Should a fistula first policy be revisited in elderly haemodialysis patients?

Life-sustaining haemodialysis requires a durable vascular access (VA) to the circulatory system. The ideal permanent VA must provide longevity for use with minimal complication rate and supply sufficient blood flow to deliver the prescribed dialysis dosage. Arteriovenous fistulas (AVFs) have been endorsed by many professional societies as the VA of choice. However, the high prevalence of comorbidities, particularly diabetes mellitus, peripheral vascular disease and arterial hypertension in elderly people, usually make VA creation more difficult in the elderly. Many of these patients may have an insufficient vasculature for AVF maturation. Furthermore, many AVFs created prior to the initiation of haemodialysis may never be used due to the competing risk of death before dialysis is required. As such, an arteriovenous graft and, in some cases, a central venous catheter, become a valid alternative form of VA. Consequently, there are multiple decision points that require careful reflection before an AVF is placed in the elderly. The traditional metrics of access patency, failure and infection are now being seen in a broader context that includes procedure burden, quality of life, patient preferences, morbidity, mortality and cost. This article of the European Dialysis (EUDIAL) Working Group of ERA-EDTA critically reviews the current evidence on VA in elderly haemodialysis patients and concludes that a pragmatic patient-centred approach is mandatory, thus considering the possibility that the AVF first approach should not be an absolute.

The complex relationship among arteriovenous access, heart, and circulation.

There are currently near 400 000 patients on hemodialysis in the United States. More than 50% of those treated by chronic hemodialysis die because of a cardiovascular (CV) event. The majority of these patients have functional arteriovenous fistulas (AVFs). AVFs have an adverse effect on cardiac function, but their exact contribution to CV morbidity is not clear. It has long been known that a vascular access with an inappropriately high-flow rate may cause high-output heart failure. Paradoxically, there may be hemodynamic and cardiopulmonary benefits conferred by AVF particularly in severe chronic obstructive pulmonary disease. While Brescia-Cimino`s basic idea of the AVF has saved millions of lives, we would like to stress that there are dangers from their often high blood flow rates, which unfortunately have proved difficult to evaluate.

Dialysate bicarbonate concentration: Too much of a good thing?

Acid-base equilibrium is a complex and vital system whose regulation is impaired in chronic kidney disease (CKD). Metabolic acidosis is a common complication of CKD. It is typically due to the accumulation of sulfate, phosphorus, and organic anions. Metabolic acidosis is correlated with several adverse outcomes, such as morbidity, hospitalization and mortality. In patients undergoing hemodialysis, acid-base homeostasis depends on many factors: net acid production, amount of alkali given by the dialysate bath, duration of interdialytic period, as well as residual diuresis, if any. Recent literature data suggest that the development of postdialysis metabolic alkalosis may contribute to adverse clinical outcomes. Unfortunately, no randomized studies exist about the effect of different dialysate bicarbonate concentrations on hard outcomes, such as mortality. Like everything else in dialysis, the quest for the "ideal" dialysate bicarbonate concentration is far from over. The Latin aphorism "ne quid nimis" ie "nothing in excess" (excess of neither acid nor base) probably best summarizes our current state of knowledge in this field. For the present, the clinician should understand that target values for predialysis serum bicarbonate concentrations have been established primarily based on observational studies and expert opinion. On the basis of this information, we should keep predialysis serum bicarbonate concentrations at least at 22 mEq/L. Furthermore, a specific focus should be addressed to the clinical and nutritional status of the major outliers on both the acid and alkaline sides of the curve.

The function of the parathyroid oxyphil cells in uremia: still a mystery?

Parathyroid glands of young adults consist primarily of chief cells. However, with age or after excessive functional stress, another cell type increases progressively-the oxyphil cell. There is evidence for a chief-to-oxyphil cell transdifferentiation in chronic kidney disease. The latter may represent a defense mechanism, transforming the actively secreting chief cells to a less actively secreting cell type. However, even if this strategy is able to delay the development of secondary hyperparathyroidism, it cannot prevent it.

Clinical use of computational modeling for surgical planning of arteriovenous fistula for hemodialysis.

BACKGROUND: Autogenous arteriovenous fistula (AVF) is the best vascular access (VA) for hemodialysis, but its creation is still a critical procedure. Physical examination, vascular mapping and doppler ultrasound (DUS) evaluation are recommended for AVF planning, but they can not provide direct indication on AVF outcome. We recently developed and validated in a clinical trial a patient-specific computational model to predict pre-operatively the blood flow volume (BFV) in AVF for different surgical configuration on the basis of demographic, clinical and DUS data. In the present investigation we tested power of prediction and usability of the computational model in routine clinical setting. METHODS: We developed a web-based system (AVF.SIM) that integrates the computational model in a single procedure, including data collection and transfer, simulation management and data storage. A usability test on observational data was designed to compare predicted vs. measured BFV and evaluate the acceptance of the system in the clinical setting. Six Italian nephrology units were involved in the evaluation for a 6-month period that included all incident dialysis patients with indication for AVF surgery. RESULTS: Out of the 74 patients, complete data from 60 patients were included in the final dataset. Predicted brachial BFV at 40 days after surgery showed a good correlation with measured values (in average 787 ± 306 vs. 751 ± 267 mL/min, R = 0.81, p < 0.001). For distal AVFs the mean difference (±SD) between predicted vs. measured BFV was -2.0 ± 20.9%, with 50% of predicted values in the range of 86-121% of measured BFV. Feedbacks provided by clinicians indicate that AVF.SIM is easy to use and well accepted in clinical routine, with limited additional workload. CONCLUSIONS: Clinical use of computational modeling for AVF surgical planning can help the surgeon to select the best surgical strategy, reducing AVF early failures and complications. This approach allows individualization of VA care, with the aim to reduce the costs associated with VA dysfunction, and to improve AVF clinical outcome.

The choice of dialysate bicarbonate: do different concentrations make a difference?

Metabolic acidosis is a common complication of chronic kidney disease; it is typically caused by the accumulation of sulfate, phosphorus, and organic anions. Metabolic acidosis is correlated with several adverse outcomes, such as morbidity, hospitalization, and mortality. Thus, correction of metabolic acidosis is fundamental for the adequate management of many systemic complications of chronic kidney disease. In patients undergoing hemodialysis, acid-base homeostasis depends on many factors including the following: net acid production, amount of alkali given by the dialysate bath, duration of the interdialytic period, and residual diuresis, if any. Recent literature data suggest that the development of metabolic alkalosis after dialysis may contribute to adverse clinical outcomes. Our review is focused on the potential effects of different dialysate bicarbonate concentrations on hard outcomes such as mortality. Unfortunately, no randomized studies exist about this issue. Acid-base equilibrium is a complex and vital system whose regulation is impaired in chronic kidney disease. We await further studies to assess the extent to which acid-base status is a major determinant of overall survival in patients undergoing hemodialysis. For the present, the clinician should understand that target values for predialysis serum bicarbonate concentration have been established primarily based on observational studies and expert opinion. Based on this, we should keep the predialysis serum bicarbonate level at least at 22 mmol/l. Furthermore, a specific focus should be addressed by the attending nephrologist to the clinical and nutritional status of the major outliers on both the acid and alkaline sides of the curve.

High versus low dialysate sodium concentration in chronic haemodialysis patients: a systematic review of 23 studies.

BACKGROUND: It is the object of debate whether a low or high dialysate sodium concentration (DNa(+)) should be advocated in chronic haemodialysis patients. In this paper, we aimed at evaluating benefits and harms of different DNa(+) prescriptions through a systematic review of the available literature. METHODS: MEDLINE and CENTRAL databases were searched for studies comparing low or high DNa(+) prescriptions. Outcomes of interest were mortality, blood pressure (BP), interdialytic weight gain (IDWG), plasma sodium, hospitalizations, use of anti-hypertensive agents and intradialytic complications. RESULTS: Twenty-three studies (76 635 subjects) were reviewed. There was high heterogeneity in the number of patients analysed, overall study quality, duration of follow-up, DNa(+) and even in the definition of 'high' or 'low' DNa(+). The only three studies looking at mortality were observational. The risk of death was related to the plasma-DNa(+) gradient, but was also shown to be confounded by indication from the dialysate sodium prescription itself. BP was not markedly affected by high or low DNa(+). Patients treated with higher DNa(+) had overall higher IDWG when compared with those with lower DNa(+). Three studies reported a significant increase in intra-dialytic hypotensive episodes in patients receiving low DNa(+). Data on hospitalizations and use of anti-hypertensive agents were sparse and inconclusive. CONCLUSIONS: There is currently no definite evidence proving the superiority of a low or high uniform DNa(+) on hard or surrogate endpoints in maintenance haemodialysis patients. Future trials adequately powered to evaluate the impact of different DNa(+) on mortality or other patient-centred outcomes are needed.

It is Time to Individualize the Dialysate Sodium Prescription.

Sodium mass balance in hemodialysis patients is primarily dependent on dietary salt intake and sodium removal during dialysis. One of the most important goals of dialysis therapy is to fully remove the mass of sodium that has accumulated in the interdialytic period. It is currently the practice in dialysis centers all over the world to use a standardized dialysate sodium concentration (Na(+) D) for all patients. The aim of the present article was to summarize the current evidence for an individualized Na(+) D prescription. Three main points are discussed: (i) Na(+) D prescription, which must necessarily take into account the sodium setpoint and the sodium gradient; (ii) clinical experience with an individualized Na(+) D prescription, and (iii) guidelines for individualizing the Na(+) D prescription. To summarize, recent data suggest that tailoring Na(+) D to an individual's sodium setpoint has the potential for short- and long-term benefits for patients. Prospective interventional studies are warranted to further understand its effects, stratified for patients with low or high serum sodium levels.

Ranking of factors determining potassium mass balance in bicarbonate haemodialysis.

BACKGROUND: One of the most important pathogenetic factors involved in the onset of intradialysis arrhytmias is the alteration in electrolyte concentration, particularly potassium (K(+)). METHODS: Two studies were performed: Study A was designed to investigate above all the isolated effect of the factor time t on intradialysis K(+) mass balance (K(+)MB): 11 stable prevalent Caucasian anuric patients underwent one standard (∼4 h) and one long-hour (∼8 h) bicarbonate haemodialysis (HD) session. The latter were pair-matched as far as the dialysate and blood volume processed (90 L) and volume of ultrafiltration are concerned. Study B was designed to identify and rank the other factors determining intradialysis K(+)MB: 63 stable prevalent Caucasian anuric patients underwent one 4-h standard bicarbonate HD session. Dialysate K(+) concentration was 2.0 mmol/L in both studies. Blood samples were obtained from the inlet blood tubing immediately before the onset of dialysis and at t60, t120, t180 min and at end of the 4- and 8-h sessions for the measurement of plasma K(+), blood bicarbonates and blood pH. Additional blood samples were obtained at t360 min for the 8 h sessions. Direct dialysate quantification was utilized for K(+)MBs. Direct potentiometry with an ion-selective electrode was used for K(+) measurements. RESULTS: Study A: mean K(+)MBs were significantly higher in the 8-h sessions (4 h: -88.4 ± 23.2 SD mmol versus 8 h: -101.9 ± 32.2 mmol; P = 0.02). Bivariate linear regression analyses showed that only mean plasma K(+), area under the curve (AUC) of the hourly inlet dialyser diffusion concentration gradient of K(+) (hcgAUCK(+)) and AUC of blood bicarbonates and mean blood bicarbonates were significantly related to K(+)MB in both 4- and 8-h sessions. A multiple linear regression output with K(+)MB as dependent variable showed that only mean plasma K(+), hcgAUCK(+) and duration of HD sessions per se remained statistically significant. Study B: mean K(+)MBs were -86.7 ± 22.6 mmol. Bivariate linear regression analyses showed that only mean plasma K(+), hcgAUCK(+) and mean blood bicarbonates were significantly related to K(+)MB. Again, only mean plasma K(+) and hcgAUCK(+) predicted K(+)MB at the multiple linear regression analysis. CONCLUSIONS: Our studies enabled to establish the ranking of factors determining intradialysis K(+)MB: plasma K(+) → dialysate K(+) gradient is the main determinant; acid-base balance plays a much less important role. The duration of HD session per se is an independent determinant of K(+)MB.

The key role of color Doppler ultrasound in the work-up of hemodialysis vascular access.

Vascular access (VA) is the lifeline for the hemodialysis patient and the native arterio-venous fistula (AVF) is the first-choice access. Among the different tests used in the VA domain, color Doppler ultrasound (CD-US) plays a key role in the clinical work-up. At the present time, three are the main fields of CD-US application: (i) evaluation of forearm arteries and veins in surgical planning; (ii) testing of AVF maturation; (iii) VA complications. Specifically, during the AVF maturation, CD-US allows to measure the diameter and flow volume in the brachial artery and calculate the peak systolic velocity (PSV) of the arterial axis, anastomosis and efferent vein, to detect critical stenosis. The borderline stenosis, revealed by the discrepancies between access flow rate and PSV, should be followed up with subsequent tests to detect progression of stenosis; the cases with significant changes in brachial flow should be referred to angiography. In conclusion, clinical monitoring remains the backbone of any VA program. CD-US is of utmost importance in a patient-centered VA evaluation, because it allows the appropriate management of all aspects of VA care. These are the main reasons why we strongly advocate the adoption of a VA surveillance program based on CD-US.

Efficacy and Safety of a New Technique of Conversion from Temporary to Tunneled Central Venous Catheters.

The usually applied conversion technique from temporary to tunneled central venous catheters (CVCs) using the same venous insertion site requires a peel-away sheath. We propose a conversion technique without peel-away sheath: a guide wire is advanced through the existing temporary CVC; then, a subcutaneous tunnel is created from the exit to the venotomy site. After removing the temporary CVC, the tunneled one is advanced along the guide wire. The study group included all patients requiring a catheter conversion from January 2012 to June 2014; the control group included incident patients who had received de novo placement of tunneled CVCs from January 2010 to December 2011. The main outcome measures were technical success and immediate complications. Seventy-two tunneled catheters (40 with our conversion technique and 32 with the traditional one) were placed in 72 patients. The technical success was 95% in the study group and 75% in the controls (p = 0.019). The immediate complications were one bleeding in the study group (2.5%) and one air embolism, one pneumothorax, and four bleedings (18.7%) in the controls (p = 0.039). Conversion from temporary to tunneled CVC using a guide wire and without a peel-away sheath is an effective and safe procedure.

Physical activity in chronic kidney disease: a plausible approach to vascular calcification?

Vascular calcification (VC) is a prominent feature that affects up to 40 to 80% of Chronic Kidney Disease (CKD) patients depending on the degree of renal impairment. Though etiology and pathogenesis of the different types of VC are far from being elucidated, it is conceivable that an imbalance between promoters and inhibitors represents the condition that triggers VC deposition and progression. In addition to traditional cardiovascular risk factors, several lines of evidence suggest that specific factors may affect the arterial system and prognosis in CKD. Over the last decade, a few pharmacological strategies aimed at controlling different selected risk factors for VC have been investigated yielding conflicting results. In light of the complicated interplay between inhibitors and promoters as well as the fact that VC represents the result of cumulative and prolonged exposure to multiple risk factors, a more comprehensive risk modification approach such as lifestyle modification or physical activity (PA) may represent a valid strategy to attenuate VC deposition and progression.We herein aim at reviewing the rationale and current evidence on the potential for lifestyle modification with a specific focus on PA as a cost-effective strategy for VC treatment.

Nephrology Partnership for Advancing Technology in Healthcare (N-PATH) program: the teachers' perspective.

The N-PATH (Nephrology Partnership for Advancing Technology in Healthcare) program concluded with the 60th European Renal Association 2023 Congress in Milan, Italy. This collaborative initiative aimed to provide advanced training in interventional nephrology to young European nephrologists. Funded by Erasmus+ Knowledge Alliance, N-PATH addressed the global burden of chronic kidney disease (CKD) and the shortage of nephrologists. CKD affects >850 million people worldwide, yet nephrology struggles to attract medical talent, leading to unfilled positions in residency programs. To address this, N-PATH focused on enhancing nephrology education through four specialized modules: renal expert in renal pathology (ReMAP), renal expert in vascular access (ReVAC), renal expert in medical ultrasound (ReMUS) and renal expert in peritoneal dialysis (RePED). ReMAP emphasized the importance of kidney biopsy in nephrology diagnosis and treatment, providing theoretical knowledge and hands-on training. ReVAC centred on vascular access in haemodialysis, teaching trainees about different access types, placement techniques and managing complications. ReMUS recognized the significance of ultrasound in nephrology, promoting interdisciplinary collaboration and preparing nephrologists for comprehensive patient care. RePED addressed chronic peritoneal dialysis, offering comprehensive training in patient selection, prescription, monitoring, complications and surgical techniques for catheter insertion. Overall, N-PATH's strategy involved collaborative networks, hands-on training, mentorship, an interdisciplinary approach and the integration of emerging technologies. By bridging the gap between theoretical knowledge and practical skills, N-PATH aimed to revitalize interest in nephrology and prepare proficient nephrologists to tackle the challenges of kidney diseases. In conclusion, the N-PATH program aimed to address the shortage of nephrologists and improve the quality of nephrology care in Europe. By providing specialized training, fostering collaboration and promoting patient-centred care, N-PATH aimed to inspire future nephrology professionals to meet the growing healthcare demands related to kidney diseases and elevate the specialty's status within the medical community.

Vascular access for hemodialysis in Italy: What a national survey reveals.

BACKGROUND: Since in Italy there are no official data on vascular access (VA) for hemodialysis the Vascular Access Project Group (VAPG) of the Italian Society of Nephrology (SIN) designed a national survey. METHODS: A 35-question survey was designed and sent it to the Italian facilities through the SIN website. The basic questions were the prevalence, the location, and the surveillance of VA, the bedside use of ultrasound, the use of fluoroscopy for central venous catheter (CVC) placement, and of buttonhole technique, the role of nephrologist in the access creation. RESULT: The questionnaire was completed in June 2022 by 161 facilities. The survey registered 15,499 patients, approximately one-third of the Italian dialysis population. The prevalence of arteriovenous fistula (AVF), arteriovenous Graft (AVG), and CVC were 61.8%, 3.7%, and 34.5% respectively. The AVF location was 50% in distal forearm, 20% in meanproximal forearm, 30% in upper arm. For AVF creation, nephrologists were involved in 72% of facilities while for CVC placement in 62%. As regards VA monitoring, 21% of the facilities did not have a surveillance protocol; 60% did not register AVF thrombosis and 53% did not register CVC infections. Most of facilities use the fluoroscope during CVC placement, 37% when needed, and 22% never. Ultrasound-guided puncture of complex AVFs was used by 80% of facilities. Buttonhole puncture was used in 5% of patients. CONCLUSIONS: Some considerations emerge from the survey data: (1) The increasing CVC prevalence compared to DOPPS 5 study. (2) The low rate of AVG prevalence. (3) The nephrologist is the operator in many VA procedures. (4) The fluoroscopy for CVC placement and the US-guide puncture of the complex AVF are widely used in most facilities. (5) The practice of the buttonhole is not widespread. (6) When the operator is the nephrologist more distal fistulas are performed.

Placing a primary arteriovenous fistula that works--more or less known aspects, new ideas.

Despite the pre-operative availability of well-defined criteria to create a primary arteriovenous fistula (AVF) a high early failure/missing maturation is complained worldwide. Based on new results from basic research using numerical techniques, the authors try to guide attention to a widely neglected field in published data: the unremarkable, small, but essential surgical details in creating a successful AVF. The aim is to describe their significance and to give them a place in a cross-border context.

Rethinking an effective AV fistula-graft screening program. An "A B C".

The goal of a vascular access screening program is to detect and preemptively correct hemodynamically significant stenosis, however, a practice pattern allowing to implement such a program still remains to be defined. Achieving balance between the increase in access-related procedures by adopting an aggressive screening program, and the risks associated with the absence of any screening program, i.e., failure or abandonment of the arterio-venous access with need for central venous catheter placement, can be extremely challenging. All major guidelines agree about the role of arterio-venous access monitoring, but the way surveillance should be managed is still a controversial issue. Preserving long-term vascular access function should be a goal for all hemodialysis teams, yet it ideally requires a multidisciplinary effort with a monitoring program, calling for a great deal of involvement by hemodialysis health professionals. In this context, the engagement of skilled nurses and the role of patient empowerment with collaborative decision-making may be the key to a successful vascular access screening program. Screening programs should be personalized, shared with the patients, and tailored according to vascular access type and site. In the near future, new devices and the use of artificial intelligence may allow to support interpretation of complex data and lead to the development of prediction models for vascular access failure.