Access flow measurement during surveillance and percutaneous transluminal angioplasty intervention

Hemodialysis vascular access flow measurements by the novel DMed NephroFlow® device: A comparative study with Transonic®

INTRODUCTION

The current Spanish Clinical Guidelines on Vascular Access for Hemodialysis support the need for surveillance and monitoring of vascular access (VA) to avoid complications. Ultrasound dilution (UD) methods are accepted for the evaluation of VA flow and Transonic® has established the gold standard method for the measurement. The DMed NephroFlow (NIPRO®) device, based on UD method has recently been incorporated. We report a comparative study between the classic Transonic® versus the new NephroFlow® device.

MATERIAL AND METHODS

For two consecutive months, measurements of VA flow using both referred systems were performed in patients with a native arteriovenous fistula (AVF) or a graft (AVG) on hemodialysis (HD) in our unit. Both studies were undertaken according to the usual recommendations: VA flow of 250 ml/min, ultrafiltration rate without modifications, both needles in the same vein, and always in the first hour of the HD session.

RESULTS

Forty-five patients were included: 17 women and 28 men, mean age of 67 ± 12 years. Thirty patients were diabetic. The baseline meantime on HD was 51 ± 39 months (range: 3-163). Type of VA was: 17 patients radio-cephalic AVF, 17 brachiocephalic AVF, 7 brachiobasilic AVF, and 3 with a graft. The mean flow estimated by the Transonic® was 1222 ± 805 ml/min and the estimated flow by the NephroFlow® device was 1252 ± 975 ml/min. Good reliability between Transonic® and NephroFlow® was observed, with a reliability index of Cronbach's Alpha of 0.927 and an Intraclass Correlation Index of 0.928.

CONCLUSIONS

The NephroFlow® device seems comparable with the accepted gold standard UD method for estimating VA flow. More studies must be performed to verify these results. However, they should be considered for the surveillance and monitoring of VA flow, in agreement with the Spanish Guidelines.

Access flow volume (Qa) and survival in a hemodialysis population: An analysis of 5208 Qa measurements over a 9-year period

BACKGROUND

Aim of the study was to determine associations between characteristics of arteriovenous access (AVA) access flow volume (Qa, mL/min) and four year freedom from cardiovascular mortality (4yr-CVM) in hemodialysis (HD) patients.

METHODS

HD patients who received a primary AVA between January 2010 and December 2017 in one center were analyzed. Initial Qa was defined as the first Qa value obtained in a well-functioning AVA by a two-needle dilution technique. Actual Qa was defined as access flow at a random point of time. Changes in actual Qa were expressed per 3-month periods. CVM was assessed according to the ERA-EDTA classification. The optimal cut-off point for initial Qa was identified by a receiver operating characteristic curve. A joint modelling statistical technique determined longitudinal associations between Qa characteristics and 4yr-CVM.

RESULTS

A total of 5208 Qa measurements (165 patients, male n = 103; age 70±12 years, autologous AVA n = 146, graft n = 19) were analyzed. During follow-up (Dec 2010-Jan 2018, median 36 months), 79 patients (48%) died. An initial Qa < 900 mL/min was associated with an increased 4y-CVM risk (HR: 4.05; 95% CI [1.94-8.43], P<0.001). After 4 years, freedom from CVM was 34% lower in patients with a Qa < 900 mL/min (53 ±7% vs. Qa ≥ 900 mL/min: 87 ±4%, P <0.001). An association between increases in actual Qa over 3-month periods and mortality was found (HR: 4.48 per 100mL/min, 95% CI [1.44-13.97], P =0.010) indicating that patients demonstrating increasing Qa were more likely to die. By contrast, actual Qa per se was not related to survival.

CONCLUSIONS

Studying novel arteriovenous access Qa characteristics may contribute to understanding excess CVM in HD patients.

Invasive radiologic management of hemodialysis fistulas: measuring flow with an endovascular catheter

OBJECTIVES

To analyze the values of flow obtained with an endovascular catheter, and to determine whether they are more reliable than angiographic and clinical findings for planning and for determining the outcome of invasive radiologic treatment of hemodialysis fistulas, as well as to determine the safety of this technique during interventional radiology procedures.

MATERIAL AND METHODS

We used endovascular catheters to measure flow in 341 vascular accesses for hemodialysis (162 [47.6%] distal fistulas, 132 [38.4%] humeral fistulas, and 47 [14%] arteriovenous grafts) in 598 procedures (a total of 3,051 flow measurements). Dysfunction was most commonly due to high pressures and flow deficits.

RESULTS

The catheter was used to measure the results of radiologic treatment in 419 (70%) cases and only to measure the control of flow in the hemodialysis access in 179 (30%) cases. In the cases where lesions of the access had been treated radiologically, the flow improved by a mean of 1,232ml/min. In 2 (0.35%) cases, the tip of the catheter perforated the wall of the vein; this complication was resolved by inflating a low pressure balloon.

CONCLUSIONS

Endovascular catheters are useful for measuring flow in invasive vascular radiology procedures for hemodialysis. In assessing the hemodynamic status of a vascular access, they are most helpful in determining whether stenosis is present.

Effect of intradialytic change in blood pressure and ultrafiltration volume on the variation in access flow measured by ultrasound dilution

BACKGROUND

Prospective access flow measurement is the preferred method for vascular access surveillance in hemodialysis (HD) patients. We studied the effect of intradialytic change in blood pressure and ultrafiltration volume on the variation in access flow measured by ultrasound dilution.

METHODS

Access flow was measured 30 minutes, 120 minutes, and 240 minutes after the start of HD by ultrasound dilution in 30 patients during 89 HD sessions and evaluated for variation.

RESULTS

The mean age of the 30 patients was 62±11 years: 19 were male. The accesses comprised 16 fistulae and 14 grafts. The mean access flow over all sessions decreased by 6.1% over time (1265±568 mL/min after 30 minutes, 1260±599 mL/min after 120 minutes, and 1197±576 mL/min after 240 minutes, P<0.01 by repeated measures ANOVA). In addition, a≥5% decrease in mean arterial pressure during HD significantly reduced access flow (P=0.014). However, no other variable (ultrafiltration volume, sex, age, presence of diabetes, type or location of access, body surface area, hemoglobin, serum albumin level) interacted significantly with the effect of time on access flow. Furthermore, mean arterial pressure did not correlate with ultrafiltration volume.

CONCLUSION

We conclude that the variation in access flow during HD is relatively small. Decreased blood pressure is a risk factor for variation in access flow measured by ultrasound dilution. In most patients whose blood pressures are stable during HD, the access flow can be measured at any time during the HD treatment.

Independent prediction factors for primary patency loss in arteriovenous grafts within six months

PURPOSE

The objective of this study was to explore the association between loss of primary functional patency within 6 months of first use and demographic and clinical characteristics in patients with arteriovenous grafts (AVGs) receiving chronic hemodialysis. The knowledge and management of these characteristics will minimize the proportion of catheterdependent dialysis patients for whom AVGs are the best choice.

METHODS

This was a retrospective study of all chronic hemodialysis patients with AVGs followed by the Southern Alberta Renal Program from January 2005 to June 2008. Demographic and clinical variables and initial intra-access blood flow (IABF) were compared between those with and without loss of primary functional patency. To determine the contribution of independent variables to the dependant variable of loss of primary functional patency, a multivariable analysis using logistic regression was performed.

RESULTS

The incidence of primary failure was 30% (107/359). Multivariable analysis found that low initial IABF (<650 mL/ min, odds ratio [OR] 31, P < 0.001), presence of diabetes (OR 3.5, P = 0.001), older age (>65 years OR 3.2, P< 0.001), and presence of peripheral vascular disease (OR 2.5, P< 0.005) were independently associated with loss of primary patency.

CONCLUSIONS

AVGs are sometimes a better choice for those patients in which the time to and probability of successful fistula maturation may be a concern. Close monitoring of AVGs in patients with the identified risk factors associated with loss of primary patency may improve the life expectancy of the access.

Risk factors associated with patency loss of hemodialysis vascular access within 6 months

BACKGROUND AND OBJECTIVES

Clinical guidelines support vascular access surveillance to detect access dysfunction and alter the clinical course by radiologic or surgical intervention. The objective of this study was to explore the association between loss of primary functional patency within 6 months of first use and demographic and clinical characteristics of patients receiving chronic renal replacement therapy with arteriovenous fistulas.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a retrospective study of all chronic hemodialysis patients followed by the Southern Alberta Renal Program from January 1, 2005 to June 30, 2008. Demographic and clinical variables and initial intra-access blood flow (IABF) were compared between those with and without loss of primary functional patency. To determine the contribution of independent variables to the dependant variable of loss of primary functional patency, a multivariable analysis using logistic regression was performed.

RESULTS

The incidence of primary failure was 10% (81 of 831). Multivariable analysis found that older age (>65 years, odds ratio [OR] 3.6, P < 0.001), history of diabetes (OR 2.3, P = 0.007), history of smoking (OR 4.3, P < 0.001), presence of forearm fistulas (OR 4.0, P < 0.001), and low initial IABF (<500 ml/min, OR 29, P < 0.001) were independently associated with loss of primary patency.

CONCLUSIONS

The set of patient risk factors identified in this study, particularly initial IABF, can be used to identify patients who are most at risk for developing vascular access failure and to guide a more directed approach for a vascular access screening protocol.

Arterial line pressure control enhanced extracorporeal blood flow prescription in hemodialysis patients

Background

In hemodialysis, extracorporeal blood flow (Qb) recommendation is 300–500 mL/min. To achieve the best Qb, we based our prescription on dynamic arterial line pressure (DALP).

Methods

This prospective study included 72 patients with catheter Group 1 (G1), 1877 treatments and 35 arterio-venous (AV) fistulae Group 2 (G2), 1868 treatments. The dialysis staff was trained to prescribe Qb sufficient to obtain DALP between -200 to -250 mmHg. We measured ionic clearance (IK: mL/min), access recirculation, DALP (mmHg) and Qb (mL/min). Six prescription zones were identified: from an optimal A zone (Qb > 400, DALP -200 to -250) to zones with lower Qb E (Qb < 300, DALP -200 to -250) and F (Qb < 300, DALP > -199).

Results

Treatments distribution in A was 695 (37%) in G1 vs. 704 (37.7%) in G2 (P = 0.7). In B 150 (8%) in G1 vs. 458 (24.5%) in G2 (P < 0.0001). Recirculation in A was 10.0% (Inter quartile rank, IQR 6.5, 14.2) in G1 vs. 9.8% (IQR 7.5, 14.1) in G2 (P = 0.62). IK in A was 214 ± 34 (G1) vs. 213 ± 35 (G2) (P = 0.65). IK Anova between G2 zones was: A vs. C and D (P < 0.000001). Staff prescription adherence was 81.3% (G1) vs. 84.1% (G2) (P = 0.02).

Conclusion

In conclusion, an optimal Qb can de prescribed with DALP of -200 mmHg. Staff adherence to DLAP treatment prescription could be reached up to 81.3% in catheters and 84.1% in AV fistulae.

Effect of online haemodialysis vascular access flow evaluation and pre-emptive intervention on the frequency of access thrombosis

Introduction. Guidelines advocate surveillance of vascular access to reduce incidences of thrombosis. However, the value of online vascular access flow monitoring is still under debate.

Methods. Through a systematic literature search, the effect of online access flow surveillance combined with pre-emptive intervention on thrombosis frequency is reviewed.

Results. Due to methodological differences, adequate comparison of the individual study results is not possible. Moreover, the methodological quality of most of the included studies is not suitable for an adequate statistical analysis of the results.

Conclusion. Until now, there is no conclusive evidence that online access flow evaluation has a significant effect on the rate of thrombosis. Future large-scale studies with adequate study design, adequate surveillance and intervention protocols and, possibly, better pre-emptive intervention alternative(s) are necessary.