A target-orientated algorithm for regional citrate-calcium anticoagulation in extracorporeal therapies

Segmental citrate anticoagulation for double-filtration plasmapheresis: A case report and literature review

Regional citrate anticoagulation (RCA) has been widely used in patients with high-risk bleeding for anticoagulation in renal replacement therapy. However, scientific reports on the use of RCA in double-filtration plasmapheresis (DFPP) are limited. In the available reports, anticoagulation was not performed in the plasma component separator. However, as demonstrated in the present study, during the treatment of a patient with anti-neutrophil cytoplasmic antibody-associated vasculitis, although RCA was used for DFPP, coagulation occurred in the plasma component separator, resulting in the interruption of treatment. Thus, segmental citrate anticoagulation (SCA) was used and the filter was successfully prevented from clotting again. The present study demonstrates that SCA can more effectively prevent the clogging of the plasma separator and the plasma component separator, thereby maintaining the continuity of treatment and avoiding treatment interruption.

A mathematical estimation for quantified calcium supplementation during intermittent hemodialysis using regional citrate anticoagulation

BACKGROUND

Regional citrate anticoagulation has been recommended as an alternative of anticoagulation for patients at high risk of bleeding undergoing intermittent hemodialysis. Precise calcium supplementation is important for the safety of regional citrate anticoagulation. In this study we aimed to develop a possible method to optimize calcium supplementation for regional citrate anticoagulation in intermittent hemodialysis.

METHODS

The investigation consisted of a pilot study and a validation study. 18 patients undergoing intermittent hemodialysis anticoagulated by citrate and Six types of filters were included in the pilot study. The ionized calcium levels were monitored and maintained in the targeted range. Calcium-free dialysate was used in the study. After linear regression analysis of the clearance of non-protein bound calcium and calculating the ratio of the non-protein bound calcium concentration to total calcium concentration, we developed a mathematical model for estimation of extracorporeal circuit calcium removal. Another 8 maintenance hemodialysis patients (12 sessions) were enrolled in the validation study to validate the new version of the calcium supplementation approach.

RESULTS

In the pilot study, positive correlations were found between the clearance of non-protein bound calcium and the hematocrit-adjusted clearance of creatinine and phosphate given in the dialyzer leaflet (R² =0.31, p=0.0165). The ratio of the non-protein bound calcium concentration to total calcium concentration at the pre-filter point after infusion of citrate were constant about 0.75. In the validation study, we found that the systemic ionized calcium levels were stably maintained in the safe range and no filter clotting occurred during the hemodialysis when we used the new model of calcium supplementation.

CONCLUSIONS

We developed a possible method to quantify calcium supplementation for intermittent hemodialysis anticoagulated by citrate which may help to avoid negative calcium balance and reduce the incidence of complications.

A target-oriented algorithm for maintaining serum calcium stability automatically in regional citrate anticoagulation

BACKGROUND

Regional citrate anticoagulation (RCA) for renal replacement therapy is widely practiced in critically ill patients. However, concern exists regarding its labor-intensiveness for monitoring and the associated hypocalcemia. In this study, we provided an algorithm for prescribing RCA and evaluated its safety in patients.

METHODS

During 18 hemofiltration treatments with calcium-free replacement solution, participants were randomized to receive algorithm-based or trial-and-error RCA protocol. The effluent volume, post-filter and in vivo ionized calcium (iCa), and calcium in the sera and effluents were periodically measured at an interval of 1 to 2 h.

RESULTS

For patients received algorithm-based RCA protocol, no one had a serum iCa less than 0.9 mmol/L, and none needed calcium supplement adjustment to maintain serum calcium stability. For patients accepted trial-and-error protocol, all patients had a serum iCa below 0.9 mmol/L, their serum iCa and calcium levels fluctuated dramatically, and all patients need additional calcium supplement adjustment during RCA. None of the participants showed a post-filter iCa > 0.4 mmol/L.

CONCLUSION

We provided a safe algorithm for calculating calcium supplementation doses that could maintain serum calcium stability without additional adjustment during RCA.

Optimized calcium supplementation approach in post-dilution CVVHDF using regional citrate anticoagulation

BACKGROUND

Regional citrate anticoagulation has been recommended as first choice for anticoagulation of continuous renal replacement therapy. Precise calcium supplementation is important for the safety of regional citrate anticoagulation. In this study we aimed to provide an optimized calcium supplementation approach for regional citrate anticoagulation in post-dilution continuous venous-venous hemodiafiltration.

METHODS

Twenty-seven patients receiving post-dilution continuous venous-venous hemodiafiltration anticoagulated by citrate were included in this study. The ionized calcium levels were monitored and maintained in the targeted range. After linear regression analysis of the clearance of non-protein bound calcium and calculating the ratio of the non-protein bound calcium concentration to total calcium concentration, we concluded the mathematical model for calcium supplementation.

RESULTS

Positive correlations were found between the clearance of non-protein bound calcium and both dialysate flow rates (r = 0.647, p < 0.001) and ultrafiltration plus substitution fluid flow rates (r = 0.525, p = 0.005). The ratio of the non-protein bound calcium concentration to total calcium concentration values at the pre-filter point after infusion of citrate were constant about 0.83. Based on the clearance and the calcium ratio, the amount of extracorporeal calcium removal can be estimated with a simplified equation.

CONCLUSIONS

We provided an optimized calcium supplementation approach for post-dilution continuous venous-venous hemodiafiltration anticoagulated by citrate which may help to estimate the amount of extracorporeal circuit removal of calcium with regard to different dosages of regional citrate anticoagulation.

Impact of anion exchange adsorbents on regional citrate anticoagulation

INTRODUCTION

Heparin and citrate are commonly used anticoagulants in membrane/adsorption based extracorporeal liver support systems. However, anion exchange resins employed for the removal of negatively charged target molecules including bilirubin may also deplete these anticoagulants due to their negative charge. The aim of this study was to evaluate the adsorption of citrate by anion exchange resins and the impact on extracorporeal Ca²⁺ concentrations.

METHODS

Liver support treatments were simulated in vitro. Citrate and Ca²⁺ concentrations were measured pre and post albumin filter as well as pre and post adsorbents. In addition, batch experiments were performed to quantify citrate adsorption.

RESULTS

Pre albumin filter target Ca²⁺ concentrations were reached well with only minor deviations. Citrate was adsorbed by anion exchange resins, resulting in a higher Ca²⁺ concentration downstream of the adsorbent cartridges during the first hour of treatment.

CONCLUSIONS

The anion exchange resin depletes citrate, leading to an increased Ca²⁺ concentration in the extracorporeal circuit, which may cause an increased risk of clotting during the first hour of treatment. An increase of citrate infusion during the first hour of treatment should therefore be considered to compensate for the adsorption of citrate.

Quantitative assessment of the anticoagulant in plasma units collected by plasmapheresis

BACKGROUND

To date, the quantification of the anticoagulant (ACD-A) in plasma units has been based on theoretical calculations. An accurate quantification could help minimize the risks associated with plasmapheresis, given that the total ACD-A used during the procedure is distributed between the donor and the plasma unit. Our aim was to experimentally quantify the volume of ACD-A in units collected by plasmapheresis.

STUDY DESIGN AND METHODS

We used proton nuclear magnetic resonance spectroscopy to measure the ACD-A volume in 295 plasma units collected by the Azienda USL-IRCCS of Reggio Emilia, Italy. We analyzed the determinants of the differences between estimated and measured ACD-A through multivariate regression models.

RESULTS

The experimentally measured ACD-A in plasma units was variable, with 45% of the samples showing a discrepancy of more than 15 mL compared to the manufacturer's estimate. ACD-A was underestimated for higher density of the units (p < 0.0005); a weak association was also observed with triglycerides (underestimated for higher levels, p = 0.015) and sex (overestimated in females, p = 0.008), but our model explained only 35% of the individual variability.

CONCLUSION

The manufacturer's algorithms do not accurately estimate the ACD-A in units collected by plasmapheresis. Donor-related characteristics may affect ACD-A distribution between donor and plasma unit, thereby explaining the discrepancies between estimate and measurement. Errors in the estimate of the ACD-A actually received by donors could hamper studies on dose-response relationship between anticoagulant and adverse reactions. Our work should stimulate research on tailored procedures aimed at minimizing the anticoagulant received by donors and increasing plasmapheresis safety.

An evaluation of four modes of low-dose anticoagulation during intermittent haemodialysis

Introduction

Intensive care participants that need dialysis frequently suffer from increased risk of bleeding. Standard intermittent haemodialysis (SHD) includes anticoagulation to avoid clotting of the dialysis system. The aim of this study was to clarify which of four different low-dose anticoagulant modes was preferable in reducing the exposure to i.v. unfractionated heparin (heparin) and maintaining patency of the dialysis circuit.

Methods

Twenty-three patients on SHD were included to perform haemodialysis with four modes of low-dose anticoagulation. For comparative analyses, patients served as their own control. Haemodialysis with a single bolus of tinzaparin at the start was compared to haemodialysis initiated without i.v. heparin but priming with (1) heparin in saline (H), (2) heparin and albumin in saline (HA), (3) heparin and albumin in combination with a citrate-containing dialysate (HAC), (4) saline and usinga heparin-coated filters (Evodial®). The priming fluid was discarded before dialysis started. Blood samples were collected at 0, 30 and 180 min during haemodialysis. Smaller bolus doses of heparin (500 Units/dose) were allowed during the modes to avoid interruption by clotting.

Findings

The mean activated partial thromboplastin (APTT) time as well as the doses of anticoagulation administered was highest with SHD and least with HAC and Evodial®. Mode H versus SHD had the highest rate of prematurely interrupted dialyses (33%, p = 0.008). The urea reduction rate was less with Evodial® vs. SHD (p < 0.01). One hypersensitivity reaction occurred with Evodial®. Changes in blood cell concentrations and triglycerides differed between the modes.

Discussion

If intermittent haemodialysis is necessary in patients at risk of bleeding, anticoagulation using HAC and Evodial® appeared most preferable with least administration of heparin, lowest APTT increase and lowest risk for prematurely clotted dialyzers in contrast to the least plausible H mode.

Electronic supplementary material

The online version of this article (10.1007/s00228-017-2389-x) contains supplementary material, which is available to authorized users.

Dialysis Procedures Alter Metabolic Conditions

A progressive chronic kidney disease results in retention of various substances that more or less contribute to dysfunction of various metabolic systems. The accumulated substances are denominated uremic toxins. Although many toxins remain undetected, numerous newly defined toxins participate in the disturbance of food breakdown. In addition, toxic effects may downregulate other pathways, resulting in a reduced ability of free fatty acid breakdown by lipoprotein lipase (LPL) and hepatic lipase (HL). Dialysis may even worsen metabolic functions. For LPL and HL, the use of heparin and low molecular weight heparin as anticoagulation during hemodialysis (HD) initiate a loss of these enzymes from their binding sites and degradation, causing a temporary dysregulation in triglyceride breakdown. This lack of function will cause retention of the triglyceride containing lipids for at least 8 h. In parallel, the breakdown into free fatty acids is limited, as is the energy supply by them. This is repeated thrice a week for a normal HD patient. In addition, dialysis will cause a loss of amino acids and disturb glucose metabolism depending on the dialysates used. The addition of glucose in the dialysate may support oxidation of carbohydrate and the retention of Amadori products and subsequent tissue alterations. To avoid these effects, it seems necessary to further study the effects of anticoagulation in HD, the extent of use of glucose in the dialysate, and the supplementation of amino acids.

Experiences with Continuous Venovenous Hemofiltration using 18mmol/L predilution Citrate anticoagulation and a Phosphate Containing Replacement Solution

CONTEXT

Regional citrate anticoagulation for continuous renal replacement therapy is associated with a longer filter-life, less bleeding events and improved mortality. Problems associated with using Prismocitrate 10/2 solution in continuous renal replacement therapy, include hypomagnesemia, hypophosphatemia and the need for additional bicarbonate infusion.

AIMS

This study uses the new Prismocitrate 18/0 solution for improved buffer balance and Phoxilium solution for a more favourable electrolyte profile.

SETTINGS AND DESIGN

A retrospective analysis of patients who underwent continuous venovenous hemofiltration (CVVH) using Prismocitrate 18/0 and Phoxilium in our 21-bed ICU was conducted from March to July 2014.

METHODS AND MATERIAL

Continuous venovenous hemofiltration (CVVH) was performed at fixed rate by using Prismocitrate 18/0 predilution at 1250 ml/hour, a blood flow rate of 110 ml/min and post-replacement with Phoxilium at 1250 ml/hr. CVVH was run for 72 h or until filter clotting, transportation, or achievement of the clinical target.

STATISTICAL ANALYSIS USED

The results were displayed as the median with the interquartile range (IQR). The trend in pH, electrolytes, and base excess are shown using a standard box plot. All analyses were performed by the Statistical Package for Social Science for Windows, version 17 (SPSS, Chicago, IL, USA).

RESULTS

Forty-five CVVH episodes were analysed. The median circuit lifetime was 44 h (interquartile range, IQR 29-55). Metabolic alkalosis, hypophosphatemia and hypomagnesemia occurred in 8.3%, 3.5% and 40.2% of the blood samples, respectively. No patient developed hypokalemia or citrate toxicity.

CONCLUSIONS

This new CVVH regime is safe and easy to administer for critically ill patients.

A prediction and simulation model for target-oriented regional citrate-calcium anticoagulation in extracorporeal blood purification

AIMS

Regional citrate-calcium anticoagulation is becoming more and more attractive for extracorporeal treatments in the clinical routine.

METHODS

A prediction and simulation tool for the safe application of RCA during extracorporeal treatments was introduced. The model predicts the course of the ionized calcium level in the patient and the current anticoagulation status in the extracorporeal circuit based on the actual settings of the dialysis machine.

RESULTS

The simulation tool delivers areas in which the blood and dialysate flow can be adjusted to reach the desired target values for RCA and predicts the time course of several parameters during treatment.

Heparin albumin priming in a clinical setting for hemodialysis patients at risk for bleeding

INTRODUCTION

Intermittent hemodialysis (IHD) is sometimes necessary in patients with a bleeding risk, i.e., before/after surgery or brain hemorrhage. In such case IHD has to be modified to limit the conventional anticoagulation used to avoid clotting of the extracorporeal circuit (ECC). We evaluated if priming using a heparin and albumin (HA) mixture could minimize the exposure to heparin.

METHODS

Retrospective data from 1995 to 2013 were collected from 1408 acute dialysis treatment protocols that included 321 patients. Comparisons were made between IHD patients that had increased risk for bleeding and were treated by standard anticoagulation (Group-S), and patients at increased risk of bleeding (Group-HA). The ECC in Group-HA was primed with a solution of unfractioned heparin (UFH) (5000 Units/L) and albumin (1 g/L) in saline that was discarded after priming. There were 16 different dialyzers in the material.

FINDINGS

Comparing Group-S (n = 883) with Group-HA (n = 221), the mean age was 61.6 vs. 62.2 years (P = 0.8), dialysis time was 197 vs. 190 minutes (P = 0.002), and total dose of intravenous anticoagulant/IHD was at median 5000 Units vs. 1200 Units (P = 0.001). Twenty-four percent of patients were treated without any additional heparin. Clotting resulting in interrupted dialysis was similar in both groups (0.8% for Group-S vs. 1.0% for Group-HA, P = 0.8). No secondary bleeding was reported in either group.

DISCUSSION

HA priming minimized the risk of clotting and enabled acute IHD in vulnerable patients without increased bleeding, thus allowing completion of IHD to the same extent as for standard HD.

Dieter Falkenhagen (1942–2015): A Multifaceted Scientist

Dieter Falkenhagen was born in 1942 in Dresden, Germany and died in 2015. He specialized in internal medicine and nephrology. Focusing on artificial organ research, he investigated various aspects of the efficacy and safety of hemodialysis and adsorption technologies, including biocompatibility issues related to blood versus surface interactions and the adverse effects of endotoxin contamination. He studied various mathematical models to analyze efficacy and safety, and animal models to help clarify uncertainty issues. Through his studies, adsorbents were developed, resulting in Prometheus, an artificial liver support device. Anticoagulation models, including citrate perfusion, were improved and made safer by his work. He also stepped into bioreactor research to increase efficacy of liver support devices.

Low concentrations of citrate reduce complement and granulocyte activation in vitro in human blood

Background

The use of acetate in haemodialysis fluids may induce negative effects in patients including nausea and increased inflammation. Therefore, haemodialysis fluids where acetate is substituted with citrate have recently been developed. In this study, we investigated the biocompatibility of citrate employing concentrations used in haemodialysis.

Methods

The effects of citrate and acetate were investigated in human whole blood in vitro under conditions promoting biomaterial-induced activation. Complement activation was measured as generation of C3a, C5a and the sC5b-9 complex, and granulocyte activation as up-regulation of CD11b expression. For the experimental set-up, a mathematical model was created to calculate the concentrations of acetate and citrate attained during haemodialysis.

Results

Citrate reduced granulocyte activation and did not induce higher complement activation compared with acetate at concentrations attained during haemodialysis. Investigating different citrate concentrations clearly showed that citrate is a potent complement inhibitor already at low concentrations, i.e. 0.25 mM, which is comparable with concentrations detected in the blood of patients during dialysis with citrate-containing fluids. Increased citrate concentration up to 6 mM further reduced the activation of C3a, C5a and sC5b-9, as well as the expression of CD11b.

Conclusions

Our results suggest that citrate is a promising substitute for acetate for a more biocompatible dialysis, most likely resulting in less adverse effects for the patients.

Regional citrate anticoagulation for RRTs in critically ill patients with AKI

Hemorrhagic complications have been reported in up to 30% of critically ill patients with AKI undergoing RRT with systemic anticoagulation. Because bleeding is associated with significantly increased mortality risk, strategies aimed at reducing hemorrhagic complications while maintaining extracorporeal circulation should be implemented. Among the alternatives to systemic anticoagulation, regional citrate anticoagulation has been shown to prolong circuit life while reducing the incidence of hemorrhagic complications and lowering transfusion needs. For these reasons, the recently published Kidney Disease Improving Global Outcomes Clinical Practice Guidelines for Acute Kidney Injury have recommended regional citrate anticoagulation as the preferred anticoagulation modality for continuous RRT in critically ill patients in whom it is not contraindicated. However, the use of regional citrate anticoagulation is still limited because of concerns related to the risk of metabolic complications, the complexity of the proposed protocols, and the need for customized solutions. The introduction of simplified anticoagulation protocols based on citrate and the development of dialysis monitors with integrated infusion systems and dedicated software could lead to the wider use of regional citrate anticoagulation in upcoming years.

A target-oriented algorithm for citrate-calcium anticoagulation in clinical practice

BACKGROUND/AIMS

Because of a high monitoring demand and an ensuing need for automation of regional citrate anticoagulation (RCA), a new semi-automated target-oriented algorithm was developed. The aim of this study was the evaluation of its functionality and safety.

METHODS

Fourteen haemodialysis patients were treated 5 times consecutively with RCA. Samples were drawn pre- and post-infusion once per hour. Electrolytes, blood cell counts, acid-base and coagulation parameters were analyzed.

RESULTS

Mean ionized calcium (Ca(2+)) values pre-filter were 0.23 and 0.33 mmol/l in the 0.2 and 0.3 mmol/l target groups, respectively. Extraction ratios for citrate and total calcium through the dialysis filter were constant during the entire treatment (83 and 68%, respectively). Citrate accumulation was avoided.

CONCLUSION

The new algorithm enables safe and accurate RCA. By regulating Ca(2+) pre-filter using the target-oriented algorithm, the degree of anticoagulation may be easily controlled.

A Significant Proportion of Patients Treated with Citrate Containing Dialysate Need Additional Anticoagulation

Background

The blood membrane interaction induced during hemodialysis (HD) activates the coagulation system. To prevent clotting and to maintain dialyzer patency, an anticoagulant such as tinzaparin is used. To increase patency of the dialyzers and to reduce the risk of bleeding related to anticoagulation, citrate-containing dialysate has been introduced in Europe.

Purpose

The aim of this randomized, cross-over study was to investigate if citrate-containing dialysate was safe and efficient enough as the sole anticoagulation agent in chronic HD patients.

Material and Methods

In this clinical setting, 23 patients on chronic hemodialysis were randomized in a cross-over design using anticoagulation either by LMWH-tinzaparin or citrate (Cit) as dialysate (22 completed the study). The study included paired analyses of subjective patency, ionized calcium (iCa), urea reduction rate. During Cit-HD, the iCa was significantly more reduced with prolonged time. The lowest iCa measured was 0.96 mmol/l. The median iCa after 210 min of HD was 1.02 for Cit-Hd and 1.16 for standard tinzaparin-HD (p = 0.001). Patency of dialyzers was estimated as clear in 14%, stripes of clotted fibers in 36%, and a red filter in 32% of HD session. The addition of approximately 40% of the patients’ usual dose of tinzaparin was given to 7 of the patients as a bolus. Four Cit-HD sessions had to be interrupted prematurely due to clotting.

Conclusion

A significant proportion of patients treated with citrate-containing dialysate need additional anticoagulation.

Bench-to-bedside review: Citrate for continuous renal replacement therapy, from science to practice

To prevent clotting in the extracorporeal circuit during continuous renal replacement therapy (CRRT) anticoagulation is required. Heparin is still the most commonly used anticoagulant. However, heparins increase the risk of bleeding, especially in critically ill patients. Evidence has accumulated that regional anticoagulation of the CRRT circuit with citrate is feasible and safe. Compared to heparin, citrate anticoagulation reduces the risk of bleeding and requirement for blood products, not only in patients with coagulopathy, but also in those without. Metabolic complications are largely prevented by the use of a strict protocol, comprehensive training and integrated citrate software. Recent studies indicate that citrate can even be used in patients with significant liver disease provided that monitoring is intensified and the dose is carefully adjusted. Since the citric acid cycle is oxygen dependent, patients at greatest risk of accumulation seem to be those with persistent lactic acidosis due to poor tissue perfusion. The use of citrate may also be associated with less inflammation due to hypocalcemia-induced suppression of intracellular signaling at the membrane and avoidance of heparin, which may have proinflammatory properties. Whether these beneficial effects increase patient survival needs to be confirmed. However, other benefits are the reason that citrate should become the first choice anticoagulant for CRRT provided that its safe use can be guaranteed.

Regional citrate anticoagulation in cardiac surgery patients at high risk of bleeding: a continuous veno-venous hemofiltration protocol with a low concentration citrate solution

Introduction

Regional citrate anticoagulation (RCA) is a valid option in patients at high risk of bleeding who are undergoing continuous renal replacement therapy (CRRT). The aim of this study was to evaluate, in critically ill patients with severe acute kidney injury following cardiac surgery, the efficacy and safety of RCA-continuous veno-venous hemofiltration (CVVH) using a low concentration citrate solution.

Methods

In high bleeding-risk cardiac surgery patients, we adopted, as an alternative to heparin or no anticoagulation, RCA-CVVH using a 12 mmol/l citrate solution. For RCA-CVVH settings, we developed a mathematical model to roughly estimate citrate load and calcium loss. In order to minimize calcium chloride supplementation, a calcium-containing solution was used as post-dilution replacement fluid.

Statistical analysis was performed using the Student t-test or analysis of variance (ANOVA) with post-hoc tests, Wilcoxon or Kruskal-Wallis tests for non-parametric analysis, and Kaplan-Meier survival analysis with Log Rank test.

Results

Thirty-three patients (age 70.8 ± 9.5, Sequential Organ Failure Assessment (SOFA) score 13.9 ± 2.5) were switched to RCA-CVVH from no anticoagulation CRRT. Among them, 16 patients had been previously switched from heparin to no anticoagulation because of bleeding or heparin-related complications. RCA-CVVH filter life (49.8 ± 35.4 hours, median 41, 152 circuits) was significantly longer (P < 0.0001) when compared with heparin (30.6 ± 24.3 hours, median 22, 73 circuits) or no anticoagulation (25.7 ± 21.2 hours, median 20, 77 circuits). Target circuit and systemic Ca⁺⁺ were easily maintained (0.37 ± 0.09 and 1.18 ± 0.13 mmol/l), while the persistence of a mild metabolic acidosis required bicarbonate supplementation (5.8 ± 5.9 mmol/hours) in 27 patients. The probability of circuit running at 24, 48, 72 hours was higher during RCA-CVVH (P < 0.0001), with a lower discrepancy between delivered and prescribed CRRT dose (P < 0.0001). RCA was associated with a lower transfusion rate (P < 0.02). Platelet count (P = 0.012) and antithrombin III activity (P = 0.004) increased throughout RCA-CVVH, reducing the need for supplementation.

Conclusions

RCA safely prolonged filter life while decreasing CRRT downtime, transfusion rates and supplementation needs for antithrombin III and platelets. In cardiac surgery patients with severe multiple organ dysfunction syndrome, the adoption of a 12 mmol/l citrate solution may provide a suboptimal buffers supply, easily overwhelmed by bicarbonate supplementation.

In Vitro Investigations of Citrate Clearance with Different Dialysis Filters

Objective:

In extracorporeal blood purification, citrate anticoagulation offers several substantial advantages over conventional heparin anticoagulation. However, there is still a lack of information on citrate kinetics, especially on the citrate clearance of conventional hemodialyzers. The aim of this study was to investigate the citrate clearance for different hemodialysis filters as a basis for the development of an intelligent citrate-calcium infusion algorithm.

Materials and Methods:

For our experiments, the Fresenius 4008H dialysis machine and the dialysis filters FX 60, F6 HPS, F8 HPS (Fresenius Medical Care, Bad Homburg, Germany), Polyflux 140H and 14L (Gambro Holding, Stockholm, Sweden), Xenium 130 (Baxter AG, Vienna, Austria) and APS-650 (ASAHI Kasei Kuraray Medical, Chiyoda-ku, Japan) were used. Clearance calculations were performed based on plasma/blood flow rate and the citrate concentrations at filter inlet and outlet. All experiments were carried out in vitro with fresh frozen plasma (FFP) or whole blood.

Results:

The results prove that citrate clearance is significantly higher with high-flux filters than with low-flux filters. Higher dialysate flow rates cause a more effective removal of citrate. The citrate clearance for low-flux and high-flux filters was 71 ± 7 and 86 ± 1% of the urea clearance, respectively.

Conclusions:

Citrate can efficiently be removed with standard hemodialysis. However, depending on the infused amounts as well as on the patient - especially in patients with impaired liver function - the use of a high-flux dialysis filter and a high dialysate flow rate should be considered to minimize the risk of citrate accumulation.