Post-operative arterio-venous fistula blood flow influences primary and secondary patency following access surgery

Surgical and endovascular assisted maturation procedures improve cannulation after arteriovenous fistula creation, but not after arteriovenous graft placement

OBJECTIVE

After creation, arteriovenous fistulae (AVF) and arteriovenous grafts (AVG) can undergo surgical or endovascular assisted maturation (AM) procedures to enable use for hemodialysis. We sought to explore the association of interventions with successful two-needle cannulation (TNC) using the United States Renal Data System (USRDS).

METHODS

Using the 2012-2017 USRDS, we identified patients initiating hemodialysis with tunneled dialysis catheters (TDC). Successful AVF/G use was defined as two-needle cannulation (TNC). Our principal outcome was time to first TNC after AVF/G creation. Death and new access placement were competing events that precluded TNC. Competing-risks regression models were constructed to identify factors associated with cannulation. Logistic regression was used to assess the association between AM procedures and 1-year TNC and also to compare post-cannulation outcomes.

RESULTS

Among 81,143 patients, 15,880 (19.6%) had AVG and 65,263 (80.4%) had AVF. AVG patients were more likely than AVF patients to achieve TNC at 1 year on unadjusted (77.4% vs 64.0%, p < 0.001) and on multivariate analysis (sHR = 2.56 (2.49-2.63), p < 0.001). For AVFs, one AM surgical procedure was associated with improved 1-year TNC rates, but further revisions were not helpful. Endovascular AM procedures were associated with increased AVF TNC rates. Any procedure, surgical or endovascular, was detrimental to achieving TNC for AVGs.Following initial TNC, those accesses that needed AM procedures were associated with higher rates of access failure (AVF: OR = 1.32 (1.21-1.45); AVG: OR = 1.77 (1.500-2.00); p < 0.001), catheter replacement (AVF: OR = 1.27 (1.20-1.34); AVG: OR = 1.56 (1.42-1.71), p < 0.001), and additional endovascular procedures (AVF: 0.75 ± 1.22 no AM vs 1.33 ± 1.62 any AM; AVG: 1.31 ± 1.77 no AM vs 1.96 ± 2.22 any AM; all p < 0.001).

CONCLUSIONS

AVG achieved TNC after creation more reliably than AVF. A single surgery or endovascular procedures for AVFs is associated with greater rates of TNC. For AVGs, any AM procedure is associated with lower cannulation rates, and reinforces the need for careful operative technique.

The feasibility of small-caliber veins for autogenous arteriovenous fistula creation: A single-center retrospective study

Objective

Autogenous arteriovenous fistula (AVF) is recommended as the first choice for hemodialysis vascular access. A small-caliber vein is one of the independent risk factors for AVF maturation and patency. However, the specific threshold is still unclear, making it difficult to accurately determine whether these vessels are suitable for AVF creation.

Design

This is a single-center retrospective study.

Method

Patients who underwent AVF creation in our medical center between January 2020 and September 2022 and satisfied the eligibility criteria were included in this retrospective study. Logistic regression analysis was performed to identify risk factors for functional maturation and additional intervention. The optimal cutoff value was determined based on the receiver operating curve (ROC) and the Youden index. Kaplan-Meier analysis was utilized in further patency rate comparisons.

Result

A total of 125 forearm AVFs were created in 121 patients with end-stage renal disease (ESRD). The mean age was 53.88 ± 15.10  years. Preoperative vascular Doppler ultrasound (DUS) was conducted and recorded in 106 cases (84.80%). The mean targeted artery and vein diameters were 2.17 ± 0.54 and 1.71 ± 0.75  mm, respectively. Small-caliber vein is the risk factor for functional maturation failure (OR = 0.256, 95%CI [0.06-0.75], p = 0.033) and additional intervention (OR = 0.306, 95% CI [0.09-0.78], p = 0.031). The optimal cutoff value is 1.35  mm (augmented) when specificity and sensitivity reach 80 and 63.7%, respectively. The AVFs with a vein diameter of more than 1.35 mm (augmented) showed higher patency rates (p < 0.01).

Conclusion

After comprehensive DUS evaluation, intraoperative hydrodilation, postoperative active exercise and intensive DUS detection, and application of balloon-assisted maturation, if necessary, using a vein more than 1.35 mm (augmented), could achieve satisfactory functional maturation and postoperative patency in AVF formation.

O volume de fluxo e a velocidade de pico sistólico ao ultrassom vascular com Doppler intraoperatório como preditores de perviedade precoce na fístula arteriovenosa autógena para hemodiálise

Background

Chronic kidney disease is a major public health problem. Hemodialysis is the most common renal replacement therapy. Arteriovenous fistulas (AVF) are a possible access option, but early failure rates remain high.

Objectives

to investigate the value of intraoperative vascular Doppler ultrasound for predicting early AVF patency.

Methods

Prospective observational study. Consecutive patients undergoing AVF were assessed with vascular Doppler ultrasonography intraoperatively and on days 1, 7, 30, and 60. Patients were divided into groups according to presence or absence of primary and secondary patency. Blood flow (BF) and peak systolic velocity (PSV) were compared. ROC curves were plotted and used to define the PSV and BF values that yielded greatest sensitivity (Sens) and specificity (Spec).

Results

47 patients met the inclusion criteria and were analyzed. Higher intraoperative PSV and BF values were observed in patients who had primary and secondary patency than in patients with access failure. The values with greatest sensitivity and specificity for predicting 30-day primary patency were 106 cm/s for venous PSV (Sens: 75% and Spec: 71.4%) and 290.5 ml/min for arterial blood flow (Sens: 80.6% and Spec 85.7%). Values for 30-day secondary patency were 106 cm/s for arterial PSV (Sens: 72.7%, Spec: 100%) and 230 ml/min for venous blood flow (Sens: 86.4%, Spec100%). Values for 60-day primary patency were 106 cm/s for venous PSV (Sens: 74.4%, Spec: 62.5%) and 290.5 ml/min for arterial blood flow (Sens: 80%, Spec: 75%).

Conclusions

Peak systolic velocity and blood flow measured using intraoperative vascular Doppler ultrasound can predict early patency of hemodialysis arteriovenous fistulas.

Blood flow quantification in dialysis access using digital subtraction angiography: A retrospective study

BACKGROUND AND OBJECTIVE

Vascular access is the "lifeline" of end-stage renal disease patients, which is surgically constructed to remove blood-waste and return artificially filtered blood into circulation. The arteriovenous shunting causes an abrupt change in blood flow and results in increased fluidic stress, which predisposes to access stenosis and thrombosis. While access flow is crucial to evaluate interventional endpoint, application to measure flow using digital angiogram is not yet available. The goal of this study was to determine the feasibility of flow quantification in dialysis access using a software tool and to guide the design of an imaging protocol.

METHODS

173 digital subtraction angiographic (DSA) images were retrospectively analyzed to evaluate access flow in a custom-programming environment. Four bolus transit time algorithms and a distance calculation method were assessed for flow computation. Gamma variate function was applied to remove secondary flow and intensity outliers in the bolus time-intensity curves and evaluated for enhancement in computational accuracy. The percent deviations of flow rates computed from dilution of iodinated radio-contrast material were compared with in situ catheter-based flow measurement.

RESULTS

Among the implemented bolus transit time algorithms, quantification error (mean ± standard error) of cross-correlation algorithm without and with gamma variate curve fitting was 35 ± 1% and 22 ± 1%, respectively. All other algorithms had quantification error >27%. The bias and limits of agreement of the cross-correlation algorithm with gamma variate curve fit was -94 ml/min and [-353, 165] mL/min, respectively.

CONCLUSIONS

The cross-correlation algorithm with gamma variate curve fit had the best accuracy and reproducibility for image-based blood flow computation. To further enhance accuracy, images may need to be acquired with a dedicated injection protocol with predetermined parameters such as the duration, rate and mode of bolus injection, and the acquisition frame rate.

A new technique for measuring fistula flow using venous blood gas oxygen saturation in patients with a central venous catheter

Background

Doppler ultrasound (DU) monitoring early after arteriovenous fistula (AVF) creation allows the identification of low blood flow (Qa) requiring prompt revision, but it is costly (needs skilled operators and technical instruments) and is not available in all dialysis units. Therefore alternative first-line methods to measure Qa would be welcomed. We reasoned that once an AVF is created, an increment in central venous oxygen saturation (ScvO₂) is predictable and proportional to Qa.

Methods

Accordingly, in patients receiving dialysis through a central venous catheter (CVC) in whom an AVF was created, we measured, by means of blood gas analysis, the ScvO₂ increment before and after manual compression of the arteriovenous shunt and verified its correlation with DU-measured Qa.

Results

We sampled blood gas in 18 patients with CVC and AVF before and after 30 s manual compression of the AVF. ScvO₂ averaged 70.5 ± 3% before and 65.2 ± 3% after AVF closure, with an average drop of 5.1 ± 3% (range 1-12). AVF Qa, which was measured within 24 h by means of DU, averaged 635 ± 349 mL/min (range 50-1300) and was strictly and positively correlated with ΔScvO₂ (r = 0.954, P < 0.0001).

Conclusions

Therefore we suggest that in patients with CVC and a newly created AVF, it is possible to monitor AVF Qa without DU by simply measuring blood gas and ΔScvO₂. This technique is simple, cheap, repeatable, non-invasive and operator independent and represents a new useful screening test to detect delayed AVF access maturation deserving prompt DU measurement and surgical revision. It helps to quickly identify patients in urgent need of DU verification and possible surgical revision. Regrettably, it is applicable only in patients with CVC.