A Multicenter Randomized Clinical Trial of Hemodialysis Access Blood Flow Surveillance Compared to Standard of Care: The Hemodialysis Access Surveillance Evaluation (HASE) Study

Rapid intervention team strategy improves intervention quality for patients undergoing hemodialysis with arteriovenous shunt dysfunction or failure

BACKGROUND

Vascular access dysfunction is a great burden for hemodialysis patients. Early intervention of a dysfunctional arteriovenous shunt is associated with higher technical success and may improve midterm patency. This trial aimed to estimate the feasibility of a new system, the "rapid intervention team" (RIT) strategy.

METHODS

We recruited hemodialysis patients who visited our hospital because of arteriovenous shunt dysfunction or failure to undergo an RIT strategy from September 1, 2019 to December 31, 2022. In addition, we included a control group comprising patients who underwent percutaneous intervention for arteriovenous shunt dysfunction or failure before this strategy was implemented from February 1, 2017 to December 31, 2022. Case number, time to intervention, all-cause mortality, cumulative survival rate, and number of patients who required temporary dialysis catheter insertion and recreation were compared between the two groups. The primary endpoints were double-lumen insertion, a composite outcome involving permanent catheter insertion, and the need for recreation. The secondary endpoint was all-cause mortality.

RESULTS

We enrolled 1054 patients, including 544 (51.6%) and 510 (48.4%) in the RIT and control groups, respectively. Even with the coronavirus disease of 2019 (COVID-19) pandemic, the number of cases significantly increased after the implementation of the RIT strategy (from 216 in 2019 to 828 in 2022, p for trend <0.001). The RIT group had a shortened time to intervention ( p for trend <0.001). The implementation of the RIT strategy was significantly associated with a reduced risk of insertion of a temporary double-lumen catheter and recreation of vascular access (1% vs 6% and 1% vs 28%, respectively; both p < 0.01). The cumulative survival rate was not significantly different between the RIT and control groups ( p = 0.16).

CONCLUSION

The implementation of the RIT strategy improves the quantity and quality of percutaneous transluminal intervention for arteriovenous shunt dysfunction or failure in patients undergoing hemodialysis.

Hemodialysis vascular access flow measurements by the novel DMed NephroFlow® device: A comparative study with Transonic®

INTRODUCTION

The current Spanish Clinical Guidelines on Vascular Access for Hemodialysis support the need for surveillance and monitoring of vascular access (VA) to avoid complications. Ultrasound dilution (UD) methods are accepted for the evaluation of VA flow and Transonic® has established the gold standard method for the measurement. The DMed NephroFlow (NIPRO®) device, based on UD method has recently been incorporated. We report a comparative study between the classic Transonic® versus the new NephroFlow® device.

MATERIAL AND METHODS

For two consecutive months, measurements of VA flow using both referred systems were performed in patients with a native arteriovenous fistula (AVF) or a graft (AVG) on hemodialysis (HD) in our unit. Both studies were undertaken according to the usual recommendations: VA flow of 250 ml/min, ultrafiltration rate without modifications, both needles in the same vein, and always in the first hour of the HD session.

RESULTS

Forty-five patients were included: 17 women and 28 men, mean age of 67 ± 12 years. Thirty patients were diabetic. The baseline meantime on HD was 51 ± 39 months (range: 3-163). Type of VA was: 17 patients radio-cephalic AVF, 17 brachiocephalic AVF, 7 brachiobasilic AVF, and 3 with a graft. The mean flow estimated by the Transonic® was 1222 ± 805 ml/min and the estimated flow by the NephroFlow® device was 1252 ± 975 ml/min. Good reliability between Transonic® and NephroFlow® was observed, with a reliability index of Cronbach's Alpha of 0.927 and an Intraclass Correlation Index of 0.928.

CONCLUSIONS

The NephroFlow® device seems comparable with the accepted gold standard UD method for estimating VA flow. More studies must be performed to verify these results. However, they should be considered for the surveillance and monitoring of VA flow, in agreement with the Spanish Guidelines.

Successful Removal of a Fractured Desilets-Hoffman Sheath in a Patient With a Loop Arteriovenous Graft: Balloon-Supported Retrieval Technique

INTRODUCTION

While a Desilets-Hoffman sheath rarely fractures, when it does, the presence of an intravenous foreign body can cause various complications.

CASE PRESENTATION

A 74-year-old woman receiving hemodialysis for end-stage renal disease via a left forearm arteriovenous graft (AVG) was referred to the interventional radiology department following thrombotic occlusion of the AVG. A corrective procedure was initiated, and the 7F Desilets-Hoffman sheath fractured after the purse-string suture. A .035-inch guidewire was passed through the fractured sheath, and a 3.0-mm x 60-mm balloon catheter was inflated, allowing for the successful removal of the sheath fragment without complications.

CONCLUSION

The fractured Desilets-Hoffman sheath was successfully removed in a patient with a loop arteriovenous graft using balloon-supported retrieval technique.

Integrating vascular access surveillance with clinical monitoring for stenosis prediction

BACKGROUND

Arteriovenous fistula and arteriovenous graft are the most common types of vascular access for dialysis; stenosis and thrombosis are major complications leading to access failure and to an incresed risk of mortality. The aim of the present study was to assess the results of integrating  strict vascular access blood flow surveillance with routine clinical monitoring for predicting vascular access stenosis in chronic hemodialysis patients.

METHODS

In this retrospective study, chronic dialysis patients with arteriovenous fistula or arteriovenous graft were included from a setting in which all patients underwent quarterly blood flow surveillance in 2017. The results of blood flow surveillance were confirmed by thorough physical examination. Predictive performance of blood flow surveillance models in detecting stenosis in patients with arteriovenous fistula or arteriovenous graft was evaluated. The predictive performance of the quarterly blood flow surveillance model was described by confusion matrix. Differences in accuracy, positive predictive value (PPV), and negative predictive value (NPV) between blood flow surveillance models with distinct blood flow thresholds were evaluated.

RESULTS

Of 397 included patients, 336 had an arteriovenous fistula and 61 had an arteriovenous graft. In 2017, 106 percutaneous transluminal angioplasty procedures were performed in patients with an arteriovenous fistula, and 63 in patients with an arteriovenous graft. The results revealed similar predictive performance of surveillance models using an absolute blood flow threshold of < 500 or < 400 mL/min in predicting stenosis in patients with arteriovenous fistula. Blood flow surveillance models for patients with an arteriovenous fistula had significantly higher accuracy than those for patients with an arteriovenous graft. Furthermore, the use of a relative threshold, defined as blood flow < 1000 mL/min and a 25% decline in blood flow, did not affect the predictive performance of blood flow surveillance models.

CONCLUSION

Blood flow surveillance models using thresholds of < 400 and < 600 mL/min, followed by thorough physical examination, showed an accuracy of 91.54% and 72.15% in predicting stenosis in patients with arteriovenous fistula and arteriovenous graft, respectively. These two blood flow surveillance models may be integrated with routine clinical monitoring to improve early detection and treatment of stenosis in hemodialysis patients.

FLOW: Flow dysfunction of hemodialysis vascular access: A randomized controlled trial on the effectiveness of surveillance of arteriovenous fistulas and grafts

INTRODUCTION

It is assumed that identification and correction of asymptomatic stenoses in the vascular access circuit will prevent thrombosis that would require urgent intervention to continue hemodialysis treatment. However, the evidence base for this assumption is limited. Recent international clinical practice guidelines reach different conclusions on the use of surveillance for vascular access flow dysfunction and recommend further research to inform clinical practice.

METHODS

The FLOW trial is a double-blind, multicenter, randomized controlled trial with a 1:1 individual participant treatment allocation ratio over two study arms. In the intervention group, only symptomatic vascular access stenoses detected by clinical monitoring are treated, whereas in the comparison group asymptomatic stenoses detected by surveillance using monthly dilution flow measurements are treated as well. Hemodialysis patients with a functional arteriovenous vascular access are enrolled. The primary outcome is the access-related intervention rate that will be analyzed using a general linear model with Poisson distribution. Secondary outcomes include patient satisfaction, access-related serious adverse events, and quality of the surveillance process. A cost effectiveness analysis and budget impact analysis will also be conducted. The study requires 828 patient-years of follow-up in 417 participants to detect a difference of 0.25 access-related interventions per year between study groups.

DISCUSSION

As one of the largest randomized controlled trials assessing the clinical impact of vascular access surveillance using a strong double-blinded study design, we believe the FLOW trial will provide much-needed evidence to improve vascular access care for hemodialysis patients.

Practice of dialysis access interventional nephrology procedures in the Asia-Pacific region: Getting lay of the land

AIM

This cross-sectional survey aimed to determine the prevalence of Interventional Nephrology (IN) practice amongst nephrologists in the Asia-Pacific Region (APR), specifically related to dialysis access (DA).

METHODS

The Association of VA and intervenTionAl Renal physicians (AVATAR) Foundation from India conducted a multinational online survey amongst nephrologists from the Asia-Pacific to determine the practice of IN in the planning, creation, and management of dialysis access. The treatment modalities, manpower and equipment availability, monthly cost of treatment, specifics of dialysis access interventions, and challenges in the training and practice of IN by nephrologists were included in the survey.

RESULTS

Twenty-one countries from the APR participated in the survey. Nephrologists from 18 (85.7%) countries reported performing at least one of the basic dialysis access-related IN procedures, primarily the placement of non-tunnelled central catheters (n-TCC; 71.5%). Only 10 countries (47.6%) reported having an average of <4% of nephrologists performing any of the advanced IN access procedures, the most common being the placement of a peritoneal dialysis (PD) catheter (20%). Lack of formal training (57.14%), time (42.8%), incentive (38%), institutional support (38%), medico-legal protection (28.6%), and prohibitive cost (23.8%) were the main challenges to practice IN. The primary obstacles to implementing the IN training were a lack of funding and skilled personnel.

CONCLUSION

The practice of dialysis access-related IN in APR is inadequate, mostly due to a lack of training, backup support, and economic constraints, whereas training in access-related IN is constrained by a lack of a skilled workforce and finances.

Screening and surveillance of venous stenosis in AVG: Is it time to rethink our assumptions?

Guidelines make no firm recommendations about surveillance of arteriovenous grafts as several randomised trials (RCT) have not shown a clear benefit in patency. However a more thorough review of these RCT based on epidemiological principles reveals significant limitations. In particular a key weakness of these older studies is the interventions performed for venous stenosis detected that was largely angioplasty. However, the observational data of modern stent-grafts shows a clear benefit over angioplasty, and thus seems to suggest that a modern well considered RCT is now mandated.

Manual compression technique improves the success rate in the treatment of thrombosed aneurysmal arteriovenous fistula: A single-center experience

OBJECTIVE

Endovascular intervention for thrombosed aneurysmal arteriovenous fistula (AVF) is still a challenge. Manual compression technique (MCT)-assisted angioplasty may be helpful, but there is no evidence or data to support it.

METHODS

From January 2018 to May 2021, patients with thrombosed aneurysmal AVFs were retrospectively enrolled. The patients were separated into the MCT group or the traditional group according to the procedure received. Technical failure, clinical failure, 90-day patency, and safety were analyzed.

RESULTS

A total of 159 cases (64 ± 12 years old, 60% male) were enrolled, of which 87 cases received MCT and 72 underwent traditional angioplasty. No technical failure was observed in the MCT group, while five technical failures were observed in the traditional group (0% vs. 7%, p = 0.02). There were no differences in the clinical failure rate (3% vs. 7%, p = 0.30), 90-day patency rate, or procedure time between the MCT group and the traditional group. There was no symptomatic pulmonary embolism or other complication in the two groups.

CONCLUSION

MCT is a low-cost, less invasive, and safe procedure for thrombosed aneurysmal AVF, and it achieves a higher technical success rate than traditional angioplasty.

Osteopontin is a key regulator of vascular smooth muscle cell proliferation in the outflow vein of arteriovenous fistulas

OBJECTIVES

Despite advances in the maintenance of arteriovenous fistulas (AVFs), the patency rates remain suboptimal. Most AVFs fail due to outflow vein stenosis; however, the underlying mechanism of AVF stenosis remains unclear. The present study aimed to identify key factors associated with AVF outflow stenosis.

METHODS

We obtained gene expression profiling data for the outflow vein of AVF from three Gene Expression Omnibus database datasets (GSE39488, GSE97377, and GSE116268) and analyzed the common differentially expressed genes (DEGs). We evaluated a common DEG in an aortocaval mouse model and the stenotic outflow veins of AVFs collected from patients. Furthermore, we isolated vascular smooth muscle cells (VSMCs) from the inferior vena cava (IVC) of wild-type (WT) and osteopontin (Opn)-knockout (KO) mice and assessed the proliferation of VSMCs following stimulation with platelet-derived growth factors (PDGFs).

RESULTS

OPN was the only common upregulated DEG among all datasets. OPN was expressed in the medial layer of the outflow vein of AVF in aortocaval mouse models and co-stained with the VSMC marker (α-smooth muscle actin). OPN expression was markedly increased in the VSMCs of stenotic outflow veins of AVF collected from patients undergoing hemodialysis compared to presurgical veins acquired during AVF formation surgery. PDGF-induced VSMC proliferation was significantly increased in the VSMCs isolated from the IVC of WT mice but not in those isolated from the IVC of Opn-KO mice.

CONCLUSIONS

OPN may be a key gene involved in VSMC proliferation in the AVF outflow veins and a therapeutic target to improve the AVF patency rate.

Thrombectomy approach for access maintenance in the end stage renal disease population: a narrative review

Objective

This article reviews current practices and outcomes in endovascular thrombectomy techniques for the treatment of thrombosed arteriovenous grafts (AVGs) and fistulas (AVFs).

Background

Arteriovenous (AV) access allows patients with end-stage renal disease (ESRD) to receive hemodialysis. Thrombosis of AV access can lead to delay in hemodialysis or abandonment of access requiring dialysis catheter placement. Endovascular approach has become the preferred treatment option for thrombosed access over surgery. Interventions include removal of thrombus from the AV circuit and treatment of the underlying anatomical abnormality, such as an anastomotic stenosis. Thrombolysis, or the act of dissolving thrombus, is performed by using infusion catheters or pulse injector devices for the administration of fibrinolytic agents. Thrombectomy, or the mechanical removal of thrombus, is performed by using embolectomy balloon catheters, rotating baskets or wires, rheolytic and aspiration mechanisms. Adjunctive methods such as cutting balloon angioplasty, drug-coated balloon (DCB) angioplasty, and stent placement are also used to treat stenoses in the AV circuit. Complications of these procedures include vessel rupture, arterial embolism, pulmonary embolism (PE), and paradoxical embolism to the brain.

Methods

This narrative review article was written based on literature search from electronic databases, including PubMed and Google Scholar.

Conclusions

The understanding of thrombectomy techniques and their potential complications is essential in the management of patients with thrombosed AV access.

Scoop thrombectomy: A declotting technique for the treatment of thrombosed autologous arteriovenous fistula. A single-center retrospective study

BACKGROUND

Thrombosis is one of the main complications leading to the failure of autologous arteriovenous fistula (AVF) for patients with renal failure. Thrombectomy is one of the major therapies to remove thrombi to salvage the AVF and prolong its patency.

MATERIALS AND METHODS

Fifty-six patients with AVF thrombosis at the anastomosis were recruited for this study and underwent thrombectomy procedures. Their clinical variables were collected. The vasculature was accessed at the site of the aneurysmal dilatation. Under ultrasound guidance, a scoop thrombectomy procedure was performed by anterograde and retrograde scooping to remove the thrombus using forceps. Then, a sheath was placed in the direct vertical direction. Angioplasty was performed with a balloon to treat the underlying primary arteriovenous stenosis. Patients were followed up for 12 months after surgery. The procedural success, primary and secondary patency rates, and incidence of procedure-related complications were analyzed.

RESULTS

There were 2 minor (3.6%) and no major complications. Clinical success was achieved in 55 of the 56 procedures (98.2%). No symptomatic pulmonary embolism or arterial embolization was noted. The primary patency rates at 3, 6, and 12 months were 92.9, 83.8, and 73.3%%, respectively, according to the Kaplan-Meier survival analysis.

CONCLUSION

Scoop thrombectomy is a safe procedure with high technical success and a low complication rate, and it is an effective method for patients to receive hemodialysis immediately.

Development and Validation of a Machine Learning Model Predicting Arteriovenous Fistula Failure in a Large Network of Dialysis Clinics

Background: Vascular access surveillance of dialysis patients is a challenging task for clinicians. We derived and validated an arteriovenous fistula failure model (AVF-FM) based on machine learning. Methods: The AVF-FM is an XG-Boost algorithm aimed at predicting AVF failure within three months among in-centre dialysis patients. The model was trained in the derivation set (70% of initial cohort) by exploiting the information routinely collected in the Nephrocare European Clinical Database (EuCliD^®). Model performance was tested by concordance statistic and calibration charts in the remaining 30% of records. Features importance was computed using the SHAP method. Results: We included 13,369 patients, overall. The Area Under the ROC Curve (AUC-ROC) of AVF-FM was 0.80 (95% CI 0.79–0.81). Model calibration showed excellent representation of observed failure risk. Variables associated with the greatest impact on risk estimates were previous history of AVF complications, followed by access recirculation and other functional parameters including metrics describing temporal pattern of dialysis dose, blood flow, dynamic venous and arterial pressures. Conclusions: The AVF-FM achieved good discrimination and calibration properties by combining routinely collected clinical and sensor data that require no additional effort by healthcare staff. Therefore, it can potentially enable risk-based personalization of AVF surveillance strategies.

Development and validation of a risk score to prioritize patients for evaluation of access stenosis

Background

Access flow dysfunction, often associated with stenosis, is a common problem in hemodialysis access and may result in progression to thrombosis. Timely identification of accesses in need of evaluation is critical to preserving a functioning access. We hypothesized that a risk score using measurements obtained from the Vasc‐Alert surveillance device could be used to predict subsequent interventions.

Methods

Measurement of five factors over the preceding 28 days from 1.46 million hemodialysis treatments (6163 patients) were used to develop a score associated with interventions over the subsequent 60 days. The score was validated in a separate dataset of 298,620 treatments (2641 patients).

Results

Interventions in arteriovenous fistulae (AVF; n = 4125) were much more common in those with the highest score (36.2%) than in those with the lowest score (11.0). The score also was strongly associated with interventions in patients with an arteriovenous graft (AVG; n = 2,038; 43.2% vs. 21.1%). There was excellent agreement in the Validation datasets for AVF (OR = 2.67 comparing the highest to lowest score) and good agreement for AVG (OR = 1.92).

Conclusions

This simple risk score based on surveillance data may be useful for prioritizing patients for physical examination and potentially early referral for intervention.

Arteriovenous Fistula Flow Dysfunction Surveillance: Early Detection Using Pulse Radar Sensor and Machine Learning Classification

Vascular Access (VA) is often referred to as the “Achilles heel” for a Hemodialysis (HD)-dependent patient. Both the patent and sufficient VA provide adequacy for performing dialysis and reducing dialysis-related complications, while on the contrary, insufficient VA is the main reason for recurrent hospitalizations, high morbidity, and high mortality in HD patients. A non-invasive Vascular Wall Motion (VWM) monitoring system, made up of a pulse radar sensor and Support Vector Machine (SVM) classification algorithm, has been developed to detect access flow dysfunction in Arteriovenous Fistula (AVF). The harmonic ratios derived from the Fast Fourier Transform (FFT) spectrum-based signal processing technique were employed as the input features for the SVM classifier. The result of a pilot clinical trial showed that a more accurate prediction of AVF flow dysfunction could be achieved by the VWM monitor as compared with the Ultrasound Dilution (UD) flow monitor. Receiver Operating Characteristic (ROC) curve analysis showed that the SVM classification algorithm achieved a detection specificity of 100% at detection thresholds in the range from 500 to 750 mL/min and a maximum sensitivity of 95.2% at a detection threshold of 750 mL/min.

Integrated management to reduce fistula-related long-term complications and improve the quality of life after arteriovenous fistula surgery: A retrospective cohort study

AIM

Proper arteriovenous fistula (AVF) management is crucial to avoid AVF complications and prolong its useful life for maintenance haemodialysis (MHD).

DESIGN

Retrospective cohort study.

METHODS

Patients on MHD who underwent AVF surgery at the Wuhan Third Hospital between January 2018 and July 2018.

RESULTS

A total of 144 patients were included, with 56 in the integrated group and 88 in the routine group. There were no differences between the two groups in terms of sex (p = .61), age (p = .62) and type of primary kidney disease (p > .99). At 1 year, the integrated group had significantly fewer fistula-related complications than the routine group (3.6% versus. 23.9%, p < .001). AVF functional scores were lower in the integrated group compared with the routine group (0.1 ± 0.5 versus. 0.8 ± 0.8, p < .001). The pain scores were lower in the integrated group than in the routine group (1.2 ± 0.4 versus. 1.8 ± 0.9, p < .001).

Effects of hemodialysis access surveillance on reducing risk of hemodialysis access thrombosis: A meta-analysis of randomized studies

INTRODUCTION

Vascular access thrombosis remains the Achilles Heel for many a hemodialysis patient. We performed a systematic review and meta-analysis to assess the impact of monitoring vascular access blood flow on prediction and prevention of vascular access thrombosis. We hypothesized that monitoring vascular access blood flow has a pivotal role in lowering the risk of thrombosis and subsequent access failure.

METHODOLOGY

We conducted a systematic review in PubMed and EMBASE databases to identify randomized studies that have assessed the effect of hemodialysis access surveillance on the risk of thrombosis. A random-effects model was used for the meta-analysis. Subgroup analysis was performed among patients with arterio-venous fistula (AV-fistulas) and those with arterio-venous graft (AV-grafts).

RESULTS

Ten randomized studies were included in the meta-analysis. The total number of patients included in the analysis was 1430. On performing the random-effects model among the included studies, hemodialysis access surveillance was associated with better outcomes (risk ratio = 0.73, 95% confidence interval ranges from 0.55 to 0.98). The analysis of the AV-fistula group showed an estimated overall risk ratio of 0.55 (95% confidence interval ranges from 0.33 to 0.89) favoring access surveillance. However, in the AV-grafts group, the estimated overall risk ratio was 0.92 (95% confidence interval ranges from 0.65 to 1.29) showing no additional benefit for access surveillance.

CONCLUSION

Hemodialysis access surveillance using access blood flow monitoring can reduce the risk of access thrombosis for patients with AV-fistulas, but this is not the case with AV-grafts.

Analysis of access flow using duplex ultrasonography and the ultrasound dilutional method

BACKGROUND

This study aimed to evaluate the correlation between duplex ultrasonography (DUS) and ultrasound dilution (UD) measurement's results and determine the factors affecting the correlation of the measured values among other clinical factors in patients.

METHODS

This cross-sectional study was conducted from April 2020 to May 2020 and included 60 patients who visited our dialysis centre. The flow of the fistula was measured in the proximal brachial artery using DUS. While dialysis was performed on the same day, the access flow was measured using the UD method. The correlation and agreement between the access flows acquired by each measurement method were analysed. Similarly, the correlation was analysed by classifying the groups based on the predisposing factor, and statistically significant factors were observed through comparison.

RESULTS

Both measurements showed a moderate positive correlation (r = 0.60, p < 0.01). The bias (mean of UD-DUS) between the two measurements was about 230 mL/min. When the measurement site of DUS was near the inflow artery and in the same anatomical section, a strong correlation with the measurement value of UD was observed (brachial based fistula: r = 0.85, radial based fistula: r = 0.87). Similarly, for patients without diabetes and those who regularly underwent access surveillance for the dialysis route, strong correlations were observed between the two measurements (r = 0.79 and r = 0.88).

CONCLUSIONS

Several factors can influence the correlation between UD and DUS. The findings showed a high correlation for DUS measurement sites within the same anatomical section as the inflow artery, patients without diabetes, and patients undergoing periodic surveillance.