Arteriovenous Research Articles

Renal Arteriovenous (AV) Fistula after High-Grade Blunt Renal Trauma Caused by Traffic Accidents.

To report a series of three patients with traumatic renal AV fistulas after blunt renal laceration. We retrospectively analyzed the renal trauma cases treated in the Department of Urology of Salzburg University Clinic during a time period of 10 years concerning traumatic AV fistula formation and other clinical parameters. In total, 3 cases of traumatic AV fistula formation were identified in 106 blunt renal trauma patients (2.8%), with a mean age of 39 (17-56) years. All renal traumas were classified as American Association for the Surgery of Trauma (AAST) grade IV. Two patients were primarily treated with ureteral stent; one was managed conservatively. All AV fistulas were diagnosed after a mean time of 7 (1-13) days. Two patients were symptomatic with gross hematuria, and the mean time between trauma and onset of symptoms was 11 (9-13) days. All cases were managed via coil embolization after a mean of 10 (8-13) days. Two patients received a second intervention after a mean of 18 (11-25) days. The mean AV fistula size was 18.7 (12-24) mm. Mean hemoglobin loss was 3.6 g/dL. One patient received one erythrocyte concentrate. Discharge was after a mean time of 13.3 (7-12) days, with the mean time of intensive care treatment being 2.3 (1-3) days. Traumatic renal AV fistula is a rare but severe complication associated with higher-grade renal trauma. It can become evident through hematuria or blood loss several days after the initial trauma. The availability of coil embolization in a trauma center can help kidney preservation management.

Standardized Methodology for Duplex Ultrasound Examination of Arteriovenous Access for Hemodialysis: A Proposal of the French Society of Vascular Medicine and the French-Speaking Society of Vascular Access.

Duplex ultrasound (DUS) is an essential tool for characterizing and monitoring arteriovenous (AV) access for hemodialysis. The aim of the work described here, requested by the French Society of Vascular Medicine in collaboration with the French-Speaking Vascular Access Society, is to propose a standardized methodology for performing and documenting DUS, taking into account the variety of AV access techniques and the problems routinely encountered. A steering committee reviewed the literature and selected the relevant references. A draft was prepared, and all items with missing or conflicting data were submitted to a Delphi consensus. The final document was discussed and approved by all participants. The principles of DUS evaluation of AV access consist of examination of the afferent artery, the anastomosis and the entire venous drainage system. DUS uses B-mode ultrasound, color flow, pulsed wave and power Doppler analysis. DUS can be used in a variety of clinical situations, which can directly influence the methodology of the examination and the interpretation of the results. Blood flow should be assessed as it correlates with the risk of thrombosis. The measurement should be adapted to the different anatomical and hemodynamic conditions encountered. Characterization of stenosis should take into account the residual diameter of the drainage vein and its hemodynamic consequences. Other complications can be assessed with a standardized DUS examination. When performed according to a rigorous methodology, DUS of the AV access allows a comprehensive assessment of its functionality and eliminates the need for further invasive diagnostic procedures.

Patency and Durability of Stent Grafts Placed in the Dialysis Circuit Cannulation Zone

PurposeTo investigate the safety, durability, and patency rates of stent grafts (SGs) placed in the cannulation zone of hemodialysis access circuits. Materials and MethodsFrom April 2020 to April 2023, all procedures with SGs placed in the cannulation zone were retrospectively analyzed. A total of 40 patients (25 men and 15 women) with SGs placed in the cannulation zone were included in the study. Mean age of the patients was 70 years. The Covera covered stent (BD, Franklin Lakes, New Jersey) was used in all cases. Of these, 26 were arteriovenous (AV) fistulae and 14 were AV grafts. SGs were placed for residual stenosis, perforation, aneurysm, and thrombosis. Follow-up outcomes were determined using follow-up angiographic images and included primary patency, primary-assisted patency, and secondary patency. ResultsThe primary patency of the target lesion was 89% (SD ± 5) and 74% (SD ± 8.4) at 6 and 12 months, respectively. The primary-assisted patency was 89% (SD ± 5.2) and 78% (SD ± 7.6) at 6 and 12 months, respectively. Secondary patency of the access circuit was 97% (SD ± 2.5) at both 6 and 12 months. Mean follow-up was 332 days (range, 28–661 days). All SGs were successfully cannulated for hemodialysis. No cases of stent fracture or stent infection were observed during follow-up. ConclusionsSGs placed for cannulation zone pathologies can be safely cannulated for dialysis and have adequate short- and mid-term patency rates.

Recent evaluation by nephrologists is associated with decreased incidence of tunneled dialysis catheter being used at the time of first arteriovenous access creation

ObjectiveLate primary care provider (PCP) or nephrologist evaluation of patients with progressive kidney disease may be associated with increased morbidity and mortality. Among patients undergoing initial arteriovenous (AV) access creation, we aimed to study the relationship of recent PCP and nephrologist evaluations with perioperative morbidity and mortality. MethodsWe performed a retrospective review of patients from 2014 to 2022 who underwent initial AV access creation at an urban, safety-net hospital. Univariable and multivariable analyses identified associations of PCP and nephrologist evaluations <1 year and <3 months before surgery, respectively, with hemodialysis initiation via tunneled dialysis catheters (TDCs), 90-day readmission, and 90-day mortality. ResultsAmong 558 patients receiving initial AV access, mean age was 59.7 ± 14 years, 59% were female gender, and 60.6% were Black race. Recent PCP and nephrology evaluations occurred in 386 (69%) and 362 (65%) patients, respectively. On multivariable analysis, unemployed and uninsured statuses were associated with decreased likelihood of PCP evaluation (unemployment: odds ratio [OR], 0.51; 95% confidence interval [CI], 0.34-0.77; uninsured status: OR, 0.05; 95% CI, 0.01-0.45) and nephrologist evaluation (unemployment: OR, 0.63; 95% CI, 0.43-0.91; uninsured status: OR, 0.22; 95% CI, 0.06-0.83) (all P < .05). Social support was associated with increased likelihood of PCP evaluation (OR, 1.81; 95% CI, 1.07-3.08) (all P < .05). Hemodialysis was initiated with TDCs in 304 patients (55%). Older age (OR, 0.98; 95% CI, 0.96-0.99), obesity (OR, 0.38; 95% CI, 0.25-0.58), and nephrologist evaluation (OR, 0.12; 95% CI, 0.08-0.19) were independently associated with decreased hemodialysis initiation with TDCs in patients receiving an initial AV access (all P < .05). Ninety-day readmission occurred in 270 cases (48%). Cirrhosis (OR, 2.5; 95% CI, 1.03-6.03; P = .04), coronary artery disease (OR, 2.31; 95% CI, 1.5-3.57), prosthetic AV access (OR, 1.84; 95% CI, 1.04-3.26), and impaired ambulation (OR, 1.75; 95% CI, 1.15-2.66) were independently associated with increased readmission (all P < .05). Older age (OR, 0.98; 95% CI, 0.97-0.99), prior TDC (OR, 0.65; 95% CI, 0.45-0.94), and unemployment (OR, 0.58; 95% CI, 0.39-0.86) were associated with decreased readmission (all P < .05). Ninety-day mortality occurred in 1.6% of patients. Neither PCP nor nephrologist evaluation was associated with readmission or mortality. ConclusionsRecent nephrology evaluation was associated with reduced hemodialysis initiation with TDCs among patients undergoing initial AV access creation. Unemployed and uninsured statuses posed barriers to accessing nephrology care.

Efficacy and safety of low dose, weight-based subcutaneous enoxaparin protocol in recurrent arteriovenous access thrombosis.

This study aims to evaluate the safety and efficacy of a short-term, low dose, weight-based subcutaneous enoxaparin protocol (SEP) in maintaining the patency of arteriovenous (AV) access with recurrent thrombosis. Prospective follow-up of 25 patients who presented to a tertiary institution with recurrent AV access thrombosis and treated with anticoagulation according to SEP following successful thrombectomy. Patency and safety outcomes of SEP were studied. The participants were 66.4 ± 10.2 years old and predominantly male (60%) and of Chinese ethnicity (72%). The AV accesses had a median age of 1.4 (0.6, 5.6) years with 60% being non-autogenous arteriovenous access while 40% were autogenous arteriovenous access. Thrombolytic agents (urokinase (72%) or alteplase (28%)) were used in all procedures while adjunct thrombectomy device was used in only four procedures. The mean dose of enoxaparin was 36.0 ± 8.2 mg or 0.64 ± 0.1 mg/kg/day for a mean duration 30.0 days (Interquartile range: 27.5, 31.0). One patient developed minor bleeding episode. Kaplan-Meier analysis demonstrated that the mean thrombosis-free survival pre- versus post-SEP adoption was 27.3 (95% CI 17.9-36.7) versus 183.5 (95% CI 100.1-266.9) days (p < 0.001). After adjusting for the type of thrombolytic agent, use of adjunct thrombectomy device, cutting balloon, drug-coated balloon, and stent graft, SEP remained a significant factor associated with longer thrombosis-free patency (HR 0.166: 95% CI 0.070-0.392, p < 0.001). SEP appears to be a feasible and safe thromboprophylaxis method to improve thrombosis-free patency for AV access with recurrent thrombosis.

Vascular Access-Related Distal Ischemia Requiring Intervention: Frequency, Risk Factors, and Consequences.

Distal ischemia is a rare complication in patients undergoing placement of an arteriovenous (AV) fistula or AV graft. There are limited studies on its frequency, risk factors, clinical consequences, or feasibility of subsequent access. A prospective vascular access database from a large academic medical center was queried retrospectively to identify 1498 patients (mean age 56±15 years, 48% female patients, 73% Black patients) undergoing placement of at least one vascular access from 2011 to 2020. For patients who developed access-related distal ischemia requiring surgical intervention, we determined the frequency of distal ischemia, clinical risk factors, and subsequent outcomes. Severe access-related distal ischemia occurred in 28 patients (1.9%; 95% confidence interval, 1.3% to 2.7%). The frequency was 0.2% for forearm AV fistulas, 0.9% for upper arm AV fistulas, 2.4% for forearm AV grafts, 2.2% for upper arm AV grafts, and 2.8% for thigh AV grafts. Risk factors independently associated with distal ischemia included female sex (odds ratio [OR], 3.64 [95% confidence interval, 1.52 to 8.72]), peripheral vascular disease (OR, 6.28 [2.84 to 13.87]), and coronary artery disease (OR, 2.37 [1.08 to 5.23]). Surgical interventions included ligation, excision, plication (banding), and other surgical procedures. Five patients developed tissue necrosis. A subsequent AV graft was placed in 13 patients, of whom only one (8%) developed distal ischemia requiring intervention. Access-related distal ischemia requiring intervention was rare in this study and more common in women and patients with peripheral vascular disease or coronary artery disease. In some cases, a subsequent vascular access could be placed with a low likelihood of recurrent distal ischemia.

Pulmonary Hypertension in Patients of Chronic Kidney Disease on Maintenance Hemodialysis: Study from a Tertiary Care Center in Central India

To study the incidence of pulmonary hypertension (PH) in chronic kidney disease (CKD) stage V patients on maintenance hemodialysis (HD) at our center. To compare clinical and metabolic variables among CKD patients with and without PH to search for possible etiologic factors. Comparison of PH in CKD patients at baseline and after 3 months of sildenafil therapy. The study was conducted in the Department of Nephrology, Sri Aurob-indo Institute of Medical Sciences, Indore, for a period of 1 year from December 2021 to November 2022. All CKD patients on maintenance HD at our center were included in the study. A pre-structured proforma was used to record patient data. Detailed clinical examination, 2DECHO, and Biochemical tests were done. All patients with mean pulmonary artery pressure (mPAP) &gt; 25 mmHg on 2D echocardiography were considered to have PH and were started on sildenafil therapy 20 mg three times a day for 3 months. PH was classified as mild PH (mPAP &gt; 25 up to 40 mmHg), moderate PH (mPAP &gt; 40 mmHg to 60 mmHg), and severe PH (mPAP &gt; 60 mmHg). Patients were then followed for 3 months to look for episodes of dyspnea and emergency admissions and reassessed after 3 months by repeat 2D echocardiography to find improvement in PH. A total of 102 patients were analyzed during the study period; among them, 40 patients (39.2%) had PH. Out of them, 18 patients (45%) had mild PH, 14 patients (35%) had moderate PH, and 8 patients (20%) patients had severe PH. Average age of our patients was 48.8 ± 9.4 years, the majority being men. On comparing the clinical features between patients with and without PH, none of the clinical parameters had any statistically significant impact on PH. Also, none of the laboratory parameters had statistical significance among PH and non-PH groups. Among the patients with PH, 25 patients (62.5%) had Arteriovenous (AV) fistula, 10 patients (25%) had temporary dialysis catheters. Eight patients (20%) had jugular catheters, two patients (5%) had femoral catheters, and 5 (12.5%) patients had tunneled jugular catheters. Initially, 102 patients were enrolled in the study. Of these, 40 (39.2%) had PH and 62 (60.7%) did not. Patients who had PH started sildenafil 20 mg three times a day. Of these 40 patients, at 3 months, eight patients were lost to follow-up, and 32 patients with PH remained in the study. Emergency admissions in each group of PH declined after 3 months, and the result was statistically significant. Echocardiographic findings were compared in patients with PH and without PH, but the difference in patients on HD with PH and without PH was not statistically significant. PH is a significant problem in CKD patients on HD. This issue needs to be evaluated in a timely manner to avoid the risk of morbidity and mortality. It is vital to treat them at the earliest to prevent life-threatening complications.

Risk factors for infection in patients with a failed kidney allograft on immunosuppressive medications.

Patients with a failing kidney allograft are often continued on immunosuppression (IS) to preserve residual kidney function and prevent allosensitization. It has been previously accepted that maintaining patients on immunosuppressive therapy results in an increased risk of infection, hospitalization, and mortality. However, as the management of IS in patients with a failed kidney allograft continues to evolve, it is important to review the data regarding associations between infection and specific immunosuppression regimens. We present a review of the literature of failed kidney allograft management and infection risk, and discuss practices for infection prevention. Fifteen studies, published from 1995 to 2022, which investigated the experience of patients with failed allograft and infection, were identified. Infection was most commonly documented as a general event, but when specified, included infections caused by Candida, Mycobacterium tuberculosis, and Aspergillus. In addition, the definition of reduced "IS" varied from decreased doses of a triple drug regimen to monotherapy, whereas others did not specify which medications patients were receiving. Despite attempts at lowering net immunosuppression, patients with failed allografts remain at risk of acquiring opportunistic and non-opportunistic infections. Although opportunistic infections secondary to IS are expected, somewhat surprisingly, it appears that the greatest risk of infection may be related to complications of dialysis. Therefore, mitigating strategies, such as planning for an arteriovenous (AV) fistula over a hemodialysis catheter placement, may reduce infection risk. Additional studies are needed to provide more information regarding the types and timing of infection in the setting of a failed kidney allograft. In addition, more data are needed regarding specific medications, doses, and timing of taper of IS to guide future patient management and inform strategies for infection surveillance and prophylaxis.

Prospective, Multicenter, Observational Study to Evaluate a Cell-Impermeable Endoprosthesis for Treatment of Stenosis or Occlusion within the Dialysis Outflow Circuit of an Arteriovenous (AV) Fistula or AV Graft (The WRAP Registry)

PurposeDysfunctional vascular access due to stenosis/occlusion within the arteriovenous fistula or graft (AVF/AVG) negatively affects the clinical management of patients undergoing hemodialysis. Results from the feasibility study of the WRAPSODY™ Cell-Impermeable Endoprosthesis demonstrated that the device can achieve high patency rates and maintain integrity of the dialysis outflow circuit. This study was designed to assess real-world evidence of safety and efficacy outcomes following device placement.Materials and MethodsThis is a prospective, multicenter, non-investigational, post-market observational study of 500 patients at up to 50 centers worldwide with a mature AVF/AVG dialysis access (≥ 1 hemodialysis session) who experience stenosis/occlusion of the outflow circuit prior to placement of WRAPSODY. Patients will be divided into the following two cohorts: peripheral or central thoracic. Primary outcome measures include target lesion primary patency (TLPP) at 6 months and procedure and/or device-related events through 30 days post-procedure. Secondary outcome measures include TLPP, safety events, and the number of interventions needed to maintain patency through the 24 month study period. Exploratory endpoints include time to access abandonment, resumption of successful dialysis, functional patency, and pending available imaging data, any incidence of stent fractures, migration, or edge stenosis. Study enrollment began in June 2022, the last patient visit is expected in 2026.DiscussionIt is expected that this study will provide real-world evidence regarding the performance of the WRAPSODY device in a diverse population of patients, which may encourage its use in the continuum of hemodialysis access management.Trial RegistrationNCT05062291Graphical

Mural Serum Response Factor (SRF) Deficiency Provides Insights into Retinal Vascular Functionality and Development.

Serum response factor (SRF) controls the expression of muscle contraction and motility genes in mural cells (MCs) of the vasculature. In the retina, MC-SRF is important for correct angiogenesis during development and the continuing maintenance of the vascular tone. The purpose of this study was to provide further insights into the effects of MC SRF deficiency on the vasculature and function of the mature retina in SrfiMCKO mice that carry a MC-specific deletion of Srf. Retinal morphology and vascular integrity were analyzed in vivo via scanning laser ophthalmoscopy (SLO), angiography, and optical coherence tomography (OCT). Retinal function was evaluated with full-field electroretinography (ERG). We found that retinal blood vessels of these mutants exhibited different degrees of morphological and functional alterations. With increasing severity, we found vascular bulging, the formation of arteriovenous (AV) anastomoses, and ultimately, a retinal detachment (RD). The associated irregular retinal blood pressure and flow distribution eventually induced hypoxia, indicated by a negative ERG waveform shape. Further, the high frequency of interocular differences in the phenotype of individual SrfiMCKO mice points to a secondary nature of these developments far downstream of the genetic defect and rather dependent on the local retinal context.

Functional Impairment is Associated with Poor Long-Term Outcomes after Arteriovenous Access Creation

Functional impairment affects outcomes after a variety of procedures. However, the impact of functional impairment on outcomes of arteriovenous (AV) access creation is unclear. We aimed to evaluate the association of patients' ability to ambulate and perform activities of daily living (ADL) with AV access outcomes. We retrospectively reviewed patients undergoing AV access creation at an urban, safety-net hospital from 2014-2022. We evaluated associations of impaired ambulatory and assisted ADL status with 90-day readmission, 1-year primary patency, and 5-year mortality. Among 689 patients receiving AV access, mean age was 59.6 ± 13.9 years, 59% were male, and 60% were Black. Access types included brachiocephalic (42%), brachiobasilic (26%), radiocephalic (14%), other autogenous (5%) fistulas and prosthetic grafts (13%). Impaired ambulatory status was identified in 35% and assisted ADL status, when assessed, was identified in 21% of patients. Ninety-day readmission was more likely in patients with impaired ambulatory (58% vs. 39%, P<.001) and assisted ADL (56% vs. 41%, P=.004) status. On Kaplan-Meier analysis, 1-year primary patency was lower for patients with impaired ambulatory status (44% ± 3% vs. 29% ± 3%, P=.001), but was not significantly different for patients with assisted ADL status (41% ± 3% vs. 32% ± 5%, P=.12). Five-year survival was lower for patients with impaired ambulatory status (53% ± 5% vs. 74% ± 4%, P<.001), but was not significantly different for patients with assisted ADL status (45% ± 9% vs. 71% ± 4%, P=.1). On multivariable analysis, increased likelihood of 90-day readmission was significantly associated with impaired ambulatory status (OR 2.03, 95% CI 1.4-2.94, P<.001) and assisted ADL status (OR 1.66, 95% CI 1.07-2.57, P=.02). One-year primary patency was not significantly associated with impaired ambulatory (HR 1.25, 95% CI .98-1.6, P = .07) or assisted ADL status (HR 1.13, 95% CI .87-1.48, P=.36). Increased likelihood of 5-year mortality was associated with impaired ambulatory (HR 1.65, 95% CI 1.04-2.62, P=.04) and assisted ADL status (HR 2.63, 95% CI 1.35-5.11, P=.004). Impaired ambulatory and assisted ADL status were associated with increased readmissions and long-term mortality after AV access creation. Approximately half of patients with functional impairment were not alive at 5 years. Setting outcome expectations as well as prospectively examining the impact of physical therapy and visiting nursing services for functionally impaired patients undergoing AV access creation are warranted.

Rural general surgeon confidence with managing vascular emergencies: A national survey.

Life and limb threatening vascular emergencies often present to rural hospitals where only general surgery services are available. It is known that Australian rural general surgical centres encounter 10-20 emergency vascular surgery procedures annually. This study aimed to assess rural general surgeons' confidence managing emergent vascular procedures. A survey was distributed to Australian rural general surgeons to determine their confidence (Yes/No) in performing emergent vascular procedures including limb revascularisation, revising arterio-venous (AV) fistulas, open repair of ruptured abdominal aortic aneurysm (AAA), superior mesenteric artery (SMA)/coeliac embolectomy, limb embolectomy, vascular access catheter insertion and limb amputation (digit, forefoot, below knee and above knee). Confidence level was compared with surgeon demographics and training. Variables were compared using univariate logistic regression. Sixteen per cent (67/410) of all Australian rural general surgeons responded to the survey. Increased age, years since fellowship and training prior to 1995 (when separation of Australian vascular and general surgery occurred) were associated with greater confidence in limb revascularisation, revising AV fistulas, open repair of ruptured AAA, SMA/coeliac embolectomy, and limb embolectomy (p < 0.05). Surgeons who completed >6 months of vascular surgery training were more comfortable with SMA/coeliac embolectomy (49% vs. 17%, p = 0.01) and limb embolectomy (59% vs. 28%, p = 0.02). Confidence in performing limb amputation was similar across surgeon demographics and training (p > 0.05). Recently graduated rural general surgeons do not feel confident in managing vascular emergencies. Additional vascular surgery training should be considered as part of general surgical training and rural general surgical fellowships.

The impact of neighborhood social disadvantage on presentation and management of first-time hemodialysis access surgery patients

ObjectivesThe impact of social determinants of health on the presentation, management, and outcomes of patients requiring hemodialysis (HD) arteriovenous (AV) access creation have not been well-characterized. The Area Deprivation Index (ADI) is a validated measure of aggregate community-level social determinants of health disparities experienced by members living within a community. Our goal was to examine the effect of ADI on health outcomes for first-time AV access patients. MethodsWe identified patients who underwent first-time HD access surgery in the Vascular Quality Initiative between July 2011 to May 2022. Patient zip codes were correlated with an ADI quintile, defined as quintile 1 (Q1) to quintile 5 (Q5) from least to most disadvantaged. Patients without ADI were excluded. Preoperative, perioperative, and postoperative outcomes considering ADI were analyzed. ResultsThere were 43,292 patients analyzed. The average age was 63 years, 43% were female, 60% were of White race, 34% were of Black race, 10% were of Hispanic ethnicity, and 85% received autogenous AV access. Patient distribution by ADI quintile was as follows: Q1 (16%), Q2 (18%), Q3 (21%), Q4 (23%), and Q5 (22%). On multivariable analysis, the most disadvantaged quintile (Q5) was associated with lower rates of autogenous AV access creation (OR, 0.82; 95% confidence interval [CI], 0.74-0.90; P < .001), preoperative vein mapping (OR, 0.57; 95% CI, 0.45-0.71; P < .001), access maturation (OR, 0.82; 95% CI, 0.71-0.95; P = .007), and 1-year survival (OR, 0.81; 95% CI, 0.71-0.91; P = .001) compared with Q1. Q5 was associated with higher 1-year intervention rates than Q1 on univariable analysis, but not on multivariable analysis. ConclusionsThe patients undergoing AV access creation who were most socially disadvantaged (Q5) were more likely to experience lower rates of autogenous access creation, obtaining vein mapping, access maturation, and 1-year survival compared with the most socially advantaged (Q1). Improvement in preoperative planning and long-term follow-up may be an opportunity for advancing health equity in this population.

#6167 THERAPEUTIC PLASMA EXCHANGE AS A TOOL IN THE TREATMENT OF NEUROLOGICAL DISEASES: A SINGLE CENTER EXPERIENCE

Abstract Background and Aims Plasmapheresis is an extracorporeal technique that removes immunological active substances, such as antibodies or immune complexes, from plasma. Simultaneously, it can provide essential factors in deficit, when supplementing with plasma. Therapeutic plasma exchange (TPE) can be used in numerous diseases with systemic involvement and, more recently, it has assumed an increasingly relevant role in the treatment of neurological diseases. Our aim was to review neurological indications, technique prescription, clinical outcomes and complications of these procedures. Methods We conducted an observational retrospective single-center study of the neurological diseases treated with TPE in our unit. We analyzed all procedures performed between January 2010 and December 2012 and collected indications, technical factors, complications and clinical outcomes of all treatments conducted. TPE was performed removing 1 to 1.5 of plasma volume per session. All procedures used Human Albumin 5% as replacement fluid and two units of fresh frozen plasma (FFP) were given in the end of each session. Hypocoagulation of the extracorporeal circuit was maintained with unfractionated heparin. Results Seventy-seven cycles of TPE (a total of 421 procedures) were performed on 45 patients [55.6% female; median age of 51 years (SD±16.8)]. The main indications of TPE in neurological diseases included myasthenia gravis (n = 35), Anti-N-methyl-d-aspartate (NMDA) encephalitis (n = 7), Guillain-Barré syndrome (n = 7), neuromyelitis optica spectrum disorders (n = 6), acute disseminated encephalomyelitis (n = 5), paraneoplastic syndromes (n = 4) and multiple sclerosis (n = 2). Intravenous immunoglobulin was given before TPE in 25 cases, 34 patients were on steroid and 6 patients had received pyridostigmine. Eighteen patients had coadjuvant immunosuppression [Mycophenolate mofetil or Azathioprine (n = 13), Rituximab (n = 3), tacrolimus (n = 1), Tocilizumab (n = 1) or Eculizumab (n = 1)]. The median number of TPE sessions per patient was 5 (range 1-20) and most cycles (63.6%) were performed every day for 3 sessions and 2 sessions every other day. Most of TPE (59.7%) was performed in ward, 27.3% in Intensive Care Unit (ICU) and 10 treatments were conducted in ambulatory. Near 84% of treatments were done through central venous catheters (CVC) and one patient had an arteriovenous (AV) fistula. Twenty-four (5.7%) complications were seen in 421 procedures. These complications were infection (18.2%), catheter-related (7.8%) and allergic reactions (1.3%). TPE procedure was terminated in 7.8% of sessions depending on these complications. Overall responses to TPE were noted in 81.8% of patients and 6 patients had at least one relapse during follow-up. Conclusion TPE is an effective and safe treatment option in several neurologic diseases. In our center, principal indications for TPE were myasthenia gravis, NMDA encephalitis and Guillain-Barré syndrome. In this study, clinical outcomes were favorable in the majority of the cases, with a minimum rate of complications per procedure. Therefore TPE should be considered in an early phase of presentation of disease. In relapsing diseases like myasthenia gravis, refractory to immunosuppression therapy, an AV fistula could be an alternative access to minimize the CVC-related complications.

#6904 EVALUATION OF KIDNEY FUNCTION GRAPH SURVEILLANCE ACROSS SOUTH WEST WALES, UK

Abstract Background and Aims For people requiring Kidney Replacement Therapy (KRT) late presentation to a nephrologist (within 90 days of initiating KRT) is associated with adverse outcomes. The ASSIST-CKD kidney function graph surveillance (KFGS) quality improvement project was adopted by the Department of Nephrology in South West (SW) Wales, UK in November 2017. Between the end of 2017 and the end of 2020, late presentation rates reduced from 19.5% [1] to 13.5% [2] across the region, having reduced to 9.7% in 2019 [3]. During KFGS, graphs of eGFR over time are generated for patients &amp;lt;65 years with eGFR ≤50ml/min/1.73 m2 and ≥65 years with eGFR ≤40ml/min/1.73 m2 with significantly deteriorating kidney function. ‘Alerts’ are sent to the GP for review and/or referral to nephrology. Over 100,000 graphs have been reviewed in SW Wales. We present demographic and initial outcome data for patients identified by KFGS. Method An observational retrospective cohort study analysed data of patients identified through KFGS in SW Wales between 1/11/17 and 1/10/21. Data were extracted from ASSIST-CKD and renal (Vital Data) databases using SQL coding. Results Data pertaining to 4811 patients are included for analysis. 44% of patients were male. At initial eGFR the mean age of patients ‘flagged’ was 73 years. The mean [range] initial eGFR was 32ml/min/1.73 m2 [2-50]. The median time [range] from initial eGFR to KFGS alert was 8 days [2-113]. For those with results within 90 days of initial eGFR the mean initial haemoglobin (Hb) was 118 g/L. The mean serum potassium was 4.7 mmol/L. Data for 1144 (24%) patients were included for outcome analysis, where a clear timeline from initial eGFR to KFGS alert, first registration with the nephrology service (registration), and outcome could be established. 3667 patients were excluded from outcome analysis because they were registered before KFGS or were not registered with nephrology, had died or moved out of area after KFGS alert. The median time [range] from alert to registration was 22 days [0-1636]. 20% of patients (n = 232) received CKD education from a specialist nurse. The median time [range] from registration to first contact from a CKD education nurse was 349 days [8-1419]. 34% of patients received IV iron and 31% received an erythropoiesis-stimulating agent (ESA) after alert. The median time [range] from registration to first IV iron and first ESA was 257 [5-1705] and 277 [3-1650] days respectively. 6% (n = 71) of patients required KRT. The late presentation rate was 22.5%. 21% of patients needing haemodialysis (HD) received their first treatment via an arteriovenous (AV) fistula, 1% via AV graft, 59% via non-tunnelled line and 19% via tunnelled line. 44% (7/16) of patients presenting late died within 90 days of starting KRT. 33% (18/55) of patients died within 90 days of starting KRT if they presented to a nephrologist ≥90 days before starting KRT. Conclusion Late presentation rates have reduced in SW Wales since implementing KFGS. The relatively high late presentation rate and low rate of initial definitive access for HD in the present data requires further analysis. eGFR values that prompted alert may denote Acute Kidney Injury (AKI) as opposed to, or as well as CKD progression; increasing the urgency of referral to nephrology. eGFR values pre and post alert will be reviewed to elucidate this. Patients presenting late were more likely to die within 90 days of starting KRT than those presenting early, emphasising the importance of early identification of progressive kidney disease. We aim to compare present data with a cohort referred to nephrology independent of KFGS to inform renal centres of the benefits of KFGS beyond headline late presentation rates, including timely access to specialists. We will consider potentially unwelcome consequences of KFGS, such as inappropriate referral. We cannot draw conclusions of causality between KFGS and outcomes. The GP may not have seen the alert, and there are several reasons why a GP may decide not to refer to nephrology following a KFGS alert.

Patency of arteriovenous fistulas and grafts for dialysis access: An analysis using the Korean National Health Insurance Service database from 2008 to 2019.

Arteriovenous (AV) access practice and its outcomes vary internationally. To provide a better understanding of the patterns and outcomes of AV access creation, we investigated the patency and risk factors of arteriovenous fistulas (AVFs) and grafts (AVGs) as initial AV access in the Korean adult population using data from the last 10 years. The National Health Insurance Service database was queried retrospectively to identify patients undergoing hemodialysis with AVFs and AVGs as well as their clinical characteristics and outcomes from 2008 to 2019. AV access patency and its associated risk factors were evaluated. During the study period, 64,179 AVFs and 21,857 AVGs were placed. The mean patient age was 62.6 ± 13.6 years (21.5% were ⩾75 years old), and 39.3% patients were women. More than half of the patients underwent AV access creation at tertiary care hospitals. At 1 year, the primary, primary assisted, and secondary patency rates were 62.2%, 80.7%, and 94.2% for AVFs, and 46.0%, 68.4%, and 86.8% for AVGs, respectively. AVG, older age, female sex, diabetes, and creation at general hospitals (vs tertiary hospitals) were associated with decreased patency outcomes (all, p < 0.05). This study using national data showed that three quarters of patients with AV access had AVF and AVF showed superior performance to AVG and identified several patient and center factors related to AV access patency in Korea.

P92: Arterio-Venous Bridge for Peripheral Veno-Arterial Extracorporeal Membrane Oxygenation Weaning in Adults

Background: The timing for liberation of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) can be challenging. Various ECMO weaning strategies have been described in the literature. Arterio-venous (AV) bridge has been deployed successfully in the pediatric population but remains underutilized in adults. This case study illustrates the usefulness of AV bridge technique in adult VA-ECMO weaning trial. Method: Arterio-venous bridge is a weaning modality that allows the patient to be temporarily fully removed from VA-ECMO therapy while maintaining the ECMO circuit integrity and enabling the immediate resumption of ECMO therapy. The technique of AV bridge is described in Picture 1 and clinical data, including diagnosis, hemodynamics, biomarkers, are included in Table 1. We present two cases of adult VA-ECMO weaning trial utilizing AV bridge. Result: One patient who had previously undergone a failed VA-ECMO weaning trial initially was subsequently weaned and successfully decannulated utilizing the AV bridge technique. The second patient was able to tolerate AV bridge off pump trial up for two hours but became hypoxic and acidotic, and eventually placed back on VA-ECMO. With no evidence of recovery and poor candidacy for advanced therapies, patients was transitioned to comfort care. Conclusion: Arterio-venous bridge is a safe and effective method to wean from VA-ECMO in adult patients. It not only allows clinicians to monitor patient’s hemodynamics when patient is fully off VA-ECMO support, but also retains the capability of immediate therapy resumption if patient fails the wean.Figure 1. The technique of AV bridge Table 1. - Patients’ Characteristics, Hemodynamics and Biomarkers when off ECMO Patient Diagnosis Hemodynamics Biomarkers Pressor Requirement MAP CVP PA Lactate PaO2 PaCO2 58 yo M Hemorrhagic Shock s/p OHT 71 12 34/25 =0.9 111 38 = 60 yo F Cardiogenic shock 2/2 CTEPH 70 10 88/49 ↑2.9 57 55 ↑↑↑

BIO11: Ambulatory Rabbit ECLS Model for Long-term Biocompatibility Testing

Background: Thrombosis causes rapid failure of oxygenators within extracorporeal life support (ECLS) circuits. To combat this problem, various groups are developing new surface coatings and anticoagulants, but their testing typically relies on either (a) inexpensive, but overly-brief (< 8 hour) in vitro or small animal in vivo testing or (b) expensive, long-term (days to weeks) testing in large animals. A more inexpensive model is thus needed to assess the long-term biocompatibility of new anticoagulant technologies. In this study, the feasibility of a long-term, ambulatory rabbit ECLS model was assessed. Methods: A miniaturized ECLS circuit was attached to rabbits (2.5-4 kg) under anesthesia using a pumpless arteriovenous (AV) configuration. The circuit contained a miniature artificial lung (surface area of 400 cm2) using the same materials as full-scale artificial lungs. The circuit was tunneled behind the animal’s back and secured just below the scruff of the neck. IV heparin was provided via a battery-powered infusion pump (SAI 3D Mini Infusion Pump) within a small jacket. Twelve non-recovery experiments were used to optimize the model, and two subsequent recovery experiments were run until oxygenator failure (blood flow rate below 5 mL/min for over 2 hours and/or resistance > 5x baseline). Non-recovery experiments were used to optimize the cannulation strategy. This included cannula type and circuit placement on the rabbit. Once optimized, two survival studies were performed. The average circuit blood flow during the first experiment was 50-60 mL/min. The circuit blood flow was then limited to 35-45 mL/min with a Hoffman clamp for the second experiment. Blood flow resistance was measured to assess anticoagulation effectiveness, and physiology was monitored through hepatic and renal panels. Results: Bilateral cannulation was ideal for circuit placement. A flexible 16G single-lumen central line was chosen because of its low blood flow resistance and resistance to kinking. The circuit was tunneled 40 cm, emerging just below the scruff. This enabled safe handling of the animal without impacting its mobility and ability to eat. The recovery experiments lasted 47 and 21 hours prior to oxygenator failure. Animals were completely ambulatory with free access to food and water. Heparin delivery could be controlled simply using the infusion pump, and coagulation could be assessed by drawing blood samples and measuring oxygenator resistance. The first survival rabbit developed hyperlipidemia on Day 1. The cause is unclear at this time but could be attributed to high blood flow through AV circuit. Conclusion: This study demonstrates the feasibility of using a lower-cost rabbit model for long-term anticoagulation testing that requires less staffing. Future studies will use this model to compare the anticoagulation effectiveness of heparin, a selective Factor XIIa inhibitor, and surface coatings for a period of five days.

Dialysis Access-Associated Steal Syndrome and Management.

Dialysis-associated steal syndrome (DASS) occurs in 1-8% of hemodialysis patients with arteriovenous (AV) access. Major risk factors include use of the brachial artery for access creation, female sex, diabetes, and age > 60years. DASS carries severe patient morbidity including tissue or limb loss if not recognized and managed promptly, as well as increased mortality. Diagnosis of DASS requires a directed history and physical exam supported by non-invasive testing. Prior to definitive therapy, detailed arteriography, fistulography, and flow measurements are performed to delineate underlying etiologies and guide management. To optimize success, DASS treatment should be individualized according to access location, underlying vascular disease, flow dynamics, and provider expertise. Possible causes of DASS include extremity inflow or outflow arterial occlusive disease, high AV access flow rate, and reversal of distal extremity arterial blood flow; DASS may also exist without any of the prior features. Depending on the DASS etiology, various endovascular and/or surgical interventions should be considered. Regardless, in the majority of patients presenting with DASS, access preservation can be achieved.

Characterization of Long-term Survival in Medicare Patients Undergoing Arteriovenous Hemodialysis Access

Patients undergoing arteriovenous (AV) access creation for hemodialysis (HD) often have significant comorbidities. Our goal was to quantify the long-term survival and associated risk factors for long-term mortality in these patients to aid in optimization of goals and expectations. The Vascular Implant Surveillance and Interventional Outcomes Network (VISION) Vascular Quality Initiative Medicare–linked data were used to assess long-term survival in the HD registry. Demographics, comorbidities, and interventions were recorded. As the majority of HD patients are provided Medicare, Medicare linkage was used to obtain survival data. Multivariable analysis was used to identify independent associations with mortality. A total of 13,945 AV access patients were analyzed: 10,872 (78%) AV fistulas and 3073 (22%) AV grafts. Patients receiving an AV fistula were more often younger, male, White, obese, independently ambulatory, preoperatively living at home, have fewer comorbidities, and less often have a prior AV access and tunneled dialysis catheters (P < .05 for all). The 5-year mortality overall was 62.9%, with 61.2% for AV fistulas and 68.8% for AV grafts (P < .001). On multivariable analysis, nonambulatory status (hazard ratio [HR]: 1.67, 95% confidence interval [CI]: 1.53-1.83; P < .0001), lower extremity access (HR: 1.67, 95% CI: 1.35-2.05; P < .0001), HIV/AIDS (HR: 1.44, 95% CI: 1.13-1.82; P = .003), White race (HR: 1.43, 95% CI: 1.35-1.51; P < .0001), current smoking (HR: 1.38, 95% CI: 1.27-1.49; P < .0001), congestive heart failure (HR: 1.33, 95% CI: 1.26-1.41; P < .0001), chronic obstructive pulmonary disease (HR: 1.23, 95% CI: 1.15-1.31; P < .0001), and AV graft placement (HR: 1.12, 95% CI: 1.02-1.23; P = .016) were associated with poor survival. Long-term survival in Medicare patients undergoing AV access creation is poor with nearly two-thirds of patients having died at 5 years. Further research focusing on modifiable risk factors in this population is warranted.