Management of vascular access inflow-outflow imbalance: A bimodal approach.

A more accurate descriptive and clinically useful diagnosis based upon pathophysiology for what is commonly referred to as venous outflow stenosis is inflow-outflow imbalance. In these cases, the total outflow capacity of the AV access is inadequate to handle the inflow volume (Qa) without an increase in pressure. The relative inadequacy of the access outflow capacity in comparison to Qa results in increased outflow resistance and a proportional increase in intraluminal pressure. The clinical indicators associated with venous stenosis are the resulting manifestations of this imbalance. The point at which this occurs is dependent upon variations in these two parameters-Qa and outflow resistance. The variations in these two parameters are considerable and reciprocal. Excessive Qa results in or can lead to an entire list of serious problems that adversely affect patient morbidity and mortality. Most studies dealing with AV access Qa reduction have been for the treatment of an existing condition rather than its prevention; however, prevention of disease rather than waiting for its development is an important tenet of medical practice. The resulting clinical picture of inflow-outflow imbalance is taken as an indication for corrective treatment. In the past, in most cases this has meant angioplasty to open the outflow if it is reduced; however, this clinical picture may be associated with an excessive Qa and angioplasty in these cases creates the risk for a further increase in Qa. It is the authors' opinion that access flow measurements should be a part of the evaluation of these cases prior to planning treatment. Using this information, a bimodal approach to primary treatment should be adopted involving either angioplasty for cases with a low or normal Qa or flow reduction in cases with an elevated Qa.

ASDIN white paper: Management of cephalic arch stenosis endorsed by the American Society of Diagnostic and Interventional Nephrology.

Brachiocephalic arteriovenous fistulas (AVF) makeup approximately one third of prevalent dialysis vascular accesses. The most common cause of malfunction with this access is cephalic arch stenosis (CAS). The accepted requirement for treatment of a venous stenosis lesion is ⩾50% stenosis associated with hemodynamically abnormalities. However, the correlation between percentage stenosis and a clinically significant decrease in access blood flow (Qa) is low. The critical parameter is the absolute minimal luminal diameter (MLD) of the lesion. This is the parameter that exerts the key restrictive effect on Qa and results in hemodynamic and functional implications for the access. CAS is the result of low wall shear stress (WSS) resulting from the effects of increased blood flow and the unique anatomical configuration of the CAS. Decrease in WSS has a linear relationship to increased blood flow velocity and neointimal hyperplasia exhibits an inverse relationship with WSS. The result is a stenotic lesion. The presence of downstream venous stenosis causes an inflow-outflow mismatch resulting in increased pressure within the access. Qa in this situation may be decreased, increased, or within a normal range. Over time, the increased intraluminal pressure can result in marked aneurysmal changes within the AVF, difficulties with cannulation and the dialysis treatment, and ultimately, increasing risk of access thrombosis. Complete characterization of the lesion both hemodynamically and anatomically should be the first step in developing a strategy for management. This requires both access flow measurement and angiographic imaging. Patients with CAS present a relatively broad spectrum as relates to both of these parameters. These data should be used to determine whether primary treatment of CAS should be directed toward the anatomical lesion (small MLD and low Qa) or the pathophysiology (large MLD and high Qa).

Two-year cumulative patency of endovascular arteriovenous fistula.

BACKGROUND AND OBJECTIVES: The recent advent of a device to create a proximal radial artery arteriovenous fistula using an endovascular approach to create the anastomosis represents a significant advance in dialysis access creation. This endovascular arteriovenous fistula offers the beneficial attributes of the proximal radial artery arteriovenous fistula while adding the advantages of avoiding a surgical procedure. The endovascular arteriovenous fistula can be created safely, functions well, has excellent patency, and has a high degree of patient satisfaction. The purpose of this study is to report the 2-year cumulative patency rate for a large multicenter cohort of endovascular arteriovenous fistula cases. DESIGN: An endovascular arteriovenous fistula was created in 105 patients using either local or regional anesthesia and conscious sedation. Patient data were obtained from each program's electronic health record system. Data collection was truncated at 2 years postprocedure and used to calculate cumulative patency. Post-access creation patient satisfaction was assessed. RESULTS: A physiologically mature arteriovenous fistula (blood flow ⩾500 mL/min and a target vein internal diameter ⩾4 mm) was obtained in 98%. A clinically functional arteriovenous fistula (supporting two-needle dialysis according to the patient's dialysis prescription) was demonstrated in 95%. Access failure resulting in the loss of access occurred in eight cases during the study period. The cumulative patency rate at 6, 12, 18, and 24 months was 97.1%, 93.9%, 93.9%, and 92.7%, respectively. The post-procedure patient evaluation emphasized a high level of patient satisfaction. CONCLUSION: The proximal radial artery arteriovenous fistula created using an endovascular approach for the anastomosis is associated with excellent 2-year cumulative patency and is associated with a high level of patient satisfaction.

ASDIN white paper: Assessment and management of hemodialysis access-induced distal ischemia by interventional nephrologists.

Although not common, hemodialysis access-induced distal ischemia is a serious condition resulting in significant hemodialysis patient morbidity. Patients with signs and symptoms suggestive of hand ischemia frequently present to the general and interventional nephrologist for evaluation. In order to care for these cases, it is necessary to understand this syndrome and its management. Most cases can be managed conservatively without intervention. Some cases requiring intervention may be treated using techniques within the scope of practice of the interventional nephrologists while other cases require vascular surgery. In order for the interventional nephrologists to evaluate and manage these cases in a timely and appropriate manner, practice guidelines are presented.

Early cannulation of percutaneously created arteriovenous hemodialysis fistulae.

INTRODUCTION: The optimal vascular access for most dialysis patients is an arteriovenous fistula and the recognized appropriate process of care for the chronic kidney disease patient is to have the access in place ready for use when renal replacement therapy is required. Unfortunately, as a result of multiple barriers, most patients start dialysis with a catheter and many experience multiple interventions. The recent advent of the percutaneous arteriovenous fistula may offer at least a partial solution to these problems. The purpose of this study was to report of the results of early cannulation of the percutaneous arteriovenous fistula. MATERIALS AND METHODS: Early cannulation, less than 14 days post creation, was performed in 14 cases in order to avoid an initial catheter or continued use of a problematic catheter for dialysis. Immediately post access creation, blood flow ranged from 491 to 1169 mL/min (mean = 790 mL/min). Ultrasound was used to map potential cannulation sites prior to use. Cannulation was performed using plastic fistula cannulas. RESULTS: Early cannulation was successful in this cohort of cases except for one cannulation complication. Dialysis treatments were otherwise uncomplicated. Primary patency at 3, 6, and 12 months was 76%, 76%, and 66%, respectively. Assisted primary patency for the same intervals was 100%, 100%, and 91%, respectively. Cumulative patency was 100% at all three-time intervals. CONCLUSION: The results of this study suggest that the possibility of successful early cannulation with a percutaneous arteriovenous fistula can be considered as an additional factor in making this access a reasonable alternative for a surgically created arteriovenous fistula in appropriate patients.

Definitions and End Points for Interventional Studies for Arteriovenous Dialysis Access.

This paper is part of the Clinical Trial Endpoints for Dialysis Vascular Access Project of the American Society of Nephrology Kidney Health Initiative. The purpose of this project is to promote research in vascular access by clarifying trial end points which would be best suited to inform decisions in those situations in which supportive clinical data are required. The focus of a portion of the project is directed toward arteriovenous access. There is a potential for interventional studies to be directed toward any of the events that may be associated with an arteriovenous access' evolution throughout its life cycle, which has been divided into five distinct phases. Each one of these has the potential for relatively unique problems. The first three of these correspond to three distinct stages of arteriovenous access development, each one of which has been characterized by objective direct and/or indirect criteria. These are characterized as: stage 1-patent arteriovenous access, stage 2-physiologically mature arteriovenous access, and stage 3-clinically functional arteriovenous access. Once the requirements of a stage 3-clinically functional arteriovenous access have been met, the fourth phase of its life cycle begins. This is the phase of sustained clinical use from which the arteriovenous access may move back and forth between it and the fifth phase, dysfunction. From this phase of its life cycle, the arteriovenous access requires a maintenance procedure to preserve or restore sustained clinical use. Using these definitions, clinical trial end points appropriate to the various phases that characterize the evolution of the arteriovenous access life cycle have been identified. It is anticipated that by using these definitions and potential end points, clinical trials can be designed that more closely correlate with the goals of the intervention and provide appropriate supportive data for clinical, regulatory, and coverage decisions.

What is the best setting for receiving dialysis vascular access repair and maintenance services?

INTRODUCTION: Advances in dialysis vascular access (DVA) management have changed where beneficiaries receive this care. The effectiveness, safety, quality, and economy of different care settings have been questioned. This study compares patient outcomes of receiving DVA services in the freestanding office-based center (FOC) to those of the hospital outpatient department (HOPD). It also examines whether outcomes differ for a centrally managed system of FOCs (CMFOC) compared to all other FOCs (AOFOC). METHODS: Retrospective cohort study of clinically and demographically similar patients within Medicare claims available through United States Renal Data System (USRDS) (2010-2013) who received at least 80% of DVA services in an FOC (n = 80,831) or HOPD (n = 133,965). Separately, FOC population is divided into CMFOC (n = 20,802) and AOFOC (n = 80,267). Propensity matching was used to control for clinical, demographic, and functional characteristics across populations. RESULTS: FOC patients experienced significantly better outcomes, including lower annual mortality (14.6% vs. 17.2%, p<0.001) and DVA-related infections (0.16 vs. 0.20, p<0.001), fewer hospitalizations (1.65 vs. 1.91, p<0.001), and lower total per-member-per-month (PMPM) payments ($5042 vs. $5361, p<0.001) than HOPD patients. CMFOC patients had lower annual mortality (12.5% vs. 13.8%, p<0.001), PMPM payments (DVA services) ($1486 vs. $1533, p<0.001) and hospitalizations ($1752 vs. $1816, p<0.001) than AOFOC patients. CONCLUSIONS: Where nephrologists send patients for DVA services can impact patient clinical and economic outcomes. This research confirmed that patients who received DVA care in the FOC had better outcomes than those treated in the HOPD. The organizational culture and clinical oversight of the CMFOC may result in more favorable outcomes than receiving care in AOFOC.

Changes in the Profile of Endovascular Procedures Performed in Freestanding Dialysis Access Centers over 15 Years.

BACKGROUND AND OBJECTIVES: Marked changes occurred in the vascular access profile of patients receiving hemodialysis in the United States over the 15-year period of 2001-2015. This study was undertaken to evaluate how these changes have affected dialysis access maintenance and salvage procedures performed in freestanding dialysis access centers and to examine the effectiveness, efficiency, and safety of these procedures in this setting. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Data were collected from freestanding, dedicated dialysis access centers operating under a common system of management. Data were available on 689,676 dialysis access procedures. Data relating to case mix, procedure outcome, procedural time, and intraprocedural and immediate postprocedural complications were analyzed. RESULTS: The arteriovenous procedure profile changed from one characterized by approximately equal numbers of angioplasties and thrombectomies performed on arteriovenous grafts (AVGs) to one characterized primarily by angioplasties performed on arteriovenous fistulas. The percentage of angioplasties performed throughout the study was significantly greater than thrombectomies, with a mean of 67.9% versus 32.1% (P<0.001). Interventional procedures did not decrease with increasing arteriovenous fistula utilization in prevalent patients receiving dialysis. The incidence roughly paralleled the increasing prevalence of this type of access. A decreasing percentage of AVG utilization resulted in a progressive, roughly parallel, but disproportionately higher, decrease in the percentage of AVG procedures (P<0.001). A progressive improvement in procedure outcomes and a decrease in complication rates and procedure times were observed (P<0.001 for each). A progressive decrease in tunneled dialysis catheter placement was also observed. CONCLUSIONS: The procedure profile treated in freestanding, dedicated dialysis access centers changed significantly over 15 years, reflecting the changes that have occurred in the vascular access profile of the dialysis population.

Angiography of Hemodialysis Fistulas and Grafts.

Angiography of the dialysis access is an important procedure in dealing with dialysis arteriovenous access (AVA) dysfunction. It is an integral part and the initiating procedure for all the interventional procedures performed for the management and salvage of dialysis AVA. The performance of this procedure and normal dialysis access-related anatomy including anatomical variants are discussed. In addition, pathology commonly encountered in association with the anatomy is reviewed.

The risk of bleeding with tunneled dialysis catheter placement.

PURPOSE: The purpose of this study was to evaluate the risk of bleeding associated with tunneled dialysis catheter (TDC) placement in a large population of hemodialysis patients who were either anticoagulated or were taking antithrombotic medications. METHODS: Medical records obtained over a two-year period were queried in order to select two groups of study cases. The first was a Med group (n = 458), cases which had a TDC placed while taking the antithrombotic medications (warfarin, clopidogrel or acetylsalicylic acid [ASA]) which were not discontinued or held. The second was a Declot Failure (DF) group (n = 941) and consisted of cases in which a TDC had been placed immediately following a failed arteriovenous access thrombectomy procedure in which they had been anticoagulated using unfractionated heparin. The results obtained in these two groups were compared to the incidence of bleeding observed in a cohort of 6555 TDC placements that had been performed previously referred to as the Control group. RESULTS: The incidence of bleeding in the Control group was 0.46%. The incidence of bleeding in the DF group was 0.44% and in the Med group was 0.36%. No patient had bleeding that required transfusion, hospitalization, or catheter removal. CONCLUSIONS: Based upon these data, it seems reasonable to classify the TDC placement procedure as having a very low risk of bleeding and to not require preprocedure laboratory testing. The value of suspending antithrombotic medications prior to TDC placement cannot be supported.

We Refuse to Give up on Nonmaturing Fistulas.

The nonmaturing arteriovenous fistula (AVF) is a major problem and can lead to significant patient morbidity and mortality because the patient is exposed to the risk of dialysis with a central venous catheter (CVC). Access planning should include a strategy to decrease the incidence of AVF nonmaturation. All newly created AVFs should be evaluated for maturation at 4-6 weeks. If it is judged to not be usable at that time, it should be evaluated for salvage. However, if multiple procedures over a prolonged period of time are necessary for salvage, the decreasing chances of long-term success with the increasing risks of CVC-based dialysis must be considered. Giving up on the nonmaturing AVF may be in the best interest of the patient.

Chronically Occluded Arteriovenous Fistula Salvaged by Sharp Needle Recanalization.

Salvage of a failed arteriovenous access with occlusion of the venous outflow and no alternative for a secondary arteriovenous fistula that would provide for immediate dialysis is a difficult problem for which there is no ideal solution. The present report is such a patient. The patient had a radial-cephalic fistula represented by only a very short segment, inadequate for effective dialysis. Salvage was accomplished using the sharp needle revascularization technique in order to avoid a prolonged period of central venous catheter use.

Role of interventional nephrology in the multidisciplinary approach to hemodialysis vascular access care.

Dialysis vascular access planning, creation, and management is of critical importance to the dialysis patient population. It requires a multidisciplinary approach involving patients and their families, dialysis facility staff, the nephrologist, the surgeon, and the interventionalist. With the emergence of interventional nephrology as a subspecialty of nephrology, the nephrologist is increasingly providing both the nephrology and interventional aspects of care, and in some areas, the surgical functions as well. Most of these interventional nephrologists work in freestanding outpatient dialysis access centers (DACs). Large clinical studies published over the past 10 years demonstrate that the interventional nephrologist can manage the problems associated with dialysis access dysfunction effectively, safely, and economically. A recently published study based upon United States Medicare claims data in which a DAC patient group (n = 27,613) and a hospital outpatient department patient group (HOPD group; n = 27,613) were compared using propensity score matching techniques showed that patients treated in the DACs had significantly better clinical outcomes (P<0.001). This included fewer vascular access-related infections (0.18 vs. 0.29), fewer septicemia-related hospitalizations (0.15 vs. 0.18), and a lower mortality rate (47.9% vs. 53.5%).

Bacterial Colonization of Thrombosed Dialysis Arteriovenous Grafts.

In the absence of obvious infection, an abandoned arteriovenous graft (AVG) is generally left in place. This has been thought to be the best solution in view of the surgical procedure that would be required for its removal. However, there are reports of occult infection in these retained AVGs that can lead to significant infectious complications. In addition, there is evidence that abandoned, retained AVGs may contribute to the inflammatory state that exist in association with dialysis patients. This observational report of 100 cases of thrombosed AVG in which the thrombus was cultured at the time of thrombectomy demonstrated a significant degree of bacterial colonization in these cases without evidence of bacteremia. It is proposed that this could be the mechanism by which occult infection in an abandoned, retained AVGs occurs.

Clinical and economic value of performing dialysis vascular access procedures in a freestanding office-based center as compared with the hospital outpatient department among Medicare ESRD beneficiaries.

Dialysis vascular access (DVA) care is being increasingly provided in freestanding office-based centers (FOC). Small-scale studies have suggested that DVA care in a FOC results in favorable patient outcomes and lower costs. To further evaluate this issue, data were drawn from incident and prevalent ESRD patients within a 4-year sample (2006-2009) of Medicare claims (USRDS) on cases who receive at least 80% of their DVA care in a FOC or a hospital outpatient department (HOPD). Using propensity score matching techniques, cases with a similar clinical and demographic profile from these two sites of service were matched. Medicare utilization, payments, and patient outcomes were compared across the matched cohorts (n = 27,613). Patients treated in the FOC had significantly better outcomes (p < 0.001), including fewer related or unrelated hospitalizations (3.8 vs. 4.4), vascular access-related infections (0.18 vs. 0.29), and septicemia-related hospitalizations (0.15 vs. 0.18). Mortality rate was lower (47.9% vs. 53.5%) as were PMPM payments ($4,982 vs. $5,566). This study shows that DVA management provided in a FOC has multiple advantages over that provided in a HOPD.

Hand ischemia associated with dialysis vascular access: an individualized access flow-based approach to therapy.

With the rise in the median age of hemodialysis patients, the increasing numbers of patients with multiple risk factors for vascular disease, and the efforts being made to increase the creation of autogenous arteriovenous fistulas (AVFs), dialysis access-related steal syndrome (DASS) has become a growing problem. This syndrome, caused by arterial insufficiency distal to the arteriovenous access due to diversion of blood into the access, is a potentially devastating complication. It is crucial that physicians who manage hemodialysis patients and perform vascular access procedures have a comprehensive understanding of the pathophysiology, symptoms, diagnostic maneuvers, and treatment options for DASS. The goals of management must be twofold-relieve the ischemia and preserve the access. The choice of any intervention, if such is necessary, should be based upon the clinical features presented by that individual patient; the clinical condition and prognosis of the patient, stage of the disease, location of the arterial anastomosis, and the level of blood flow within the access. This review presents information that supports an individualized, physiologic approach to this condition.

Radiation dose associated with dialysis vascular access interventional procedures in the interventional nephrology facility.

The number of dialysis access procedures performed by interventional nephrologists using a mobile C-arm fluoroscopy machine in freestanding centers continues to rise. With this activity comes the risk of radiation exposure to patients being treated and staff. This study was conducted to assess the levels of radiation dosage involved with these procedures. Dosimetry information including kerma area product (KAP), reference point air kerma (RPAK) and fluoroscopy time (FT) was collected prospectively. Radiation dosage data were collected from 24 centers in various parts of the United States and reflected cases managed by 69 different interventional nephrologists. The data were tabulated separately for eight procedures - fistula angioplasty and thrombectomy, graft angioplasty and thrombectomy, tunneled catheter placement and exchange, vein mapping and cases in which only angiographic evaluation was performed. The range for all of the measured parameters was large. Additionally there was considerable inter-operator variability. The dosage levels noted in this series were well below the threshold for deterministic effects. FT for AVF procedures was higher than for other types of access. The highest values were observed for thrombectomies. The highest KAP values were recorded for venous mapping. Thrombectomy procedures were associated with the highest RPAK levels. All dosage metrics were considerably lower than those previously reported.