Vascular access for hemodialysis: 2004 and beyond

Development and validation of a risk score to prioritize patients for evaluation of access stenosis

Background

Access flow dysfunction, often associated with stenosis, is a common problem in hemodialysis access and may result in progression to thrombosis. Timely identification of accesses in need of evaluation is critical to preserving a functioning access. We hypothesized that a risk score using measurements obtained from the Vasc‐Alert surveillance device could be used to predict subsequent interventions.

Methods

Measurement of five factors over the preceding 28 days from 1.46 million hemodialysis treatments (6163 patients) were used to develop a score associated with interventions over the subsequent 60 days. The score was validated in a separate dataset of 298,620 treatments (2641 patients).

Results

Interventions in arteriovenous fistulae (AVF; n = 4125) were much more common in those with the highest score (36.2%) than in those with the lowest score (11.0). The score also was strongly associated with interventions in patients with an arteriovenous graft (AVG; n = 2,038; 43.2% vs. 21.1%). There was excellent agreement in the Validation datasets for AVF (OR = 2.67 comparing the highest to lowest score) and good agreement for AVG (OR = 1.92).

Conclusions

This simple risk score based on surveillance data may be useful for prioritizing patients for physical examination and potentially early referral for intervention.

Influence of intradialytic systolic blood pressure changes on arteriovenous access thrombosis in maintenance hemodialysis patients

BACKGROUND

Arteriovenous access (AV) thrombosis is an important and preventable problem amongst chronic hemodialysis (HD) patients. Systolic blood pressure (SBP) fluctuation relates to higher cardiovascular mortality amongst these patients. We proposed there is a close relation between SBP changes and arteriovenous (AV) access thrombosis. We also determined other risk factors and biochemical parameters related to AV access failure.

METHODS

50 HD patients with thrombosis and 50 HD patients without thrombosis were included in the study. Odds ratios and 95% confidence intervals were estimated with multivariate-adjusted logistic regression models to determine the association between potential thrombosis-related risk factors and thrombosis risk.

RESULTS

Elder adults, women, and patients with AV grafts, lower intradialytic SBP and higher SBP variations during HD sessions had higher incidence of AV access thrombosis. AV access infection and decreased blood flow (BF) velocity were associated with an increased incidence of thrombotic events, whereas the use of anti-thrombotic agents was associated with a decreased incidence of thrombotic events. Further, anaemia, hypoalbuminemia, hyperlipidemia, and impaired mineral metabolism parameters were also found to be associated with AV access thrombosis.

CONCLUSIONS

Close monitoring and management of intradialytic hypotension and SBP fluctuation in every HD session are important. Some important and novel modifiable risk factors related to AV access thrombosis were identified in this study (eg, AV access infection, decreased BF and abnormal biochemical parameters, etc). Earlier surveillance and modification of these risk factors is crucial to prevent AV access failure in HD patients.

Sentinel vascular access monitoring after endovascular intervention predicts access outcome

BACKGROUND AND OBJECTIVES

The vascular access pressure ratio test identifies dialysis vascular access dysfunction when three consecutive vascular access pressure ratios are >0.55. We tested whether the magnitude of the decline in vascular access pressure ratio 1-week post-intervention could alert of subsequent access failure.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

The retrospective study included all vascular access procedures at one institution from March 2014 to June 2016. Data included demographics, comorbidities, vascular access features, %ΔVAPR = ((Pre-Post)/Pre] × 100% assessed within the first 2 weeks post-percutaneous transluminal balloon angioplasty, time-to-next procedure, and patency. The log-rank test compared the area under the curve, receiver operating curve, Kaplan-Meier arteriovenous graft and arteriovenous fistula survival curves. A multivariable Cox proportional hazard (CP) model was used to determine the association of %ΔVAPR with access patency.

RESULTS

Analysis of 138 subjects (females 51%; Black 87%) included 64 arteriovenous fistulas with 104 angioplasties and 74 arteriovenous grafts with 134 angioplasties. The area under the receiver operating characteristic curve for fistula failure at 3 months was 0.59, with optimal screening characteristics of 33.3%, sensitivity of 56.1%, and specificity of 63.2%. Arteriovenous fistula with <33.3% decline compared to >33.3% required earlier subsequent procedure (136 vs 231 days), lower survival on Kaplan-Meier analysis (P = 0.01), and twofold greater risk of failure (P = .006). Area under the receiver operating characteristic for arteriovenous graft failure at 3 months had a sensitivity of 52.3% and specificity of 67.4%. Arteriovenous graft with a post-intervention vascular access pressure ratio decline of <28.8% also required earlier subsequent procedure (144 vs 189 days), lower survival on Kaplan-Meier (P = 0.04), and a 59% higher risk for failure. The area under the receiver operating characteristic curve for combined access failure (arteriovenous fistula + arteriovenous graft) at 3 months had an optimal cut-point value of 31.2%, a sensitivity of 54.6%, and a specificity of 63.1%. Access with a <31.2% drop had a 62% increase in the risk of failure (hazard ratio 1.62; confidence interval 1.16, 2.27; P = 0.005).

CONCLUSION

The magnitude of post-intervention reduction in vascular access pressure ratio provides a novel predictive measure of access outcomes.

Interventions for treating central venous haemodialysis catheter malfunction

BACKGROUND

Adequate haemodialysis (HD) in people with end-stage kidney disease (ESKD) is reliant upon establishment of vascular access, which may consist of arteriovenous fistula, arteriovenous graft, or central venous catheters (CVC). Although discouraged due to high rates of infectious and thrombotic complications as well as technical issues that limit their life span, CVC have the significant advantage of being immediately usable and are the only means of vascular access in a significant number of patients. Previous studies have established the role of thrombolytic agents (TLA) in the prevention of catheter malfunction. Systematic review of different thrombolytic agents has also identified their utility in restoration of catheter patency following catheter malfunction. To date the use and efficacy of fibrin sheath stripping and catheter exchange have not been evaluated against thrombolytic agents.

OBJECTIVES

This review aimed to evaluate the benefits and harms of TLA, preparations, doses and administration as well as fibrin-sheath stripping, over-the-wire catheter exchange or any other intervention proposed for management of tunnelled CVC malfunction in patients with ESKD on HD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register up to 17 August 2017 through contact with the Information Specialist using search terms relevant to this review. Studies in the Specialised Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all studies conducted in people with ESKD who rely on tunnelled CVC for either initiation or maintenance of HD access and who require restoration of catheter patency following late-onset catheter malfunction and evaluated the role of TLA, fibrin sheath stripping or over-the-wire catheter exchange to restore catheter function. The primary outcome was be restoration of line patency defined as ≥ 300 mL/min or adequate to complete a HD session or as defined by the study authors. Secondary outcomes included dialysis adequacy and adverse outcomes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed retrieved studies to determine which studies satisfy the inclusion criteria and carried out data extraction. Included studies were assessed for risk of bias. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using GRADE.

MAIN RESULTS

Our search strategy identified 8 studies (580 participants) as eligible for inclusion in this review. Interventions included: thrombolytic therapy versus placebo (1 study); low versus high dose thrombolytic therapy (1); alteplase versus urokinase (1); short versus long thrombolytic dwell (1); thrombolytic therapy versus percutaneous fibrin sheath stripping (1); fibrin sheath stripping versus over-the-wire catheter exchange (1); and over-the-wire catheter exchange versus exchange with and without angioplasty sheath disruption (1). No two studies compared the same interventions. Most studies had a high risk of bias due to poor study design, broad inclusion criteria, low patient numbers and industry involvement.Based on low certainty evidence, thrombolytic therapy may restore catheter function when compared to placebo (149 participants: RR 4.05, 95% CI 1.42 to 11.56) but there is no data available to suggest an optimal dose or administration method. The certainty of this evidence is reduced due to the fact that it is based on only a single study with wide confidence limits, high risk of bias and imprecision in the estimates of adverse events (149 participants: RR 2.03, 95% CI 0.38 to 10.73).Based on the available evidence, physical disruption of a fibrin sheath using interventional radiology techniques appears to be equally efficacious as the use of a pharmaceutical thrombolytic agent for the immediate management of dysfunctional catheters (57 participants: RR 0.92, 95% CI 0.80 to 1.07).Catheter patency is poor following use of thrombolytic agents with studies reporting median catheter survival rates of 14 to 42 days and was reported to improve significantly by fibrin sheath stripping or catheter exchange (37 participants: MD -27.70 days, 95% CI -51.00 to -4.40). Catheter exchange was reported to be superior to sheath disruption with respect to catheter survival (30 participants: MD 213.00 days, 95% CI 205.70 to 220.30).There is insufficient evidence to suggest any specific intervention is superior in terms of ensuring either dialysis adequacy or reduced risk of adverse events.

AUTHORS' CONCLUSIONS

Thrombolysis, fibrin sheath disruption and over-the-wire catheter exchange are effective and appropriate therapies for immediately restoring catheter patency in dysfunctional cuffed and tunnelled HD catheters. On current data there is no evidence to support physical intervention over the use of pharmaceutical agents in the acute setting. Pharmacological interventions appear to have a bridging role and long-term catheter survival may be improved by fibrin sheath disruption and is probably superior following catheter exchange. There is no evidence favouring any of these approaches with respect to dialysis adequacy or risk of adverse events.The current review is limited by the small number of available studies with limited numbers of patients enrolled. Most of the studies included in this review were judged to have a high risk of bias and were potentially influenced by pharmaceutical industry involvement.Further research is required to adequately address the question of the most efficacious and clinically appropriate technique for HD catheter dysfunction.

Adequação de um sistema de hemodiálise em eqüinos

Realizou-se a adequação da técnica de hemodiálise com eqüinos, distribuídos em quatro grupos experimentais de seis animais cada. Os animais do grupo I foram submetidos a cateterismo central unilateral (grupo-controle); os do grupo II foram submetidos a cateterismo central unilateral com cateter duplo-lúmen e a uma sessão de hemodiálise de seis horas; os do grupo III a cateterismo central unilateral com cateter duplo-lúmen e duas sessões de hemodiálise de seis horas e os do grupo IV a cateterismo central bilateral com cateter monolúmen e a uma sessão de hemodiálise de seis horas. Empregaram-se xilazina 10% (0,4mg/kg) e acepromazina 2% (0,008mg/kg) via intravenosa para sedação. Foram utilizados dois hemodialisadores conectados em série, do tipo fibras ocas, baixo fluxo, membrana de polissulfona e área de 1,8m². O fluxo sangüíneo médio foi de 319,18±97,41ml/minuto, associado a um fluxo de dialisato de 500ml/min. A anticoagulação foi feita com heparina sódica em 100UI/kg para primming, repetida na dose de 53,86±18,61UI/kg/hora. Foram avaliados: tempo de coagulação, tempo de protrombina, tempo de tromboplastina parcial ativada e contagem plaquetária, e verificado trombocitopenia nos grupos dialisados. O melhor acesso vascular foi proporcionado pelo cateterismo unilateral com cateter lúmen-duplo (Grupos II e III), podendo a técnica de hemodiálise ser empregada na espécie eqüina, com dialisadores de alta eficiência, em sessão de seis horas de diálise.

Feasibility of trans-radial approach in percutaneous intervention for upper arm dialysis access

BACKGROUND

This retrospective study evaluated the feasibility and efficacy of trans-radial intervention for upper arm dialysis access.

METHODS

This study retrospectively reviewed 165 trans-radial interventions performed for upper arm dialysis access in 101 patients. Sixty-nine patients had arteriovenous graft (AVG), and 32 had arteriovenous fistula (AVF). Balloon angioplasty was performed in 66 stenotic dialysis accesses and 99 thrombosed dialysis accesses. Thrombosed dialysis access was further managed by additional balloon thrombectomy with or without urokinase injection.

RESULTS

Procedural time was 46.7 +/- 25.5 minutes. Anatomic and clinical success rates were 89.7% and 84.2%, respectively. The rate of complications, most of which involved lesion rupture with contrast-media extravasation and distal embolism, was 9.7%. Pretreatment stenosis was more severe (p = 0.01) and the prevalence of total occlusion was higher (p < 0.01) in the AVG group than the AVF group. The success rate and complication rate did not statistically differ (p = 0.59). Additionally, the thrombosed group had a lower success rate (p = 0.02), a higher complication rate (p < 0.01) and a longer procedural time (p < 0.01) than the stenotic group.

CONCLUSIONS

Comparison with previous studies employing the traditional approach reveals that trans-radial intervention has a comparable success rate, procedural time and complication rate for upper arm dialysis access. Therefore, trans-radial intervention is a safe and feasible technique for upper arm dialysis access.

Vascular access complications in long-term pediatric hemodialysis patients

Current data demonstrate pediatric patients who remain on hemodialysis (HD) therapy are more likely to be dialyzed via central venous catheters (CVCs) than arteriovenous grafts (AVGs) and fistulae (AVFs). We retrospectively compared complications and health-related quality of life (HRQOL) associated with different vascular access types at two large centers over a 1-year period. Patients included in the study were younger than 25 years of age, weighed >20 kg, and had received HD for at least 3 months. Thirty CVC patients and 21 AVG/AVF patients received a total of 2,393 and 3,506 HD treatments, respectively. The infectious complication rate was higher for CVC patients, who were hospitalized 3.7 days for each 100 HD treatments versus 0.2 days for AVG/AVF patients (p < 0.01). CVC patients also had a much higher rate of access revision, needing 2.7 hospital days every 100 HD treatments compared with 0.2 days for AVG/AVF patients (p < 0.01). HRQOL scores did not differ between groups. Thus, despite similar HRQOL, CVCs were associated with more complications and greater morbidity when compared with AVG/AVFs. These findings further emphasize the need to use AVG/AVFs as primary HD access for pediatric patients expected to receive a long course of maintenance HD.

Comorbidities do not influence primary fistula success in incident hemodialysis patients: a prospective study

BACKGROUND AND OBJECTIVES

Concern about primary fistula failure may contribute to the underuse of arteriovenous fistula. The objective of this study was to investigate the baseline clinical parameters associated with primary fistula success.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Consecutive incident patients who commenced dialysis during a 28-mo period in a regional renal program were studied. Data on patient-related variables and on surgical approach (e.g., whether the surgeons routinely assess vessel size during the operation) were collected. Primary fistula success was defined as an arteriovenous fistula that was able to afford successful dialysis for 3 h with blood pump speed of > or =300 ml/min for three consecutive sessions.

RESULTS

A total of 205 (69%) patients had an AVF attempted as their first vascular access. The overall primary success rate was 64% and was similar for radiocephalic and brachiocephalic fistula. Logistic regression was done separately for patients with the two types of fistula because of the presence of statistical interaction. For radiocephalic fistula, male gender was the only parameter associated with primary fistula success (odds ratio 3.57; P = 0.01). The presence of comorbidity was not significantly associated with primary fistula failure.

CONCLUSIONS

Despite significant patient comorbidity, there was a high primary fistula success rate among this incident hemodialysis cohort. Given that vessel size may be the ultimate determinant of fistula success, if surgeons assess vessel size perioperatively, then the presence of significant comorbidity might not preclude arteriovenous fistula from being attempted as the initial access.

Vascular Anastomosis Model: Relation Between Competency in a Laboratory-based Model and Surgical Competency

BACKGROUND

Previously, we presented a new, laboratory-based, vascular anastomosis model as a tool to objectively quantify surgical skill. The purpose of the present study was to determine the relation between the outcomes of vascular anastomosis in the laboratory and technical competency, when performing similar vascular anastomoses, in the operating room.

MATERIALS AND METHODS

Twenty-nine resident surgeons-in-training participated in the present study. All residents had at least one previous laboratory training session using the vascular anastomosis model. Then residents had to create a forearm arterio-venous bridge graft in the operating room (OR). Three measures were used to assess technical competency in the OR: completion time of the graft to vein anatomosis, leakage grade across the anastomosis, and the mini-objective structured assessment of technical skills (MOSAT) score. Similar outcomes obtained in the laboratory were used as predictors of OR outcomes. Significant predictors were identified using multiple linear regression and multiple ordinal logistic regression modelling.

RESULTS

Worse leakage in the laboratory predicted worse leakage in the OR, longer completion time and worse MOSAT score in the OR. Longer completion time in the laboratory was associated with longer OR completion time, but less leakage. Higher year of training and greater laboratory exposure were related to higher MOSAT score and shorter completion time in the OR, respectively.

CONCLUSIONS

Completion time and grade of anastomosis leakage measured in the laboratory were predictive of technical competency in the OR. The vascular anastomosis model may be useful for training in clinical surgery.

Late referral of patients with chronic kidney disease: no time to waste

The prevalence of patients with chronic kidney disease (CKD) in the US population is approximately 11%, and because of the increase in life expectancy and in diabetic nephropathy incidence, an exponential increase is predicted for the next decades. During the past decade, evidence that the progression of CKD can be attenuated by a multifactorial therapeutic approach has been increasing. However, a substantial percentage of patients with CKD will have progression to CKD stage V (ie, need for renal replacement therapy). Late referral of these patients (ie, <1 to 6 months before the start of renal replacement therapy) has been shown to be associated with higher mortality, morbidity, and costs. However, up to 64% of patients with CKD are still referred late. This review presents the available data on the epidemiology, causes, and consequences of late patient referral. Furthermore, it offers information to prevent late referral, improve CKD patient care, and change clinical practice.

ASDIN Clinical Case Focus: Cause for Inadequate Clearance: Hemodialysis Catheter Migration into the Coronary Sinus

Complications associated with central dialysis catheters prove to be an important source of morbidity that challenge patients and clinicians alike. While thrombosis, stenosis, and infection remain the most common threats to functioning central dialysis catheters, malposition of such devices may similarly result in serious consequences. Despite advanced techniques used to confirm initial catheter placement, the very nature of these catheters entails frequent manipulation for vascular access and therefore they may migrate after repeated use. When compared with the loss of patency and infection, complications involving malposition or migration may present in a more insidious fashion, such as a gradual decline in achievable blood flow rate or observed clearance over time. We describe a patient who acutely developed both clinical and biochemical evidence of inadequate clearance after several months of suboptimal catheter function. When the central dialysis catheter was examined fluoroscopically, it was found to have migrated into the coronary sinus.

Design of the Dialysis Access Consortium (DAC) Aggrenox Prevention Of Access Stenosis Trial

BACKGROUND

Surgically created arteriovenous (AV) grafts are the most common type of hemodialysis vascular access in the United States, but fail frequently due to the development of venous stenosis. The Dialysis Access Consortium (DAC) Aggrenox Prevention of Access Stenosis Trial tests the hypothesis that Aggrenox (containing dipyridamole and aspirin) can prevent stenosis and prolong survival of arteriovenous grafts.

METHODS

This is a multicenter, randomized, double-blind, placebo-controlled trial that will enroll 1056 subjects over four years with one-half year follow-up. Subjects undergoing placement of a new AV graft for hemodialysis are randomized to treatment with Aggrenox or placebo immediately following access surgery. The primary outcome is primary unassisted patency defined as the time from access placement until thrombosis or an access procedure carried out to maintain or restore patency. The major secondary outcome is cumulative access patency. Monthly access flow monitoring is incorporated in the study design to enhance detection of a hemodynamically significant access stenosis before it leads to thrombosis.

RESULTS

This paper describes the key issues in trial design, broadly including: 1) ethical issues surrounding the study of a clinical procedure that, although common, is no longer the clinical intervention of choice; 2) acceptable risk (bleeding) from the primary intervention; 3) inclusion of subjects already receiving a portion of the study intervention; 4) inclusion of subjects with incident rather than prevalent qualifying clinical conditions; 5) timing of the study intervention to balance safety and efficacy concerns; and 6) the selection of primary and secondary study endpoints.

CONCLUSIONS

This is the first, large, multicenter trial evaluating a pharmacologic approach to prevent AV graft stenosis and failure, an important and costly problem in this patient population. Numerous design issues were addressed in implementing the trial and these will form a roadmap for future trials in this area.

Hemodialysis for the non-nephrologist

Hemodialysis is now routinely provided to more than 300,000 patients in the United States. An epidemic of end-stage renal disease will nearly double this number by 2010. Patients undergoing chronic hemodialysis have high morbidity and mortality rates. Given these facts, most medical providers will be involved in the care of patients undergoing hemodialysis and it is thus important to have an understanding of the dialysis procedure and its attendant risks. This review discusses the basic physiology of the dialysis procedure and its associated complications.