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).

Antiphospholipid Syndrome in a Patient With Autosomal Dominant Polycystic Kidney Disease: The Surface of the Moon.

Antiphospholipid syndrome (APS) is a rare coagulopathic disorder diagnosed with a combination of clinical/imaging findings with specific antibody titer elevations over a period of 12 weeks. The following case report will discuss the unusual and challenging hospital course of a patient with extensive autosomal dominant polycystic kidney disease (ADPKD) being treated for a multi-drug resistant urinary tract infection (UTI). The patient later developed multiple deep vein thrombosis (DVT) and was found to have antiphospholipid syndrome. Warfarin, the anticoagulant of choice for antiphospholipid syndrome, has a higher likelihood of intracerebral hemorrhage than direct oral anticoagulants. This is particularly challenging since patients with autosomal dominant polycystic kidney disease have a higher propensity to develop intracranial aneurysms (ICA).

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.

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.

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.

Surgical site infection rates in dialysis patients undergoing endovascular procedures.

A surgical site infection (SSI) is an infection related to surgery that develops within 30 days after an operation or within 1 year of implant placement. Postoperative SSIs are the most common health-care-associated infections, occurring in up to 5% of surgical patients. Endovascular surgical procedures related to vascular access are common in the dialysis population and may cause SSIs. A large outpatient vascular access system developed and implemented a surveillance program to measure and monitor SSIs in their population. The health-care surveillance system extended to 76 ambulatory care centers across the United States and Puerto Rico. Based on a recorded 92,880 patient encounters, the surveillance system tabulated 12,541 valid patient survey responses documenting self-reported symptoms of infection within a 30-day postoperative period. The SSI rate was tabulated based on the presence of two or more specified indicators of infection: antibiotics, pus, dehiscence, pain, warmth, and swelling. Patients undergoing interventional procedures received surveys at discharge. Data were collected and analyzed using SPSS software. Survey analysis indicated a less than 3% superficial incisional SSI rate in hemodialysis patients undergoing endovascular procedures. The SSI rate for clean wound procedures is generally 2% or less. These data indicate that dialysis patients undergoing interventional procedures in vascular access centers may have a slightly greater risk of developing SSIs due to the presence of additional risk factors including obesity, diabetes, and age. This study was limited by a set of loose diagnostic criteria self-reported by patients, which may have overestimated the prevalence of infection. SSIs are a serious medical problem associated with increased morbidity and mortality and increased medical care costs. All providers should consider an active surveillance program following endovascular procedures given the comorbidities associated with the dialysis population.

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.

Interventional nephrology: When should you consider a graft?

The patient's vascular access is critical in ensuring that hemodialysis is successful, effective, relatively uncomplicated, and consistently reproducible from one treatment to another. The choice of vascular access is dictated by a multitude of factors, some of which are generalizable to a larger system, and others of which are flavored by local experience and expertise; an important fraction is specific to the patient presenting to the clinician at a particular point in time. Some of these factors, such as patient age and sex, are not modifiable; others, like comorbidity, vessel size and urgency of presentation to the renal provider, are manageable and sometimes modifiable. The role of the autologous arteriovenous fistula as the ideal conduit for hemodialysis treatments is well established. The role of the prosthetic graft warrants discussion and investigation to most optimally apply to patients this important alternative within the armamentarium of vascular access.

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.

The risk of sedation/analgesia in hemodialysis patients undergoing interventional procedures.

Data derived from a large cohort of hemodialysis patients (12,896) undergoing dialysis access maintenance procedures being performed by interventional nephrologists were analyzed to determine the safety of sedation/analgesia (S/A) in a freestanding facility. Data collected included patient demographics, procedures performed, time of procedures, drugs used, doses used, and complications that occurred. Four high-risk groups were identified based upon age, pulmonary status, and over all physical status. These were compared to the total cohort. Midazolam, fentanyl, or a combination of the two were used. Within the total cohort of patients, midazolam alone was used most commonly (94.7%). The total mean dose of midazolam when used alone was 3.4 mg. The dosages used in the high-risk groups tended to be only slightly lower (3-3.2 mg). This setting appears to be safe for hemodialysis patients, even those in high-risk subgroups having these types of procedures. The types of drugs and the dosages that are commonly used do not appear to be associated with an unacceptable risk to the hemodialysis patient. A nephrologist that is not specialty trained in anesthesia is able to provide S/A safely in a freestanding facility.

Excimer laser assisted angioplasty in hemodialysis access intervention.

A case is described in which an excimer laser is used to assist angioplasty of a severe central venous lesion that is refractory to conventional techniques. Modern laser technology uses the ultraviolet (UV) spectral region to generate nanosecond pulses of energy. This results in photoablation, which is the process by which energy photons cause molecular bond disruption, while minimizing thermal damage to the surrounding vascular tissues. Further investigation of excimer laser assisted angioplasty in the setting of hemodialysis access intervention is needed to rigorously define its potential role. In occlusive disease where no conventional alternative is available, however, laser therapy is a viable option.

Infection associated with tunneled hemodialysis catheters.

The use of tunneled dialysis catheters to deliver hemodialysis treatment may be associated with major problems. For this reason their use should be minimized as much as possible. Infection is the most serious of these problems. This complication causes very significant morbidity and mortality and has emerged as the primary barrier to long-term catheter use. Bacteremia is the most serious type of infection associated with catheter use. It can result in metastatic infection and even lead to death of the patient. Prophylaxis is important to decrease the risk of infection. The use of an antibiotic ointment at the exit site until it has healed and the long-term use of a dressing to cover the exit site are effective in decreasing the incidence of exit-site infection. With optimal catheter-use management, it should be possible to reduce the incidence of catheter-related bacteremia (CRB) to a level in the range of 1/1000 catheter days. Antibiotic and antimicrobial locking solutions show promise and may, if verified in appropriate clinical studies, prove to be important adjuncts to the management of catheter-dependent patients. Aspirin has been shown to have anti-staphylococcal activity and warrants further clinical evaluation. The diagnosis of CRB is based upon positive blood cultures in association with typical clinical features. If a simple routine blood culture is positive, along with a high clinical probability based upon the patient's signs and symptoms, the sensitivity and specificity of the diagnosis is greater than 75%. CRB is in reality a biofilm infection and must be treated as such. Treatment needs to focus on appropriate systemic antibiotics which should be continued for a minimum of 3 weeks and catheter management to remove the biofilm. Catheter exchange has been shown to be effective and should be performed based upon the clinical presentation of the patient. While treatment with a combination of systemic antibiotics and antibiotic locking solution may be effective for gram-negative infections, this approach does not appear to be a good choice for Staphylococcus aureus CRB.

The classification of procedure-related complications--a fresh approach.

As with any type of medical procedure, endovascular procedures result in procedure-related complications (PRCs). A PRC system as part of an outcome-based practice monitoring strategy is essential. Such a program should have several features. It should be realistic, it should be standardized, it should have credibility, it must allow for comparisons with other physicians who are performing the same procedure, and it should be easily accomplished. Currently the only system in popular use is the system designed by the Society of Interventional Radiology (SIR). Definitions within this system are excessively broad and somewhat difficult to apply. This leads to inconsistencies. SIR indicates that their system is intended for use in publications of clinical research and may not be appropriate for use in routine clinical practice. There is a need for a system specifically aimed at and designed for day to day use by the practicing interventionalist whose work is not necessarily directed toward publication. We have described a system from the clinical applications viewpoint.