Determinants of native arteriovenous fistula blood flow

BACKGROUND: Determinants of native arteriovenous fistula (AVF) placement have been well studied. Little is known on whether these factors impact on subsequent blood flow (Qa) in the mature AVF. METHODS: Arteriovenous fistula Qa and cardiac index (CI) were determined by ultrasound dilution. Multiple linear regression was used to assess independent predictors of AVF Qa. RESULTS: Of the 148 patients available for the analysis, 68% were male, with 61% using a radiocephalic AVF. Aetiology of renal disease was: 38% glomerulonephritis (GN), 22% diabetes mellitus (DM), 9% hypertension/ischaemic (HTN) and 31% other. Thirty per cent had coronary artery disease (CAD), 10% cerebrovascular disease and 11% peripheral vascular disease (PVD). Median (iqr) Qa was 1185 mL/min (790-1650) and CI was 3.15 L/min per 1.73 m(2) (2.60-3.93). On univariable analysis, log CI (0.98, P < 0.001), age (-0.1 per 10 years, P = 0.002), access position (upper vs lower 0.26, P = 0.003, PVD (-0.35, P = 0.015), CAD (-0.25, P = 0.008), and primary renal disease (DM vs GN, -0.35, P = 0.003, HTN vs GN, -0.34, P = 0.04) were associated with Qa. On multivariable analysis, CI (0.84, P < 0.001), access position (upper vs lower, 0.17, P = 0.018) and primary renal disease (DM vs GN, -0.26, P = 0.005, and HTN vs GN, -0.26, P = 0.038) remained significant predictors of AVF Qa. CONCLUSION: Once established, CI, AVF position and primary renal disease (hypertension/ischaemic and diabetes) are the major determinants of AVF Qa while female gender, CAD, PVD and body mass index were not significant determinants of Qa in this cohort.     

Prediction of failure of native arteriovenous fistulas using 'on-line' fistula flow measurements

BACKGROUND: Measurement of blood flow within native arteriovenous fistula during haemodialysis is recommended to detect incipient fistula failure. In the present study the value of such flow measurements was assessed in a group of patients on maintenance haemodialysis, with access via native arteriovenous fistulas. METHODS: Flow was measured using the 'on-line' thermodilution technique, on three separate occasions, and correlated with subsequent fistula failure within 6 months. RESULTS: Of the 53 patients studied, there were six failures (three thromboses and three inadequate dialysis filtration rates). Flow rates in patients who progressed to fistula failure were significantly less than flow rates in patients whose fistulas did not fail (U = 13.0, P < 0.0003). Failure was no more common in one type of fistula than another (type fistula: F = 0.29, P = 0.88; flow predicting failure: F = 7.22, P = 0.010). Receiver operating characteristic (ROC) curve analyses confirmed flow measurement to be a useful predictor of fistula failure (area under ROC curve 0.91). The optimal threshold of 576 mL/min flow gave a sensitivity of 89% and a specificity of 81%. Measurement of access resistance was less useful in predicting failure (area under ROC curve 0.87). Measurement of fall in flow from the previous measurement was of no use (area under ROC curve 0.535). CONCLUSION: On-line thermodilution measurement of flow within established native arteriovenous fistula is useful in surveillance and early prediction of fistula failure. Fistula flow <576 mL/min may indicate incipient native fistula failure, and should prompt further investigation.     

Can blood flow surveillance and pre-emptive repair of subclinical stenosis prolong the useful life of arteriovenous fistulae? A randomized controlled study.

BACKGROUND: Stenosis is the main cause of arteriovenous fistula (AVF) failure. It is unclear, however, if surveillance for stenosis enhances AVF function and longevity and if there is an ideal time for intervention. METHODS: In a 5-year randomized, controlled, open trial we compared blood flow surveillance and pre-emptive repair of subclinical stenoses (one or both of angioplasty and open surgery) with standard monitoring and intervention based upon clinical criteria alone to determine if the former prolonged the longevity of mature forearm AVFs. Surveillance with blood pump flow (Qb) monitoring during dialysis sessions and quarterly shunt blood flow (Qa) or recirculation measurements identified 79 AVFs with angiographically proven, significant (>50%) stenosis. The AVFs were randomized to either a control group (intervention done in response to a decline in the delivered dialysis dose or thrombosis; n = 36) or to a pre-emptive treatment group (n = 43). To evaluate a possible relationship between outcome and haemodynamic status of the access, AVFs were divided into functional and failing subgroups, according to Qa values higher or lower than 350 ml/min or the absence or presence of recirculation. RESULTS: A Kaplan-Meier analysis showed that pre-emptive treatment reduced failure rate (P = 0.003) and the Cox hazards model identified treatment (P = 0.009) and higher baseline Qa (P = 0.001) as the only variables associated with favourable outcome. Primary patency rates were higher in treatment than in control AVFs in both functional (P = 0.021) and failing subgroups (P = 0.005). They were also higher in functional than in failing AVFs in both control (P<0.001) and treatment groups (P = 0.023). Access survival was significantly higher in pre-emptively treated than in control AVFs (P = 0.050), a higher post-intervention Qa being the only variable associated with improved access longevity (P = 0.044). Secondary patency rates were similar in pre-emptively treated and control AVFs in both functional (P = 0.059) and failing subgroups (P = 0.394). They were also similar in functional and failing AVFs in controls (P = 0.082), but were higher in pre-emptively treated functional AVFs than in pre-emptively treated failing AVFs (P = 0.033) or in the entire control group (P = 0.019). CONCLUSIONS: We provide evidence that active blood flow surveillance and pre-emptive repair of subclinical stenosis reduce the thrombosis rate and prolong the functional life of mature forearm AVFs. We also show that Qa is a crucial indicator of access patency and a Qa >350 ml/min portends a superior outcome with pre-emptive action in AVFs.     

Haemodialysis vascular access and fistula surveillance methods in The Netherlands.

INTRODUCTION: As the mean age of haemodialysis patients is increasing, fewer patients will have suitable blood vessels for the creation of a Brescia-Cimino fistula and an increased use of graft implants is to be expected. METHODS: To assess the change in vascular access and the use of surveillance techniques, all haemodialysis centres in The Netherlands received a questionnaire regarding the types of vascular accesses and surveillance techniques used in their department on 31 December, 1996. The results were related to a comparable study done in 1987, shown between brackets. RESULTS: The response of the haemodialysis staff was 96%, of the vascular surgeons this was 91%. Sixty-two per cent (70%) of the patients had Brescia-Cimino fistulas, 21% (13%) Polytetrafluoroethylene (PTFE) graft fistulas, 17% (17%) other vascular accesses. Scheduled surveillance for stenosis detection was done by recirculation measurements in 6%, venous pressure measurements in 31%, Duplex scanning in 11% and angiography in 11% of the centres. When access problems occurred, 79% of the physicians performed recirculation measurements, 38% venous pressure measurements, 79% Duplex scanning and 100% angiography. In 46% of the centres PTA was done occasionally, and in 46% routinely for the treatment of stenotic complications in arteriovenous fistulas. CONCLUSIONS: The use of PTFE grafts and other types of vascular accesses has increased at the expense of BC fistulas. Recirculation and venous pressure measurements are primarily done when problems occur and not according to a standard surveillance schedule. For visualization of failing fistulas, 79% of the centres uses Duplex ultrasound analysis and 100% angiography. The popularity of PTA has increased from 46 to 92% of the centres.     

Characters and influential factors of vascular remolding after native arteriovenous fistula

Objective To finding out the characters of vascular remolding after the establishment of native arteriovenous fistula on the wrist, and exploring the influential factors.MethodsDoppler ultrasound was used to monitor the diameter of cephalic vein, brachial artery, radial artery and ulnar artery at the time before the surgery and one day, one week, two weeks, four weeks and eight weeks after the surgery respectively. The tendency of the diameter change was analyzed. ResultsTwenty eight patients completed the whole monitor session, in which eleven were female. The average age of those patients was (53.68 ± 2.61) years old. Twelve of them were diabetic nephropathy. The diameters of all vessel were increased more rapidly at the first day than any other days after surgery(all P＜0.01). The patients were divided into two groups depending on whether diabetic nephropathy. No significant difference was found between the two groups on the tendency of diameter change in cephalic vein and brachial artery (all P ﹥ 0.05). However, the tendency of diameter change in radial artery and ulnar artery was statistically significant difference between the two groups (all P＜0.05). ConclusionsCephalic vein, brachial artery, radial artery and ulnar artery are all apparently dilated on the first day after the surgery. The vascular dilation and diameter increasing become much slower after the period, the diameter tend to be stable. The primary diseases may affect the tendency of the diameter change in radial artery as well as ulnar artery.     

How to design a randomized controlled trial

Randomized controlled trials are the ideal study design to evaluate the effectiveness of health-care interventions. The conduct of a clinical trial is a collaborative effort between participants, investigators and a range of health-care professionals involved both centrally and locally in the coordination and execution of the trial. In this article, the key steps that are required to design a randomized controlled trial are summarized.     

External dilator-assisted banding for high-flow hemodialysis arteriovenous fistula

Creation of arteriovenous fistula (AVF) may lead to left ventricle hypertrophy and predispose for development or worsening of heart failure. It was postulated to reduce access blood flow if exceeded 2?L/min or cardiac index was higher than 3.0?L/min/m². Numbers of techniques decreasing flow were described. The major disadvantage was the complexity of procedure and necessity of intraoperative flow measurement needed to establish desired flow. The technique of dilator-assisted banding with no endovascular catheterization is presented. After blunt dissection non absorbable thread was placed around vessel and tied over the dilator. Then the dilator was gently removed and blood flow was confirmed by palpation. We performed 12 banding procedures. Mean brachial blood flows were 3733.2?±?826.2?mL/min preoperatively and 1461.2?±?337.7?mL/min after surgery. Mean flow reduction was 2272.2?±?726.9?mL/min. The external dilator-assisted banding is a feasible method for vascular access flow reduction without necessity of endovascular catheterization.     

How to read a report of a randomized controlled trial

Proper evaluation of up‐to‐date clinical evidence is essential for the provision of optimal patient care. Randomized controlled trials (RCTs) are the ideal study type to investigate the benefit or harm of an intervention, such as a drug therapy. RCTs aims to avoid biased assessment of clinical interventions through the even distribution of both known and unknown factors that may influence outcomes. However, not all RCTs are well designed, conducted or reported. As such, the clinician needs to critically appraise RCTs in order to determine their strengths and weaknesses. This paper aims to explain how to approach critical appraisal, by highlighting and illustrating important questions that help determine the reliability of results from randomized trials.     

Obesity is not an obstacle for successful autogenous arteriovenous fistula creation in haemodialysis.

BACKGROUND: Obesity, which is often associated with diabetes, is increasingly encountered in the haemodialysed population, and this may produce difficulty in autogenous arteriovenous fistula creation. Prosthetic angioaccess or catheters, when used in place of autogenous fistulas, increase thrombotic and infectious complications in these already challenged patients. METHODS: This prospective study was undertaken to assess the feasibility of autogenous arteriovenous fistula creation in 71 obese patients (BMI 34.6 +/- 7.8). We performed a two-stage procedure, in which radio-cephalic fistula formation was followed by subcutaneous transposition of the venous component for safe and easy puncture. RESULTS: Fistulas suitable for puncture, having blood flows of 799 +/- 285 ml/min, and sufficient to perform adequate haemodialysis (Kt/V 1.24) were achieved in 85% of the patients. Primary patency rates were 65% and 59% at 6 and 12 months, respectively, and secondary patency rates were 83% both at 6 and 12 months. CONCLUSIONS: Obesity does not prevent successful autogenous arteriovenous fistula formation, and may protect forearm venous vessels from the iatrogenic damage that occurs before the onset of haemodialysis therapy.     

Excellent performance of one-stage brachial-basilic arteriovenous fistula.

BACKGROUND: According to the National Kidney Foundation-Dialysis Outcomes Quality Initiative (NKF-DOQI) and the European Guidelines, the first and second choice for vascular access for haemodialysis are the radial-cephalic and brachial-cephalic arteriovenous fistula (AVF). Autogenous fistulas have a longer functional lifetime, less thrombotic complications and a lower infection risk compared with prosthetic implants. If it is impossible to create a brachial-cephalic AVF or after failure, either a brachial-basilic (BB) or a prosthetic forearm loop AVF may be considered. To determine the outcome of BB-AVFs, we retrospectively surveyed the results of this type of vascular access. METHODS: All BB-AVF patient records over a 6 year period were subtracted from an academic hospital registry. Primary failure and primary, assisted primary and secondary patency rates were calculated with the Kaplan-Meier method. Sex, diabetes mellitus (DM), pre-operative duplex diameters, complications and interventions were recorded and correlated with the patency rates. RESULTS: A total of 31 BB-AVFs were created in a one-stage surgical procedure. Of the patients, 36% were male and 19% had DM. Only one patient had a primary failure, leaving 30 (97%) of the BB-AVFs functional for dialysis treatment. Four patients died within 1 year after the operation, one of them from a catheter sepsis. Primary, assisted primary and secondary patency rates after 1 year were, 58, 83 and 90%, respectively. Patient characteristics and pre-operative duplex parameters did not influence patency rates. CONCLUSION: The BB-AVF is an excellent third choice option for vascular access.     

Primary study in maturity status of native arteriovenous fistula on the wrist

Object To investigate the maturity status of the cephalic vein when the native arteriovenous fistula matures and set up indicators of a matured native arteriovenous fistula. Methods The diameter, flow rate and wall thickness of the cephalic vein were prospectively measured by Doppler ultrasound after the native fistula was created. Mature judgment was done by skilled nurses depending on their experience before the fistula was punctured. The ultrasound data was marked as proposed mature at the same time. After three times dialysis, if blood flow was fluent and complications such as prolonged bleeding time and hematoma were absent, fistula mature was confirmed. Results Thirty-one patients were admitted to the study, then fistula were matured. The average age of those patients was (52.93±3.21) years old. Thirteen patients were female. Twenty two fistula located on the left arm. Thirteen of the patients were diabetic nephropathy. The average diameter of cephalic vein was increased from (3.10±0.11) mm before surgery to (4.74±0.16) mm when the fistula was matured, though it was still smaller than 6 mm which K/DOQI guideline had recommended (P＜0.05). The average mature period was (57.10±3.21) days. The matured fistula had an average high flow rate of (569.76±48.34) ml/min and wall thickness of (0.95±0.04) mm. The one-side 95% credibility interval of the diameter, flow rate and wall thickness of cephalic vein was 4.44 mm, 486.37 ml/min and 0.67 mm, respectively. Conclusions The diameter of cephalic vein in a matured native arteriovenous fistula in our study was significantly smaller than 6 mm which K/DOQI guideline had recommended. The indicators of native arteriovenous fistula mature in our country may different from abroad.     

Serenoa repens extract for benign prostate hyperplasia: a randomized controlled trial

OBJECTIVE: To compare the effect of a Serenoa repens extract with placebo for symptoms of benign prostatic hyperplasia (BPH). PATIENTS AND METHODS: In a double-blind placebo-controlled randomized trial between January 1999 and March 2000, 100 men with symptoms of BPH, aged < 80 years, with a maximum urinary flow rate of 5-15 mL/s for a voiding volume of 150 mL, were randomly and equally allocated to 320 mg S. repens extract or placebo (paraffin oil). The main outcome measures were the International Prostate Symptom Score (IPSS), peak urinary flow rate, and the Rosen International Index of Erectile Function (IIEF) questionnaire. RESULTS: There was no significant difference between the treatments over the 12 weeks of the study in the IPSS, peak urinary flow rate or for the IIEF questionnaire. CONCLUSIONS: During the trial all participants had some improvement in their symptoms of BPH but there was no significant beneficial effect of this S. repens extract over placebo in this 12-week trial.     

Prospective randomized controlled trial of traditional laparoscopic cholecystectomy versus single-incision laparoscopic cholecystectomy: report of preliminary data

Background

This study presents preliminary data from a prospective randomized multicenter, single-blinded trial of single-incision laparoscopic cholecystectomy (SILC) versus standard laparoscopic cholecystectomy (4PLC).

Methods

Patients with symptomatic gallstones, polyps, or biliary dyskinesia (ejection fraction <30%) were randomized to SILC or 4PLC. Data included operative time, estimated blood loss, length of skin and fascial incisions, complications, pain, satisfaction and cosmetic scoring, and conversion.

Results

Operating room time was longer with SILC (n = 50) versus 4PLC (n = 33). No differences were seen in blood loss, complications, or pain scores. Body image scores and cosmetic scores at 1, 2, 4, and 12 weeks were significantly higher for SILC. Satisfaction scores, however, were similar.

Conclusions

Preliminary results from this prospective trial showed SILC to be safe compared with 4PLC although operative times were longer. Cosmetic scores were higher for SILS compared with 4PLC. Satisfaction scores were similar although both groups reported a significantly higher preference towards SILC.     

A randomized, controlled trial of aprotinin in neonates undergoing open-heart surgery

Background:  Neonates undergoing open-heart surgery are especially at risk for massive bleeding and pronounced inflammation. The efficacy of aprotinin, a serine protease inhibitor, at ameliorating these adverse effects of cardiopulmonary bypass has not been clearly demonstrated in neonates.
Methods:  Term neonates were enrolled and randomly assigned in a blinded fashion to receive saline (group P, placebo) or high-dose aprotinin (group A). Intraoperative management was standardized: surgeon, anesthesia, cardiopulmonary bypass and hemostasis therapy. Patients were admitted postoperatively to a pediatric cardiac intensive care unit. Primary outcome measure of efficacy was duration of the postoperative mechanical ventilation. Secondary outcome measures were total volume and units of blood products transfused intraoperatively and for 24 h after surgery, duration of chest tube in situ , and intensive care and hospital stays after surgery.
Results:  Twenty-six neonates were enrolled; 13 received aprotinin and 13 received placebo. The study was halted prematurely because of US Food and Drug Administation's concerns about aprotinin's safety. Baseline patient, surgery and cardiopulmonary bypass characteristics were similar between groups. No outcome variables differed between groups ( P  > 0.05). Duration of postoperative ventilation was 115 ± 139 h (group A); 126 ± 82 h (group P); P  = 0.29, and total blood product exposure was 8.2 ± 2.6 U (group A); 8.8 ± 1.4 U (group P); P  = 0.1. Postoperative blood creatinine values did not differ between groups. In-hospital mortality rate was 4%.
Conclusions:  Aprotinin was not shown to be efficacious in neonates undergoing open-heart surgery. It is unclear whether adult aprotinin safety data are relevant to neonates undergoing open-heart surgery.     

A randomized controlled trial of immunosuppression conversion for the treatment of chronic allograft nephropathy.

BACKGROUND: This study was conducted to assess the effect of immunosuppression conversion on progression of chronic allograft nephropathy (CAN). METHODS: Forty-two cyclosporin-treated renal transplant recipients were studied. Patients were included if they had a negatively sloping reciprocal of creatinine vs time (ROCT) plot for >6 months and biopsy-proven CAN. Patients were excluded if they had previously been treated with tacrolimus/mycophenolate mofetil (MMF) or their serum creatinine was >400 micromol/l. Subjects were randomly treated with either: (A) MMF/reduced dose cyclosporin [MMF for azathioprine 0.5-1.0 g bd; cyclosporin trough level (C(0)): 75-100 ng/ml]; (B) tacrolimus for cyclosporin (C(0): 5-10 ng/ml); or (C) continuation of standard therapy. Glomerular filtration rate (GFR) was measured at baseline and after 6 months. RESULTS: Two patients started dialysis within 6 months (one each from groups A and B). One patient in group A was intolerant of MMF, six others reported gastrointestinal symptoms and three developed anaemia. Cyclosporin dose was reduced by 24% [interquartile range (IQR): 14-27%] in group A [end-of-study C(0): 99 ng/ml (IQR: 90-113 ng/ml)]. In group B, the end-of-study tacrolimus C(0) was 7 ng/ml (5-9 ng/ml). The end-of-study cyclosporin C(0) in group C was 163 ng/ml (145-215 ng/ml). Comparison of ROCT slopes before and after intervention revealed a treatment advantage for group A (P<0.05). The GFR analysis was supportive (P = 0.05). When patients with GFR <20 ml/min/1.73 m(2) at enrollment were excluded from the analysis, the treatment advantage for group A reached statistical significance (n = 27, P<0.05). CONCLUSIONS: MMF/reduced dose cyclosporin is superior to tacrolimus-for-cyclosporin and standard dose cyclosporin in patients with CAN, at least in the short term. The cyclosporin dose reduction component is likely to be of particular importance. Other findings suggest that early intervention is beneficial.