Teun Wilmink

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.

Accuracy of early postoperative clinical and ultrasound examination of arteriovenous fistulae to predict dialysis use

Aim The aim of this article is to assess the accuracy of early clinical and ultrasound (US) examination in terms of predicting arteriovenous fistula (AVF) dialysis use. Methods Physical and US examination of patent AVF was performed 4 weeks after fistula creation. AVF dialysis use was defined as subsequent use of an AVF for at least six consecutive dialysis sessions with two needles and a blood flow of more than 200 mL/min. Results Of 119 AVF patent at 4 weeks, 26 (22%) failed. Clinical examination was 96% sensitive for predicting successful dialysis, but only 21% specific for failure. Vein diameter above 5 mm and an arterial end-diastolic velocity above 110 cm/s were the best US predictors for dialysis use. Vein diameter was slightly better than arterial velocity in terms of predicting maturity (sensitivity: 83% vs 67%, specificity: 68% vs 65%). All assessments predicted AVF maturity (positive predictive value: clinical = 81%, US diameter = 90%, US velocity = 87%) much better than AVF failure (negative predictive value: clinical = 63%, US diameter = 53%, US velocity = 37%). Conclusion One month after surgery, a new AVF with a thrill or a vein diameter >5 mm is likely to be used for dialysis. An AVF not meeting these criteria has an increased risk of failure and further investigations may be required.

Measurement of arterial stiffness in subjects with and without renal disease: Are changes in the vessel wall earlier and more sensitive markers of cardiovascular disease than intima media thickness and pulse pressure?

There is increased cardiovascular (CV) mortality in subjects with chronic kidney disease (CKD). Arterial stiffness in these subjects is increased when compared to a healthy population. Markers of arterial stiffness and intima media thickness (IMT) are predictors of CV mortality. The aim of this study was to investigate whether there is any difference in markers of arterial stiffness and IMT between subjects with normal renal function and those with mild renal disease. The arterial distension waveform, IMT, diameter, and brachial blood pressure were measured to calculate Youngs modulus (E) and elastic modulus (Ep) in the common carotid arteries of subjects with normal kidney function (estimated glomerular filtration rate [eGFR] >90) and those mild CKD (stage 2, eGFR 89–60). Data were available for 15 patients with normal kidney function and 29 patients with mild CKD. The subjects with mild CKD were older, but other co-variables were not significantly different. Both arterial wall stiffness parameters (E and Ep), but not IMT were significantly higher in the mild CKD group. Logistic regression demonstrated that only the arterial wall stiffness parameters (Ep and E) were independently associated with mild renal disease compared with normal, in a model adjusting for sex, age and diabetes and history of cardiovascular disease (CVD). E and Ep may be early markers of CVD in subjects with mild CKD that may manifest change before other more recognized markers such as IMT and pulse pressure.

UK organisation of access care

National UK audits show that 73% of patients start renal replacement therapy (RRT) with haemodialysis (HD). However, 59% of those start HD on non-permanent access in the form of a tunnelled line (TL) or a non-tunnelled line (NTL), 40% on an arteriovenous fistula (AVF) and 1% on an arteriovenous graft (AVG). After 3 months, the number of patients dialysing on AVF was only 41%. Late referrals, within 90 days of starting dialysis to the renal service, occur in one-fifth of all incident HD patients. Referral to a surgeon was an important determinant of mode of access at first dialysis. However, referral to a surgeon occurred in 67% of patients who were known to the nephrologist for over a year and in 46% of patients who were known to nephrology less than a year but more than 90 days. Best practice tariffs of the National Health Service (NHS) payment by results program have set a target of 75% of prevalent HD occurring via an AVF or AVG in 2011/2012, rising to 85% in 2013/2014. We suggest that this target is best achieved by increasing timely referral to a surgeon for creation of access before HD is needed.

Comparison of surgical and radiological interventions for thrombosed arteriovenous access

Introduction: To compare open surgical and radiological interventions for thrombosed arteriovenous access for dialysis. Methods: A retrospective analysis of access procedures and dialysis episodes from 1 December 2002 to 30 November 2015 with follow-up up to 1 August 2016. Hospital records and dialysis database interrogated for further interventions and length of functional use. Results: Some 128 surgical and 27 radiological thrombectomies were compared. Radiological treatment was successful in 24 (89%) cases and surgical interventions in 65 cases (51%; p < 0.001). In all, 82 (64%) of the 128 surgical thrombectomies had no additional treatment, 43 (34%) had a surgical revision and 3 cases (2%) had an on-table balloon angioplasty. All 27 interventional thrombectomies had an additional balloon angioplasty. Success rate was significantly increased after a surgical revision (74%) or balloon angioplasty (87%) compared to no adjuvant procedure (38%; p < 0.001). There was a trend towards higher primary failure rates of arteriovenous fistula thrombectomies in the upper arm (57%) compared to the arteriovenous fistula thrombectomies in forearm (40%) and arteriovenous graft thrombectomies (33%; p = 0.056). Assisted primary patency was better after interventional treatment compared to surgery (p = 0.02) and significantly better after thrombectomy with additional treatment (p = 0.005). Patency after surgical revision or balloon angioplasty of the access was similar (p = 0.15). More procedures were required to maintain the access after balloon angioplasty than after surgical revision, and intervention-free survival was better after surgical revision (p = 0.02). Conclusion: Revision procedures significantly increase success rate of access thrombectomies. Radiological thrombectomies have higher success rates but lower intervention-free survival and need more additional procedures to maintain patency.

Is early cannulation of an arteriovenous fistula associated with early failure of the fistula

Objective To study the effect of early cannulation of arteriovenous fistulas (AVF) on early AVF failure. Methods Analysis of two databases of access operations and dialysis sessions from 1/12/2002 till 1/4/2015. Follow-up until 1/4/2016. Functional dialysis use defined as six consecutive cannulations of the AVF with two needles. Early cannulation defined as needling of the AVF within 30 days of creation. Early failure was defined as abandonment for new form of access within 90 days of first cannulation. Machine blood-flow rates (BFR) of each dialysis session for the first 2 months collected from the dialysis database. Results We analysed 1167 AVFs with functional dialysis use. Some 148 AVFs (11%) were needled within 30 days. Early needling was not associated with increased early failure rates (p = 0.43). Early failure rates were lower in AVFs with six consecutive successful cannulations from the start (p = 0.002). There was a trend of reduced early failure rates (test for trend: p = 0.018) in the latter years of the study period, but no trend in early cannulation rates (p = 0.19). Failure to achieve six successful cannulations from the start was an independent predictor of early AVF failure but early needling was not an independent predictor in multivariate analysis. Average starting BFRs were higher in AVF that were needled early. Conclusions Early cannulation was not associated with early failure. Failure to achieve six successful cannulations from the start was an independent predictor of early failure. The trend in yearly variation of early failure rates suggests that evolving practices influenced early failure rates.

Should patients be on antithrombotic medication for their first arteriovenous fistulae

Purpose Evidence on the effect of antithrombotic medication on reducing early and late fistula failure is inconclusive. Antithrombotic use carries risks in patients with end-stage renal failure and could increase the risk of needling complications as a result of bleeding. The objectives of this study are to determine the effect of antithrombotic agents on early and late fistula failure and on the risk of interrupted start of cannulation of the fistula. Methods Retrospective analysis of two prospectively maintained databases of access operations and dialysis sessions of 671 patients who had their first fistula between 2004 and 2011. Early failure was defined as failure to reach six consecutive dialysis sessions at any time with two needles on the index form of access. Fistula survival was defined as the time from when the fistula was first used to fistula abandonment. Results Primary failure was similar between patients on antiplatelet (18.8%), anticoagulants (18.4%) or no antithrombotic medication (18.8%; p = 0.998). Antithrombotic medication did not have an effect on AVF survival (p = 0.86). Antithrombotic medication did not increase complicated cannulation rates, defined as the percentage of patients failing to achieve six uninterrupted dialysis sessions from the start (p = 0.929). Conclusions Antithrombotic medication had no significant effect on primary failure rate, long-term fistula survival or initial complicated cannulation rates in our study. This suggests that patients already on antithrombotic medication can continue taking them without increasing the risk of interrupted dialysis.

Elbow arteriovenous fistulae.

Multiple superficial veins in different anatomical configurations exist in the elbow. The resulting variety of elbow arteriovenous fistulae (AVFs) is described in this paper. A classification of elbow AVF in nontransposed AVF, transposed AVF and multiple outflow AVF is proposed. The nontransposed brachiocephalic AVF has the lowest primary failure rate and a good medium-term survival particularly in the elderly. The simplest technique is an end-to-side anastomosis of the median cubital vein to the brachial artery. In cases of small upper arm veins, a perforating vein AVF, using multiple outflow tracts, may be helpful to lower primary failure risk. In the era of vein mapping with portable ultrasound elbow AVF should be made when forearm veins are exhausted or too small. A side-to-side AVF in order to enhance retrograde flow in the median forearm vein seems rarely indicated, in particular considering the greater risk of steal and venous hypertension. A transposed brachiobasilic AVF is a tertiary access procedure after the simpler alternatives have been exhausted. There is conflicting evidence of the benefits of one-stage versus two-stage procedures. Therefore, the type of operation should be tailored to the individual patient.

Lower limb access

Lower limb vascular access is used as an access site in patients in whom all upper limb possibilities for arteriovenous access creation are exhausted or with bilateral upper limb central vein occlusions. Autologous arteriovenous fistulae (AVF) using the greater saphenous vein have disappointing results apart from the isolated success. Autologous AVF using the femoral vein transposition have good results both in terms of long-term patency and are associated with a 10-fold reduction in infection risk compared with arteriovenous grafts (AVGs). However, a femoral vein transposition is a major undertaking and is associated with an increased risk of ischaemic complications. It is not a good option for patients with established peripheral arterial disease, but may be a good alternative for the younger patient with a high infection risk. The type of lower-extremity vascular access should be carefully tailored to the individual patient.

Effect of first cannulation time and dialysis machine blood flows on survival of arteriovenous fistulas

Background To study the effect of cannulation time on arteriovenous fistula (AVF) survival. Methods. Analysis of two prospective databases of access operations and dialysis sessions from 12 January 2002 through 4 January 2015 with follow-up until 4 January 2016. First cannulation time (FCT), defined from operation to first cannulation, was categorized as <2 weeks, 2-4 weeks, 4-8 weeks, 8-16 weeks and ≥16 weeks. Early cannulation was defined as FCT within 4 weeks. AVF survival was defined as the date until the AVF was abandoned. Maximum machine blood flow rate (BFR) for the first 29 dialysis sessions on AVF was analysed. Results Altogether, 1167 AVF with functional dialysis use were analysed: 667 (57%) radial cephalic AVF, 383 (33%) brachiocephalic AVF and 117 (10%) brachiobasilic AVF. The 631 (54%) AVF created in on-dialysis patients were analysed separately from 536 (46%) AVF created in pre-dialysis patients. AVF survival was similar between cannulation categories for both pre-dialysis patients (P = 0.19) and on-dialysis patients (P = 0.83). Early cannulation was associated with similar AVF survival in both pre-dialysis patients (P = 0.82) and on-dialysis patients (P = 0.17). Six consecutive successful cannulations from the start were associated with improved AVF survival (P = 0.0002). A below-median BFR at the start of dialysis was associated with better AVF survival (P < 0.0001). A below-median increase in BFR in the first 2 months was associated with worse AVF survival (P = 0.007). The type of AVF, diabetes, pre-dialysis state at operation and six successful cannulations from the start were independent predictors for AVF survival. Conclusions FCT is not associated with AVF survival. Failures to achieve six successful cannulations from the start of dialysis and higher machine BFR in the first week of dialysis are associated with decreased AVF survival.