Postoperative Assessment of Vascular Access

The "Rule of 4" ultrasound diagnostic criteria at 6 weeks postoperatively was more appropriate for clinical determination of arteriovenous fistula maturation

OBJECTIVE

The aim of this study was to investigate the timing of assessing the maturation of arteriovenous fistula (AVF) and the diagnostic efficacy of two ultrasound assessment criteria in determining the maturation of AVF.

METHODS

We collected clinical data on 227 patients with end-stage renal disease who were first diagnosed at our institution between February 1, 2023 and February 1, 2024, and were followed up regularly for 12 weeks post-AVF creation, with the diameter of the draining vein and the brachial artery volume flow (VF) recorded at 1 day, 2, 4, 6, 8, 10, and 12 weeks post-operation. We focused on the time of AVF maturation, and ultrasonographic diagnostic criteria 1 (the vein diameter was ≥4 mm, and the brachial artery VF was >500 mL/min, referred to as the "Rule of 4") and ultrasonographic diagnostic criteria 2 (the vein diameter was ≥5 mm, and the brachial artery VF was> 500 mL/min, referred to as the "Rule of 5") were used to evaluate the maturation of AVF. And compared with clinically maturation criteria to understand the correlation, consistency, and diagnostic efficacy.

RESULTS

1. The venous diameter and brachial artery VF of AVF showed an upward trend, and increased significantly in 1 day to 6 weeks postoperatively (p < .05),especially between 1 day and 2 weeks, while no significant difference in the increases at 6-12 weeks; 2. Logistic regression analysis showed that venous diameter (OR = 19.589 , 95% CI 1.560-245.979, p = .021) and brachial artery VF (OR = 1.024 , 95% CI 1.005-1.042, p = .011) at 6 weeks were the independent correlates affecting AVF maturation; and the optimal thresholds were 4.08 mm (sensitivity 88.10%, specificity 70.00%) and 472.50 mL/min (sensitivity 93.20%, specificity 84.00%), respectively; 3. Compared with clinical maturation, the two ultrasonographic diagnostic criteria at 6 weeks postoperatively were correlated with clinical maturation, and the specificity of both was 100%, with "Rule of 4" having a sensitivity of 79.66%, an accuracy of 84.14%, and a concordance kappa = 0.633, while "Rule of 5″ had a sensitivity of 31.63%, an accuracy of 46.69%, and a concordance kappa = 0.169; and the area under the ROC curve (AUC) for "Rule of 4″ was higher than that for "Rule of 5" (0.898 vs. 0.658, p < .001).

CONCLUSION

Six weeks postoperatively may be the best timing for an ultrasound assessment of AVF maturation, and the "Rule of 4" ultrasound assessment criteria was more suitable for clinical judgment of AVF maturation.

The Role of Cardio-Renal Inflammation in Deciding the Fate of the Arteriovenous Fistula in Haemodialysis Therapy

Vascular access is an indispensable component of haemodialysis therapy for end-stage kidney disease patients. The arteriovenous fistula (AVF) is most common, but importantly, two-year failure rates are greater than fifty percent. AVF failure can occur due to a lack of suitable vascular remodelling, and inappropriate inflammation preventing maturation, or alternatively neointimal hyperplasia and vascular stenosis preventing long-term use. A comprehensive mechanistic understanding of these processes is still lacking, but recent studies highlight an essential role for inflammation from uraemia and the AVF itself. Inflammation affects each cell in the cascade of AVF failure, the endothelium, the infiltrating immune cells, and the vascular smooth muscle cells. This review examines the role of inflammation in each cell step by step and the influence on AVF failure. Inflammation resulting in AVF failure occurs initially via changes in endothelial cell activation, permeability, and vasoprotective chemokine secretion. Resultingly, immune cells can extravasate into the subendothelial space to release inflammatory cytokines and cause other deleterious changes to the microenvironment. Finally, all these changes modify vascular smooth muscle cell function, resulting in excessive and unchecked hyperplasia and proliferation, eventually leading to stenosis and the failure of the AVF. Finally, the emerging therapeutic options based off these findings are discussed, including mesenchymal stem cells, small-molecule inhibitors, and far-infrared therapies. Recent years have clearly demonstrated a vital role for inflammation in deciding the fate of the AVF, and future works must be centred on this to develop therapies for a hitherto unacceptably underserved patient population.

Accuracy of physical examination versus Doppler ultrasonography for determining maturity in postoperative arteriovenous fistula formation

BACKGROUND

Differentiating between arteriovenous fistula (AVF) maturation and failure can help determine which AVF will undergo successful canulation and which ones will require immediate rescue.

METHODS

A prospective observational study was conducted at Vajira Hospital in Bangkok, Thailand, between October 2020-November 2022. A single vascular surgeon performed a physical examination on patients with chronic kidney disease undergoing AVF placement, and a radiologist conducted Doppler ultrasonography during the second and sixth postoperative weeks. Dialysis nurses determined AVF maturity by performing cannulation. The study compared the accuracy of physical examination and Doppler ultrasonography. A model was developed to predict the success of AVF use.

RESULTS

Out Of the 125 recruited patients, 81% demonstrate unassisted maturation of their AVF. The male sex and brachiocephalic type are associated with AVF maturation. The physical examination findings of palpable thrill and the absence of a strong pulse at the 6th week show an area under the receiver operating curve (AUC) value of 0.79. Similarly, arterial end-diastolic velocity on ultrasonography at the 6th week also demonstrates a comparable predictive value with an AUC of 0.82 (p = 0.697). Meanwhile, the model that combined end-diastolic velocity and venous volume flow yields the best results for predicting AVF maturation, with an AUC of 0.92. These models provide more accurate predictions compared to physical examination alone (AUC: 0.92 vs. 0.79; p < 0.01).

CONCLUSION

Although a prudent physician predicts AVF maturation through a thorough physical examination, Doppler ultrasonography is preferred in anticipating the success of postoperative AVF placement.

Current role of ultrasound in hemodialysis access evaluation

Physical examination (PE) is considered the backbone before vascular access (VA) placement, during maturation period and for follow-up. However, it may be inadequate in identifying suitable vasculature, mainly in comorbid patients, or in detecting complications. This review highlights the advantages of ultrasound imaging to manage VA before placement, during maturation and follow-up. Furthermore, it analyses the future perspectives in evaluating early and late VA complications thank to the availability of multiparametric platforms, point of care of ultrasound, and portable/wireless systems. Technical improvements and low-cost systems should favor the widespread ultrasound-based VA surveillance programs. This significant turning point needs an adequate training of nephrologists and dialysis nurses and the standardization of exams, parameters, and procedures.

Postoperative Day 1 Access Blood Flow and Resistive Index can Predict Patency in Distal Forearm Arteriovenous Fistula

Introduction

Early access failure is an important complication of autogenous arteriovenous fistulas (AVFs). We prospectively monitored patients who underwent AVF creation using ultrasonography.

Methods

Color flow imaging was used to assess access blood flow in patients undergoing creation of a new AVF in the distal forearm preoperatively and at 1 day and 1 week postoperatively. We measured the flow volume (FV) and resistive index (RI) of the brachial artery, and the internal diameter of the brachial artery and outflow vein. The primary outcome was the primary patency of the AVF without percutaneous angioplasty (PTA) or surgical revision 40 days after access creation.

Results

We recruited 35 patients with newly created AVFs (men, 21; mean age, 73 years). Within one day of operation, the overall FV increased from 62 to 352 mL/min (p<0.0001) while the overall RI decreased from 1.0 to 0.63 (p<0.001). Five patients required PTA or surgical revision (intervention group [IG]), whereas 30 patients did not (non-intervention group [NIG]). The FV increased while the RI decreased from day 1 to week 1 in the NIG, but not in the IG (p<0.0001). The diameter of the brachial artery and outflow vein significantly increased in the NIG at 1 week. The FV of 235 mL/min and RI of 0.63 at 1 day were the thresholds for predicting early fistula failure.

Conclusions

Access FV and RI at 1 day after AVF creation can predict primary patency and help plan intervention.

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 pre-operative 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.

Performance of physical examination versus ultrasonography to detect stenosis in haemodialysis arteriovenous fistula

Purpose

The overall purpose of this study is to compare the accuracy of physical examination (PE) versus ultrasonography (US) in people with arteriovenous fistula (AVF).

Methods

This is a cross-sectional study with a total of 99 patients attended by the vascular radiology unit for AVF evaluation during January - March 2015. PE and ultrasonography were blinded performed by different radiologists. For complete and individual signs of PE, sensitivity, specificity, predictive positive (PPV) and negative (PNV) value, likelihood ratios (LR) and Cohen's κ value were measured.

Results

According to ultrasonography, the presence of stenosis was identified in 57 (58%) patients, and 61 (62%) by PE. The accuracy of PE for the diagnosis of AVF was sensitivity 82%, specificity 67%, PPV 77%, NPV 74%, LR 2.74 and 0.26. There was a moderate agreement beyond chance between PE and ultrasonography (κ = 0.5).

Conclusions

PE has shown a moderate accuracy to detect stenosis. With non-ultrasonography availability Haemodialysis Units can get benefit to optimize VA survival and professionals should improve its basic skills.

Importance of monitoring and treatment of failed maturation in radiocephalic arteriovenous fistula in predialysis: Role of ultrasound

The aim of the study was to analyse outcomes of AVF-RC in predialysis stage in which a clinical and radiological follow up of its maturation had been done and primary failure had been treated.

MATERIAL AND METHODS

We studied 127 RC-AVF in 117 predialysis patients. All cases had a preoperative map. The RC-AVF was considered mature if it had a brachial artery flow ≥500ml/min and a cephalic vein diameter of ≥4mm. Primary failure was treated radiologically or surgically depending on the type of lesion. Fifty-eight patients started dialysis at the time of the study.

RESULTS

In 106 RC-AVF without thrombosis, 72 (68%) were mature and 34 (32%) were immature. A total of 97% of the immature had at least one lesion, and the most common site was the post-anastomotic vein. Lesions were found in 31% of mature RC-AVF, and 18% of patients required treatment. Radiological treatment was the most frequent for maturation failure. After 6 months, primary and secondary patency were 59% and 78%, while after 12 months they were 48% and 77%, respectively. The 80% of patients started dialysis with a distal AVF (76% RC-AVF and 4% ulnar basilic). None of the patients with treated immature RC-AVF started dialysis with CVC, while 78% of the patients started with said AVF.

CONCLUSION

Ultrasonography for monitoring maturation provides advantages over clinical monitoring. With our management of RC-AVF in predialysis, 80% of patients start dialysis with an adequate distal AVF.

Vascular access Creation and Care Should be Provided by Nephrologists

The long-term survival and quality of life of patients on hemodialysis is dependent on the adequacy of dialysis via an appropriately placed vascular access. Recent clinical practice guidelines recommend the creation of native arteriovenous fistula or synthetic graft before start of chronic hemodialysis therapy to prevent the need for complication-prone dialysis catheters. The direct involvement of nephrologists in the management of referral patterns, predialysis follow-up, policy of venous preservation, pre-operative evaluation, vascular access surgery and vascular access care seems to be important and productive targets for the quality of care delivered to the patients with end-stage renal disease. Early referral to nephrologists is important for delay progression of both kidney disease and its complications by specific and adequate treatment, for education program which should include modification of lifestyle, medication management, selection of treatment modality and instruction for vein preservation and vascular access. Nephrologists are responsible for on-time placement and adequate maturation of vascular access. The number of nephrologists around the world who create their own fistulas and grafts is growing, driven by a need for better patient outcomes on hemodialysis. Nephrologists have also a key role for care of vascular access during hemodialysis treatment by following vascular access function using clinical data, physical examination and additional ultrasound evaluation. Timely detection of malfunctioning vascular access means timely surgical or radiological intervention and increases the survival of vascular access.

Organisation of a Radiological Vascular access Unit

An interventional vascular access unit is usually part of an interdisciplinary centre, including departments of nephrology, vascular surgery, angiology and interventional radiology. We present recommendations on quality control, equipment and diagnostic and interventional techniques for the treatment of vascular access insufficiency.

Standard Procedures of Endovascular Treatment for Vascular Access Stenosis in our Facility – Clinical Usefulness of Ultrasonography

In Japan, the number of patients receiving dialysis is 314,180 at the end of 2013 and 97% are treated with hemodialysis. And the mean age of patients and the percentage of diabetes have been increasing. For this reason, preparations of a new vascular access (VA) and its long-term maintenance have become difficult. In the guidelines by the Japanese Society for Dialysis Therapy (JSDT), endovascular treatment (ET) is positioned as the first line for VA stenosis. The procedure of ET itself is very simple. The revision of Japanese health insurance set an expensive technical fee for ET in 2012. It also added a restriction by which the claims for both technical and material fees would be denied, if the treatment was performed within 3 months after a previous treatment. This makes determination of best treatment timing more important. The functional evaluation using ultrasonography (US) is a useful monitoring index for determination of the ET timing for patients with stenosis. We investigated the cumulative relative frequency of flow volume (FV) and resistant index (RI) of brachial artery in arteriovenous graft (AVG) and arteriovenous fistula (AVF) cases with access failures. As a result, the cut-off values of FV and RI in AVG were 480 mL/min and 0.57, and in AVF were 354 mL/min and 0.61, respectively. Therefore we determine the treatment timing based on these results. Since 2012, active monitoring using US could have decreased the number of treatment patients by 100 per year. This meant that objective evaluation by US enabled treatments at a more suitable time to promote the proper use of medical expenses for EV treatment.

Proactive Surveillance Approach to Guarantee a Functional Arteriovenous Fistula at First Dialysis is Worth

Purpose

To evaluate the impact of a proactive surveillance program on functional access rate at the time of first dialysis.

Methods

In January 2010, a proactive surveillance program to intercept failures to mature was set up at the University Hospitals Leuven. Patients receiving an arteriovenous fistula (AVF) for pre-dialysis end-stage renal disease between January 2010 and May 2013 were retrospectively analyzed. The primary end-point was a functional AVF at first dialysis. Also, AVF- associated complications and reinterventions were analyzed. Furthermore, primary, assisted primary and secondary patency rates were estimated using Kaplan-Meier survival curves.

Results

One hundred sixty-four patients were included in the study. Patients were followed until first dialysis. Median follow-up time was 287 days (interquartile range, 108-551 days). During follow-up, 40 patients (24.4%) needed one or more additional interventions, resulting in 60 reinterventions. Ten patients needed dialysis within the minimal accepted maturation period of the AVF (4 weeks). Of the 154 patients who could await the maturation period of the AVF, 145 (94.2%) appeared ready for use at the time of dialysis or at the end of the study period. In 34 of them (22%), this was thanks to one or more interventions during follow-up.

Conclusions

A dedicated surveillance program of patients with AVFs in the pre-dialysis stadium detects failure to mature. Close coaching and proactive intervention can aid the patient in his own “fistula first” project.

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.