Heparins and blood polymorphonuclear stimulation in haemodialysis: an expansion of the biocompatibility concept

Anticoagulation for people receiving long-term haemodialysis

BACKGROUND

Haemodialysis (HD) requires safe and effective anticoagulation to prevent clot formation within the extracorporeal circuit during dialysis treatments to enable adequate dialysis and minimise adverse events, including major bleeding. Low molecular weight heparin (LMWH) may provide a more predictable dose, reliable anticoagulant effects and be simpler to administer than unfractionated heparin (UFH) for HD anticoagulation, but may accumulate in the kidneys and lead to bleeding.

OBJECTIVES

To assess the efficacy and safety of anticoagulation strategies (including both heparin and non-heparin drugs) for long-term HD in people with kidney failure. Any intervention preventing clotting within the extracorporeal circuit without establishing anticoagulation within the patient, such as regional citrate, citrate enriched dialysate, heparin-coated dialysers, pre-dilution haemodiafiltration (HDF), and saline flushes were also included.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to November 2023 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-randomised controlled studies (quasi-RCTs) evaluating anticoagulant agents administered during HD treatment in adults and children with kidney failure.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias using the Cochrane tool and extracted data. Treatment effects were estimated using random effects meta-analysis and expressed as relative risk (RR) or mean difference (MD) with 95% confidence intervals (CI). Evidence certainty was assessed using the Grading of Recommendation, Assessment, Development and Evaluation approach (GRADE).

MAIN RESULTS

We included 113 studies randomising 4535 participants. The risk of bias in each study was adjudicated as high or unclear for most risk domains. Compared to UFH, LMWH had uncertain effects on extracorporeal circuit thrombosis (3 studies, 91 participants: RR 1.58, 95% CI 0.46 to 5.42; I2 = 8%; low certainty evidence), while major bleeding and minor bleeding were not adequately reported. Regional citrate anticoagulation may lower the risk of minor bleeding compared to UFH (2 studies, 82 participants: RR 0.34, 95% CI 0.14 to 0.85; I2 = 0%; low certainty evidence). No studies reported data comparing regional citrate to UFH on risks of extracorporeal circuit thrombosis and major bleeding. The effects of very LMWH, danaparoid, prostacyclin, direct thrombin inhibitors, factor XI inhibitors or heparin-grafted membranes were uncertain due to insufficient data. The effects of different LMWH, different doses of LMWH, and the administration of LMWH anticoagulants using inlet versus outlet bloodline or bolus versus infusion were uncertain. Evidence to compare citrate to another citrate or control was scant. The effects of UFH compared to no anticoagulant therapy or different doses of UFH were uncertain. Death, dialysis vascular access outcomes, blood transfusions, measures of anticoagulation effect, and costs of interventions were rarely reported. No studies evaluated the effects of treatment on non-fatal myocardial infarction, non-fatal stroke and hospital admissions. Adverse events were inconsistently and rarely reported.

AUTHORS' CONCLUSIONS

Anticoagulant strategies, including UFH and LMWH, have uncertain comparative risks on extracorporeal circuit thrombosis, while major bleeding and minor bleeding were not adequately reported. Regional citrate may decrease minor bleeding, but the effects on major bleeding and extracorporeal circuit thrombosis were not reported. Evidence supporting clinical decision-making for different forms of anticoagulant strategies for HD is of low and very low certainty, as available studies have not been designed to measure treatment effects on important clinical outcomes.

The effects of citrate dialysate in hemodialysis on polymorphonuclear elastase interaction with tissue factor and its inhibitor

BACKGROUND

This study aimed to investigate whether hemodialysis (HD) affects tissue factor (TF), tissue factor pathway inhibitor (TFPI), and polymorphonuclear elastase (PMNE) in endstage renal disease (ESRD) patients when eliminating the effects of heparin. Also, to explore the interaction of TF, TFPI, and PMNE throughout a single HD session.

METHODS

We enrolled 57 ESRD patients who had undergone hemodialysis for >3 months as an experimental group. Plasma levels of TF, TFPI and PMNE were measured by ELISA in 24 ERSD patients on intermittent HD using low-molecular-weight heparin (LMWH) as anticoagulation (LMWH group) and 33 ESRD patients using citrate as anticoagulation (citrate group) at the start and at 1, 2 and 5 h of the HD session. Meanwhile,28 ESRD patients not on dialysis were enrolled as a control group and fasting venous blood samples were taken in the morning.

RESULTS

Compared with the control group, the plasma TFPI levels of the LMWH group and the citrate group were significantly higher (P=0.000, P=0.002, respectively) under baseline conditions as well as the plasma PMNE levels (P=0.001, P=0.02, respectively), whereas TF showed no difference (P=0.186). During HD with citrate, plasma TFPI decreased slightly (P=0.012) and PMNE increased significantly (P=0.008) at 1 h. The plasma TFPI levels of the citrate group correlate with PMNE at 2 and 5 h (P=0.001, P=0.008, respectively).

CONCLUSIONS

ESRD patients on HD have significantly higher TFPI and PMNE levels compared to patients not on HD under baseline conditions, while TF levels were similar between the three groups. TFPI and PMNE are differently regulated, but the plasma levels correlated during HD in the citrate group. It might be possible that PMNE plays a role in anticoagulative activity through TFPI.

Citrate confers less filter-induced complement activation and neutrophil degranulation than heparin when used for anticoagulation during continuous venovenous haemofiltration in critically ill patients

Background

During continuous venovenous haemofiltration (CVVH), regional anticoagulation with citrate may be superior to heparin in terms of biocompatibility, since heparin as opposed to citrate may activate complement (reflected by circulating C5a) and induce neutrophil degranulation in the filter and myeloperoxidase (MPO) release from endothelium.

Methods

No anticoagulation (n = 13), unfractionated heparin (n = 8) and trisodium citrate (n = 17) regimens during CVVH were compared. Blood samples were collected pre- and postfilter; C5a, elastase and MPO were determined by ELISA. Additionally, C5a was also measured in the ultrafiltrate.

Results

In the heparin group, there was C5a production across the filter which most decreased over time as compared to other groups (P = 0.007). There was also net production of elastase and MPO across the filter during heparin anticoagulation (P = 0.049 or lower), while production was minimal and absent in the no anticoagulation and citrate group, respectively. During heparin anticoagulation, plasma concentrations of MPO at the inlet increased in the first 10 minutes of CVVH (P = 0.024).

Conclusion

Citrate confers less filter-induced, potentially harmful complement activation and neutrophil degranulation and less endothelial activation than heparin when used for anticoagulation during continuous venovenous haemofiltration in critically ill patients.

Clinical review: anticoagulation for continuous renal replacement therapy--heparin or citrate?

Heparin is the most commonly prescribed anticoagulant for continuous renal replacement therapy. There is, however, increasing evidence questioning its safety, particularly in the critically ill. Heparin mainly confers its anticoagulant effect by binding to antithrombin. Heparin binds to numerous other proteins and cells as well, however, compromising its efficacy and safety. Owing to antithrombin consumption and degradation, and to the binding of heparin to acute phase proteins, and to apoptotic and necrotic cells, critical illness confers heparin resistance. The nonspecific binding of heparin further leads to an unpredictable interference with inflammation pathways, microcirculation and phagocytotic clearance of dead cells, with possible deleterious consequences for patients with sepsis and systemic inflammation. Regional anticoagulation with citrate does not increase the patient's risk of bleeding. The benefits of citrate further include a longer or similar circuit life, and possibly better patient and kidney survival. This needs to be confirmed in larger randomized controlled multicenter trials. The use of citrate might be associated with less inflammation and has useful bio-energetic implications. Citrate can, however, with inadequate use cause metabolic derangements. Full advantages of citrate can only be realized if its risks are well controlled. These observations suggest a greater role for citrate.

Clinical review: Patency of the circuit in continuous renal replacement therapy

Premature circuit clotting is a major problem in daily practice of continuous renal replacement therapy (CRRT), increasing blood loss, workload, and costs. Early clotting is related to bioincompatibility, critical illness, vascular access, CRRT circuit, and modality. This review discusses non-anticoagulant and anticoagulant measures to prevent circuit failure. These measures include optimization of the catheter (inner diameter, pattern of flow, and position), the settings of CRRT (partial predilution and individualized control of filtration fraction), and the training of nurses. In addition, anticoagulation is generally required. Systemic anticoagulation interferes with plasmatic coagulation, platelet activation, or both and should be kept at a low dose to mitigate bleeding complications. Regional anticoagulation with citrate emerges as the most promising method.

Assessment of the Heparin-Binding AN69 ST Hemodialysis Membrane: II. Clinical Studies without Heparin Administration

Binding polyanionic unfractionated heparin over the modified AN69 polyacrylonitrile membrane, the surface electronegativity of which has been neutralized by polyethyleneimine (AN69-ST), renders the membrane more hemocompatible. This property was tested in two groups of long-term hemodialysis patients. Results were rated as massive or partial clotting of a dialyzer at the end of the session. Group I patients were included in a prospective, cross-over study comparing standard dialysis with hemodialysis without systemic administration of unfractionated heparin (n = 12, 123 sessions). In all instances, priming was made with 2 I saline containing 5,000 IU/l heparin. Only patchy or partial clotting was observed in 11% and 39% of the sessions with standard and heparin-free administration, respectively. Group II patients were included in an open, observational pilot study testing the effects of the heparin-coated membrane, without systemic administration of heparin, in patients at high risk of bleeding (n = 68, 331 sessions). Massive clotting was observed in six sessions only (less than 2%) and normal or slightly patchy dialyzers were found in 88% of the sessions. It is concluded that the dialysis AN69 ST membrane, after adequate priming at bedside, can be used without systemic administration of heparin for hemodialysis in patients at high risk of bleeding.

Safety and Efficacy of Single Bolus Anticoagulation with Enoxaparin for Chronic Hemodialysis. Results of an Open-Label Post-Certification Study

BACKGROUND

Low-molecular-weight heparin (LMWH) is supposed to be advantageous compared to unfractionated heparin for chronic hemodialysis (HD) with respect to lipid and bone metabolism, polymorphonuclear cell stimulation, induction of antibody-mediated thrombocytopenia, and aldosterone suppression. Due to longer biological half-life, LMWH offers the possibility of single bolus administration.

METHODS

To assess safety and efficacy of single bolus anticoagulation with enoxaparin for chronic HD, 781 stable HD patients from 79 German dialysis centers (mean age 62 years; 31% ESRD due to diabetes mellitus) were monitored by clinical and laboratory parameters for 32 weeks. Additionally, in a single dialysis center, 22 chronic HD patients were investigated by molecular markers of coagulation during chronic HD under conditions of single bolus or continuous anticoagulation regimens. Anti-Xa activity and the thrombin- antithrombin-III complex (TAT) were determined before the enoxaparin bolus, after 15 min, 2 h, and at the end of HD in venous and arterial blood lines.

RESULTS

Chronic HD was performed in 24,117 HD treatments with enoxaparin at a median dose of 70.1 IU/kg (5,000 IU median total dose) for single bolus anticoagulation. In 83.0% of HD treatments, enoxaparin was given as single bolus. In 98.3% of patients no adverse event was reported. No drug-related severe adverse event occurred. Significant clotting problems were observed in only 0.3% of HD treatments with single bolus anticoagulation. As assessed in 257 HD treatments, essentially identical anti-Xa levels were detected at the end of HD with single bolus (50 IU/kg) or continuous (mean total dose 43 IU/kg) anticoagulation regimens. Bolus anticoagulation resulted in higher TAT generation at the end of HD. However, this was not associated with increased macroscopic clot formation.

CONCLUSION

Single bolus anticoagulation with enoxaparin was safe and effective for chronic HD. For a duration of 4 h HD, a median dose of 70 IU/kg can be recommended for regular use, which is in accordance with the manufacturer's instructions for use of enoxaparin recommending a range of 50-100 IU/kg.

Regional anticoagulation with acid citrate dextrose-A for extracorporeal photoimmunochemotherapy

BACKGROUND AND OBJECTIVES

During photopheresis, intravenous heparin is used to prevent clotting in the extracorporeal circuit. Regional citrate anticoagulation could lower the risks associated with heparin treatment.

MATERIALS AND METHODS

Four-hundred and six photophereses procedures that were anticoagulated by acid citrate dextrose-A (ACD-A) (of which 343 were performed in patients at risk for haemorrhage) were analysed together with 278 heparin-anticoagulated treatments.

RESULTS

Four-hundred and four of 406 citrate treatments were completed. Seven transient paresthesias (1.73%), five of which occurred in the first 50 treatments, were observed. Bleeding complications were noted during heparin anticoagulation (1.07%), but not during citrate anticoagulation. During photopheresis, haemoglobin values and platelet counts decreased by 11.4% and 14.6%, respectively (P < 0.0001). Twenty-four hours after treatment, haemoglobin values, and platelet and leucocyte counts were still lower than at baseline (P < 0.0001). The changes of haemoglobin, platelet and leucocyte values did not differ for citrate and heparin.

CONCLUSIONS

In patients with contraindications against heparin use, ACD-A citrate anticoagulation during photopheresis is a safe and efficient alternative. Photopheresis induces profound changes of the blood count, irrespective of the anticoagulation method.