Is Routine Preoperative Ultrasonographic Mapping for Arteriovenous Fistula Creation Necessary in Patients with Favorable Physical Examination Findings? Results of a Randomized Controlled Trial

When should a patient receive an arteriovenous graft rather than a fistula?

There has been a dramatic increase in the placement and use of arteriovenous fistulas (AVF) in US patients with chronic kidney disease over the past few years, in accordance with strong recommendations by Fistula First Initiative and KDOQI guidelines. However, AVF nonmaturation remains a substantial obstacle to achieving functional AVFs in a subset of patients, despite the widespread use of preoperative vascular mapping to assist surgeons in planning access surgery, and the growing use of interventions to salvage nonmaturing AVFs. In the right patient, aggressive efforts result in a functioning AVF, which provides adequate dialysis with relatively few interventions required to maintain its long-term patency for dialysis. In the wrong patient, aggressive efforts to achieve a mature AVF may result in numerous failed surgical and percutaneous procedures and prolonged catheter dependence, with all its associated complications. Thus, strict recommendations to place an AVF in all dialysis patients might not benefit every patient, and may actually harm some patients. There are no randomized clinical trials to address which patients are more suitable for placement of an arteriovenous graft (AVG), rather than an AVF. However, there is a wealth of observational studies, which taken cumulatively, may assist clinicians in identifying those patients who should receive an AVG. In this article, we review the relevant published literature regarding this topic and provide suggestions for stratifying patients who should receive each type of vascular access.

The Clinical Utility of Vascular Mapping with Doppler Ultrasound Prior to Arteriovenous Fistula Construction for Hemodialysis Access

Purpose

To compare the outcomes of vascular access (VA) procedures performed using physical examination (PE) alone to PE and ultrasound vein mapping for assessment of patients needing hemodialysis access.

Methods

Comparative analysis of data obtained by retrospective review of records of 63 patients who underwent PE and vascular mapping (VM) using colored Doppler ultrasonography (CDUS) and 76 patients assessed by physical examination alone to schedule vascular access surgery. The parameters assessed to study the impact of these two different pre-operative assessment approaches included selection of surgical site, procedure, construction of arteriovenous fistulas (AVF) and grafts (AVG), negative surgical exploration rates and surgical outcomes (maturation and patency rates).

Results

The rate of successfully constructed AVF increased significantly from 75% to 97% (P=.001) with pre-operative ultrasonographic vascular mapping. In 22 patients (34.9%) the access planned with physical examination was modified based on CDUS examination. In 12 patients, the surgical site for AVF creation and type of surgical procedure were modified based on the CDUS results. Permanent access placement rates were significantly higher in patients assessed with CDUS (P=.001). All patients who underwent vascular mapping had successful VA construction while the PE group had a 18.4% negative surgical exploration rate. When fistulas were assessed at six months, the patency rate was 80.7% for the physical examination (PE) group and 93.4% for the vascular mapping (VM) group.

Conclusions

Pre-operative vascular mapping using CDUS significantly increases the success of AVF construction and patency.

Factors affecting the patency of arteriovenous fistulas for dialysis access

BACKGROUND

The autologous arteriovenous fistula (AVF) is the accepted gold standard mode of repeated vascular access for hemodialysis in terms of access longevity, patient morbidity, and health care costs. This review assesses the current evidence supporting the role of various patient and surgeon factors on AVF patency.

METHODS

The literature was searched to identify the current evidence available for patient characteristics, methods of AVF planning, and anatomic factors that may affect patency outcomes after AVF formation. The use of adjuvant medications, surgical techniques, and policies for AVF maintenance are discussed in relation to AVF patency.

RESULTS

Current literature supports patient factors, such as increasing age, presence of diabetes, smoking, peripheral vascular disease, predialysis hypotension, and vessel characteristics, as directly influencing AVF patency. Vessels of small caliber (<2 mm) or demonstrating reduced distensibility are unlikely to create a functional AVF. Current evidence does not support altered patency due to sex or raised body mass index (<35 kg/m(2)). Factors such as early referral for AVF, preoperative ultrasound vessel mapping, use of vascular staples, and intraoperative flow measurements affected AVF patency, but the use of medical adjuvant therapies did not. Programs of surveillance and various needling techniques to maintain patency are not supported by current evidence. Novel techniques of infrared radiotherapy and topical glyceryl trinitrate are possible future strategies to increase AVF patency rates. The limitations of available evidence include a lack of large, randomized controlled trials and meta-analysis data to support current practice.

CONCLUSIONS

There is a complex interaction of factors that may affect the patency of an individual AVF. These need to be carefully considered when selecting surgical site or technique, adjuvant treatments, and follow-up protocols for AVFs.

Routine preoperative vascular ultrasound improves patency and use of arteriovenous fistulas for hemodialysis: a randomized trial

BACKGROUND AND OBJECTIVES

Arteriovenous fistulas (AVFs) are the preferred vascular access for hemodialysis but have a considerable failure rate. This study investigated whether routine preoperative vascular ultrasound results in better AVF outcome than physical examination.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with end-stage kidney disease referred for permanent access formation were assessed by independent examiners using physical examination and ultrasound. After random allocation, the ultrasound report was disclosed to the surgeon for patients in the ultrasound group but not for the clinical group. End points were AVF failure and survival rates, analyzed by intention to treat and by use for hemodialysis.

RESULTS

AVFs were made in 208 of 218 randomized patients. Clinical and ultrasound groups were similar in terms of patient characteristics, allocation to individual surgeons, and proportion of forearm AVFs. The ultrasound group had a significantly lower rate of immediate failure (4% versus 11%, P = 0.028) and, among failed AVFs, less thrombosis (38% versus 67%, P = 0.029). Primary AVF survival at 1 year was not statistically different (ultrasound = 65%, clinical = 56%, P = 0.081). Assisted primary AVF survival at 1 year was significantly better for the ultrasound group (80% versus 65%, P = 0.012). The number of patients requiring preoperative ultrasound to prevent one AVF failure was 12.

CONCLUSIONS

Routine preoperative vascular ultrasound in addition to clinical assessment improves AVF outcomes in terms of patency and use for dialysis. National Research Register, United Kingdom, trial number N0046131432.

Duplex sonography in the planning and evaluation of arteriovenous fistulae for haemodialysis

This paper describes how to perform duplex sonography in the planning and evaluation of arteriovenous fistulae in haemodialysis patients, discusses its roles in these settings, and presents a review of commonly encountered complications.

Preoperative mapping for haemodialysis access surgery with CO(2) venography of the upper limb

OBJECTIVE

This study aims to evaluate the impact of CO(2) venography on the planning and outcome of native arteriovenous fistula (AVF) creation.

METHODS

Records of patients who underwent CO(2) venography prior to access surgery between January 2000 and December 2008 were reviewed. CO(2) venography was performed selectively in chronic kidney disease (CKD) in stage IV-V patients without suitable veins on clinical examination. Findings at surgery were compared to CO(2) venography images. Patency of AVFs was analysed by the Kaplan-Meier method. Differences in outcome of maturation were compared using a chi(2) test.

RESULTS

A total of 209 CO(2) venograms were obtained in 116 patients. In 89 patients (77%), 101 AVFs (21 forearm AVF (21%) and 80 elbow AVF (79%) were created. Surgical findings corresponded with CO(2) venography findings in 90% of patients. In 10 cases (10%), access was created at the elbow despite a patent forearm cephalic vein on CO(2) venography (n = 2) or access was attempted with a vein which was thought to be unsuitable on CO(2) venography (n = 8). Maturation rate of the latter was 50% (4/8) vs. 88% (80/91) for AVFs created with veins considered usable (P = 0.004). The overall maturation rate was 84% with 1-year primary, assisted primary and secondary patency rates of 63%, 70% and 71%, respectively.

CONCLUSION

CO(2) venography is a useful tool for venous mapping prior to vascular access surgery, resulting in an overall maturation rate of 84% and good patency rates.

Preoperative Evaluation for Vascular Access Creation

In an effort to increase the prevalence of arteriovenous fistulae (AVF), ultrasound vessel mapping (USVM) and upper extremity venography (UEV) have been suggested; however, the effectiveness of their combined use remains unknown. We studied the effect of such a combined protocol on arteriovenous (AV) access type change compared with physical examination alone. Consecutive patients with chronic kidney disease ( n = 137) after an initial estimation of the AV access type, based on physical examination, had USVM and UEV to detect vascular pathology that could potentially alter the original plan. USVM changed the preoperative plan in 31 (22.6%) patients; this was 36.7% ( n = 18) in diabetics compared with 14.8% ( n = 13) in nondiabetics ( p < .001). Patients for whom USVM changed the type of planned AV access had been on hemodialysis significantly longer (2.7 years vs 0.9 years; p < .001). Venography identified 18 patients with central vein stenosis that led to a site change in 12 of them. Significant venous stenosis in patients with a history of two or more central catheters placed and patients without such a history was 93% and 1%, respectively. In eight patients, intraoperative findings dictated AV graft placement or creation of a central AVF. The original plan was revised in 31%, and this rate was similar for distal AVF, central AVF, and AV grafts (38%, 26%, and 43%, respectively; all p > .05). The 30-day patency rate was 92.2%. A significant proportion of patients have vascular pathology severe enough to alter the access type as suggested by physical examination alone. USVM should be routinely performed, whereas UEV should be selectively performed in patients with a history of surgery or instrumentation of their central veins.

Gender differences in vascular access in hemodialysis patients in the United States: developing strategies for improving access outcome

BACKGROUND

Patients undergoing chronic hemodialysis (HD) require placement of permanent vascular access with the creation of an arteriovenous fistula (AVF), an arteriovenous prosthetic graft (AVG), or a tunneled central venous catheter. AVFs provide greater long-term patency, fewer complications, and lower infection rates than do either AVGs or catheters. Despite these advantages, women continue to be underrepresented among AVF patients, possibly because of concerns about smaller vascular diameters and higher rates of early primary fistula failure in female HD patients. The numerous clinical benefits of AVF suggest that a greater effort should be made to promote AVF placement in women.

OBJECTIVE

This review analyzes risk factors for AVF failure in women and describes clinical strategies to improve AVF utilization and success for female HD patients.

METHODS

English-language publications were identified through a MEDLINE database search from January 1997 to March 2007, using the search terms arteriovenous fistula, vascular access, hemodialysis, female, and gender. Reference lists of identified articles were also reviewed.

RESULTS

There are significant benefits to using AVFs instead of AVGs or catheters in HD patients: greater long-term fistula patency, superior flow rates, and fewer complications. Vascular anatomical differences between the sexes contribute to the underutilization of AVF in women. AVF placement rates can be improved if patients and staff are adequately educated and provided with the tools to facilitate AVF placement. Noninvasive preoperative screening is important to identify superior access sites in women. Intraoperative monitoring of blood flow is a reliable predictor of early radiocephalic AVF patency. Routine postoperative vascular monitoring may improve overall success with AVF, and exercise may improve vascular diameter and may be even more beneficial for women, who may have smaller preoperative veins.

CONCLUSIONS

Concerns about smaller vascular diameters and reports of higher failure rates in women may prevent nephrologists and surgeons from considering AVF for female HD patients. The numerous advantages associated with AVF suggest that a greater effort should be made to increase its utilization in women. With appropriate motivation, care, and diligence by treating clinicians, the success of AVFs in women can approach the good results typically expected in men.