ( P = .035) were higher in BCAVFs than in RCAVFs.

Conclusions:

The BCAVFs give significantly higher primary and primary-assisted patency rates and also significantly higher secondary patency rates at 1 and 2 years. Therefore, we suggest the placement of elbow fistulae in the elderly patients. The QOL was surprisingly high in this population despite a high mortality rate.

Validation of a patient-specific hemodynamic computational model for surgical planning of vascular access in hemodialysis patients

Vascular access dysfunction is one of the main causes of morbidity and hospitalization in hemodialysis patients. This major clinical problem points out the need for prediction of hemodynamic changes induced by vascular access surgery. Here we reviewed the potential of a patient-specific computational vascular network model that includes vessel wall remodeling to predict blood flow change within 6 weeks after surgery for different arteriovenous fistula configurations. For model validation, we performed a multicenter, prospective clinical study to collect longitudinal data on arm vasculature before and after surgery. Sixty-three patients with newly created arteriovenous fistula were included in the validation data set and divided into four groups based on fistula configuration. Predicted brachial artery blood flow volumes 40 days after surgery had a significantly high correlation with measured values. Deviation of predicted from measured brachial artery blood flow averaged 3% with a root mean squared error of 19.5%, showing that the computational tool reliably predicted patient-specific blood flow increase resulting from vascular access surgery and subsequent vascular adaptation. This innovative approach may help the surgeon to plan the most appropriate fistula configuration to optimize access blood flow for hemodialysis, potentially reducing the incidence of vascular access dysfunctions and the need of patient hospitalization.

Chronic kidney disease and dialysis access in women

Chronic kidney disease currently affects one in nine Americans and over 500,000 have progressed to failure requiring kidney replacement therapy, with nearly 45% being women. Clinical Practice Guidelines have been developed in an effort to synthesize the latest literature, particularly randomized controlled trials, to assist clinical decision making. Women have different levels of kidney function than men at the same level of serum creatinine and may also lose kidney function over time more slowly than men. Although the arteriovenous fistulae have long been recognized as the preferred access for hemodialysis, women are less likely to initiate dialysis with an arteriovenous fistula in place. In addition, the female sex is regarded as a risk factor for access failure as well for complications such as steal. This article reviews treatment of women with chronic kidney disease, focusing on the difficulties they are perceived to have with dialysis access.

Association of maturation period blood pressure with dialysis access patency

Problematic dialysis vascular access is a major health issue. The purpose of this study was to evaluate for potentially modifiable factors associated with access patency, particularly, the association of early postoperative, or maturation period, blood pressure with patency. A retrospective review was performed of patients who had undergone placement of an arteriovenous fistula or graft. Demographic, operative, and postoperative factors were evaluated for possible association with access primary patency using univariate and multivariate Cox regression analyses. Seventy-three patients over a 3-year review period were examined. Overall analysis showed a significant association of absence of peripheral vascular disease, aspirin use, and absence of previous permanent dialysis access with higher primary patency rates. Fistula subgroup analysis showed that higher blood pressure during the maturation period relative to preoperative blood pressure was associated with lower patency rates. For grafts, race was significantly associated with patency, with blacks having higher patency rates than whites. Multiple clinical factors were found to have a significant association with dialysis access primary patency. The finding of an association of maturation period blood pressure with fistula patency suggests that the maturation period environment, specifically hemodynamics during this time, may play an important role in dialysis access patency.

Synthetic vascular hemodialysis access versus native arteriovenous fistula: a cost-utility analysis

OBJECTIVE

To determine the cost-effectiveness of 2 different vascular access strategies among incident dialysis patients.

BACKGROUND

Vascular access is a principal cause of morbidity and cost in hemodialysis patients. Recent guidelines and initiatives are intended to increase the proportion of patients with a fistula. However, there is growing awareness of the high prevalence of fistula failures and attendant complications.

METHODS

A decision analysis using a Markov model was implemented to compare 2 different vascular access strategies among incident dialysis patients: (1) placing an arteriovenous fistula (AVF1st) as the initial access followed by a synthetic vascular access if the AVF did not mature compared to (2) placing a synthetic vascular access (SVA1st) as the initial access device. The cost-utility was evaluated across a range of the risk of complications from temporary catheters and SVA.

RESULTS

Under base case assumptions, the AVF1st strategy yielded 2.19 quality-adjusted life years (QALYs) compared with 2.06 QALYs from the SVA1st strategy. The incremental cost-effectiveness was $9389 per QALY for AVF1st compared to SVA1st and was less than $50,000 per QALY as long as the probability of maturation is 36% or greater. AVF1st was the dominant strategy when the AVF maturation rate was 69% or greater.

CONCLUSION

The high risk of complications of temporary catheters and the overall low AVF maturation rate explain why a universal policy of AVF1st for all incident dialysis patients may not optimize clinical outcomes. Strong consideration should be given to a more patient-centered approach taking into account the likelihood of AVF maturation.

A retrospective review of basilic and cephalic vein-based fistulas

This study compares outcomes of basilic and cephalic vein fistulas for hemodialysis. A retrospective review of arteriovenous fistulas in a university hospital system was performed using charts and hemodialysis records. Patency and demographic data were assessed with life table analysis. One hundred fifty-six patients (88 males; 68 females) underwent creation of 172 autogenous fistulas (mean age 61 years; mean follow-up 78 weeks). There were 101 basilic vein transpositions and 71 cephalic vein fistulas. Primary patency did not differ significantly, while assisted primary patency was significantly better for basilic vein fistulas at one year (73% versus 53%: P = 0.024). Secondary patency was significantly better for basilic fistulas through three years (58% versus 52%; P = 0.027). Primary failure (thrombosis before access or failed maturation) was significantly higher for cephalic than basilic fistulas (28% versus 13%; P = 0.01). Maturation time, usage time and complications were not significantly significant. Thirty-three (33%) basilic vein-based fistulas and 12 (17%) cephalic vein fistulas required revision during follow-up. Basilic vein-based fistulas perform as well as or better than cephalic vein-based fistulas in terms of patency, maturation time, and usage time and complication rates, though requiring more re-interventions.

Mechanical buckling of veins under internal pressure

Venous tortuosity is associated with multiple disease states and is often thought to be a consequence of venous hypertension and chronic venous disease. However, the underlying mechanisms of vein tortuosity are unclear. We hypothesized that increased pressure causes vein buckling that leads to a tortuous appearance. The specific aim of this study was to determine the critical buckling pressure of veins. We determined the buckling pressure of porcine jugular veins and measured the mechanical properties of these veins. Our results showed that the veins buckle when the transmural pressure exceeds a critical pressure that is strongly related to the axial stretch ratio in the veins. The critical pressures of the eight veins tested were 14.2 +/- 5.4 and 26.4 +/- 9.0 mmHg at axial stretch ratio 1.5 and 1.7, respectively. In conclusion, veins buckle into a tortuous shape at high lumen pressures or reduced axial stretch ratios. Our results are useful in understanding the development of venous tortuosity associated with varicose veins, venous valvular insufficiency, diabetic retinopathy, and vein grafts.

Vascular access for dialysis: recent lessons and new insights

PURPOSE OF REVIEW

Vascular access complications are a major cause of excessive morbidity and mortality in the dialysis population. This review will focus on recent changes in vascular access practices and access management directly affecting patient outcomes.

RECENT FINDINGS

The proportion of patients dialyzing via arteriovenous fistulas continues to increase as a result of national initiatives. Maturation failure is now the main obstacle to successful use of fistulas. Arteriovenous grafts remain an important vascular access option for dialysis, and interventions to prevent progression of stenosis are being explored. Central venous catheter prevalence has increased and new interventions to address catheter-related complications such as thrombosis and infection are promising.

SUMMARY

Advances in understanding the factors related to fistula maturation failure will have a major beneficial effect on vascular access outcomes. New approaches to prevent graft and catheter-related complications should complement advances on fistula management. Optimal patient selection for specific access modalities and institution of timely access interventions tested in rigorous clinical trials should be the next step to improve access management.