Comparative Clinical Performances of Tunneled Central Venous Catheters versus Arterio-Venous Accesses in Patients Receiving High-Volume Hemodiafiltration: The Case for High-Flow DualCath, a Tunneled Two-Single-Lumen Silicone Catheter.

Tunneled central venous catheters (CVC) are mainly considered as a rescue vascular access option in dialysis but are still used on approximately one quarter of prevalent patients worldwide even though they are associated with poor performances and higher risks. STUDY DESIGN: in this retrospective single-center study, we aimed to report on the clinical performances achieved with high-flow tunneled CVCs (DualCath or DCath) and compared them with arteriovenous accesses (AVAs, e.g., AV fistula, AV graft, and Thomas Shunt) in a hospital-based dialysis unit. METHODS: Sixty-eight stage 5 chronic kidney disease dialysis-dependent patients (CKD5D) receiving high volume hemodiafiltration were followed-up with for 30 months. The study consisted of two phases: baseline cross-sectional and longitudinal follow-ups of key performance indicators. Clinical performances consisting of effective blood flow and blood volume, recirculation, urea and ionic Kt/V, total Kt, ultrafiltration volume, and percent reduction in ß2-M were measured monthly as part of quality control in our unit. RESULTS: At baseline, the effective blood flow using a DCath was close to 400 mL/min, similar to an AVA. Recirculation with a DCath (7%, 6-13%) was higher than with an AVA. The diffusive dialysis dose delivered with a DCath (spKt and eKt/V) and convective dialysis dose achieved with a DCath were slightly lower than those achieved with AVAs, but they were still much higher than is recommended by guidelines. The percent reduction in ß2-M achieved with a DCath was also 4 to 10% lower than that achieved with an AVA. On longitudinal follow-up, the main clinical performance indicators of DCaths (total Kt and total ultrafiltration volume, L/session) were maintained as very stable over time and close to those achieved with AVAs. CONCLUSIONS: As shown in this study, high-flow DualCath tunneled two-single-lumen silicone catheters may be used to deliver high volume hemodiafiltration in a reliable and consistent manner without compromising clinical performance. These results relied on the specific design of the two silicone cannulas and the strict adherence to best catheter practices.

Monthly reference change value of cardiac troponin in hemodialysis patients as a useful tool for long-term cardiovascular management.

PURPOSE OF RESEARCH: Circulating cardiac troponin (cTn) has been identified as a risk factor for cardiovascular and overall mortality in patients undergoing hemodialysis. However, its interpretation remains difficult due to the high prevalence of patients with cTn level beyond the 99th percentile. Determining the cTn reference change value (RCV) may help in assessing a clinically significant change of cTn during regular follow-up of patients. We aimed to determine the long-term RCV of cTn in such patients and to calculate the perdialytic reduction rate of cTn. DESIGN AND METHODS: To calculate RCV, high-sensitivity (hs)-cTnT (Roche), hs-cTnI (Abbott), and cTnI-ultra (Siemens) were determined every month before the midweek dialysis session over a 3-month period in 36 stable hemodialysis patients. cTn was also measured after the midweek dialysis session to calculate the cTn removal rate. RESULTS: The mean RCV (95% confidence interval) was 22% (18-26) for hs-cTnT versus 53% (34-73) for hs-cTnI versus 65% (45-84) for cTnI-ultra. Log-normal RCV (%) was -19/+25 for hs-cTnT, -33/+96 for hs-cTnI, and -39/+115 for cTnI-ultra. The index of individuality was <0.6 regardless of the cTn assay used. A significantly greater reduction rate was observed for hs-cTnT (48%) than for hs-cTnI (30%, p<0.001) and cTnI-ultra (29%, p<0.05). CONCLUSIONS: These results underline the need to use the RCV approach rather than cutoff points to identify the critical change in long-term serial cTn levels. In addition, RCV should be determined for each available assay due to significant differences between assays. Removal of cTn during hemodialysis sessions should also be considered if acute coronary syndrome is suspected during a session.

[Residual renal function in dialysis patients]. / Rôle de la fonction rénale résiduelle dans la balance sodée du dialysé: est-ce un bénéfice ou un risque?

Residual renal function (RRF) contributes to the achievement of treatment adequacy in CKD-5 patients. It may facilitate patients' acceptance of renal replacement therapy (RRT) in minimizing dietary and fluid restriction. It has been confirmed to improve dialysis patient outcomes. Attempts to preserve RKF in incident CKD-5 patients are still subject to controversies. In this review we analyze the role of RRT in dialysis patient. What are the positive and the beneficial effects of maintaining RRF? What are the negative and the risks of maintaining a RRF? At what expense the maintenance of RRF is achieved? Preservation of RRF is undoubtedly an interesting means to enhance the efficacy of renal replacement therapy and reduce dietary fluid restriction. However, maintainance of RRF should not be considered as a goal of dialysis adequacy in dialysis patients but rather a means of optimizing RRT. Further, preservation of RRF should be considered as a permanent trade-off between patient comfort and chronic fluid volume overload with its deleterious effects.

The role of mineral metabolism and inflammation on dialysis vascular access failure.

Thrombosis of arteriovenous fistula (AVF) is the leading cause of vascular access (VA) loss usually due to silent stenosis. Therefore, assessment of relevant risk factors of VA monitoring may provide insight into potential therapeutic targets for stenosis and thrombosis. The aim of this study was to evaluate the influence of cardiovascular risk factors (including inflammation and mineral metabolism dysfunctions) on the failure of internal AVF in HD patients. 128 HD patients with internal AVF were included in the study and followed up for two years. At baseline, VA morphology and function were followed by Doppler ultrasonography and serum albumin, prealbumine, C-reactive protein, orosomucoid, calcium, phosphorus, parathyroid hormone, bone-type alkaline phosphatase, osteoprotegerin and receptor activator of nuclear factor ê ê B ligand were measured. At baseline, 50 stenoses were detected but none of them required any intervention. Age and biological parameters did not significantly differ between patients with or without VA stenosis. Over the two year- follow up, VA thrombosis occurred in 19 patients. Preexisting stenosis of VA was present in 9/19 patients (47.3% of cases) (chi-square = 3.708, p = 0.0538). Despite the low rate of events, phosphorus [1.75 (0.95-2.77) vs 1.42 (0.47-3.22) mmol/L, p = 0.0416], Calcium x Phosphorus product [4.00 (2.00-5.90) vs 3.40 (1.10-6.80) mmol(2)/L(2), p = 0.0676] and parathyroid hormone [165.00 (1.00-944.00) vs 79.50 (1.00-846.60) ng/L, p = 0.0814) levels were higher in the 19 thrombotic patients whereas all other biological parameters did not significantly differ. These results, which confirm that VA thrombosis occurs more frequently upon preexisting stenosis, also demonstrate that mineral metabolism disorders, compared to inflammation, may contribute to VA dysfunction leading to thrombosis.

[Vascular access, an underestimated source of inflammation in dialysis patients]. / L'accès vasculaire, une cause d'inflammation sous-estimée chez l'hémodialysé.

The surveillance of inflammation in dialysis patient, by means of sensitive markers such as CRP, is strongly recommended in a continuous quality improvement treatment approach. Chronic inflammation being deleterious via several pathways including malnutrition, accelerated arteriosclerosis and beta 2M-amyloidosis, microinflammation must diagnosed and corrected as soon as possible in dialysis patients. Vascular access represents an underestimated source of inflammation in hemodialysis patients. In the absence of organic cause of inflammation, the vascular access should be always incriminated and meticulously investigated. Withdrawing the suspected prosthetic or unused material (PTFE or catheter) should be considered as the best way of correcting the inflammation and restoring the recombinant erythropoietin (EPO) activity in the dialysis patient.

[Extrarenal dialysis in end-stage renal disease]. / Suppléance extrarénale de l'insuffisance rénale chronique terminale.

Renal replacement therapy (RRT) has reached its plain maturity. RRT is an unavoidable and banal tool in the armamentorium in the treatment of end stage renal failure (ESRD). It relies on several practical modalities (hemodialysis, peritoneal dialysis and their variants) that permit to satisfy various patient's needs and to ensure the continuity of life support system. Substitution of certain renal endocrine functions (human recombinant erythropoietin, active vitamin D) has brought a new dimension to the treatment of ESRD in improving substantially the quality of life of these patients. Now, if the long-term outcomes confirm the high efficiency of the renal replacement therapies they also draw their limits bounded by the occurrence of a specific pathology of the "long term dialysis" patient. Such dialysis-related pathology is clearly the new challenge for the nephrologist in the XXIst century that should lead to a deep revision of the RRT concept. Optimal treatment of ESRD patients rely clearly on several options that may be used sequentially to solve specific complications and should be part of a complete management program including renal transplantation in patient non contraindicated.

Monitoring the microbial purity of the treated water and dialysate.

Dialysate purity has become a major concern in recent years since it has been proven that contamination of dialysate is able to induce the production of proinflammatory cytokines, putatively implicated in the development of dialysis related pathology. In order to reduce this risk, it is advised to use ultrapure dialysate as a new standard of dialysate purity. Ultrapure dialysate preparation may be easily achieved with modern water treatment technologies. The reliable production of ultrapure dialysate requires several prerequisites: use of ultrapure water, use of clean electrolytic concentrates, implementation of ultrafilters in the dialysate pathway to ensure cold sterilization of the fresh dialysate. The regular supply with such high-grade purity dialysate relies on predefined microbiological monitoring of the chain using adequate and sensitive methods, and hygienic handling including frequent disinfection to reduce the level of contamination and to prevent biofilm formation. Reliability of this process requires compliance with a very strict quality assurance process. In this paper, we summarized the principles of the dialysate purity monitoring and the criteria used for surveillance in order to establish good antimicrobial practices in dialysis.

[Dialock: results of a French multicenter study]. / Dialock: résultats de l'étude multicentrique française.

INTRODUCTION: By offering a rapid and convenient vascular access option for hemodialysis, permanent catheters are increasingly used in ESRD patients. Indeed, permanent catheters are associated with an increased risk for complications. Moreover, catheter bearing spoils the self body image and may alter the quality of life of dialysis patients. Implantable port catheter device, recently introduce in dialysis, may offer an attractive option, able to reduce most of infectious risk and inconveniences of the permanent catheters. PATIENT AND MATERIAL: The Dialock (Biolink) device was evaluated in a multicenter French trial. Twelve dialysis facilities enrolling 51 ESRD patients (male 28, female 23, age 56 +/- 2 years) participated in this trial. Dialock devices were inserted in patients for whom a permanent venous catheter was indicated. The cumulative experience was 56.8 years-patient. The technical survival (intent to treat) of Dialock devices was 85% at two years. Blood flow were 299 +/- 7 ml/min. Dialysis adequacy was achieved in all patients without altering dialysis schedule (3 sessions per week, 240 +/- 30 min each). Dialysis dose (K(/Vdp) delivered was 1.3 +/- 0.2. Satisfaction of patients and nursing staff was achieved in 75% of cases. Normalized incidence of complications (events for 1000 patient-days) in the evaluation phase (II) were as follows: hematoma and/or small bleeding (2.1), bacteremia (1.1), device infection (0.2), skin necrosis (0.1). A significant reduction of the infection and hematoma incidence rate was noticed when heparin lock was substituted for an non hemorrhagic antithrombotic locking solution (fragmented heparin or sodium citrate). This observation tend to accreditate the hypothesis that port catheter infection occurs via a transluminal bacteria passage. CONCLUSION: The Dialock device, offers a new and comfortable hemodialysis vascular access for ESRD patients. Performances are in agreement with those needed to achieve adequate dialysis. The regular use of dual antithrombotic-antiseptic catheter locking solution seems to be necessary to prevent any bacterial contamination.

[Surveillance of permanent central venous access for hemodialysis]. / Surveillance et suivi des accès veineux centraux permanents pour hémodialyse.

Central venous catheters have emerged as a valuable alternative for permanent access in hemodialysis. Thanks to steady improvements of materials and design they have been successfully used as bridging solution until another vascular access became available or even long term solution for patients with limited or insuffisant vascular resources. Since the use of central venous catheters is affiliated with a higher dysfunction rate and morbidity, special attention is indicated. This should include regular surveillance, clinical examination and intervention using specific methods, bacteriological exams and regular dialysis quantification. Such a constant quality control followed by strict and adapted rules for catheter handling are essential necessities to reduce catheter-related complications and assure an adequate dialysis.

Urea as a marker of adequacy in hemodialysis: lesson from in vivo urea dynamics monitoring.

BACKGROUND: "Dialysis dose," a concept developed by Sargent and Gotch based on urea kinetic modeling, is a useful and recognized tool that is used to quantitate and optimize a dialysis-efficacy program. However, it has been shown that oversimplification of the "dialysis adequacy" concept to the Kt/V index might lead to dramatic underdialysis and subsequent deleterious consequences on morbidity and mortality of dialysis patients. With this perspective, the determination of Kt/V must be very cautious and rely on accurate measurement of postdialysis urea concentration and its use integrated as a tool in a quality-assurance process. METHODS: In this study, we analyzed urea dynamics by means of a blood side (ultrafiltrate) continuous online urea monitoring system interfaced with a two-pool model hosted in a microcomputer. The study was designed to provide instantaneous dialysis performances (body and dialyzer clearances, dialyzer mass transfer coefficient) and to determine the in vivo functional permeability characteristics of the patient [intercompartment urea mass transfer coefficient (Kc)]. Thirteen end-stage renal disease patients (age 54 +/- 16 years; 12 male and 1 female) were studied during nine consecutive dialysis sessions (3 weeks). RESULTS: Urea kinetics obtained from the urea monitoring system fitted closely the urea kinetic modeling prediction, confirming the validity of the double-pool model structure. Effective in vivo urea mass transfer coefficient averaged 912 +/- 235 mL/min/1.73 m2, a value close to those reported with more invasive methods. Large variations ranging from 363 to 1249 mL/min were observed among patients, confirming very large interindividual patient permeability differences. Interestingly, the urea mass transfer coefficient was inversely correlated with the postdialysis rebound values. Intraindividual variations were also noted as a function of time denoting functional changes in urea mass transfer coefficient values. The urea distribution volume was 38.1 +/- 7, 8 L (53 +/- 8% body weight). V1 referring to the extracellular volume and V2 to the intracellular volume were 9 +/- 2 L (13 +/- 2% body weight) and 29.2 +/- 6.6 L (41 +/- 1.3% body wt), respectively. The extracellular/intracellular volume ratio was 0.31 (approximately one third) and was not as usually defined by the paradigm 1/2 ratio. CONCLUSION: Online double-pool urea kinetic modeling gave a new insight in urea kinetic modeling approach. Urea dynamics fit perfectly a double-compartment model structure. Accessible extracellular volume to hemodialysis is smaller than expected. The in vivo urea mass transfer coefficient must be considered as an individual and variable characteristic of ESRD patients that should be taken into consideration when prescribing the hemodialysis schedule.

Temporary vascular access for extracorporeal therapies.

Central venous catheters provide at the present time the basic and ideal method to perform acute extracorporeal blood purification. Rapid launch of extracorporeal therapy is indicated in two situations: first, renal conditions presenting as a recognized acute organic renal failure (ARF) and acute decompensation of end stage renal disease (ESRD) without permanent vascular access; second, non-renal conditions presenting as urgent clinical situations requiring isolated ultrafiltration for chronic congestive heart failure, plasmapheresis or selective immunoadsorption for immune diseases, cytapheresis for hematological disease, and selective detoxification for certain types of poisoning. Central venous catheters are classified into 2 categories according to the duration of use: temporary catheter (less than 90 days) and permanent catheter (more than 90 days). A temporary catheter, including rigid (polyethylene, teflon) and semirigid (polyurethane) material, is indicated in emergency situations and for short-term use. A permanent catheter, made usually of soft silicone rubber with a subcutaneous anchoring system, has a subcutaneous tunnel and is indicated in medium and long-term use. Catheter design has benefited greatly from technical advances and material hemocompatability. However, catheter-related morbidity still remains high and is associated with an unacceptable incidence rate of infection and/or vein thrombosis. This article covers our present knowledge regarding catheter indications, technical aspects of catheter insertion and care, functional limitation of central venous catheters, and catheter-related complications. It is also our intent to provide the reader with optimal indication and catheter care in order to prevent and reduce the burden of catheter-related morbidity.

Intradialytic glucose infusion increases polysulphone membrane permeability and post-dilutional haemodiafiltration performances.

INTRODUCTION: During real-time monitoring of the ultrafiltration coefficient (Kuf) in haemodiafiltration (HDF), it was noticed that the ultrafiltration performance of polysulphone membrane dialysers increased when hypertonic glucose (D50%) was administered through the venous blood return. METHODS: This observation was explored in six non-diabetic chronic dialysis patients during 48 HDF sessions using 1.8 m(2) polysulphone membrane dialysers. In all six patients, 24 sessions were performed with glucose supplementation (as a continuous D50% (500 g/l) infusion at 40 ml/h) and 24 sessions without supplementation. RESULTS: Glucose supplementation led to a marked increase in Kuf from 22.8+/-2.2 (without D50%, n=24) to 32. 1+/-3.9 ml/h/mmHg (with D50%, n=24) (P<0.0001). An increase in percentage reduction ratios for urea and creatinine were also consistently observed during the sessions with glucose administration (from respective mean values of 75+/-5 and 68+/-4% to 79+/-4 and 74+/-10%). Mean double-pool Kt/V, calculated from serum urea concentrations, rose from 1.65+/-0.24 (n=24) to 1.86+/-0.24 (n=24) (P<0.005). Similar results were observed in a subgroup of 18 HDF sessions (nine with glucose and nine without) monitored with an on-line urea sensor of spent dialysate. No detrimental effects were induced at any time. CONCLUSIONS: We conclude that intravenous glucose administration during high-flux HDF using polysulphone membranes increases significantly both ultrafiltration capacity and dialysis dose delivery.

Imbalance of oxidants and antioxidants in haemodialysis patients.

Dialysis-related pathology (DRP) observed in long-term haemodialysis patients is increasingly reported. Among DRP manifestations, cardiovascular disease is the most frequent, being the first cause of mortality in haemodialysis patients. Alterations in lipid metabolism and oxidative stress are recognised as major risk factors that could be prevented or reduced by optimal therapy. In order to evaluate the rationale for preventive intervention against oxidative damage we review the factors that are implied and may be responsible for the imbalance between prooxidative and antioxidative mechanisms in haemodialysis patients. Oxidative stress resulting from this imbalance is responsible for increasing stress markers and enhancing susceptibility to LDL oxidation. Factors implied in this prooxidative state belong to four groups: (1) uremia and comorbid status of the end stage renal disease (ESRD) patient; (2) losses of antioxidant substances via the dialysis; (3) haemoincompatibility of the dialysis system; (4) adjuvant therapy. Such prooxidant status could have further deleterious consequences since it has been recently shown that antioxidant status could modulate cell functions such as reactive oxygen species (ROS) production, adhesive molecule expression and/or cell proliferation. Preventive modalities, including use of biocompatible membrane, ultrapure dialysate, exogenous supplementation of antioxidant vitamins, extracorporeal removal of ROS and oxidatively-modified substances, would appear highly desirable to reduce complications of long-term dialysis patients.

Dialock: a new vascular access device for extracorporeal renal replacement therapy. Preliminary clinical results.

BACKGROUND: Vascular access, a vital tool for end-stage renal disease patients, remains a weak component of extracorporeal renal replacement therapy (RRT) and the first cause of morbidity. Permanent catheters proposed as an alternative to permanent AV fistulae are associated with a significant risk of infection. A subcutaneously implantable chamber connected to permanent catheter appears highly desirable to reduce such hazards. METHODS: Dialock, a metallic port-like valve device connected to permanent silicone twin catheters has been developed (Biolink Corp, Middleboro, MA, USA). After being implanted subcutaneously below the clavicle, Dialock provides a linear flow passage to two Silastic catheters placed in the right atrium via the right internal jugular vein. The valve is accessed percutaneously each dialysis session with needle cannulae that functionally convert the device into twin catheters. Interdialytic patency of the catheters is ensured by antithrombotic lock (heparin or low-molecular-weight heparin). RESULTS: Dialock was implanted in 10 ESRD patients (64+/-12 years) under general anaesthesia, with almost immediate use for HD. RRT consisted of three HD sessions per week lasting 4 h; 699 HD sessions were performed. Average duration of use was 5.7 patient-months (1.3-9.6 months). Patient satisfaction was evident in all cases. Three episodes of bacteraemia occurring in the early phase of the study were cured by appropriate antibiotics. No device was removed because of infection. Skin condition at the puncture sites has remained satisfactory in all patients. Nurse training for cannulating was brief (2-3 x). Effective blood flow was 307+/-3.3 ml/min, with a venous pressure of 195+/-39 mmHg and a recirculation rate of 6.7+/-0.8%. Effective Kt/V dp delivered was 1.36+/-0.03 with a nPCR of 1.20+/-0.005 g/kg/day. Haematoma and a small amount of bleeding of the skin puncture sites observed in the initial period of the study were effectively prevented by reducing heparin lock volume. CONCLUSIONS: The Dialock device offers a new and interesting vascular access alternative for haemodialysis bridging the 'gap' between permanent catheters and arteriovenous fistulae. Dialock's place in the vascular access strategy for haemodialysis patients deserves further long-term clinical studies.