GIT (Glucose Infusion Test): Polycentric Evaluation of a New Test for Vascular Access Recirculation

Glucose infusion test: A new screening test for vascular access recirculation

There is a need for studies to establish a specific access recirculation (AR) threshold for screening arteriovenous fistula (AVF) stenosis in hemodialysis patients. This study was to assess the validity of AR against duplex doppler ultrasound in detecting AVF stenosis in hemodialysis patients. This cross-sectional study recruited chronic hemodialysis patients with AVF installment of at least three months. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), Youden’s index, and area under the curve (AUC) were calculated to establish AR thresholds for the screening of AVF stenosis<50% and AVF stenosis≥50%. The sample included 324 hemodialysis patients (193 non-stenosis, 48 stenosis<50%, and 83 stenosis≥50%). Hemodialysis patients with AVF stenosis≥50% had the highest AR (10.45±14.03%). AR was not valid in screening for AVF stenosis<50%. When screening for AVF stenosis≥50%, AR threshold of ≥4% or 5% provided optimal Youden indexes. AR threshold of 4% was found a sensitivity of 72.3%, a specificity of 46.9%, PPV of 31.9%, and NPV of 83.1%. AR threshold of 5% found a sensitivity of 60.2%, a specificity of 58.9%, PPV of 33.6%, and NPV of 81.1%. Both thresholds displayed AUC of 0.60 (95%CI 0.54–0.65, p<0.01). AR of 4% should be used for screening stenosis≥50% in hemodialysis patients.

BackgroundThe presence of arterio-venous (A-V) fistula recirculation among hemodialysis (HD) patients markedly decrease adequacy of dialysis.ObjectivesThe present article summarize some of observations about clinical significance, causes, the most common techniques for measurement, and main source of pitfall in calculation of access recirculation.Materials and MethodsA variety of literature sources such as PubMed, Current Content, Scopus, Embase, and Iranmedex; with key words such as inadequate dialysis and arterio-venous fistula access recirculation were used to collect current data. Manuscripts published in English language as full-text articles or as abstract form were included in our review study.ResultsAny access recirculation among HD patients should be considered abnormal and if it presents prompt investigation should be performed for its causes. There are two most common techniques for accurate assessment of access recirculation: Urea (or chemical) and nonurea-based method by ultrasound dilution technique. The most common causes of access recirculation are the presence of high-grade venous stenosis, inadequate arterial blood flow rate, close proximity, or misdirection of arterial and venous needles placement by HD staff especially in new vascular accesses due to a lack of familiarity with the access anatomy.ConclusionsThe presence of access recirculation among HD patients can lead to significant inadequate dialysis thereby resulting in reducing the survival of these patients. Therefore, periodic assessment of access recirculation should be performed in HD wards.

Vascular catheter use for dialysis remains highly prevalent, however, it is frequently adversely affected by access recirculation (AR). We previously reported the utility of effective ionic dialysance (EID)/blood flow rate (Qb) ratio in identifying significant (>5%) AR in arteriovenous (AV) fistulas (Mohan et al ASAIO J 56:427-433, 2010). We present data from 58 patients, receiving hemodialysis via venous catheters (85% tunneled cuffed catheters) who underwent intermittent monitoring for AR with the saline dilution technique (Transonic HD02 monitor) and had EID and Qb measurements from Diascan biosensor in the Gambro Phoenix dialysis machine available. Among the 193 hemodialysis sessions studied, 74 instances of significant access recirculation (sAR) were identified. A higher incidence of sAR occurred with temporary catheters and catheters in the femoral vein. We report a significant correlation between the EID/Qb ratio and AR in addition to demonstrating the predictive utility of the ratio for identifying dysfunction catheters with sAR (area under the receiver operator characteristic curve of 0.86 with a sensitivity of 79% and a specificity of 76% at an EID/Qb ratio of ≤ 0.60). Our data demonstrate the utility of the EID/Qb ratio as an indicator of sAR in dialysis catheters albeit at a different threshold than that seen with AV fistulae.

Formation and Spontaneous Closure of an Arteriovenous Fistula After Transvenous Pacemaker Placement

The arteriovenous (AV) fistula is the optimal vascular access for chronic haemodialysis (HD) patients. The Dialysis Outcomes and Practice Patterns Study (DOPPS II) reported a high use of central venous (CV) catheters for HD in Canadian centres. We studied factors influencing the choice of access in a prevalent HD population at a Canadian centre. This was a cross-sectional study of all HD patients at the Ottawa Hospital (Ottawa, Canada). Demographic information, the type of HD vascular access used and the factors influencing access choice were obtained from medical records. Nephrologists at the Ottawa Hospital were surveyed to identify attitudes that might influence the choice of HD access. In the survey of nephrologists (n = 17), there was 100% agreement that the AV fistula is the optimal HD access. In 599 prevalent chronic HD patients, AV fistulae were used in 58.0% (n = 347), CV catheters in 39.7% (n = 238) and only 2.3% had AV grafts (n = 14). By multivariate logistic regression, female gender, peripheral vascular disease and shorter duration of HD were independent predictors of CV catheter use. Of the patients with CV catheters, 68.9% had vascular factors or medical contraindications that precluded AV fistula creation. System/resource limitations influenced choice of access in only 19.3% of patients with CV catheters, although these factors were more important in patients within the first 6 months of HD initiation. The relatively high prevalence of CV catheter use at our HD centre is due mainly to patient-specific factors (e.g. unsuitable vessels or medical co-morbidities), rather than resource limitations or physician attitudes. Target setting for AV fistula use requires consideration of these factors as well as the effect of HD duration.

Background: Assessment of access recirculation (AR) is crucial to dialysis efficiency and there is thus a need for a method yielding a highly accurate, fast, easy and economical measurement that can be applied in any dialysis clinic. Non-urea based dilutional methods are more accurate than urea based methods and avoid problems with cardiopulmonary recirculation, but they require expensive specialized devices, which limit their applicability. Patients and Methods: We used simple dilutional method of AR based on the determination of serum potassium [K+] in two samples. A prospective study was performed in a Dialysis Unit at El Sahel Teaching hospital, Cairo, on End stage kidney disease patients on regular Hemodialysis through a functioning Arterio-venous fistula. Results: Access recirculation was found in 42% of studied patients. There were Highly Significant positive correlation between access recirculation, pre / post dialysis blood urea, basal k, and parathyroid hormone level. In addition, there were highly significant negative correlation between AR, Urea reduction ratio and KT/V. Conclusion and Recommendations: Potassium dilution method is one of the most simple, specific, and economical way to measure access recirculation and can easily be performed in any dialysis unit. We recommend more research should be done about hemodialysis adequacy, access recirculation and how to improve it.

There is a belief that there should be a minimum of 5 cm between two cannulating needles of an arteriovenous fistula. This study examined the effect of reduction of space between needles from 5 cm to 2.5 cm on access recirculation, the measurement of access blood flow rate (by indicator dilution technology), and dialysis efficiency (by effective ionic dialysance). Twelve patients were studied, with half having their dialysis needles placed 2.5 cm apart for five consecutive dialysis treatments followed by placing needles 5 cm apart for a further five consecutive treatments. The other half initiated with 5 cm followed by 2.5 cm distance for a similar number of treatments. All 120 dialyses had successful cannulations with access recirculation excluded. Access blood flow (Qa mL/min) measurement was attempted for each patient twice, with each of the two needle positions. The Qa with needles 2.5 cm apart was 1310.95 ± 525.7 mL/min (M ± SD, n = 21) and was 1001.0 ± 240.4 mL/min when 5 cm apart (n = 22) (p = 0.014). There was a correlation between these two sets of Qa values (r = 0.554; p = 0.011). The effective ionic dialysance values obtained with needles 2.5 cm or 5 cm apart were similar and correlated strongly (r = 0.71; p = 0.000). Hemodialysis treatments using arteriovenous fistulae and two needles as close as 2.5 cm apart are possible without access recirculation and impairment of clearance. Indicator dilution access blood flow measurements are not recommended under these circumstances.

Objective: The arterial needle placement in arteriovenous fistula (AVF) can either be antegrade (in the direction of blood flow or pointing towards the heart) or retrograde (against the direction of blood flow) while venous needle placement should always be in the same direction as the blood flow. This study determined the effects of arterial needle placement in the arteriovenous fistula on dialysis adequacy of End-Stage Renal Disease (ESRD) patients undergoing maintenance hemodialysis in United Candelaria Doctors Hospital - Nephro Synergies Inc. (UCDHNSI) Hemodialysis Center. Methods: A randomized controlled trial design was used in the study. A total of 20 non-diabetic, non-cardiac patients on maintenance hemodialysis for more than 6 months were randomized either to the intervention group (patients’ AVF were cannulated in a retrograde manner) or the control group (patients’ AVF were cannulated in an antegrade manner). Urea reduction ratio (URR) and Kt/V as well as access recirculation percentage were used to determine dialysis adequacy. Pre-dialysis, in the first 30 minutes of dialysis initiation and post-dialysis blood samples were obtained in each patient in 6 succeeding hemodialysis considering dialyzer reuse up to fifth reuse. Means were compared by independent t-test. Results: The findings of the study revealed that the mean URR and Kt/V of the subjects cannulated in retrograde manner and antegrade manner were 69.35% and 1.45, and 74.65% and 1.70, respectively. The mean access recirculation percentage of the subjects was 4.65% in the intervention group and 3.02% in the control group. There was a significant difference on URR and Kt/V of the subjects using retrograde and antegrade arterial needle placement in 6 succeeding hemodialysis sessions. There was no significant difference on access recirculation percentage of the subjects using retrograde and antegrade arterial needle placement in 6 succeeding hemodialysis sessions. Conclusions: Antegrade arterial needle placement provides more adequate hemodialysis than retrograde arterial needle placement in terms of URR and Kt/V values among non-diabetic, non-cardiac patients undergoing maintenance hemodialysis in 6 succeeding hemodialysis sessions. The directions of the arterial needle either retrograde and antegrade did not have significant effects on access recirculation.

Background and Aims Vascular access (VA) type used at hemodialysis (HD) initiation varies greatly across countries and dialysis providers, and central venous catheters (CVC) usage is associated with poor survival. Since middle 2019, the Romanian Renal Registry (RRR) imposed compulsory reporting for VA. Therefore, we aimed to evaluate at a national level the VA at HD initiation and its impact on survival. Method We examined the outcome on September 30, 2022, in incident patients starting HD between January 1, 2020 and December 31, 2021. RRR records data on patient age, sex, primary kidney disease (PKD), history of kidney replacement therapy (KRT) and VA, date and cause of death. Results A total of 6153 patients (median age 65 (IQR 54, 72) years, 60% male) started HD in the study period. Glomerulonephritis, diabetic kidney disease (DKD) and tubulointerstitial disease were the main PKD (12, 11 and 9%); the diagnosis was unknown in almost half of the patients (47%). Only 15% of the patients started HD on arterio-venous fistula (AVF); CVC was used in most of the patients: 63% temporary and 22% tunnelled. As in the first 90 days of the study 1674 patients died (74%), recovered the kidney function (17%), received a kidney transplant (2%) or were lost to follow up (7%), the final cohort for survival analysis (i.e. patients that survived more than 90 days) included 4479 patients. The proportion of VA type at HD initiation was similar in this cohort: only 20% AVF, 58% temporary and 23% long-life CVC. A total of 664 (15%) patients died after the first 90 days. They were older, had more often DKD and more frequently started HD on CVC. Cardiovascular disease (56%) was the main cause of death, followed by infectious (14%), cancer (6%), neurological (5%) and gastroenterological (2%) causes. There were no differences in the causes of death between patients who started HD on AVF or CVC. The mean survival time for the entire cohort was 25.3 (95%CI, 25.0-25.6) months. Survivals at 6, 12 and 24 months were 93%, 88% and 80%. In univariate analysis, patients who started HD on AVF had a significantly better mean survival time than those starting on temporary or on tunnelled CVC: 26.6 (95%CI, 26.2-27.1) vs. 25.1 (95%CI, 24.8-25.5) and 24.6 (95%CI, 24.0-25.2) months. In the multivariate Cox proportional hazard model, higher age at HD initiation, DKD, and CVC as initial VA were significantly associated with a poorer survival (Table 1). We reexamined the VA at 6 months after HD initiation - on December 31, 2021, or at the last treatment recorded – in 5654 patients. At six months from HD initiation, 33% were using an AVF, 39% a tunnelled, and 28% a temporary CVC. Conclusion In this nationwide, registry-based study we observed a high rate of CVC usage (80%) among incident HD patients. Also, there was a low conversion from CVC to AVF, with only 33% of patients having a patent AVF six months after HD initiation. HD initiation on a CVC was independently associated with a higher mortality. Furthermore, close to a half of the studied patients had unknown PKD. Taken together, these data point to late nephrology referral of patients in stage 4 CKD, and deficient predialysis nephrology care. A national strategy should be implemented to improve CKD care, aiming to increase both the rate of AVF usage at HD, and the conversion from CVC to AVF in the six months.

Introduction: Vascular access for hemodialysis (HD) is essential for the patient. Even though Arteriovenous fistula (AVF) is the preferred access, in certain age groups, the central venous catheter (CVC) may provide advantages. This study aims to investigate the quality of life related to vascular access. Methods: Cross-sectional study including patients from a hospital, a home HD unit and a satellite hemodialysis center. Clinical data was collected from the patients, who went through a quality-of-life questionnaire SF12 and a Vascular Access Questionnaire (VAQ). Results: 91 patients participated, mostly male (70%), with a mean age of 68.9 ± 16.2 years. AVF was the current vascular access in 60.4%, the rest used a CVC. Home HD was performed in 12.1% of patients and 76% started it via CVC. Regarding patients who have had both AVF and CVC, 58% prefer AVF and only 26.5% of current CVC carriers would have a new AVF, mostly due to fear of pain (52%). Most people (72.5%) reported having received sufficient information, with no differences between both accesses. The SF12 results showed no differences between patients with AVF or CVC. Regarding the VAQ, patients with AVF were more satisfied with the social aspect (p = 0.036) and complications (p = 0.006). Conclusion: Patients with AVF had better outcomes than those using CVC regarding complications and social aspects. These differences are not attributable to a worse overall quality of life status of CVC patients. Most patients with CVCs refuse to go through a new AVF for fear of puncture pain.

Controversy remains as to whether initiating haemodialysis (HD) with a central venous catheter (CVC) and vascular access conversion are associated with the risk of morbidity and mortality in incident HD patients. At our dialysis centre, the vascular access strategy is to create an arteriovenous fistula (AVF) early and use the AVF to initiate HD. In emergency situations, HD is initiated with a CVC and subsequent conversion from a CVC to an AVF as soon as possible. The effects of early AVF conversion on hospitalization and mortality were analysed. At HD initiation, 35.42% used AVF, 15.63% used CVC with immature AVF and 48.96% used CVC, and all patients were able to convert from CVC to AVF within approximately 3 months. Compared to starting HD using an AVF, using a CVC was associated with access-related hospitalizations at 2 years, regardless of whether an AVF was created before (incidence rate ratio (IRR) = 3.02, 95% CI 0.89-10.24, p = 0.03) or after (IRR = 4.10, 95% CI 1.55-10.85, p < 0.01) HD initiation. The Kaplan-Meier method showed that the 2-year survival probability was not statistically significant between the three groups (log-rank χ2 = 0.165, p = 0.921). Multivariate Cox proportional hazards regression showed that starting HD with a CVC was not associated with mortality at 2 years (p > 0.05). In this cohort, initiating HD with a CVC was associated with more access-related hospitalizations. Under the impact of an early AVF conversion strategy, despite initiating HD with a CVC, subsequent conversion from a CVC to an AVF within approximately 3 months had no impact on all-cause mortality in incident HD patients.

Arteriovenous Fistulae as an Alternative to Central Venous Catheters for Delivery of Long-Term Home Parenteral Nutrition

The traditional method for measuring vascular access recirculation has been questioned. We have compared methods based on samples from the femoral artery, a peripheral vein, and a slow flow technique. Seventeen patients on high-flux haemodialysis with blood flow 355 +/- 42 ml/min were examined after 60 min of treatment. Using urea as the marker solute, recirculation was 0.0 +/- 1.8% (femoral artery), 6.7 +/- 2.7% (peripheral vein), and 4.7 +/- 1.6% (slow flow), and using creatinine 0.1 +/- 1.4% (femoral artery), 7.8 +/- 3.0% (peripheral vein) and 2.9 +/- 1.2 (slow flow). Access recirculation was non-existent among these patients when using the femoral artery sample: maximum 3.1%. In contrast, the traditional method (peripheral vein) produced values up to 13.5%. The observed differences can be explained by cardiopulmonary recirculation. Blood returning from the periphery mixes with blood returning from the dialyser, so that solute concentration will be less in femoral artery than in peripheral vein. In conclusion, neither the traditional method nor slow-flow techniques accurately quantify access recirculation. Cardiopulmonary recirculation must be considered in kinetic studies, including routine dialysis prescription, where samples should be taken at least 2 min after termination of dialysis.

This commentary critically examines key assumptions and recommendations in the 2006 Kidney Disease Outcomes Quality Initiative vascular access guidelines, and argues that several are not relevant to the contemporary United States hemodialysis population. First, the guidelines prefer arteriovenous fistulas (AVFs) over arteriovenous grafts (AVGs), on the basis of their superior secondary survival and lower frequency of interventions and infections. However, intent-to-treat analyses that incorporate the higher primary failure of AVFs, demonstrate equivalent secondary survival of both access types. Moreover, the lower rate of AVF versus AVG infections is counterbalanced by the higher rate of catheter-related bloodstream infections before AVF maturation. In addition, AVFs with assisted maturation (interventions before successful AVF use), which account for about 50% of new AVFs, are associated with inferior secondary patency compared with AVGs without intervention before successful use. Second, the guidelines posit lower access management costs for AVFs than AVGs. However, in patients who undergo AVF or AVG placement after starting dialysis with a central venous catheter (CVC), the overall cost of access management is actually higher in patients receiving an AVF. Third, the guidelines prefer forearm over upper arm AVFs. However, published data demonstrate superior maturation of upper arm versus forearm AVFs, likely explaining the progressive increase in upper arm AVFs in the United States. Fourth, AVFs are thought to fail primarily because of aggressive juxta-anastomotic stenosis. However, recent evidence suggests that many AVFs mature despite neointimal hyperplasia, and that suboptimal arterial vasodilation may be an equally important contributor to AVF nonmaturation. Finally, CVC use is believed to result in excess mortality in patients on hemodialysis. However, recent data suggest that CVC use is simply a surrogate marker of sicker patients who are more likely to die, rather than being a mediator of mortality.