Determinants of native arteriovenous fistula blood flow

Preoperative Cardiac Index as a Predictor of Maturation and Primary Patency of Radiocephalic Arteriovenous Fistula in Hemodialysis

BACKGROUND

Radiocephalic arteriovenous fistula (RCAVF) is the best access modality to be considered initially when planning arteriovenous fistula (AVF) for maintenance hemodialysis. Considering the higher incidence of RCAVF failed maturation (M), it is important to perform proper preoperative evaluation and identification of high-risk patients. There has been no study on the influence of preoperative cardiac function on the M and patency of AVFs. The purpose of this investigation is to determine whether preoperative cardiac index (CI) is a predictor of M and primary patency of RCAVF.

METHOD

A total of 365 end-stage renal disease patients undergoing RCAVF surgery were consecutively enrolled with a median follow-up time of 20 months in this prospective cohort study. Demographics, vascular diameters measured by duplex ultrasound examination, and CI measured by echocardiography, were analyzed for effect on RCAVF primary functional M and primary patency.

RESULT

Patients in the group achieving primary RCAVF functional M had a significantly larger mean CI than the group with early RCAVF failure (2.93 ± 0.77 vs. 3.57 ± 0.76 L/min/m2, p < 0.001). The receiver operating characteristic curve was plotted and demonstrated that preoperative vein diameter and CI can predict failure of RCAVF M. The AUC of CI was higher (0.745 vs. 0.666). Multivariate regression analysis, adjusted for age, sex, diabetes, preoperative dialysis status and vessel diameters, showed that decreased CI remained associated with increased risk of failure of M (FM) and worse primary unassisted patency. The Kaplan-Meier survival analysis suggested that patients with CI <3 L/min/m2 had a worse primary unassisted patency rate at all time points compared with patients with CI ≥3 L/min/m2.

CONCLUSION

This study demonstrated that preoperative CI was associated with RCAVF M and long-term patency. A decreased CI may be a possible predictor of an increased risk of FM and a shorter primary patency time.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for hemodialysis vascular access since 1996. Since the last update in 2006, there has been a great accumulation of new evidence and sophistication in the guidelines process. The 2019 update to the KDOQI Clinical Practice Guideline for Vascular Access is a comprehensive document intended to assist multidisciplinary practitioners care for chronic kidney disease patients and their vascular access. New topics include the end-stage kidney disease "Life-Plan" and related concepts, guidance on vascular access choice, new targets for arteriovenous access (fistulas and grafts) and central venous catheters, management of specific complications, and renewed approaches to some older topics. Appraisal of the quality of the evidence was independently conducted by using a Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and interpretation and application followed the GRADE Evidence to Decision frameworks. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Influence of intraoperative findings on immediate flow through radial-cephalic arteriovenous wrist fistulas for hemodialysis access

Background

Adequate flow through a newly created arteriovenous fistula depends on multiple characteristics of the vessels and patient comorbidities. Several studies have related preoperative findings to failure, but few have analyzed the influence of intraoperative findings.

Objectives

To evaluate the predictive value of intraoperative findings on the immediate outcome of radial-cephalic arteriovenous wrist fistulas (RCAVF) by collecting data that are easily measured intraoperatively.

Methods

We designed a cross-sectional study, in which a single surgeon performed 101 RCAVF in 100 patients at a single center. We analyzed the immediate postoperative flow, assessed by thrill intensity immediately after fistula creation, against patient demographics and intraoperative data. The following variables were analyzed: age, sex, comorbidities, length of vein visible at preoperative examination, macroscopic arterial calcification, maximum vein diameter, and length of stenosis-free vein, measured by cannulation with a urethral catheter during the procedure. The chi-square test was used both to eliminate possible bias introduced by side of venous access (left or right), and to determine predictive values of immediate thrill.

Results

Side of access was not associated with any significant differences in variables. Absence of macroscopic arterial calcification, successful venous catheterization using a 6 French catheter or larger, and ability to advance it more than 10 centimeters along the lumen of the proximal vein were correlated with adequate immediate postoperative thrill (p = 0.004, p < 0.001, and p = 0.005, respectively).

Conclusions

In this series of 101 RCAVF, both the diameter of the catheter and its progress through the proximal vein and also absence of arterial calcification had positive predictive value for achieving adequate immediate thrill after vascular access construction.

Higher arteriovenous fistulae blood flows are associated with a lower level of dialysis-induced cardiac injury

Native arteriovenous fistulae (AVF) remain the vascular access of choice for hemodialysis (HD). Despite being associated with superior long-term outcomes (cf. catheter use), little is known about the systemic hemodynamic consequences of AVFs. Repetitive myocardial injury (myocardial stunning) is an under-recognized common consequence of HD. The aim of this study was to examine the impact of AVF flow (Qa) on dialysis-induced cardiac injury. We studied 50 chronic HD patients. All patients underwent echocardiography (and subsequent quantitative offline analysis) at baseline, during and post dialysis, to assess left ventricular function and the development of regional wall motion abnormalities. Qa was measured using ionic dialysance. Patients were divided into Qa tertiles (<500, mean 291+/-101 mL/min, 500-1000, mean 739+/-130 mL/min and >1000, mean 1265+/-221 mL/min). There were no significant differences between the groups in terms of age, sex, diabetes, or resting ejection fraction. Patients with Qa>1000 mL/min had a lower prevalence of left ventricular hypertrophy (55% vs. 76%, P=0.01). Dialysis-induced myocardial stunning (seen in 65% of the patients studied) was significantly and sequentially reduced in those patients with higher Qas. This was seen in a lower number of segments and ventricular regions developing regional wall motion abnormalities, as well as a significantly reduced mean and cumulative percentage reduction in fractional shortening of those ventricular segments affected (-187+/-37%, -161+/-26%, and -101+/-25%, respectively, P=0.04). Relatively higher AVF flows appear to be associated with a lower level of observed HD-induced cardiac injury.

Angiotomographically-proven Left Innominate Vein Occlusion in Dialysis Patients With Prior Left Internal Jugular Vein Catheterization Presenting With Arm Swelling After Ipsilateral Access Creation: Report of Four Cases

Central vein occlusion (CVO) is not uncommonly observed after hemodialysis (HD) catheter placement and it may prevent subsequent ipsilateral arteriovenous (AV) access creation. Right internal jugular vein catheterization (RJVC) appears to be the insertion site with the lowest incidence of CVO, but little is known about the incidence of CVO following left internal jugular vein catheterization (LJVC). We report on four patients with left innominate vein occlusion after LJVC who developed severe arm swelling after ipsilateral AV access creation. In three of the four cases swelling appeared 12-26 months after access creation, and in the fourth, swelling developed immediately after surgery while the catheter was still in place. Two patients underwent access ligation and in the remainder the arm swelling improved either spontaneously or after LJVC removal. LJVC is not as safe as RJVC as an insertion route for HD catheter placement in terms of CVO frequency.

Does monthly native arteriovenous fistula blood-flow surveillance detect significant stenosis--a randomized controlled trial

BACKGROUND

Clinical practice guidelines recommend that the preferred method of surveillance for arteriovenous fistula (AVF) is the measurement of AVF blood flow (Qa). As these recommendations are based on observational studies, we conducted a randomized, prospective, double-blind, controlled trial to assess whether Qa surveillance results in an increased detection of AVF stenosis.

METHODS

A total of 137 patients were randomly assigned to receive either continuing AVF surveillance using current clinical criteria (control, usual treatment) or usual treatment plus AVF blood-flow surveillance by ultrasound dilution (Qa surveillance group). The primary outcome measure was the detection of a significant (>50%) AVF stenosis.

RESULTS

There were 67 and 68 patients assigned to the control and Qa surveillance groups, respectively. Patients in the Qa surveillance group were twice as likely to have a stenosis detected compared with the control hazard ratio (HR) confidence interval (CI) group (2.27, 95% 0.85-5.98, P = 0.09), with a trend for a significant stenosis to be detected earlier in the Qa surveillance group (P = 0.09, log rank test). However, using the Qa results alone prior to angiography, the area under the receiver operating characteristic curve demonstrated, at best, a moderate prediction of (>50%) AVF stenosis (0.78, 95% CI 0.63-0.94, P = 0.006).

CONCLUSION

This study demonstrates that the addition of AVF Qa monitoring to clinical screening for AVF stenosis resulted in a non-significant doubling in the detection of angiographically significant AVF stenosis. Further, large multi-centre randomized trials are feasible and will be necessary to confirm whether Qa surveillance and the correction of detected AVF stenosis will lead to a reduction in AVF thrombosis and increased AVF survival.

Primary Vascular Access

Primary vascular access is usually achievable by a distal autogenous arterio-venous fistula (AVF). This article describes the approach to vascular access planning, the usual surgical options and the factors affecting patency.

The Relation Between Vascular Access Flow and Different Types of Vascular Access With Systemic Hemodynamics in Hemodialysis Patients

Access flow (Qa) has an important effect on systemic hemodynamics in dialysis patients. A Qa : cardiac output (CO) ratio higher than 0.3 is considered a risk factor for high-output cardiac failure. However, the effect of different types of vascular access in hemodialysis patients has not yet been studied. The aim of the present study was to assess the relationship between Qa and systemic hemodynamics and to compare systemic hemodynamics between patients with elbow/upperarm access with forearm access types. Qa, CO, cardiac index (CI), central blood volume (CBV), and peripheral vascular resistance (PVR) were studied by the saline dilution technique in 58 hemodialysis patients (18 with elbow/upperarm access; 40 with forearm access types). This article found that Qa was significantly and positively related to CO and CI, and inversely related to PVR. CBV, Qa, and presence of cardiac failure were independent determinants of CI. Qa and the Qa : CO ratio were significantly higher, and PVR significantly lower, in patients with elbow/upperarm access compared to patients with forearm access types. When patients with cardiac failure were excluded, CO and CI were also significantly higher in patients with elbow/upperarm access types. Eleven percent of patients with elbow/upperarm fistula had a Qa : CO ratio above 0.3. In conclusion, Qa is strongly related to systemic hemodynamics in dialysis patients. In patients without cardiac failure, CO and CI are significantly higher in patients with elbow/upperarm access compared to patients with forearm access types. However, only a small percentage of patients with elbow/upperarm fistulae appeared to be in the risk zone for development of high-output cardiac failure.