Vascular Access Surveillance Research Articles

Role of Color Doppler Ultrasonography in Assessment of Vascular Access Surveillance in Hemodialysis Patients.

Role of Color Doppler Ultrasonography in Assessment of Vascular Access Surveillance in Hemodialysis Patients.

Current state of vascular access in Singapore.

This article described the current state of vascular access management for patients with end-stage renal disease in Singapore. Over the past 10 years, there has been a change in the demographics of end-stage renal disease patients. Aging population and the increase in prevalence of diabetes mellitus has led to the acceleration of chronic kidney disease and increase in incidence and prevalence of end-stage renal disease. Vascular access care has, therefore, been more complicated, with the physical, psychological, and social challenges that occur with increased frequency in elderly patients and patients with multiple co-morbidities. Arteriovenous fistula and arteriovenous graft are created by vascular surgeons, while maintenance of patency of vascular access through endovascular intervention has been a shared responsibility between surgeons, interventional radiologists, and interventional nephrologists. Pre-emptive access creation among end-stage renal disease patients has been low, with up to 80% of new end-stage renal disease patients being commenced on hemodialysis via a dialysis catheter. Access creation is exclusively performed by a dedicated vascular surgeon with arteriovenous fistula success rate up to 78%. The primary and cumulative patency rates of arteriovenous fistula and arteriovenous graft were consistent with the results from many international centers. Vascular access surveillance is not universally practiced in all dialysis centers due to its controversies, in addition to the cost and the limited availability of equipment for surveillance. Timely permanent access placement, with reduced dependence on dialysis catheters, and improved vascular access surveillance are the main areas for potential intervention to improve vascular access management.

Access-related infections in two haemodialysis units: results of a nine-year intervention and surveillance program

BackgroundAccess-related infections are a major cause of morbidity and mortality in haemodialysis patients. Our goal was to decrease the rate of these infections by implementing an intervention and surveillance program.MethodsThis intervention took place in two haemodialysis units (Units A and B) and was a joint effort by the haemodialysis staff and the unit for infection prevention and control. It included reviewing the work methods and work space, observations on compliance with standard precautions and handling of the vascular access, creating a checklist and a designated kit for handling the vascular access and prospective surveillance of access-related infections.ResultsDuring a nine-year period, the haemodialysis units A and B treated 4471 and 7547 patients (mean number of patients per year: 497 (range 435–556) and 839 (range 777–1055), respectively). For most patients, the procedure was done through an arteriovenous fistula (66.7%, range 50.3–81.5%). The access-related infection rate decreased significantly in both haemodialysis units: from 3 to 0.9% (trend: p < 0.05, linear regression: p < 0.001) in Unit A and from 0.9 to 0.2% (trend: p < 0.05, linear regression: p = 0.01) in Unit B.ConclusionsAn intervention which included introduction of a checklist and designated kit, together with ongoing surveillance and feedback, resulted in a significant decrease in the access-related infection rates in both haemodialysis units.

Pro: Vascular access surveillance in mature fistulas: is it worthwhile?

Guidelines recommend regular screening of mature arteriovenous fistulas (AVFs) for preemptive repair of significant stenosis (≥50% lumen reduction) at high risk of thrombosis, identifiable from clinical signs of access dysfunction (monitoring) or by measuring access blood flow (Qa surveillance), which also enables stenosis detection in functional accesses. To compare the value of Qa surveillance versus monitoring, a meta-analysis was performed on the randomized controlled trials (RCTs) comparing the two screening strategies. It emerged that correcting stenosis identified by Qa surveillance significantly halved the risk of thrombosis [relative risk (RR) = 0.51, 95% confidence interval (CI) 0.35-0.73] and access loss (RR = 0.47, 95% CI 0.28-0.80) in comparison with intervention prompted by clinical signs of access dysfunction. One small RCT aiming to identify an optimal Qa threshold showed that stenosis repair at Qa >500 mL/min produced a significant 3-fold reduction in the risk of thrombosis (RR = 0.37, 95% CI 0.12-0.97) and access loss (RR = 0.36, 95% CI 0.09-0.99) in comparison with intervening when Qa dropped to <400 mL/min as per guidelines. To test the real-world benefits of Qa surveillance, the expected RCT-based thrombosis and access loss rates with Qa surveillance were compared with the rates with monitoring reported in observational studies: the expected thrombosis and access loss rates with surveillance were only lower than with monitoring when a Qa >500 mL/min was considered (2.4, 95% CI 1.0-4.6 and 2.2, 95% CI 0.7-5.0 versus 9.4, 95% CI 7.4-11.3 and 10.3, 95% CI 7.7-13.4 events per 100 AVFs-year, P ≤ 0.024), suggesting that in clinical practice adopting Qa surveillance may only be worthwhile at centres with high thrombosis and access loss rates associated with monitoring, and adopting Qa thresholds >500 mL/min for elective stenosis repair.

Con: Vascular access surveillance in mature fistulas: is it worthwhile?

The risks and benefits of hemodialysis arteriovenous (AV) access surveillance have been debated since the introduction of AV access surveillance techniques. The debate is fuelled by the lack of robust, high-quality evidence with consistent and comparable patient-important outcomes. Additionally, there is a lack of clarity regarding the diagnostic cut points for AV access stenosis using the various surveillance techniques, questions about the appropriateness of the 'knee-jerk' response to intervention on a stenosis >50% regardless of the presence of clinical indicators and whether the intervention results in desired patient-important outcomes. The physiology of the AV access is complex considering the different hemodynamics within an AV fistula, which vary by time of dialysis, location, size of vessels and location of the stenosis. The current evidence suggests that the use of AV access surveillance in an AV fistula does detect more stenosis compared with clinical monitoring alone and leads to an increased number of procedures. It remains uncertain if that leads to improved patient-important outcomes such as prolonged AV fistula patency. Vascular access is an essential component of hemodialysis and further study is needed to clarify this long-standing debate. There needs to be better distinction between the strategies of vascular access surveillance, clinical monitoring with clinical indictors and preemptive intervention and their respective impacts on patient-important outcomes. Randomized controlled studies must be conducted with defined indications for intervention, reproducible methods of intervention and clinically important AV fistula and patient outcomes. The current guidelines need to be challenged and revised to permit these necessary studies to be done.

Prediction of vascular access stenosis: Blood temperature monitoring with the Twister versus static intra-access pressure ratio.

BackgroundThe Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines recommend intra-access flow (Qa) measurement as the preferred vascular access surveillance method over static intra-access pressure ratio (SIAPR). Recently, it has become possible to perform Qa measurement during hemodialysis using thermodilution method called blood temperature monitoring (BTM) with the Twister device. The aim of this study was to investigate the correlation between Qa by BTM and SIAPR and to compare the performance of two tests in prediction of vascular access stenosis.MethodsThe study was performed from January 2016 to November 2017 and included 97 patients with arteriovenous fistulas (AVF). Qa by BTM and SIAPR were simultaneously measured every 1~3 months with a total of 449 measurements during study period.ResultsIn our study population, mean age was 59.9±10.0 years and 61.9% were diabetes. The mean Qa obtained by BTM was 1186±588 mL/min. There was no correlation between Qa by BTM and venous SIAPR (r = 0.061, P = 0.196). Angiography identified 36 stenotic AVFs (37.1%) among the study subjects. They included 13 cases with only inflow stenosis, 6 with only outflow stenosis, and 17 with stenosis on both sides. Receiver-operating characteristic (ROC) curve analysis showed that Qa by BTM had higher discriminative ability to diagnose vascular access stenosis compared to SIAPR (P <0.001). The Qa less than 583 mL/min showed the highest diagnostic accuracy in vascular stenosis prediction.ConclusionIntradialytic measurement of Qa by BTM showed better diagnostic power over venous SIAPR in prediction of vascular access stenosis.

Diameter of inflow as a predictor of radiocephalic fistula flow.

The optimal method for vascular access surveillance is largely unknown. A previous case-control study suggested a simplified anatomical measure obtained by Doppler ultrasound-the narrowest segment of the circuit or "minimal luminal diameter" may identify patients with a dysfunctional radiocephalic arteriovenous fistula. The relationship between minimal luminal diameter and access flow (Qa) in the radiocephalic arteriovenous fistula has not previously been studied. Patients undergoing Doppler ultrasound of a radiocephalic arteriovenous fistula over an 8-month period were identified retrospectively. Minimal luminal diameter was identified and demographic and clinical data were collected. Qa was estimated by Doppler estimation of brachial artery flow. The relationship between minimal luminal diameter and Qa was examined by correlation and using different levels of minimal luminal diameter as a simplified measure to detect or exclude low Qa (<600 mL/min). A total of 81 Doppler ultrasound scans were performed. In all, 26 scans demonstrated brachial artery flow <600 mL/min. Simple logistic regression indicated a weak statistical relationship between the minimal luminal diameter and Qa (R2 = 0.27, p < 0.01). Minimal luminal diameter performed poorly as a marker of low Qa with low specificity, however, showed high negative predictive value for ruling out low Qa at a minimal luminal diameter of 3.2 mm or higher (94%). Qa estimated by brachial artery flow correlated well with Qa estimated by indicator dilution (R2 = 0.83, p < 0.01) without significant mean difference or proportional bias. Minimal luminal diameter correlates weakly with Qa. Low minimal luminal diameter values should not be used in isolation to determine low Qa for a radiocephalic arteriovenous fistula. Conversely, minimal luminal diameter >3.2 mm largely excludes a low-flow radiocephalic arteriovenous fistula in this cohort. Brachial artery flow is a reasonable measure of Qa in comparison with indicator dilution.

Color Doppler ultrasonography percutaneous transluminal angioplasty of vascular access grafts.

Percutaneous transluminal angioplasty (PTA) is a possible treatment for stenosis. This study aimed to verify the impact of a vascular access (VA) surveillance protocol, based on the detection of functional changes and their correction by a new PTA method for VA performed under color Doppler ultrasonography (CDU) guidance. We divided the patients into two groups: group A, before May 1999 (retrospective study) without the surveillance protocol, and group B, from 1 May 1999 to January 2001 (prospective study) with the surveillance protocol. Access blood flow (Qa) was assessed every 4 weeks by ultrasound velocity dilution. In cases of a reduction of >or=35% from the baseline value, VA was examined using CDU: if a stenosis >50% was detected, angioplasty was performed. In cases of Qa reduction <35% we continued monitoring. By Coxs multivariate analyses, only the use of PTA with or without stenting reduced the relative risk of thrombosis by 64% during the follow-up (p=0.017 confidence intervals 88%-15%) in group B patients. Secondary patency was 80% for VA in which we performed PTA with or without stenting at 18 months, and 58% at 18 months in which we did not perform PTA. Our data show how PTA under CDU is useful to maintain and to improve graft patency. This PTA under CDU guidance allows patients to avoid surgical intervention, hospitalization, and adverse reactions to contrast media and exposure to ionizing radiation, with reduced cost and with better graft survival.

The Vascular Access Team

In recent years, the need for the vascular access surveillance has been growing steadily. In our dialysis department, a dedicated multidisciplinary team is active since 10 years. The Team is compos...

Surveillance of Hemodialysis Vascular Access with Temperature Biosensor Combined with Doppler-Ultrasound to Prevent Vascular Failure

Regular surveillance and pre-emptive correction of subclinical stenosis have been shown to be useful procedures for reducing the rate of vascular access (VA) failure. Blood flow (Qa) measurement is considered the best procedure for VA surveillance. Qa below 500 ml/min or reductions over 25% from preceding Qa measurements are predictors of VA thrombosis.

Echo color Doppler ultrasound: a valuable diagnostic tool in the assessment of arteriovenous fistula in hemodialysis patients.

A functioning vascular access is a critical requirement to improve the quality of life in hemodialysis patients, so monitoring and surveillance of vascular access play key roles in identifying all dysfunctions and reducing the huge economic cost as well as adequacy of dialysis.In our five-year experience, a study protocol has been used and improved with the help of ultrasonography.Doppler ultrasound is an excellent and sensitive modality for hemodialysis access evaluation, one of techniques employed for arteriovenous fistulae (AVF) study, not only as a preoperative tool, but also in post-operative monitoring of AVF maturation. In addition, the current guidelines recommend AVF surveillance by access blood flow measurement and the correction of hemodynamic stenosis in order to prolong access survival. Doppler ultrasound is readily available, directly used by nephrologists, non-invasive, safe, inexpensive, reproducible, although it requires more clinical skill and time to perform and proper equipment. Ultrasonography imaging can substantially reduce the number of subsequent invasive angiographic procedures. In our opinion, Doppler ultrasound should have a crucial place in the interdisciplinary cooperation in AVF monitoring and it should be included as part of an integrated vascular access management program.

Team per l'allestimento degli accessi vascolari: la nostra esperienza

Abstract non disponibile

Team for Vascular Access: Our Experience

In recent years, in the Dialysis departments, the need of a team for the construction and the surveillance of vascular access begins to appear. In this article we describe our experience.

Doppler ultrasound and calcification score: improving vascular access surveillance

Aim: Vascular access (VA) dysfunction limits hemodialysis delivery, which increases morbidity and mortality. The most com mon cause of VA failure is thrombosis, due to flow limiting stenosis resulting from neointimal hyperplasia. This occurs not only due to hemodynamic factors but also by systemic ones related to vascular atherosclerosis, inflammation and calcification, which has developed a simple vascular calcification score (SVCS) predictor of vascular calcification and arterial stiffness. The NKF-K/DOQ recommends several diagnostic procedures for VA surveillance. Blood access flow (Qa) has predictive power for the detection of stenosis. Our aim was to evaluate the role of systemic factors, especially SCVS, on Qa. Material and methods: Transversal study in 50 patients. Qa value was obtained with Blood Temperature Monitor and Doppler method. Pearson coefficient evaluated correlation between them. Clinical, lab and radiological variables were recorded and non-parametric tests evaluated how both Qa varied with them. Results: Pearson’s corelation between DU-Qa and TD-Qa was 0.851 (p-value <0.001). DU-Qa varied significantly with age (p = 0.012), VA type (p = 0.021), SCVS (p = 0.030), intra-access arterial pressure (p = 0.015) and time on dialysis (p = 0.002). BTM-Qa varied significantly with diabetes status (p = 0.027), age (p = 0.017), first VA status (p = 0.036), intra-access arterial pressure (p = 0.028) and dialysis time (p = 0.001). Nevertheless, gender, hypertensive status and analitical parameters did not change the flow values. Conclusion: Higher SVCS was associated only with lower DU-Qas, giving this method an advantage towards the indirect one. Additionally, a simple method like SVCS may be used to guide new surveillance recommendations accordingly to risk stratification.

Doppler ultrasound: a powerful tool for vascular access surveillance.

National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) guidelines recommend Doppler ultrasound (DU) for surveillance of vascular access (VA), but trials have not been unanimous about its benefit on VA patency. The aim of this study was to evaluate the accuracy of DU for patency, as well as to highlight additional data provided by this method. A transversal study was conducted to evaluate DU method in correlation with BTM using paired t-test and Pearson test. Ultrasonography evaluation was performed with a Siemens Acuson X150 Ultrasound device and BTM-Qa with the Blood Temperature Monitor BTM(®). Access blood flow (Qa) values were correlated with several factors by nonparametric tests. Fifty hemodialysis patients were included, with mean age of 64.5 ± 13.7 years; durations of hemodialysis and VA were 51.4 ± 47.3 and 47.6 ± 42.1 months, respectively. The mean difference between DU and BTM flows was 20.5 ml/minute (p 0.624). Pearson correlation was 0.851 (p < 0.001). DU-Qa values varied significantly with several factors: type of VA, reason for DU referral, the presence of artery stenosis, and the location and number of stenosis. BTM-Qa values only varied significantly with the presence and number of stenosis. Various silent abnormalities were detected with DU. DU provides accurate anatomic and hemodynamic data to further knowledge regarding the etiology of stenosis and other abnormalities that compromise VA well functioning.

Monitoring and Surveillance of Hemodialysis Vascular Access Using StenTec and Physical Exam.

Hemodialysis vascular access surveillance for hemodynamically significant stenosis can be a challenge because no universal gold standard exists. The StenTec Gauge measures static intra-access peak pressure and graphically displays the ratio of this pressure to systemic systolic (peak) arterial pressure (PIA ratio). In combination with careful physical exam (PE), the StenTec Gauge is an acceptable and cost-effective way of detecting hemodynamically significant stenosis in arteriovenous fistulas (AVF) or grafts (AVG). In a selected population of 21 hemodialysis patients with mature arteriovenous access, a StenTec reading and physical examination was measured on a weekly basis. Interventional procedures for suspected access dysfunction were performed if there was a greater than 25% increase of the PIA ratio from baseline in two consecutive readings, along with correlating clinical suspicion from physical examination findings. StenTec independently had a sensitivity of 56% and a specificity of 99% in detecting clinically significant stenosis. PE alone had a sensitivity of 89% and a specificity of 100%. StenTec combined with PE had a sensitivity of 100% and a specificity of 99% for predicting hemodynamically significant stenosis. StenTec detected 4 of 10 patients who had a PIA ratio value of ≥0.5, which correlates with current National Kidney Foundation Disease Outcomes Quality Initiative (KDOQI) criteria for mean intra-access pressure ratios indicating a clinically significant outflow stenosis. PE predicted 9 of 10 patients with stenosis, and the combination of StenTec and PE predicted all 10 patients with clinically significant stenosis using the KDOQI criteria for PIA ratio. Hemodynamically significant access stenosis can be detected with excellent accuracy using both StenTec and PE measurements combined for monitoring and surveillance methods.

The key role of color Doppler ultrasound in the work-up of hemodialysis vascular access.

Vascular access (VA) is the lifeline for the hemodialysis patient and the native arterio-venous fistula (AVF) is the first-choice access. Among the different tests used in the VA domain, color Doppler ultrasound (CD-US) plays a key role in the clinical work-up. At the present time, three are the main fields of CD-US application: (i) evaluation of forearm arteries and veins in surgical planning; (ii) testing of AVF maturation; (iii) VA complications. Specifically, during the AVF maturation, CD-US allows to measure the diameter and flow volume in the brachial artery and calculate the peak systolic velocity (PSV) of the arterial axis, anastomosis and efferent vein, to detect critical stenosis. The borderline stenosis, revealed by the discrepancies between access flow rate and PSV, should be followed up with subsequent tests to detect progression of stenosis; the cases with significant changes in brachial flow should be referred to angiography. In conclusion, clinical monitoring remains the backbone of any VA program. CD-US is of utmost importance in a patient-centered VA evaluation, because it allows the appropriate management of all aspects of VA care. These are the main reasons why we strongly advocate the adoption of a VA surveillance program based on CD-US.

Vascular Access Surveillance: Current Concepts

Konstantinos Leivaditis and Vassilios Liakopoulos* 1st Department of Internal Medicine, Division of Nephrology and Hypertension, AHEPA Hospital, School of Medicine, Aristotle University of Thessaloniki, Greece *Corresponding author: Vassilios Liakopoulos, Assistant Professor of Nephrology, Division of Nephrology and Hypertension, 1st Department of Internal Medicine, AHEPA Hospital, School of Medicine, Aristotle University of Thessaloniki, 1, St. Kyriakidi street, 54636, Thessaloniki, Greece, Tel: +302310994694; E-mail: liakopul@otenet.gr

Vascular access for hemodialysis: postoperative evaluation and function monitoring

Vascular access (VA) survival is a crucial issue associated with morbidity and mortality of patients undergoing maintenance hemodialysis. The development of stenosis is the major factor that leads to VA failure. Strategies for early detection of lesions within a VA system before serious complications arise are therefore crucial. The implementation of a VA surveillance program could lead to timely detection of VA dysfunction and referral for correction, reduction in central venous catheter use and decrease in hospitalization and VA-related cost. Suggested methods for arteriovenous fistulae and grafts surveillance include blood flow measurement, static pressure evaluation and duplex ultrasonography. Physical examination is an accepted method in contrast to nonstandardized dynamic pressure measurement for grafts. Access recirculation (not urea based) and dynamic pressure measurements are accepted methods for fistulae. Decreasing URR or Kt/V (otherwise unexplained) and increased (negative) arterial pressure in the dialysis machine are methods of limited sensitivity and specificity for both fistulae and grafts. Measurement of access blood flow has been proposed as the gold standard for the screening of all types of VA. Access flow can be measured by various techniques which are direct or indirect. Several studies about VA surveillance programs have demonstrated conflicting results. Larger, randomized controlled trials need to be carried out in order to clarify whether surveillance programs are necessary and which is the best surveillance strategy for each type of VA.

Vascular Access Surveillance: Time to End the Controversy

AbstractThe establishment and maintenance of permanent vascular access for hemodialysis patients are important clinical problems. Vascular access surveillance, currently mandated by the CMS, refers to the task of identifying and correcting an underlying vascular access stenosis to prolong vascular access patency and survival. While this premise makes intuitive sense, this article discusses the underlying evidence to support it, outlining disparate conclusions of clinical practice guidelines and a recent commentary by experts in vascular access.