Effect of preoperative sonographic mapping on vascular access outcomes in hemodialysis patients

Factors influencing maturation time of native arteriovenous fistulas

BACKGROUND

To determine the factors influencing the maturation time of native arteriovenous fistulas.

METHODS

A retrospective review was performed of hemodialysis patients from a single university-associated dialysis center from 2004 to 2009. Demographics, comorbidities, and insurance status were recorded. Maturation time was defined as the time from access creation until the access was able to be used regularly for hemodialysis for a period of 2 weeks.

RESULTS

A total of 249 patients were identified during the study period who had an arteriovenous fistula created that successfully matured; 104 (42%) patients were women and 145 (58%) were men. Most of the patients were Hispanic (82%). Ninety-seven (39%) of the patients had Medicaid-type insurance and 133 (53%) had Medicare. The mean age was 51 years, and 190 (76%) of the patients had diabetes. The overall mean maturation time was 79 days. Women had a significantly longer time to fistula maturation than males (91.9 days vs. 70.5 days, P = 0.0028). Diabetics also had a significantly longer maturation time than nondiabetics (92.5 days vs. 75.4 days, P = 0.0004). Age did not have an effect on maturation time. On multivariable analysis, sex remained significant (P = 0.007), however, diabetes lost its significance.

CONCLUSIONS

In this predominantly Hispanic hemodialysis population, women require longer fistula maturation times than men. The exact reasons for this are unknown based on this data. More study is required to determine the etiology of this gender discrepancy.

Primary Intraoperative Transluminal Angioplasty: A New Approach to Reduce the Early Failure of Distal Arteriovenous Fistulas

Purpose

About 8 years ago, we approached an intraoperative transluminal angioplasty (ITA) performed during the arteriovenous fistula (AVF) creation, to treat arterial or venous stenosis diagnosed by a preliminary ultrasound examination. Objective of this study is to validate the efficacy of ITA.

Methods

Early failure (EF) and failure to mature (FTM) were evaluated in 69 AVFs with ITA created in 58 patients in the last 3 years. In the same period, 160 patients received 188 AVFs without ITA and were considered control group. Of the two groups, age, comorbid factors, sex, primary and secondary patency rate (PR) were also analysed.

Results

The two groups were homogeneous for gender and age (70.4 + 11.1 years of ITA group vs. 66.3 + 14.4, p = 0.059). The incidence of diabetes, heart disease and peripheral artery disease was higher in the ITA group (43% vs. 17%, p<0.0001, 35% vs. 6%, p<0.0001 and 56% vs. 15%, p<0.0001, respectively). EF and FTM occurred in seven and eight cases in the ITA group and in 15 and 13 cases in the controls, respectively. Total failure occurred in 24% of ITA group and 14% of the controls (p = 0.2). The primary PR at 6, 12 and 24 months was 78%, 72% and 59% for ITA group and 85%, 78% and 78 % for control group (p<0.01). The secondary PR at 6, 12 and 24 months was 91%, 86% and 80% for ITA group and 95%, 95% and 92% for the controls (p<0.01).

Conclusions

Our ITA approach has allowed satisfactory results in patients at a high risk of AVF failure.

G. Value of preoperative sonographic vascular evaluation of haemodialysis access in upperlimb

OBJECTIVE

To know the value of preoperative Dopplerultrasonography vascular mapping of upper limb for hemodialysis access placement.

MATERIALS AND METHODS

Prospective ultrasonographic assess- ment of upper extremity vessels was performed in 60 patients prior to hemodialysis access placement and potential access sites were selected (based on the standard criteria). The findings were correlated with the operative findings. Discrepancies found between ultrasonographic and operative findings were analysed.

RESULTS

All the 60 patients who underwent vascular mapping had vascular access placed. 80% of them had native arteriovenous fistulae (AVF) placed. In 95% of patients, at the selected sites, the vascular parameters as determined by ultrasonography matched with the operative findings. In 5% of patients there were discrepancies between the ultrasonography findings and operative findings. There was no negative surgical exploration. There was strong correlation between the diameters measured by ultrasonography and surgery.

CONCLUSION

Preoperative ultrasonography vascular mapping prior to hemodialysis access placement has facilitated definite selection of potential sites in difficult patient population in whom evaluation by physical examination was inconclusive. It also helped in maximizing the native AVFs and decreasing the negative surgical exploration rates.

Preserving arteriovenous fistula outcomes during surgical training

PURPOSE

Arteriovenous fistulae (AVFs) are the preferred option for vascular access, as they are associated with lower mortality in hemodialysis patients than in those patients with arteriovenous grafts (AVGs) or central venous catheters (CVCs). We sought to assess whether vascular access outcomes for surgical trainees are comparable to fully trained surgeons.

METHODS

A prospectively collected database of patients was created and information recorded regarding patient demographics, past medical history, preoperative investigations, grade of operating surgeon, type of AVF formed, primary AVF function, cumulative AVF survival and functional patency.

RESULTS

One hundred and sixty-two patients were identified as having had vascular access procedures during the 6 month study period and 143 were included in the final analysis. Secondary AVF patency was established in 123 (86%) of these AVFs and 89 (62.2%) were used for dialysis. There was no significant difference in survival of AVFs according to training status of surgeon (log rank x2 0.506 p=0.477) or type of AVF (log rank x2 0.341 p=0.559). Patency rates of successful AVFs at 1 and 2 years were 60.9% and 47.9%, respectively.

CONCLUSION

We have demonstrated in this prospective study that there are no significant differences in outcomes of primary AVFs formed by fully trained surgeons versus surgical trainees. Creation of a primary AVF represents an excellent training platform for intermediate stage surgeons across general and vascular surgical specialties.

Vein diameter is the major predictor of fistula maturation

OBJECTIVES

Preoperative duplex ultrasound mapping of veins and arteries has been widely advocated to maximize the creation of native arteriovenous fistula (AVF) for hemodialysis access, but reliable diameter criteria have not been established. We sought to determine patient and anatomic variables predictive of fistula maturation in patients receiving their initial permanent hemodialysis access.

METHODS

All patients undergoing dialysis access creation from January 2003 to June 2007 were retrospectively reviewed. We analyzed fistula type and functional maturation rates (Society for Vascular Surgery [SVS] reporting standards) based on patient characteristics and findings on physical examination, preoperative vein mapping studies, or venography. Maturation and patency rates were determined by Kaplan Meier analysis. The following factors were analyzed: age, race, gender, body-mass index (BMI), fistula site, preoperative duplex vein diameter, diabetes, hyperlipidemia, HTN, prior central catheter placement, HIV, and history of IV drug abuse.

RESULTS

From January 2003 to June 2007, 298 vascular access procedures were performed. One hundred ninety-five (65%) were initial hemodialysis access procedures, among which a native AVF was created in 185 (95%); 158 patients with posterior radiocephalic AVF (PRCAVF, n = 24), wrist radiocephalic AVF (WRCAVF, n = 72), or brachiocephalic AVF (BCAVF, n = 62) had adequate follow-up and were included in the analysis. PRCAVF, WRCAVF, and BCAVF had 54%, 66%, and 81% maturation rates, respectively. Both the type of fistula type (P = .032) and vein size (P = .002) significantly affected maturation by univariate analysis. In contrast, by multivariate logistic regression analysis, vein diameter was the sole independent predictor of fistula functional maturation (P = .002).

CONCLUSION

In this series of 158 patients undergoing initial hemodialysis access creation, native AVF creation was performed in 95%. In contrast to previous reports, age, gender, diabetes, and BMI had no significant effect on functional maturation. By multivariate logistic regression analysis, vein diameter was the sole independent predictor of functional fistula maturation.

Role of far infra-red therapy in dialysis arterio-venous fistula maturation and survival: systematic review and meta-analysis

INTRODUCTION

A well-functioning arteriovenous fistula (AVF) is the best modality for vascular access in patients with end-stage renal disease (ESRD) requiring haemodialysis (HD). However, AVFs' main disadvantage is the high rate of maturation failure, with approximately one third (20%-50%) not maturing into useful access. This review examine the use of Far-Infra Red therapy in an attempt to enhance both primary (unassisted) and secondary (assisted) patency rates for AVF in dialysis and pre-dialysis patients.

METHOD

We performed an online search for observational studies and randomised controlled trials (RCTs) that evaluated FIR in patients with AVF. Eligible studies compared FIR with control treatment and reported at least one outcome measure relating to access survival. Primary patency and secondary patency rates were the main outcomes of interest.

RESULTS

Four RCTs (666 patients) were included. Unassisted patency assessed in 610 patients, and was significantly better among those who received FIR (228/311) compared to (185/299) controls (pooled risk ratio of 1.23 [1.12-1.35], p = 0.00001). In addition, the two studies which reported secondary patency rates showed significant difference in favour of FIR therapy--160/168 patients--compared to 140/163 controls (pooled risk ratio of 1.11 [1.04-1.19], p = 0.003).

CONCLUSION

FIR therapy may positively influence the complex process of AVF maturation improving both primary and secondary patency rates. However blinded RCTs performed by investigators with no commercial ties to FIR therapy technologies are needed.

Color Doppler ultrasound and arteriovenous fistulas for hemodialysis

Native arteriovenous fistula (AVF) is the vascular access of choice for hemodialysis patients. Compared with grafts and central venous catheters, AVFs last longer and are associated with fewer complications. The widespread use of the Doppler ultrasound (DUS) has increased the number of patients who are eligible for AVF by facilitating the identification of vessels that are suitable for fistula construction (preoperative vascular mapping). DUS can also extend native AVF survival by improving the early detection of complications (post-operative surveillance). It is the only imaging modality that furnishes both morphological and functional data on the native vascular access, and it is also the only imaging tool that can be used directly by the surgeon, an indisputable advantage. This review examines the numerous roles played by DUS in the construction and postoperative follow-up of AVFs, including preoperative vascular mapping, AVF maturation, and surveillance.

Endovascular techniques for cannulation difficulties in dialysis access

Although the arteriovenous fistula (AVF) is the access of choice for dialysis, its success as an access is limited by its high rate of failing to mature and its development of venous stenoses. This makes cannulation difficult or even impossible for dialysis staff. A variety of endovascular techniques exist for improving cannulation rates in AVFs. These include coil embolization of tributaries and balloon-assisted maturation in immature fistulae and fistuloplasty, stents and thrombus removal in mature failing access. This article aims to discuss the methods and evidence related to these techniques.

Arteriovenous Fistula Creation Using the Optiflow™ Vascular Anastomotic Connector: The Open (Optiflow PatEncy and MaturatioN) Study

Purpose

Arteriovenous fistulas (AVFs) are the preferred form of vascular access for hemodialysis. However, non-maturation and patency are major clinical problems. The Optiflow™ device is an implantable anastomotic connector used to standardize the creation of an AVF. Studies have suggested that the geometry of the anastomosis and experience of the surgeon impact patency and maturation rates. The Optiflow serves as a surgical template whereby the geometry and flow path of the anastomosis are predetermined. This prospective study was intended to evaluate maturation, patency and safety of the Optiflow.

Methods

Forty-one upper arm AVFs were created in 41 end-stage renal disease patients using the Optiflow device at two investigational sites. Patients were followed for 90 days with serial Doppler ultrasounds performed at approximately 14, 42 and 90 days to determine AVF maturation. The primary performance endpoint was unassisted maturation, defined as an outflow vein that was equal to or greater than 5 mm in diameter, and with flow equal to or greater than 500 mL/min without the need for any intervention intended to promote or maintain maturation. The primary safety endpoint was the rate of device-related serious adverse events.

Results

Unassisted maturation rates were 76%, 72% and 68% and unassisted patency rates were 93%, 88% and 78%, at 14, 42 and 90 days, respectively. There were no device-related serious adverse events.

Conclusions

The results suggest that the Optiflow is safe for its intended use and could play an important role in enhancing AVF maturation while standardizing the anastomotic technique.

Factors predicting failure of AV "fistula first" policy in the elderly

An arteriovenous fistula (AVF) is the preferential hemodialysis (HD) access. The goal of this study was to identify factors associated with pre-dialysis AVF failure in an elderly HD population. We used United States Renal Data System + Medicare claims data to identify patients ≥ 67 years old who had an AVF as their initial vascular access placed pre-dialysis. Failure of the AVF to be used for initial HD, was used as the outcome. Logistic regression model was used to identify factors associated with AVF failure. The study cohort consisted of 20,360 subjects (76.2 ± 6.02 year old, 58.5% men). Forty-eight percent of patients initiated dialysis using an AVF, while 52% used a catheter or an AVG. The following variables found to be associated with AVF failure when an AVF was created at least 4 months pre-HD initiation: older age (odds ratio [OR] 1.01; 95% confidence interval [CI] 1.00-1.02), female gender (OR 1.69; 95% CI 1.55-1.83), black race (OR 1.41; 95% CI 1.26-1.58), history of diabetes (OR 1.22; 95% CI 1.06-1.39), cardiac failure (OR 1.26; 95% CI 1.15-1.37), and shorter duration of pre-end-stage renal disease (ESRD) nephrology care (OR for a nephrology care of less than 6 months prior to ESRD of 1.22 compared with a pre-ESRD nephrology follow up of more than 12 months; 95% CI 1.07-1.38). OR for AVF failure for the entire cohort showed similar findings. In an elderly HD population, there is an association of older age, female gender, black race, diabetes, cardiac failure and shorter pre-ESRD nephrology care with predialysis AVF failure.

Risk factors associated with inadequate veins for placement of arteriovenous fistulas for hemodialysis

An arteriovenous fistula (AVF) between the radial artery and cephalic vein at the wrist is the preferred type of hemodialysis vascular access. However, in the practice of access placement, we are aware that some patients fail to form the standard forearm radial-cephalic AVF, owing to naturally small veins or acquired abnormal lesions of the veins. To identify the risk factors for failure to form the standard AVF, we examined 305 consecutive patients who underwent first-time access surgery at our hospital from January 2006 to December 2010. We compared the patients' characteristics between those having normal vessels and successfully forming the standard AVF, and those having apparently abnormal vessels and thus forming alternative types of access instead. Histories of major and minor surgery were specifically evaluated, assuming that surgical procedures in the past could potentially damage the superficial veins. We created 207 standard and 98 alternative accesses during the period and found that significantly more patients with alternative accesses (31 %) had undergone major surgery of a variety of specialties, in comparison with those with the standard AVF (15.0 %). Multivariate logistic analysis revealed that a history of major surgery (OR = 2.39, 95 %CI 1.29-4.47, p = 0.006) and female gender (OR = 1.87, 95 %CI 1.10-3.20, p = 0.02) were independent risk factors associated with failure to construct the standard AVF. Our results indicate that previous surgery can damage the superficial veins and cause venous abnormality, which makes construction of the standard AVF difficult. We propose that care should be taken to preserve the superficial veins when patients for whom dialysis therapy is a future possibility undergo surgical procedures, especially invasive ones.

Objectives and design of the hemodialysis fistula maturation study

BACKGROUND

A large proportion of newly created arteriovenous fistulas cannot be used for dialysis because they fail to mature adequately to support the hemodialysis blood circuit. The Hemodialysis Fistula Maturation (HFM) Study was designed to elucidate clinical and biological factors associated with fistula maturation outcomes.

STUDY DESIGN

Multicenter prospective cohort study.

SETTING & PARTICIPANTS

Approximately 600 patients undergoing creation of a new hemodialysis fistula will be enrolled at 7 centers in the United States and followed up for as long as 4 years.

PREDICTORS

Clinical, anatomical, biological, and process-of-care attributes identified pre-, intra-, or postoperatively.

OUTCOMES

The primary outcome is unassisted clinical maturation, defined as successful use of the fistula for dialysis for 4 weeks without maturation-enhancing procedures. Secondary outcomes include assisted clinical maturation, ultrasound-based anatomical maturation, fistula procedures, fistula abandonment, and central venous catheter use.

MEASUREMENTS

Preoperative ultrasound arterial and venous mapping, flow-mediated and nitroglycerin-mediated brachial artery dilation, arterial pulse wave velocity, and venous distensibility; intraoperative vein tissue collection for histopathologic and molecular analyses; postoperative ultrasounds at 1 day, 2 weeks, 6 weeks, and prior to fistula intervention and initial cannulation.

RESULTS

Assuming complete data, no covariate adjustment, and unassisted clinical maturation of 50%, there will be 80% power to detect ORs of 1.83 and 1.61 for dichotomous predictor variables with exposure prevalences of 20% and 50%, respectively.

LIMITATIONS

Exclusion of 2-stage transposition fistulas limits generalizability. The requirement for study visits may result in a cohort that is healthier than the overall population of patients undergoing fistula creation.

CONCLUSIONS

The HFM Study will be of sufficient size and scope to: (1) evaluate a broad range of mechanistic hypotheses, (2) identify clinical practices associated with maturation outcomes, (3) assess the predictive utility of early indicators of fistula outcome, and (4) establish targets for novel therapeutic interventions to improve fistula maturation.

Retrospective review of angiography before cannulation of newly created vascular accesses in hemodialysis patients

PURPOSE

To investigate vascular access status before first cannulation and the clinical implications of angiography performed before cannulation.

MATERIALS AND METHODS

A retrospective review of 300 consecutive patients who underwent angiography after vascular access surgery and before cannulation between August 2004 and April 2010 was performed. Angiography was performed 4-6 weeks after the surgery but before the first cannulation.

RESULTS

Angiography revealed 94 (31.3%) cases of severe stenosis (≥ 50% luminal narrowing) that required percutaneous transluminal angioplasty (PTA) or a second operation. No stenosis was observed in 122 (40.7%) cases, and mild stenosis (< 50% luminal narrowing) was observed in 84 (28%) cases. For the 94 cases with severe stenosis, PTA was performed in 66, and a second operation was performed in 16. In the other cases (n = 12), HD was maintained by a permanent catheter, or the patients were transferred to another institution. PTA was an immediate success in all patients who underwent the procedure except two. Of 84 patients with mild stenosis, 70 were followed for 1 year; vascular access dysfunction occurred in 15, and 11 of these underwent successful PTA. Of the 122 patients with normal angiographic findings, 102 were followed for 1 year, and vascular access dysfunction did not occur in any of these patients.

CONCLUSIONS

Early postoperative angiography before the first hemodialysis is helpful for the early detection and treatment of vascular access dysfunction.

Preoperative venous intimal hyperplasia, postoperative arteriovenous fistula stenosis, and clinical fistula outcomes

BACKGROUND AND OBJECTIVES

Arteriovenous fistulas often fail to mature, and nonmaturation has been attributed to postoperative stenosis caused by aggressive neointimal hyperplasia. Preexisting intimal hyperplasia in the native veins of uremic patients may predispose to postoperative arteriovenous fistula stenosis and arteriovenous fistula nonmaturation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This work explored the relationship between preexisting venous intimal hyperplasia, postoperative arteriovenous fistula stenosis, and clinical arteriovenous fistula outcomes in 145 patients. Venous specimens obtained during arteriovenous fistula creation were quantified for maximal intimal thickness (median thickness=22.3 μm). Postoperative ultrasounds at 4-6 weeks were evaluated for arteriovenous fistula stenosis. Arteriovenous fistula maturation within 6 months of creation was determined clinically.

RESULTS

Postoperative arteriovenous fistula stenosis was equally frequent in patients with preexisting venous intimal hyperplasia (thickness>22.3 μm) and patients without hyperplasia (46% versus 53%; P=0.49). Arteriovenous fistula nonmaturation occurred in 30% of patients with postoperative stenosis versus 7% of those patients without stenosis (hazard ratio, 4.33; 95% confidence interval, 1.55 to 12.06; P=0.001). The annual frequency of interventions to maintain arteriovenous fistula patency for dialysis after maturation was higher in patients with postoperative stenosis than patients without stenosis (0.83 [95% confidence interval, 0.58 to 1.14] versus 0.42 [95% confidence interval, 0.28 to 0.62]; P=0.008).

CONCLUSIONS

Preexisting venous intimal hyperplasia does not predispose to postoperative arteriovenous fistula stenosis. Postoperative arteriovenous fistula stenosis is associated with a higher arteriovenous fistula nonmaturation rate. Arteriovenous fistulas with hemodynamically significant stenosis frequently mature without an intervention. Postoperative arteriovenous fistula stenosis is associated with an increased frequency of interventions to maintain long-term arteriovenous fistula patency after maturation.

Non Contrast-Enhanced MRA versus Ultrasound Blood Vessel Assessment to determine the Choice of Hemodialysis Vascular Access

Purpose

The aim of this work was to establish the relationship between traditional blood vessel mapping for vascular access (VA) creation by B-mode ultrasound (US) and novel non contrast-enhanced magnetic resonance angiography (NCE-MRA), and to study the potential influence of the diameter assessment technique on the choice of hemodialysis vascular access.

Methods

A total of 27 end-stage renal-disease patients were included. They received routine US and a NCE-MRA examination of the upper extremity. Diameters were measured manually on US and semi-automatically on NCE-MRA. These measurements were statistically compared for the arteries and veins and for each measurement location. Furthermore, sensitivity and specificity of both modalities to predict VA location was investigated by comparison with an experienced surgeon. This analysis gave insight into the potential influence of vessel mapping modality on decision-making.

Results

Comparison of NCE-MRA with US for the arteries and veins, demonstrated a bias of 9% (limits −33%-78%) and 38% (limits −36%-198%), respectively. Statistically significant differences between the modalities on the individual locations were mainly found for the venous locations. The sensitivity and specificity for US to predict VA location was 1.0 and 0.74, respectively, while for NCE-MRA this was 0.88 and 0.39, respectively.

Conclusions

The results obtained indicate that extreme caution should be exercised when replacing one diameter measurement modality with the other. A further need exists to improve both vessel mapping protocols to obtain a geometric description of the upper extremity vasculature regardless of acquisition modality.

Assessment of Effects of Upper Extremity Exercise with Arm Tourniquet on Maturity of Arteriovenous Fistula in Hemodialysis Patients

Objective

This study was designed to investigate the effects of hand exercise using a tourniquet on arteriovenous fistula (AVF) maturity in patients with end stage renal disease.

Methods

Fifty patients were randomly allocated to 2 groups with 25 patients. After creating an AVF, in the control group, patients were asked to start doing simple hand exercise- opening and closing the fingers. In the second groups, patients underwent a structured isometric exercise program. The pre exercise and post exercise ultrasound examination were performed in the first 24 hours and 2 weeks after the operation respectively. Patients were also clinically evaluated at the end of the study.

Results

Post exercise ultrasound showed significant difference in the draining vein diameter, vein wall thickness, vein area and blood flow rate (BFR) (p-value: 0.009, 0.04, 0.02 and 0.02 respectively). The number of patients who had clinically mature AVFs in the case group was significantly more than the control group (13 vs. 5; p-value: 0.008).

Conclusion

We conclude that hand exercise using arm tourniquet affects most sonographic parameters which are associated with AVF maturity, and could be beneficial for acceleration of AVF clinical maturation.

Cumulative patency of contemporary fistulas versus grafts (2000-2010)

BACKGROUND AND OBJECTIVES

Comparisons of fistulas and grafts often overlook the high primary failure rate of fistulas. This study compared cumulative patency (time from access creation to permanent failure) of fistulas and grafts.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Vascular accesses of 1140 hemodialysis patients from two centers (Toronto and London, Ontario, Canada, 2000-2010) were analyzed. Cumulative patency was compared between groups using Kaplan-Meier survival curves and log-rank tests. Hazard ratios (HRs) for fistula failure relative to grafts and 95% confidence intervals (95% CIs) are reported.

RESULTS

There were 1012 (88.8%) fistulas and 128 (11.2%) grafts. The primary failure rate was two times greater for fistulas than for grafts: 40% versus 19% (P<0.001). Cumulative patency did not differ between fistulas and grafts for the patients' first access (median, 7.4 versus 15.0 months, respectively [HR, 0.99; 95% CI, 0.79-1.23; P=0.85]) or for 600 with a subsequent access (7.0 versus 9.0 months [HR, 0.93; 95% CI, 0.77-1.13; P=0.39]). However, when primary failures were excluded, cumulative patency became significantly longer for fistulas than for grafts for both first and subsequent accesses (61.9 versus 23.8 months [HR, 0.56; 95% CI, 0.43-0.74; P<0.001] and 42.8 versus 15.9 months [HR, 0.56; 95% CI, 0.44-0.72; P<0.001]). Results were similar for forearm and upper-arm accesses. Compared with functioning fistulas, grafts necessitated twice as many angioplasties (1.4 versus 3.2/1000 days, respectively; P<0.001) and significantly more thrombolysis interventions (0.06 versus 0.98/1000 days; P<0.001) to maintain patency once matured and successfully used for dialysis.

CONCLUSIONS

Cumulative patency did not differ between fistulas and grafts; however, grafts necessitated more interventions to maintain functional patency.

Morphologic and Functional Vessels Characteristics Assessed by Ultrasonography for Prediction of Radiocephalic Fistula Maturation

Purpose

Although native radiocephalic arteriovenous fistula (RCAVF) is the best vascular access for hemodialysis (HD), a major obstacle to increase its use is high frequency of fistulas that fail to mature. The aim of this study was to investigate and define cut-off values of morphologic and functional vessel parameters influencing successful RCAVF maturation using ultrasound.

Methods

A prospective, observational study was performed on 122 patients (66 men) who underwent primary RCAVF creation. Internal diameters of cephalic vein (CVd) and radial artery (ARd), venous distensibility (VD), resistance index (RI) and endothelial function by flow mediated dilatation (FMD) were determined by ultrasound examination before AVF placement. AVF maturation was observed by measuring blood flow (Qa) and CVd 0, 14 and 28 days after creation. Depending on the time when AVFs attained maturity (Qa ≥500 mL/min, CVd ≥5 mm), patients were divided into three groups: (i) successful maturation (after four weeks), (ii) prolonged maturation (within eight weeks) and (iii) failure to mature.

Results

Only 11% of patients failed to achieve a mature RCAVF. Successful AVF maturation occurred in 53% of patients and prolonged maturation in 36% of patients. ROC analysis defined the limits of variables relevant for RCAVF success (CVd >1.8 mm, ARd >1.6 mm, VD >0.4 mm). Female sex was associated with prolonged maturation (OR 0.35, 95% CI=0.17-0.72; P=0.005) having a significantly smaller ARd (1.83 vs. 2.01 mm, P=0.01) but better FMD (2981.5 vs. 2689.5, P=0.02) compared to men.

Conclusions

ARd ≤1.6 mm, CVd ≤1.8 mm and VD ≤0.4 mm are exact cut-off points, which best predict nonmaturation of RCAVF. Women need extended time for adequately matured AVF.

When should a patient receive an arteriovenous graft rather than a fistula?

There has been a dramatic increase in the placement and use of arteriovenous fistulas (AVF) in US patients with chronic kidney disease over the past few years, in accordance with strong recommendations by Fistula First Initiative and KDOQI guidelines. However, AVF nonmaturation remains a substantial obstacle to achieving functional AVFs in a subset of patients, despite the widespread use of preoperative vascular mapping to assist surgeons in planning access surgery, and the growing use of interventions to salvage nonmaturing AVFs. In the right patient, aggressive efforts result in a functioning AVF, which provides adequate dialysis with relatively few interventions required to maintain its long-term patency for dialysis. In the wrong patient, aggressive efforts to achieve a mature AVF may result in numerous failed surgical and percutaneous procedures and prolonged catheter dependence, with all its associated complications. Thus, strict recommendations to place an AVF in all dialysis patients might not benefit every patient, and may actually harm some patients. There are no randomized clinical trials to address which patients are more suitable for placement of an arteriovenous graft (AVG), rather than an AVF. However, there is a wealth of observational studies, which taken cumulatively, may assist clinicians in identifying those patients who should receive an AVG. In this article, we review the relevant published literature regarding this topic and provide suggestions for stratifying patients who should receive each type of vascular access.

The Clinical Utility of Vascular Mapping with Doppler Ultrasound Prior to Arteriovenous Fistula Construction for Hemodialysis Access

Purpose

To compare the outcomes of vascular access (VA) procedures performed using physical examination (PE) alone to PE and ultrasound vein mapping for assessment of patients needing hemodialysis access.

Methods

Comparative analysis of data obtained by retrospective review of records of 63 patients who underwent PE and vascular mapping (VM) using colored Doppler ultrasonography (CDUS) and 76 patients assessed by physical examination alone to schedule vascular access surgery. The parameters assessed to study the impact of these two different pre-operative assessment approaches included selection of surgical site, procedure, construction of arteriovenous fistulas (AVF) and grafts (AVG), negative surgical exploration rates and surgical outcomes (maturation and patency rates).

Results

The rate of successfully constructed AVF increased significantly from 75% to 97% (P=.001) with pre-operative ultrasonographic vascular mapping. In 22 patients (34.9%) the access planned with physical examination was modified based on CDUS examination. In 12 patients, the surgical site for AVF creation and type of surgical procedure were modified based on the CDUS results. Permanent access placement rates were significantly higher in patients assessed with CDUS (P=.001). All patients who underwent vascular mapping had successful VA construction while the PE group had a 18.4% negative surgical exploration rate. When fistulas were assessed at six months, the patency rate was 80.7% for the physical examination (PE) group and 93.4% for the vascular mapping (VM) group.

Conclusions

Pre-operative vascular mapping using CDUS significantly increases the success of AVF construction and patency.

Patients on Hemodialysis Are Better Served by a Proximal Arteriovenous Fistula for Long-Term Venous Access

Patients with end-stage renal disease should have arteriovenous fistula (AVF) formation 3 to 6 months prior to commencing hemodialysis (HD). However, this is not always possible with strained health care resources. We aim to compare autologous proximal AVF (PAVF) with distal AVF (DAVF) in patients already on HD. Primary end point is 4-year functional primary. Secondary end point is freedom from major adverse clinical events (MACEs). From January 2003 to June 2009, out of 495 AVF formations, 179 (36%) patients were already on HD. These patients had 200 AVF formations (49 DAVF vs 151 PAVF) in arms in which no previous fistula had been formed. No synthetic graft was used. Four-year primary functional patency significantly improved with PAVF (68.9% ± SD 8.8%) compared to DAVF (7.3% ± SD 4.9%; P < .0001). Five-year freedom from MACE was 85% with PAVF compared to 40% with DAVF ( P < .005). Proximal AVF bestows long-term functional access with fewer complications compared to DAVF for patients already on HD.

Ultrasound measurement of brachial artery elasticity prior to hemodialysis access placement: a pilot study

OBJECTIVES

Successful hemodialysis requires reliable vascular access that can deliver adequate blood flow. An arteriovenous fistula is preferred for access because of its longevity and low frequency of complications, but up to 60% of arteriovenous fistulas created surgically are never suitable for hemodialysis because of nonmaturation (insufficient vascular dilatation). Decreased arterial elasticity may impair dilatation, thereby affecting fistula maturation. This study evaluated the feasibility of brachial artery elasticity measurement in patients with chronic kidney disease obtained during routine pre-operative mapping ultrasound (US) imaging before hemodialysis access placement and compared the measurements to those obtained in healthy volunteers.

METHODS

Brachial artery functional US studies were collected from 75 patients undergoing routine preoperative mapping for hemodialysis access and 50 healthy volunteers. Vascular strain was calculated from the change in intima-media thickness between end systole and end diastole, and vascular stress was estimated from the pulse pressure. Assuming a linear elastic medium, the elastic modulus was estimated as the ratio of vascular stress to strain.

RESULTS

Elastic modulus measurements were significantly higher in patients than in volunteers (130 versus 100 kPa; P = .01). With combined volunteer and patient data, there was a significant correlation between elasticity and systolic blood pressure (R2 = 0.23; P < .001). Elasticity was correlated with age in volunteers but not in patients (R2 = 0.14; P = .017; R2 < .001; P = .829, respectively).

CONCLUSIONS

This analysis of clinical arterial vessel biomechanics shows that a noninvasive US measurement can detect elastic modulus differences between patients with chronic kidney disease and healthy individuals. Future studies will correlate the elastic modulus with histologic characteristics and eventual arteriovenous fistula maturation, which may provide supplemental information on arterial biomechanical properties as a useful addition to current predictors of fistula success.

Vascular access in patients receiving hemodialysis in Libya

PURPOSE

A native arteriovenous fistula (AVF) represents the optimal form of Vascular Access (VA) for patients receiving hemodialysis (HD). In Libya there are several barriers to AVF creation including lack of adequate preparation for dialysis and surgical services. We aimed to conduct the first comprehensive study of VA utilisation in HD patients in Libya.

METHODS

A prospective observational study included all adult patients receiving HD treatment in 25 HD facilities in Libya from May 2009 to Nov 2011. Researchers gathered data regarding VA through interviews with staff and patients as well as medical records. Patients with definitive VA were re-interviewed after 1 year.

RESULTS

At baseline the majority of patients (91.9%; n=1573) were using permanent VA in the form of AVF or arteriovenous graft. Patients with permanent VA were more likely to be male and less likely to be diabetic than those with CVCs. Most patients had commenced HD using a temporary CVC (91.8%). VA-related complications were: thrombosis (46.7%), aneurysm (22.6%), infection (11.5%) and haemorrhage (10.2%). Incident VA thrombosis was reported by 14.7% in 1 year. Independent risk factors for incident thrombosis were female gender and diabetes. Hospitalisation for VA related complications was reported by 31.4%.

CONCLUSIONS

Few patients in Libya initiate HD with definitive VA, but most achieve it thereafter. Improved dialysis preparation and increased provision of surgical services are required to increase the proportion of patients initiating HD with definitive VA and should be a priority in rebuilding health services in Libya after the recent conflict.

Association of hemodialysis central venous catheter use with ipsilateral arteriovenous vascular access survival

BACKGROUND

Central venous catheters frequently are used for hemodialysis vascular access while patients await placement and maturation of an arteriovenous fistula or graft. Catheters may cause central vein stenosis, which can adversely affect vascular access outcomes. We compared vascular access outcomes in patients with a history of ipsilateral and contralateral dialysis catheters.

STUDY DESIGN

Retrospective analysis of a prospective computerized vascular access database.

SETTING & PARTICIPANTS

Patients at a large medical center who initiated hemodialysis therapy with a catheter and subsequently received a fistula (n = 233) or graft (n = 89).

PREDICTOR

History of central venous catheter placement ipsilateral versus contralateral to the arteriovenous fistula or graft.

OUTCOME & MEASUREMENTS

Primary access failure (access never suitable for dialysis) and cumulative access survival (time from successful cannulation until permanent access failure).

RESULTS

For patients receiving a fistula, the primary failure rate was similar for those with ipsilateral and contralateral catheters (50% vs 53%; HR, 0.94; 95% CI, 0.71-1.26; P = 0.7), and time to fistula maturation was similar (101 ± 41 vs 107 ± 39 days; P = 0.5). However, cumulative fistula survival was inferior in patients with ipsilateral catheters (HR, 2.48; 95% CI, 1.33-7.33; P = 0.009). For patients receiving a graft, the primary failure rate was similar for those with ipsilateral and contralateral catheters (35% vs 38%; HR, 0.92; 95% CI, 0.49-1.73; P = 0.8), but cumulative graft survival tended to be shorter with ipsilateral catheters (HR, 2.04; 95% CI, 0.92-5.38; P = 0.07).

LIMITATIONS

Retrospective analysis, single medical center.

CONCLUSIONS

The primary failure rate of fistulas and grafts is not affected by the presence of an ipsilateral catheter. However, cumulative access survival is inferior in patients with prior ipsilateral catheters. Avoidance of ipsilateral catheters may improve long-term vascular access survival.

The choice of vascular access for therapeutic apheresis

Therapeutic apheresis (TA) is performed using either centrifugation-based or filter-based systems. The blood flow rate (BFR) used for TA using centrifugation-based systems is less than 100 mL/min. Because of this low BFR requirement, even peripheral veins can be considered as an option for TA, especially for less-frequent treatments and those performed for short periods. Other options for vascular access (VA) include central venous catheters (temporary or tunneled), totally implantable ports, and arteriovenous fistulae (AVF) or grafts (AVG). Nontunneled catheters should be considered as the choice of VA for relatively short-term treatments mainly in the inpatient settings. For long-term treatments, ports and tunneled catheters should be considered because of lower rates of infections compared to nontunneled catheters. However, studies in hemodialysis (HD) patients have demonstrated significantly higher morbidity and mortality rates associated with the use of tunneled catheters as compared to AVF. Therefore, if TA is being considered for several years, AVG and AVF would be the preferred options of VA. Studies in HD population indicate far better outcomes with the use of AVF as compared to AVG. This article, as presented at the Therapeutic Apheresis Academy in September 2011, is an overview of the available VA options for TA based on indication and duration of treatment. Pros and cons of each option are mentioned briefly. Finally, for those considered for AVF placement for chronic TA, specific recommendations are made for the care of AVF based on our own experience at University of Virginia.

Prevalence of arteriovenous fistulas in incident hemodialysis patients: correlation with patient factors that may be associated with maturation failure

BACKGROUND

Lok et al previously reported a risk equation for arteriovenous fistula (AVF) maturation failure. It is unclear whether this model or a more comprehensive model correlates with incident AVF use in the US hemodialysis population.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

195,756 adult patients initiating outpatient hemodialysis therapy in the United States between July 1, 2005, and December 31, 2009, with 6 months or more prior nephrology care.

PREDICTOR

Patient characteristics (age, peripheral vascular disease, coronary artery disease, and race) populating the AVF maturation failure risk equation and other demographic and clinical variables from the Centers for Medicare & Medicaid Services (CMS) Medical Evidence Report (CMS 2728).

OUTCOMES & MEASUREMENTS

AVF use at first outpatient dialysis treatment as recorded on the CMS 2728.

RESULTS

Using the risk categories defined by Lok et al, AVF use varied from 19.0% (very high risk) to 25.6% (low risk). In a model using only these risk categories, logistic regression showed lower ORs for moderate-, 0.90 (95% CI, 0.88-0.93); high-, 0.80 (95% CI, 0.78-0.83); and very high-risk patients, 0.68 (95% CI, 0.63-0.73) compared with low risk. In the expanded model, odds were lower for women, blacks, Hispanics, age older than 85 years, diabetes, peripheral vascular disease, congestive heart failure, other cardiac disease, and underweight. Odds were higher for hypertension, overweight, obesity, 12 months or more nephrologist care, most insurance types, and each successive year after 2005. Despite associations, the C statistic for the expanded model was 0.64.

LIMITATIONS

This analysis is limited by lack of access creation history before dialysis therapy initiation and minimal external validation of CMS 2728 data.

CONCLUSIONS

Clinical risk factors identified by Lok and expanded in this analysis have limited ability to predict incident AVF use. Even patients judged at highest risk can have successful AVF construction and initiate dialysis therapy through a functioning AVF.

Mapping of superficial extremity veins: normal diameters and trends in a vascular patient-population

Ultrasonic measurement of superficial extremity veins is a common procedure. To establish normal values for vein-size in a population of vascular patients and to assess if measurements remain unchanged over time, we analyzed a database with results of 28,130 measurements in 2420 separate saphenous and 3206 cephalic veins. Mean size of the great saphenous vein ranges from 2.3 mm to 4.4 mm but did not follow a tapering pattern as is often assumed. The distal calf segment is smaller than the ankle segment. The mean cephalic vein size in the upper arm (2.4 mm) was smaller than at the antecubital level (2.7 mm). A decrease in vein diameter over time was noted in many locations and this reached statistical significance (p < 0.005 for the thigh segment). The clinical significance of this is a need to repeat ultrasonic vein-mapping if more than a year elapses between ultrasound and surgical vein harvest.

Medial fibrosis, vascular calcification, intimal hyperplasia, and arteriovenous fistula maturation

BACKGROUND

Arteriovenous fistulas (AVFs) for hemodialysis frequently fail to mature because of inadequate dilation or early stenosis. The pathogenesis of AVF nonmaturation may be related to pre-existing vascular pathologic states: medial fibrosis or microcalcification may limit arterial dilation, and intimal hyperplasia may cause stenosis.

STUDY DESIGN

Observational study.

SETTING & PARTICIPANTS

Patients with chronic kidney disease (N = 50) undergoing AVF placement.

PREDICTORS

Medial fibrosis, microcalcification, and intimal hyperplasia in arteries and veins obtained during AVF creation.

OUTCOME & MEASUREMENTS

AVF nonmaturation.

RESULTS

AVF nonmaturation occurred in 38% of patients despite attempted salvage procedures. Preoperative arterial diameter was associated with upper-arm AVF maturation (P = 0.007). Medial fibrosis was similar in patients with nonmaturing and mature AVFs (60% ± 14% vs 66% ± 13%; P = 0.2). AVF nonmaturation was not associated with patient age or diabetes, although both variables were associated significantly with severe medial fibrosis. Conversely, AVF nonmaturation was higher in women than men despite similar medial fibrosis in both sexes. Arterial microcalcification (assessed semiquantitatively) tended to be associated with AVF nonmaturation (1.3 ± 0.8 vs 0.9 ± 0.8; P = 0.08). None of the arteries or veins obtained at AVF creation had intimal hyperplasia. However, repeated venous samples obtained in 6 patients during surgical revision of an immature AVF showed venous neointimal hyperplasia.

LIMITATIONS

Single-center study.

CONCLUSION

Medial fibrosis and microcalcification are frequent in arteries used to create AVFs, but do not explain AVF nonmaturation. Unlike previous studies, intimal hyperplasia was not present at baseline, but developed de novo in nonmaturing AVFs.