Gender Disparities in Vascular Access Surgical Outcomes in Elderly Hemodialysis Patients

Fibroblast growth factor 21 predicts arteriovenous fistula functional patency loss and mortality in patients undergoing maintenance hemodialysis

BACKGROUND

Arteriovenous fistula (AVF) dysfunction is a common complication in patients undergoing maintenance hemodialysis (MHD). Elevated serum levels of fibroblast growth factor 21 (FGF21) are associated with atherosclerosis and cardiovascular mortality. However, its association with vascular access outcomes remains elusive. The present study evaluated the relationship of serum FGF21 levels with AVF dysfunction and all-cause mortality in patients undergoing MHD.

METHODS

We included patients undergoing MHD using AVF from January 2018 to December 2019. FGF21 concentration was detected using enzyme-linked immunosorbent assay. Patients were followed up to record two clinical outcomes, AVF functional patency loss and all-cause mortality. The follow-up period ended on April 30, 2022.

RESULTS

Among 147 patients, the mean age was 58.49 ± 14.41 years, and the median serum level of FGF21 was 150.15 (70.57-318.01) pg/mL. During the median follow-up period of 40.83 months, the serum level of FGF21 was an independent risk factor for AVF functional patency loss (per 1 pg/mL increase, HR 1.002 [95% CI: 1.001-1.003, p = 0.003]). Patients with higher serum levels of FGF21 were more likely to suffer from all-cause mortality (per 1 pg/mL increase, HR 1.002 [95% CI: 1.000-1.003, p = 0.014]). The optimal cutoffs for FGF21 to predict AVF functional patency loss and all-cause mortality in patients undergoing MHD were 149.98 pg/mL and 146.43 pg/mL, with AUCs of 0.701 (95% CI: 0.606-0.796, p < 0.001) and 0.677 (95% CI: 0.595-0.752, p = 0.002), respectively.

CONCLUSIONS

Serum FGF21 levels were an independent risk factor and predictor for AVF functional patency loss and all-cause mortality in patients undergoing MHD.

Temporal trends in hemodialysis access creation during the fistula first era

OBJECTIVE

Although forearm arteriovenous fistulas (AVFs) are the preferred initial vascular access for hemodialysis based on national guidelines, there are no population-level studies evaluating trends in creation of forearm vs upper arm AVFs and arteriovenous grafts (AVGs). The purpose of this study was to report temporal trends in first-time permanent hemodialysis access type, and to assess the effect of national initiatives on rates of AVF placement.

METHODS

Retrospective cross-sectional study (2012-2022) utilizing the Vascular Quality Initiative database. All patients older than 18 years with creation of first-time upper extremity surgical hemodialysis access were included. Anatomic location of the AVF or AVG (forearm vs upper arm) was defined based on inflow artery, outflow vein, and presumed cannulation zone. Primary analysis examined temporal trends in rates of forearm vs upper arm AVFs and AVGs using time series analyses (modified Mann-Kendall test). Subgroup analyses examined rates of access configuration stratified by age, sex, race, dialysis, and socioeconomic status. Interrupted time series analysis was performed to assess the effect of the 2015 Fistula First Catheter Last initiative on rates of AVFs.

RESULTS

Of the 52,170 accesses, 57.9% were upper arm AVFs, 25.2% were forearm AVFs, 15.4% were upper arm AVGs, and 1.5% were forearm AVGs. From 2012 to 2022, there was no significant change in overall rates of forearm or upper arm AVFs. There was a numerical increase in upper arm AVGs (13.9 to 18.2 per 100; P = .09), whereas forearm AVGs significantly declined (1.8 to 0.7 per 100; P = .02). In subgroup analyses, we observed a decrease in forearm AVFs among men (33.1 to 28.7 per 100; P = .04) and disadvantaged (Area Deprivation Index percentile ≥50) patients (29.0 to 20.7 per 100; P = .04), whereas female (17.2 to 23.1 per 100; P = .03), Black (15.6 to 24.5 per 100; P < .01), elderly (age ≥80 years) (18.7 to 32.5 per 100; P < .01), and disadvantaged (13.6 to 20.5 per 100; P < .01) patients had a significant increase in upper arm AVGs. The Fistula First Catheter Last initiative had no effect on the rate of AVF placement (83.2 to 83.7 per 100; P=.37).

CONCLUSIONS

Despite national initiatives to promote autogenous vascular access, the rates of first-time AVFs have remained relatively constant, with forearm AVFs only representing one-quarter of all permanent surgical accesses. Furthermore, elderly, Black, female, and disadvantaged patients saw an increase in upper arm AVGs. Further efforts to elucidate factors associated with forearm AVF placement, as well as potential physician, center, and regional variation is warranted.

Bioinformatics identifies predictors of arteriovenous fistula maturation

BACKGROUND

Arteriovenous fistulae (AVF) are the preferred access for hemodialysis but still have poor rates of maturation and patency limiting their clinical use. The underlying mechanisms of venous remodeling remain poorly understood, and only limited numbers of unbiased approaches have been reported.

METHODS

Biological Gene Ontology (GO) term enrichment analysis and differentially expressed genes (DEG) analysis were performed for three AVF datasets. A microRNA enrichment analysis and L1000CDS2 query were performed to identify factors predicting AVF patency.

RESULTS

The inflammatory and immune responses were activated during both early and late phases of AVF maturation, with upregulation of neutrophil and leukocyte regulation, cytokine production, and cytokine-mediated signaling. In men with failed AVF, negative regulation of myeloid-leukocyte differentiation and regulation of macrophage activation were significantly upregulated. Compared to non-diabetic patients, diabetic patients had significantly reduced immune response-related enrichment such as cell activation in immune response, regulation of immune-effector process, and positive regulation of defense response; in addition, diabetic patients showed no enrichment of the immune response-regulating signaling pathway.

CONCLUSIONS

These data show coordinated, and differential regulation of genes associated with AVF maturation, and different patterns of several pathways are associated with sex differences in AVF failure. Inflammatory and immune responses are activated during AVF maturation and diabetes may impair AVF maturation by altering these responses. These findings suggest several novel molecular targets to improve sex specific AVF maturation.

Sex disparities in hemodialysis access outcomes: A systematic review

The goal of this systematic review was to collate and summarize the current literature on hemodialysis access outcomes in females, identify differences between females and men, and provide a foundation for future research. A systematic review of the English-language literature was conducted by searching PubMed and Google Scholar for the following terms: "sex," "hemodialysis access," "arteriovenous fistula," "arteriovenous graft," and "dialysis catheter." Reference lists from the resulting articles were also evaluated to ensure that any and all relevant primary sources were identified. Studies were then screened by two independent reviewers for inclusion. Of 967 total studies, 53 ultimately met inclusion criteria. Females have lower maturation rates; have decreased rates of primary, primary-assisted, and secondary patency; require more procedures per capita to achieve maturation and to maintain fistula patency; are more likely to receive dialysis via an arteriovenous graft or central venous catheter; and require a longer time and potentially more assistive invasive interventions to achieve a mature fistula. Our findings emphasize the urgent need for further research to evaluate and address the causes of these disparities. Discussion with patients undergoing hemodialysis should include these findings to improve patient education, expectations, satisfaction, and outcomes.

Health inequities in dialysis care: A scoping review

MAIN PROBLEM

We aim to look at potential gaps in current dialysis literature on inequities and explore future research that could contribute to more equitable care.

METHODS

Following guidelines from the Joanna Briggs Institute (JBI) and the Preferred Reporting Items for Systematic reviews and Meta Analyses extension for Scoping Reviews (PRISMA-ScR), we conducted a scoping review of health inequities in dialysis. PubMed and Ovid Embase were searched in July 2022 for articles published between 2016 and 2022 that examined at least one of the following NIH defined health inequities: race/ethnicity, sex/gender, LGBTQ+ identity, underserved rural populations, education level, income, and occupation status. Frequencies of each health inequity as well as trends over time of the four most examined inequities were analyzed.

RESULTS

In our sample of 69 included studies, gaps were identified in LGBTQ+ identity and patient education. Inequities pertaining to race/ethnicity, sex/gender, underserved rural populations, and income were sufficiently reported. No trends between inequities investigated over time were identified.

CONCLUSIONS

Our scoping review examined current literature on health inequities pertaining to dialysis and found gaps concerning LGBTQ+ and patients with lower levels of education. To help fill these gaps, and possibly alleviate additional burden to these patients, we recommend cultural competency training for providers and dialysis center staff as well as community-based educational programs to improve dialysis patients' health literacy.

Gender disparities in patients with aortoiliac disease requiring open operative intervention

OBJECTIVE

Peripheral artery disease is known to affect males and females in different proportions. Disparate surgical outcomes have been quantified after endovascular aortic aneurysm repair, arteriovenous fistula creation, and treatment of critical limb ischemia. The aim of this study is to objectively quantify the sex differences in outcomes in patients undergoing open surgical intervention for aortoiliac occlusive disease.

METHODS

Patients were identified in the aortoiliac occlusive disease Vascular Quality Initiative database who underwent aorto-bifemoral bypass or aortic thromboendarterectomy as determined by Current Procedural Terminology codes between 2012 and 2019. Patients with a minimum of 1-year follow-up were included. Risk differences (RDs) by sex were calculated using a binomial regression model in 30-day and 1-year incidence of mortality and limb salvage. Additionally, incidence of surgical complications including prolonged length of stay (>10 days), reoperation, and change in renal function (>0.5 mg/dl rise from baseline), were recorded. Inverse probability weighting was used to standardize demographic and medical history characteristics. Multivariate logistic regression models were employed to conduct analyses of the before mentioned clinical outcomes, controlling for known confounders.

RESULTS

Of 16,218 eligible patients from the VQI data during the study period, 6538 (40.3%) were female. The mean age, body mass index, and race were not statistically different between sexes. Although there was no statistically significant difference detected in mortality between males and females at 30 days postoperatively, females had an increased crude 1-year mortality with an RD of 0.014 (95% confidence interval, 0.01-0.02; P value < .001. Males had a higher rate of a postoperative change in renal function with an RD of -0.02 (95% confidence interval, -0.03 to -0.01; P < .001).

CONCLUSIONS

Although there was no sex-based mortality difference at 30 days, there was a statistically significant increase in mortality in females after open aortoiliac intervention at 1 year based on our weighted model. Male patients are statistically significantly more likely to have a decline in renal function after their procedures when compared with females. Postoperative complications including prolonged hospital stay, reoperation, and wound disruption were similar among the sexes, as was limb preservation rates at 1 year. Further studies should focus on elucidating the underlying factors contributing to sex-based differences in clinical outcomes following aortoiliac interventions.

Study protocol of a randomized controlled trial of fistula vs. graft arteriovenous vascular access in older adults with end-stage kidney disease on hemodialysis: the AV access trial

BACKGROUND

Treatment of end-stage kidney disease (ESKD) with hemodialysis requires surgical creation of an arteriovenous (AV) vascular access-fistula (AVF) or graft (AVG)-to avoid (or limit) the use of a central venous catheter (CVC). AVFs have long been considered the first-line vascular access option, with AVGs as second best. Recent studies have suggested that, in older adults, AVGs may be a better strategy than AVFs. Lacking evidence from well-powered randomized clinical trials, integration of these results into clinical decision making is challenging. The main objective of the AV Access Study is to compare, between the two types of AV access, clinical outcomes that are important to patients, physicians, and policy makers.

METHODS

This is a prospective, multicenter, randomized controlled trial in adults ≥ 60 years old receiving chronic hemodialysis via a CVC. Eligible participants must have co-existing cardiovascular disease, peripheral arterial disease, and/or diabetes mellitus; and vascular anatomy suitable for placement of either type of AV access. Participants are randomized, in a 1:1 ratio, to a strategy of AVG or AVF creation. An estimated 262 participants will be recruited across 7 healthcare systems, with average follow-up of 2 years. Questionnaires will be administered at baseline and semi-annually. The primary outcome is the rate of CVC-free days per 100 patient-days. The primary safety outcome is the cumulative incidence of vascular access (CVC or AV access)-related severe infections-defined as access infections that lead to hospitalization or death. Secondary outcomes include access-related healthcare costs and patients' experiences with vascular access care between the two treatment groups.

DISCUSSION

In the absence of studies using robust and unbiased research methodology to address vascular access care for hemodialysis patients, clinical decisions are limited to inferences from observational studies. The goal of the AV Access Study is to generate evidence to optimize vascular access care, based on objective, age-specific criteria, while incorporating goals of care and patient preference for vascular access type in clinical decision-making.

TRIAL REGISTRATION

This study is being conducted in accordance with the tenets of the Helsinki Declaration, and has been approved by the central institutional review board (IRB) of Wake Forest University Health Sciences (approval number: 00069593) and local IRB of each participating clinical center; and was registered on Nov 27, 2020, at ClinicalTrials.gov (NCT04646226).

Teaching what matters: Integrating health equity education into the core surgery clerkship

BACKGROUND

Significant disparities in surgical outcomes exist. It is imperative to prepare future doctors to eliminate disparities. Our team of senior medical students developed a surgical clerkship module examining equity in prostate cancer. Student attitudes before and after a facilitated teaching session were assessed.

METHODS

A surgical equity pilot module was integrated into the core surgical clerkship starting in July 2020. This module was composed of (1) asynchronous preparatory material and (2) a synchronous interactive case discussion regarding disparities in prostate cancer. Discussion sessions were facilitated by upper-level medical students. Participants answered optional anonymous Likert-style and open-ended survey questions before and after the session. Pre- and post-responses were compared.

RESULTS

One hundred and sixteen students completed the module between July 2020 and January 2021. Pre- and post-survey response rates were 66% and 29%, respectively. At baseline, almost all students (95%) agreed knowledge of disparities would make them a better physician. However, the majority (95%) described their general knowledge of surgical disparities as "nonexistent," "poor," or "average." Most students did not have a framework for assessing causes of surgical disparities (86%) and were not aware of interventions for reducing disparities (90%). After intervention, the majority rated their knowledge of surgical disparities as "good" or "excellent" (71%; P < .001). Most students indicated they had a framework 79%; P < .001) and were aware of effective interventions (62%; P < .001).

CONCLUSION

We demonstrated a successful pilot of an equity-focused clerkship module. Student attitudes after a single session reflected significant improvement in knowledge of causes and interventions related to surgical disparities. Equity-focused teaching can be incorporated into the surgical clerkship.

Sex Differences in Inflammation During Venous Remodeling of Arteriovenous Fistulae

Vascular disorders frequently have differing clinical presentations among women and men. Sex differences exist in vascular access for hemodialysis; women have reduced rates of arteriovenous fistula (AVF) maturation as well as fistula utilization compared with men. Inflammation is increasingly implicated in both clinical studies and animal models as a potent mechanism driving AVF maturation, especially in vessel dilation and wall thickening, that allows venous remodeling to the fistula environment to support hemodialysis. Sex differences have long been recognized in arterial remodeling and diseases, with men having increased cardiovascular events compared with pre-menopausal women. Many of these arterial diseases are driven by inflammation that is similar to the inflammation during AVF maturation. Improved understanding of sex differences in inflammation during vascular remodeling may suggest sex-specific vascular therapies to improve AVF success.

Impacts of age, diabetes, gender, and access type on costs associated with vascular access among Chinese patients on hemodialysis

OBJECTIVES

Examine the impacts of age, diabetes, gender, and access type on vascular access (VA) associated costs among Chinese hemodialysis (HD) patients.

METHODS

We retrospectively included patients whose first permanent VA was created at the West China Hospital. Clinical characteristics, maturation, intervention, utilization, and exchange of every VA, as well as VA-related infection were collected. The study period for each patient was from HD initiation to the last follow-up. VA-related costs, including those for placement and intervention procedures, were calculated according to the standards set in 2019 for Chinese tertiary hospitals. Mann-Whitney U and Chi-square tests were conducted for comparisons between groups.

RESULTS

A total of 358 Chinese HD patients experienced functionally 143 arteriovenous fistula (AVF), 22 arteriovenous graft (AVG), and 439 tunneled cuffed central venous catheter (tcCVC) during a median study period of 26 (IQR 13-44) months, of which 42.5% used more than one permanent VA. The median annual VA-related cost in the groups of age >75 years and ⩽75 years, diabetes and non-diabetes, male and female, was $525 and $397 (p = 0.016), $459 and $462 (p = 0.64), $476 and $445 (p = 0.94), respectively. The median monthly costs for AVF ($18), AVG ($289), and tcCVC ($37) were significantly different.

CONCLUSION

HD patients aged >75 years had significantly higher annual VA-related costs. However, the annual VA-related costs did not differ across the diabetes groups or the gender groups. AVF was the most cost-effective permanent VA type in China, partly due to the inexpensive materials used compared to AVG or tcCVC.

Predictors of Arteriovenous Fistula Failure: A Post Hoc Analysis of the FAVOURED Study

Background

An autologous arteriovenous fistula (AVF) is the preferred hemodialysis vascular access, but successful creation is hampered by high rates of AVF failure. This study aimed to evaluate patient and surgical factors associated with AVF failure to improve vascular access selection and outcomes.

Methods

This is a post hoc analysis of all participants of FAVOURED, a multicenter, double-blind, multinational, randomized, placebo-controlled trial evaluating the effect of fish oil and/or aspirin in preventing AVF failure in patients receiving hemodialysis. The primary outcome of AVF failure was a composite of fistula thrombosis and/or abandonment and/or cannulation failure at 12 months post-AVF creation, and secondary outcomes included individual outcome components. Patient data (demographics, comorbidities, medications, and laboratory data) and surgical factors (surgical expertise, anesthetic, intraoperative heparin use) were examined using multivariable logistic regression analyses to evaluate associations with AVF failure.

Results

Of 536 participants, 253 patients (47%) experienced AVF failure during the study period. The mean age was 55±14.4 years, 64% were male, 45% were diabetic, and 4% had peripheral vascular disease. Factors associated with AVF failure included female sex (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.20 to 2.68), lower diastolic BP (OR for higher DBP, 0.85; 95% CI, 0.74 to 0.99), presence of central venous catheter (OR, 1.49; 95% CI, 1.02 to 2.20; P=0.04), and aspirin requirement (OR, 1.60; 95% CI, 1.00 to 2.56).

Conclusions

Female sex, requirement for aspirin therapy, requiring hemodialysis via a central venous catheter, and lower diastolic BP were factors associated with higher odds of AVF failure. These associations have potential implications for vascular access planning and warrant further studies.

Sex differences in the vascular access of hemodialysis patients: a cohort study

Background

We describe differences for probability of receiving a fistula attempt, achieving fistula use, remaining catheter-free and the rate of access-related procedures as a function of sex.

Methods

Prospectively collected vascular access data on incident dialysis patients from five Canadian programs using the Dialysis Measurement Analysis and Reporting System to determine differences in fistula-related outcomes between women and men. The probability of receiving a fistula attempt and the probability of fistula use were determined using binary logistic regression. Catheter and fistula procedure rates were described using Poisson regression. We studied time to fistula attempt and time to fistula use, accounting for competing risks.

Results

We included 1446 (61%) men and 929 (39%) women. Men had a lower body mass index (P < 0.001) and were more likely to have coronary artery disease (P < 0.001) and peripheral vascular disease (p < 0.001). A total of 688 (48%) men and 403 (43%) women received a fistula attempt. Women were less likely to receive a fistula attempt by 6 months {odds ratio [OR] 0.64 [95% confidence interval (CI) 0.52-0.79]} and to achieve catheter-free use of their fistula by 1 year [OR 0.38 (95% CI 0.27-0.53)]. At an average of 2.30 access procedures per person-year, there is no difference between women and men [incidence rate ratio (IRR) 0.97 (95% CI 0.87-1.07)]. Restricting to those with a fistula attempt, women received more procedures [IRR 1.16 (95% CI 1.04-1.30)] attributed to increased catheter procedures [IRR 1.50 (95% CI 1.27-1.78)]. There was no difference in fistula procedures [IRR women versus men 0.96 (95% CI 0.85-1.07)].

Conclusion

Compared with men, fewer women undergo a fistula attempt. This disparity increases after adjusting for comorbidities. Women have the same number of fistula procedures as men but are less likely to successfully use their fistula.

Arteriovenous Fistula Placement, Maturation, and Patency Loss in Older Patients Initiating Hemodialysis

RATIONALE & OBJECTIVE

The current clinical guidelines for vascular access do not have specific recommendations for older hemodialysis patients. Our study aimed to determine the association of age with arteriovenous fistula (AVF) placement, maturation, and primary and secondary patency loss among older hemodialysis recipients.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

A US national cohort of incident hemodialysis patients 67 years or older (N = 43,851) assembled from the US Renal Data System.

EXPOSURE

Age at dialysis initiation.

OUTCOMES

AVF placement, maturation, primary patency loss, and abandonment.

ANALYTICAL APPROACH

Cause-specific and subdistribution proportional hazards models were used to examine the association of age and AVF outcomes, with kidney transplantation, peritoneal dialysis, and death treated as competing events. Age cutoff was identified by restricted cubic splines. We compared crude and inverse probability-weighted cumulative incidence functions using Gray's test.

RESULTS

As compared with those aged 67-<77 years, patients 77 years or older had significantly lower probabilities of AVF placement (adjusted cause-specific HR [cHR], 0.96 [95% CI, 0.92-0.99]; adjusted subdistribution HR [sHR], 0.92 [95% CI, 0.89-0.95]; Gray's test P < 0.001) and maturation (adjusted cHR, 0.95 [95% CI, 0.91-0.99]; adjusted sHR, 0.93 [95% CI, 0.90-0.97]; P < 0.001). However, age was not associated with AVF primary (adjusted cHR, 1.05 [95% CI, 1.00-1.11]; adjusted sHR, 1.04 [95% CI, 0.99-1.09]; P = 0.09) or secondary (adjusted cHR, 1.06 [95% CI, 0.94-1.20]; adjusted sHR, 1.05 [95% CI, 0.93-1.18]; P = 0.4) patency loss.

LIMITATIONS

Reliance on administrative claims to ascertain AVF outcomes.

CONCLUSIONS

The likelihood of AVF maturation is an important consideration for vascular access planning. Age alone should not be the basis for excluding older dialysis patients from AVF creation because maintenance of fistula patency was not reduced with older age despite a modest reduction in fistula maturation.

A randomized pilot study to evaluate graft versus fistula vascular access strategy in older patients with advanced kidney disease: results of a feasibility study

BACKGROUND

Although older adults encompass almost half of patients with advanced chronic kidney disease, it remains unclear which long-term hemodialysis vascular access type, arteriovenous fistula or arteriovenous graft, is optimal with respect to effectiveness and patient satisfaction. Clinical outcomes based on the initial AV access type have not been evaluated in randomized controlled trials. This pilot study tested the feasibility of randomizing older adults with advanced kidney disease to initial arteriovenous fistula versus graft vascular access surgery.

METHODS

Patients 65 years or older with pre-dialysis chronic kidney disease or incident end-stage kidney disease and no prior arteriovenous vascular access intervention were randomized in a 1:1 ratio to undergo surgical placement of a fistula or a graft after providing informed consent. Trial feasibility was evaluated as (i) recruitment of ≥ 70% of eligible participants, (ii) ≥ 50 to 70% of participants undergo placement of index arteriovenous access within 90 to 180 days of enrollment, respectively, (iii) ≥ 80% adherence to study-related assessments, and (iv) ≥ 70% of participants who underwent index arteriovenous access placement will have a follow-up duration of ≥ 12 months after index surgery date.

RESULTS

Between September 2018 and October 2019, 81% (44/54) of eligible participants consented and were enrolled in the study; 11 had pre-dialysis chronic kidney disease, and 33 had incident or prevalent end-stage kidney disease. After randomization, 100% (21/21) assigned to arteriovenous fistula surgery and 78% (18/23) assigned to arteriovenous graft surgery underwent index arteriovenous access placement within a median (1st, 3rd quartile) of 5.0 (1.0, 14.0) days and 13.0 (5.0, 44.3) days, respectively, after referral to vascular surgery. The completion rates for study-specific assessments ranged between 40.0 and 88.6%. At median follow-up of 215.0 days, 5 participants expired, 7 completed 12 months of follow-up, and 29 are actively being followed. Assessments of grip strength, functional independence, and vascular access satisfaction were completed by > 85% of patients who reached pre-specified post-operative assessment time point.

CONCLUSIONS

Results from this study reveal it is feasible to enroll and randomize older adults with advanced kidney disease to one of two different arteriovenous vascular access placement surgeries. The study can progress with minor protocol adjustments to a multisite clinical trial.

TRIAL REGISTRATION

Clinical Trials ID, NCT03545113.

Perspectives in Individualizing Solutions for Dialysis Access

The vascular access is the lifeline for the hemodialysis patient. Previous national vascular access guidelines have emphasized placement of arteriovenous fistulas in most hemodialysis patients. However, the new Kidney Disease Outcomes Quality Initiative guidelines for vascular access, soon to be published, will focus on a patient's end-stage kidney disease "life plan" and take a patient "first" approach. One of the major themes of the new Kidney Disease Outcomes Quality Initiative guidelines is selecting the "right access, for the right patient, at the right time, for the right reason". Given the availability of new advances in biomedical technologies, techniques, and devices in the vascular access field, this shift to a more patient-centered vascular access approach presents unique opportunities to individualize the solutions and care for patients requiring a dialysis vascular access. This review article will address 3 potential areas where there is an unmet need to individualize solutions for dialysis vascular access care: (1) biological approaches to improve vascular access selection and selection of therapies, (2) vascular access care for the post-transplant patient, and (3) vascular access disparities in race, gender, and the elderly patient.

Selecting important predictors for arteriovenous fistula maturation in older hemodialysis patients by using random survival forests

BACKGROUND

Placing an arteriovenous fistula (AVF) in older hemodialysis patients at great risk of primary failure leads to prolonged dependency on central venous catheter (CVC). A model which accurately predicts AVF maturation can facilitate better clinical determination for AVF placement.

METHODS

We assembled a retrospective cohort of 14 892 patients aged 67 years and older who started hemodialysis with a CVC between 7/1/2010 and 6/30/2012 and had a subsequent, incident AVF placement from the United States Renal Data System (USRDS). We used random survival forests (RSF) with competing risks to identify important predictors for AVF maturation.

RESULTS

Approximately 49.7% patients achieved AVF maturation and 13.6% had a competing event. The median time to maturation was 4 (IQR: 3-5) months. Patient's gender had the highest variable importance (VIMP, 0.0027), followed by race, being institutionalized, days on hemodialysis without an AVF, estimated glomerular filtration rate, and body mass index with borderline importance (VIMP ≥0.0005). The out-of-bag (OOB) error rate of the RSF was 45.3% and 45.8% for AVF maturation in the training and validation data sets, respectively.

CONCLUSIONS

Predictors in USRDS data have limited ability to predict AVF maturation. Patient's gender might be considered as the most important predictor for AVF maturation.

Reduced patency in left-sided arteriovenous grafts in a porcine model

OBJECTIVE

The porcine arteriovenous graft model is commonly used to study hemodialysis vascular access failure, with most studies using a bilateral, paired-site approach in either the neck or femoral vessels. In humans, left- and right-sided central veins have different anatomy and diameters, and left-sided central vein catheters have worse outcomes. We assessed the effect of laterality on arteriovenous prosthetic graft patency and hypothesized that left-sided carotid-jugular arteriovenous prosthetic grafts have reduced patency in the porcine model.

METHODS

Arteriovenous polytetrafluoroethylene grafts were placed ipsilaterally or bilaterally in 10 Yorkshire male pigs from the common carotid artery to the internal jugular vein. Ultrasound measurements of blood flow velocities and diameters were assessed before graft placement. Animals were sacrificed at 1 week, 2 weeks, or 3 weeks. Patency was determined clinically; grafts and perianastomotic vessels were excised and analyzed with histology and immunostaining.

RESULTS

At baseline, left- and right-sided veins and arteries had similar blood flow velocities. Although internal jugular veins had similar diameters at baseline, left-sided carotid arteries had 11% smaller outer diameters (P = .0354). There were 10 left-sided and 8 right-sided polytetrafluoroethylene grafts placed; only 4 of 10 (40%) grafts were patent on the left compared with 7 of 8 (88%) grafts patent on the right (P = .04). Left-sided grafts had increased macrophages at the arterial anastomosis (P = .0007). Left-sided perianastomotic arteries had thicker walls (0.74 vs 0.60 mm; P = .0211) with increased intima-media area (1.14 vs 0.77 mm²; P = .0169) as well as a trend toward 38% smaller luminal diameter (1.6 vs 2.5 mm; P = .0668) and 20% smaller outer diameter (3.0 vs 3.7 mm; P = .0861). Left- and right-sided perianastomotic veins were similar histologically, but left-sided veins had decreased expression of phosphorylated endothelial nitric oxide synthase (P = .0032) and increased numbers of α-actin-positive smooth muscle cells (P = .0022).

CONCLUSIONS

Left-sided arteriovenous grafts are associated with reduced short-term patency compared with right-sided grafts in the Yorkshire pig preclinical model of arteriovenous prosthetic grafts. Laterality must be considered in planning and interpreting surgical preclinical models.

Long-Term Outcomes of Arteriovenous Fistulas with Unassisted versus Assisted Maturation: A Retrospective National Hemodialysis Cohort Study

BACKGROUND

About half of arteriovenous fistulas (AVFs) require one or more interventions before successful dialysis use, a process called assisted maturation. Previous research suggested that AVF abandonment and interventions to maintain patency after maturation may be more frequent with assisted maturation versus unassisted maturation.

METHODS

Using the US Renal Data System, we retrospectively compared patients with assisted versus unassisted AVF maturation for postmaturation AVF outcomes, including functional primary patency loss (requiring intervention after achieving AVF maturation), AVF abandonment, and frequency of interventions.

RESULTS

We included 7301 patients ≥67 years who initiated hemodialysis from July 2010 to June 2012 with a catheter and no prior AVF; all had an AVF created within 6 months of starting hemodialysis and used for dialysis (matured) within 6 months of creation, with 2-year postmaturation follow-up. AVFs matured without prior intervention for 56% of the patients. Assisted AVF maturation with one, two, three, or four or more prematuration interventions occurred in 23%, 12%, 5%, and 4% of patients, respectively. Patients with prematuration interventions had significantly increased risk of functional primary patency loss compared with patients who had unassisted AVF maturation, and the risk increased with the number of interventions. Although the likelihood of AVF abandonment was not higher among patients with up to three prematuration interventions compared with patients with unassisted AVF maturation, it was significantly higher among those with four or more interventions.

CONCLUSIONS

For this cohort of patients undergoing assisted AVF maturation, we observed a positive association between the number of prematuration AVF interventions and the likelihood of functional primary patency loss and frequency of postmaturation interventions.