Does the surface-treated AN69 membrane prolong filter survival in CRRT without anticoagulation?

How to safeguard the continuous renal replacement therapy circuit: a narrative review

The high prevalence of acute kidney injury (AKI) in ICU patients emphasizes the need to understand factors influencing continuous renal replacement therapy (CRRT) circuit lifespan for optimal outcomes. This review examines key pharmacological interventions-citrate (especially in regional citrate anticoagulation), unfractionated heparin (UFH), low molecular weight heparin (LMWH), and nafamostat mesylate (NM)-and their effects on filter longevity. Citrate shows efficacy with lower bleeding risks, while UFH remains cost-effective, particularly in COVID-19 cases. LMWH is effective but associated with higher bleeding risks. NM is promising for high-bleeding risk scenarios. The review advocates for non-tunneled, non-cuffed temporary catheters, especially bedside-inserted ones, and discusses the advantages of surface-modified dual-lumen catheters. Material composition, such as polysulfone membranes, impacts filter lifespan. The choice of treatment modality, such as Continuous Veno-Venous Hemodialysis (CVVHD) or Continuous Veno-Venous Hemofiltration with Dialysis (CVVHDF), along with the management of effluent volume, blood flow rates, and downtime, are critical in prolonging filter longevity in CRRT. Patient-specific conditions, particularly the type of underlying disease, and the implementation of early mobilization strategies during CRRT are identified as influential factors that can extend the lifespan of CRRT filters. In conclusion, this review offers insights into factors influencing CRRT circuit longevity, supporting evidence-based practices and suggesting further multicenter studies to guide ICU clinical decisions.

Solute Clearance Evaluation and Filter Clotting Prediction in Continuous Renal Replacement Therapy

Unexpected filter clotting is a major problem in continuous renal replacement therapy (CRRT). Reduced solute clearance is observed prior to filter clotting. This single-center, retrospective, observational study aimed to determine whether reduced solute clearance of low- and medium-molecular-weight molecules in CRRT can predict filter clotting. Solute clearances of urea and myoglobin (Mb) were measured at 24 h after initiation of continuous hemodiafiltration (CHDF). Clearance per flow (CL/F) was calculated. The primary outcome was clotting of the filter in the subsequent 24 h, and 775 CHDF treatments conducted on 230 patients for at least 24 consecutive hours in our ICU were analyzed. Filter clotting was observed in 127 treatments involving 39 patients. Urea and Mb CL/F at 24 h were significantly lower in the patients who experienced clotting. Further analysis was limited to the first CHDF treatment of each patient to adjust for confounding factors. Multivariate logistic regression analysis revealed that both urea CL/F < 94% and Mb CL/F < 64% were significant predictors of clotting within the next 24 h. Lower urea and Mb CL/F measured at 24 h after CRRT initiation were associated with filter clotting in the next 24 h. Further study is necessary to ascertain whether measurement of urea and MB CL/F will help with avoiding unexpected filter clotting.

Effect of Dynamic Circuit Pressures Monitoring on the Lifespan of Extracorporeal Circuit and the Efficiency of Solute Removal During Continuous Renal Replacement Therapy

Objective: To observe the effects of dynamic pressure monitoring on the lifespan of the extracorporeal circuit and the efficiency of solute removal during continuous renal replacement therapy (CRRT).

Materials and Methods: A prospective observational study was performed at the West China Hospital of Sichuan University in the ICU. Analyses of the downloaded pressure data recorded by CRRT machines and the solute removal efficiencies, calculated by 2^*Ce/(Cpre+Cpost), where Ce, Cpre, and Cpost are the concentrations of the effluent, pre-filter blood, and post-filter blood, respectively, were performed. Samples were collected at 0, 2, 6, 12, and 24 h when continuous veno-venous hemodiafiltration (CVVHDF) was used after the initiation of CRRT. Measurements in concentrations of creatinine, blood urea nitrogen, and β2-microglobulin in the plasma and effluent were recorded.

Results: Extracorporeal circuits characterized by moderate-to-severe (M–S) access outflow dysfunction (AOD) events, defined as access outflow pressure less than or equal to −200 mmHg for more than 5 min, had shorter median lifespans with no anticoagulation (32.3 vs. 10.90 h, P = 0.001) compared with the no M–S AOD events group. The significant outcome also existed in regional citrate anticoagulation (RCA) (72 vs. 42.47 h, P = 0.02). Moreover, Cox regression analysis revealed that the lack of M–S AOD events, RCA, or CVVHDF independently prolonged the circuit lifespan. All tested solutes removal efficiencies started to decline at 12 h. Furthermore, efficiencies of all solutes removal dropped obviously at 24 h when TMP ≥ 150 mmHg.

Conclusion: RCA and CVVHDF predicted a longer circuit lifespan. M–S AOD events were associated with a shorter circuit lifespan when RCA or no anticoagulant was used. Replacement of extracorporeal circuit could be considered when running time of filter lasted up to 24 h with TMP ≥ 150 mmHg.

Non-pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement therapy

BACKGROUND

Acute kidney injury (AKI) is a common complication amongst people who are critically ill, and it is associated with an increased risk of death. For people with severe AKI, continuous kidney replacement therapy (CKRT), which is delivered over 24 hours, is needed when they become haemodynamically unstable. When CKRT is interrupted due to clotting of the extracorporeal circuit, the delivered dose is decreased and thus leading to undertreatment.

OBJECTIVES

This review assessed the efficacy of non-pharmacological measures to maintain circuit patency in CKRT.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 25 January 2021 which includes records identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) (parallel-group and cross-over studies), cluster RCTs and quasi-RCTs that examined non-pharmacological interventions to prevent clotting of extracorporeal circuits during CKRT.  DATA COLLECTION AND ANALYSIS: Three pairs of review authors independently extracted information including participants, interventions/comparators, outcomes, study methods, and risk of bias. The primary outcomes were circuit lifespan and death due to any cause at day 28. We used a random-effects model to perform quantitative synthesis (meta-analysis). We assessed risk of bias in included studies using the Cochrane Collaboration's tool for assessing risk of bias. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

A total of 20 studies involving 1143 randomised participants were included in the review. The methodological quality of the included studies was low, mainly due to the unclear randomisation process and blinding of the intervention. We found evidence on the following 11 comparisons: (i) continuous venovenous haemodialysis (CVVHD) versus continuous venovenous haemofiltration (CVVH) or continuous venovenous haemodiafiltration (CVVHDF); (ii) CVVHDF versus CVVH; (iii) higher blood flow (≥ 250 mL/minute) versus standard blood flow (< 250 mL/minute); (iv) AN69 membrane (AN69ST) versus other membranes; (v) pre-dilution versus post-dilution; (vi) a longer catheter (> 20 cm) placing the tip targeting the right atrium versus a shorter catheter (≤ 20 cm) placing the tip in the superior vena cava; (vii) surface-modified double-lumen catheter versus standard double-lumen catheter with identical geometry and flow design; (viii) single-site infusion anticoagulation versus double-site infusion anticoagulation; (ix) flat plate filter versus hollow fibre filter of the same membrane type; (x) a filter with a larger membrane surface area versus a smaller one; and (xi) a filter with more and shorter hollow fibre versus a standard filter of the same membrane type. Circuit lifespan was reported in 9 comparisons. Low certainty evidence indicated that CVVHDF (versus CVVH: MD 10.15 hours, 95% CI 5.15 to 15.15; 1 study, 62 circuits), pre-dilution haemofiltration (versus post-dilution haemofiltration: MD 9.34 hours, 95% CI -2.60 to 21.29; 2 studies, 47 circuits; I² = 13%), placing the tip of a longer catheter targeting the right atrium (versus placing a shorter catheter targeting the tip in the superior vena cava: MD 6.50 hours, 95% CI 1.48 to 11.52; 1 study, 420 circuits), and surface-modified double-lumen catheter (versus standard double-lumen catheter: MD 16.00 hours, 95% CI 13.49 to 18.51; 1 study, 262 circuits) may prolong circuit lifespan. However, higher blood flow may not increase circuit lifespan (versus standard blood flow: MD 0.64, 95% CI -3.37 to 4.64; 2 studies, 499 circuits; I² = 70%). More and shorter hollow fibre filters (versus standard filters: MD -5.87 hours, 95% CI -10.18 to -1.56; 1 study, 6 circuits) may reduce circuit lifespan. Death from any cause was reported in four comparisons We are uncertain whether CVVHDF versus CVVH, CVVHD versus CVVH or CVVHDF, longer versus a shorter catheter, or surface-modified double-lumen catheters versus standard double-lumen catheters reduced death due to any cause, in very low certainty evidence. Recovery of kidney function was reported in three comparisons. We are uncertain whether CVVHDF versus CVVH, CVVHDF versus CVVH, or surface-modified double-lumen catheters versus standard double-lumen catheters increased recovery of kidney function. Vascular access complications were reported in two comparisons. Low certainty evidence indicated using a longer catheter (versus a shorter catheter: RR 0.40, 95% CI 0.22 to 0.74) may reduce vascular access complications, however the use of surface-modified double lumen catheters versus standard double-lumen catheters may make little or no difference to vascular access complications.

AUTHORS' CONCLUSIONS

The use of CVVHDF as compared with CVVH, pre-dilution haemofiltration, a longer catheter, and surface-modified double-lumen catheter may be useful in prolonging the circuit lifespan, while higher blood flow and more and shorter hollow fibre filter may reduce circuit life. The Overall, the certainty of evidence was assessed to be low to very low due to the small sample size of the included studies. Data from future rigorous and transparent research are much needed in order to fully understand the effects of non-pharmacological interventions in preventing circuit coagulation amongst people with AKI receiving CKRT.

Filter life and safety of heparin-grafted membrane for continuous renal replacement therapy - A randomized controlled trial

Polyethyleneimine-layered membrane with grafted heparin (oXiris) may improve filter life during continuous renal replacement therapy (CRRT) in addition to its immunoadsorptive capability, compared with that of conventional membrane. In this single center, prospective, open-label pilot study, we randomized critically ill patients with bleeding risk who underwent anticoagulation-free CRRT, to commence with oXiris or M150 filter with sequential crossover. We examined the filter life with each circuit and its effect on systemic coagulation parameters. We randomized 11 and nine patients to commence CRRT with oXiris and M150 respectively, with 19 oXiris and 20 M150 filter-circuits in all. Patient profiles in both arms were comparable for illness severity and comorbidities. Median filter lives for oXiris versus M150 circuits were 13 h versus 18 h (p = 0.10). Among 11 patients with paired crossover filters, filter lives for 14 oXiris-M150 circuit pairs were 13 h versus 16 h (p = 0.27), and corresponding transmembrane pressures increased to 111 mmHg versus 75 mmHg by 12 h (p = 0.02). Patients' coagulation parameters were comparable following both filter-circuits. CRRT with oXiris (vs. M150) was independently associated with shorter filter life, adjusted for prescribed dose, vascular access, and coagulopathy. Use of oXiris did not prolong filter life over conventional membrane with no evidence of systemic heparin exposure; significant membrane clogging is observed by 12 h with oXiris.

Comparison of the circulatory effects of continuous renal replacement therapy using AN69ST and polysulfone membranes in septic shock patients: A retrospective observational study

The acrylonitrile-co-methallyl sulfonate surface-treated (AN69ST) membrane is expected to improve hemodynamics in patients with sepsis through cytokine adsorption. However, the clinical literature on AN69ST membranes is very limited. We aimed to compare the circulatory effects of continuous renal replacement therapy (CRRT) between patients using the AN69ST membrane and polysulfone (PS) membrane (a nonadsorbing membrane). This retrospective observational study enrolled 38 patients with septic shock, as defined by Sepsis-3 criteria, who required CRRT from April 2013 to March 2018. Those who died within 24 hours after CRRT initiation and received polymyxin B-immobilized fiber column direct hemoperfusion, extracorporeal membrane oxygenation, and CRRT using other membranes were excluded. The primary outcome was the vasopressor dependency index during the 12 hours after CRRT initiation, which was calculated as (inotropic score)/(mean arterial pressure). Of 38 patients analyzed, 16 underwent CRRT with an AN69ST membrane and 22 with a PS membrane. The median patient age was 68 years, and the median Acute Physiology and Chronic Health Evaluation (APACHE) II score at intensive care unit admission was 29.5. The vasopressor dependency index decreased significantly during the 12 hours after CRRT initiation in both groups (AN69ST: from 0.50 ± 0.43 to 0.33 ± 0.27 [P < .05], PS: from 0.34 ± 0.30 to 0.21 ± 0.22 [P < .05]). The time course of the vasopressor dependency index during the 12 hours did not differ between the two groups (P = .11). The vasopressor dependency index decreased significantly after CRRT initiation in both groups. The time course of the vasopressor dependency index did not differ between the groups.

An update on membranes and cartridges for extracorporeal blood purification in sepsis and septic shock

PURPOSE OF REVIEW

This review aims to summarize the most recent advances on different membranes and cartridges used for extracorporeal blood purification in critically ill patients with sepsis or septic shock.

RECENT FINDINGS

Despite positive signals from experimental, cases and small clinical studies, blood purification showed no distinct morbidity and mortality benefit in large clinical trials.

SUMMARY

None of the discussed specific membranes or cartridges can currently be recommended as sole adjunctive treatment in sepsis and septic shock. Any available technique should be timely initiated and adapted to the patient's status. Sickest patients seem to benefit more from blood purification. Patient selection is thus of crucial importance and may be optimized by focusing on disease severity and degree of organ failure. Measurement of endotoxin activity and plasma procalcitonin levels can support the selection process but ideal cutoff values need to be defined. Well-designed prospective randomized clinical trials assessing or comparing the various available membranes and cartridges are eagerly awaited.

Antithrombotic properties of hemofilter coated with polymer having a hydrophilic blood-contacting layer

OBJECTIVE:

Extracorporeal circulation devices are coated with a biocompatible polymer coating agent (BPCA) that has a hydrophilic blood-contacting layer, but hemofilters are not. We aimed to investigate the antithrombotic properties of a BPCA-coated hemofilter.

METHODS:

Four experiments using BPCA-coated circuits and non-coated hemofilters and four experiments using BPCA-coated circuits and BPCA-coated hemofilters were performed with whole human blood and compared by measuring the circuit pressure every 5 min, antithrombin activity every 40 min, and thrombin-antithrombin complex every 40 min, for a total of 240 min of recirculation.

RESULTS:

The mean time required for the pressure at the inlet of the hemofilter to increase sharply was longer in BPCA-coated than in non-coated hemofilters (66 ± 11 min vs 25 ± 9 min, p < 0.01). The mean antithrombin activity value at 200 and 240 min of recirculation was significantly higher in the experiments with BPCA-coated versus non-coated hemofilters (43.3 ± 2.87 vs 33.3 ± 5.74, p = 0.04; 42.8 ± 3.59 vs 31.0 ± 5.35, p = 0.01, respectively); the antithrombin activity values at the other time points were not significantly different. Furthermore, all thrombin-antithrombin complex values in experiments with the BPCA-coated hemofilters achieved overrange at 80 min of recirculation, whereas those with the non-coated hemofilter achieved overrange at 40 min.

CONCLUSION:

This study suggests that BPCA-coated hemofilters can inhibit antithrombin consumption, contributing to antithrombotic effects in extracorporeal circulation circuits.

Micro-computed tomography for the quantification of blocked fibers in hemodialyzers

A novel technique based on micro-CT scanning is developed to quantify coagulation in fibers of hemodialyzers. This objectivation is needed to allow accurate assessment of thrombogenicity of dialyzers used during hemodialysis, for example when comparing different strategies to avoid coagulation and/or fiber blocking. The protocol allowed imaging at a resolution of 25 µm, making it possible to count the open, non-coagulated fibers in a non-invasive way. In 3 fresh, non-used FX600 hemodialyzers, patent fiber counts were extremely consistent (10748 ± 2). To illustrate the potential of this technique, different dialysis parameters currently used as surrogates for fiber blocking were evaluated during 20 hemodialysis sessions. After dialysis, the FX600 dialyzers were visually scored for clotting, dried and subsequently weighed and scanned. The number of patent fibers (10003 [8763,10330], range 534–10692) did not correlate with any of the recorded surrogate parameters. Micro-CT scanning is a feasible, objective, non-invasive, accurate and reproducible tool for quantification of the degree of fiber blocking in a hemodialyzer after use, making it a potential gold standard for use in studies on fiber blocking during renal replacement therapies.

Polyethyleneimine-treated polyacrylonitrile membrane hemofilter for critically ill patients receiving anticoagulant-free prolonged intermittent renal replacement therapy: a single-center, prospective, self-controlled pilot study

Background

Critically ill patients requiring renal replacement therapy (RRT) are at risk of disease-related bleeding. Systemic heparinization should be avoided. AN69ST, a polyethyleneimine-treated polyacrylonitrile (AN69) membrane hemofilter, can be primed with heparin, improving its local anticoagulative activity. Prolonged intermittent RRT (PI-RRT) is of shorter duration and cheaper, considered as an alternative to continuous RRT. This study was performed to compare the success rate of anticoagulant-free PI-RRT using AN69ST versus AN69 membrane hemofilter. We also evaluated risk factors for filter clotting.

Methods

This crossover, double-blind, randomized study included patients requiring PI-RRT but at high bleeding risk treated with AN69ST and AN69 hemo filters. The success rate of RRT, filter lifespan and severity of filter clotting were compared between the hemo filters. Factors associated with the filter clotting risk were analyzed with a Cox proportional hazards model.

Results

This study included 60 patients (mean age, 68.1 ± 15.8 years). Thirty-three (55.0%) patients were in the intensive care unit, 34 (56.8%) had disease-related thrombocytopenia, and 14 (23.3%) had local hemorrhagic diseases. The success rate of PI-RRT with the AN69ST and AN69 hemofilter was 51.7% and 50.9%, respectively (P > 0.05). The mean PI-RRT duration was 543.1 ± 119.0 min in the completed sessions and 387.3 ± 140.8 min in the prematurely terminated sessions, without significant difference between AN69ST and AN69 hemofilters. Cox regression analysis showed that age (odds ratio [OR], 1.023 per year), platelet count (OR, 1.07 per 10 × 10⁹/L), hemoglobin concentration (OR, 1.035 per 1 g/L), and activated partial thromboplastin time (aPTT; OR, 0.973 per second) were associated with a hemofilter clotting risk. The AN69ST hemofilter lifespan was significantly prolonged averaging an extra 251.7 min in patients with an aPTT of <35.3 s, hemoglobin concentration of >83 g/L and platelet count of <70 × 10⁹/L.

Conclusions

Anticoagulant-free PI-RRT by a heparin-primed AN69ST hemofilter reached a 51.7% success rate. The risk of premature clotting of the extracorporeal circuit remains unsatisfactory. For select patients at high risk of bleeding, the heparin-primed AN69ST hemofilter may be more appropriate for anticoagulation-free PI-RRT.

Trial registration

https://www.clinicaltrials.gov; study number: NCT02355873. Release Date 01/21/2015

Non anti-coagulant factors associated with filter life in continuous renal replacement therapy (CRRT): a systematic review and meta-analysis

BACKGROUND

Optimising filter life and performance efficiency in continuous renal replacement therapy has been a focus of considerable recent research. Larger high quality studies have predominantly focussed on optimal anticoagulation however CRRT is complex and filter life is also affected by vascular access, circuit and management factors. We performed a systematic search of the literature to identify and quantify the effect of vascular access, circuit and patient factors that affect filter life and presented the results as a meta-analysis.

METHODS

A systematic review and meta-analysis was performed by searching Pubmed (MEDLINE) and Ovid EMBASE libraries from inception to 29th February 2016 for all studies with a comparator or independent variable relating to CRRT circuits and reporting filter life. Included studies documented filter life in hours with a comparator other than anti-coagulation intervention. All studies comparing anticoagulation interventions were searched for regression or hazard models pertaining to other sources of variation in filter life.

RESULTS

Eight hundred nineteen abstracts were identified of which 364 were selected for full text analysis. 24 presented data on patient modifiers of circuit life, 14 on vascular access modifiers and 34 on circuit related factors. Risk of bias was high and findings are hypothesis generating. Ranking of vascular access site by filter longevity favours: tunnelled semi-permanent catheters, femoral, internal jugular and subclavian last. There is inconsistency in the difference reported between femoral and jugular catheters. Amongst published literature, modality of CRRT consistently favoured continuous veno-venous haemodiafiltration (CVVHD-F) with an associated 44% lower failure rate compared to CVVH. There was a trend favouring higher blood flow rates. There is insufficient data to determine advantages of haemofilter membranes. Patient factors associated with a statistically significant worsening of filter life included mechanical ventilation, elevated SOFA or LOD score, elevations in ionized calcium, elevated platelet count, red cell transfusion, platelet factor 4 (PF-4) antibodies, and elevated fibrinogen. Majority of studies are observational or report circuit factors in sub-analysis. Risk of bias is high and findings require targeted investigations to confirm.

CONCLUSION

The interaction of patient, pathology, anticoagulation, vascular access, circuit and staff factors contribute to CRRT filter life. There remains an ambiguity from published data as to which site and side should be the first choice for vascular access placement and what interaction this has with patient factors and timing. Early consideration of tunnelled semi-permanent access may provide optimal filter life if longer periods of CRRT are anticipated. There remains an absence of robust evidence outside of anti-coagulation strategies despite over 20 years of therapy delivery however trends favour CVVHD-F over CVVH.

Renal replacement therapy in adult and pediatric intensive care : Recommendations by an expert panel from the French Intensive Care Society (SRLF) with the French Society of Anesthesia Intensive Care (SFAR) French Group for Pediatric Intensive Care Emergencies (GFRUP) the French Dialysis Society (SFD)

Acute renal failure (ARF) in critically ill patients is currently very frequent and requires renal replacement therapy (RRT) in many patients. During the last 15 years, several studies have considered important issues regarding the use of RRT in ARF, like the time to initiate the therapy, the dialysis dose, the types of catheter, the choice of technique, and anticoagulation. However, despite an abundant literature, conflicting results do not provide evidence on RRT implementation. We present herein recommendations for the use of RRT in adult and pediatric intensive care developed with the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system by an expert group of French Intensive Care Society (SRLF), with the participation of the French Society of Anesthesia and Intensive Care (SFAR), the French Group for Pediatric Intensive Care and Emergencies (GFRUP), and the French Dialysis Society (SFD). The recommendations cover 4 fields: criteria for RRT initiation, technical aspects (access routes, membranes, anticoagulation, reverse osmosis water), practical aspects (choice of the method, peritoneal dialysis, dialysis dose, adjustments), and safety (procedures and training, dialysis catheter management, extracorporeal circuit set-up). These recommendations have been designed on a practical point of view to provide guidance for intensivists in their daily practice.

Practical considerations for the dosing and adjustment of continuous renal replacement therapy in the intensive care unit

Familiarity with the initiation, dosing, adjustment, and termination of continuous renal replacement therapy (CRRT) is a core skill for contemporary intensivists. Guidelines for how to administer CRRT in the intensive care unit are not well documented. The purpose of this review is to discuss the modalities, terminology, and components of CRRT, with an emphasis on the practical aspects of dosing, adjustments, and termination. Management of electrolyte and acid-base derangements commonly encountered with acute renal failure is emphasized. Knowledge regarding the practical aspects of managing CRRT in the intensive care unit is a prerequisite for achieving desired physiological end points.