Effect of kidney transplantation activity on arteriovenous fistula use in prevalent haemodialysis patients: A registry-based study.

BACKGROUND: Kidney transplantation (KT) is considered to be the best kidney replacement therapy (KRT) option for most end-stage kidney disease (ESKD) patients. Arteriovenous fistula (AVF) is considered to be the best vascular access (VA) for most haemodialysis (HD) patients. In this study, we investigated the effect of KT activity on AVF use in prevalent HD patients. The probability of receiving a kidney graft (KTx) over time, depending on the first VA used to start the HD program, was also evaluated. METHODS: Data from the Catalan Registry of prevalent patients on KRT by either KT or HD were examined over a 20-year period (1997-2017). RESULTS: The percentage of prevalent ESKD patients with a functioning KTx increased from 40.5% in 1997 to 57.0% in 2017 and, conversely, the percentage of AVF utilisation in HD patients decreased from 86.0% to 63.2% during the same period (for both comparisons, p < 0.001). This inverse relationship was also demonstrated in other countries and regions worldwide by performing a simple linear regression analysis (R2 = 0.4974, p = 0.002). The probability of prevalent patients dialysed through an AVF in Catalonia was independently associated with the percentage of functioning KTx among KRT population, after adjusting by age, gender, primary kidney disease, time on KRT, cardiovascular disease and type of HD Unit. Incident patients starting HD through an AVF had a significantly higher probability of receiving a KTx over time in comparison to patients who initiated HD through a catheter (hazard ratio 1.68 [95% confidence interval: 1.41-2.00], p < 0.001). CONCLUSIONS: In addition to some demographical and clinical characteristics of patients and type of HD Unit, KT activity can be a determining factor in AVF use in prevalent HD patients. Starting an HD programme through an AVF is independently associated with a greater probability of receiving a KTx as compared to starting HD through a catheter.

Changes in vascular access profile for pediatric hemodialysis patients over time: A registry-based study from Catalonia.

BACKGROUND: The criteria for vascular access (VA) selection in pediatric hemodialysis (HD) population has changed over time until the current patient-centered approach using the individualized Life-Plan. We analyzed the type of VA used by incident and prevalent end-stage kidney disease (ESKD) pediatric patients (pts) treated with HD in Catalonia. METHOD: Data from the Catalan Renal Registry of ESKD pts under 18 years of age undergoing kidney replacement therapy (KRT) were examined for a 22-year period (1997-2018). RESULTS: ESKD children starting KRT through HD decreased progressively from 55.6% (1997-2001) to 38.2% (2012-2018) and, conversely, there was an increase in pts starting KRT by preemptive kidney transplantation (KT) from 28.9% to 42.6% between the same periods (for both comparisons, p = 0.007). Most ESKD pts started HD by fistula (AVF) from 1997 to 2001 (56.5%) but this percentage decreased over time and no AVFs were used to start HD in children from 2012 to 2018. Likewise, the percentage of children starting HD by tunneled catheter increased progressively from 8.7% to 72.2% between the same periods (for both comparisons, p < 0.001). Regarding prevalent ESKD pts, children on HD decreased from 34.9% in 1997 to 4.7% in 2018 and, conversely, pts with a functioning kidney graft increased from 62.8% to 92.4% during the same periods (for both comparisons, p < 0.001). There was a progressive decrease in the percentage of children dialyzed by AVF from 100% in 1997 to 0% in 2018 (p < 0.001). The KT rate increased from 5.4 per million population (pmp) in 1997 to 17.1 pmp in 2018 (p = 0.007). The median time on HD prior to the first KT progressively decreased to 6.6 months (2014-2018). CONCLUSION: The high KT rate was a determining factor in choosing the VA type in the incident and prevalent pediatric population treated with HD in Catalonia.

Is fetuin-A a biomarker of dialysis access dysfunction?

BACKGROUND: The arteriovenous (AV) access function of hemodialysis (HD) patients can be impaired by afferent artery stiffness due to preexisting microcalcification and by venous stenosis secondary to neointimal hyperplasia in whose development participates an upregulated local inflammatory process. Fetuin-A is a circulating potent inhibitor of vascular calcification and plays an important anti-inflammatory role. The aims of this prospective study were to investigate the relationship between baseline serum fetuin-A levels and: blood flow (QA) values at baseline, AV access failure (thrombosis or intervention for stenosis) during follow-up and primary unassisted AV access patency. METHODS: We measured baseline serum fetuin-A levels and QA values of the AV access in 64 HD patients under routine QA surveillance for stenosis. Patients were classified into tertiles according to their baseline fetuin-A levels (g/L): <0.5 (tertile-1), 0.5-1.20 (tertile-2), and >1.20 (tertile-3). RESULTS: Fetuin-A was positively correlated with QA (Spearman coefficient = 0.311, p = 0.012). Fourteen patients (21.9%) underwent AV access failure and they had lower fetuin-A (0.59 ± 0.32 g/L) and lower QA (739.4 ± 438.8 mL/min) values at baseline compared with the remaining patients (1.05 ± 0.65 g/L and 1273.0 ± 596.3 mL/min, respectively) (p = 0.027 and p < 0.001, respectively). The AV access failure rate was highest (34.8%) in tertile-1 (lowest fetuin-A level). Unadjusted Cox regression analysis showed a decrease in the risk of AV access patency loss by increasing fetuin-A concentration (hazard ratio 0.395 (95% confidence interval: 1.42-1.69), p = 0.044) but it was not confirmed in the adjusted model, although the hazard ratio was low (0.523). Kaplan-Meier analysis showed that patients in tertile-3 (highest fetuin-A concentration) had the highest primary unassisted AV access patency (λ2 = 4.68, p = 0.030, log-rank test). CONCLUSION: If our results are confirmed in further studies, fetuin-A could be used as a circulating biomarker to identify HD patients at greater risk for AV access dysfunction, who would benefit from much closer dialysis access surveillance.

Haemodialysis access profile in failed kidney transplant patients: Analysis of data from the Catalan Renal Registry (1998-2016).

BACKGROUND: Data about vascular access (VA) use in failed kidney transplant (KT) patients returning to haemodialysis (HD) are limited. We analysed the VA profile of these patients, the factors associated with the likelihood of HD re-initiation through fistula (AVF) and the effect of VA in use at the time of KT on kidney graft (KTx) outcome. METHOD: Data from the Catalan Registry on failed KT patients restarting HD and incident HD patients with native kidney failure were examined over an 18-year period. RESULTS: The VA profile of 675 failed KT patients at HD re-initiation compared with that before KT and with 16,731 incident patients starting HD was (%): AVF 79.3 versus 88.6 and 46.2 (p = 0.001 and p < 0.001), graft AVG 4.4 versus 2.6 and 1.1 (p = 0.08 and p < 0.001), tunnelled catheter TCC 12.4 versus 5.5 and 18.0 (p = 0.001 and p < 0.001) and non-tunnelled catheter 3.9 versus 3.3 and 34.7 (p = 0.56 and p < 0.001). The likelihood of HD re-initiation by AVF was significantly lower in patients with cardiovascular disease, KT duration >5 years, dialysed through AVG or TCC before KT, and females. The analysis of Kaplan-Meier curves showed a greater KTx survival in patients dialysed through arteriovenous access than in patients using catheter just before KT (λ2 = 5.59, p = 0.0181, log-rank test). Cox regression analysis showed that patients on HD through arteriovenous access at the time of KT had lower probability of KTx loss compared to those with catheter (hazard ratio 0.71, 95% CI 0.55-0.90, p = 0.005). CONCLUSIONS: The VA profile of failed KT patients returning to HD and incident patients starting HD was different. Compared to before KT, the proportion of failed KT patients restarting HD with AVF decreased significantly at the expense of TCC. Patients on HD through arteriovenous access at the time of KT showed greater KTx survival compared with those using catheter.

Hemodialysis vascular access affects heart function and outcomes: Tips for choosing the right access for the individual patient.

Chronic kidney disease is associated with increased cardiovascular morbidity and mortality. A well-functioning vascular access is associated with improved survival and among the available types of vascular access the arterio-venous (AV) fistula is the one associated with the best outcomes. However, AV access may affect heart function and, in some patients, could worsen the clinical status. This review article focuses on the specific cardiovascular hemodynamics of dialysis patients and how it is affected by the AV access; the effects of an excessive increase in AV access flow, leading to high-output heart failure; congestive heart failure in CKD patients and the contraindications to AV access; pulmonary hypertension. In severe heart failure, peritoneal dialysis (PD) might be the better choice for cardiac health, but if contraindicated suggestions for vascular access selection are provided based on the individual clinical presentation. Management of the AV access after kidney transplantation is also addressed, considering the cardiovascular benefit of AV access ligation compared to the advantage of having a functioning AVF as backup in case of allograft failure. In PD patients, who need to switch to hemodialysis, vascular access should be created timely. The influence of AV access in patients undergoing cardiac surgery for valvular or ischemic heart disease is also addressed. Cardiovascular implantable electronic devices are increasingly implanted in dialysis patients, but when doing so, the type and location of vascular access should be considered.

Quality assessment of vascular access procedures for hemodialysis: A position paper of the Vascular Access Society based on the analysis of existing guidelines.

Quality assessment in vascular access procedures for hemodialysis is not clearly defined. The aim of this article is to compare various guidelines regarding recommendation on quality control in angioaccess surgery. The overall population of end-stage renal disease patients and patients in need for hemodialysis treatment is growing every year. Chronic intermittent hemodialysis is still the main therapy. The formation of a functional angioaccess is the cornerstone in the management of those patients. Native (autologous) arteriovenous fistula is the best vascular access available. A relatively high percentage of primary failure and fistula abandonment increases the need for quality control in this field of surgery. There are very few recommendations of quality assessment on creation of a vascular access for hemodialysis in the searched guidelines. Some guidelines recommend the proportion of native arteriovenous fistula in incident and prevalent patients as well as the maximum tolerable percentage of central venous catheters and complications. According to some guidelines, surgeon's experience and expertise have a considerable influence on outcomes. There are no specific recommendations regarding surgeon's specialty, grade, level of skills, and experience. In conclusion, there is a weak recommendation in the guidelines on quality control in vascular access surgery. Quality assessment criteria should be defined in this field of surgery. According to these criteria, patients and nephrologists could choose the best vascular access center or surgeon. Centers with best results should be referral centers, and centers with poorer results should implement quality improvement programs.

Consensus document for ultrasound training in the specialty of Nephrology. / Documento de consenso para la formación en ecografía en la especialidad de Nefrología.

Ultrasound is an essential tool in the management of the nephrological patient allowing the diagnosis, monitoring and performance of kidney intervention. However, the usefulness of ultrasound in the hands of the nephrologist is not limited exclusively to the ultrasound study of the kidney. By ultrasound, the nephrologist can also optimize the management of arteriovenous fistula for hemodialysis, measure cardiovascular risk (mean intimate thickness), implant central catheters for ultrasound-guided HD, as well as the patient's volemia using basic cardiac ultrasound, ultrasound of the cava inferior vein and lungs. From the Working Group on Interventional Nephrology (GNDI) of the Spanish Society of Nephrology (SEN) we have prepared this consensus document that summarizes the main applications of ultrasound to Nephrology, including the necessary basic technical requirements, the framework normative and the level of training of nephrologists in this area. The objective of this work is to promote the inclusion of ultrasound, both diagnostic and interventional, in the usual clinical practice of the nephrologist and in the Nephrology Services portfolio with the final objective of offering diligent, efficient and comprehensive management to the nephrological patient.

The impact of pre-existing radial artery pathology by histological assessment on the maturation, function and patency of the radiocephalic fistula for hemodialysis.

BACKGROUND: We prospectively analyzed the effect of preexisting structural changes of the radial artery (RA) wall by histological examination on the wrist radiocephalic fistula (RCF) outcomes. METHODS: During RCF creation, one segment of the RA wall was collected and its histomorphometric analysis was performed. The RCF function was evaluated by measuring blood flow rate. RESULTS: At the end of follow-up, 75.7% of the thirty-seven patients enrolled were performing hemodialysis by using their successful RCF and 24.3% of them showed early RCF failure. Compared to patients with a healthy RA, the RCF of those with medial RA microcalcification reached up a lower flow and a shorter primary patency (P=0.005 and P=0.040, respectively). The RA microcalcification was predictive of the RCF function (coefficient -614.9, 95% CI: -994.7 to -235.1, P=0.003). Compared to patients with successful RCF, those with failed RCF had a greater frequency of weak RCF thrill after releasing the clamps (P=0.045). Dependence on hemodialysis during RCF placement was predictive of its early failure (OR: 23.2, 95% CI: 1.76 to 306.9, P=0.017). Both having at least one cardiovascular comorbidity (HR 4.30, 95% CI: 1.29 to 14.39, P=0.018) and a thicker media layer of the RA (HR 1.60, 95% CI: 1.87 to 2.15, P=0.002) were predictive of primary RCF patency. CONCLUSIONS: The function and survival of the successful RCF were related to preoperative RA abnormalities such as microcalcification and media layer thickness. Both dependence on hemodialysis during RCF placement and an attenuated RCF thrill were associated with early RCF failure.

Diagnostic and Interventional Nephrology in Spain: A snapshot of current situation.

BACKGROUND:: Diagnostic and Interventional Nephrology has been a rising field in recent years worldwide. Catheter insertion, renal biopsy, renal ultrasound, and peritoneal dialysis catheter or permanent dialysis catheter insertion are vital to our specialty. At present, many of these procedures are delegated to other specialties, generating long waiting lists and limiting diagnosis and treatment. METHODS:: An online survey was emailed to all Nephrology departments in Spain. One survey response was allowed per center. RESULTS:: Of 195 Nephrology departments, 70 responded (35.8%). Of them, 72.3% (52) had ultrasound equipment, 77.1% insert temporary jugular catheters, and 92.8% femoral. Up to 75.7% (53 centers) perform native renal biopsies, of which 35.8% (19) are real-time ultrasound guided by nephrologists. Transplant kidney biopsies are done in 26 centers, of which 46.1% (12) by nephrologists. Tunneled hemodialysis catheters are inserted in 27 centers (38.5%), peritoneal catheter insertion in 18 (31.6%), and only 2 centers (2.8%) perform arteriovenous fistulae angioplasty. In terms of ultrasound imaging, 20 centers (28.5%) do native renal ultrasound and 16 (22.8%) transplanted kidneys. Of all units 71.4% offer carotid ultrasound to evaluate cardiovascular risk, only in 15 centers (21%) by nephrologists. AVF ultrasound scanning is done in 55.7% (39). CONCLUSION:: Diagnostic and Interventional Nephrology is slowly spreading in Spain. It includes basic techniques to our specialty, allowing nephrologists to be more independent, efficient, and reducing waiting times and costs, overall improving patient care. Nowadays, more nephrologists aim to perform them. Therefore, appropriate training on different techniques should be warranted, implementing an official certification and teaching programs.

Dialysis arteriovenous access monitoring and surveillance according to the 2017 Spanish Guidelines.

The Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology (S.E.N.), vascular surgery (SEACV), interventional radiology (SERAM-SERVEI), infectious diseases (SEIMC), and nephrology nursing (SEDEN)), along with the methodological support of the Iberoamerican Cochrane Centre, has developed the Spanish Clinical Guidelines on Vascular Access for Hemodialysis. This article summarizes the main issues from the guideline's chapter entitled "Monitoring and surveillance of arteriovenous access." We will analyze the current evidence on conflicting topics such as the value of the flow-based screening methods for the arteriovenous access surveillance or the role of Doppler ultrasound as the imaging exploration to confirm suspected stenosis. In addition, the concept of significant stenosis and the criteria to perform the elective intervention for stenosis were reviewed. The adoption of these guidelines will hopefully translate into a reduced risk of thrombosis and increased patency rates for both arteriovenous fistulas and grafts.

Adding access blood flow surveillance reduces thrombosis and improves arteriovenous fistula patency: a randomized controlled trial.

PURPOSE: Stenosis is the main cause of arteriovenous fistula (AVF) failure. It is still unclear whether surveillance based on vascular access blood flow (QA) enhances AVF function and longevity. METHODS: We conducted a three-year follow-up randomized, controlled, multicenter, open-label trial to compare QA-based surveillance and pre-emptive repair of subclinical stenosis with standard monitoring/surveillance techniques in prevalent mature AVFs. AVFs were randomized to either the control group (surveillance based on classic alarm criteria; n = 104) or to the QA group (QA measured quarterly using Doppler ultrasound [M-Turbo®] and ultrasound dilution [Transonic®] added to classic surveillance; n = 103).The criteria for intervention in the QA group were: 25% reduction in QA, QA<500 mL/min or significant stenosis with hemodynamic repercussion (peak systolic velocity [PSV] more than 400 cm/sc or PSV pre-stenosis/stenosis higher than 3). RESULTS: At the end of follow-up we observed a significant reduction in the thrombosis rate in the QA group (0.025 thrombosis/patient/year in the QA group vs. 0.086 thrombosis/patient/year in the control group [p = 0.007]). There was a significant improvement in the thrombosis-free patency rate (HR, 0.30; 95% CI, 0.11-0.82; p = 0.011) and in the secondary patency rate in the QA group (HR, 0.49; 95% CI, 0.26-0.93; p = 0.030), with no differences in the primary patency rate between the groups (HR, 0.98; 95% CI, 0.57-1.61; p = 0.935).There was greater need for a central venous catheter and more hospitalizations associated with vascular access in the control group (p = 0.034/p = 0.029).Total vascular access-related costs were higher in the control group (€227.194 vs. €133.807; p = 0.029). CONCLUSIONS: QA-based surveillance combining Doppler ultrasound and ultrasound dilution reduces the frequency of thrombosis, is cost effective, and improves thrombosis free and secondary patency in autologous AVF.

Spanish Clinical Guidelines on Vascular Access for Haemodialysis. / Guía Clínica Española del Acceso Vascular para Hemodiálisis.

Vascular access for haemodialysis is key in renal patients both due to its associated morbidity and mortality and due to its impact on quality of life. The process, from the creation and maintenance of vascular access to the treatment of its complications, represents a challenge when it comes to decision-making, due to the complexity of the existing disease and the diversity of the specialities involved. With a view to finding a common approach, the Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology [S.E.N.], vascular surgery [SEACV], vascular and interventional radiology [SERAM-SERVEI], infectious diseases [SEIMC] and nephrology nursing [SEDEN]), along with the methodological support of the Cochrane Center, has updated the Guidelines on Vascular Access for Haemodialysis, published in 2005. These guidelines maintain a similar structure, in that they review the evidence without compromising the educational aspects. However, on one hand, they provide an update to methodology development following the guidelines of the GRADE system in order to translate this systematic review of evidence into recommendations that facilitate decision-making in routine clinical practice, and, on the other hand, the guidelines establish quality indicators which make it possible to monitor the quality of healthcare.

Permanent arteriovenous fistula or catheter dialysis for heart failure patients.

Heart failure (HF) is the most frequent cardiovascular disease associated with chronic kidney disease and represents a high risk for cardiovascular mortality in incident hemodialysis (HD) patients. This risk is especially high during the arteriovenous fistula (AVF) maturation period due to the marked hemodynamic changes related to the large increase in the blood flow and also within the first 120 days after HD inception because in this period the highest mortality rate occurs. When planning the vascular access for each incident HF patient, the risk of aggravating HF after AVF creation must be evaluated carefully alongside the risk of catheter-related complications, but avoiding a non-selective 'catheter first' approach for all these patients. HF patients classified within the New York Heart Association (NYHA) Class I-II and the American College of Cardiology/American Heart Association (ACC/AHA) Stage A-B could initiate HD through a distal arm AVF. High-flow brachial artery-based AVF creation must be avoided because it displays the highest risk of worsening the cardiac function. The decision for AVF creation or tunneled central catheter placement in HF patients classified within the NYHA Class III and the ACC/AHA Stage C must have been individualized according the degree of systolic and/or diastolic dysfunction. HF patients with significant reduction in systolic function (ejection fraction lower than 30%) or classified within the NYHA Class IV and the ACC/AHA Stage D, are candidates for tunneled catheter placement to start HD treatment.

Starting hemodialysis with catheter and mortality risk: persistent association in a competing risk analysis.

PURPOSE: The vascular access (VA) used at hemodialysis (HD) inception is involved in the mortality risk. We analyzed the survival of incident patients over time according to the initial VA and the VA profile of patients who died during the first year of follow-up. METHODS: Data of VA were obtained from 9956 incident HD patients from the Catalan Registry. RESULTS: Over 12 years, 47.9% of patients initiated HD with a fístula, 1.2% with a graft, 15.9% with a tunneled catheter and 35% with an untunneled catheter. Regarding fistula use, the hazard ratio of death for all-causes over time when applying a multivariate competing risk model was 1.55 [95% confidence interval (CI): 1.42-1.69] and 1.43 (95% CI: 1.33-1.54) for patients with tunneled and untunneled catheter, respectively. During the first year of follow-up, the crude all-cause mortality rate (deaths/100 patient-years) was higher during the early (first 120 days) compared to the late (121-365 days) period: 18.3 (95% CI: 16.8-19.8) versus 15.4 (95% CI: 14.5-16.5). Regarding fistula use, for patients using untunneled and tunneled catheter, the odds ratio of death in the early period for all-causes was 3.66 (95% CI: 2.80-4.81) and 2.97 (95% CI: 2.17-4.06), for cardiovascular causes it was 2.76 (95% CI: 1.90-4.01) and 1.84 (95% CI: 1.17-2.89) and for infection-related causes it was 6.62 (95% CI: 3.11-14.05) and 4.58 (95% CI: 2.00-10.52), respectively. CONCLUSIONS: Half of all incident patients in Catalonia are exposed to excessive mortality risk related to catheter and this scenario can be improved by early fistula placement.

The impact of access blood flow surveillance on reduction of thrombosis in native arteriovenous fistula: a randomized clinical trial.

PURPOSE: The usefulness of access blood flow (QA) measurement is an ongoing controversy. Although all vascular access (VA) clinical guidelines recommend monitoring and surveillance protocols to prevent VA thrombosis, randomized clinical trials (RCTs) have failed to consistently show the benefits of QA-based surveillance protocols. We present a 3-year follow-up multicenter, prospective, open-label, controlled RCT, to evaluate the usefulness of QA measurement using Doppler ultrasound (DU) and ultrasound dilution method (UDM), in a prevalent hemodialysis population with native arteriovenous fistula (AVF). METHODS: Classical monitoring and surveillance methods are applied in all patients, the control group (n = 98) and the QA group (n = 98). Besides this, DU and UDM are performed in the QA group every three months. When QA is under 500 ml/min or there is a >25% decrease in QA the patient goes for fistulography, surgery or close clinical/surveillance observation. Thrombosis rate, assisted primary patency rate, primary patency rate and secondary patency rate are measured. RESULTS: After one-year follow-up we found a significant reduction in thrombosis rate (0.022 thrombosis/patient/year at risk in the QA group compared to 0.099 thrombosis/patient/year at risk in the control group [p = 0.030]). Assisted primary patency rate was significantly higher in the QA group than in control AVF (hazard ratio [HR] 0.23, 95% confidence interval [CI] 0.05-0.99; p = 0.030). In the QA group, the numbers unddergoing angioplasty and surgery were higher but with no significant difference in non-assisted primary patency rate (HR 1.41, 95% CI 0.72-2.84; p = 0.293). There was a non-significant improvement in secondary patency rate in the QA group (HR 0.510, 95% CI 0.17-1.50; p = 0.207). CONCLUSIONS: The measurement of QA combining DU and UDM shows a reduction in thrombosis rate and an increased assisted primary patency rate in AVF after one-year follow-up. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02111655.