Predictors of sustained arteriovenous access use for haemodialysis

Risk score for the prediction of arteriovenous fistula maturation

OBJECTIVE

The poor maturation rate of arteriovenous fistulas (AVFs) remains a challenge. We aim to develop a parsimonious risk score equations that incorporate patients' demographics, comorbidities, and vessel characteristics to assist the access surgeons in predicting the likelihood of AVF maturation before surgery.

METHODS

Data of AVFs created from 2015 to 2020 in National University Hospital Singapore was retrospectively obtained and used as the training dataset. Two prediction models were developed to predict: (1) the commencement of cannulation; and (2) functional maturation, by 3 months after creation. The models were internally validated using k-fold cross validation and externally validated on patients who had AVFs created in 2021 and 2022. The final models were converted to interpretable risk score equations for clinical usage.

RESULTS

The training dataset included 474 AVF cases. Six and eight variables were selected for predicting: (1) the commencement of cannulation; and (2) functional maturation, respectively. The two models demonstrated satisfactory performance with C-statistics of 0.72 and 0.74, respectively. The C-statistics in internal validation were 0.7 and 0.69 for the two models, respectively. External validation was performed using the data of 220 different patients; the C-statistic was 0.7 in both models.

CONCLUSIONS

The two risk scores developed demonstrated reasonable preoperative predicative values for AVF maturation. They are potentially useful in aiding clinicians to make decisions about AVF creation sites. Further evaluation of these prediction scores in a large cohort is required to reveal their clinical value.

Standardization of Pre-operative Evaluation to Improve the Outcome of Arteriovenous Fistula for Vascular Access of Hemodialysis: A Review of 700 Cases

Background With the advent of COVID-19, mortality rates of end-stage kidney disease (ESKD) rose by 37% which makes its treatment an important part of healthcare. Arteriovenous fistula (AVF) is linked to higher patient survival rates. Cimino-Brescia fistula is the most effective vascular access technique, but it has a high rate of primary failure (PF) and a several-week maturation period before it can be used. The current study aims to verify the preoperative evaluation in improving survival among AVF patients. Methodology The current study is a retrospective analysis of the hospital database from Jan 2022 to July 2023, with patients of a mean age of 60.2 years. The sample size was around 700, including the patients indicated for long-term hemodialysis (HD) with an estimated GFR of less than 20 mm/min/1.73m². Following AVF surgery, post-operative outcomes, PF, and maturation time were considered. Results Among the 757 AVF procedures, 588 (82%) were new cases, and 112 (16%) had prior AVF history on the same side. PF was observed in 126 (18%) AVFs, while 574 (84%) achieved maturation. Age at surgery did not correlate with PF. Male sex and brachiocephalic AVF (BCAVF) had lower PF rates, while female gender, non-BCAVF, and vascular chronic kidney disease (CKD) were independent predictors. Proximal fistulas had a higher failure risk (32%). During surgery, the PF occurred six times more frequently in patients with veins and arteries under 2 mm and without a bruit. Conclusion AVF maturation aims to achieve a functional AVF for easy dialysis, requiring meticulous vein selection, doppler vascular mapping, and a standardized process to reduce PF rates. Factors determining PF include thrill and bruit, flow rates, and comorbidities. These findings can help clinicians make informed decisions and improve outcomes for patients undergoing fistula surgery.

Arteriovenous Fistula Formation with Adjuvant Endovascular Maturation

INTRODUCTION

The clinical utility of the native arteriovenous fistula (AVF) is limited by a prolonged time to maturation, low overall maturation rate, and subsequent abandonment. Endovascular intervention is increasingly accepted as first line therapy to treat AVF stenosis. The objective of this study was to evaluate AVF formation outcomes when early endovascular intervention was selectively performed to bring about timely AVF maturation.

METHODS

A retrospective study (February 2014- February 2020) was performed on 82 AVF consecutive patients (mean age 62.5±13.5 (17-83); 58 male (70.7%)) with end-stage renal failure who had Vascular Access (VA) construction at a single institution. Four year AVF patency, vascular diameters, haemodialysis parameters, re-intervention rate, and mortality were analysed.

RESULTS

Radiocephalic AVF was the most common fistula constructed (71 patients; 88.6%). Post formation evaluation (46.2+/-56.0 days (5-343)) revealed 33 (40.2%) immature AVFs. Subsequently, 19 patients underwent endovascular procedures consisting of angioplasty/stenting of the juxta-anastomosis, cannulation and/or outflow segments to bring about timely maturation of the AVF. Hence 93.9% of AVFs had reached functional patency (maturation) by 6 months post formation, with a mean time to maturation of 67.8 +/- 65.9 (5-320) days. After reaching maturation, Primary Access Functional Patency was 82 +/- 4.3 % at 6 months, 58+/- 5.5% at 12 months and 34 +/- 6.8% at 48 months. Primary Assisted Access Functional Patency was 95 +/- 2.4% at 6 months, 90 +/-3.3 % at 12 months and 83 % +/- 4.7 % at 48 months. 121 endovascular interventions were performed to maintain patency, equating to an endovascular reintervention rate of .37 procedures/patient year. Mean arterial, venous and brachial flow rates did not change significantly after maturation with a mean fistula (primary assisted functional patency) survival time of 5.9 +/- 0.26 (5.33- 6.36) years from maturation. Only 12 thromboses occurred after the first post formation follow up review, which were all salvaged using endovascular techniques leading to 100% Total secondary functional patency at 4 years. 5 year estimated all-cause mortality was 45.6 +/-12.7%.

CONCLUSION

Arteriovenous fistula maturation rate and time to maturation can be improved when early endovascular intervention is selectively performed post formation. This allows for near universal maturation where, once matured, the use of ongoing endovascular re-intervention allows for a low re-intervention rate and long term patency providing for reliable long term renal vascular access.

Association of Proteinuria with Central Venous Catheter Use at Initial Hemodialysis

CONTEXT

Central venous catheter (CVC) use is associated with increased mortality and complications in hemodialysis recipients. Although prevalent CVC use has decreased, incident use remains high.

OBJECTIVE

To examine characteristics associated with CVC use at initial dialysis, specifically looking at proteinuria as a predictor of interest.

DESIGN

Retrospective cohort of 918 hemodialysis recipients from Kaiser Permanente Northwest who started hemodialysis from January 1, 2004, to January 1, 2014.

MAIN OUTCOME MEASURES

Multivariable logistic regression was used to examine an association of proteinuria with the primary outcome of CVC use.

RESULTS

More than one-third (36%) of patients in our cohort started hemodialysis with an arteriovenous fistula, and 64% started with a CVC. Proteinuria was associated with starting hemodialysis with a CVC (likelihood ratio test, p < 0.001) after adjustment for age, peripheral vascular disease, congestive heart failure, diabetes, sex, race, and length of predialysis care. However, on pairwise comparison, only patients with midgrade proteinuria (0.5-3.5 g) had lower odds of starting hemodialysis with a CVC (odds ratio = 0.39, 95% confidence interval = 0.24-0.65).

CONCLUSION

Proteinuria was associated with use of CVC at initial hemodialysis. However, a graded association did not exist, and only patients with midgrade proteinuria had significantly lower odds of CVC use. Our findings suggest that proteinuria is an explanatory finding for CVC use but may not have pragmatic value for decision making. Patients with lower levels of proteinuria may have a higher risk of starting dialysis with a CVC.

Arteriovenous Fistulae for Haemodialysis: A Systematic Review and Meta-analysis of Efficacy and Safety Outcomes

BACKGROUND

Arteriovenous fistulae are the currently recommended gold standard vascular access modality for haemodialysis because of their prolonged patency, improved durability, and low risk of infection for those that mature. However, notable disadvantages are observed in terms of protracted maturation time, associated high rates of catheter use, and substantial abandonment rates. The aim of this study was to quantitatively summarize the outcomes of fistula patency, infection, maturation, and abandonment published in the scientific literature.

METHODS

This was a systematic review and meta-analyses of studies evaluating fistula outcomes. Literature searches were conducted in multiple databases to identify observational and interventional studies of mean fistula patency rates at 1 year, infection risk, maturation time, and abandonment. Digitisation software was used to simulate individual patient level data from Kaplan-Meier survival plots.

RESULTS

Over 8000 studies were reviewed, and from these, 318 studies were included comprising 62,712 accesses. For fistulas the primary unassisted, primary assisted, and secondary patency rates at one year were 64%, 73% and 79% respectively, however not all fistulas reported as patent could be confirmed as being clinically useful for dialysis (i.e. functional patency). For fistulas that were reported as mature, mean time to maturation was 3.5 months, however only 26% of created fistulas were reported as mature at 6 months and 21% of fistulas were abandoned without use. Overall risk of infection in fistula patients was 4.1% and the overall rate per 100 access days was 0.018.

CONCLUSIONS

Reported fistula patency rates may overstate their potential clinical utility when time to maturation, maturation rate, abandonment and infection are considered. Protracted maturation times, abandonment and infection all have a significant impact on evaluating the clinical utility of fistula creation. A rigorous and consistent set of outcomes definitions for hemodialysis access are necessary to clarify factors contributing to fistula success and the clinical consequence of fistula failure.

Investigating clinical predictors of arteriovenous fistula functional patency in a European cohort

BACKGROUND

Arteriovenous fistula (AVF) failure to mature (FTM) rates contribute to excessive dependence on central venous catheters for haemodialysis. Choosing the most appropriate vascular access site for an individual patient is guided largely by their age, co-morbidities and clinical examination. We investigated the clinical predictors of AVF FTM in a European cohort of patients and applied an existing clinical risk prediction model for AVF FTM to this population.

METHODS

A prospective cohort study was designed that included all patients undergoing AVF creation between January 2009 and December 2014 in a single centre (Belfast City Hospital) who had a functional AVF outcome observed by March 2015.

RESULTS

A total of 525 patients had a functional AVF outcome recorded and were included in the FTM analysis. In this cohort, 309 (59%) patients achieved functional AVF patency and 216 (41%) patients had FTM. Female gender [P < 0.001, odds ratio (OR) 2.03 (CI 1.37-3.02)] and lower-arm AVF [P < 0.001, OR 4.07 (CI 2.77-5.92)] were associated with AVF FTM. The Lok model did not predict FTM outcomes based on the associated risk stratification in our population.

CONCLUSIONS

In this European study, female gender was associated with twice the risk of AVF FTM and a lower-arm AVF with four times the risk of FTM. The FTM risk prediction model was not found to be discriminative in this population. Clinical risk factors for AVF FTM vary between populations; we would recommend that units investigate their own clinical predictors of FTM to maximize AVF functional patency and ultimately survival in dialysis patients. Clinical predictors of AVF FTM may not be sufficient on their own to improve vascular access functional patency rates.

Predictive parameters of arteriovenous fistula functional maturation in a population of patients with end-stage renal disease

INTRODUCTION

With increasing numbers of patients diagnosed with ESRD, arteriovenous fistula (AVF) maturation has become a major factor in improving both dialysis related outcomes and quality of life of those patients. Compared to other types of access it has been established that a functional AVF access is the least likely to be associated with thrombosis, infection, hospital admissions, secondary interventions to maintain patency and death.

AIM

Study of demographic factors implicated in the functional maturation of arteriovenous fistulas. Also, to explore any possible association between preoperative haematological investigations and functional maturation.

METHODS

We performed a retrospective chart review of all patients with ESRD who were referred to the vascular service in the University Hospital of Limerick for creation of vascular access for HD. We included patients with primary AVFs; and excluded those who underwent secondary procedures.

RESULTS

Overall AVF functional maturation rate in our study was 53.7% (52/97). Female gender showed significant association with nonmaturation (P = 0.004) and was the only predictor for non-maturation in a logistic regression model (P = 0.011). Patients who had history of renal transplant (P = 0.036), had relatively lower haemoglobin levels (P = 0.01) and were on calcium channel blockers (P = 0.001) showed better functional maturation rates.

CONCLUSION

Female gender was found to be associated with functional non-maturation, while a history kidney transplant, calcium channel-blocker agents and low haemoglobin levels were all associated with successful functional maturation. In view of the conflicting evidence in the literature, large prospective multi-centre registry-based studies with well-defined outcomes are needed.