Hemodialysis Access Surveillance Research Articles

The role of hemodialysis access duplex ultrasound for evaluation of patency and access surveillance.

The rise in prevalence of end stage renal disease (ESRD) and the impact on health care resulted in increasing focus on delivery of vascular access. Hemodialysis vascular access is the most common renal replacement therapy method. The vascular access types include arteriovenous fistula, arteriovenous graft, and tunneled central venous catheters. Vascular access function remains an important outcome measure with significant impact on morbidity and health care cost. The survival and quality of life of patients on hemodialysis is dependent on the adequacy of dialysis through proper vascular access. Early detection of failure to mature vascular access, stenosis, thrombosis, and aneurysm or pseudoaneurysm formation remains crucial. Ultrasound can help identify complications, even though ultrasound evaluation of the arteriovenous access is less well defined. Some published vascular access guidelines support ultrasound for detecting stenosis. The evolution of ultrasound has improved throughout the years, both multi parametric top-line systems and hand-held systems. Ultrasound evaluation is inexpensive, rapid, noninvasive, and repeatable, it is a powerful tool used for early diagnosis. The ultrasound image quality still depends on the skill of the operator. Careful attention to technical details is needed and avoidance of several diagnostic pitfalls is necessary. This review is focused on the role of ultrasound for hemodialysis access surveillance, evaluation of maturation, detection of access complications, and aid with cannulation.

Study of Anti-C1q Antibodies in Egyptian Systemic Lupus Erythematosus Patients.

Autoantibodies to complement are associated with various diseases. Anti-C1q antibodies are present in all patients with hypocomplementemic urticarial vasculitis, but also with varying prevalence in other conditions. Anti-C1q may interfere with the clearance of apoptotic cells, so influencing induction and expression of autoimmunity. The aim of this work is to study the relation between anti-C1q antibodies and systemic lupus erythematosus (SLE) and its manifestations including renal affection. The presence and levels of anti-C1q antibodies were investigated using enzyme-linked immunosorbent assay technique. The study included 70 Egyptian patients suffering from SLE and 18 healthy controls. They were 65 females and five males. Their age ranged from 12 to 48.5 years with a mean value of 27.4 ± 8.4. Anti-C1q antibodies were statistically significantly elevated in cases compared with controls being positive in 37.2% (mean 18.3 ± 27.1) in patients versus 11.1% (mean value 4.1 ± 3.5) in controls (P = 0. 03). Anti-C1q antibody-positive patients (n = 226) had significantly higher SLE Disease Activity Index (SLEDAI) (16.1 ± 9.9) compared to negative patients (n = 44) (SLEDAI = 8.1 ± 7.7) P = 0.000. Regarding renal affection, the presence of anti-C1q-positive antibodies was associated with proteinuria, P = 0.002. In conclusion, anti-C1q was more common in patients with SLE and disease activity. We confirmed a significant association of anti-C1q with renal involvement, independent of demographics and other serologies.

Effects of hemodialysis access surveillance on reducing risk of hemodialysis access thrombosis: A meta-analysis of randomized studies.

Vascular access thrombosis remains the Achilles Heel for many a hemodialysis patient. We performed a systematic review and meta-analysis to assess the impact of monitoring vascular access blood flow on prediction and prevention of vascular access thrombosis. We hypothesized that monitoring vascular access blood flow has a pivotal role in lowering the risk of thrombosis and subsequent access failure. We conducted a systematic review in PubMed and EMBASE databases to identify randomized studies that have assessed the effect of hemodialysis access surveillance on the risk of thrombosis. A random-effects model was used for the meta-analysis. Subgroup analysis was performed among patients with arterio-venous fistula (AV-fistulas) and those with arterio-venous graft (AV-grafts). Ten randomized studies were included in the meta-analysis. The total number of patients included in the analysis was 1430. On performing the random-effects model among the included studies, hemodialysis access surveillance was associated with better outcomes (risk ratio = 0.73, 95% confidence interval ranges from 0.55 to 0.98). The analysis of the AV-fistula group showed an estimated overall risk ratio of 0.55 (95% confidence interval ranges from 0.33 to 0.89) favoring access surveillance. However, in the AV-grafts group, the estimated overall risk ratio was 0.92 (95% confidence interval ranges from 0.65 to 1.29) showing no additional benefit for access surveillance. Hemodialysis access surveillance using access blood flow monitoring can reduce the risk of access thrombosis for patients with AV-fistulas, but this is not the case with AV-grafts.

Impact of a Structured Duplex Ultrasound Hemodialysis Access Surveillance Program on Access Intervention Rates

Purpose —To assess the impact of a structured duplex ultrasound hemodialysis access surveillance program on the frequency of diagnostic fistulograms and endovascular interventions. Methods —A structured ultrasound hemodialysis access surveillance program was implemented at our institution on March 1, 2010. The access ultrasound comprised the measurement of vessel diameter, velocity, and flow in the feeding artery, anastomosis, and at specific points along the outflow vein (2.5, 5.0, 7.5, and 10 cm beyond anastomosis) along with a waveform pattern in the ipsilateral axillary and internal jugular vein. In this retrospective multicenter study, we compared the frequency of diagnostic contrast fistulograms and endovascular interventions (angioplasty) performed from March 2010 to February 2011 (12 months) by using the implemented ultrasound access surveillance program (postsurveillance) to the preceding 12 month period (March 2009 to February 2010) where no ultrasound access surveillance program was used (pre-surveillance). Results —Within our hemodialysis program, there was an average of 119 active fistulae during the presurveillance period versus 141 in the postsurveillance period. There were no significant demographic differences in our study populations across the two time frames ( p > 0.05). In the presurveillance period, 59 diagnostic contrast fistulograms were performed, whereas 47 diagnostic contrast fistulograms were performed during the post surveillance period. Using a two-sample test for equality of proportions, we found there was a significant decrease in the proportion of diagnostic contrast fistulograms after implementation of an access ultrasound surveillance program ( p = 0.0114). Similarly, 81 endovascular interventions were performed during the presurveillance period, whereas a significantly decreased number of endovascular interventions (n = 50) were performed postsurveillance ( p < 0.0001). Conclusions —There was a significant decrease in the number of invasive diagnostic contrast fistulograms and endovascular interventions upon implementation of an ultrasound access surveillance program. Such a structured surveillance program has the potential to provide significant reduction in patient discomfort and to minimize unnecessary invasive endovascular procedures.

Monitoring Dialysis Arteriovenous Fistulae: It's in our Hands

Vascular access problems are a daily occurrence in hemodialysis units. Loss of patency of the vascular access limits hemodialysis delivery and may result in underdialysis that leads to increased morbidity and mortality. Despite the known superiority of autogenous fistulae over grafts, autogenous fistulae also suffer from frequent development of stenosis and subsequent thrombosis. International guidelines recommend programmes for detection of stenosis and consequent correction in an attempt to reduce the rate of thrombosis. Physical examination of autogenous fistulae has recently been revisited as an important element in the assessment of stenotic lesions. Prospective observational studies have consistently demonstrated that physical examination performed by trained physicians is an accurate method for the diagnosis of fistula stenosis and, therefore, should be part of all surveillance protocols of the vascular access. However, to optimize hemodialysis access surveillance, hemodialysis practitioners may need to improve their skills in performing physical examination. The purpose of this article is to review the basics and drawbacks of physical examination for dialysis arteriovenous fistulae and to provide the reader with its diagnostic accuracy in the detection of arteriovenous fistula dysfunction, based on current published literature.

Dysfunctional stenotic hemodialysis arteriovenous fistulae: Effect of percutaneous transluminal angioplasty

Purpose: To study effect of percutaneous transluminal balloon angioplasty (PTA) on dysfunctional stenotic arteriovenous fistulae (AVF). Methods: Between June 2008 to January 2010, 22 patients with dysfunctional stenotic hemodialysis native AVF for whom technically successful PTA were done, were enrolled in the study. AVF dysfunction was shown by a decrease in blood pump flow (Qb) below prescribed level (300-350 ml/min), a decrease in access blood flow rate (Qa) below 400 ml/min and a decrease in urea reduction rate (URR) below 65%. AVF stenoses were diagnosed by duplex ultrasound study and significant stenoses (more than 50% of luminal diameter) were treated by PTA. After PTA, measurements of Qb, Qa, and URR were done and were compared to pre- intervention levels. All AVF were kept on access surveillance program and primary patency rates were assessed at 1, 3, 6 and 12 months. Results: PTA was associated with improvement of AVF hemodynamics as shown by returning of Qb to the prescribed levels with a significant increase by mean of 76(± 26) ml/min (P<0.001) and a significant increase of Qa by mean of 407 (± 92) ml/min (P<0.001) compared to pre- intervention levels. Also PTA was associated with improvement of adequacy of dialysis as shown by a significant increase of URR by a mean of 24.6(± 6.1) % (P<0.001) compared to pre- intervention levels. Primary patency rates of AVF were 95.4%, 68.2 %, 45.4% and 22.7% at 1, 3,6 and 12 months, respectively. Also, primary patency rates were significantly superior in less severe stenoses compared to more severe stenoses with 6 months patency rate of 66.7% versus 20%, respectively (P=0.029). Conclusion: PTA is an effective and safe procedure in the treatment of dysfunctional stenotic haemodialysis native AVF. When successful, it improves AVF haemodynamics, adequacy of dialysis and primary patency rates at short and intermediate terms. Our findings also support the importance of hemodialysis access surveillance programs for early detection of AVF stenosis causing access dysfunction and the pre-emptive PTA which improves access survival

Hemodialysis access surveillance does not improve access outcomes

Hemodialysis access surveillance does not improve access outcomes

Comparison of Clinical Assessment With Ultrasound Flow for Hemodialysis Access Surveillance

Organized clinical assessment of hemodialysis access is as useful a surveillance tool as ultrasound flow measurements in preventing access thrombosis. Cohort analysis comparing a dialysis unit evaluated using ultrasound flow measurements with another unit evaluated clinically. University-affiliated community program with private and health maintenance organization dialysis units. One hundred patients in each unit were enrolled. Patients who were unavailable for follow-up or died within the first 30 days of enrollment were excluded from further analysis. Angiograms were obtained in the Transonics Doppler ultrasound system (Transonics Systems Inc, Ithaca, New York) cohort if graft flow was less than 600 mL/min, fistula flow was less than 450 mL/min, or flow decreased more than 25%, and in the clinical cohort if there was a change in the access appearance, change in the bruit, or a sharp increase in venous resistance. Primary and secondary patencies of the hemodialysis access were analyzed for each cohort. Subset analysis was obtained for synthetic grafts and native fistulas. Procedures were assessed for each cohort. The patients in the clinical cohort had similar primary patency (1199 days) as in the Transonics cohort (1162 days) (P = .92). Angiographic procedures were also similar, with 56% of all patients having none. The mean number of procedures was 0.56 per patient in the Transonics cohort and 0.48 in the clinical group (P = .48). An organized clinical assessment, using a formal tracking tool, is equal to ultrasound flow measurements as a surveillance method to prevent hemodialysis access thrombosis.

American Society of Diagnostic and Interventional Nephrology Section Editor: Stephen Ash: Thresholds for Significant Decrease in Hemodialysis Access Blood Flow

AbstractDuring hemodialysis access surveillance, referral for evaluation and correction of stenosis is based upon determination that a significant decrease in blood flow (Q) has occurred. However, criteria for determining when a decrease is statistically significant have not yet been established. In this study we established such criteria by analyzing Q variation with the glucose pump test (GPT). We took nine Q measurements in each of 25 patients (18 grafts, 7 fistulas) during three dialysis sessions within a 2‐week period (predialysis and during hours 1 and 3). We determined thresholds that define a significant percentage decrease in Q (ΔQ) for various p values. In order to confirm the general applicability of these thresholds, we computed the average within‐patient Q variation during the three sessions (computed as a coefficient of variation and referred to as short‐term variation). We then determined the relative influences of biological (true) variation and analytical error on short‐term variation. We found that ΔQ must be &gt; 33% to be significant at p &lt; 0.05, whereas the threshold is &gt; 17% for p &lt; 0.20. Measuring Q at uniform versus different times during the sessions did not significantly reduce these thresholds. We also found that biological variation was nearly as large as short‐term Q variation, whereas analytical error contributed minimally to short‐term variation. In conclusion, this study defines thresholds for a significant ΔQ that have wide application in determining access referral for evaluation and correction of stenosis. Selection of a particular threshold should consider the relative importance of avoiding thrombosis versus avoiding unnecessary procedures. If avoiding unnecessary procedures is a priority, then we recommend a threshold of &gt; 33%. These thresholds apply to other methods of measuring Q, provided analytical error is significantly less than biological variation.

Underestimation of access flow by ultrasound dilution flow measurements

For hemodialysis access surveillance, flow measurements are increasingly considered important because they identify accesses at risk of thrombosis. Usually these flow measurements are performed with the ultrasound dilution technique. In a previous patient study it was observed that the resulting flow values were systematically low as compared to magnetic resonance flow measurements, but a satisfactory explanation was lacking. In the present study, we will demonstrate by hemodynamic calculations and in vitro experiments that this discrepancy can be explained by a temporary reduction of the access flow rate, caused by the reversed needle configuration during ultrasound dilution flow measurements. In this configuration, blood is injected retrogressively at one needle and flow between the needles is increased, causing an increased dissipation of energy. The proposed explanation is subsequently confirmed in a patient with a loop graft, by measuring the blood velocity by Doppler ultrasound as a function of reversed dialyzer flow rate. Apart from the ultrasound dilution technique, these findings are applicable to other recently proposed methods for measuring access flow that employ the reversed needle configuration.