Differences in coagulation in clotting of vascular access in hemodialysis patients

Arteriovenous graft (AVG) thrombosis is a frequent cause of graft failure. We evaluated coagulation protein concentrations, platelet function, and viscoelasticity factors in 20 hemodialysis (HD) patients with AVGs. The goal was to determine whether significant differences in protein concentrations, platelet function, and viscoelasticity factors exist among dialysis patients requiring frequent AVG declot procedures vs. those who do not. Twenty HD patients were enrolled: 10 frequent clotters (>3 declots in the previous year) and 10 were nonclotters. Patients on antiplatelets or chronic anticoagulation were excluded. Laboratories were drawn pretreatment and heparinase was added to counteract any potential heparin effect. Coagulation protein concentrations including tissue factor (TF), thrombin/antithrombin III complex (TAT), and prothrombin fragment 1 + 2 (F₁₊₂) were assayed. The time to clot onset was measured by force onset time (FOT). Platelet contractile force (PCF) measured the force produced by platelets during clot retraction, whereas clot rigidity was measured as clot elastic modulus (CEM). FOT, CEM, and PCF were measured by Hemodyne. Both groups had upregulation of the TF pathway, as TF, TAT, and F₁₊₂ levels were similarly increased over baseline levels. Hemodialysis patients with frequent AVG clotting had higher levels of both PCF and CEM compared with nonclotters. Additionally, the frequent clotters had a lower FOT relative to nonclotters, although both were considered in the normal range. Our study suggests that HD patients with recurrent AVG thrombotic events form clots with higher tensile strength compared with HD patients without recurrent graft thrombosis.     

Dialysis access venous stenosis: Treatment with balloon angioplasty 30‐second vs. 1‐minute inflation times

Percutaneous balloon angioplasty is the standard of care in the endovascular treatment of dialysis access venous stenosis. The significance of balloon inflation times in the treatment of these stenoses is not well defined. Our objective was to examine the outcomes of 30‐second vs. 1‐minute balloon inflation times on primary‐assisted patency of arteriovenous fistulae and grafts. Using a prospectively collected vascular access database, we identified a total of 75 patients referred for access dysfunction during a 5‐year period. These patients received 223 interventions (178 with 30‐second inflations and 45 with 1‐minute inflations). We compared primary‐assisted patency during the subsequent 9 months across groups defined by inflation times. Demographics and baseline characteristics were similar across groups. Immediate technical success and patency in the first 3 months were similar across groups (hazard ratio [HR] = 0.86; 95% confidence interval [CI]: 0.34–2.20). After 3 months, however, a 1‐minute inflation time was associated with greater incidence of access failure (adjusted HR [aHR] = 1.74; 95% CI: 1.09–2.79). Other predictors of access failure included age over 60 (aHR = 1.02; 95% CI: 1.01–1.04), central location of the lesion (aHR = 2.49; CI: 1.27–4.89), and three or more prior procedures (aHR 2.48; CI: 1.19–5.16). Our data suggest that shorter balloon inflation times may be associated with improved longer term access patency, although the benefit was not observed until after 3 months. Given the increasing demands of maintaining access patency in the era of the National Kidney Foundation Kidney Disease Outcomes Quality Initiative and Fistula First, the role of angioplasty times requires further study.     

Cephalic arch stenosis in patients with fistula access for hemodialysis: relationship to diabetes and thrombosis

Numerous studies have identified the fistula as the best access for hemodialysis with fewest complications. The radiocephalic fistula (RCF) is the first access of choice, but often results in poor maturation. Therefore, an increased number of brachiocephalic fistulas (BCF) have been placed. Cephalic arch stenosis (CAS) can occur in patients with fistula access. The current study was done to determine the incidence and associated comorbidities in patients with BCF or RCF who have CAS. A retrospective review of 450 hemodialysis patients in 3 outpatient hemodialysis units between July 1, 2000 and July 1, 2005 (60 months) was preformed. We reviewed demographics, medications, and indications for venograms. Interventional Radiologists reviewed the venograms for evidence of CAS. Radiology reports were screened to determine incidence of thrombosis, treatment with either angioplasty or stent placement and if a complication such as venous rupture occurred. One hundred and twenty-seven patients had fistula access with at least 1 venogram. Of these, 30 were RCF and 97 were BCF. Cephalic arch stenosis occurred in 77% of patients with BCF and in 20% of patients with RCF. Those with diabetes had a lower rate of occurrence than those without (p<0.01). Cephalic arch stenosis led to a high rate of thrombosis (p<0.01). The probability of having multiple radiology procedures was higher with CAS than without (p<0.01). Cephalic arch stenosis is an important problem in hemodialysis patients who have fistula access, and contributes to thrombosis. Diabetes was found to have a negative association with CAS for undefined reasons. Attempts to understand this relationship are important.     

Hemodialysis access at initiation in the United States, 2005 to 2007: Still "Catheter First"

Despite the broad consensus that native arteriovenous fistula is the access of choice for hemodialysis, national-level information about vascular access at dialysis initiation has been unavailable in the United States. For incident hemodialysis patients, June 2005 to October 2007 (n=220,157), vascular access type was determined from the new Centers for Medicare & Medicaid Services Medical Evidence Report (form CMS-2728). Proportions with each type at first dialysis, demographic and clinical associations of each type, and associations between initial access type and survival were assessed. The mean patient age was 63.6 years; 29.4% of patients were African American, and for 44.5%, end-stage renal disease was due to diabetes. Vascular access proportions were: fistula, 13.2% of patients; graft, 4.3%; catheter/maturing fistula, 16.0%; catheter/maturing graft, 3.3%; and catheter alone, 63.2%. Adjusted odds ratios (vs. fistula) of catheter use alone were ≥1.50 for lack of insurance (1.62 [95% confidence interval 1.62–1.68]), nephrologist care for 0 to 12 months (2.75 [2.69–2.81]), other (2.19 [2.09–2.29]), or unknown (1.53 [1.44–1.63]) cause of renal disease, institutional residence (1.51 [1.45–1.57]), and 7 of 18 end-stage renal disease networks. Over a mean follow-up of 1 year, 26.0% of the study population died. Compared with fistula, adjusted mortality hazards ratios were 1.39 (1.32–1.47) for grafts, 1.49 (1.44–1.55) for catheters/maturing fistulas, 1.74 (1.65–1.84) for catheters/maturing grafts, and 2.18 (2.11–2.26) for catheters alone. While geographic variability is pronounced, vascular access at dialysis inception is typically suboptimal; suboptimal access exhibits a graded association with mortality. Lack of timely access to specialty care appears to limit optimal access.     

The effect of in-stent restenosis on hemodialysis access patency

Endovascular stents have recently been shown to extend access patency in thrombosed and stenotic arteriovenous grafts (AVG). Concern remains over the frequency and severity of in-stent restenosis, though this has not been rigorously defined to date. The study was a retrospective analysis of hemodialysis patients referred for access dysfunction during a 2-year period. Using a prospectively collected, vascular access database, we identified 76 patients seen for follow-up angiography due to access dysfunction after stent placement. We compared the effect of in-stent restenosis vs. de novo lesions in patients with previously placed endovascular stents. Measured outcomes were primary assisted patency and frequency of in-stent and de novo lesions. Thirty-five (46.1%) patients had de novo lesions, while 41 (53.9%) had in-stent restenosis. In-stent restenosis was found to be the only factor associated with severity of luminal stenosis (β=0.35, 95% confidence interval 2.21–15.48, P=0.01). In-stent restenosis was associated with increased primary patency among AVGs (hazards ratio 3.10; 95% confidence interval 1.35–7.10; P=0.008). Primary patency of in-stent restenosis vs. de novo lesions for AVGs were respectively: 78% vs. 94% at 1 month, 56% vs. 42% at 3 months, 33% vs. 6% at 6 months. For arteriovenous fistulae, the difference in primary patency of in-stent vs. de novo lesions was not statistically significant. In-stent restenosis is associated with higher percent luminal diameter lesions, while de novo lesions rather than in-stent restenosis are associated with higher risk of AVG access failure and reduced primary patency.     

Relation between Access-Related Infection and Preinfection Serum Albumin Concentration in Patients on Chronic Hemodialysis

Background: Hemodialysis (HD) access‐related infection is a major cause of morbidity and mortality in HD patients. We tested whether hypoalbuminemia is a risk factor for HD access infection and whether mortality of HD catheter infection is affected by removal of the infected catheter. Methods: We analyzed the records of 87 patients on chronic HD who were hospitalized for HD access‐related infection. We obtained data on age, sex, preinfection serum albumin level, comorbidities, complications, infecting organism, type of infection, mode of management, and mortality. We compared preinfection serum albumin levels in 79 patients with HD access infection with the serum albumin levels of 198 control patients on chronic HD without HD access infection admitted to the hospital during the same time for other reasons. In the HD catheter infection subgroup, we compared mortalities between patients treated with catheter removal plus antibiotics as the primary mode of management and those treated initially with antibiotics alone. Results: Preadmission serum albumin level was lower in the HD access infection group (2.4 ± 0.6 g/dL) than in the control group (3.2 ± 0.6 g/dL, P < 0.0001). Logistic regression identified preadmission serum albumin level as a strong independent predictor of HD access infection. In a logistic regression model, with age, sex, HIV status, diabetes, and type of HD vascular access (excluding arterovenous fistula) as the covariates, the odds ratio of HD access infection was 9.8 (95% confidence interval [CI] 4.9–19.7) for a serum albumin level ≤ 3.0 g/dL (P < 0.0001), 10.4 (95% CI 4.97–21.6) for a serum albumin level ≤ 2.5 g/dL (P < 0.0001), and 28.0 (95% CI 5.8–135.9) for a serum albumin level ≤ 2.0 g/dL (P < 0.0001). Case mortality was 25.0% (4/16) in patients with tunneled HD catheter infection initially treated with antibiotics alone and 2.8% (2/71) in those treated with catheter removal plus antibiotics at the time of presentation (P = 0.0096). Conclusion: Hypoalbuminemia is associated with increased risk of HD access infection. Treatment of HD access infection with antibiotics alone is associated with increased risk of death.     

Stent use for hemodialysis access: What a general nephrologist needs to know

Recurrent stenosis due to neo‐intimal hyperplasia leads to loss of patency in an established hemodialysis access. The current treatment strategy to maintain patency involves percutaneous transluminal angioplasty with or without stent placement. There are several key points that an interventionalist needs to weigh before deciding to place a stent. These include appropriateness of stent placement, the long term consequences, the type of stent to be deployed, the size of stent and finally the impact on cannulation during dialysis. A general nephrologist needs to be aware of the various benefits and pitfalls of stent placement. The current review provides basic information that will educate the dialysis provider about stents and its use in treating dysfunctional hemodialysis access using commonly encountered clinical scenarios.     

Comparing frozen saphenous vein with Gore-tex in vascular access for chronic hemodialysis

Performing chronic hemodialysis in patients suffering from end‐stage renal disease needs a suitable vascular access like arteriovenous fistula in the upper limbs and bridge fistula in the upper or lower limbs, and also use of permanent and temporary catheters. The purpose of this study is to compare frozen saphenous vein versus using synthetic Gore‐tex vascular graft for A–V fistula. In the prospective randomized study, 70 patients needing for dialysis access were randomly divided into two groups. We performed the frozen saphenous vein A–V fistula in the test group and the Gore‐tex fistula in the control group. An assessment included function criteria (fistula thrill and murmur) and complications (infection and thrombosis) in planned intervals. At the end of the follow‐up period, the flow rates of all fistulas were assessed by Doppler sonography. The data were compared. Comparing the function criteria (fistula murmur and thrill) and the flow rate of the test group (frozen saphenous A–V fistula) and the control group (Gore‐tex method) showed no significant difference and also no significant difference between two groups in thrombosis. Infection rate of the Gore‐tex method was significantly high (p < 0.05). Arteriovenous fistula was an acceptable alternative in chronic hemodialysis, and frozen saphenous vein arteriovenous fistula was superior to Gore‐tex arteriovenous graft in some aspects.     

Vascular access for hemodialysis: experience of a team of nephrologists

A survey conducted by Bonucchi et al. underlined the different types of doctors placing arteriovenous fistula (AVF) for hemodialysis in the United States and Europe (in particular Italy). In fact, nephrologists definitely prevail in Italy, where almost 48.8% of nephrologists place an AVF themselves or with the help of a vascular surgeon (26.4%). In Europe, only 35% do so, whereas 89% of AVF are performed by surgeons in the United States. In 98% of the cases occurring at our center, the AVF was placed and reviewed by the nephrologists. This paper reports surgery cases related to the period between January 1983 and September 2006. Over this time, 1386 operations for placing and reviewing vascular access were conducted. Among these, 47 (3.3%) were related to a cuffed central venous catheter (CVC); 1138 (80.2%) related to a distal AVF; 201 (10.6%) related to a proximal AVF; and 51 (3.6%) related to an arteriovenous graft (AVG). In addition, 33 (2.3%) operations performed before January 1983 relating to AV Scribner shunts were included. Arteriovenous fistulas or AVGs were provided to our patients (only 2.6% of them have a CVC), and AVF rescue operations were performed in the shortest possible time with advantages for the patient and his vascular access.     

A pilot study of genetic polymorphisms and hemodialysis vascular access thrombosis

Vascular access thrombosis (VAT) remains a significant problem worldwide. This study determined the association between VAT and 7 candidate gene polymorphisms (factor V Leiden 1691G>A, factor II 20210G>A, methylenetetrahydrofolate reductase 677C>T, angiotensin converting enzyme 287 base pair (bp) insertion/deletion, transforming growth factor-β1 869T>C and 915G>C, NOS3 −786T>C and intron 4 27 bp tandem repeat, and endotoxin receptor CD14 −159C>T). This was a retrospective case-control pilot study conducted in 101 hemodialysis patients at a large tertiary-care, University health-science center. Sixty cases that experienced frequent VAT and 41 controls that had not experienced VAT in at least 3 years were evaluated for demographics and genotyping. These data were summarized, and univariable and multivariable regression models were constructed. Univariate VAT predictors included the NOS3 420 bp allele (P=0.03) and the presence of a central venous dialysis catheter (P<0.01). Aspirin use was protective against VAT (P=0.02). In the multivariate analysis, the dialysis access type remained a significant predictor of thrombosis (P<0.01), while aspirin use retained its protective status (P=0.01). Statin use was associated with the cases (P=0.02); however, the NOS3 420 bp allele failed to improve the model. These data confirm that central venous dialysis catheter access is associated with thrombosis, while aspirin use appears protective. The NOS3 420 bp allele may have an association with thrombosis; however, further epidemiologic data evaluating large dialysis registries are needed to confirm our observation.     

The use of vascular access audit and infections in home hemodialysis

Vascular access‐related infection is an important adverse event in home hemodialysis (HHD). We hypothesize that errors in self‐cannulation or manipulation of dialysis vascular access are associated with increased incidence of access‐related infection. We conducted a retrospective cohort study of all prevalent HHD patients at the University Health Network. All vascular access‐related infections were recorded from 2006 to 2013. Errors in dialysis access were ascertained by nurse‐administered vascular access checklist. Ninety‐two patients had completed at least one vascular access audit. Median HHD vintage was 2.3 (0.9–5.0) years in patients with appropriate vascular access technique and 5.8 (1.5–9.4) years in patients with erroneous vascular access technique. The overall rate of infection between patients with and without appropriate vascular access technique was similar (0.27 and 0.28 infections per year, P = 0.166). Among patients who were identified with errors in dialysis access manipulation, patients with five or more errors were associated with higher rate of access‐related infection (mean of 0.47 vs. 0.16 infection per patient‐year, P < 0.001). The use of vascular access audit is a feasible strategy, which can identify errors in vascular access technique. Patients with a longer median HHD vintage are associated with higher risk of inappropriate vascular access technique. Patients with multiple errors in vascular access technique are associated with a higher risk of dialysis access‐related infection. Prospective evaluation of the impact of vascular access audit on adverse vascular access events is warranted.     

Stenosis in hemodialysis arteriovenous fistula: evaluation and treatment

Vascular access complications are one of the main causes associated with an increase in morbidity and mortality in stage 5 chronic kidney disease patients. The arteriovenous fistula is regarded as the vascular access of choice for hemodialysis (HD) because of its superior patency and lower complication rates. Stenosis is considered the major cause of dysfunction of arteriovenous fistula. Despite the relatively low thrombosis rates of arteriovenous fistula, surveillance programs are necessary for detection of stenosis. We report a case of a HD patient who had never achieved an adequate Kt/V since the start of maintenance HD. During the investigation, abnormal findings were found on physical examination of the fistula, in addition to an alteration in intra-access pressure (IAP) measurements. A venous stenosis was diagnosed by Doppler ultrasound and then promptly treated with percutaneous transluminal angioplasty. The purpose of the discussion is to highlight the peculiarities of arteriovenous fistulae, methods of surveillance, including physical examination, IAP, recirculation, and measurements of blood flow, and the importance of the correction procedures for the stenosis.     

Our experience in using the brachial venae comitantes as a native vascular access for hemodialysis

A native arteriovenous fistula is the preferred vascular access for patients on long‐term hemodialysis. In the absence of suitable superficial veins, the deep venous system can be used. We intend to present our experience in using the brachial venae comitantes (VC) to create a native arteriovenous fistula. From January 2012 to December 2014, we utilized the brachial vena comitantes to create 12 arteriovenous fistulae. Data from these 12 subjects were analyzed retrospectively to produce this case series. The average age of our subjects was 55.6 years. Forty‐two percent of the subjects were women. Fifty percent of the subjects had diabetes mellitus and 58% had hypertension. We achieved a functional patency rate of 58% at 1 month's follow up after maturation. The brachio–brachial vena comitans fistula is a safe and plausible option in patients with no other suitable veins for a native fistula, more so in the hands of experienced surgeons. The longer time to cannulation has to be taken into consideration when creating a VC fistula. In suitable patients with end‐stage renal disease, it can delay the use of an arteriovenous graft or a tunneled central venous catheter.     

Is ionic dialysance useful for early detection of vascular access dysfunction? Six illustrative cases

Continuous ionic dialysance monitoring is a useful clinical tool to determine the dialysis dose in real time in each hemodialysis session. We followed up 49 patients for 16 months. Six patients with a Kt reduction of ≥20% in >3 consecutive hemodialysis sessions were identified. Fistulography demonstrated significant stenosis in all 6 patients. Angioplasty was performed in 5 with an excellent angiographic result and optimal Kt levels were restored. Unexplained and persistent Kt reduction in patients with stable chronic kidney disease under hemodialysis could represent, together with an accurate vascular access examination, a practical and additional indirect method for the early detection of vascular access dysfunction.     

Use of a "composite" vascular access graft in a young child on hemodialysis

Although arterio-venous fistulae (AVF) are currently considered to be the first choice of permanent vascular access for hemodialysis, there are some patients who are not candidates for fistulae and synthetic grafts provide other options. The Thoratec (Vectra) polyurethane vascular access graft is a new prosthetic graft that may be cannulated within days of insertion due to "self-sealing" properties. However, a tendency for kinking at the suture site due to the strong elasticity of this graft, leading to undesirable complications such as thrombosis, have been reported. We describe a surgical modification of the anastomosis by interposing a segment of expanded polytetrafluoroethylene graft (ePTFE, Venaflo) between the native vessels and the polyurethane graft sections in a pediatric patient. This modification may overcome the kinking complication associated with use of the polyurethane graft and the resulting thrombosis.     

Lower limb gigantism,lymphedema, and painful varicosities following a thigh vascular access graft

Prosthetic arteriovenous grafts (AVGs) are associated with greater morbidity than autogenous arteriovenous fistulas (AVFs), but their use is indicated when AVF formation is not possible. This report adds to the literature a case of lower limb gigantism, painful varicosities, and lymphedema following long‐term use of AVG in the upper thigh. The patient's past medical history included renal transplantation on the same side well before the AVG was inserted and right leg deep vein thrombosis. Suspicion of AVG thrombosis was excluded by Doppler ultrasound, which demonstrated an access flow of 1700 mL/min. A computed tomography (CT) scan of the abdomen and pelvis did not identify the cause of her symptoms. Whereas functional incompetence of the iliac vein valve might be responsible for the varicosities, the extent of hypertrophy in this case raises the suspicion of lymphatic blockage possibly secondary to groin dissection undertaken at the time of graft insertion, in addition to the previous dissection at the time of transplantation. This case highlights the need for minimal groin dissection during AVG insertion, particularly in patients with a history of previous abdominopelvic surgery.     

Clinical hemodialysis experience with percutaneous arteriovenous fistulas created using the Ellipsys® vascular access system

Introduction: The aim of this study is to report our clinical hemodialysis experience using a percutaneous arteriovenous fistula (pAVF) created with the Ellipsys® vascular access system. This pAVF device creates a permanent AVF anastomosis between the proximal radial artery (PRA) and the deep communicating vein (DCV) in the proximal forearm. Methods: The medical records of all patients with a pAVF were retrospectively reviewed. The clinical data analyzed included reliability of pAVF use, quality of dialysis, rate and success of puncture, and pAVF related complications, along with incidence of subsequent interventions. Findings: Between May 2017 and November 2018, 34 patients had a pAVF created with technical success in 33 patients (97%). Twenty‐eight out of 34 (82%) patients had successful two‐needle cannulation within 10 days to 6 weeks after pAVF creation. The mean Kt/v was 1.6 (1.2‐2) and the average recirculation was 10%. Fifteen patients (44%) needed no further access intervention. Twelve patients (35%) required an additional procedure to assist maturation of the pAVF in order to facilitate puncture. The average blood flow measured at the brachial artery, before the first cannulation, was 850 ml/min. From causes unrelated to the procedure, four patients died during the follow‐up study. Two patients required revision to a surgical AVF. None of the pAVFs developed aneurysmal degeneration steal syndrome, or high access flow related issues. Discussion: The Ellipsys® pAVF offers a safe and functional vascular access for hemodialysis. Advantages included prompt access maturation, avoidance of high flow AVFs, and a simple nonsurgical procedure with high patient satisfaction. Functional outcomes are equivalent and likely better than surgical fistulas. There appears to be less aneurysmal degeneration and need for future re‐intervention. Objective dialysis parameters indicate excellent quality of hemodialysis for the patient.     

Central Venous Catheters for Hemodialysis: How to Overcome the Problems

The use of central venous dialysis catheters is increasing in clinical practice. These devices, although relatively easy to insert, do have problems. Catheter size limits the amount of dialysis that can be delivered. Central venous hemodialysis catheters minimize cardiopulmonary recirculation, but have increased potential for access recirculation compared to native or artificial arteriovenous (AV) fistulas and grafts. Developments in catheter design and optimal positioning have improved the amount of dialysis that can be delivered. Similarly, infection rates are improving with careful attention to peri‐insertion care and the use of topical antiseptics and antibiotics. Although catheter thrombus remains a problem, the introduction of recombinant tissue plasminogen activator and mechanical dislodgement with an endoluminal brush have improved patency rates, but some patients may require long‐term warfarin therapy.