Anticoagulation intensity sufficient for haemodialysis does not prevent activation of coagulation and platelets

Detection and Scoring of Extracorporeal Circuit Clotting During Hemodialysis

Maintaining patency of the extracorporeal hemodialysis (HD) circuit is a prerequisite to perform HD. Unfractionated heparin and low-molecular-weight heparins are the most used anticoagulants in maintenance HD, but their administration comes with a major trade-off of bleeding complications. This narrative review article discusses technical factors impacting on HD circuit patency, such as tubings, dialyzer membranes, priming practices, and treatment settings. Strategies for monitoring extracorporeal circuit clotting during and after treatment are also reviewed, as these are essential tools for optimizing anticoagulation.

Laboratory Monitoring of Heparin Anticoagulation in Hemodialysis: Rationale and Strategies

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are commonly used to prevent clotting of the hemodialysis extracorporeal circuit and optimize hemodialysis adequacy. There is no consensus on the optimal dosing for UFH and LMWHs during hemodialysis. In clinical practice, semiquantitative clotting scoring of the dialyzer and venous chamber may help to guide UFH and LMWH dose adjustment. Laboratory monitoring has not been shown to improve clinical outcomes and is therefore not routinely indicated in most hemodialysis patients. It might, however, be considered in select patients, such as those with extremes of body weight or history of repeated clotting or bleeding. Methods for laboratory monitoring include the activated partial thromboplastin time, activated clotting time, and antifactor Xa assays for UFH and antifactor Xa assay for LMWHs. Target ranges for anticoagulation in hemodialysis have been suggested but not clearly defined. When utilizing these tests, issues such as availability, standardization, interfering factors, and interpretation must be considered. In this narrative review, we discuss the rationale and methods of monitoring anticoagulation in hemodialysis.

Effect of dialyzer geometry on coagulation activation in the extracorporeal circuit in maintenance hemodialysis patients: Prospective randomized trial

BACKGROUND AND OBJECTIVES

The coagulation cascade is activated during hemodialysis (HD) due to interaction of blood with the dialysis circuit. There is a paucity of data on the effect of the physical structure of the dialyzers on coagulation activation during HD. We conducted this study to compare the effect of Helixone FX80 versus Platinum H4 dialyzers on coagulation activation during HD.

METHODS

Twenty patients on maintenance HD were enrolled in this randomized prospective crossover study. Each patient was dialyzed using Helixone FX80 and Platinum H4 dialyzers. Serum thrombin-antithrombin complex (TAT) was measured before (T0h) and at the end (T4H) of HD.

RESULTS

The absolute changes of serum TAT were comparable with the two dialyzers (median [IQR]: 1.15 [0.65, 1.75] for Helixone FX80 vs. 1.15 [0.67, 2.05] for Platinum H4, p = 0.371).

CONCLUSION

Helixone FX80 and Platinum H4 dialyzers have similar effects on coagulation activation during HD.

Phase 2 Study of the Factor XI Antisense Inhibitor IONIS-FXIRx in Patients With ESRD

Introduction

Patients with end-stage renal disease (ESRD) requiring hemodialysis (HD) have an increased risk of thrombotic events and bleeding. Antisense reduction of factor XI (FXI) with IONIS-FXI_Rx is a novel strategy that may safely reduce the risk of thrombotic events.

Methods

This multicenter study enrolled 49 patients receiving HD in 2 parts. First, 6 participants (pharmacokinetics [PK] cohort) received 1 open-label 300 mg dose of IONIS-FXI_Rx both before and after HD. Subsequently, 43 participants were treated in a double-blind, randomized design with 200 mg or 300 mg IONIS-FXI_Rx or placebo for 12 weeks. The PK, pharmacodynamics (PD), and adverse events of IONIS-FXI_Rx were evaluated (ClinicalTrials.gov: NCT02553889).

Results

The PK of IONIS-FXI_Rx was consistent with previous studies and similar whether injected before or after HD. No accumulation of IONIS-FXI_Rx was observed after repeat administration. By day 85, mean levels of FXI activity fell 56.0% in the 200 mg group, 70.7% in the 300 mg group, and 3.9% in the placebo group compared with baseline. FXI antigen levels paralleled FXI activity. Dose-dependent prolongation of activated partial thromboplastin time (aPTT) was observed, with no changes in international normalized ratio (INR). IONIS-FXI_Rx was not associated with drug-related serious adverse events. In the randomized phase of the study, major bleeding events occurred in 0 (0.0%; 200 mg), 1 (6.7%; 300 mg), and 1 (7.7%; placebo) patients and were not considered related to treatment.

Conclusion

IONIS-FXI_Rx reduced FXI activity in patients with ESRD receiving HD. Further studies are needed to determine the benefit-risk profile of FXI as a therapeutic target for patients who require HD.

Assessment of Coagulation and Hemostasis Biomarkers in a Subset of Patients With Chronic Cardiovascular Disease

Measurement of a single marker of coagulation may not provide a complete picture of hemostasis activation and fibrinolysis in patients with chronic cardiovascular diseases. We assessed retrospective orders of a panel which included prothrombin fragment 1.2 (PF1.2), thrombin: antithrombin complexes, fibrin monomers, and D-dimers in patients with heart assist devices, cardiomyopathies, atrial fibrillation and intracardiac thrombosis (based on ordering ICD-10 codes). During 1 year there were 117 panels from 81 patients. Fifty-six (69%) patients had heart assist devices, cardiomyopathy was present in 17 patients (21%) and 29 patients (36%) had more than 1 condition. PF1.2 was most frequently elevated in patients with cardiomyopathy (61.1%) compared to those with cardiac assist devices (15.7%; P = 0.0002). D-dimer elevation was more frequent in patients with cardiac assist devices (98.8%) compared to those patients with cardiomyopathy (83.3%; P = 0.014). Patients with cardiomyopathy show increases of PF1.2 suggesting thrombin generation. In contrast, elevations of D-dimers without increase in other coagulation markers in patients with cardiac assist devices likely reflect the presence of the intravascular device and not necessarily evidence of hemostatic activation.

Dialyzer Performance During Hemodialysis Without Systemic Anticoagulation Using a Heparin-Grafted Dialyzer Combined With a Citrate-Enriched Dialysate: Results of the Randomized Crossover Noninferiority EvoCit Study

RATIONALE & OBJECTIVE

The EvoCit study was designed to evaluate performance of a heparin-grafted dialyzer during hemodialysis with and without systemic anticoagulation.

STUDY DESIGN

Randomized, crossover, noninferiority trial. Noninferiority was defined as a difference of≤10% for the primary outcome.

SETTING & PARTICIPANTS

Single hemodialysis center; 26 prevalent patients treated with 617 hemodialysis sessions.

INTERVENTIONS

Hemodialysis using a heparin-grafted dialyzer combined with a 1.0mmol/L citrate-enriched dialysate ("EvoCit") without systemic anticoagulation compared with hemodialysis performed with a heparin-grafted dialyzer with systemic heparin ("EvoHep"). Patients were randomly allocated to a first period of 4 weeks and crossed over to the alternative strategy for a second period of 4 weeks.

OUTCOMES

The primary end point was the difference in Kt/V_urea between EvoCit and EvoHep. Secondary end points were urea reduction ratio, middle molecule removal, treatment time, thrombin generation, and reduction in dialyzer blood compartment volume.

RESULTS

The estimated difference in Kt/V_urea between EvoCit and EvoHep was-0.03 (95% CI, -0.06 to-0.007), establishing noninferiority with mean Kt/V_urea of 1.47±0.05 (SE) for EvoCit and 1.50±0.05 for EvoHep. Noninferiority was also established for reduction ratios of urea and β₂-microglobulin. Premature discontinuation of dialysis was required for 4.2% of sessions among 6 patients during EvoCit and no sessions during EvoHep. Effective treatment time was 236±5 minutes for EvoCit and 238±1 minutes for EvoHep. Thrombin generation was increased and there was greater reduction in dialyzer blood compartment volume after treatments with EvoCit compared with EvoHep.

LIMITATIONS

The effects of avoiding systemic anticoagulation on clinical outcomes were not evaluated.

CONCLUSIONS

EvoCit is noninferior to EvoHep with respect to solute clearance but results in a greater number of shortened treatments, more membrane clotting, and greater thrombin generation TRIAL REGISTRATION: Registered at ClinicalTrials.gov with study number NCT03887468.

Vitamin K antagonist has a higher impact than heparin in preventing circuit clotting in chronic haemodialysis patients

Background

In dialysis sessions, some data suggest that decreasing or even avoiding additional anticoagulation by heparin is possible among patients already treated with oral anticoagulation. However, the required dose of heparin may actually depend on the pre-dialysis international normalized ratio (INR), which varies from one session to another. The aim of our study was to determine the respective role of INR and heparin dosing in the risk of circuit clotting during chronic haemodialysis.

Methods

From early 2012 to July 2016, we analysed the totality of dialysis sessions performed at Brest University Hospital among haemodialysis patients treated by vitamin K antagonists (VKA). We established a prediction of circuit clotting on the basis of a simplified score obtained by combining INR and heparin dosing.

Results

In total, 7184 dialysis sessions among chronic haemodialysis patients under VKA were identified, including 233 with clotting events. The mean INR without clotting events was 2.5 versus 1.8 with clotting events (P < 0.001). Frequencies of circuit clotting were different according to INR group (INR <2.0, INR 2.0-3.0, INR >3.0; P < 0.0001). The protective role of VKA was higher than heparin, as shown by discriminant factor analysis (P < 0.0001). Conclusion. Our study established a predictive model of thrombosis risk of dialysis circuits in patients treated by VKA for a given heparin dose and a given INR. This model shows a marginal contribution of heparin to protect against the risk of thrombosis compared with VKA. Moreover, heparin would not appear to be necessary for patients with an INR >2.2.

Hemodialysis Does Not Induce Detectable Activation of the Contact System of Coagulation

Introduction

Systemic anticoagulation is administered during hemodialysis to prevent clotting of the extracorporeal circuit. The role of contact system activation in thrombin generation during hemodialysis using current era dialyzer membranes is unknown.

Methods

We performed a single-center randomized crossover study. Ten patients treated with hemodialysis underwent 3 standardized hemodialysis sessions. For every patient, each session was performed with a different type of dialyzer membrane (polyphenylene [PP], polymethylmetacrylate [PMMA], polyethylenimine-coated polyacrylonitrile [AN69ST]). Blood samples were collected before and 5, 15, 30, 90, and 240 minutes after blood pump start to evaluate coagulation activation (thrombin–antithrombin complex [TAT], prothrombin fragment 1+2 [PF1+2], activated factor XII [FXIIa], kallikrein, activated factor XI [FXIa]). Plasma of healthy volunteers (n = 20) was used as a reference.

Results

Baseline TAT and PF1+2 levels were higher in hemodialysis patients compared to healthy controls (median [interquartile range] for TAT: 3.3 [2.9–4.2] vs. 2.4 [2.3–2.5] μg/l [P = 0.0002] and for PF1+2: 647 [478–737] vs. 138 [125–254] pmol/l [P < 0.0002]). Despite the use of systemic anticoagulation, TAT further increased during treatment, with the increase starting after 30 minutes (median TAT at t240: 9.0 μg/l (PP), 5.5 μg/l (PMMA), and 7.2 μg/l (AN69ST), all P < 0.05 vs. baseline). Contact system markers FXIIa and kallikrein did not differ significantly between dialysis patients and healthy controls, whereas baseline FXIa levels were significantly lower in dialysis patients compared to healthy controls (P = 0.001). Levels of all contact system markers remained unchanged during hemodialysis with all types of dialyzer membranes.

Conclusion

Routine hemodialysis using systemic heparin anticoagulation induces coagulation activation without measurable contact system activation.

Examining hemodialyzer membrane performance using proteomic technologies

The success and the quality of hemodialysis therapy are mainly related to both clearance and biocompatibility properties of the artificial membrane packed in the hemodialyzer. Performance of a membrane is strongly influenced by its interaction with the plasma protein repertoire during the extracorporeal procedure. Recognition that a number of medium-high molecular weight solutes, including proteins and protein-bound molecules, are potentially toxic has prompted the development of more permeable membranes. Such membrane engineering, however, may cause loss of vital proteins, with membrane removal being nonspecific. In addition, plasma proteins can be adsorbed onto the membrane surface upon blood contact during dialysis. Adsorption can contribute to the removal of toxic compounds and governs the biocompatibility of a membrane, since surface-adsorbed proteins may trigger a variety of biologic blood pathways with pathophysiologic consequences. Over the last years, use of proteomic approaches has allowed polypeptide spectrum involved in the process of hemodialysis, a key issue previously hampered by lack of suitable technology, to be assessed in an unbiased manner and in its full complexity. Proteomics has been successfully applied to identify and quantify proteins in complex mixtures such as dialysis outflow fluid and fluid desorbed from dialysis membrane containing adsorbed proteins. The identified proteins can also be characterized by their involvement in metabolic and signaling pathways, molecular networks, and biologic processes through application of bioinformatics tools. Proteomics may thus provide an actual functional definition as to the effect of a membrane material on plasma proteins during hemodialysis. Here, we review the results of proteomic studies on the performance of hemodialysis membranes, as evaluated in terms of solute removal efficiency and blood-membrane interactions. The evidence collected indicates that the information provided by proteomic investigations yields improved molecular and functional knowledge and may lead to the development of more efficient membranes for the potential benefit of the patient.

β-Thromboglobulin may not reflect platelet activation during haemodialysis with the HeprAN membrane

BACKGROUND

When blood passes through the extracorporeal circuit during haemodialysis (HD) undesirable effects including platelet degranulation and coagulation activation take place. β-thromboglobulin (β-TG) is a sensitive marker of platelet activation. The aim of this study was to investigate platelet degranulation and coagulation activation during HD with the heparin-coated dialysis membrane HeprAN.

METHODS

Four HD sessions were evaluated in each of 12 chronic HD patients. None of the patients used oral warfarin, other anticoagulants or antiplatelet drugs. In the first session the HeprAN membrane or a conventional polyflux membrane was used in a randomized manner and thereafter alternately in a cross-over design, and 50% of the conventional dalteparin dose was given at start of HD. Prothrombin fragment 1 + 2 (PF1 + 2), β-TG and anti-factor Xa activity were measured repeatedly.

RESULTS

No dialysis sessions were terminated early due to clotting of the extracorporeal system. Activation of intravascular coagulation as assessed by change in PF1 + 2 during 4 hours of HD was the same with the two membranes. β-TG concentration decreased significantly during 4 hours of HD with the HeprAN membrane but remained stable with the polyflux membrane.

CONCLUSION

There were no differences in clotting scores or coagulation activation with the two membranes. The decrease in β-TG during HD with the HeprAN membrane suggests β-TG to be an inferior marker of platelet degranulation when using a heparin-coated dialysis membrane. A possible mechanism for the decline in β-TG concentration may be adherence of this heparin-binding protein to the heparin-coated dialysis membrane.

Vascular adhesion protein-1 in hemodialysis and hemodiafiltration patients: effect of single hemodialysis session on its level in regard to type of anticoagulant

PURPOSE

Traditional anticoagulants used in intermittent hemodialysis (HD) are unfractionated heparin (UFH) and increasingly low molecular weight heparins (LMWHs). Repeated and prolonged exposure to UFH and/or LMWHs may further disturb hemostasis in uremic patients. Vascular adhesion protein-1 (VAP-1) is secreted by vascular smooth muscle cells, adipocytes and endothelial cells with functional monoamine oxidase activity and is elevated in atherosclerosis, diabetes mellitus and obesity. The aim of this study was to assess the effects of UFH and LMWHs on VAP-1 concentration in HD patients. The effects on single HD session on VAP-1 were also evaluated as well as VAP-1 levels in regard to type of renal replacement therapy.

METHODS

We studied 82 hemodialyzed patients (mean age 63 years, dialysis vintage 59 months) and 17 patients treated by means of hemodiafiltration (HDF) (mean age 59 years, HD vintage 84 months, HDF 7 months). Patients were anticoagulated with enoxaparin (n = 46), dalteparin (n = 10), nadroparin (n = 6) or UFH (n = 20) during their HD sessions. VAP-1 was assessed using kits from BioVendor, Modrice, Czech Republic.

RESULTS

Patients on HDF had significantly lower VAP-1 when compared with HD patients. We found that VAP-1 concentration in patients dialyzed by using LMWH or UFH was similar. There was no effect on HD session on VAP-1 concentration. Diabetic patients had higher serum VAP-1 than non-diabetic.

CONCLUSIONS

HDF is associated with lower VAP-1 levels indicating less pronounced endothelial cell injury than hemodialysis. Type of heparin seems to have no effect on VAP-1 levels in hemodialyzed patients. However, the cross-sectional but not prospective design is a limitation of this study.

Upper-extremity Deep Vein Thrombosis Complicating Apheresis in a Healthy Donor

Venous thrombus was recognized in the upper extremity of a 53-year-old man after blood donation. The patient presented with a 15-day history of swelling in the left upper-extremity that started 6 hours after apheresis. Contrast-enhanced computed tomography revealed clots in the deep veins of the left arm and the peripheral pulmonary artery. Blood donation had proceeded smoothly, and the patient had no thrombotic predisposition, except for a smoking habit. The thrombus resolved following anticoagulant therapy, and the patient' s clinical course was uncomplicated. Despite a thorough investigation, the cause of this thrombus remains unknown.

Coagulation, thrombophilia and patency of arteriovenous fistula in children undergoing haemodialysis compared with healthy volunteers: a prospective analysis

This study aimed to assess whether markers of coagulation, fibrinolysis or thrombophilia are increased in children on haemodialysis compared with controls and whether measurement of any of these factors could help to identify patients at an increased risk of arteriovenous fistula (AVF) occlusion. Blood samples were taken from 55 children immediately before a session of haemodialysis and from 20 healthy volunteers. Thrombin-antithrombin (TAT), D-dimer, plasmin-antiplasmin (PAP) and anticardiolipin immunoglobulin G (ACA-Ig G) were measured by ELISA. Factor V Leiden mutation (G1691A) was determined by gene polymorphism [restriction fragment length polymorphism (RFLP)]. Determination of the patency of the AVF was prospectively followed up for a minimum of 4 years or until the AVF was nonfunctioning. Fifty-five patients were studied with a median follow-up of 659 days (range 30-1670 days). A significant increase was found in the levels of D-dimer, PAP and ACA-Ig G in haemodialysis patients with thrombosed and nonthrombosed native AVFs vs.

CONTROLS

There was a significant difference between both chronic haemodialysis patients with thrombosed and nonthrombosed native AVF with regard to ACA-IgG levels. At 1 year follow-up, primary patency was 61.4% (27 patients). In multivariate analysis, D-dimer was inversely associated with secondary patency.Thrombophilia may predispose children with end stage renal disease to access failure. The promising finding is that in children on haemodialysis, D-dimer levels were increased and inversely correlated with secondary patency. Further evaluation is required into the possible role of D-dimer as a biomarker of AVF occlusion.

Soluble P-Selectin During a Single Hemodialysis Session in Patients With Chronic Renal Failure and Erythropoietin Treatment

In several studies, hemodialysis (HD) patients treated with recombinant human erythropoietin (rHuEPO) because of renal anemia showed increased levels of soluble adhesion molecules. The purpose of the study was to investigate the changes of soluble P-selectin (sSELP) and its relationship to platelet activation during a single HD session in patients with long-term rHuEPO treatment. Fifty-two HD patients with chronic renal failure were involved—26 with rHuEPO treatment (EPO group) and 26 without (non-EPO group). Thirty healthy subjects served as the control group. The sSELP, β-thromboglobulin, and platelet factor 4 plasma levels were measured before and after a single 4-hour HD session on a cuprophane dialyzer. The basal β-thromboglobulin and platelet factor 4 plasma levels were significantly increased in both HD groups compared with healthy controls but did not change after a single HD session, except for a significant decrease of platelet factor 4 in the non-EPO group. The predialysis sSELP plasma levels did not differ significantly compared with those of the healthy controls, but there was a significant increase of sSELP levels after a single HD session in both groups (EPO, P < .005; non-EPO, P < .05, respectively). These results suppose that the increased sSELP level was released from platelets during the course of a single HD session. The more significant increase of the sSELP plasma levels in EPO group during HD indicates that platelets are more activated in patients with long-term rHuEPO treatment, and this fact could partially explain the suspected tendency for thrombosis in these patients.

Effect of Heparin on Coagulation Tests: A Comparison of Continuous and Bolus Infusion in Haemodialysis Patients

INTRODUCTION

Haemodialysis is one of the most conventional treatments of chronic renal failure. The risk of clot formation is high during haemodialysis due to regular contact of blood with the surfaces of foreign objects such as catheters, dialyzers' membrane, and other materials used for dialysis. Therefore, to prevent clot formation during haemodialysis, the dialysis system requires anticoagulation; this is usually done by heparin.

AIM

The present study aimed to compare two heparinization methods and determine the proper impacts of these methods.

MATERIALS AND METHODS

In this quasi-experimental study, 80 haemodialysis patients covered by the dialysis center of Amir-al-momenin Hospital of Zabol were studied in two 40-member groups of heparin therapy methods of bolus injection and continuous infusion. PT and PTT were measured in blood samples collected from all patients before starting haemodialysis. The first group received 3000 units of heparin once the haemodialysis machine started to work and 2000 units of heparin two hours later as bolus injection. In the second group, 1500 units of heparin was injected at the start of dialysis after then, 5000 units of heparin (one mL) were mixed with 11 mL of distilled water and infused using a heparin injection pump up to half an hour before the end of dialysis. At 30 minutes after starting dialysis and at the end of 4 hours of haemodialysis, PT and PTT were measured and compared between the two groups.

RESULTS

According to the results, the mean partial thromboplastin time in the bolus and continuous heparin-receiving group was 41.75±6.29 and 37.90±4.77, respectively, which was statistically significant (p=0.036). But PT was 14.45±1.82 in the bolus heparin group and 13.95±1.39 in the continuous heparin group, which was not significant according to the results of independent t-test (p=0.336).

CONCLUSION

The results indicated a statistically significant difference between the bolus heparin injection and the continuous heparin infusion groups in terms of coagulation tests in haemodialysis patients (p=0.036). Therefore, given the effects of heparin on coagulation, it was more effective in the bolus heparin group than the continuous infusion group. It is recommended to use the bolus method for heparin therapy during haemodialysis.

Biocompatibility assessment of haemodialysis membrane materials by proteomic investigations

We examine and compare the protein adsorption capacity and coagulation profiles of different haemodialysis membrane biomaterials.

Thrombin-anti-thrombin levels and patency of arterio-venous fistula in patients undergoing haemodialysis compared to healthy volunteers: a prospective analysis

Background

Patients on haemodialysis (HD) are at an increased risk of sustaining thrombotic events especially to their vascular access which is essential for maintenance of HD.

Objectives

To assess whether 1) markers of coagulation, fibrinolysis or endothelial activation are increased in patients on HD compared to controls and 2) if measurement of any of these factors could help to identify patients at increased risk of arteriovenous (AVF) access occlusion.

Patients/Methods

Venous blood samples were taken from 70 patients immediately before a session of HD and from 78 resting healthy volunteers. Thrombin-antithrombin (TAT), D-dimer, von Willebrand factor (vWF), plasminogen activator inhibitor-1 antigen (PAI-1) and soluble p-selectin were measured by ELISA. C-reactive protein (hsCRP) was measured by an immunonephelometric kinetic assay. Determination of the patency of the AVF was based upon international standards and was prospectively followed up for a minimum of four years or until the AVF was non-functioning.

Results

A total of 70 patients were studied with a median follow-up of 740 days (range 72-1788 days). TAT, D-dimer, vWF, p-selectin and hsCRP were elevated in patients on HD compared with controls. At one year follow-up, primary patency was 66% (46 patients). In multivariate analysis TAT was inversely associated with primary assisted patency (r= -0.250, p= 0.044) and secondary patency (r = -0.267, p= 0.031).

Conclusions

The novel finding of this study is that in patients on haemodialysis, TAT levels were increased and inversely correlated with primary assisted patency and secondary patency. Further evaluation is required into the possible role of TAT as a biomarker of AVF occlusion.

A multi-center, prospective, open-label, 8-week study of certoparin for anticoagulation during maintenance hemodialysis--the membrane study

Background

Adequate anticoagulation is prerequisite for effective hemodialysis to prevent clotting in the extracorporeal circuit. We aimed providing first data on the efficacy and safety of the low-molecular-weight heparin certoparin in this setting.

Methods

Multicenter, open-label, 8-week trial. Patients received a single dose of 3,000 IU certoparin i.v. with additional titration steps of 600 IU and/or continuous infusion if necessary.

Results

120 patients were screened, 109 enrolled (median age 71; range 26–90 years) and 106 available for efficacy analyses. The percentage of unsatisfactory dialysis results at 8 weeks due to clotting or bleeding, was 1.9% (n = 2/106; 95% confidence interval [CI] 0.23–6.65%); no major bleeding. 1.9% had moderate/severe clotting in the lines/bubble catcher and 2.8% in the dialyser at week 8. 15.7 ± 14.3% of the dialysis filters’ visual surface area was showing redness. In subgroups of patients receiving median doses of 3000 ± 0, 3000 (2400–6000) and 4200 (3000–6600) IU, plasma aXa levels at baseline, 4 and 8 weeks were 0.24 [95%CI 0.21–0.27], 0.33 [0.27–0.40] and 0.38 [0.33–0.45] aXa IU/ml at 2 h. C_48h was 0.01 [0.01–0.02] aXa IU at all visits. At baseline and 4 weeks AUC_0-48h was 2.66 [2.19–3.24] and 3.66 [3.00–4.45] aXa IU*h/ml. In 3.0% of dialyses (n = 83/2724) prolonged fistula compression times were documented. Eight patients (7.34%) had at least one episode of minor bleeding. 4) 85.3% of patients had any adverse event, 9.2% were serious without suspected drug relation; and in 32 patients a drug-relation was suspected.

Conclusions

Certoparin appears effective and safe for anticoagulation in patients undergoing maintenance hemodialysis.

Coagulation activation is associated with nicotinamide adenine dinucleotide phosphate oxidase-dependent reactive oxygen species generation in hemodialysis patients

AIMS

This study investigated on (i) the role of gp91(phox)/NOX2 in reactive oxygen species (ROS) generation in hemodialysis (HD) patients, and (ii) the link between clotting activation and ROS production in this setting.

RESULTS

The study was performed on peripheral blood mononuclear cells (PBMCs) isolated from HD patients randomized to polysulphon/polyamide (S-group, n=30) or ethylene-vinyl-alcohol (EVAL) membrane (E-group, n=30) treatment and from healthy subjects (control group, n=15). ROS generation was increased in PBMCs of HD patients compared with healthy subjects. S-group showed higher levels of intracellular ROS generation than control, whereas E-group did not. In addition, S-group displayed an increase in nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity compared with E-group and healthy subjects. A further increase in NADPH activity shortly after HD treatment was observed only in S-group. The plasma levels of the prothrombin fragment F1+2, a marker of in vivo clotting activation, were significantly higher in S-group than in E-group. Moreover, a heightened thrombin generation was recorded in the plasma of S-group. Intracellular ROS production correlated with NADPH oxidase activity and coagulation priming in HD patients. The in vitro validation study demonstrated that incubation of PBMCs with activated FX induced a significant increase in intracellular ROS production, superoxide generation, and gp91(phox)/NOX2 expression.

INNOVATION

The pivotal role of NADPH oxidase in the upregulation of ROS in HD patients makes this enzyme a potential target for therapeutic intervention in the treatment of HD-related oxidative stress.

CONCLUSION

The EVAL membrane, by reducing clotting activation, inhibits gp91(phox)/NOX2-related ROS production in HD patients.

Bleeding and thrombotic complications of kidney disease

With the rising prevalence of kidney disease, clinicians are increasingly faced with concerns about potential thrombotic and bleeding complications. Thrombotic risk, both arterial and venous, predominates with all severities of kidney disease but bleeding manifestations become an additional concern particularly with uraemia. This article reviews these contrasting problems and discusses strategies for prevention and management in the context of renal impairment, renal replacement therapy and renal transplantation.

Prothrombotic changes in platelet, endothelial and coagulation function following hemodialysis

PURPOSE

Patients on hemodialysis (HD) have an increased risk of thrombotic events, including myocardial infarction and vascular access thrombosis. The study hypothesis is that a single session of dialysis leads to platelet, endothelial and coagulation activation. Our aim is to determine the effect of a single HD session on prothrombotic vascular biomarkers before and after a single session of hemodialysis.

METHODS

Blood samples were taken from the vascular access of 55 patients immediately before and after a hemodialysis session. Platelet function was assessed by (1) flow cytometric measurement of P-selectin expression and fibrinogen binding +/- ADP stimulation, (2) Ultegra rapid platelet function assay (RPFA) using the agonists thrombin receptor activating peptide (TRAP) and arachidonic acid (AA), (3) soluble P-selectin, and (4) soluble CD40L. Coagulation (thrombin-antithrombin III [TAT] and D-dimer), endothelial von Willebrand factor (vWF) and high sensitivity C-Reactive protein (hsCRP) were assessed by ELISA.

RESULTS

Unfractionated heparin was given to all patients during dialysis and 30 patients (55%) were on antiplatelet agents. Post-hemodialysis there were significant increases in unstimulated platelet P-selectin (p=.037), stimulated P-selectin (p<.001), soluble P-selectin (p<.001) and soluble CD40L (p=.036). Stimulated platelet fibrinogen binding was increased post-hemodialysis (p<.001) but unstimulated fibrinogen binding was unchanged. TRAP- (p<.001] and AA-(p=.009) stimulated aggregation were reduced post-hemodialysis. There were increases post-hemodialysis in TAT (p<.001), D-dimer (p<.001), vWF (p<.001) and hsCRP (p=.011).

CONCLUSION

This study has shown that despite heparin therapy, a single session of HD induced increases in platelet, endothelial, and coagulation activation. More effective medical strategies to reduce the prothrombotic state of patients on hemodialysis should be investigated.

Systemic anticoagulation considerations in chronic kidney disease

Anticoagulation therapy is commonly required in patients with chronic kidney disease for treatment or prevention of thromboembolic disorders. Anticoagulant management plans can involve use of a single agent, or in some cases, a combination of agents to meet both short- and long-term goals. Systemic anticoagulation in the setting of renal insufficiency poses unique challenges secondary to renal failure-associated hypercoagulable conditions and increased risks for bleeding. Evidence supporting dosing regimens and monitoring approaches in the setting of severe renal impairment or hemodialysis is limited because this population is typically excluded in clinical trials. This review explores concepts of systemic anticoagulation in the chronic kidney disease setting with warfarin, unfractionated heparin, low-molecular-weight heparin, fondaparinux, direct thrombin inhibitors, and anticoagulants in advanced stages of development. Potential strategies for anticoagulant reversal are also briefly described.

Different effects of enoxaparin, nadroparin, and dalteparin on plasma TFPI during hemodialysis: a prospective crossover randomized study

BACKGROUND

Low-molecular-weight heparins (LMWHs) are an alternative to unfractionated heparin (UFH) for anticoagulation during hemodialysis (HD). We performed a prospective randomized crossover study of the effect of enoxaparin, nadroparin, and dalteparin on some hemostatic factors, including tissue factor pathway inhibitor (TFPI), in patients with maintenance HD.

METHODS

Plasma levels (immunoassays) of total TFPI, platelet-derived growth factor-AB (PDGF-AB), and prothrombin fragment 1 + 2 (PF 1 + 2) were evaluated pre-HD, after 10 (T10) and 180 (T180) minutes of HD in 21 patients, who completed a 3-period (for 2 months each) crossover study in 6 groups (Latin-square design).

RESULTS

The baseline TFPI, PDGF-AB, and PF 1 + 2 levels were comparable under all LMWH treatments. Tissue factor pathway inhibitor levels, compared with the baseline, significantly increased (all P < 10(-4)), whereas PDGF-AB levels remained stable at each interval during enoxaparin, nadroparin, and dalteparin anticoagulated HD. Interestingly, TFPI increment at T10 was the highest, dose-dependent, and accompanied by PF 1 + 2 decrease under enoxaparin administration.

CONCLUSION

The switch from enoxaparin to nadroparin and dalteparin used as anticoagulants had no long-term effect on the baseline total TFPI and PF 1 + 2 levels in chronically HD patients. Only short-term, overdialytic differences were noticed, indicating a single bolus of enoxaparin (0.75 mg/kg) as the most potent stimulus for endothelial TFPI.

Monitoring of low molecular weight heparin anticoagulation during haemodialysis with a Sonoclot Analyzer

OBJECTIVES

Sonoclot was used in this study to monitor low molecular weight heparin (LMWH) during haemodialysis.

MATERIAL AND METHODS

Two different intravenous doses (standard / half-dose) of dalteparin were studied in eight patients. Blood was sampled for coagulation analyses with Sonoclot, thrombin-antithrombin (TAT) and anti-Xa. A visual fibrin deposition score (VFS) in the venous drip chamber was also evaluated.

RESULTS

All patients completed their dialysis. There was a progressive increase in TAT levels, which correlated to the dalteparin dose. Significant differences (p<0.05) were found for TAT, VFS and Sonoclot celite-activated clotting time (SonACT) between the different LMWH dosages. TAT and Sonoclot correlated to each other, but not to the VFS. SonACT was significantly increased at two hours, with the high dalteparin dose compared to the lower dose.

CONCLUSION

Both Sonoclot and TAT failed to predict the VFS. No patient had any clinical clotting events and all dialyses were completed successfully.

Microemboli, developed during haemodialysis, pass the lung barrier and may cause ischaemic lesions in organs such as the brain

BACKGROUND

Chronic haemodialysis (HD) may relieve some medical problems of terminal uraemia, but the life expectancy of patients is still significantly shortened, and there is a greatly increased morbidity. This includes pulmonary morbidity and chronic central nervous system (CNS) abnormalities. Previous studies have shown that a considerable amount of air microbubbles emanate within the blood lines of the dialysis device and pass the air detector without sounding an alarm. The aim of this study was to investigate whether microemboli can pass to the patient and whether they could be detected in the carotid artery.

METHODS

A total of 54 patients on chronic HD (16 with central dialysis catheter) were investigated with an ultrasound detector (Hatteland, Røyken, Norway) for the presence of microemboli at the arteriovenous (AV) fistula/graft and at the common carotid artery before and during HD. Measurements were taken for 2 and 5 min, respectively. Non-parametric paired statistics were used (Wilcoxon).

RESULTS

The median number (range) and mean +/- SD of microembolic signals detected at the AV access site before commencing dialysis and during HD were 0 (0-3) and 0.2+/- 0.5 versus 4 (0-85) and 13.5 +/- 20 (P = 0.000); at the carotid artery, 1 (0-14) and 1.7 +/- 2.9 versus 2 (0-36) and 3.5 +/- 5.8 (P = 0.008).

CONCLUSIONS

The infused and returning fluid from HD devices contains air microbubbles that enter the patient without triggering any alarms. These small emboli pass the lung and may cause ischaemic lesions in organs supported by the arterial circuit, such as the brain.

Diabetes, vascular complications and antiplatelet therapy: open problems

Diabetes mellitus is commonly associated with both microvascular and macrovascular complications (coronary artery disease, cerebrovascular events, severe peripheral vascular disease, nephropathy and retinopathy). There is wide evidence demonstrating that platelet degranulation and synthesis of TxA2 are increased in diabetic patients. For this reason, many studies on anti-platelet therapy have been made to reduce thrombotic complication of diabetes mellitus. Some diabetic patients, although treated with ASA, have a high prevalence of recurrent thrombotic events, which may presumably be due to an "ASA resistance". Nevertheless, this drug remains the one with the greatest benefit. To optimize its function, we should try to understand the causes of "aspirin resistance", try to find the most suitable dosage, recommending patients to comply constantly with the prescription given and to avoid interactions with other drugs. "Clopidogrel resistance" is a term not clearly defined. The clinical implications of "clopidogrel resistance" are unknown. An important consideration affecting the use of aspirin in diabetic patients is its interaction with ACE-inhibitors. Another question is antiplatelet therapy in nephropathic diabetic patients. Although these patients are at high thrombotic and haemorrhagic risk, they should nevertheless be considered eligible to undergo antithrombotic therapy, taking into account the individual's haemorrhagic risk.

Unfractionated Heparin but Not Enoxaparin Causes Delayed Plasma PAI-1 Depletion in Hemodialysis Patients: A Prospective Study

Background and aims. Heparin modulates function of vascular endothelial cells. We studied the effects of unfractionated heparin (UFH) versus low-molecular-weight heparin (LMWH), enoxaparin, used as anticoagulants during hemodialysis (HD) on plasma levels of circulating endothelium-derived molecules: thrombomodulin (TM), von Willebrand factor (vWF), plasminogen activator inhibitor-1 (PAI-1), cell surface adhesion molecules (E-selectin), intercellular adhesion molecule-1 (ICAM-1), and prothrombin fragment 1+2 (PF 1+2). Methods. Twenty-five patients undergoing enoxaparin-anticoagulated HD were randomly assigned either to continue enoxaparin (n = 13) or receive UFH (n = 12) during HD and followed prospectively for 12 weeks. Plasma immunoreactive TM, vWF, PAI-1, ICAM-1, E-selectin, and PF 1+2 were measured before the randomization procedure and after 12 weeks, at the start, after 10 and 180 minutes of HD. Results. The switch from LMWH to UFH resulted in decreased pre-HD levels of PAI-1 and TM and increased PF 1+2 concentrations. Predialysis PAI-1 negatively correlated with the total dose of UFH/kg/HD. No significant differences were observed in the other variables before and during HD after switching from LMWH to UFH. During enoxaparin-anticoagulated HD, only plasma PAI-1 levels decreased by 32% after 180 minutes compared with the baseline values. This percentage decrease positively correlated with predialysis PAI-1 levels and marginally with PF 1+2 concentrations after 180 minutes of enoxaparin-anticoagulated HD. Conclusion. Enoxaparin-anticoagulated HD is related to transient plasma PAI-1 decrease, whereas UFH anticoagulation may be the cause of delayed PAI-1 and TM depletion, which is an untoward consequence of enhanced coagulation activity in chronic HD patients.

Platelet Adhesion Testing May Predict Early Hemodialysis Arteriovenous Graft and Fistula Failure in End-Stage Renal Disease Patients

Vascular access thrombosis (VAT) is the most morbid and costly complication in end-stage renal disease (ESRD) patients. Although hypercoagulability is a major risk factor for VAT, in most patients, the cause of hypercoagulability cannot be identified despite clinical suspicion. In this study, platelet hyperreactivity was investigated for a possible role in the hypercoagulability of ESRD and VAT in 42 patients with arteriovenous (AV) grafts or fistulas. Platelet adhesion, platelet aggregation, and the history of VAT were assessed. The statistics included a nonparametric 2-factor ANOVA, a Mann-Whitney analysis, and a Kaplan-Meier analysis of hemodialysis angioaccess survival to examine platelet hyperadhesiveness as a predictor of access survival. The study showed a significant correlation between increased platelet adhesiveness and shortened survival of the primary hemodialysis angioaccess. Collagen-induced platelet aggregation reflected a significantly higher response in those with shortened access survival. These findings may have significant clinical implications for risk assessment and prevention of VAT.

Anticoagulation with low-molecular-weight heparin (dalteparin) in plasmapheresis therapy: initial experience

BACKGROUND

In contrast to other extracorporeal treatments no established regime exists for anticoagulation with low-molecular-weight heparin (LMWH) in plasmapheresis therapy. A study was conducted to investigate whether LMWH (dalteparin-Na) is suitable as an effective anticoagulant in plasmapheresis therapy.

STUDY DESIGN AND METHODS

Eleven patients with autoimmune neurological diseases and the necessity for a plasmapheresis therapy were enrolled. A capillary membrane filter was used. A total of 2000 mL of human plasma was isovolumetrically exchanged per plasmapheresis cycle. The anticoagulation was accomplished with a single bolus of LMWH (dalteparin) of 80 to 90 IU per kg of body weight. The system was visually monitored. Anti-factor (F)Xa activity, thrombin-antithrombin III complex (TAT), and prothrombin fragment 1+2 (F 1+2) were determined at regular intervals. Samples were taken from the collected plasma pool to determine the loss of LMWH during the plasmapheresis procedure.

RESULTS

All plasmapheresis cycles with LMWH were successful without complications. Approximately 40 percent of the initially administered LMWH bolus was lost by the large porous filter during the plasmapheresis. The anti-FXa values were determined to be 0.5 IU per mL during the entire plasmapheresis. TAT values were elevated (TAT median, 14.3 microg/L). F 1+2 values measured before the filter cartridge remained within the normal range for the entire plasmapheresis cycle (<1.2 nmol/L) and were increasingly elevated after the filter.

CONCLUSION

Our initial experiences with LMWH for anticoagulation in plasmapheresis indicate that a body weight adjusted dose of LMWH (dalteparin) is suitable for anticoagulation in plasmapheresis therapy. No complications were observed. The data are encouraging. Further investigations will show if and how the present anticoagulation regime could be further optimized.

Activation of Coagulation During Hemodialysis: Effect of Blood Lines Alone and Whole Extracorporeal Circuit

Activation of coagulation during hemodialysis (HD) is a relevant clinical problem, especially when patients at risk of bleeding are treated. However, little is known about the relative contribution of the various components of the circuit to the thrombotic process. Thus, an experimental model was developed that is aimed at evaluating biochemical markers of coagulation activation at different times and sites throughout the HD circuit. A HD blood-tubing set with integrated arterial and venous chambers (cartridge-line set) was used, which was added with the following sampling points: at the beginning of the arterial line (P1), before the blood pump (P2), after the blood pump (P3), and at the end of the venous line (P4). A bypass system allowed us to circulate the blood only into the blood lines for the first 20 min of the extracorporeal circulation. The extracorporeal circuit was rinsed with 1.7 L of heparinized saline (2,500 IU/L) that was completely discarded before patient connection. A continuous administration of unfractionated heparin (500-800 IU/h) without a starting bolus was adopted as a low heparin extracorporeal treatment. Samples were collected before the start of the extracorporeal circulation from the fistula needle (T0P0), after 5 (T1), 10 (T2), and 20 min (T3) from P1, P2, P3, and P4. After 20 min, the blood was returned to the patient using only saline and HD was then started, circulating the blood through the dialyzer. Further samples were obtained from P1 and P4 after 5 (T4) and 210 min (T5). Plasma levels of coagulation activation markers-thrombin-antithrombin complex (TAT) and prothrombin fragment 1 + 2 (F1 + 2)-were evaluated in all the samples in 12 stable HD patients. In each patient, the activated partial thromboplastin time (APTT) was measured at T0P0 and T1-T5 from P1. No significant changes were found at any time as far as F1 + 2 is concerned. However, TAT levels increased over time only after the start of HD, suggesting that the latter test could be more useful in order to detect coagulation activation during HD. The same experiments performed with nonheparin-primed extracorporeal circuit showed similar results. The blood lines used did not significantly activate coagulation during the first 20 min, whereas only 5 min of blood circulation throughout the whole circuit increased TAT values, which still remained lower than previous reports, even after 210 min of treatment.

uPAR (CD87) as a biocompatibility marker of dialysis membrane

BACKGROUND/AIMS

Hemodialysis (HD) therapy may lead to functional changes in patient leukocytes. For example, the upregulation of inflammatory cytokines, such as IL-1beta and TNFalpha, has been well characterized. However, these findings do not explain the entire response of leukocytes in HD. In this study, we carried out a comprehensive gene expression analysis in leukocytes treated with various dialysis membranes using DNA microarrays. The identified gene has the potential to be a new marker for testing dialysis membrane biocompatibility.

METHODS

Gene expression profiles were compared between a group of leukocytes treated with various dialysis membranes and an untreated group by using DNA microarray analysis. Expression was confirmed by quantitative RT-PCR. The expression of the gene product (leukocyte surface protein) was examined in 20 chronic HD patients by flow cytometry.

RESULTS

In addition to the inflammatory cytokines, the urokinase plasminogen activator receptor (uPAR or CD87) gene was induced in leukocytes treated with each dialysis membrane. The extent of induction depended on the membrane's material composition. The expression of the uPAR (CD87) protein on leukocytes was markedly increased in patients undergoing dialysis therapy. The magnitude of uPAR (CD87) protein expression was correlated with clinical findings, i.e., the degree of leukopenia and the expression of adhesion molecules.

CONCLUSIONS

The gene and protein expression of uPAR (CD87) depended on the dialysis membrane material and correlated closely with clinical findings. These results suggest that uPAR has the potential to serve as a marker not only for clinical use but also for the development of new dialysis membranes.

Thromboembolism and anticoagulant management in hemodialysis patients: A practical guide to clinical management

The need for anticoagulation in dialysis patients is common and the incidence of venous thromboembolism (VTE) and atrial fibrillation in this population is high. While direct data are lacking on the management of anticoagulation in dialysis patients, careful weighing of risks and benefits on the basis of evidence from other populations is crucial. VTE should be managed with adjusted dose warfarin for most patients. Placement of an inferior vena cava filter is a reasonable option for those patients with unacceptable bleeding risks. Studies are ongoing to assess the safety of some low-molecular-weight heparins (LMWH), which may potentially be useful for long-term anticoagulation in hemodialysis patients. In atrial fibrillation the available data on risk of bleeding, risk of stroke, and patient preferences should all be taken into account when considering long-term anticoagulation. We have constructed an evidence model to help quantitate the risks and benefits for an individual patient. The impact of dialysis on risk of bleeding is such that the risk of bleeding will outweigh the benefit in many patients, and anticoagulation will not be used: in some of these patients aspirin therapy may be an alternative. Finally, in the area of prevention of graft and access thrombosis, some randomized controlled trials are available, but none have to date shown benefit from anticoagulation for primary or secondary prevention of thrombosis, and the risk of bleeding in these studies was high.

Intermittent saline flushes during haemodialysis do not alleviate coagulation and clot formation in stable patients receiving reduced doses of dalteparin

BACKGROUND

Heparin-free haemodialysis (HD) with intermittent saline flushes (ISF) in patients with bleeding risk is widely used. The aim of this study was to investigate if ISF reduce coagulation and clotting in stable patients receiving reduced doses of dalteparin.

METHODS

Inclusion criteria were stable chronic HD patients >or=18 years of age and haemoglobin >or=11 g/dl. Exclusion criteria were use of warfarin and acetylsalicylic acid. Six HD sessions were evaluated per patient. Dalteparin was given as one bolus dose at start of HD (50% of the conventional dose). In HD number 1, 3 and 5, 100 ml saline solution was flushed through the filter each 30 min. In HD 2, 4 and 6, no ISF were given. Potential clotting in the bubble trap was visually observed each hour and graded on a 4-point scale: 1 = normal, 2 = fibrinous ring, 3 = clot formation and 4 = coagulated system. The dialyser was visually inspected at the end of each session: 1 = normal, 2 = a few blood stripes (affecting less than 5% of the surface fibres), 3 = many blood stripes (more than 5% of the fibres) and 4 = coagulated filter. The coagulation marker PF1+2, the platelet activation marker beta-TG and anti-FXa activity were repeatedly measured during HD.

RESULTS

Six men and two women were included. In four cases (four different patients), HD was stopped due to a coagulated system, all cases on days with ISF performed. Multiple linear regression analyses with repeated measurements showed that ISF adjusted for dalteparin dose/kg significantly increased mean clot in the bubble trap, estimate (B) = 0.717, P = 0.0001 and also showed that ISF increased PF1+2, B = 0.16, P = 0.001 when adjusted for anti-FXa activity and hours of dialysis, whereas beta-TG was only borderline increased, B = 0.09, P = 0.055.

CONCLUSIONS

ISF during HD does not alleviate visible clotting or intravascular coagulation activity in stable patients receiving reduced doses of dalteparin and polysulphone dialysers. Whether this applies to unstable patients with increased bleeding risk not receiving any anticoagulation remains to be shown.

The effect of oral anticoagulation on clotting during hemodialysis

BACKGROUND

Between 5% and 10% of hemodialysis patients are treated with oral anticoagulants. It is currently unknown whether additional anticoagulation with heparin or low-molecular-weight heparin (LMWH) is needed to prevent clotting during hemodialysis.

METHODS

In this prospective, randomized, cross-over study 10 patients treated with oral anticoagulants (phenprocoumon) received either no additional anticoagulation or low dose dalteparin (bolus of 40 IU/kg body weight) before dialysis. Efficacy of hemodialysis was measured by normalized weekly Kt/V and urea reduction rate (URR). Thrombus formation was evaluated by measurement of D-dimer and inspection of air traps and dialyser.

RESULTS

The median international normalized ratio (INR) did not differ between both observation periods (phenprocoumon 2.2(2 to 3) vs. dalteparin 2.1(2 to 2.9). The anti-Xa level in dalteparin patients was 0.33 (0.27 to 0.38) IU/mL after 2 hours and 0.16 (0.03 to 0.23) IU/mL after 4 hours of hemodialysis. The median increase of D-dimer was significantly higher in patients without additional dalteparin therapy during hemodialysis (DeltaD-dimer 0.23 microg/mL vs. 0.03 mug/mL) (P= 0.0004). Complete thrombosis of the dialyser membrane occurred in one patient in the phenprocoumon group but in none with combined treatment. The extent of thrombosis in the arterial and venous air trap and dialyser was significantly less in patients with additional dalteparin therapy (P= 0.0014, P= 0.0002, and P= 0.0005, respectively). Weekly Kt/V and URR was similar in both groups.

CONCLUSION

Standard oral anticoagulation with an INR between 2 and 3 is insufficient to prevent clotting during hemodialysis. Additional low dose anticoagulation with a LMWH or heparin is necessary to facilitate treatment.

Assessment of Heparin Binding to the AN69 ST Hemodialysis Membrane: I. Preclinical Studies

The AN69 ST membrane was designed to render the surface of the native polyacrylonitrile polymer less cationic. This was achieved by layering the membrane with the polycationic biopolymer polyethyleneimine. This new membrane is able to bind heparin to its surface, through electrical interactions, without altering the reactivity of the sulfonate groups of the membrane, regularly distributed in the membrane bulk. The kinetics of unfractionated or low-molecular-weight heparins were studied in vitro and in vivo in sheep. Encouraging results were obtained indicating that heparin-coated hemodialyzers are potent anticoagulants. Priming the AN69 ST membrane-equipped hemodialyzer with heparin, as in regular hemodialysis, could allow drastic reduction of heparin consumption in hemodialysis.

Coagulation cascade activation causes CC chemokine receptor-2 gene expression and mononuclear cell activation in hemodialysis patients

Priming of the coagulation cascade during hemodialysis (HD) leads to the release of activated factor X (FXa). The binding of FXa to its specific receptors, effector protease receptor-1 (EPR-1) and protease-activated receptor-2 (PAR-2), may induce the activation of peripheral blood mononuclear cells (PBMC) and promote a chronic inflammatory state that is responsible for several HD-related morbidities. In the attempt to elucidate the mechanisms underlying the coagulation-associated inflammation in HD, 10 HD patients were randomized to be treated subsequently with a cellulose acetate membrane (CA) and Ethylen-vinyl-alcohol (EVAL), a synthetic membrane that has been shown to reduce FXa generation. At the end of each experimental period, surface FXa and thrombin receptors (EPR-1 and PAR-1, -2, and -4) and CCR2 (monocyte chemoattractant protein-1 receptor) gene expression in isolated PBMC were examined. the ability of dialytic membranes to activate protein-tyrosine kinases and the stress-activated kinase JNK and to modulate the generation of terminal complement complex (TCC) was also investigated. EPR-1 and PAR-2 and -4 mRNA expression, barely detectable in normal PBMC, were significantly upregulated in HD patients, particularly in those who were treated with CA. A striking increase of tyrosine-phosphorylated proteins and JNK activation was observed at the end of HD only in CA-treated patients. Simultaneously, an increased gene expression for both splicing isoforms of CCR2, A and B, only in PBMC from CA-treated patients was demonstrated. The increased CCR-2 mRNA abundance was followed by a significant increase in its protein synthesis. The high expression of CCR2 was associated with an increased generation of plasma TCC and a significant drop in leukocyte and monocyte count. By contrast, EVAL treatment slightly lowered TCC generation and normalized leukocyte count. In vitro FXa induced CCR2 A and B expression and JNK activation in freshly isolated PBMC. FXa-induced CCR2 mRNA expression was completely abolished by JNK and tyrosine kinase inhibition. In conclusion, these data suggest that subclinical clotting activation may cause an increased CCR2 gene and protein expression on uremic PBMC, contributing to HD-related chronic microinflammation. The use of the less coagulation-activating membrane, EVAL, may reduce PBMC activation through the modulation of the stress-activated kinase JNK.

Comparison of effects of different heparins on thrombin activatable fibrinolysis inhibitor in hemodialyzed patients

BACKGROUND

Thrombin activatable fibrinolysis inhibitor (TAFI) is a regulator of endogenous fibrinolysis. Heparin is used routinely during dialysis sessions to prevent clot formation in the extracorporeal circuit; therefore the aim of the study was to assess whether unfractionated heparin or low-molecular-weight heparins affect TAFI concentration and activity in hemodialyzed patients.

METHODS

Dalteparin (n = 16) or enoxaparin (n = 25) were administered before the second hemodialysis session in the week in a single dose, whereas unfractionated heparin (n = 18) was given first as a bolus, then in a pump. We also evaluated thrombin activity (thrombin-antithrombin complexes, prothrombin fragments 1 + 2), TAFI activator, thrombomodulin, a catalyzer of TAFI activation and a marker of endothelial cell injury, and the degree of plasmin generation (plasmin-antiplasmin complexes).

RESULTS

TAFI concentration, activity and markers of ongoing coagulation, i.e. prothrombin fragments 1 + 2 and thrombin-antithrombin complexes, were significantly higher in patients anticoagulated with unfractionated heparin when compared to both enoxaparin and dalteparin groups. Thrombin-antithrombin complexes, plasmin-antiplasmin complexes, prothrombin fragments 1 + 2, and thrombomodulin did not differ between patients anticoagulated with dalteparin and enoxaparin.

CONCLUSIONS

Our results suggest that low-molecular-weight heparins influence TAFI and other hemostatic parameters in hemodialyzed patients to a lesser degree than unfractionated heparin. Increased TAFI is possibly due to thrombin appearance during hemodialysis with unfractionated heparin.

Different effects of enoxaparin and unfractionated heparin on extrinsic blood coagulation during haemodialysis: a prospective study

BACKGROUND

Heparin inhibits prothrombotic tissue factor (TF) and releases its inhibitor, tissue factor pathway inhibitor (TFPI), from the endothelium, but repeated administration of heparin depletes vascular stores of TFPI. We studied the anticoagulant effects of unfractionated heparin (UFH) vs low-molecular-weight enoxaparin-used for thrice-weekly maintenance haemodialysis (HD)-on plasma levels of total TF and TFPI and on those of an activated coagulation marker prothrombin fragment 1+2 (PF 1+2).

METHODS

Twenty-five patients dialysed using a single injection of enoxaparin (at a mean dose of 0.68 mg/kg) were randomly assigned to either receive UFH administered as a mean bolus of 42.1 IU/kg and continuous infusion of 57.8 IU/kg (n=12) or to be maintained on enoxaparin (n=13), and were followed prospectively for 12 weeks. Plasma immunoreactive TF, TFPI and PF 1+2 were measured at the start and after 10 and 180 min of HD, and compared with values in 15 healthy controls.

RESULTS

Pre-dialysis TF, TFPI and PF 1+2 were higher than normal (all P<0.0001). TF and PF 1+2 did not change, while TFPI levels, compared with baseline, increased at each interval in enoxaparin-anticoagulated HD patients (all P<0.0001). TFPI increments correlated inversely with pre-dialysis TFPI (both P<0.0007). In patients switched to UFH, TF levels remained unchanged compared with pre-randomization values, TFPI increased at each interval of HD sessions (all P<0.035) and PF 1+2 increased pre-dialysis (P=0.015). The over-dialysis effects of UFH resembled those of enoxaparin. In contrast, baseline TFPI and its 10-min rise correlated inversely with the UFH loading dose (both P<0.040). Pre-dialysis PF 1+2 was inversely associated with TFPI increments (both P<0.034), and directly with pre-dialysis TFPI (P=0.018) and the UFH loading dose (P=0.045).

CONCLUSIONS

Depletion of heparin-releasable stores of TFPI is an untoward effect of repeated anticoagulation during maintenance HD therapy. The traditional UFH regimen is more prothrombotic than single enoxaparin injections, with high loading doses of UFH being involved in TFPI exhaustion and subsequent hypercoagulability.