Access Blood Flow Research Articles

Investigation of the Effect of Variations in the Puncture Site of the Arteriovenous Fistula on Access Blood Flow Measurement by Ultrasound Dilution Method

Investigation of the Effect of Variations in the Puncture Site of the Arteriovenous Fistula on Access Blood Flow Measurement by Ultrasound Dilution Method

Risk factors for thrombosis in dialysis patients: A comprehensive systematic review and meta-analysis

AimTo identify the factors associated with thrombosis in dialysis patients. BackgroundThrombosis is a leading cause of vascular access failure in dialysis patients. Numerous risk factors contribute to thrombosis in this population. MethodsA systematic search was conducted across international databases using standardized keywords. The quality of the selected studies was assessed using the STROBE and CONSORT checklists. The findings were summarized in a Garrard table. Meta-analysis was performed using CMA software. The study adhered to the guidelines outlined in the PRISMA statement. ResultsA total of 180 articles were reviewed. The odds ratio for thrombosis in patients with arteriovenous grafts compared to arteriovenous fistulas was 10.93 (95 % CI: 9.35-12.78), demonstrating statistical significance (P = 0.001). Similarly, hemodialysis patients had an odds ratio of thrombosis 3.60 times higher than non-hemodialysis patients (95 % CI: 3.54-4.19), with statistical significance (P = 0.001). Patients undergoing single-stage basilic vein transposition had a 1.89 times higher risk of thrombosis compared to those undergoing two-stage transposition (95 % CI: 1.04-3.46), also demonstrating statistical significance (P = 0.038). ConclusionsThrombosis in patients with end-stage renal disease undergoing dialysis was significantly associated with various factors, including graft access, single-stage basilic vein transposition, and hemodialysis. Additional contributing factors to thrombosis included diabetes, elevated homocysteine levels, female gender, age over 50, access location, and low access blood flow velocity. The analysis revealed a higher incidence of thrombosis in end-stage renal disease patients undergoing hemodialysis compared to those not undergoing dialysis, as well as in patients with arteriovenous grafts compared to those with arteriovenous fistulas. These findings underscore the importance of recognizing and managing these risk factors to prevent thrombotic events and enhance patient care within the dialysis setting.

Progressive increase in vascular access blood flow after percutaneous transluminal angioplasty in patients on hemodialysis.

Percutaneous transluminal angioplasty (PTA) is the gold standard for treating stenoses with dysfunctional vascular access. Recently, we found that vascular access blood flow (VABF) measured immediately after PTA increased over time without the need for additional procedures in the patients who underwent PTA. Therefore, this study was conducted to confirm an increase in VABF after PTA and identify the factors associated with it. Patients on chronic hemodialysis at a single institution were retrospectively reviewed and those with accesses that had a measurement of VABF immediately after PTA and within 1 month from PTA were included in the study. The relationship between clinical parameters and changes in VABF were analyzed using paired t-test and linear regression. A total of 47 PTA accesses (fistulas, 26; grafts,21) were included. The mean VABF on the day of PTA and the following measurement were 796.9 ± 329.1 mL/min and 1105.1 ± 410.3 mL/min, respectively. In the univariate analysis, the diameter of the balloon catheter used in the PTA and serum uric acid (SUA) level were significantly associated with an increase in VABF. Atrial fibrillation was a significant factor for the percentage change in vascular access. In the multivariate analysis, SUA level, balloon catheter diameter, and atrial fibrillation remained independent factors for changes in VABF and percentage change in VABF, respectively. The study identified progressive increases in the VABF after PTA without additional procedures. SUA level, balloon catheter diameter used in PTA, and atrial fibrillation were independently associated with changes in VABF.

#540 Investigation of vascular sound visualization system using electronic stethoscope

Abstract Background and Aims The routine evaluation of VA involves visual, palpatory, and auscultatory examinations, as well as monitoring of venous pressure and other parameters. Surveillance indices include Flow Volume (FV) and Resistance Index (RI) obtained by Doppler ultrasound (DU) and Access Blood Flow (Qa) obtained by the Ultrasound Dilution Method (UDM) are well known. On the other hand, the MSS-U11C electronic stethoscope (Fig. 1) and dedicated application (Fig. 2) developed by Pioneer Inc. converts vascular sound into digital data and calculates the INDEX value obtained from the sound intensity (dB) analyzed by the vascular sound visualization system. In this study, we examined the correlation between INDEX values and conventional surveillance indices. Method 1. Eighty-three cases in which INDEX, FV, RI, and Qa were simultaneously measured in hemodialysis patients with AVF at the Artificial Kidney Department of Osaka Metropolitan University Hospital were included. 2. The measurement site for INDEX was just above the anastomosis of the AVF. 3. FV and RI were measured using a KONICA MINOLTA SONIMAGE HS2 diagnostic ultrasound system with the brachial artery as the measurement site. 4. Measurements were expressed in Median [IQR], and for statistical examination, Pearson's correlation coefficient was used for the correlation of each measurement, transformed to the natural logarithm to satisfy the assumption of normality of the residuals. The significance level for all hypothesis tests was 5%. For statistical analysis, R version 4.2.1 (https://www.r-project.org/foundation/) with the “rms” and “RcmdrPlugin.EZR ” packages were used. 5. This study protocol was conducted in accordance with the Principles of the Declaration of Helsinki. The ethics review boards of Osaka Metropolitan University approved the study (No. 2021-243). Opt-out consent was obtained instead of written informed consent. Results INDEX showed a significant positive correlation with Qa and FV (R = 0.449, P = 0.002 / R = 0.484, P < 0.001, respectively), INDEX showed a significant negative correlation with RI (R = −0.336, P = 0.002). Conclusion INDEX measurement using an electronic stethoscope is a monitoring index and showed a positive correlation with FV and Qa, which are established surveillance indices, and a weak negative correlation with RI. In Japan, FV and RI are commonly used as surveillance indices, but it has been reported that these indices can be underestimated or overestimated depending on the skill of the examiner, and that Qa requires specialized equipment and cannot be measured depending on the puncture site. We believe that monitoring by stethoscope is influenced by subjective factors of staff members, which may lead to differences in evaluation, but INDEX could become a more quantitative and standardized indicator. In addition, the electronic stethoscope could be used without any difference compared to the stethoscope currently in clinical use.

#2778 The Charlson Index can be used prospectively to identify patients who will need a close follow up of surveillance for the vascular access

Abstract Background and Aims The primary screening methods for monitoring vascular access in haemodialysis involve measuring access blood flow and dialysis venous pressure. However, challenges are present in both aspects, potentially hindering the attainment of desired results. Research in this field is crucial to identify the optimal combination of intensive clinical monitoring and supplementary surveillance for effective outcomes. For this reason, we aim to describe the impact of comorbidities and patency of native arteriovenous fistulae (nAVF). Method Descriptive study of prevalent patients on haemodialysis, carried out by consulting electronic medical records over a period of 35 months. Demographic and vascular access-related variables were included. Primary and secondary patency was calculated for all accesses. Patients with upper limb AVF were classified according to distal and proximal access location; and the Charlson Index was used to categorise patients according to comorbidities. Kaplan Meyer survival curves were used to contrast the impact of comorbidities on the different patency. Results 52 patients, age 70.7 ± 1.57 years, 69.2% male, 42.3% diabetic, Charlson index with a median of 7 (6.5 - 7.73), 98.1% with a native fistula, the most frequent nAVF location in our population was humerocephalic (63.5%) and a predominance of the left upper extremity (65.4%). According to the location of the access, adjusted by the Charlson index, it is evident that in proximal accesses (humerocephalic and basilic humerus nAVF), with a Charlson Index less than or equal to 7, the time required to reach an event was statistically significantly longer (Log Rank Test (Mantel-Cox): primary patency p=0.057 and secondary patency p=0.069). This comparison was not significant in distal fistulas. Conclusion Using the Charlson comorbidity index information, we transformed it into an accessible and valuable tool for maintaining vascular access patency. Close follow-up in patients with proximal nAVF and high Charlson comorbidity index could be beneficial.

Integrating vascular access surveillance with clinical monitoring for stenosis prediction.

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 andto an incresed risk ofmortality.The aim of the present study wasto assess the results of integrating strictvascular access blood flow surveillance with routine clinical monitoring for predicting vascular access stenosis in chronic hemodialysis patients. In this retrospective study, chronic dialysis patients with arteriovenous fistula or arteriovenous graft were included from a settingin 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 quarterlyblood 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. Of 397 included patients, 336 had anarteriovenous fistula and 61 had anarteriovenous graft. In 2017, 106 percutaneous transluminal angioplasty procedures were performed in patients with anarteriovenous fistula, and 63 in patients with anarteriovenous graft. The results revealed similar predictive performance of surveillance models using an absolute blood flow threshold of < 500 or < 400mL/min in predicting stenosis inpatients with arteriovenous fistula. Blood flow surveillance models for patients with anarteriovenous fistula had significantly higher accuracy than those for patients with anarteriovenous graft. Furthermore, the use ofarelative threshold, defined as blood flow < 1000mL/min and a 25% decline in blood flow, did not affect thepredictive performance of blood flow surveillance models. Blood flow surveillance models using thresholds of < 400 and < 600mL/min, followed by thorough physical examination, showed an accuracy of 91.54% and 72.15% in predicting stenosis inpatients 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.

Systemic vascular resistance predicts high-output cardiac failure in patients with high-flow arteriovenous fistula.

Patients with high-flow arteriovenous (AV) access are at risk of developing high-output cardiac failure (HOCF) and subsequent hospitalization. However, diagnosing HOCF is challenging and often requires invasive procedures. The role of systemic vascular resistance (SVR) in diagnosing HOCF is underestimated, and its predictive value is limited. Our study aims to identify non-invasive risk factors for HOCF to facilitate early diagnosis and timely surgical interventions. We included 109 patients with high-flow AV access who underwent serial echocardiography. The retrospective cohort was divided into two groups based on their hospitalization due to HOCF. The two groups were matched for age and gender. After a mean follow-up of 25.1months, 19 patients (17.4%) were hospitalized due to HOCF. The two groups had similar baseline characteristics. However, the HOCF group had a higher value of vascular access blood flow (Qa) (2168±856 vs. 1828±617mL/min; P=0.045). Echocardiographic analysis revealed that the HOCF group had more pronounced left ventricular diastolic dysfunction (E/e': 21.1±7.3 vs. 16.2±5.9; P=0.002), more severe pulmonary hypertension (right ventricular systolic pressure: 41.4±16.7 vs. 32.2±12.8; P=0.009), a higher Doppler-derived cardiac index (CI) (4.3±0.8 vs. 3.7±1.1; P=0.031), and a lower Doppler-derived estimated SVR (eSVR) value (5.5±0.3 vs. 6.9±0.2; P=0.002) than the non-HOCF group. Using multivariable Cox regression analysis, a low eSVR value (<6) emerged as an independent predictor of HOCF hospitalization with a hazard ratio of 9.084 (95% confidence interval, 2.33-35.39; P=0.001). Receiver operating characteristic curve analysis indicated that CI/eSVR values more accurately predicted HOCF hospitalization [sensitivity: 94.7%, specificity: 51.0%, area under the curve (AUC): 0.75, P<0.001] than the Qa/cardiac output ratio (AUC: 0.50, P=0.955), Qa values≥2000mL/min (AUC: 0.60, P=0.181), and Qa values indexed for height in metres (AUC: 0.65, P=0.040). In patients with high-flow AV access, low eSVR values obtained through non-invasive Doppler echocardiography were associated with a high rate of HOCF hospitalizations. Therefore, routine eSVR screening in these patients might expedite the diagnosis of HOCF.

A scoping review of outcomes with routine surveillance of arterio-venous fistulas.

The arteriovenous fistula (AVF) is the preferred venous access for maintenance haemodialysis. AVF dysfunction can progress to access failure, with all the associated morbidity and costs of revising vascular accesses. Routine surveillance of AVFs using specialised equipment has the potential to enable early detection of potential problems. The KDOQI Clinical Practice Guidelines for Vascular Access: Update 2019 suggest that surveillance may be useful to supplement regular clinical monitoring but acknowledge a lack of evidence to make firm recommendations. This scoping review of peer-reviewed literature explored outcomes with the routine surveillance of AVFs using specialised equipment in haemodialysis dependent adults. A systematic search was undertaken using terms such as 'vascular access', haemodialysis, surveillance and 'access flow', utilising the data bases ProQuest (Medline), CINAHL and Embase to include original research articles published between October 2016 and August 2022. A total of eight papers were identified for comprehensive analysis, including two randomised controlled trials, two cross-sectional studies, two retrospective reviews and two evaluations. Themes identified include the incidence of thrombotic events, the role of access blood flow measurements, the need for follow-up angiograms after surveillance and identification of the at-risk access. This review of research published in recent years demonstrated an ongoing paucity of evidence for the benefits of routine AVF surveillance. More research focused on actual outcomes is needed in this important area that is a routine part of dialysis unit workloads everywhere.

Hemodialysis through persistent left superior vena cava. Should it be used?

Background To describe a case of hemodialysis done through persistent left superior vena cava, identified incidentally after a left jugular central venous dialysis catheter insertion, and to discuss its feasibility. Case Summary Single case: A 66-year-old woman was admitted to the ICU with a diagnosis of septic shock, severe pneumonia, and acute renal failure. Hemodialysis was required for acute renal insufficiency. Persistent left superior vena cava (PLSVC) was detected on Chest x-ray after a left jugular central venous dialysis catheter placement. Hemodialysis was uneventful. Using a permanent dialysis catheter placed later through the PLSVC was less efficient. Although no complications were seen during hemodialysis, it was technically difficult (with high pressure in access and low blood flow rate). Conclusion Hemodialysis through PLSVC should remain an exceptional and short-term therapeutic alternative in dialysis patients.

The impact of vascular access location on pulmonary arterial pressure in chronic kidney disease patients undergoing hemodialysis.

It is feared that among chronic kidney disease patients undergoing hemodialysis, arteriovenous fistula (AVF) itself could contribute to pulmonary hypertension (PH). The impact of AVF location on PH is yet to be assessed. We hypothesize that patients with proximal AVF have higher access blood flow and hence higher pulmonary arterial systolic pressure (PASP) than those with distal AVF. We aimed to compare the PASP between patients with proximal and distal AVF. In this cross-sectional study, PASP was estimated using Doppler echocardiography and blood flow in the AVF was assessed by Doppler ultrasound. PASP was modeled by multivariate linear regression. AVF location was the primary exposure of interest. Out of 89 patients undergoing hemodialysis, 72 (81%) had PH defined as PASP >35 mmHg. The mean blood flow in proximal and distal AVF was, respectively, 1240 and 783 mL/min (mean difference 457 mL/min, p < 0.001). Mean PASP in patients with proximal AVF was 16.6mmHg higher than those with distal AVF (p < 0.001, 95% CI 8.3-24.9). There was a positive correlation between access blood flow and PASP (r = 0.28, p = 0.007). If access blood flow was included as a covariate in the multivariate model, the association between AVF location and PASP ceased to exist. Patients with proximal AVF have a significantly higher PASP than those with distal AVF, and this could be attributed to the higher blood flow in proximal AVF compared to distal AVF.

Double guidewire technique (DGT): Optimising endovascular revision of juxta-anastomotic stenosis in AV-fistulae: A retrospective analysis.

Arteriovenous fistula (AVF) is the preferred angioaccess for haemodialysis but suffers from a high stenosis rate, juxta-anastomotic stenosis (JAS) being the most frequent. Percutaneous transluminal angioplasty (PTA) of JAS would have some advantage (such as mini-invasive and vein sparing treatment), but higher recurrence rate is observed as compared to surgery. We report results of juxta anastomotic stenosis PTA using the 'double guide technique' (DGT) as described by Turmel-Rodrigues, in a selected cohort from our Vascular Access Centre. From January to June 2018, 25 consecutive patients were treated by DGT. By means of retrograde access through the outflow vein by a 6 F introducer, two guide wires were navigated: one into proximal radial artery (GW1), the other into distal artery (GW2). GW2 was used to dilate juxta-anastomotic vein and anastomotic area with 6 mm high-pressure balloon, while by GW1 juxta-anastomotic artery was dilated with 4 mm semi-compliant balloon. Mean diameter of balloons were 6.7 and 4.1 mm for venous and arterial tract dilatation. Follow up was carried out up to 12 months. Prospectively collected data were analysed retrospectively. One-year primary and secondary patency was 52% and 95% respectively. Recurrence rate was 0.56 procedure/pt/year. Mean access blood flow at 12 months was 830 ml/min. Double Guidewire Technique is an effective and minimally invasive procedure. By avoiding under dilation of JAS the recurrence rate resulted quite satisfactorily in our population.

Reduction of arteriovenous access blood flow in kidney transplant patients.

Cardiovascular disease is the most frequent cause of death in kidney transplant patients. High-flow arteriovenous fistula (AVF) increases cardiac output and may contribute to hyperkinetic heart failure. AVF follow-up is not implemented in kidney transplant patients. The aim of this study was to reduce AVF blood flow in a group of patients with a high-flow AVF following kidney transplantation to reduce cardiac strain. This prospective study was performed in kidney transplant patients who had a vascular access created before transplantation. The AVF of these patients was examined by ultrasound with a focus on AVF flow and brachial artery size. If high-flow AVF was detected, flow reduction was performed in the indicated group of patients. The study examined 164 patients, of whom 24 had a hyperfunctional AVF (14.8%). A total of 16 AVF flow reductions were performed, which led to an average decrease in cardiac index by 0.77 L/min/m2. Primary patency of the reconstructions was 93.33% after 12 months. All patients experienced a subjective improvement in dyspnea. Reduction in AVF flow leads to an improvement in the quality of life of kidney transplant patients. Maintaining a functional AVF is beneficial, especially for patients after repeated surgeries, where the option of creating an autologous AVF is limited.

Study of Anti-C1q Antibodies in Egyptian Systemic Lupus Erythematosus Patients.

Autoantibodies to complement are associated with various diseases. Anti-C1q antibodies are present in all patients with hypocomplementemic urticarial vasculitis, but also with varying prevalence in other conditions. Anti-C1q may interfere with the clearance of apoptotic cells, so influencing induction and expression of autoimmunity. The aim of this work is to study the relation between anti-C1q antibodies and systemic lupus erythematosus (SLE) and its manifestations including renal affection. The presence and levels of anti-C1q antibodies were investigated using enzyme-linked immunosorbent assay technique. The study included 70 Egyptian patients suffering from SLE and 18 healthy controls. They were 65 females and five males. Their age ranged from 12 to 48.5 years with a mean value of 27.4 ± 8.4. Anti-C1q antibodies were statistically significantly elevated in cases compared with controls being positive in 37.2% (mean 18.3 ± 27.1) in patients versus 11.1% (mean value 4.1 ± 3.5) in controls (P = 0. 03). Anti-C1q antibody-positive patients (n = 226) had significantly higher SLE Disease Activity Index (SLEDAI) (16.1 ± 9.9) compared to negative patients (n = 44) (SLEDAI = 8.1 ± 7.7) P = 0.000. Regarding renal affection, the presence of anti-C1q-positive antibodies was associated with proteinuria, P = 0.002. In conclusion, anti-C1q was more common in patients with SLE and disease activity. We confirmed a significant association of anti-C1q with renal involvement, independent of demographics and other serologies.

Correlation of Serum Vitamin D Levels to Vascular Access Dysfunction in Prevalent Hemodialysis

Abstract Vascular access dysfunction in hemodialysis patients has been correlated to low serum vitamin D level in previous studies. Vitamin D deficiency and hepatitis C virus infection have been linked to endothelial cell dysfunction, promoting inflammatory cascade.30 negative - &amp; 30 positive - hepatitis C virus patients on prevalent hemodialysis in Ain Shams University Hospitals, were enrolled in the study. All patients had access blood flow &amp;lt; 800 ml/min. For all patients we performed: complete physical examination, complete blood count, serum ferritin, ESR 1st and 2nd hours, CRP, blood urea, serum creatinine, serum albumin, total and direct bilirubin, alanine transferase, aspartate transferase, prothrombin time, International Normalized Ratio, serum calcium and phosphorus, and serum intact parathyroid hormone. Previous laboratory tests were performed using conventional methods within our hospitals laboratories. Serum vitamin Dlevel was measured by Enzyme Linked Immunosorbent Assay. Access blood flow was measured by Duplex Ultrasound. Vitamin D serum level was &amp;lt; 20 ng/ml within negative and positive groups with no significant difference between them. Vascular access flow was significantly lower within positive patients. Parathyroid hormone, Phosphorus, Prothrombin time, International Normalized Ratio, Alanine - and Aspartate - transferase were significantly higher within positive patients. We deduced that Vitamin D level &amp;lt; 20ng/ml was associated with reduced vascular access blood flow &amp;lt; 800 ml/min, with much more reduced access flow within hepatitis C virus positive patients. [Mona Hosny Abdel Salam, Reem Jan Farid, Mostafa Abdelnassier Abdelgawad and Marwa Salim Youssef Ismail. Correlation of Serum Vitamin D Levels to Vascular Access Dysfunction in Prevalent Hemodialysis.

Mathematical Models for Blood Flow Quantification in Dialysis Access Using Angiography: A Comparative Study.

Blood flow rate in dialysis (vascular) access is the key parameter to examine patency and to evaluate the outcomes of various endovascular interve7ntions. While angiography is extensively used for dialysis access–salvage procedures, to date, there is no image-based blood flow measurement application commercially available in the angiography suite. We aim to calculate the blood flow rate in the dialysis access based on cine-angiographic and fluoroscopic image sequences. In this study, we discuss image-based methods to quantify access blood flow in a flow phantom model. Digital subtraction angiography (DSA) and fluoroscopy were used to acquire images at various sampling rates (DSA—3 and 6 frames/s, fluoroscopy—4 and 10 pulses/s). Flow rates were computed based on two bolus tracking algorithms, peak-to-peak and cross-correlation, and modeled with three curve-fitting functions, gamma variate, lagged normal, and polynomial, to correct errors with transit time measurement. Dye propagation distance and the cross-sectional area were calculated by analyzing the contrast enhancement in the vessel. The calculated flow rates were correlated versus an in-line flow sensor measurement. The cross-correlation algorithm with gamma-variate curve fitting had the best accuracy and least variability in both imaging modes. The absolute percent error (mean ± SEM) of flow quantification in the DSA mode at 6 frames/s was 21.4 ± 1.9%, and in the fluoroscopic mode at 10 pulses/s was 37.4 ± 3.6%. The radiation dose varied linearly with the sampling rate in both imaging modes and was substantially low to invoke any tissue reactions or stochastic effects. The cross-correlation algorithm and gamma-variate curve fitting for DSA acquisition at 6 frames/s had the best correlation with the flow sensor measurements. These findings will be helpful to develop a software-based vascular access flow measurement tool for the angiography suite and to optimize the imaging protocol amenable for computational flow applications.

ASDIN white paper: Management of cephalic arch stenosis endorsed by the American Society of Diagnostic and Interventional Nephrology.

Brachiocephalic arteriovenous fistulas (AVF) makeup approximately one third of prevalent dialysis vascular accesses. The most common cause of malfunction with this access is cephalic arch stenosis (CAS). The accepted requirement for treatment of a venous stenosis lesion is ⩾50% stenosis associated with hemodynamically abnormalities. However, the correlation between percentage stenosis and a clinically significant decrease in access blood flow (Qa) is low. The critical parameter is the absolute minimal luminal diameter (MLD) of the lesion. This is the parameter that exerts the key restrictive effect on Qa and results in hemodynamic and functional implications for the access. CAS is the result of low wall shear stress (WSS) resulting from the effects of increased blood flow and the unique anatomical configuration of the CAS. Decrease in WSS has a linear relationship to increased blood flow velocity and neointimal hyperplasia exhibits an inverse relationship with WSS. The result is a stenotic lesion. The presence of downstream venous stenosis causes an inflow-outflow mismatch resulting in increased pressure within the access. Qa in this situation may be decreased, increased, or within a normal range. Over time, the increased intraluminal pressure can result in marked aneurysmal changes within the AVF, difficulties with cannulation and the dialysis treatment, and ultimately, increasing risk of access thrombosis. Complete characterization of the lesion both hemodynamically and anatomically should be the first step in developing a strategy for management. This requires both access flow measurement and angiographic imaging. Patients with CAS present a relatively broad spectrum as relates to both of these parameters. These data should be used to determine whether primary treatment of CAS should be directed toward the anatomical lesion (small MLD and low Qa) or the pathophysiology (large MLD and high Qa).

Reduction of arteriovenous access blood flow leads to biventricular unloading in haemodialysis patients

AimsPatients on chronic haemodialysis have a wide range of changes in cardiac function and structure, including left ventricular hypertrophy, dilation and diastolic dysfunction or pulmonary hypertension. All these changes were linked to increased mortality in previous studies. High-flow arteriovenous fistulas (AVF) are supposed to be a factor contributing to their development. This study investigated the early effect of surgical AVF blood flow (Qa) reduction on these changes in patients with or without heart failure changes. Methods and resultsForty-two patients in chronic haemodialysis programme with high-flow AVF (Qa over 1500 mL/min), indicated for surgery for ≥1 of the following indications: 1.manifest heart failure; 2.hand ischemia; 3.advanced structural heart changes detected by echocardiography. The patients underwent echocardiography on selection visit, before blood flow reducing surgery and six weeks thereafter. The Qa reduction led to decrease of left ventricular mass (p = 0.02), end-diastolic volume (p = 0.008), end-diastolic diameter (p = 0.003) and left atrial volume (p = 0.0006). Diastolic function improved. Similarly, right ventricular diameter and right atrial volume decreased (p = 0.000001 and 0.00009, respectively) together with the decrease of estimated pulmonary artery systolic pressure. 81% of patients suffered from pulmonary hypertension prior to surgery, only 36% thereafter. ConclusionThe surgical restriction of the hyperkinetic circulation leads to several improvements of heart structure and function, which was linked to higher mortality in other studies. The beneficial effect of Qa reduction is present even in patients without symptoms of heart failure. The contribution of AVF must be considered with structural or functional heart changes.

Vascular Access Perspectives in Patients After Kidney Transplantation.

Introduction: More attention has been paid to the influence of arteriovenous fistula (AVF) on the cardiovascular system. In renal transplant recipients, some beneficial effect of an elective vascular access (VA) ligation was observed in patients with a high AVF flow. However, this strategy is not widely accepted and is in contradiction to the rule of vasculature preservation for possible future access. The aim of our study is to elucidate the vascular access function and VA perspective in the kidney transplantation (KTx) population.Materials and Methods: KTx patients with a stable graft function were recruited to participate in this single center observational study (NCT04478968). The measurement of VA flow and vessel mapping for future vascular access was performed by a color Doppler ultrasound. The study group included 99 (63%) males and 58 (37%) females; the median age was 57 (IQR 48–64) years. The median time from the transplantation to the baseline visit was 94 (IQR 61–149) months. Median serum creatinine concentration was 1.36 (IQR 1.13–1.67) mg/dl.Results: Functioning VA was found in 83 out of 157 (52.9%) patients. The sites were as follows: snuffbox in six (7.2%), wrist in 41 (49.4%), distal forearm in 18 (21.7%), middle or proximal forearm in eight (9.6%), upper-arm AV graft in one (1.2%), and upper-arm AVFs in nine (10.8%) patients, respectively. Blood flow ranged from 248 to 7,830 ml/min; the median was 1,134 ml/min. From the transplantation to the study visit, 66 (44.6%) patients experienced access loss. Spontaneous thrombosis was the most common, and it occurred in 60 (90.9%) patients. The surgical closure of VA was performed only in six (4%) patients of the study group with a functioning VA at the time of transplantation. Access loss occurred within the 1st year after KTx in 33 (50%) patients. Majority (50 out of 83, 60.2%) of the patients with an active VA had options to create a snuffbox or wrist AVF on the contralateral extremity. In a group of 74 patients without a functioning VA, the creation of a snuffbox or wrist AVF on the non-dominant and dominant extremity was possible in seven (9.2%) and 40 (52.6%) patients, respectively. In 10 (13.1%) patients, the possibilities were limited only to the upper-arm or proximal forearm VA on both sides. Access ligation was considered by 15 out of 83 (18.1%) patients with a patent VA.Conclusions: In the majority of the patients, vascular access blood flow was below the threshold of the negative cardiovascular effect of vascular access. Creation of a distal AVF is a protective measure to avoid a high flow and preserve the vessels for future access. The approach to VA should be individualized and adjusted to the patient's profile.

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

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. 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). 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. 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.

Dialysis efficacy and pain levels in relation to cannulation distance using the buttonhole technique

ObjectiveIn this study, we investigated whether there was any difference in pain and dialysis efficacy when patients who initially entered dialysis with the rope ladder technique were switched to the buttonhole technique.MethodsWe reduced the space between needles and examined the effects on access blood flow rate, dialysis efficacy, and pain levels with BH technique. Forty-four patients participated, 25with dialysis needles placed 5–7 cm apart using the BH technique, and 19 with needles placed 7–10 cm apart.ResultsThere was a significant reduction in the pain sensation in both groups from patients who passed the rope ladder technique to the buttonhole technique from the onset to the sixth month. There was no difference in dialysis efficacy between the patients who passed the lope ladder technique to the buttonhole technique; also, there was no difference in the dialysis efficacy compared to the needle entry interval in two groups of patients who were dialyzed with the BH technique.DiscussionThe BH technique continues to attract interest due to its dramatically reduced pain levels compared to the RL technique and no difference in dialysis efficacy.