Arteriovenous Fistula Surgery Research Articles

#3008 Very low protein diet with ketoanalogues supplementation could start haemodialysis with AVF without additional CVCs insertion

Abstract Background and Aims Nutritional interventions and a low-protein diet (LPD) are a critical point in the management of chronic kidney disease (CKD). Several protein-restricted dietary regimens have been proposed in patients with end stage kidney disease: a typical LPD provides around 0.6–0.7 g·kg meanwhile a very low-protein diet (VLPD) provides around 0.3–0.4 g·kg and it is basically a vegetarian diet which has to be supplemented with essential amino acids (EAA) to satisfy the body nitrogen need and with nitrogen-free ketoanalogues (KA) to recirculate the endogenous urea, whose serum levels are elevated in patients with CKD. KA and EAA reduce the rate of progression of chronic kidney disease and improve the inflammatory state; they reduce the absorption of phosphates and can maintain a good state of nutrition even if associated with diets with very low protein content. On the contrary, an excessively restrictive and inadequate diet in terms of EAA or calorie intake induces a negative nitrogen balance, therefore cachexia. The recommended vascular access to start dialysis treatment is represented by the arteriovenous fistula (AVF). An early referral to the vascular surgeon for vascular access creation is pivotal for deciding on a patient-specific strategy for planning access. Guidelines advise referral at least 3–6 months before the expected start of HD, because time is needed for AVF maturation and possible repeat interventions when it is impaired. An early referral results in more autologous AVFs, which have a better long-term patency, whereas late referral, results in a greater risk of AVF non-maturation and failure and therefore the need for additional central venous catheters (CVCs) to initiate dialysis. Recent studies have shown that pre-dialysis patients who undergo a VLDP + KA require less emergency dialysis access and have better elasticity of the arterial wall, better maturation rates and duration of the AVF and sometimes a reduction in the uremic toxins responsible of endothelial dysfunction. The aim of the study was to evaluate if patients could start haemodialysis with fistula cannulation, without central venous catheter insertion. Method 10 patients, late referral end stage renal disease were enrolled in a prospective, single arm study starting very low protein diet supplemented with ketoanalogues after arteriovenous fistula creation; they were followed with periodically assessment of renal function, uremic toxin, and acid-base balance until they need to start haemodialysis. It was evaluated AVF maturation and needs to additional CVC insertion. Results Patients (3 females, 7 males) mean age was 71.2 years; before AVF creation, baseline mean value was: sCr: 6.46 mg/dl, sUrea: 150 mg/dl, phosphorus: 4.45 mg/dl, bicarbonates: 19.8 mmol/l, eGFR: 8,37 ml/min. After 3 months of VLPD supplemented with KA, eGFR and sCr was stable to 8.25 ml/min and 6.69 respectively, sUrea and phosphorus reduced to 115 mg/dl and 3.8 mg/dl, and bicarbonate increased to 22.4 mmol/l. All 10 patients achieved AVF maturation within 3 months, no one needed CVC insertion. Conclusion In this small group we see how late referral ESRD patients, undergone AVF surgery, after 3 months of VLPD supplemented with KA, had stability of renal function, with reduction of urea and phosphorus, improvement of acid-base balance and achievement of AVF maturation, without needing of CVC insertion. For these reasons VLPD + KA could be useful in delaying haemodialysis start in late referral ESRD patients who have created AVF, without emergency placement of a central venous catheter.

Heat therapy preconditioning improves the skeletal muscle contractile and mitochondrial function in a mouse model of access-related hand dysfunction

Introduction: Hemodialysis via arteriovenous fistula (AVF) is a life-line treatment for patients with end-stage kidney disease. However, hemodialysis access-related hand dysfunction (ARHD) including ischemia, muscle weakness and alterations in mitochondrial function is prevalent following AVF placement. We tested the hypothesis that two-weeks of daily heat therapy prior to AVF surgery would improve hindlimb function in a mouse model of ARHD. Methods: Adult male C57BL/6J mice (N=9-11/group) were fed a 0.2% adenine diet to induce chronic kidney disease. Following two weeks of the initial adenine diet, animals were randomly allocated to heat therapy (HT) or control (CON) groups. Animals assigned to HT were exposed to environmental heat at 40°C in a climate chamber for 30 min/day, six days/week, for two weeks while the control mice were exposed to room temperature (~22°C). The AVF was created using the left common iliac artery and vein 24-48 hours after the last treatment session. Laser Doppler perfusion to the ventral paw was assessed post-operatively (POD) and AVF patency was verified using a high-frequency duplex ultrasound system three days prior to euthanasia. Following 14 days of recovery, in situ tibialis anterior (TA) muscle contractility and gastrocnemius muscle mitochondrial function were assessed. RNA sequencing analysis of the hindlimb skeletal muscle (N=4/group) was performed. Results: Compared to baseline, the level of blood urea nitrogen was similarly elevated ( P<0.05) in both groups following four weeks of adenine diet. In both groups, blood perfusion to the paw was decreased by ~50% immediately after AVF creation and progressively recovered to ~80% at POD13 without a treatment effect ( P=0.4467). No differences in body weight and muscle mass in the TA, extensor digitorum longus, and soleus muscles were observed (all P>0.05). Notably, however, the absolute ( P=0.0250) and specific force ( P=0.0101) frequency relationship of the TA muscle were significantly improved in the animals exposed to HT. In addition, compared with control animals, HT mice had significant improvement in oxidative phosphorylation (OXPHOS) in both pyruvate ( P=0.0145) and octanoylcarnitine ( P=0.0196) fueled conditions. RNA sequencing results revealed that genes involved in nervous system development and metabolism were significantly different between HT and CON groups. Conclusion: Daily application of heat therapy for two weeks prior to the AVF surgery has beneficial effects on both skeletal muscle contractile and mitochondrial function suggesting this pre-habilitation strategy may mitigate the risk of ARHD in patients undergoing AVF surgery. Funding Support: National Institutes of Health grant R01HL148597 and American Heart Association grant POST903198. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Digital exoscope versus surgical microscope in spinal dural arteriovenous fistula surgery: a comparative series.

Surgical treatment of spinal dural arteriovenous fistulas (DAVFs) has been reported to be superior to endovascular treatment in terms of occlusion of the fistula. Despite the increased availability of digital 3D exoscopes, the potential benefits of using an exoscope in spinal DAVF surgery have not been studied. The purpose of this study was to report and compare the results of exoscope- and microscope-assisted surgery for spinal DAVFs. All consecutive adult patients (≥ 18 years of age) treated surgically for spinal DAVFs from January 2016 to January 2023 in a tertiary neurosurgical referral center were included. All patients were operated on by one neurosurgeon. Their pre- and postoperative clinical findings, imaging studies, and intra- and postoperative events were evaluated and surgical videos from the operations were analyzed. Altogether, 14 patients received an operation for spinal DAVF during the study period, 10 (71%) with an exoscope and 4 (29%) with a microscope. The DAVFs were most commonly located in the lower parts of the thoracic spine in both groups. The duration of exoscopic surgeries was shorter (141 vs 151 minutes) and there was less blood loss (60 vs 100 ml) than with microscopic surgeries. No major surgical complications were observed in either group. Of the 14 patients, 10 had gait improvement postoperatively: 7 (78%) patients in the exoscope group and 3 (75%) in the microscope group. None of the patients experienced deterioration following surgery. Exoscope-assisted surgery for spinal DAVFs is comparable in safety and effectiveness to traditional microscopic surgery. With practice, experienced neurosurgeons can adapt to using the exoscope without major additional risks to the patient.

Comparative analysis of RADAR vs. conventional techniques for AVF maturation in patients with blood viscosity and vessel elasticity-related diseases through fluid-structure interaction modeling: Anemia, hypertension, and diabetes.

This study aims to compare two surgical techniques, the standard Vein-to-Artery and the newer Artery-to-Vein (Radial Artery Deviation And Reimplantation; RADAR), for enhancing the success of Arterio-Venous Fistula maturation in end-stage renal disease patients. The impact of diseases like anemia, diabetes, hypertension, and chronic kidney disease were considered. The goals are to advance Arterio-Venous Fistula (AVF) surgery, improve patient outcomes, and contribute to evidence-based surgical guidelines. Fluid-structure interaction modeling was employed to investigate how hemodynamic and mechanical stresses impact arteriovenous fistula maturation, with a particular focus on the role of wall shear stress in determining maturation outcomes. The critical threshold for vessel injury was identified as wall shear stress values exceeding 35 N/m2, while stenosis formation was projected to occur at levels below 1 N/m2. This work introduced a novel approach by considering disease-related factors, including blood viscosity (anemia), and vessel elasticity (diabetes, hypertension, and chronic kidney diseases), which directly influence hemodynamics and the generation of wall shear stress. Furthermore, the model was designed to incorporate varying thicknesses and elasticities for both the vein and artery, accurately representing authentic vascular anatomy. The RADAR technique has demonstrated superior performance compared to the standard technique by providing appropriate wall shear stress in critical regions and minimizing the risk of wall damage. Its use of a thicker vessel also reduces the risk of vessel injury, making it particularly effective for patients with Chronic Kidney Disease (CKD), hypertension, anemia, and diabetes, ensuring optimal blood flow and fewer complications. However, there are minor concerns about stenosis formation in hypertension and anemia cases, which could be mitigated by adjusting the anastomosis angle to be lower than 30°. Diabetes and hypertension have significant physiological effects that increase the risks associated with arteriovenous fistula maturation. The anemic condition resulting from CKD may help reduce vessel injury but raises concerns about potential stenosis formation. Despite these co-morbidities, the RADAR technique has demonstrated its ability to induce more favorable hemodynamic changes, promoting arteriovenous fistula maturation.

Predicting factors for early failure of vascular access in hemodialysis patients.

This study aimed to investigate the incidence of early failure of vascular access for hemodialysis, and determine which factors measured in duplex ultrasound study could predict early failure. We performed a retrospective review of patients who underwent arteriovenous fistula (AVF) or arteriovenous graft (AVG) creation for hemodialysis between September 2019 and January 2023. Early failure was defined as any event that required surgical or endovascular intervention within 6 months following AVF or AVG creation. A total of 189 patients were included. Early failure occurred in 36 patients (19.0%), which included 22 AVFs and 14 AVGs. In the patients who underwent AVF, the preoperative venous diameter, postoperative venous and arterial diameters, and flow volume of AVF all were significantly smaller in the early failure group compared to the patent group. In AVG, the preoperative venous diameter was the only parameter that differed between the 2 groups. A sonographic score was defined based on these factors. In a multivariable analysis, male sex, a previous history of AVF or AVG creation, and sonographic score were found to be significantly associated with early failure. The postoperative venous diameter in AVF and the preoperative venous diameter in AVG were highly predictive of early failure (areas under the curves 0.92 and 0.82, respectively). Venous diameter measured 6 weeks following AVF operation and preoperative venous diameter in AVG were highly predictive of early failure among the duplex ultrasound parameters. Surveillance strategies in the early phase following vascular access creation can be based on these factors.

A rare case report: compartment syndrome after brachiocephalic arteriovenous fistula formation in a hemodialysis patient

Introduction: Acute compartment syndrome is a condition in which increased pressure in the tight fascia space reduces capillary perfusion below the level required for tissue viability. Very few cases of acute compartment syndrome associated with dialysis have been reported. It can lead to severe damage to the tissues of the arm. Case Illustration: A 47-year-old woman with end-stage renal failure presented to the emergency room with swelling and pain in the right upper extremity and has lasted for a day. Three days before admission, the patient underwent right brachiocephalic arteriovenous (AV) fistula surgery. Physical Examination showed a blackish bruise at the fossa cubiti, radial and ulnar artery were not palpable, but there is trill at AV fistula. Decreased motoric strength, reduced hand sensation and decreased capillary return in fingers. Oxygen blood saturation of the right fingers could not be read. Diagnosis of acute compartment syndrome was made. The patient was immediately taken to the operating room for decompression surgery. Emergency compartment fasciotomy was performed. After fasciotomy, necrotomy was performed. Furthermore, brachiocephalic AV fistula was ligated. Postoperative evaluation obtained good radial and ulnar artery. Six months after the surgery, the wound was fully healed and no sign of neuromuscular or vascular deficit. Conclusion: Compartment syndrome is a possible complication after AV fistula formation that can have disastrous consequences. However, it can be effectively treated if detected and treated early. Prognosis of compartment syndrome after fasciotomy depends on how quickly the condition is diagnosed and treated.

Early arteriovenous fistula failure associated with mortality and major adverse cardiovascular events in patients undergoing incident hemodialysis.

Arteriovenous fistula (AVF) patency is important for patients undergoing hemodialysis. The association between early AVF failure and the prognosis, including all-cause mortality and major adverse cardiovascular events (MACE), has not been fully investigated. The present study was performed to investigate the association between early AVF failure and 3-year mortality, cardiovascular disease (CVD) mortality, and MACE. We analyzed 358 patients who started hemodialysis in our institution from October 2008 to February 2020. We defined early AVF failure as cases requiring percutaneous transluminal angioplasty or reoperation within 1 year after AVF surgery. The patients were divided into two groups according to the presence or absence of early AVF failure, and the prognosis of each group was examined. The association between early AVF failure and outcomes (3-year all-cause mortality, CVD mortality, and MACE) was determined using Cox proportional hazards regression analysis. During the 3-year follow-up, 75 (20.9%) patients died (cardiovascular death: n = 39) and 145 patients developed MACE. According to the multivariable analysis, the early AVF failure group had a significantly higher risk of 3-year all-cause mortality (hazard ratio [HR], 1.42; 95% confidence interval [CI], 1.09-1.83; p = 0.009), CVD mortality (HR, 1.54; 95% CI, 1.29-2.08; p < 0.001), and MACE (HR, 1.68; 95% CI, 1.25-2.26; p < 0.001). When the patients were stratified by age, early AVF failure was associated with 3-year all-cause mortality in all groups except for the younger group (<65 years of age). Early AVF failure was associated with an increased risk of 3-year all-cause mortality, CVD mortality, and MACE.

Factors Associated with Dialysis Initiation in Patients with Predialysis Arteriovenous Fistula

Introduction: A large proportion of patients initiated hemodialysis with a central vein catheter rather than a permanent vascular access which was recommended by guidelines. One major barrier was the paucity of evidence regarding the optimal timing of vascular access creation in predialysis patients. Methods: Our study prospectively enrolled 300 patients undergoing predialysis arteriovenous fistula (AVF) creation in our center from 2015 to 2018. Cox proportional hazard regression was performed to identify which demographic and clinical factors were associated with the initiation of hemodialysis after AVF surgery. A receiver operating characteristic area under the curve (AUC) was used to assess the predictive power of preoperative factors for the likelihood of hemodialysis initiation. Results: Overall, 163 (54.3%), 214 (71.3%), and 275 (91.7%) patients initiated hemodialysis within 3 months, 6 months, and 1 year, respectively, after AVF creation. The median time between AVF creation and hemodialysis start was 71.5 days. Using multivariate Cox regression analysis, three factors were associated with hemodialysis initiation within 1 year: serum phosphorus (HR = 1.407, p = 0.021), diabetic kidney disease (DKD) (HR = 1.429, p = 0.039), and cystatin C (HR = 1.179, p = 0.009). Cystatin C alone had a moderate predictive value for dialysis initiation (AUC = 0.746; p < 0.001), whereas the full model had a higher predictive value (AUC = 0.800; p < 0.001). Conclusion: DKD, serum cystatin C, and phosphorus at access surgery were associated with hemodialysis initiation within 1 year of the predialysis AVF creation. Our findings provide a basis for a more customized approach to planning AVF placement in patients with chronic kidney disease.

Slowly moving the needle away from Fistula First

ObjectiveIn 2019, the management of end-stage kidney disease (ESKD) shifted away from “Fistula First” (FF) to “ESKD Life-Plan: Patient Life-Plan First then Access Needs.” Indeed, some patients exhibit such excessive comorbidity that even relatively minor vascular surgery may be complicated. The purpose of this study was to retrospectively assess complications and mortality (and delineate operative futility) in patients undergoing arteriovenous fistula (AVF) creation in the FF era. MethodsConsecutive AVFs created in a single institution before 2021 were retrospectively reviewed. Operative futility was defined as never-accessed fistula, no initiation of dialysis, failure of access maturation (despite secondary intervention), hemodialysis access-induced distal ischemia requiring ligation, early loss of secondary patency, and/or patient mortality within the first 6 postoperative months. ResultsA total of 401 AVFs were created including radial-cephalic (44%), brachial-cephalic (41%), and brachial-basilic (15%) constructions. Patients exhibited a mean age of 69 ± 15 years; 63% were male, and most (74%) were already being hemodialyzed at the time of fistula creation. Forty-five patients (11%) suffered a cardiac event, and five patients died (1%) within 90 days of their access surgery. Perioperative cardiac events were significantly more common after age 80 (19% vs 8%; P = .004); age >80 years was an independent predictor of major 90-day complications (odds ratio [OR], 1.88; 95% confidence interval [CI], 1.04-3.39; P = .036) and the sole independent predictor of major morbidity defined as cardiopulmonary complications, stroke, or death within the first year (OR, 2.01; 95% CI, 1.24-3.25; P = .004). Operative futility was encountered in 52% of the cohort (n = 208 patients): 40% (n = 160) of primary AVFs failed to mature despite assistance, 19% (n = 77) had lost secondary patency by 6 months, 13% of patients (n = 53) were never started on dialysis after access creation, 4% (n = 16) were dead by 6 months, 2% of AVFs (n = 10) matured but were never accessed, and 2% (n = 9) required ligation for hemodialysis access-induced distal ischemia. Not surprisingly, the sole independent protector against operative futility was that catheter-based dialysis had been established prior to AVF creation (OR, 0.36; 95% CI, 0.22-0.59; P < .01). ConclusionsApproximately 50% of primary AVF operations performed in the aggressive FF era were deemed futile. Octogenarians were particularly prone to futility and complications during this era. A paradigm shift, from FF to an “ESKD Life-Plan” will, hopefully, more thoughtfully match vascular access strategies to individual patient needs.

Arteriovenöz Fistül Cerrahisinde Rejyonal ve Lokal Anestezi Karşılaştırması: Tek Merkezli Bir Araştırma

Background: This retrospective study aimed to compare the outcomes of regional anesthesia and local anesthesia techniques in arteriovenous fistula operations, focusing on early patency rates, operation time, and postoperative pain. Methods: A total of 77 arteriovenous fistula and arteriovenous graft operations performed between April 2020 and April 2023 on adult patients with chronic renal failure were analyzed. The patients were divided into two groups based on the anesthesia technique: Group-1 (n=49) received local anesthesia, while Group-2 (n=28) received regional anesthesia. Results: The majority of operations in the local anesthesia group involved radio-cephalic arteriovenous fistula, while brachio-cephalic, brachio-basilic arteriovenous fistula, and arteriovenous grafts were predominantly performed in the regional anesthesia group. There was no significant difference in operation time between the two groups. However, the regional anesthesia group had a significantly lower need for pain relief within the first 24 hours postoperatively. There were no significant differences in early postoperative fistula failure or bleeding/hematoma between the groups. One case of local wound infection was observed in each group during post-discharge follow-up. Conclusion: This retrospective analysis suggests that regional anesthesia provides superior pain control in the first 24 hours following arteriovenous fistula surgery compared to local anesthesia. Regional anesthesia is a safe and effective technique and may be preferred for more sophisticated arteriovenous fistula procedures.

Developing the surgeon-machine interface: using a novel instance-segmentation framework for intraoperative landmark labelling.

The utilisation of artificial intelligence (AI) augments intraoperative safety, surgical training, and patient outcomes. We introduce the term Surgeon-Machine Interface (SMI) to describe this innovative intersection between surgeons and machine inference. A custom deep computer vision (CV) architecture within a sparse labelling paradigm was developed, specifically tailored to conceptualise the SMI. This platform demonstrates the ability to perform instance segmentation on anatomical landmarks and tools from a single open spinal dural arteriovenous fistula (dAVF) surgery video dataset. Our custom deep convolutional neural network was based on SOLOv2 architecture for precise, instance-level segmentation of surgical video data. Test video consisted of 8520 frames, with sparse labelling of only 133 frames annotated for training. Accuracy and inference time, assessed using F1-score and mean Average Precision (mAP), were compared against current state-of-the-art architectures on a separate test set of 85 additionally annotated frames. Our SMI demonstrated superior accuracy and computing speed compared to these frameworks. The F1-score and mAP achieved by our platform were 17% and 15.2% respectively, surpassing MaskRCNN (15.2%, 13.9%), YOLOv3 (5.4%, 11.9%), and SOLOv2 (3.1%, 10.4%). Considering detections that exceeded the Intersection over Union threshold of 50%, our platform achieved an impressive F1-score of 44.2% and mAP of 46.3%, outperforming MaskRCNN (41.3%, 43.5%), YOLOv3 (15%, 34.1%), and SOLOv2 (9%, 32.3%). Our platform demonstrated the fastest inference time (88ms), compared to MaskRCNN (90ms), SOLOV2 (100ms), and YOLOv3 (106ms). Finally, the minimal amount of training set demonstrated a good generalisation performance -our architecture successfully identified objects in a frame that were not included in the training or validation frames, indicating its ability to handle out-of-domain scenarios. We present our development of an innovative intraoperative SMI to demonstrate the future promise of advanced CV in the surgical domain. Through successful implementation in a microscopic dAVF surgery, our framework demonstrates superior performance over current state-of-the-art segmentation architectures in intraoperative landmark guidance with high sample efficiency, representing the most advanced AI-enabled surgical inference platform to date. Our future goals include transfer learning paradigms for scaling to additional surgery types, addressing clinical and technical limitations for performing real-time decoding, and ultimate enablement of a real-time neurosurgical guidance platform.

Temporal serum metabolomic and lipidomic analyses distinguish patients with access-related hand disability following arteriovenous fistula creation

For end-stage kidney disease (ESKD) patients, hemodialysis requires durable vascular access which is often surgically created using an arteriovenous fistula (AVF). However, some ESKD patients that undergo AVF placement develop access-related hand dysfunction (ARHD) through unknown mechanisms. In this study, we sought to determine if changes in the serum metabolome could distinguish ESKD patients that develop ARHD from those that have normal hand function following AVF creation. Forty-five ESKD patients that underwent first-time AVF creation were included in this study. Blood samples were obtained pre-operatively and 6-weeks post-operatively and metabolites were extracted and analyzed using nuclear magnetic resonance spectroscopy. Patients underwent thorough examination of hand function at both timepoints using the following assessments: grip strength manometry, dexterity, sensation, motor and sensory nerve conduction testing, hemodynamics, and the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire. Nineteen of the forty-five patients displayed overt weakness using grip strength manometry (P < 0.0001). Unfortunately, the serum metabolome was indistinguishable between patients with and without weakness following AVF surgery. However, a significant correlation was found between the change in tryptophan levels and the change in grip strength suggesting a possible role of tryptophan-derived uremic metabolites in post-AVF hand-associated weakness. Compared to grip strength, changes in dexterity and sensation were smaller than those observed in grip strength, however, post-operative decreases in phenylalanine, glycine, and alanine were unique to patients that developed signs of motor or sensory disability following AVF creation.

Standardization of Pre-operative Evaluation to Improve the Outcome of Arteriovenous Fistula for Vascular Access of Hemodialysis: A Review of 700 Cases.

Background With the advent of COVID-19, mortality rates of end-stage kidney disease (ESKD) rose by 37% which makes its treatment an important part of healthcare. Arteriovenous fistula (AVF) is linked to higher patient survival rates. Cimino-Brescia fistula is the most effective vascular access technique, but it has a high rate of primary failure (PF) and a several-week maturation period before it can be used. The current study aims to verify the preoperative evaluation in improving survival among AVF patients. Methodology The current study is a retrospective analysis of the hospital database from Jan 2022 to July 2023, with patients of a mean age of 60.2 years. The sample size was around 700, including the patients indicated for long-term hemodialysis (HD) with an estimated GFR of less than 20 mm/min/1.73m². Following AVF surgery, post-operative outcomes, PF, and maturation time were considered. Results Among the 757 AVF procedures, 588 (82%) were new cases, and 112 (16%) had prior AVF history on the same side. PF was observed in 126 (18%) AVFs, while 574 (84%) achieved maturation. Age at surgery did not correlate with PF. Male sex and brachiocephalic AVF (BCAVF) had lower PF rates, while female gender, non-BCAVF, and vascular chronic kidney disease (CKD) were independent predictors. Proximal fistulas had a higher failure risk (32%). During surgery, the PF occurred six times more frequently in patients with veins and arteries under 2 mm and without a bruit. Conclusion AVF maturation aims to achieve a functional AVF for easy dialysis, requiring meticulous vein selection, doppler vascular mapping, and a standardized process to reduce PF rates. Factors determining PF include thrill and bruit, flow rates, and comorbidities. These findings can help clinicians make informed decisions and improve outcomes for patients undergoing fistula surgery.

The Benefit of Cost-Transparency Calculators Does Not Extend to Vascular Surgery Patients

In 2021, the Centers for Medicare & Medicaid Services (CMS) mandated that every hospital create a publicly available webtool for pricing various medical services in an effort to give patients transparency in regard to their health care expenses and allow patients to "shop around" to receive the care most fitting their budget. Our objective is to investigate the utility this mandate provides for vascular surgery patients. Standardized searches were performed to find patient cost calculators for Newsweek's Top 50 Hospitals in the United States. If the webtool was found, a list of standardized searches were performed to investigate whether the tool listed prices for the following vascular procedures: Arteriovenous fistula (AVF), varicose vein procedures, and Endovascular Aneurysm Repair (EVAR). Of the 50 hospitals included, all had an easily accessible web-based cost estimator tool. The average time to find the cost estimator was 33.27sec. Of these 50 hospitals, 10% provided cost information on AVF surgery, 12% provided cost information on varicose vein procedures, and 0% provided information on EVAR. There was no difference in the hospital's likelihood to report a price based on region of the United States. Average preinsurance price for AVF surgery was $11,933.61 and $22,191 for vein procedures. In conclusion, despite good adherence to the CMS mandate requiring a publicly available pricing tool, these tools provide little to no information for vascular surgery patients. Overall, this discrepancy places vascular surgery patients at a significant disadvantage. As such, vascular patients do not have access to the knowledge necessary to financially prepare for surgery, and furthermore, they are not afforded the luxury to choose where to have procedures performed based on price variability. Hopefully this research will encourage hospitals to broaden the scope of their cost calculators to allow it to benefit all patients.

N-acetylcysteine treatment attenuates hemodialysis access-related limb pathophysiology in mice with chronic kidney disease.

The objective of the present study was to determine if treatment with N-acetylcysteine (NAC) could reduce access-related limb dysfunction in mice. Male and female C57BL6J mice were fed an adenine-supplemented diet to induce chronic kidney disease (CKD) prior to the surgical creation of an arteriovenous fistula (AVF) in the iliac vascular bundle. AVF creation significantly increased peak aortic and infrarenal vena cava blood flow velocities, but NAC treatment had no significant impact, indicating that fistula maturation was not impacted by NAC treatment. Hindlimb muscle and paw perfusion recovery and muscle capillary density in the AVF limb were unaffected by NAC treatment. However, NAC treatment significantly increased the mass of the tibialis anterior (P = 0.0120) and soleus (P = 0.0452) muscles post-AVF. There was a significant main effect of NAC treatment on hindlimb grip strength at postoperative day 12 (POD 12) (P = 0.0003), driven by significantly higher grip strength in both male (P = 0.0273) and female (P = 0.0031) mice treated with NAC. There was also a significant main effect of NAC treatment on the walking speed at postoperative day 12 (P = 0.0447), and post hoc testing revealed an improvement in NAC-treated male mice (P = 0.0091). The area of postsynaptic acetylcholine receptors (P = 0.0263) and motor endplates (P = 0.0240) was also increased by NAC treatment. Interestingly, hindlimb skeletal muscle mitochondrial oxidative phosphorylation trended higher in NAC-treated female mice but was not statistically significant (P = 0.0973). Muscle glutathione levels and redox status were not significantly impacted by NAC treatment in either sex. In summary, NAC treatment attenuated some aspects of neuromotor pathology in mice with chronic kidney disease following AVF creation.NEW & NOTEWORTHY Hemodialysis via autogenous arteriovenous fistula (AVF) is the preferred first-line modality for renal replacement therapy in patients with end-stage kidney disease. However, patients undergoing AVF surgery frequently experience a spectrum of hand disability symptoms postsurgery including weakness and neuromotor dysfunction. Unfortunately, no treatment is currently available to prevent or mitigate these symptoms. Here, we provide evidence that daily N-acetylcysteine supplementation can attenuate some aspects of limb neuromotor function in a preclinical mouse model of AVF.

Building a Scaffold for Arteriovenous Fistula Maturation: Unravelling the Role of the Extracellular Matrix

Vascular access is the lifeline for patients receiving haemodialysis as kidney replacement therapy. As a surgically created arteriovenous fistula (AVF) provides a high-flow conduit suitable for cannulation, it remains the vascular access of choice. In order to use an AVF successfully, the luminal diameter and the vessel wall of the venous outflow tract have to increase. This process is referred to as AVF maturation. AVF non-maturation is an important limitation of AVFs that contributes to their poor primary patency rates. To date, there is no clear overview of the overall role of the extracellular matrix (ECM) in AVF maturation. The ECM is essential for vascular functioning, as it provides structural and mechanical strength and communicates with vascular cells to regulate their differentiation and proliferation. Thus, the ECM is involved in multiple processes that regulate AVF maturation, and it is essential to study its anatomy and vascular response to AVF surgery to define therapeutic targets to improve AVF maturation. In this review, we discuss the composition of both the arterial and venous ECM and its incorporation in the three vessel layers: the tunica intima, media, and adventitia. Furthermore, we examine the effect of chronic kidney failure on the vasculature, the timing of ECM remodelling post-AVF surgery, and current ECM interventions to improve AVF maturation. Lastly, the suitability of ECM interventions as a therapeutic target for AVF maturation will be discussed.

#5088 ARTIFICIAL INTELLIGENCE APPLIED TO VASCULAR DOPPLER ULTRASOUND MODELS FOR PREDICTING UNDERDEVELOPMENT OF VASCULAR ACCESS IN NEPHROLOGY

Abstract Background and Aims The vascular access of choice for hemodialysis patients is the arteriovenous fistula (AVF). There is a high rate of early primary failure and loss of primary AVF patency. Monitoring of vascular access is essential for early diagnosis of complications and prolonging survival. Models based on Artificial Intelligence (AI) and Machine Learning (ML) can be used for this. Method Retrospective descriptive study of the Vascular Doppler Ultrasound (VDU) in adults carried out since January 2019 to January 2022 in our AVF follow-up nephrology clinic. We analyze the results and create AI-based AVF underdevelopment prediction models. We included clinical, demographic and ultrasound variables. Patients were undergoing AVF post-surgery follow-up (VDU by protocol at 3-4 weeks after AVF surgery) or were referred to the clinic with signs of AVF dysfunction. The insufficient development of the vascular access is established as an objective variable. SPSS 20 Statistical Package. Automated Learning Analysis (ML) with Orange ML and BigML. Results 243 VDU were performed. Of the total, 139 (57%) were follow-up post-surgical VDU per protocol and 104 (43%) were AVF dysfunction VDU. Using supervised ML Analysis techniques with random sampling of 80% of the instances for Training and 20% for Test, we obtain prediction models for the underdevelopment (UD) attribute of FAV: Decision tree algorithm, Area under the curve (AUC) 89%, Classification accuracy (CA) 90%, Precision 90%. Random Forest Algorithm (RF) (AUC) 95%, (CA) 86%, Accuracy 81%. Near Neighbor Algorithm (K-NN) (AUC) 88%, CA 82%, Accuracy 78%. Convolutional Neural Networks (NNC) (AUC) 82%, CA 74%, Accuracy 60%. Algorithm with unsupervised technique of clustering in k-Means 3 clusters are obtained. The variables that best correlate with the objective variable are access flow, vein diameter, resistance index (RI) proximal, (RI) distal, and diameter of the anastomosis. Conclusion The vascular ultrasound systematized by the nephrologist facilitates the early diagnosis of complications that lead to early intervention. Analysis of the data with techniques (ML) can facilitate early diagnosis AVF poor development requiring close monitoring or intervention. The development of a nephrology clinic for monitoring vascular access could avoid invasive and unnecessary procedures for the patient.

#5866 CLINICAL CHARACTERISTICS AND TREATMENT OF ADULT DIALYSIS PATIENTS FROM UKRAINE DISPLACED TO OTHER EUROPEAN COUNTRIES AFTER THE RUSSIAN INVASION

Abstract Background and Aims The Russian invasion on Ukraine, which started on 24th February 2022 led to migration of millions of people, including some of the about 10,000 adult dialysis patients. A Renal Disaster Relief Task Force (RDRTF) established by the European Renal Association, is dedicated to support the people living with kidney disease and to the nephrology community in Ukraine, working together with WHO, NGOs and industry. Besides these activities, the RDRTF conducted a survey to understand distribution and management of Ukrainian refugees requiring dialysis displaced to other European countries. The study aim was to characterize these patients and evaluate treatment modality and care they received after displacement. Method A cross-sectional online survey on status of displaced dialysis patients, clinical data and care they received after migration was sent to all national nephrology societies across Europe with a request to disseminate it to all dialysis centers in their countries. Data were collected between May and August 2022. Fresenius Medical Care (FMC) shared a set of aggregated data without direct center participation. Results Data on 602 patients (290 collected through the survey and 312 from FMC), who were dialyzed in 24 countries was gathered. Most patients were dialyzed in Poland (45.0%), followed by Slovakia (18.1%), Czech Republic (7.8%), Romania (6.3%), Germany (4.7%) and Hungary (3.5%). Mean time between last dialysis session and the first session in the reporting center was 3.1±1.6 days. For 28.1% of patients this time interval ranged from 4 to 12 days. Mean age was 48.1±13.4 years, and 43.5% of patients were females. The most common primary cause of kidney failure in the study group was glomerulonephritis or autoimmune diseases (29.5%), diabetic nephropathy constituted 12.7%. Before patients left Ukraine, 95.7% had been on hemodialysis, 2.5% on continuous ambulatory peritoneal dialysis (PD) and 1.8% on automated PD. Since leaving Ukraine, 33.8% of patients were hospitalized upon arrival at the reporting center. The most common causes of hospitalization were: anemia (18.6%), COVID-19 pneumonia (4.7%), non-COVID pneumonia (4.7%), overhydration (4.7%) and Perm-Cath implantation (4.7%), followed by exacerbation of heart failure, peripheral artery occlusive disease and arteriovenous fistula surgery. In terms of pharmacotherapy provided in the reporting dialysis units, 50.3% of patients received erythropoiesis stimulating agents and 36.9% received intravenous iron supplementation. 35.0%, 21.9% and 3.3% received phosphate binders, vitamin D analogues and cinacalcet, respectively. 29 patients (11.4%) were waitlisted for kidney transplantation (KTx) in Ukraine before displacement. Of these, 15 also qualified for KTx in the receiving country. A further 33 individuals who had not been listed for KTx in Ukraine, started the KTx recipient work-up under the care of the reporting center. Overall, 43 patients (17.4%) received psychological support – for 29 provided by the reporting dialysis units and for 14 patients outside the center. Conclusion Under 10% of dialysis patients fled Ukraine since the start of the Russian-Ukrainian war. Almost 30% of them remained without dialysis for 4 days or longer. Clinical status upon arrival often necessitated hospitalization. Our data indicate, that the treatment at receiving centers conformed with standard of care. Monitoring the situation of dialysis patients during armed conflicts may help in creating informed policies that allow for prompt and targeted interventions to respond to special needs of this vulnerable population.

#3349 METICULOUS CATHETER CARE CAN REDUCE CATHETER-RELATED BLOODSTREAM INFECTIONS SIGNIFICANTLY IN HAEMODIALYSIS PATIENTS – A 5-YEAR SINGLE CENTRE STUDY

Abstract Background and Aims The use of central venous catheters as hemodialysis (HD) vascular access is a leading contributor to a high rate of bloodstream infection. Our dialysis unit in China has followed the China National Infection Control Policy for HD unit as well as developed its own specific dialysis catheter care protocol using the Centre for Disease Control and Prevention (CDC) guidelines as a template. By doing so, our HD unit has achieved a tunneled dialysis catheter (TDC)- related bloodstream infection rate of 0.0229 per 1000 catheter days in the past 5 years. This report, aims to share our experience with the other units. Method We have undertaken a retrospective analysis to determine our catheter-related bloodstream infection (CRBSI) rate. The local Ethics and Research Committee has approved the conduct of the retrospective study. In this study, the definition of a CRBSI is taken from Kidney Disease Outcomes Quality Initiative (KDOQI) Vascular Access-2019 update as 1) clinical manifestations (fever &amp;gt; 37.5°C or rigors or presence of clinical signs of infection); 2) confirmation of bacteremia (blood cultures growing the same organism from the dialysis catheter and a peripheral vein), with either positive semiquantitative (&amp;gt;15CFU/catheter segment), or quantitative (&amp;gt;102 CFU/catheter segment), differential period of catheter culture versus peripheral blood culture (BC) positivity of 2 hours; 3) exclusion of another source of infection. Information including patient demographics, causes of kidney failure, and duration of TDC was obtained. Results The Covidien Palindrome chronic catheters have been used in the majority of our patients during the study period. All tunneled dialysis catheters were placed by the nephrologists under radiological guidance in the Hospital's sterile Digital Subtraction Angiography (DSA) Suite. In the study period (2017-2021), an average of 235 prevalent patients were receiving dialysis in the HD unit. A total of 212 tunneled dialysis catheters have been inserted and managed according to our local dialysis access pathway and catheter care protocol. The TDC days have been calculated by adding all the catheter days until the catheters have been removed or the patients have been transferred out of our HD unit. There was a total of 43,585 catheter days. The average waiting time for arteriovenous fistula (AVF) surgery was two weeks. The mean duration of TDC use was 107.8±14.8 days, range 1-1827 days. The incidence of confirmed tunneled CRBSI was 0.0229/ 1000 catheter days. Conclusion Our local catheter care protocol is similar to the CDC's “scrub-the-hub” protocol. 2% chlorhexidine with 70% alcohol has been used for the scrubbing and disinfection but we have a few additional steps. In our practice, great attention is given to the cleansing of the clamps. 1) Prior to removal of the caps, the clamps are opened and the surroundings are cleaned and disinfected thoroughly. 2) Two nurses are assigned to connect the bloodlines to the hubs, hence the risk of hub contamination is reduced. 3) The point of connection between the hubs and the bloodlines is protected with a gauze dressing in 3 layers during the entire duration of the dialysis. We believe our success with a very low rate of CRBSI has been the result of strict adherence to 1) good and general hygiene, 2) a well-designed dialysis catheter care protocol, 3) good use of a vascular access nurse, 4) short-duration of TDC days, and 5) short waiting time for AVF. Limitations: We may have underestimated the true rate of CRBSI because of the inherent nature of the diagnostic criteria as mentioned above. Although it is unlikely that a blood culture would have been missed before intravenous antibiotics under our hospital's stringent antibiotics stewardship and continuous audit, it is still possible in theory. Finally, a small number of patients has been transferred out to other HD units due to their change of residence, hence the follow up data might be incomplete. However, such patients are very few in number and the long follow up of this study strengthens our findings and conclusion.

#4731 THE CHANGING HAEMODIALYSIS POPULATION IN A SINGLE UK CENTRE: A POST PANDEMIC PHENOMENON?

Abstract Background and Aims Following the Covid-19 pandemic, UK dialysis centres have seen a sharp increase in numbers of patients requiring renal replacement therapy (RRT) particularly haemodialysis (HD). This has resulted in pressures on dialysis capacity and staffing. There may also have been negative effects on other aspects of quality of care, such as a fall in the proportion of patients dialysing via an Arterio-venous fistula (AVF) or worsening anaemia. To study this further, we conducted a retrospective observational study to describe the incident and prevalent HD populations in the post-Covid pandemic period and compare these against pre-pandemic patterns, in a single UK dialysis centre. Method We reviewed data on prevalent HD patient numbers across our service. We specifically collected data from all patients commencing HD between January 2021 and December 2022 using electronic medical records. We collected information on time known to renal prior to starting dialysis, clinic data including which types of clinic attended, documentation of pre-dialysis decisions about modality as well as vascular access referrals, vascular access clinics and vascular access surgery as well as haemoglobin (Hb) at first dialysis. We compared figures with published pre-pandemic data from the 23rd annual UK Renal Registry report on data collected to December 2019 for our centre. We defined a planned start to dialysis as patients who were known to renal &amp;gt;90 days. This aligns with the registry definition. We compared proportional data using the chi square test. Results Comparing prevalent data in Dec. 2022 with Dec 2019, there was a 17% increase in the prevalent HD population from 298 to 349. The proportion of patients dialysing via an AVF fell from 88% to 80% (p = 0.006). The spread across different types of HD in Dec.2022 remained static at 71% In-Centre HD (72% in Dec 2019), 11% Satellite HD (9% in 2019) and 17% HHD (18% 2019) with overall numbers rising across all HD modalities (p for trend = 0.37). PD numbers also rose from 58 to 71 keeping the total percentage on home therapies stable at 31% in our unit. From Jan. 2021- Dec. 2022 inclusive 147 people commenced HD of whom 115 (78%) had planned starts. This compares to 58 starting HD in 2019 and 79% planned (p = 0.85). There was a significant fall in the proportion of planned start HD patients who commenced dialysis with an AVF/AVG, from 81% in 2019 to 56% in 2021-22 (p = 0.003). Themes emerged n planned starters who did not start HD with an AVF/AVG and are detailed in Figure 1. Median Hb level of planned starts on HD was lower at only 94 for 2021-22 and 99 in 2019. Looking in detail at those missing appointments in clinics, 33% had prior documented evidence of fear of Covid-19. Delays in AVF surgery consisted of delayed and cancelled theatre dates, failed AVF requiring re-do or AVF awaiting further intervention at time of dialysis initiation. In the group with a last minute change in decision sighted reasons included: worsening eyesight, development of dementia in partner, reducing mobility. Others changed their mind after further input from the PD team. Despite attending the Advanced Kidney Clinic (AKC) there were still a number of patients with no decision at all. Cancellation of group sessions for dialysis education persisted in our centre until mid-2022 and may have contributed to reduced timely decision making as well as late modality switches. All those with an early failure of PD (defined as &amp;lt; 90 days) had chosen PD prior to the Covid-19 pandemic with intervening remote visits in AKC. Conclusion Following the Covid-19 pandemic, unexpected and unprecedented changes in the HD incident population have been observed, resulting in pressures on dialysis services. In particular, we report an increase in absolute number of dialysis patients, a significant fall in the proportion of patients initiating dialysis with definitive vascular access and a rise in those starting anaemic. This was not related to a change in the proportion of patients with planned starts but may be related to delayed shared decision making as a result of remote consultations and greater delays in vascular access surgery. We have identified a number of areas for service improvement.