Citrate versus acetate-based dialysate in on-line haemodiafiltration. A prospective cross-over study

Comparison of citrate dialysate in pre- and post-dilution online hemodiafiltration: effect on clot formation and adequacy of dialysis in hemodialysis patients

BACKGROUND

Citrate dialysate (CD) has been successfully used in conventional hemodialysis and continuous renal replacement therapy; however, no study has compared pre- and post-dilution online hemodiafiltration (oL-HDF). Therefore, we aimed to investigate the efficacy of citrate anticoagulation for oL-HDF and the metabolic changes and quality of life of patients on hemodialysis treated using both modes.

METHOD

Eight dialysis patients were treated with CD containing 0.8 mmol of citric acid for 4 weeks in each phase. Visual clotting scores were investigated as the primary endpoints. Adequacy of dialysis, laboratory parameters, and quality of life were measured as secondary objectives.

RESULTS

The mean clotting scores in the pre-dilution mode were significantly lower than those in the post-dilution mode and in all phases except the heparin-free phase (p < 0.001 in the baseline phase, p = 0.001 in phase 1, and p = 0.023 in phase 2). The values of Kt/V in both modalities were comparable except during the baseline phase, in which the values of pre-dilution were significantly greater than post-dilution (2.36 ± 0.52/week vs. 1.87 ± 0.33/week;95% CI -0.81 to -0.19, p = 0.002). The patient's quality of life regarding their physical activity level was significantly higher in the post-dilution mode than in the pre-dilution mode at baseline and in phase 1 (p = 0.014 and 0.004 at baseline and in phase 1, respectively). Metabolic changes did not differ between the two modes.

CONCLUSION

Citrate dialysate decreased or prevented anticoagulation in both pre- and post-dilution modes of oL-HDF without significant side effects and had comparable adequacy of dialysis.

Switching from acetate to citrate dialysate in a central concentrate delivery system for high-volume online hemodiafiltration: a retrospective cohort study

Interest in citrate-based dialysate (Cit-D) is growing due to its benefits, including anticoagulation and dialysis efficacy. However, research on safety and efficiency of Cit-D in high-volume hemodiafiltration (HDF) via central concentrate delivery system (CCDS) is scarce. This study aimed to investigate the safety and efficacy of Cit-D when switching from acetate-based dialysate (Acet-D) in high-volume HDF via CCDS. This is a retrospective analysis of 28 patients who underwent post-dilution online HDF via CCDS, who switched from Acet-D to Cit-D. The study period was divided into 3 periods for analysis: 12 weeks using Acet-D (AD period), the first 12 weeks using Cit-D (CD-1 period), and the second 12 weeks using Cit-D (CD-2 period). We collected the laboratory, dialysis, and safety parameters in each period from electrical medical records. After switching from Acet-D to Cit-D, heparin dosage decreased by 17%, whereas the incidence of complications did not increase. Kt/VBUN and urea reduction ratio increased by 4.6% and 2.1%, respectively. Pre-dialysis beta2-microglobulin concentration decreased after using Cit-D. The corrected calcium levels decreased in the CD-1 period compared to the AD period, but in CD-2, they subsequently increased to levels similar to those observed during the AD period. Symptomatic hypocalcemia did not occur, and there was no significant difference in the incidence of hyperparathyroidism. Endotoxin levels and the bacterial culture of ultrapure dialysate were unremarkable throughout all periods. These results might suggest that Cit-D could potentially offer advantages over Acet-D, such as reducing the heparin dose and increasing dialysis efficiency, in patients undergoing high-volume HDF using CCDS.

Citrate Dialysate with and without Magnesium Supplementation in Hemodiafiltration: A Comparative Study Versus Acetate

The choice of dialysate buffer in hemodialysis is crucial, with acetate being widely used despite complications. Citrate has emerged as an alternative because of its favorable effects, yet concerns persist about its impact on calcium and magnesium levels. This study investigates the influence of citrate dialysates (CDs) with and without additional magnesium supplementation on CKD-MBD biomarkers and assesses their ability to chelate divalent metals compared to acetate dialysates (ADs). A prospective crossover study was conducted in a single center, involving patients on thrice-weekly online hemodiafiltration (HDF). The following four dialysates were compared: two acetate-based and two citrate-based. Calcium, magnesium, iPTH, iron, selenium, cadmium, copper, zinc, BUN, albumin, creatinine, bicarbonate, and pH were monitored before and after each dialysis session. Seventy-two HDF sessions were performed on eighteen patients. The CDs showed stability in iPTH levels and reduced post-dialysis total calcium, with no significant increase in adverse events. Magnesium supplementation with CDs prevented hypomagnesemia. However, no significant differences among dialysates were observed in the chelation of other divalent metals. CDs, particularly with higher magnesium concentrations, offer promising benefits, including prevention of hypomagnesemia and stabilization of CKD-MBD parameters, suggesting citrate as a viable alternative to acetate. Further studies are warranted to elucidate long-term outcomes and optimize dialysate formulations. Until then, given our results, we recommend that when a CD is used, it should be used with a 0.75 mmol/L Mg concentration rather than a 0.5 mmol/L one.

Recommended calcium intake in adults and children with chronic kidney disease-a European consensus statement

Mineral and bone disorders (MBD) are common in patients with chronic kidney disease (CKD), contributing to significant morbidity and mortality. For several decades, the first-line approach to controlling hyperparathyroidism in CKD was by exogenous calcium loading. Since the turn of the millennium, however, a growing awareness of vascular calcification risk has led to a paradigm shift in management and a move away from calcium-based phosphate binders. As a consequence, contemporary CKD patients may be at risk of a negative calcium balance, which, in turn, may compromise bone health, contributing to renal bone disease and increased fracture risk. A calcium intake below a certain threshold may be as problematic as a high intake, worsening the MBD syndrome of CKD, but is not addressed in current clinical practice guidelines. The CKD-MBD and European Renal Nutrition working groups of the European Renal Association (ERA), together with the CKD-MBD and Dialysis working groups of the European Society for Pediatric Nephrology (ESPN), developed key evidence points and clinical practice points on calcium management in children and adults with CKD across stages of disease. These were reviewed by a Delphi panel consisting of ERA and ESPN working groups members. The main clinical practice points include a suggested total calcium intake from diet and medications of 800-1000 mg/day and not exceeding 1500 mg/day to maintain a neutral calcium balance in adults with CKD. In children with CKD, total calcium intake should be kept within the age-appropriate normal range. These statements provide information and may assist in decision-making, but in the absence of high-level evidence must be carefully considered and adapted to individual patient needs.

Regional Citrate Anticoagulation: A Tale of More Than Two Stories

Calcium is a key clotting factor, and several inorganic molecules that bind to calcium have been found to reduce the clotting propensity of blood. Citrate, a calcium chelator, is used as inhibitor of the coagulation cascade in blood transfusion. Also, it is used as an anaticoagulant during dialysis to maintain patency of the extracorporeal circuit, known as regional citrate anticoagulation (RCA). The amount of citrate should be chosen such that ionized calcium concentrations in the extracorporeal circuit are reduced enough to minimize propagation of the coagulation cascade. The dialytic removal of the calcium-citrate complexes combined with reduced ionized calcium concentrations makes necessary calcium supplementation of the blood returning to the patient. This can be achieved in different ways. In classical RCA, citrate and calcium are infused in the afferent and efferent tubing, respectively, whereas the dialysate does not contain calcium. This setup has been shown to be highly efficacious with a very low clotting propensity. Strict monitoring of blood electrolytes is required. Alternatively, the use of a high-calcium dialysate leads to calcium loading, obviating the need for a separate calcium infusion pump. The main advantages are simplified delivery of RCA and less fluctuation of systemic calcium concentrations. Currently, citric acid is sometimes added to the acid concentrate as a replacement for acetic acid. Differences and similarities between RCA and citrate-containing dialysate are discussed. RCA is an excellent alternative to heparin for patients at high risk of bleeding.

Success of Pregnancy in a Patient on High-Volume Hemodiafiltration with Citrate-Acidified Dialysate

Although pregnancy in dialysis patients is rare, recent reports in the literature have shown improvement in pregnancy outcome in this population. Increasing doses of dialysis have led to improvement in fetal prognosis, but recommendations are still lacking, and there are few documented reports of pregnant woman on high-volume online hemodiafiltration. Here, we report the first successful pregnancy in a 28-year-old patient on daily high-volume online post-dilution hemodiafiltration with a citrate dialysate. At 37 weeks and 1 day, she delivered a healthy 2.3 kg baby that did not require neonatal intensive care. This case report suggests that hemodiafiltration with a dialysate acidified with citrate is safe in pregnancy. Further reports and a registry are necessary to confirm that high-volume online hemodiafiltration with a citrate dialysate should be the preferred dialysis modality in pregnant women.

Advantages of the use of citrate over acetate as a stabilizer in hemodialysis fluid: A randomized ABC-treat study

Hemodialysis (HD) with bicarbonate dialysis fluid (DF) requires the presence of an acid to prevent the precipitation of calcium and magnesium carbonate. The most used acid is acetic acid, with it several complications have been described. In a previous work we described the acute changes during an HD session with a DF with citrate instead of acetate. Now we report the results in the medium term, 16 weeks. It is a prospective, multicenter, crossover and randomized study, where 56 HD patients with bicarbonate three times a week were dialysed for 16 weeks with 3 mmol/L acetate and 16 weeks with 1 mmol/L citrate. Patients older than 18 years with a previous stay on HD of more than 3 months and with a normal functioning arteriovenous fistula were included. Epidemiological data, dialysis, bioimpedance, biochemistry before and after HD, as well as hypotensive episodes, were collected monthly. After 16 weeks of citrate treatment, preHD ionic calcium and magnesium were significantly lower and PTH higher than in the acetate period. No differences were observed in the effectiveness of dialysis. Hypotensive episodes were significantly more frequent with acetate than with citrate: 311 (14.1%) vs 238 (10.8%) sessions. The lean mass index increased by 0.96 ± 2.33 kg/m² when patients switched from LD with acetate to citrate. HD with citrate modifies several parameters of bone mineral metabolism, not only acutely as previously described, but also in the long term. The substitution of acetate for citrate improves hemodynamic stability, producing less hypotension and can improve nutritional status.

Advantages of the use of citrate over acetate as a stabilizer in hemodialysis fluid: A randomized ABC-treat study

Hemodialysis (HD) with bicarbonate dialysis fluid (DF) requires the presence of an acid to prevent the precipitation of calcium and magnesium carbonate. The most used acid is acetic acid, with it several complications have been described. In a previous work, we described the acute changes during an HD session with a DF with citrate instead of acetate. Now, we report the results in the medium term, 16 weeks. It is a prospective, multicenter, crossover and randomized study, where 56 HD patients with bicarbonate three times a week were dialysed for 16 weeks with 3mmol/L acetate and 16 weeks with 1mmol/L citrate. Patients older than 18 years with a previous stay on HD of more than 3 months and with a normal functioning arteriovenous fistula were included. Epidemiological data, dialysis, bioimpedance, biochemistry before and after HD, as well as hypotensive episodes, were collected monthly. After 16 weeks of citrate treatment, pre-HD ionic calcium and magnesium were significantly lower and paratiroid hormone (PTH) higher than in the acetate period. No differences were observed in the effectiveness of dialysis. Hypotensive episodes were significantly more frequent with acetate than with citrate: 311 (14.1%) vs 238 (10.8%) sessions. The lean mass index increased by 0.96±2.33kg/m2 when patients switched from DF with acetate to citrate. HD with citrate modifies several parameters of bone mineral metabolism, not only acutely as previously described, but also in the long-term. The substitution of acetate for citrate improves hemodynamic stability, producing less hypotension and can improve nutritional status.

Effects of on-line hemodiafiltration regimens and dialysate composition on serum concentrations of magnesium and calcium ions

Background

Low-ionized magnesium and high-ionized calcium levels are associated with increased cardiovascular mortality in patients undergoing dialysis. We examined the effects of the dilution method, substitution volume, and dialysate of on-line hemodiafiltration on the total and ionized magnesium and calcium levels.

Methods

Eighteen patients were randomly assigned to three dialysate groups: two acetic acid dialysate groups and one citrate dialysate group. Five treatment conditions were applied: pre-diluted on-line hemodiafiltration, post-diluted on-line hemodiafiltration, and hemodialysis.

Results

The total and ionized serum levels of magnesium and calcium were evaluated and found to be unaffected by the dilution methods and substitution volumes. The albumin leakage was approximately 3 g/session under the pre-dilution and hemodiafiltration conditions, and approximately 4–5 g/session under the post-dilution condition. The ionized magnesium concentration decreased in the citrate dialysate group.

Conclusion

The on-line hemodiafiltration parameters had a negligible effect on ionized magnesium and calcium; however, the use of citrate dialysate decreased the ionized magnesium levels, probably because of chelation.

Trial registration

000028172. The study was registered on July 11 2017.

A high magnesium concentration in citrate dialysate prevents oxidative stress and damage in human monocytes in vitro

BACKGROUND

The use of dialysis fluids (DFs) during haemodialysis has been associated with increased oxidative stress and reduced serum magnesium (Mg) levels, contributing to chronic inflammation. Since the role of Mg in modulating immune function and reducing oxidative stress has been demonstrated, the aim of this study was to characterize in vitro whether increasing the Mg concentration in DFs could protect immune cells from oxidative stress and damage.

METHODS

The effect of citrate [citrate dialysis fluid (CDF), 1 mM] or acetate [acetate dialysis fluid (ADF), 3 mM] dialysates with low (0.5 mM; routinely used) or high (1 mM, 1.25 mM and 2 mM) Mg concentrations was assessed in THP-1 human monocytes. The levels of reactive oxygen species (ROS), malondialdehyde (MDA) and oxidized/reduced (GSSG/GSH) glutathione were quantified under basal and inflammatory conditions (stimulation with lipopolysaccharide, LPS).

RESULTS

The increase of Mg in CDF resulted in a significant reduction of ROS production under basal and inflammatory conditions (extremely marked in 2 mM Mg; P < 0.001). These effects were not observed in ADF. Interestingly, in a dose-dependent manner, high Mg doses in CDF reduced oxidative stress in monocytes under both basal and inflammatory conditions. In fact, 2 mM Mg significantly decreased the levels of GSH, GSSG and MDA and the GSSG/GSH ratio in relation to 0.5 mM Mg.

CONCLUSIONS

CDF produces lower oxidative stress than ADF. The increase of Mg content in DFs, especially in CDF, could have a positive and protective effect in reducing oxidative stress and damage in immune cells, especially under inflammatory conditions.

Citrate high volume on-line hemodiafiltration modulates serum Interleukin-6 and Klotho levels: the multicenter randomized controlled study "Hephaestus"

BACKGROUND

Studies addressing the anti-inflammatory properties of citrate dialysate enrolled patients in both hemodialysis (HD) and hemodiafiltration (HDF), the latter not adjusted for adequate convective exchange. This is a potential source of confounding in that HDF itself has anti-inflammatory effects regardless of the buffer, and optimal clinical outcomes are related to the amount of convection.

METHODS

To distinguish the merits of the buffer from those of convection, we performed a 6-month, prospective, randomized, crossover AB-BA study. Comparisons were made during the 3-month study period of on-line HDF with standard dialysate containing three mmol of acetic acid (OL-HDFst) and the 3-month of OL-HDF with dialysate containing one mmol of citric acid (OL-HDFcit). Primary outcome measure of the study was interleukin-6 (IL-6). Klotho, high sensitivity C-reactive protein (hsCRP), fetuin and routine biochemical parameters were also analyzed.

RESULTS

We analyzed 47 patients (mean age 64 years, range 27-84 years) enrolled in 10 participating Nephrology Units. Convective volumes were around 25 L/session with 90 percent of sessions > 20 L and ß2-microglobulin reduction rate 76% in both HDFs. Baseline median IL-6 values in OL-HDFst were 5.6 pg/ml (25:75 interquartile range IQR 2.9:10.6) and in OL-HDFcit 6.6 pg/ml (IQR 3.4:11.4 pg/ml). The difference was not statistically significant (p 0.88). IL-6 values were lower during OL-HDFcit than during OL-HDFst, both when analyzed as the median difference of overall IL-6 values (p 0.02) and as the median of pairwise differences between the baseline and the 3-month time points (p 0.03). The overall hsCRP values too, were lower during OL-HDFcit than during OL-HDFst (p 0.01). Klotho levels showed a time effect (p 0.02) and the increase was significant only during OL-HDFcit (p 0.01).

CONCLUSIONS

Citrate buffer modulated IL-6, hsCRP and Klotho levels during high volume OL-HDF. These results are not attributable to differences in the dialysis technology that was applied and may suggest a potential biological effect of citrate on CKD-associated inflammatory state. ClinicalTrials.gov identifier NCT02863016.

Improvements in Inflammation and Calcium Balance of Citrate versus Acetate as Dialysate Buffer in Maintenance Hemodialysis: A Unicentric, Cross-Over, Prospective Study

INTRODUCTION

The composition of the dialysate is a crucial feature in the dialysis treatment. Two of its most debated elements are the optimal calcium concentration and the use of acetate as a buffer. Moreover, among the different alternatives to achieve acetate-free dialysis, the use of citrate is postulated as the most suitable option. The objective of this study is to identify the potential beneficial effects of citrate when compared to acetate dialysate (AD) both in short-term effects (especially regarding intradialytic calcium balance and cardiac damage biomarkers) and in medium-term ones with CKD-mineral and bone disorder (CKD-MBD) and inflammatory biomarkers measured after twelve sessions performed with each dialysate.

METHODS

This is a unicentric, cross-over, prospective study. Each patient underwent 24 dialysis sessions, 12 with each dialysate buffer. Blood samples were taken in 2 different sessions with each acidifier. They include CKD-MBD and inflammatory biomarkers. The calcium concentration of both dialysates was 1.5 mmol/L, while all other dialysis parameters and patients' treatment remained unchanged during the study period.

RESULTS

When comparing AD and citrate dialysate (CD), there were no differences in pre-dialysis ionized calcium (iCa) (1.11 vs. 1.08 mmol/L) in both groups. However, there was a significant increase in iCa with the use of AD in immediate and 30-min post-dialysis blood samples. In contrast, iCa levels remained stable with the use of citrate. Inflammatory biomarkers were also reduced after the use of CD.

CONCLUSIONS

The use of citrate provides interesting advantages when compared to acetate. It maintains iCa levels stable during dialysis sessions with a neutral or negative effect on calcium balance, and it improves the chronic inflammatory condition that comes with long-time hemodialysis treatment. These beneficial effects may lead to an improvement in clinical outcomes.

Impact of the dialysate acid component on haemodialysis mortality rates

BACKGROUND

No prospective study has evaluated the long-term effect on mortality of the new acid concentrates added to bicarbonate dialysate. The aim of this pharmacoepidemiological study was to evaluate the association between hydrochloric or citric acid-based dialysate and mortality on haemodialysis (HD).

METHODS

This study included 117 796 patients with 3 723 887 months on HD recorded in the national French Renal Epidemiology and Information Network registry. Dialysate acid components were retrospectively reconstructed for each facility. All patients on HD were associated each month with an exposure based on that at their facility of treatment. We took each patient's time-varying exposure into account to calculate the monthly mortality rates for each exposure. Incidence rate ratios (IRRs) for mortality were calculated with a Poisson regression, with acetic acid as the reference. Regressions were adjusted for initial clinical characteristics (age, gender, previous cardiovascular events, active malignancy, diabetes, pulmonary disease, mobility), dialysis technique and location (in-centre, outpatient centre, self-care unit) and ESRD vintage, updated monthly.

RESULTS

The crude mortality rate per 1000 patient-months with citric acid {11.5 [95% confidence interval (CI) 11.1-12.0]} was lower than with either acetic acid [12.9 (95% CI 12.8-13.1)] or hydrochloric acid [12.8 (95% CI 12.2-13.5)]. For the 2014-17 period, the IRR for mortality with citric acid [adjusted IRR 0.94 (95% CI 0.90-0.99)] and with hydrochloric acid [adjusted IRR 0.86 (95% CI 0.79-0.94)] were significantly lower than with acetic acid.

CONCLUSION

This post-marketing study of long-term exposure to dialysate acidifiers at the patient level found the use of citric and hydrochloric acid-based dialysates, compared with acetic acid, was associated with lower mortality.

Long-term mortality risk associated with citric acid- and acetic acid-based bicarbonate haemodialysis: a historical cohort propensity score-matched study in a large, multicentre, population-based study

Background

Citric acid-based bicarbonate dialysate (CiD) is increasingly used in haemodialysis (HD) to improve haemodynamic tolerance and haemocompatibility associated with acetic acid-based bicarbonate dialysate. Safety concerns over CiD have been raised recently after a French ecological study reported higher mortality hazard in HD clinics with high CiD consumption. Therefore, we evaluated the mortality risk associated with various acidifiers (AcD, CiD) of bicarbonate dialysate.

Methods

In this multicentre, historical cohort study, we included adult incident HD patients (European, Middle-East and Africa Fresenius Medical Care network; 1 January 2014 to 31 October 2018). We recorded acidifiers of bicarbonate dialysis and dialysate composition for each dialysis session. In the primary intention-to-treat analysis, patients were assigned to the exposed group if they received CiD in &gt;70% of sessions during the first 3 months (CiD70%), whereas the non-exposed group received no CiD at all. In the secondary analysis, exposure was assessed on a monthly basis for the whole duration of the follow-up.

Results

We enrolled 10 121 incident patients during the study period. Of them, 371 met the criteria for inclusion in CiD70%. After propensity score matching, mortality was 11.43 [95% confidence interval (CI) 8.86–14.75] and 12.04 (95% CI 9.44–15.35) deaths/100 person-years in the CiD0% and CiD70% groups, respectively (P = 0.80). A similar association trend was observed in the secondary analysis.

Conclusions

We did not observe evidence of increased mortality among patients exposed to CiD in a large European cohort of dialysis patients despite the fact that physicians were more inclined to prescribe CiD to subjects with worse medical conditions.

Long-term effects of citric acid-based bicarbonate haemodialysis on patient outcomes: a survival propensity score–matched study in western France

Background

Citric acid–based bicarbonate haemodialysis (CIT-HD) has gained more clinical acceptance over the last few years in France and is a substitute for other acidifiers [e.g. acetic acid (CH3COOH) and hydrochloric acid (HCl)]. This trend was justified by several clinical benefits compared with CH3COOH as well as the desire to avoid the consequences of the corrosive action of HCl, but a nationwide clinical report raised concerns about the long-term safety of CIT-HD. The aim of this study was to assess the long-term effects of CIT-HD exposure on patient outcomes in western France.

Methods

This is a population-based retrospective multicentre observational study performed in 1132 incident end-stage kidney disease patients in five sanitary territories in western France who started their renal replacement therapy after 1 January 2008 and followed up through 15 October 2018. Relevant data, collected prospectively with the same medical software, were anonymously aggregated for the purposes of the study. The primary goal of this study was to investigate the effects of citrate exposure on all-cause mortality. To provide a control group to CIT-HD one, propensity score matching (PSM) at 2:1 was performed in two steps: the first analysis was intended to be exploratory, comparing patients who received citrate ≤80% of the time (CIT-HD ≤80) versus those who received citrate &gt;80% of the time (CIT-HD &gt;80), while the second analysis was intended to be explanatory in comparing patients with 0% (CIT-HD0) versus 100% citrate time exposure (CIT-HD100).

Results

After PSM, in the exploratory part of the analysis, 432 CIT-HD ≤80 patients were compared with 216 CIT-HD &gt;80 patients and no difference was found for all-cause mortality using the Kaplan–Meier model (log-rank 0.97), univariate Cox regression analysis {hazard ratio [HR] 1.01 [95% confidence interval (CI) 0.71–1.40]} and multivariate Cox regression analysis [HR 1.11 (95% CI 0.76–1.61)] when adjusted for nine variables with clinical pertinence and high statistical relevance in the univariate analysis. In the explanatory part of the analysis, 316 CIT-HD0 patients were then compared with 158 CIT-HD100 patients and no difference was found using the Kaplan–Meier model (log-rank 0.06), univariate Cox regression analysis [HR 0.69 (95% CI 0.47–1.03)] and multivariate Cox regression analysis [HR 0.87 (95% CI 0.57–1.33)] when adjusted for seven variables with clinical pertinence and high statistical relevance in the univariate analysis.

Conclusions

Findings of this study support the notion that CIT-HD exposure ≤6 years has no significant effect on all-cause mortality in HD patients. This finding remains true for patients receiving high-volume online haemodiafiltration, a modality most frequently prescribed in this cohort.

Citric-acid dialysate improves the calcification propensity of hemodialysis patients: A multicenter prospective randomized cross-over trial

INTRODUCTION

The concentration of dialysate calcium (dCa) has been suggested to affect vascular calcification, but evidence is scarce. Calcification propensity reflects the intrinsic capacity of serum to prevent calcium and phosphate to precipitate. The use of citric-acid dialysate may have a beneficial effect on the calcification propensity due to the chelating effect on calcium and magnesium. The aim of this study was to compare the intradialytic and short-term effects of haemodialysis with either standard acetic-acid dialysate with dCa1.50 (A1.5) or dCa1.25 (A1.25), as well as citric-acid dialysate with dCa1.50 (C1.5) in bicarbonate dialysis on the calcification propensity of serum.

METHODS

Chronic stable hemodialysis patients were included. This multicenter randomized cross-over study consisted out of a baseline week (A1.5), followed by the randomized sequence of A1.25 or C1.5 for one week after which the alternate treatment was provided after a washout week with A1.5. Calcification propensity of serum was assessed by time-resolved nephelometry where the T50 reflects the transition time between formation of primary and secondary calciprotein particles.

RESULTS

Eighteen patients (median age 70 years) completed the study. Intradialytic change in T50 was increased with C1.5 (121 [90-152]min) compared to A1.25 (83 [43-108]min, p<0.001) and A1.5 (66 [18-102]min, p<0.001). During the treatment week, predialysis T50 increased significantly from the first to the third session with C1.5 (271 [234-291] to 280 [262-339]min, p = 0.002) and with A1.25 (274 [213-308] to 307 [256-337]min, p<0.001), but not with A1.5 (284 [235-346] to 300 [247-335]min, p = 0.33).

CONCLUSION

Calcification propensity, as measured by the change in T50, improved significantly during treatment in C1.5 compared to A1.25 and A1.5. Long-term studies are needed to investigate the effects of different dialysate compositions concentrations on vascular calcification and bone mineral disorders.

Impact of acetate- or citrate-acidified bicarbonate dialysate on ex vivo aorta wall calcification

Vascular calcification is highly prevalent in patients with chronic hemodialysis. Increased acetatemia during hemodialysis sessions using acetate-acidified bicarbonate has also been associated with several abnormalities, By contrast, these abnormalities were not induced by citrate-acidified bicarbonate dialysis. Moreover, citrate is biocompatible alternative to acetate in dialysis fluid. However, the effects of citrate on vascular calcification during hemodialysis had not been studied in detail. This study analyzed herein the effects of acetate- or citrate-acidified bicarbonate dialysis on vascular calcification. Citrate has been shown to inhibit calcification in urine in hemodialysis patients. Therefore, our hypothesis is that citrate-acidified bicarbonate dialysis could reduce vascular calcification. Blood samples before and after hemodialysis from patients on acetate- or citrate-acidified bicarbonate dialysis were collected in heparin-containing tubes (n = 35 and n = 25 respectively). To explore the effect of pre- and post-dialysis plasmatic bicarbonate and citrate on vascular calcification, rats aortic rings cultured ex vivo in Minimum Essential Medium containing 0.1% FBS and 45-calcium as radiotracer were used (n = 24). After 7 days of incubation aortic rings were dried, weighed and radioactivity was measured via liquid scintillation counting. Bicarbonate levels increase calcium accumulation in rat aortic wall in a dose-response manner (pH = 7.4). Moreover, citrate prevents calcium accumulation, with a mean inhibitor concentration (IC₅₀) value of 733 µmol/L. During acetate-acidified bicarbonate dialysis, bicarbonate and citrate levels in plasma increase (22.29 ± 3.59 versus 28.63 ± 3.56 mmol/L; p < 0.001) and decrease (133.3 ± 53.6 versus 87.49 ± 32.3 µmol/L, p < 0.001), respectively. These changes in pos-hemodialysis plasma significantly (p < 0.001) alter calcium accumulation in the aortic wall (38.9% higher). Moreover, citrate-acidified bicarbonate dialysis increases post-hemodialysis citrate levels 5-fold (145 ± 79.8 versus 771.6 ± 184.3 µmol/L), reducing calcium accumulation in the aortic wall. Citrate-acidified bicarbonate dialysis reduces plasmatic calcium and pH variations during dialysis session (Δ[Ca²⁺] = −0.019 ± 0.089; ΔpH = 0.098 ± 0.043) respect to acetate-acidified bicarbonate dialysis (Δ[Ca²⁺] = 0.115 ± 0.118; ΔpH = 0.171 ± 0.078). To our knowledge, our study is the first to show that citrate protects against calcium accumulation in rat aortic walls ex vivo. Therefore, citrate-acidified bicarbonate dialysis may be an alternative approach to reduce calcification in hemodialysis patients without additional cost.

Prospective randomised multicentre study to demonstrate the benefits of haemodialysis without acetate (with citrate): ABC-treat Study. Acute effect of citrate

INTRODUCTION

Dialysis fluid (DF), an essential element in hemodialysis (HD), is manufactured in situ by mixing three components: treated water, bicarbonate concentrate and acid concentrate. To avoid the precipitation of calcium and magnesium carbonate that is produced in DF by the addition of bicarbonate, it is necessary to add an acid. There are 2 acid concentrates that contain acetate (ADF) or citrate (CDF) as a stabilizer.

OBJECTIVE

To compare the acute effect of HD with CDF vs. ADF on the metabolism of calcium, phosphorus and magnesium, acid base balance, coagulation, inflammation and hemodynamic stability.

METHODS

Prospective, multicenter, randomized and crossed study, of 32 weeks duration, in patients in three-week HD, AK-200-Ultra-S or Artis monitor, 16 weeks with ADF SoftPac^®, prepared with 3mmol/L of acetate, and 16 weeks with CDF SelectBag Citrate^®, with 1mmol/L of citrate. Patients older than 18 years were included in HD for a minimum of 3 months by arteriovenous fistula. Epidemiological, dialysis, pre and postdialysis biochemistry, episodes of arterial hypotension, and coagulation scores were collected monthly during the 8 months of the study. Pre and post-dialysis analysis were extracted: venous blood gas, calcium (Ca), ionic calcium (Cai), phosphorus (P), magnesium (Mg) and parathyroid hormone (PTH) among others. ClinicalTrials.gov NCT03319680.

RESULTS

We included 56 patients, 47 (84%) men and 9 (16%) women, mean age: 65.3 (16.4) years, technique HD/HDF: 20 (35.7%)/36 (64.3%). We found differences (p<0.05) when using the DF with citrate (C) versus acetate (A) in the postdialysis values of bicarbonate [C: 26.9 (1.9) vs. A: 28.5 (3) mmol/L], Cai [C: 1.1 (0.05) vs. A: 1.2 (0.08) mmol/L], Mg [C: 1.8 (0.1) vs A: 1, 9 (0.2) mg/dL] and PTH [C: 255 (172) vs. 148 (149) pg/mL]. We did not find any differences in any of the parameters measured before dialysis. Of the 4,416 sessions performed, 2,208 in each group, 311 sessions (14.1%) with ADF and 238 (10.8%) with CDF (p<0.01), were complicated by arterial hypotension. The decrease in maximum blood volume measured by Hemoscan^® biosensor was also lower [-3.4 (7.7) vs -5.1 (8.2)] although without statistical significance.

CONCLUSION

Dialysis with citrate acutely produces less postdialysis alkalemia and significantly modifies Ca, Mg and PTH. CDF has a positive impact on hemodynamic tolerance.

Vascular Targeting of Radiolabeled Liposomes with Bio-Orthogonally Conjugated Ligands: Single Chain Fragments Provide Higher Specificity than Antibodies

Liposomes are a proven, versatile, and clinically viable technology platform for vascular delivery of drugs and imaging probes. Although targeted liposomes have the potential to advance these applications, complex formulations and the need for optimal affinity ligands and conjugation strategies challenge their translation. Herein, we employed copper-free click chemistry functionalized liposomes to target platelet-endothelial cell adhesion molecule (PECAM-1) and intracellular adhesion molecule (ICAM-1) by conjugating clickable monoclonal antibodies (Ab) or their single chain variable fragments (scFv). For direct, quantitative tracing, liposomes were surface chelated with ¹¹¹In to a >90% radiochemical yield and purity. Particle size and distribution, stability, ligand surface density, and specific binding to target cells were characterized in vitro. Biodistribution of liposomes after IV injection was characterized in mice using isotope detection in organs and by noninvasive imaging (single-photon emission computed tomography/computed tomography, SPECT/CT). As much as 20-25% of injected dose of liposomes carrying PECAM and ICAM ligands, but not control IgG accumulated in the pulmonary vasculature. The immunospecificity of pulmonary targeting of scFv/liposomes to PECAM-1 and ICAM-1, respectively, was 10-fold and 2.5-fold higher than of Ab/liposomes. Therefore, the combination of optimal ligands, benign conjugation, and labeling yields liposomal formulations that may be used for highly effective and specific vascular targeting.

Mathematical model of calcium exchange during haemodialysis using a citrate containing dialysate

Calcium has two important roles in haemodialysis. It participates in the activation of blood coagulation and calcium intakes have a major impact on patient mineral and bone metabolism. The aim of this article is to propose a mathematical model for calcium ions concentration in a dialyzer during haemodialysis using a citrate dialysate. The model is composed of two elements. The first describes the flows of blood and dialysate in a dialyzer fibre. It was obtained by asymptotic analysis and takes into account the anisotropy of the fibres forming a dialyzer. Newtonian and non-Newtonian blood rheologies were tested. The second part of the model predicts the evolution of the concentration of five chemical species present in these fluids. The fluid velocity field drives the convective part of a convection-reaction-diffusion system that models the exchange of free and complexed calcium. We performed several numerical experiments to calculate the free calcium concentration in the blood in a dialyzer using dialysates with or without citrate. The choice of blood rheology had little effect on the fluid velocity field. Our model predicts that only a citrate based dialysate without calcium can decrease free calcium concentration at the blood membrane interface low enough to inhibit blood coagulation. Moreover for a given calcium dialysate concentration, adding citrate to the dialysate decreases total calcium concentration in the blood at the dialyzer outlet. This decrease of the calcium concentration can be compensated by infusing in the dialyzed blood a quantity of calcium computed from the model.

Bicarbonate Balance and Prescription in ESRD

The optimal approach to managing acid-base balance is less well defined for patients receiving hemodialysis than for those receiving peritoneal dialysis. Interventional studies in hemodialysis have been limited and inconsistent in their findings, whereas more compelling data are available from interventional studies in peritoneal dialysis. Both high and low serum bicarbonate levels associate with an increased risk of mortality in patients receiving hemodialysis, but high values are a marker for poor nutrition and comorbidity and are often highly variable from month to month. Measurement of pH would likely provide useful additional data. Concern has arisen regarding high-bicarbonate dialysate and dialysis-induced alkalemia, but whether these truly cause harm remains to be determined. The available evidence is insufficient for determining the optimal target for therapy at this time.

Is Anticoagulation Discontinuation Achievable with Citrate Dialysate during HDF Sessions?

Citrate dialysate has been developed for few years to replace acetate and HCl concentrates. In Online Postdilution Hemodiafiltration (OL-POST-HDF), several issues are remaining concerning the possibility of stopping anticoagulation during sessions and the side effects of citrate solutions on calcium metabolism. This 1-year monocentric retrospective study included all patients exposed to citrate in OL-POST-HDF with nadroparin decrease for more than one month. Clotting events, serum calcium, PTH, hemoglobin, CRP, depuration parameters, and treatments administrated were recorded for analysis. 27 patients experienced nadroparin decrease and 5 did not receive nadroparin at the end of the study. Nadroparin decrease and withdrawal were both associated with more clotting events whereas the use of vitamin K antagonists was protective. No significant metabolic side effects were observed. Citrate dialysate does not allow anticoagulation discontinuation or decrease but has no significant side effects on mineral bone metabolism or erythropoiesis.

Effects of citrate dialysate in chronic dialysis: a multicentre randomized crossover study

BACKGROUND

Although citrate dialysate (CiDi) is regarded to be safe, dialysis modalities using higher dialysate volumes, like haemodiafiltration (HDF), may expose patients to higher citrate load and thus increase the risk of complications. We investigated the residual risk of CiDi compared with standard dialysate (StDi) in patients on different dialysis modalities and its effect on dialysis dose.

METHODS

In a multicentre randomized crossover study, 92 dialysis patients (HDF post-dilution: n = 44, HDF pre-dilution: n = 26, haemodialysis: n = 25) were treated for 4 weeks with each dialysate (StDi and CiDi). Hypocalcaemia (ionized calcium ≤0.9 mmol/L), alkalosis (pH ≥7.55), post-treatment bicarbonate ≥32 mmol/L, pre-treatment bicarbonate ≥27 mmol/L, intra-dialytic events (IEs) and adverse events (AEs) between dialysis sessions were investigated as primary end points. The secondary objective was dialysis efficacy, i.e. dose and removal ratios of urea, creatinine, phosphate and β-2-microglobulin.

RESULTS

Post-dialysis overcorrection of bicarbonate (>32 mmol/L) was less frequent with CiDi (P = 0.008). Other predefined calcium and acid-base disturbances did not vary. There was no significant difference in IE. However, more patients developed AEs such as fatigue, muscle spasms or pain using CiDi (StDi: 41 versus CiDi: 55 patients, P = 0.02), particularly in the first 2 weeks of exposure. Dialysis efficacy was comparable with both dialysates.

CONCLUSIONS

It can be confirmed that CiDi is not associated with the development of severe calcium and acid-base disorders, even when dialysis modalities with higher citrate loads are used. However, a refinement of the CiDi composition to minimize AEs is necessary.

Individualizing the dialysate calcium concentration

PURPOSE OF REVIEW

The optimal dialysate calcium concentration (DCC) in hemodialysis patients is still debated. Strategies have varied over time due to developments in the treatments available for mineral metabolism disorders and our increasing knowledge of bone and vascular diseases. International recommendations [Kidney Disease Outcomes Quality Initiative (KDIGO) and European Best Practice Guidelines] urge for DCC individualization in order to meet the patient's specific needs whenever possible. In this review, we aim to discuss the pros and cons of individualizing the DCC in hemodialysis patients.

RECENT FINDINGS

Different regions of the world have various strategies with respect to DCCs. Decreasing the DCC slightly reduces calcemia, but mainly stimulates parathyroid hormone secretion and bone turnover. Conversely, increasing the DCC increases calcemia slightly and reduces parathyroid hormone secretion and bone turnover markedly. Furthermore, higher DCCs favor hemodynamic stability and can prevent ventricular arrhythmias. The impact of DCC individualization on survival rate or cardiovascular calcification progression has not been evaluated.

SUMMARY

Individualizing DCC appears to be useful but requires time, a clear defined strategy, and close biological monitoring. Even though some studies have shown that using individualized DCCs of 1.25 or 1.75 mmol/l is not harmful, the real benefits of this strategy need to be assessed in a large, multicentric trial.