Micah R. Chan

Stent Placement Versus Angioplasty Improves Patency of Arteriovenous Grafts and Blood Flow of Arteriovenous Fistulae

BACKGROUND While endovascular stent placement is the standard of care in most percutaneous coronary and peripheral artery intervention, its role in the salvage of thrombosed and stenotic hemodialysis access remains controversial. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS We compared the effects of stent versus angioplasty on primary patency rates in the treatment of stenotic arteriovenous fistulae (AVF) and arteriovenous grafts (AVGs). Moreover, we compared access flow (Qa) and urea reduction ratio (URR) between the two groups as a metric of the effect of stent placement versus angioplasty on dialysis delivery. RESULTS Cox regression analysis revealed that the primary assisted AVG patency was significantly longer for the stent group compared with angioplasty, with a median survival of 138 versus 61 d, respectively (aHR = 0.17; 95% confidence interval, 0.07 to 0.39; P < 0.001). The primary AVG patency for stent versus angioplasty was 91% versus 80% at 30 d, 69% versus 24% at 90 d, and 25% versus 3% at 180 d, respectively. The primary assisted AVF patency did not differ significantly between the stent and angioplasty groups. In patients dialyzing via AVF, multiple regression analysis revealed that stent placement was associated with improved after intervention peak Qa, 1627.50 ml/min versus 911.00 ml/min (beta = 0.494; P = 0.008), change in Qa from before to after intervention, 643.54 ml/min versus 195.35 ml/min (beta = 0.464; P = 0.012), and change in URR from before to after intervention, 5.85% versus 0.733% (beta = 0.389; P = 0.039). CONCLUSIONS Our results suggest that stent placement is associated with improved AVG primary assisted patency and improved AVF blood flow, which may significantly impact on dialysis adequacy.

Hemodialysis central venous catheter dysfunction.

Despite aggressive efforts to increase autogenous fistula prevalence, catheters remain an essential access modality to a large percentage of the hemodialysis population. Central venous catheter dysfunction, which includes catheter‐related bacteremia and thrombotic occlusion, comprises the majority of complications which affect dialysis adequacy, patient quality of life, patient survival, and the economics of health care. This review provides a comprehensive overview of hemodialysis central venous catheter dysfunction, its epidemiology and risk factors, and avenues of prevention and treatment. Novel directions for future investigation are also addressed.

OBESITY AS A PREDICTOR OF VASCULAR ACCESS OUTCOMES: ANALYSIS OF THE USRDS DMMS WAVE II STUDY

Arteriovenous fistulae (AVF) are widely regarded as the preferred vascular access in hemodialysis patients due to their primary patency and patient survival benefits. While the obesity paradox has been associated with improved cardiovascular morbidity and all‐cause mortality in dialysis patients, its long‐term vascular access outcomes are less clear. Recent literature has suggested that obese patients may have increased early and late fistula failure. The purpose of this study was to explore the relationships between obesity and vascular access outcomes. We performed a retrospective cohort analysis using the USRDS DMMS Wave 2 data set. All incident dialysis patients as of January 1, 1996, over the age of 18, receiving only hemodialysis as mode of renal replacement therapy were eligible for inclusion. Among other variables, data collected for the DMMS Wave 2 included: type and location of vascular access, AVF maturity, vascular access revision, and failure. Logistic regression analyses were used to examine the relationships between obesity and vascular access outcomes, adjusting for important covariates. In all, 1486 hemodialysis patients were included. Using body mass index (BMI) <30 kg/m2 as reference, obesity did not emerge as a factor in predicting vascular access revisions or failures. An increased risk of AVF failure to mature was found only in the highest BMI quartile (≥35 kg/m2) (aOR 3.66 [95% CI 1.27–10.55], p = 0.017). Peripheral vascular disease was independently associated with an increased risk of AVF failure (aOR 2.78 [95% CI 1.01–7.63], p = 0.047) and arteriovenous graft (AVG) failure (aOR 1.65 [95% CI 1.03–2.64], p = 0.036). Obesity was not associated with increased AVF or AVG revision rates or failure and only associated with poorer AVF maturity at highest BMI quartile. We conclude that obesity should not preclude placement of AVF as vascular access of choice, except in the very obese where assessment should be individually based.

The Rationale, Implementation, and Effect of the Medicare CKD Education Benefit

Although it affects <1% of the US population, stage 4 chronic kidney disease (CKD) has increased in prevalence in the United States, grown 67% between the early 1990s and the first part of this decade. It is important to consider new strategies to slow or halt this increase. A frameshift in patient care delivery is underway in kidney health care in the United States with a Medicare education benefit for patients with stage 4 CKD. This Medicare benefit is a unique program that has the potential to inform patients and families about CKD and prepare them for transitions in health states and kidney health care. For the greatest value of this benefit to be realized, it is critical for the health care community to accurately gauge patient understanding of CKD and provide curricula that are comprehensible and actionable for patients. This type of benefit is patient centered, yet it will succeed only with a willingness to review its effectiveness and revise it if needed.

Recurrent Atypical Hemolytic Uremic Syndrome Associated With Factor I Mutation in a Living Related Renal Transplant Recipient

Atypical hemolytic uremic syndrome, or the nondiarrheal form of hemolytic uremic syndrome, is a rare disorder typically classified as familial or sporadic. Recent literature has suggested that approximately 50% of patients have mutations in factor H (CFH), factor I (CFI), or membrane cofactor protein (encoded by CD46). Importantly, results of renal transplantation in patients with mutations in either CFH or CFI are dismal, with recurrent disease leading to graft loss in the majority of cases. We describe an adult renal transplant recipient who developed recurrent hemolytic uremic syndrome 1 month after transplantation. Bidirectional sequencing of CFH, CFI, and CD46 confirmed that the patient was heterozygous for a novel missense mutation, a substitution of a serine reside for a tyrosine residue at amino acid 369, in CFI. This report reemphasizes the importance of screening patients with atypical hemolytic uremic syndrome for mutations in these genes before renal transplantation and shows the challenges in the management of these patients.

“Venopathy” at Work: Recasting Neointimal Hyperplasia in a New Light

Hemodialysis vascular access is a unique form of vascular anastomosis. Although it is created in a unique disease state, it has much to offer in terms of insights into venous endothelial and anastomotic biology. The development of neointimal hyperplasia (NH) has been identified as a pathologic entity, decreasing the lifespan and effectiveness of hemodialysis vascular access. Subtle hints and new data suggest a contrary idea-that NH, to some extent an expected response, if controlled properly, may play a beneficial role in the promotion of maturation to a functional access. This review attempts to recast our understanding of NH and redefine research goals for an evolving discipline that focuses on a life-sustaining connection between an artery and vein.

Tunneled Dialysis Catheters: Recent Trends and Future Directions

Despite aggressive efforts to increase autogenous fistula prevalence primarily from recommendations by the NKF and the Fistula First National Vascular Access Improvement Initiative, catheters remain an essential access modality for a large percentage of the hemodialysis population. Tunneled dialysis catheters or chronic catheters are associated with a multitude of complications including infections, stenosis, thrombosis, and increased morbidity and mortality even after adjustment for potential confounding variables. Also, given the blood flow rates of catheters, dialysis adequacy is compromised as compared with arteriovenous fistulae and arteriovenous grafts. This review endeavors to provide an update on catheter outcomes in the Fistula First and Kidney Disease Outcomes Quality Initiative era in relation to the increasing fistula prevalence and decline in graft placements. The conflicting view of whether catheters are increasing concurrently with the increase in fistula prevalence is discussed. The management of tunneled dialysis catheter-related complications is considered with a review of the most recent data. Future research strategies and innovations in catheter design are also addressed. This review provides a comprehensive update of tunneled hemodialysis catheters, their necessity and pitfalls, and novel directions for future investigation.

Initial Vascular Access Type in Patients with a Failed Renal Transplant

BACKGROUND AND OBJECTIVES Permanent hemodialysis vascular access is crucial for RRT in ESRD patients and patients with failed renal transplants, because central venous catheters are associated with greater risk of infection and mortality than arteriovenous fistulae or arteriovenous grafts. The objective of this study was to determine the types of vascular access used by patients initiating hemodialysis after a failed renal transplant. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Data from the US Renal Data System database on 16,728 patients with a failed renal transplant and 509,643 patients with native kidney failure who initiated dialysis between January 1, 2006, and September 30, 2011 were examined. RESULTS At initiation of dialysis, of patients with a failed transplant, 27.7% (n=4636) used an arteriovenous fistula, 6.9% (n=1146) used an arteriovenous graft, and 65.4% (n=10,946) used a central venous catheter. Conversely, 80.8% (n=411,997) of patients with native kidney failure initiated dialysis with a central venous catheter (P<0.001). Among patients with a failed transplant, predictors of central venous catheter use included women (adjusted odds ratio, 1.75; 95% confidence interval, 1.63 to 1.87), lack of referral to a nephrologist (odds ratio, 2.00; 95% confidence interval, 1.72 to 2.33), diabetes (odds ratio, 1.14; 95% confidence interval, 1.06 to 1.22), peripheral vascular disease (odds ratio, 1.31; 95% confidence interval, 1.16 to 1.48), and being institutionalized (odds ratio, 1.53; 95% confidence interval, 1.23 to 1.89). Factors associated with lower odds of central venous catheter use included older age (odds ratio, 0.85 per 10 years; 95% confidence interval, 0.83 to 0.87), public insurance (odds ratio, 0.74; 95% confidence interval, 0.68 to 0.80), and current employment (odds ratio, 0.87; 95% confidence interval, 0.80 to 0.95). CONCLUSIONS Central venous catheters are used in nearly two thirds of failed renal transplant patients. These patients are usually followed closely by transplant physicians before developing ESRD after a failed transplant, but the relatively low prevalence of arteriovenous fistulae/arteriovenous grafts in this group at initiation of dialysis needs to be investigated more thoroughly.

The Effect of Buttonhole Cannulation vs. Rope‐ladder Technique on Hemodialysis Access Patency

The rope‐ladder (RL) technique is the most common technique used for cannulation of arteriovenous fistulae (AVF). Buttonhole cannulation (BHC), or constant‐site technique, is recommended by the National Kidney Foundations Kidney Disease Outcome Quality Initiative (NKF/KDOQI) vascular access guidelines. We compared outcomes of primary patency, episodes of bacteremia, access blood flow (Qa), and quality of life (QoL) scores between RL and BHC patients. Using a prospectively collected, vascular access database, a total of 45 prevalent dialysis patients using BHC were compared with 38 patients using the RL technique over a median of 12 months (inter‐quartile range: 4–27 months). The two groups did not differ significantly in demographics except that diabetes was more common in those using BHC as compared to rope‐ladder (69% vs. 34%; p = 0.002). Risk factors associated with lack of primary patency were age (hazards ratio [HR] = 1.02 per decade; 95% CI: 1.00–1.03; p = 0.04) and female gender (HR = 1.92; 95% CI: 1.08–3.40; p = 0.03). Use of the buttonhole technique was not associated with improved primary patency (HR = 1.22, 95% CI: 0.65–2.28; p = 0.53). Episodes of bacteremia and mean scores from KDQOL‐36 did not differ significantly between the groups. This study demonstrates for the first time that BHC use is not associated with improved access patency.

How I do it: preferential use of the right external jugular vein for tunneled catheter placement.

We describe a case in which the right external jugular vein (REJ) was preferentially used to place a tunneled catheter, even though the left internal jugular vein (LIJ) was widely patent. The possible advantage of placing REJ catheters over LIJ is that doing so may function to preserve better the left‐sided vasculature in general, and, in particular, when future left‐sided access is planned. Contrast venography was required. While REJ is a viable option for catheter insertion, the effect of REJ vs. LIJ catheter placement on long‐term vessel patency as well as catheter function must be more rigorously defined to conclusively establish the superiority of one over the other.