Analysis: Intravascular Devices with a Higher Risk of Polymer Emboli: The Need for Particulate Generation Testing.

Hydrophilic polymer coatings on intravascular devices lower friction between the device and vasculature, thereby reducing trauma during interventional procedures. Polymer coating embolism-the detachment and downstream embolism of polymer particles-has been reported as an iatrogenic complication of coated interventional devices affecting the vasculature and various organs. The Food and Drug Administration (FDA) acknowledges this complication and continues to work with stakeholders to close gaps in performance testing and standards related to polymer coating integrity. Recent innovations within interventional technologies have led to development of new hydrophilic-coated devices with expanded indications for use. The 2018 FDA draft guidance for intravascular guidewires expands the application of particulate generation testing to most devices and recommends labeling changes to increase industry awareness. This article highlights current procedural trends where the phenomenon of polymer coating embolism may be more prevalent. It describes the mechanisms of polymer separation, reported clinical sequelae, and risk factors for relevant indications. These procedural trends and associated risk factors articulate the need for particulate testing and support the FDA's draft guidance recommendations for performance testing of applied coatings. If standardized, particulate assessments may allow characterization and comparisons of coating integrity among devices from various manufacturers, and are an important foundation for setting particulate limits. As hydrophilic coatings enable endovascular treatment for a range of patient populations, setting particulate limits or finding alternative solutions without compromise to device function may be essential. Particulate testing is relevant to physicians, regulators, and manufacturers for the purposes of product development and quality improvement of interventional devices.

Kidney outcomes in patients with liver cirrhosis and chronic kidney disease receiving an orthotopic liver transplant alone.

Kidney transplant in patients with liver cirrhosis and nondialysis chronic kidney disease (CKD) is controversial. We report 14 liver cirrhotic patients who had persistently low MDRD-6 estimated glomerular filtration rate (e-GFR) <40 mL/min/1.73 m2 for ≥3 months and underwent either liver transplant alone (LTA; n=9) or simultaneous liver-kidney transplant (SLKT; n=5). Pretransplant, patients with LTA compared with SLKT had lower serum creatinine (2.5±0.73 vs 4.6±0.52 mg/dL, P=.001), higher MDRD-6 e-GFR (21.0±7.2 vs 10.3±2.0 mL/min/1.73 m2 , P=.002), higher 24-hour urine creatinine clearance (34.2±8.8 vs 18.0±2.2 mL/min, P=.002), lower proteinuria (133.2±117.7 vs 663±268.2 mg/24 h, P=.0002), and relatively normal kidney biopsy and ultrasound findings. Post-LTA, the e-GFR (mL/min/1.73 m2 ) increased in all nine patients, with mean e-GFR at 1 month (49.8±8.4), 3 months (49.6±8.7), 6 months (49.8±8.1), 12 months (47.6±9.2), 24 months (47.9±9.1), and 36 months (45.1±7.3) significantly higher compared to pre-LTA e-GFR (P≤.005 at all time points). One patient developed end-stage renal disease 9 years post-LTA and another patient expired 7 years post-LTA. The low e-GFR alone in the absence of other markers or risk factors of CKD should not be an absolute criterion for SLKT in patients with liver cirrhosis.

Imaging and Peritoneal Dialysis Catheters.

The placement of a peritoneal dialysis (PD) catheter by interventionalists demands not only procedural skill but also an ability to decipher real-time ultrasonographic and fluoroscopic images. In this article, we discuss how imaging assists in PD placement and recognition of complications. To aid this endeavor, we have provided images and video clips that should assist interventionalists. Compared with the fluoroscopic technique, peritoneoscopic PD catheter placement provides direct visual imaging to also aid placement of the initial trocar and the peritoneal catheter.

Bowel Perforation During Peritoneal Dialysis Catheter Placement.

Interventional nephrologists and radiologists place peritoneal dialysis catheters using the percutaneous fluoroscopic technique in both the inpatient and outpatient setting. Nephrologists caring for such patients may have to diagnose and manage the complications resulting from these procedures. Abdominal pain can occur following peritoneal dialysis catheter placement when the local and systemic analgesia wears off. However, abdominal pain with hypotension is suggestive of a serious complication. Bleeding into the abdomen and perforation of the colon or bladder should be considered in the differential diagnosis. In the case reported here, the peritoneogram showed contrast in the bowel, and correct interpretation by the interventionist would have prevented this complication. The characteristic pattern of peritoneogram images in this case will guide interventionists to avoid this complication, and the discussion of the differential diagnosis and management will assist nephrologists in taking care of such patients.

Minimal Modification to the Trerotola Backbleeding Technique Increases Its Effectiveness.

Thrombectomy of a clotted upper arm access may be complicated by brachial artery embolization. A number of techniques have been described to relieve the embolization that may not always be successful. Backbleeding is one such technique. We describe a minimal modification that makes backbleeding more effective.

Complications of a High-flow Access and Its Management.

A high-flow access has been defined as one with a flow >1-1.5 l/minute or as one where the access flow is >20% of the cardiac output. Although it may be asymptomatic, it can be associated with cardiopulmonary complications, aneurysms, central vein stenosis and the distal hypoperfusion ischemic syndrome in some patients. The decision for surgical intervention should be made after careful medical optimization especially in patients with high output cardiopulmonary compromise. In this review, we present a summary of current knowledge about the pathophysiology of a high-flow fistula, followed by a concise, comprehensive synopsis of current medical and surgical therapy.

An approach to heparin and lidocaine hypersensitivity for the interventional nephrologist.

The general and interventional nephrologist may occasionally encounter a situation where the patient may state that he/she has an allergy to lidocaine or heparin. Heparin hypersensitivity is usually either a delayed type hypersensitivity reaction or an immune-mediated thrombocytopenia. While a number of alternative drugs are available, many of them are subject to local availability, food and drug administration indications, and the patient's hepatic and renal function. Many of these drugs do not have antidotes in case of bleeding. Lidocaine hypersensitivity is usually a delayed type reaction, although adverse reactions, which are much more common, are wrongly labeled as an allergy. 1% diphenhydramine and benzyl alcohol may be used as alternatives.

The structure and function of endovascular stents: a primer for the interventional nephrologist.

The use of stents has become common practice in various interventional fields. The purpose of this article is to provide the interventionalist with an understanding of the basic structure stent. We describe the etymology, the classification and describe various terms used by engineers as they strive to develop that "ideal" stent. We also describe the fabrication process briefly and finally elaborate on the characteristic "build and cut" of some commonly used stents.

Telescoping of sheaths-an easy technique to facilitate the removal of a stuck ruptured transluminal angioplasty balloon.

Balloon rupture during angioplasty is an uncommon event. The ruptured balloon usually is removed through its introducer sheath without any problems. However, there may be occasions when a ruptured balloon cannot be withdrawn from an access. We describe a simple technique that can be used to extricate a stuck ruptured angioplasty balloon.

Stent strut protrusion--an uncommon complication of stent placement in a fistula.

Stent strut protrusion through the skin is a rare and a potentially dangerous complication from the cannulation of stents placed within arterio-venous fistulas and grafts. Such cases are usually managed surgically. We present a case wherein strut penetration of an arterio-venous fistula was noted at the distal (uncovered) end of a Fluency Plus(®) tracheo bronchial stent graft. After analyzing the various reasons why this may have happened, a nonsurgical approach was taken to preserve the access and manage strut protrusion.

Polymer embolization from minimally invasive interventions.

Many of the tools used in interventional nephrology, such as glidewires and sheaths, are coated with a hydrophilic polymer to increase their lubricity; however, this polymer can shear off, which causes polymer embolization. We describe 3 cases in which polymer emboli were found on histopathologic examination in an arteriovenous graft, a transplanted kidney, and the myocardium. A review of the literature shows that although most of these phenomena are benign, in some patients, it may present with significant morbidity.

Graftula: a composite access consisting of a graft used to repair a dysfunctional hemodialysis fistula.

Nonmaturing or dysfunctional hemodialysis fistulas are often repaired with interposition grafts placed either within the fistula (fistula-to-fistula configuration), or connected to another vein (fistula-to-vein configuration). The goal of this study was to compare the survival and usefulness of the composite accesses thus created, which we call "graftulas," with upperarm grafts. This was a retrospective study wherein we determined the survival and thrombosis rates of graftulas (n=24) and upper arm grafts (n=31) placed 1/1/07 through 12/31/09 and followed through 11/30/10. Graftulas resembled grafts as most (96%) were successfully cannulated in 65 ± 43 days. Survival of graftulas was also similar to grafts (58%, 47%, and 32% vs. 56%, 47%, and 39% at 1, 2, and 3 years respectively, p=0.60). However, graftulas had a lower thrombosis rate than grafts (0.5 vs. 1.2 per patient year, p=0.04), and in the fistula-to-fistula configuration, a 2-year thrombosis-free survival of 78%. Total survival of the access site (fistula+graftula) was 92%, 73%, and 42% at 1, 3, and 5 years, respectively. Graftulas possess certain beneficial properties of fistulas and grafts that allows for continued use of the original access site.

Ischemia from extrinsic compression of the brachial artery by a stent in the venous outflow of a brachio-basilic arterio-venous graft.

Distal artery embolization is a well-known complication after mechanical thrombectomy, manifesting as limb ischemia. We describe a case of ischemia that developed after mechanical thrombectomy and stent placement in the venous anastomosis of a brachio- basilic arterio-venous graft. Subsequent investigations revealed that the stent had extrinsically compressed the adjacent brachial artery. Although balloon angioplasty of the artery initially restored flow, the patient needed surgical removal of the graft and stent to prevent persistent ischemia.

Lessons learnt and future directions in managing dialysis access during the COVID 19 pandemic: Patient and provider experience in the United States.

BACKGROUND: The COVID 19 pandemic adversely impacted delivery of preventive, routine, urgent, and essential care worldwide. Dialysis access care was particularly affected due to the lack of specific guidelines regarding procedures for its creation and maintenance. Early guidance by Centers for Medicare and Medicaid was inadvertently interpreted as guidance to stop dialysis access procedures. Prompt action by professional societies was needed to furnish detailed guidance to establish essential nature of these procedures. METHODS: The American Society of Diagnostic and Interventional Nephrology (ASDIN) issued a joint statement with Vascular Access Society of the Americas (VASA) - "Maintaining Lifelines for ESKD Patients" to clearly establish the role of vascular access as a lifeline for ESKD (End Stage Kidney Disease) patients and the importance and urgency of its timely management. ASDIN also conducted a survey in mid-2020, that was administered to the ASDIN database as well as shared with the general public via the organization's social media platforms. The respondents reported their experiences in the care of dialysis access, practice patterns and the utility of the ASDIN-VASA statement during the COVID 19 pandemic. RESULTS: Of the 2030 individual surveys sent, 581 were opened and 53 (9.1%) responses were received from different parts of the country and from different practice settings. ASDIN COVID 19 triage document was frequently utilized and 83% of respondents found the document valuable. The survey also revealed multiple obstacles, including logistical and financial issues that led to significant disruption of services. CONCLUSIONS: The care of dialysis access was significantly affected in the United States during the COVID 19 pandemic due to multiple reasons. ASDIN actions provided valuable specific guidance regarding and explored barriers to dialysis access care. We describe those results and discuss strategies to prevent COVID 19 transmission with innovative strategies of providing access care. Individualized decision making is of essence when considering dialysis access procedures.

Catheter-directed thrombolytic infusion for thrombosed arteriovenous fistulas with a large clot burden: A case series.

Arteriovenous fistula (AVF) thrombosis occurs less often when compared to arteriovenous grafts. Since the number of AVFs has increased in the United States, AVF thrombosis is seen more frequently today. AVF thrombectomy can be tedious, requires physician ingenuity, and many times results in failure. Substantial clot burden in megafistulas and aneurysms is considered a relative contraindication to endovascular thrombectomy. Usually, it results in surgical referral for open thrombectomy or, at times, abandonment of the fistula altogether. Herein, we describe the technique, results, and cautions of combining a continuous infusion of recombinant tissue plasminogen (rTPA) followed by angioplasty of the culprit stenotic lesion that was successful in opening five of six AVFs with a substantial clot burden.

Uncommon complications of long-term hemodialysis catheters: adhesion, migration, and perforation by the catheter tip.

Use of long-term dialysis catheters (e.g., tunneled dialysis catheters) predisposes patients to complications. While catheter-related bacteremia is one of the commonest encountered complication, there are a series of rare complications, namely catheter adherence to the vessel wall, catheter fracture, and vessel perforation, that can occur. This article attempts to discuss such complications with emphasis on potential risk factors, clinical presentations, and management options.

Going Home: Access for Home Modalities.

The cost and health burden of ESRD continues to increase globally. Total Medicare expenditure on dialysis has increased from 229 million USD in 1973 to 35.4 billion USD in 2016. Dialysis access can represent almost a tenth of these costs. Central venous catheters have been recognized as a significant factor driving costs and mortality in this population. Home dialysis, which includes peritoneal dialysis and home hemodialysis, is an effective way of reducing costs related to renal replacement therapy, reducing central venous catheter usage and in many cases improving the clinical and psychosocial aspects of patients' health. Addressing access-related issues for peritoneal dialysis, urgent-start peritoneal dialysis and home hemodialysis can have impact on the success of home dialysis. This article reviews issues related to dialysis access for home therapies.

Role of stents in hemodialysis vascular access.

Stents are ubiquitously utilized in coronary and peripheral arterial disease. Interventional nephrologists, however, place stents in the venous outflow of the arteriovenous access. Stenosis is the predominant pathology that causes access dysfunction and will ultimately lead to thrombosis if uncorrected. Angioplasty and stent deployment are the current techniques available to combat stenosis. From initial bare metal stainless steel stents, the current generations of stents used are predominately covered nitinol stents. The latest randomized control trials reveal that stents decrease the number of interventions required to maintain patency but do not improve the overall access survival. Furthermore, bare metal stents have been shown to be inferior to stent grafts. This review discusses indications for stent deployment in the hemodialysis access, the current evidence for their use, and briefly touches on their complications.

Iron chelators reduce chromosomal breaks in ataxia-telangiectasia cells.

Ataxia-telangiectasia (A-T) is characterized by ataxia, genomic instability, and increased cancer incidence. Previously, iron chelator concentrations which suppressed normal cell colony formation increased A-T cell colony formation. Similarly, iron chelators preferentially increased A-T cell colony formation following peroxide exposure compared to normal cells. Last, A-T cells exhibited increased short-term sensitivity to labile iron exposure compared to normal cells, an event corrected by recombinant ATM (rATM) expression. Since chromosomal damage is important in A-T pathology and iron chelators exert beneficial effects on A-T cells, we hypothesized that iron chelators would reduce A-T cell chromosomal breaks. We treated A-T, normal, and A-T cells expressing rATM with labile iron, iron chelators, antioxidants, and t-butyl hydroperoxide, and examined chromosomal breaks and ATM activation. Additionally, the effect of ATM-deficiency on transferrin receptor (TfR) expression and TfR activity blockage in A-T and syngeneic A-T cells expressing rATM was examined. We report that (1) iron chelators and iron-free media reduce spontaneous and t-butyl hydroperoxide-induced chromosomal breaks in A-T, but not normal, or A-T cells expressing rATM; (2) labile iron exposure induces A-T cell chromosomal breaks, an event lessened with rATM expression; (3) desferal, labile iron, and copper activate ATM; (4) A-T cell TfR expression is lowered with rATM expression and (5) blocking TfR activity with anti-TfR antibodies increases A-T cell colony formation, while lowering chromosomal breaks. ATM therefore functions in iron responses and the maintenance of genomic stability following labile iron exposure.

Vascular Access Guidelines: Summary, Rationale, and Controversies.

Dialysis vascular access management in the United States changed significantly after National Kidney Foundation-Kidney Disease Outcome Quality Initiative (NKF-KDOQI) clinical practice guidelines were first published in 1997. The Centers for Medicare and Medicaid Service adopted these guidelines and in collaboration with the End-Stage Renal Disease Networks established the Fistula First Breakthrough Initiative (FFBI) in 2003 to improve the rate of arteriovenous fistula use over arteriovenous graft and central venous catheter in the dialysis population. The implementation of guidelines and FFBI has led to a significant increase in the arteriovenous fistula use in the prevalent dialysis population. The guidelines are criticized for being opinion based and often impractical. Over the past 2 decades, the patient population undergoing dialysis has become older with complex comorbidities and challenges for creating an ideal vascular access. Advancing knowledge about access pathophysiology, improved treatment options, and improved process of care with team approach model point toward diminishing relevance of few of the existing guidelines. Moreover, several guidelines remain controversial and may be leading to clinical decisions that may be unfavorable to the patients. The review discusses the historical aspect of vascular access care in the United States and evolution of current practice standards and controversies surrounding few of these guidelines in the current time.