Evaluation of arteriovenous fistula maturation and early prediction of clinical eligibility, using ultrasound: The Fistula Maturation Evaluation (FAME) Study.

INTRODUCTION: The study of time-related alterations of ultrasound-determined parameters during maturation, and the assessment of time to hemodynamic maturation, enabling early prediction of clinical eligibility, of hemodialysis autologous arteriovenous fistulae (AVF). METHODS: This is an observational, prospective, study of only AVF-eligible patients referred for access creation, from 02/2019 to 02/2022 (ClinicalTrials.gov identifier: NCT0473687). Brachial artery diameter (dBA), access flow volume (FV), non-augmented efferent vein diameter (dEV), resistivity index (RI), and efferent vein total wall thickness (tEV), were assessed by ultrasound. Measurements were conducted daily in the first week and repeated on days 14, 21, 30, 60, and 90, postoperatively. The primary endpoint included the documentation of serial changes of flow and structural parameters related to AVF maturation in the first 90 days of the post-operative period and maturation early prediction. Secondary endpoints included the determination of factors affecting maturation. RESULTS: One hundred one participants (mean age, 67 ± 6 years; 76 males) were enrolled. Average dBA and FV reached maximum on day 60 (5.64 ± 0.85 mm) and 90 (1.172 ± 617 mL/min), respectively. Day 7 values of dBA (5.48 ± 0.73 mm) and FV (1.039 ± 531 mL/min) did not alter significantly during the follow-up period. Parameters indicative of clinical functionality, dEV (5.82 ± 0.90 mm) and tEV (0.493 ± 0.10 mm), reached approximately 90% of maximum (6.66 ± 1.42 mm and 0.526 ± 0.11 mm), by day 14. RI reached minimum on day 30 (0.46 ± 0.09), without significant changes after day 2 (0.48 ± 0.09, p = 0.284). A significant correlation was identified, between day 7 FV and day 60 dEV (r = 0.40, p = 0.0002). A FV cut-off value ⩾657.51 mL/min, on day 7, predicted successful fistula maturation with 85% sensitivity and 100% specificity. Multivariate analysis identified female gender, age >75, diabetes, and wrist access as independent predictors of decreased values of maturation parameters. CONCLUSION: Hemodynamic maturation is completed by the first postoperative week, while AVF is clinically functional, by the second. FV can be used for early prediction of maturation.

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 access flow measurement: Comparison of ultrasound dilution and ultrafiltration method on NIKKISO DBB-EXA™ dialysis machine.

BACKGROUND: The methods of estimating vascular access (VA) flow rates are usually based on the indicator dilution theory by measuring recirculation during dialysis sessions. METHODS: This is an observational study comparing the VA flow rates measured by NIKKISO DBB-EXA™ and Transonic®. Sixty-five patients (38 M/27 F, mean age 72 ± 10 years) participated in the study. We measured the VA flow rates during dialysis twice with each method and repeated the procedure 7 days later. RESULTS: In 130 double measurements for each method on the same day, mean flow with Transonic® was 1413±715 ml/min and with DBB-EXA™ 1297 ± 664 ml/min. In Bland-Altman analysis, the mean difference between the two methods was 159 ± 211 ml/min (limits of agreement: -274 and 572 ml/min). Eighty-one out of the 130 DBB-EXA™ measurements were within 25% of the Transonic® measurements (62% accuracy). Regarding reproducibility of each method on different days, mean difference in the Bland-Altman analysis was 29 ± 620 ml/min (limits of agreement: -1186 and 1244 ml/min) for the Transonic® measurements and 132 ± 625 ml/min (limits of agreement: -1092 and 1356 ml/min) for the DBB-EXA™ measurements. The measurements on two different days were within 25% of each other for 52 of the 65 patients (80%) with the Transonic® method, and for 35 of the 65 patients (54%) with the DBB-EXA™ method. CONCLUSIONS: In conclusion, the DBB-EXA™ method underestimates VA flow rates compared to the Transonic® technique, resulting in a limited accuracy of 62%. There was poor reproducibility for both methods in different day measurements with better performance of the Transonic® technique. The DBB-EXA™ method could be used as a simple tool for a rough estimate of VA flow rates but cannot replace the Transonic® reference method.

Acute hemodynamic changes during far infrared treatment of the arteriovenous fistula in hemodialysis patients.

BACKGROUND: The arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis (HD) treatment and preservation of a stable vascular access is crucial. Long term Far Infrared Radiation (FIR) has been found to increase access flow together with an enhanced maturation and patency of the AVF. The acute effects of FIR on access flow have been sparsely described and the results are contradictory, perhaps due to differences in measurement conditions and other factors of importance for access flow. METHODS: Twenty patients in HD with an AVF were included. Each patient was randomized to receive either FIR (FIR group) or no FIR (control group). The acute changes in access flow were investigated in both groups on the second dialysis day of the week and during the first 1.5 h of the dialysis session. Concomitant changes in hemodynamic parameters of importance for access flow were also explored. RESULTS: There was no significant change in access flow in the FIR group compared with the control group (median (Interquartile Range)) (-10 (-413.8; 21.3) ml/min vs -17.5 (-83.8; 76.3) ml/min, p = 0.58). There was no significant difference in any of the hemodynamic parameters between the FIR and the control group; cardiac output (-0.7 (-1.2; -0.2) l/min vs -0.4 (-0.9; 0.1) l/min, p = 0.58), cardiac index (-0.3 (-0.5; -0.1)) l/min/m2 vs -0.3 (-0.4; 0) l/min/m2, p = 0.68), mean arterial pressure (5.5 (-1.8; 8.4) mmHg vs 1.5 (-3; 6.3) mmHg, p = 0.35) and total peripheral resistance (2 (1.8; 3.4) mmHg × min/l vs 1 (-0.3; 3.1) mmHg × min/l, p = 0.12). CONCLUSION: In this trial, with a highly standardized set-up, one session of FIR did not result in any acute changes in access flow. This was not due to differences in the hemodynamic parameters between the groups.

Comparing non-invasive diagnostic methods for arteriovenous fistula stenosis: a prospective study.

PURPOSE: International guidelines recommend screening for arteriovenous fistula (AVF) stenosis using various non-invasive methods. We evaluate different non-invasive AVF flow measurements for detecting AVF stenosis. METHODS: Twenty-three haemodialysis patients with suspected AVF stenosis are enrolled based on abnormal physical signs or high venous pressure during dialysis. Ultrasound dilution, urea dilution, Doppler ultrasonography, and fistulography are performed on all patients. The accuracy of three non-invasive methods is compared. RESULTS: Fistulography reveals AVF stenosis in 18 patients, 12 of whom have severe stenosis (greater than 50% stenosis in diameter). Concerning the location of the stenosis lesions, eight are at the inflow site, six at the outflow site, and four on both sites. Receiver operating characteristic curve analysis shows that Doppler ultrasonography has a high discriminative ability and the averaged areas under the curves are 0.933 (95% confidence interval [CI]; 0.81 to 0.99) for stenosis and 0.929 (95% CI 0.82-0.99) for severe stenosis. The sensitivity of each method for the prediction of access stenosis using ultrasound dilution, urea dilution, and Doppler ultrasonography is 73%, 73%, and 80%, respectively. The respective specificity of each method is 40%, 80%, and 100%, respectively. Physical examination (PE) shows an 80% sensitivity and 80% specificity in the detection of AVF stenosis. The combination of Doppler ultrasound with PE produces the highest sensitivity (93%) for detecting AVF stenosis. CONCLUSIONS: Doppler ultrasound combined with physical examination is more accurate than other non-invasive methods for detecting AVF stenosis.

Influencia de las venas colaterales en la medición del flujo del acceso vascular medicante ecografía y termodilución: estudio observacional / Influence of collateral veins on flow measurement of vascular access using ultrasound and thermodilution: an observational study

Introducción: La ecografía doppler y métodos dilucionales permiten monitorizar el flujo del acceso vascular. La presencia de venas colaterales podría influir en la determinación del flujo del acceso vascular.Objetivo: Determinar la influencia de las venas colaterales en la medición del flujo del acceso vascular por ecografía doppler y por el método de termodilución.Material y Método: Estudio observacional y prospectivo. Se seleccionaron las fístulas arteriovenosas nativas que cumplían los criterios de selección. Se realizó una medición anual del flujo del acceso vascular mediante ecografía-doppler y 2 mediciones trimestrales de termodilución (termodilución-1 y termodilución-2). Para determinar la presencia de venas colaterales se empleó el ecógrafo.Resultados: Se analizaron 38 fístulas arteriovenosas nativas. Los hombres representaban el 78,9% de la muestra. El 23,6% presentaban venas colaterales. Analizando la totalidad de la muestra, se obtuvo correlación lineal entre los flujos por ecografía-doppler con los de termodilución-1 (0,694) y con termodilución-2 (0,678), ambas p<0,001. Al estratificar por venas colaterales, se observó correlación significativa entre ecografía-doppler con termodilución-1 (0,698) y termodilución-2 (0,696) ambas significativas (p<0,001) cuando no existían venas colaterales, correlación no significativa cuando si había venas colaterales.Conclusiones: Existe correlación entre la medición del flujo del acceso vascular obtenido por ecografía-doppler y termodilución; la presencia de venas colaterales modifica esta relación. Es necesario implementar programas de vigilancia del acceso vascular que incluyan diferentes métodos de monitorización, para mitigar el efecto que las venas colaterales tienen en la determinación del flujo del acceso vascular. (AU)

Introduction: Doppler ultrasound and dilutional methods allow monitoring of vascular access flow. The presence of collateral veins may influence the determination of vascular access flow.Objective: To determine the influence of collateral veins on the vascular access flow measurement by Doppler ultrasound and by the thermodilution method.Material and Method: Observational and prospective study. Native arteriovenous fistulas that met the selection criteria were selected. An annual measurement of vascular access flow by Doppler ultrasound and two quarterly thermodilu-tion measurements (thermodilution-1 and thermodilution-2) were performed. Ultrasound was used to determine the pre-sence of collateral veins.Results: Thirty-eight native arteriovenous fistulae were analysed. Males accounted for 78.9% of the sample. Collateral veins were present in 23.6% of cases. Analysing the whole sample, a linear correlation was obtained between ultrasound-Doppler flows with thermodilution-1 (0.694) and thermodilution-2 (0.678), [both p<0.001]. When stratified by collateral veins, when no collateral veins were present, there was a significant correlation between Doppler ultrasound with thermodilution-1 (0.698) and thermodilution-2 (0.696) [both p<0.001)]; whereas the correlation was non-significant when collateral veins were present.Conclusions: There is correlation between vascular access flow measurement obtained by Doppler ultrasound and thermodilution; the presence of collateral veins modifies such relationship. It is necessary to implement vascular access surveillance programs that include different monitoring methods in order to mitigate the effect of collateral veins on vascular access flow determination. (AU)

Validation of the inverse method for the determination of the access flow with thermodilution.

INTRODUCTION: Thermodiluction is a widely used method for measuring vascular access flow (QA). Among the possibilities of TD, the reverse method (MI) can be beneficial in the execution time, without impact on the dialysis efficacy (Kt). However, it is not a sufficiently studied technique. METHOD: Transversal study of 117 arteriovenous fistulas (AVF). Two QA measurements were taken with the method described by the manufacturer (MR) and another with MI. MI is bases in the obtention of an inverted recirculation registry at the beginning of the session and a single subsequent recirculation measurement with the lines in normal position. In the concordance analysis, the Bland-Altman method and Cohen's Kappa index were used. RESULTS: Very good concordance between MR and MI was evidenced for QA below 700 ml/min, but it worsens as flow increases. The median variability between the MR measurements (intra-method variability) was 3.4% (-17.13). This value did not differ from the median variability generated between MR and MI (inter-method variability), which was 2% (-14, 12) (P = 0.287). The degree of agreement between the two to identify AVFs susceptible to intervention was very good (K = 0.834). The time spent using the MI was significantly shorter (P = 0.000) without evidence of variations in the Kt of the measurement sessions (P = 0.201). CONCLUSIONS: The thermodiluction MI is valid to determine the flow of the vascular access, especially in Qa lower than 700 ml/min, with great time savings, simplification of the procedure and without modifying the dialysis efficiency. The variability between the measurement by MR and MI is similar to that of MR. The concordance between methods in identifying potentially pathological AVFs is very good.

High-flow arteriovenous fistula and myocardial fibrosis in hemodialysis patients with non-contrast cardiac magnetic resonance imaging.

Background: The role of high-flow arteriovenous fistula (AVF) in cardiovascular morbidity in hemodialysis (HD) patients is very likely under-recognized. We assessed the relationship between high access flow (Qa) and myocardial fibrosis in HD patients. Methods: Myocardial fibrosis was assessed by native T1 relaxation times on non-contrast cardiac magnetic resonance imaging and a potential marker of fibrosis. Serum levels of galectin-3, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and monocyte chemoattractant protein 1 (MCP-1) were measured in 101 HD patients who underwent regular monitoring of AVF Qa. A high-flow AVF was defined as a Qa >2 L/min. Results: Hemodialysis patients showed significantly higher galectin-3 value and increased T1 relaxation time compared to healthy volunteers, suggesting increased myocardial fibrosis in uremic cardiomyopathy. In HD patients, 20 (19.8%) had a Qa > 2L/min, and they had significantly higher cardiac output, cardiac index, left ventricular mass, and increased T1 times than those with a Qa ≤ 2 L/min. Also, serum galectin-3 and NT-proBNP levels were much higher in the high Qa group, indicating a close relationship between the high Qa, increased myocardial fibrosis, and the risk of heart failure (HF) in HD patients. It is interesting that a higher AVF Qa for myocardial fibrosis was independent of several traditional cardiovascular risk factors as well as serum levels of NT-proBNP and MCP-1. Conclusions: A supra-physiologically high Qa can be related to myocardial fibrosis and increased risk of HF in HD patients. Regular Qa monitoring could allow early detection of a high-flow AVF that could arise cardiac complications.

Effect and correlation of patent vascular access flow on left ventricular hypertrophy in kidney transplant patients.

Background: Patency of vascular accesses (VA) is associated with left ventricular hypertrophy (LVH) in kidney transplant recipients (KTR). This level of VA flow (VAF) as related to LVH was assessed and an upward level of VA flow recommended for VA closure determined. This recommendation has not been previously reported. Methods: 123 KTR cohort patients were enrolled between August 2016 and December 2017 and their LVH and LV mass index (LVMI) by echocardiography and VAF by Doppler ultrasound were evaluated at baseline and for a 24-month follow-up period. Associations between VAF and LVH were adjusted for other factors. Results: Patients with patent VA (55.3%) had significantly greater LVH (47.1 vs. 29.1%, an adjusted odds ratio 2.44, p = 0.03) and LVMI (112.15 ± 34.4 vs. 97.55 ± 23.55 g/m2, p = 0.009) when compared with the non-VA group. A positive correlation between VAF rate and LVM was noted (r = 0.40, p < 0.001). Subgroup analysis revealed the VAF ≥ 900 ml/min had risks of LVH 3.61, and 2.86 times compared with the non-VA group and the VAF < 900 ml/min group. After a 24-month follow up, there was no significantly individual change in LVMI in patients with or without VA except 6 patients who lost their VA patency during follow-up time had a significant reduction of LVMI (120.17 ± 52.13 to 80.89 ± 22.72 g/m2, p = 0.046). Conclusions: Patency of VA in post-KT patients was associated with LVH. There was a significant reduction of LMVI after loss of VA patency. Patients with stable kidney graft function should be considered for VA closure especially if VAF is ≥ 900 ml/min.

Validación del método inverso para la determinación del flujo de acceso con termodilución / Validation of the inverse method for the determination of the access flow with thermodilution

Introducción: La termodilución es un método ampliamente usado para la medición del flujo de acceso vascular (QA). Entre las posibilidades de la termodilución, el método inverso (MI) puede ser beneficioso en el tiempo de ejecución, sin repercusión en la eficacia dialítica (Kt). Sin embargo, no es una técnica lo suficientemente estudiada.MétodoEstudio transversal sobre 117 fístulas arteriovenosas. Se realizaron 2 mediciones de QA con el método descrito por el fabricante (MR) y otra con MI. El MI se basa en la obtención del registro de recirculación invertida al iniciar la sesión y una única medición posterior de recirculación con las líneas en posición normal. En el análisis de concordancia se utilizó el método Bland-Altman y el índice kappa de Cohen.ResultadosSe evidenció muy buena concordancia entre MR y MI para QA inferiores a 700ml/min, pero empeora a medida que aumenta el flujo. La variabilidad mediana entre las mediciones con MR (variabilidad intramétodo) fue del 3,4% (−17,13). Este valor no difirió de la variabilidad mediana generada entre MR y MI (variabilidad intermétodo), que fue del 2% (−14,12) (p=0,287). El grado de acuerdo entre ambos para identificar fístulas arteriovenosas susceptibles de intervención fue muy bueno (kappa=0,834). El tiempo empleado utilizando el MI fue significativamente menor (p=0,000), sin evidenciarse variaciones en el Kt de las sesiones de medida (p=0,201).ConclusionesEl MI de termodilución es válido para determinar el flujo del acceso vascular, especialmente en QA inferiores a 700ml/min, con gran ahorro de tiempo, simplificación del procedimiento y sin modificar la eficacia de diálisis. La variabilidad entre la medición por MR y MI es similar a la propia del MR. La concordancia entre métodos a la hora de identificar fístulas arteriovenosas potencialmente patológicas es muy buena. (AU)

Introduction: Thermodilution is a widely used method for measuring vascular access flow (QA). Among the possibilities of thermodilution, the reverse method (RM) can be beneficial in the execution time, without impact on the dialysis efficacy (Kt). However, it is not a sufficiently studied technique.MethodTransversal study of 117 arteriovenous fistulas. Two QA measurements were taken with the method described by the manufacturer (MR) and another with RM. RM is based on the obtention of an inverted recirculation registry at the beginning of the session and a single subsequent recirculation measurement with the lines in normal position. In the concordance analysis, the Bland-Altman method and Cohen's Kappa index were used.ResultsVery good concordance between MR and RM was evidenced for QA below 700ml/min, but it worsens as flow increases. The median variability between the MR measurements (intra-method variability) was 3.4% (−17.13). This value did not differ from the median variability generated between MR and RM (inter-method variability), which was 2% (−14,12) (P=.287). The degree of agreement between the 2 to identify arteriovenous fistulas susceptible to intervention was very good (Kappa=0.834). The time spent using the RM was significantly shorter (P=.000) without evidence of variations in the Kt of the measurement sessions (P=.201).ConclusionsThe thermodilution RM is valid to determine the flow of the vascular access, especially in QA lower than 700ml/min, with great time savings, simplification of the procedure and without modifying the dialysis efficiency. The variability between the measurement by MR and RM is similar to that of MR. The concordance between methods in identifying potentially pathological arteriovenous fistulas is very good. (AU)

Access flow volume (Qa) and survival in a haemodialysis population: an analysis of 5208 Qa measurements over a 9-year period.

BACKGROUND: The aim of this study was to determine associations between characteristics of arteriovenous access (AVA) flow volume (Qa; mL/min) and 4-year freedom from cardiovascular mortality (CVM) in haemodialysis (HD) patients. METHODS: HD patients who received a primary AVA between January 2010 and December 2017 in one centre were analysed. Initial Qa was defined as the first Qa value obtained in a well-functioning AVA by a two-needle dilution technique. Actual Qa was defined as access flow at a random point in time. Changes in actual Qa were expressed per 3-month period. CVM was assessed according to the European Renal Association-European Dialysis and Transplant Association classification. The optimal cut-off point for initial Qa was identified by a receiver operating characteristics curve. A joint modelling statistical technique determined longitudinal associations between Qa characteristics and 4-year CVM. RESULTS: A total of 5208 Qa measurements (165 patients; 103 male, age 70 ± 12 years, autologous AVA n = 146, graft n = 19) were analysed. During follow-up (December 2010-January 2018, median 36 months), 79 patients (48%) died. An initial Qa <900 mL/min was associated with an increased 4-y CVM risk {hazard ratio [HR] 4.05 [95% confidence interval (CI) 1.94-8.43], P < 0.001}. After 4 years, freedom from CVM was 34% lower in patients with a Qa <900 mL/min (53 ± 7%) versus a Qa ≥900 mL/min (87 ± 4%; P < 0.001). An association between increases in actual Qa per 3-month period and mortality was found [HR 4.48/100 mL/min (95% CI 1.44-13.97), P = 0.010], indicating that patients demonstrating increasing Qa were more likely to die. In contrast, actual Qa per se was not related to survival. CONCLUSIONS: Studying novel AVA Qa characteristics may contribute to understanding excess CVM in HD patients.

Association of access blood flow with patency loss of arteriovenous fistula in maintenance hemodialysis patients: ultrasound dilution versus color Doppler ultrasound / 中华肾脏病杂志

Objective:To explore the association of access blood flow measured by ultrasound dilution and color Doppler ultrasound with patency loss of arteriovenous fistula (AVF).Methods:This was a bidirectional cohort study. The adult patients who underwent maintenance hemodialysis (MHD) with AVF in Peking University First Hospital from January 1, 2018 to July 31, 2020 were enrolled. AVF blood flow was measured by ultrasonic dilution method (Qa), and color Doppler ultrasound in cephalic vein and brachial artery. Patients were divided into low Qa (<500 ml/min), normal Qa (500-1 500 ml/min) and high Qa (>1 500 ml/min) groups according to baseline AVF blood flow measured by ultrasonic dilution method. Qa was monitored every 3 months within the first year. The endpoint events of follow-up were defined as AVF patency loss or death. The deadline of the follow-up was July 31, 2022. Linear regression analysis was used to assess the change trend of Qa. Fine and Gray competitive risk model was used to evaluate the cumulative incidence of AVF patency loss. The Cox proportional hazards regression model was used to evaluate the association between access AVF blood flow and patency loss.Results:A total of 163 patients were enrolled, with age of (57.0±13.7) years old and 110 males (67.5%). The median follow-up time was 45(22, 53) months. Forty-four patients (27.0%) had AVF failure, and 29 patients (17.8%) died. The cumulative incidence rates of AVF patency loss in patients with low Qa, low blood flow of brachial artery and cephalic vein (<500 ml/min), and in those with a downward trend of Qa were higher than those in patients with normal or high blood flow, and in those with a upward trend of Qa (Gray′s test, all P<0.05). After adjusted for age, sex, age of fistula, diabetes and vascular stenosis, multivariable Cox regression analysis results showed that baseline Qa<500 ml/min ( HR=3.508, 95% CI 1.382-8.905, P=0.008), baseline brachial artery flow<500 ml/min ( HR=2.413, 95% CI 1.058-5.503, P=0.036) and a downward trend of Qa ( HR=2.498, 95% CI 1.241-5.027, P=0.010) were independently associated with AVF patency loss. Conclusions:Patients with low baseline value or downward trend of AVF blood flow are at significantly higher risk of patency loss. The brachial artery measurement of AVF blood flow is the preference location for color Doppler ultrasonic.

Validation of the inverse method for the determination of the access flow with thermodilution. / Validación del método inverso para la determinación del flujo de acceso con termodilución.

INTRODUCTION: Thermodilution is a widely used method for measuring vascular access flow (QA). Among the possibilities of thermodilution, the reverse method (RM) can be beneficial in the execution time, without impact on the dialysis efficacy (Kt). However, it is not a sufficiently studied technique. METHOD: Transversal study of 117 arteriovenous fistulas. Two QA measurements were taken with the method described by the manufacturer (MR) and another with RM. RM is based on the obtention of an inverted recirculation registry at the beginning of the session and a single subsequent recirculation measurement with the lines in normal position. In the concordance analysis, the Bland-Altman method and Cohen's Kappa index were used. RESULTS: Very good concordance between MR and RM was evidenced for QA below 700ml/min, but it worsens as flow increases. The median variability between the MR measurements (intra-method variability) was 3.4% (-17.13). This value did not differ from the median variability generated between MR and RM (inter-method variability), which was 2% (-14,12) (P=.287). The degree of agreement between the 2 to identify arteriovenous fistulas susceptible to intervention was very good (Kappa=0.834). The time spent using the RM was significantly shorter (P=.000) without evidence of variations in the Kt of the measurement sessions (P=.201). CONCLUSIONS: The thermodilution RM is valid to determine the flow of the vascular access, especially in QA lower than 700ml/min, with great time savings, simplification of the procedure and without modifying the dialysis efficiency. The variability between the measurement by MR and RM is similar to that of MR. The concordance between methods in identifying potentially pathological arteriovenous fistulas is very good.

A novel technique of reimplantation of a radial artery that makes a hairpin turn to reduce the excessive vascular access flow in a dialysis patient.

We report a new technique called "reimplantation of an artery with a hairpin turn (RAHT)" to reduce excessive vascular access flow. A 73-year-old woman on dialysis consulted us for vascular surgery because of an increased cardiac preload. Chest radiography and echocardiography revealed an excessive shunt flow in the brachial artery (flow rate, 2336 mL/min). Vascular echo-Doppler of the left upper limb showed that the radial artery made a hairpin turn at the arteriovenous fistula (diameter, 9 mm). Diameters of the radial artery proximal and distal to the arteriovenous fistula were 5.4 and 3.7 mm, respectively. We ligated and divided the juxta-anastomosis proximal radial artery and subsequently created an end-to-side anastomosis between the proximal radial artery and the distal radial artery. The anastomosis ostium in the distal radial artery (the recipient) was formed with a 4-mm longitudinal and gently curved incision. We performed RAHT so that the small anastomosis between both arteries and the small diameter of the distal radial artery juxta-anastomosis segment could reduce the vascular access flow. The flow rates in the brachial artery were 500 mL/min just after surgery and 560 mL/min at 2 months after surgery. Postoperative chest radiography and echocardiography confirmed a decrease in cardiac preload. We believe that this RAHT technique could be useful as one of the options to reduce the flow in patients who have excessive vascular access flow with a radial artery that makes a hairpin turn.

Blood temperature monitoring-guided vascular access intervention improved dialysis adequacy.

OBJECTIVES: The aim of this study was to investigate whether blood temperature monitoring-guided vascular access intervention could improve dialysis adequacy. METHODS: We retrospectively evaluated all patients who received outpatient-based prevalent hemodialysis patients (n = 84) in our artificial kidney room between January 2019 and October 2019. Through blood temperature monitoring, access blood flow was calculated every month and Kt/V was calculated every 3 months. The reference point was set at the time of vascular intervention in the patients (n = 27) who underwent intervention or at the middle of the study period in patients (n = 57) who did not undergo intervention. The mean blood temperature monitoring-estimated access flow and Kt/V before and after the reference point were calculated and compared. RESULTS: Among 84 patients, 30 (35.7%) showed access flow rates of <500 mL/min, calculated by blood temperature monitoring during the study period. Twenty-seven patients (32.1%) underwent vascular intervention, of whom 24 (28.6%) showed access flow rates of <500 mL/min, 2 (2.4%) showed weak bruit or thrill incapable of needling, and 1 (1.2%) presented acute occlusion. Six patients (7.1%) whose access flow rates were <500 mL/min refused to undergo intervention. All angiographies in the patients whose access flow rates were <500 mL/min who underwent intervention showed a significant stenosis. The mean change in blood temperature monitoring-estimated access flow and Kt/V before and after vascular intervention was 483.3 ± 490.6 and 0.19 ± 0.21, respectively, which showed significant differences (all p < 0.05). A weak positive correlation between the mean change in blood temperature monitoring-estimated access flow and Kt/V was shown in all study patients by Pearson's correlation analysis (r = 0.234, p = 0.033). CONCLUSION: Access flow estimation by blood temperature monitoring might identify candidates who require vascular intervention. Blood temperature monitoring-guided vascular intervention significantly improved access flow and dialysis adequacy.

Contribution of inflow artery to observed flow in a vascular access: A computational fluid dynamic modeling study of an arteriovenous fistula circuit.

INTRODUCTION: The volume of blood flowing through the vascular access is an important parameter necessary to provide adequate dialysis for a functional arteriovenous fistula. Higher blood flows are seen in arteriovenous access that receive inflow from larger arteries such as brachial or axillary compared to those based on medium-caliber radial or ulnar arteries. We hypothesized that an anatomic difference in the length and the diameter of the artery is an important determinant of the flow volume in arteriovenous fistula created at different anatomic locations. METHODS: Using computational fluid dynamics, we evaluated the contribution of the length and diameter of inflow artery on simulations performed with geometric models constructed to represent arteriovenous fistula circuits. Lengths and diameters of the inflow artery were altered to mimic arteriovenous fistula created at various locations of the upper extremity with standard and variant anatomy. RESULTS: Models of arteriovenous fistula created with variable lengths and diameters of the inflow artery suggest that the length of the vessel has an inverse linear relationship and the diameter has a direct linear relationship to flow volume. CONCLUSION: Computational fluid dynamic modeling of arteriovenous fistula can be used to understand the physiologic basis of clinical observations of function. Evaluation of the effect of inflow artery length and diameter helps explain the higher flows seen in arteriovenous fistula created using large caliber arteries for inflow. Computational fluid dynamic modeling helps operators understand the contributions of inflow artery in access function and can guide anastomotic site selection.

Effect of Dumbbell Exercise on Arteriovenous Fistula in Patients Undergoing Maintenance Haemodialysis: A Prospective Randomized Controlled Trial.

BACKGROUND: Arteriovenous fistulas (AVF) have been the main vascular accesses for haemodialysis patients, but the maintenance after maturation poses serious challenges. Arm exercises promote the maturation of AVFs. However, few studies have evaluated the effect of arm exercise on matured AVF and addressed the intervention for late fistula failure. OBJECTIVES: The study was conducted to explore the effect of dumbbell exercise on mature AVF. METHODS: 86 participants undergoing haemodialysis with AVFs were randomized into the control group and experimental group. The experimental group held 6-pound dumbbells on non-dialysis days for 3 months, while the control group squeezed rubber balls. RESULTS: For blood flow of draining vein (DV; primary outcome), the between-group effects, interaction effect and time effect showed significant differences. A significant increase in blood flow of DV was observed in the dumbbell group at the 3rd month (mean difference, 359.50 [111.90-829.05] mL/min; p = 0.001). The difference in blood flow of AVF proximal artery, blood flow of brachial artery, the diameter of DV and the incidence of adverse events at 3 months (secondary outcomes) between the 2 groups was insignificant. CONCLUSION: Prolonged training with arm exercises is essential for patients with AVFs though the fistula has matured. The designed dumbbell exercise is an economical, effective intervention to maintain the function of AVF, especially for patients with potential reduction of access blood flow and no percutaneous transluminal angioplasty indication.

Effect of Blood Pump Flow and Arteriovenous Fistula Blood Flow on the Blood Pressure and Cardiac Function in Patients Undergoing Maintenance Hemodialysis.

The effect of blood pump flow rate on the cardiac functions of hemodialysis patients with arteriovenous fistula (AVF) is largely unknown. This study aimed to investigate if blood pump flow rate (Qb) and AVF access flow rate (Qa) can affect the cardiac function of Chinese hemodialysis patients. A total of 72 patients undergoing AVF hemodialysis were included from March 2010 to June 2014 and dichotomized into the high- and low-flow groups using the medians of Qb (220 mL/min) and Qa (1000 mL/min) as the cutoffs. The cardiac function parameters were measured by ultrasound dilution technique within the first (t + 30) and the last (t - 30) 30 min of dialysis. At t + 30, Qb-high group had significantly higher systolic blood pressure (SBP) and mean arterial pressure (MAP) than Qb-low group. At t - 30, Qb-high group had higher SBP, diastolic blood pressure (DBP), and MAP than Qb-low group. Qa-high group had higher SBP, MAP, cardiac output (CO), cardiac index (CI), central blood volume (CBV), and lower peripheral resistance than Qa-low group. Multiple linear regression showed that at t - 30, Qb was positively correlated with SBP and MAP. Qa was positively correlated with CO, CI, CBV, and PR but negatively correlated with heart rate. Although Qb > 220 mL/min and Qa >1000 mL/min would elevate some parameters, the means of SBP, DBP, MAP remain within the normal range, indicating that appropriate increase in blood pump flow rate has little effect on the cardiac function of hemodialysis patients.

Association of vascular access flow with short-term and long-term mortality in chronic haemodialysis patients: a retrospective cohort study.

OBJECTIVES: To investigate the impact of vascular access flow (Qa) on vascular and all-cause mortality in chronic haemodialysis (HD) patients. DESIGN: Observational cohort study. SETTING: Single centre. PARTICIPANTS: Adult chronic HD patients at the HD unit of Shin Kong Wu Ho-Su Memorial Hospital between 1 January 2003 and 31 December 2003 were recruited. Patients were excluded if they had arteriovenous fistula or arteriovenous graft failure within 3 months before the date of Qa measurement, were aged <18 years and had Qa levels of ≥2000mL/min. A total of 378 adult chronic HD patients were eventually enrolled for the study. INTERVENTIONS: The selected patients were evaluated with Qa and cardiac index (CI). They were divided into four groups according to three Qa cut-off points (500, 1000 and 1500 mL/min). PRIMARY AND SECONDARY OUTCOME MEASURES: Short-term and long-term vascular (cardiovascular or cerebrovascular) and all-cause mortality. RESULTS: Qa was positively correlated with CI (r=0.48, p<0.001). A Qa level of <1000 mL/min was independently associated with 1-year all-cause mortality (adjusted OR, 6.04; 95% CI 1.64 to 22.16; p=0.007). Kaplan-Meier analysis revealed that the cumulative incidence rates of all-cause and vascular mortality were significantly higher in the patients with a Qa level of <1000 mL/min (log-rank test; all p<0.01). Furthermore, a Qa level of <1000 mL/min was independently associated with long-term all-cause mortality (adjusted HR, 1.62; 95% CI 1.11 to 2.37; p=0.013); however, the risk of vascular mortality did not significantly increase after adjustment for confounders. CONCLUSIONS: Qa is moderately correlated with cardiac function, and a Qa level of <1000 mL/min is an independent risk factor for both short-term and long-term all-cause mortality in chronic HD patients.

External dilator-assisted banding for high-flow hemodialysis arteriovenous fistula.

Creation of arteriovenous fistula (AVF) may lead to left ventricle hypertrophy and predispose for development or worsening of heart failure. It was postulated to reduce access blood flow if exceeded 2 L/min or cardiac index was higher than 3.0 L/min/m(2). Numbers of techniques decreasing flow were described. The major disadvantage was the complexity of procedure and necessity of intraoperative flow measurement needed to establish desired flow. The technique of dilator-assisted banding with no endovascular catheterization is presented. After blunt dissection non absorbable thread was placed around vessel and tied over the dilator. Then the dilator was gently removed and blood flow was confirmed by palpation. We performed 12 banding procedures. Mean brachial blood flows were 3733.2 ± 826.2 mL/min preoperatively and 1461.2 ± 337.7 mL/min after surgery. Mean flow reduction was 2272.2 ± 726.9 mL/min. The external dilator-assisted banding is a feasible method for vascular access flow reduction without necessity of endovascular catheterization.