Complications of regional citrate anticoagulation: accumulation or overload?

Low bicarbonate replacement fluid normalizes metabolic alkalosis during continuous veno-venous hemofiltration with regional citrate anticoagulation

Background

Metabolic alkalosis is a frequently occurring problem during continuous veno-venous hemofiltration (CVVH) with regional citrate anticoagulation (RCA). This study aimed to evaluate the effectiveness of switching from high to low bicarbonate (HCO₃⁻) replacement fluid in alkalotic critically ill patients with acute kidney injury treated by CVVH and RCA.

Methods

A retrospective-comparative study design was applied. Patients who underwent CVVH with RCA in the ICU between 09/2016 and 11/2017 were evaluated. Data were available from the clinical routine. A switch of the replacement fluid Phoxilium^® (30 mmol/l HCO₃⁻) to Biphozyl^® (22 mmol/l HCO₃⁻) was performed as blood HCO₃⁻ concentration persisted ≥ 26 mmol/l despite adjustments of citrate dose and blood flow. Data were collected from 72 h before the switch of the replacement solutions until 72 h afterwards.

Results

Of 153 patients treated with CVVH during that period, 45 patients were switched from Phoxilium^® to Biphozyl^®. Forty-two patients (42 circuits) were available for statistical analysis. After switching the replacement fluid from Phoxilium^® to Biphozyl^® the serum HCO₃⁻ concentration decreased significantly from 27.7 mmol/l (IQR 26.9–28.9) to 25.8 mmol/l (IQR 24.6–27.7) within 24 h (p < 0.001). Base excess (BE) decreased significantly from 4.0 mmol/l (IQR 3.1–5.1) to 1.8 mmol/l (IQR 0.2–3.4) within 24 h (p < 0.001). HCO₃⁻ and BE concentration remained stable from 24 h till the end of observation at 72 h after the replacement fluid change (p = 0.225). pH and PaCO₂ did not change significantly after the switch of the replacement fluid until 72 h.

Conclusions

This retrospective analysis suggests that for patients developing refractory metabolic alkalosis during CVVH with RCA the use of Biphozyl^® reduces external HCO₃⁻ load and sustainably corrects intracorporeal HCO₃⁻ and BE concentrations. Future studies have to prove whether correcting metabolic alkalosis during CVVH with RCA in critically ill patients is of relevance in terms of clinical outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00850-4.

Regional citrate anti-coagulation dose titration: impact on dose of continuous renal replacement therapy

BACKGROUND

Regional citrate anti-coagulation (RCA) is the recommended anti-coagulation for continuous renal replacement therapy (CRRT). Citrated replacement fluids provide convenience but may compromise effluent delivery when adjusted to maintain circuit ionised calcium levels (circuit-iCa). This study aims to evaluate the effect of RCA titration on the delivered CRRT effluent dose.

METHODS

This prospective observational study evaluated patients on RCA-CRRT in continuous veno-venous hemodiafiltration mode. Citrated replacement fluid was titrated to target circuit-iCa 0.26-0.40 mmol/L. Patients were then stratified into 'reduced-dose' who required citrate down-titration and 'stable-dose' who did not.

RESULTS

Data from 200 RCA-CRRT sessions were collected. The reduced-dose RCA group (n = 114) had higher median initial citrate dose (3.00 vs 2.50; P < 0.001) but lower time-averaged dose (2.49 vs 2.60; P < 0.001). In addition, median prescribed effluent dose was 33.3 mL/kg/h (28.6-39.2) but median delivered effluent dose was significantly lower at 29.9 mL/kg/h (25.4-36.9; P < 0.001). Mortality was higher in the reduced-dose RCA group (39.5% vs 25.6%; P = 0.022) and in patients with delivered-to-prescribed effluent dose ratio of < 0.9 vs ≥ 0.9 (51.3% vs 29.2%; P = 0.014).

CONCLUSION

RCA titration can significantly impact delivered CRRT effluent dose. Measures should be taken to address the CRRT dose deficit and prevent poor outcomes due to inadequate dialysis.

Complications associated with continuous renal replacement therapy

With the evolution of standardized replacement fluids, newer machines, and high flux membranes, continuous renal replacement therapy (CRRT) has made remarkable progress in the field of extracorporeal therapies. CRRT is the preferred dialytic modality for patients in intensive care unit setting (ICU). Standardized protocols are implemented by many institutions to avoid errors and ensure patient safety. However, complications related to CRRT are not uncommon. Understanding CRRT operations is essential to analyze the complications and further assist in developing measures to mitigate the risk. Overview of CRRT complications and potential preventive strategies are discussed in the current review.

Hemodynamic Instability during Acute Kidney Injury and Acute Renal Replacement Therapy: Pathophysiology and Clinical Implications

Hemodynamic instability associated with acute renal replacement therapy (aRRT, HIRRT) and/or with acute kidney injury (AKI) is frequently observed in the intensive care unit; it affects patients' renal recovery, and negatively impacts short- and long-term mortality. A thorough understanding of mechanisms underlying HIRRT and AKI-related hemodynamic instability may allow the physician in adopting adequate strategies to prevent their occurrence and reduce their negative consequences. The aim of this review is to summarize the main alterations occurring in patients with AKI and/or requiring aRRT of those homeostatic mechanisms which regulate hemodynamics and oxygen delivery. In particular, a pathophysiological approach has been used to describe the maladaptive interactions between cardiac output and systemic vascular resistance occurring in these patients and leading to hemodynamic instability. Finally, the potential positive effects of aRRT on these pathophysiological mechanisms and on restoring hemodynamic stability have been described.

Continuous renal replacement therapy and extended indications

Extracorporeal blood purification (EBP) techniques provide support for critically ill patients with single or multiple organ dysfunction. Continuous renal replacement therapy (CRRT) is the modality of choice for kidney support for those patients and orchestrates the interactions between the different artificial organ support systems. Intensive care teams should be familiar with the concept of sequential extracorporeal therapy and plan on how to incorporate new treatment modalities into their daily practices. Importantly, scientific evidence should guide the decision-making process at the bedside and provide robust arguments to justify the costs of implementing new EBP treatments. In this narrative review, we explore the extended indications for CRRT as an adjunctive treatment to provide support for the heart, lung, liver, and immune system. We detail practicalities on how to run the treatments and how to tackle the most frequent complications regarding each of the therapies, whether applied alone or integrated. The physicochemical processes and technologies involved at the molecular level encompassing the interactions between the molecules, membranes, and resins are spotlighted. A clinical case will illustrate the timing for the initiation, maintenance, and discontinuation of EBP techniques.

A Meta-Analysis of Extracorporeal Anticoagulants in Pediatric Continuous Kidney Replacement Therapy

OBJECTIVE

Continuous kidney replacement therapy (CKRT) is the primary therapeutic modality utilized in hemodynamically unstable patients with severe acute kidney injury. As the circuit is extracorporeal, it poses an increased risk of blood clotting and circuit loss; frequent circuit losses affect the provider's ability to provide optimal treatment. The objective of this meta-analysis is to evaluate the safety and efficacy of the extracorporeal anticoagulants in the pediatric CKRT population.

DATA SOURCES

We conducted a literature search on PubMed/Medline and Embase for relevant citations.

STUDY SELECTION

Studies were included if they involved patients under the age of 18 years undergoing CKRT, with the use of anticoagulation (heparin, citrate, or prostacyclin) as a part of therapy. Only English articles were included in the study.

DATA EXTRACTION

Initial search yielded 58 articles and a total of 24 articles were included and reviewed. A meta-analysis was performed focusing on the safety and effectiveness of regional citrate anticoagulation (RCA) vs unfractionated heparin (UFH) anticoagulants in children.

DATA SYNTHESIS

RCA had statistically significantly longer circuit life of 50.65 hours vs. UFH of 42.10 hours. Two major adverse effects metabolic alkalosis and electrolyte imbalance seen more commonly in RCA compared to UFH. There was not a significant difference in the risk of systemic bleeding when comparing RCA vs. UFH.

CONCLUSION

RCA is the preferred anticoagulant over UFH due to its significantly longer circuit life, although vigilant circuit monitoring is required due to the increased risk of electrolyte disturbances. Prostacyclin was not included in the meta-analysis due to the lack of data in pediatric patients. Additional studies are needed to strengthen the study results further.

A simplified protocol for individualized regional citrate anticoagulation for hemodialysis: A single-center, randomized clinical study

INTRODUCTION

The lack of individualized treatment protocols and complicated procedures are important factors limiting the use of regional citrate anticoagulation (RCA) technology in hemodialysis. This study aims to validate the safety and efficacy of a simplified individualized RCA protocol for hemodialysis.

MATERIALS AND METHODS

From June 2019 to August 2019, 45 patients with active bleeding or bleeding tendency undergoing maintenance hemodialysis in the Nephrology Department of the First Affiliated Hospital of Nanchang University were randomly divided into a modified conventional RCA protocol group with a low-flux dialyzer, a simplified individualized RCA protocol group with a high-flux dialyzer, and a simplified individualized RCA protocol group with a low-flux dialyzer.

RESULTS

A total of 45 patients were included in this study. The mean age of the patients was 57.38 ± 19.05 years, and 78% were men. Forty-three patients completed 4 hours of hemodialysis, and the median total clotting scores in the 3 groups were 11, 12, and 12. Compared with the modified conventional RCA protocol group with a low-flux dialyzer, the 2 simplified individualized RCA protocol groups had better clotting scores for the dialyzer, arterial bubble trap, and single-pool urea clearance index (spKt/VBUN) and lower costs. Moreover, these parameters did not differ between the 2 simplified individualized RCA protocol groups. No electrolyte or acid-base imbalances or citrate poisoning was observed in any of the 3 groups. Adverse events did not differ significantly among the 3 groups.

CONCLUSIONS

The simplified individualized RCA protocol is safe, effective, and easy to implement. Therefore, this protocol can be promoted for clinical practice.

TRIAL REGISTRATION

This study was registered in the Chinese Clinical Study Registry under registration number ChiCTR1900023801.

How To Prescribe And Troubleshoot Continuous Renal Replacement Therapy: A Case-Based Review

Continuous RRT (CRRT) is the preferred dialysis modality for solute management, acid-base stability, and volume control in patients who are critically ill with AKI in the intensive care unit (ICU). CRRT offers multiple advantages over conventional hemodialysis in the critically ill population, such as greater hemodynamic stability, better fluid management, greater solute control, lower bleeding risk, and a more continuous (physiologic) approach of kidney support. Despite its frequent use, several aspects of CRRT delivery are still not fully standardized, or do not have solid evidence-based foundations. In this study, we provide a case-based review and recommendations of common scenarios and interventions encountered during the provision of CRRT to patients who are critically ill. Specific focus is on initial prescription, CRRT dosing, and adjustments related to severe hyponatremia management, concomitant extracorporeal membrane oxygenation support, dialysis catheter placement, use of regional citrate anticoagulation, and antibiotic dosing. This case-driven simulation is made as the clinical status of the patient evolves, and is on the basis of step-wise decisions made during the care of this patient, according to the specific patient's needs and the logistics available at the corresponding institution.

Metformin-Induced Lactic Acidosis: A Question of Time

Metformin is an oral antidiabetic largely prescribed in the treatment of type II diabetes. Overdose is associated with life-threatening lactic acidosis. We report the case of the highest metformin concentration ever described secondary to a voluntary suicidal intake. The patient developed a severe lactic acidosis and hemodynamic shock successfully treated with high-flow hemofiltration. Time to start extrarenal epuration is capital to avoid poor evolution.

Regional citrate anticoagulation vs no-anticoagulation for CRRT in hyperlactatemia patients with increased bleeding risk: A retrospective cohort study

There are controversial opinions on the use of regional citrate anticoagulation (RCA) continuous renal replacement therapy (CRRT) in hyperlactatemia patients with increased bleeding risk. Patients with hyperlactatemia and increased bleeding risk who accepted RCA or no-anticoagulation CRRT in our center were retrospectively included. Eighty patients who underwent RCA-CRRT and 47 patients received no-anticoagulation CRRT were included. Filter lifespan was significantly longer in the RCA group than the no-anticoagulation group (44.5 hours [2-89] vs 24.5 hours [1.5-70], P < .001). The adjusted results demonstrated that patients in the no-anticoagulant group had significantly higher risk of filter failure (HR = 4.765, 95% CI 2.703-8.4, P < .001). Bleeding episodes occurred in 19 (24.1%) and 22 (46.8%) patients in the RCA and no-anticoagulation group, respectively (P = .012). The overall citrate accumulation (CA) rate was 5% in the RCA group. Patient mortality was associated with the comorbidity of hypertension, increased serum lactate level, and increased SOFA score. After matching, the filter lifespan was significantly longer in the RCA group than the no-anticoagulation group. With careful monitoring and timely adjustment, RCA most likely was safe and effective for CRRT in hyperlactatemia patients with increased bleeding risk.

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.

A novel predictive score for citrate accumulation among patients receiving artificial liver support system therapy with regional citrate anticoagulation

Patients with liver failure may suffer citrate accumulation when using regional citrate anticoagulation for artificial liver support system therapy (RCA-ALSS therapy). This study aimed to develop a predictive scoring system to stratify the risk of citrate accumulation. A total of 338 patients treated with RCA-ALSS therapy were retrospectively enrolled and randomly divided into derivation and validation cohorts. Longer duration of citrate accumulation (LDCA) was defined as the presence of citrate accumulation 2 h after RCA-ALSS therapy. Four baseline variables were found to be independently associated with LDCA: gender, international normalized ratio of prothrombin time, serum creatinine, and serum chloride. A predictive R-CA model and its simplified R-CA score were developed. The R-CA model (AUROC = 0.848) was found to be superior to the MELD score (AUROC = 0.725; p = 0.022) and other univariate predictors (AUROCs < 0.700; all p ≤ 0.001) in predicting LDCA. The R-CA score (AUROC = 0.803) was as capable as the R-CA model (p = 0.369) and the MELD score (p = 0.174), and was superior to other univariate predictors (all p < 0.05) in predicting LDCA. An R-CA score of 0–2 had a negative predictive value of 90.2% for LDCA. Our R-CA score reliably predicts LDCA in patients with RCA-ALSS therapy, and it is easy to use. Patients with R-CA score of 0–2 can safely receive RCA-ALSS therapy, while others should be carefully evaluated before treatment.

Trial registration: Chinese Clinical Trial Registry, ChiCTR2000029179. Registered 17 January 2020, https://www.chictr.org.cn/showproj.aspx?proj=48084.

Extracorporeal CO2 Removal Integrated within a Continuous Renal Replacement Circuit Offers Multiple Advantages

Extracorporeal CO2 removal within a continuous renal replacement therapy circuit offers multiple advantages for the regulation of the CO2 extraction. The authors review the impact of the dialysate solution, the buffer, and the anticoagulation on CO2 removal. They propose a theoretical model of the ideal circuit for the optimization of CO2 extraction.

Calcium priming of the central venous catheter prevents a drop in ionized calcium concentration during Regional Citrate Anticoagulation

During citrate-based Continuous Renal Replacement Therapy (CRRT), an infusion of calcium is necessary to replace the calcium lost in the effluent. The replacement takes place through a central venous catheter (CVC) that is primed with saline solution. Thus, we hypothesized a potential systemic anticoagulation caused by the unchelated citrate reaching the patient at the start of CRRT because of 0.42 ml of line dead space. In this pilot study, two subpopulations of 7 patients who underwent Continuous Veno-Venous Hemodiafiltration (150 ml/min of blood flow, 1500 ml/h dialysate flow, 1500 ml/h of citrate predilution) were studied. One had the CVC primed with saline, the second with calcium chloride 10%. Calcium replacement rate was 6.3 ± 0.2 ml/h. Ionized calcium concentration was studied over time in the two groups and in the group with saline priming we detected a transient period of hypocalcemia (ionized calcium concentration [iCa] < 1.00 mmol/l for the first 2 hours). In the subpopulation with the calcium priming, this was not present. No significant effect on filter life emerged. Priming of the catheter with calcium seems effective in avoiding a potential issue regarding citrate accumulation at the start of CRRT. More studies are needed to assess the clinical significance of this finding.

Determinants of Total/ionized Calcium in patients undergoing citrate CVVH: A retrospective observational study

PURPOSE

To identify potential determinants of the Total/ionized Ca ratio (T/iCa), a marker of citrate accumulation.

MATERIALS AND METHODS

Single-center retrospective observational study evaluating citrate dose, citrate target, albumin, phosphate, pH, lactate, and APACHE II score as potential determinants. Linear mixed models (LMM) using citrate dose and citrate target were developed describing associations with T/iCa.

RESULTS

From a dataset of 471 samples in 103 patients, an LMM in 379 complete samples (95 patients) sets revealed that citrate dose, pH, phosphate, albumin and APACHE were interactively related to T/iCa. A rising citrate dose was associated with a higher increase in T/iCa when phosphate was high, and less when phosphate was low. A rising albumin was associated with a higher increase in T/iCa when APACHE was high and phosphate was low and less when APACHE was low and phosphate high. In case of acidosis, a rising lactate was associated with a higher increase in T/iCa. In the LMM using citrate target, citrate target and pH were the main independent predictors of T/iCa with albumin, phosphate and APACHE score as modifiers.

CONCLUSIONS

Besides citrate dose, a high pH and high phosphate, albumin and APACHE are also associated with a rising T/iCa.

Prescription of CRRT: a pathway to optimize therapy

Severe acute kidney injury (AKI), especially when caused or accompanied by sepsis, is associated with prolonged hospitalization, progression to chronic kidney disease (CKD), financial burden, and high mortality rate. Continuous renal replacement therapy (CRRT) is a predominant form of renal replacement therapy (RRT) in the intensive care unit (ICU) due to its accurate volume control, steady acid-base and electrolyte correction, and achievement of hemodynamic stability. This manuscript reviews the different aspects of CRRT prescription in critically ill patients with severe AKI, sepsis, and multiorgan failure in ICU. These include the choice of CRRT versus Intermittent and extended hemodialysis (HD), life of the filter/dialyzer including assessment of filtration fraction, anticoagulation including regional citrate anticoagulation (RCA), prescribed versus delivered CRRT dose, vascular access management, timing of initiation and termination of CRRT, and prescription in AKI/sepsis including adsorptive methods of removing endotoxins and cytokines.

Serial measurement of electrolyte and citrate concentrations in blood-primed continuous hemodialysis circuits during closed-circuit dialysis

BACKGROUND

For continuous renal replacement therapy in small infants, due to the large extracorporeal volume involved, blood priming can be necessary to prevent hypotension and hemodilution. Because packed red blood cells (RBCs) have high levels of potassium and citrate, closed-circuit dialysis is often performed. We assessed the metrics of closed-circuit dialysis and serial citrate concentration changes.

METHODS

We performed dialysis of closed circuits primed with expired human packed RBC solution and 5% albumin. Blood and dialysate flow rates were 70 and 33.3 mL/min, respectively. The extracorporeal volume was 70 mL. We measured pH, electrolytes, and citrate in the closed circuit every 3 min for 15 min. We also assessed the adequacy of closed-circuit dialysis using the formula: [dialysate flow rate (mL/min) × time of dialysis (min)]/extracorporeal volume (mL) and we assessed the correlation between citrate and ionized calcium concentrations.

RESULTS

To reach normal concentrations of sodium, potassium, and chloride, 2.4 times as much dialysate fluid as extracorporeal volume was needed. In contrast, for ionized calcium, bicarbonate, and citrate, 3.8 times as much dialysate fluid as extracorporeal volume was required. By simple linear regression analysis, the concentration of citrate was significantly correlated with that of ionized calcium.

CONCLUSIONS

For closed-circuit dialysis using an RBC solution, the formula [dialysate flow rate (mL/min) × time of dialysis (min)]/extracorporeal volume (mL) would be a better parameter to estimate efficacy, compared with other metrics. Additionally, the citrate concentration can be readily estimated from the ionized calcium concentration during closed-circuit dialysis.

Intoxication à la metformine

La metformine, seul représentant disponible en France de la classe des biguanides, est un médicament antidiabétique largement prescrit. L’effet thérapeutique bénéfique du contrôle glycémique obtenu par inhibition de la néoglucogenèse est objectivé par une réduction de la morbimortalité chez les patients diabétiques de type 2. Néanmoins, la metformine affecte aussi le métabolisme du lactate en augmentant sa production par la cellule. Ainsi, l’effet secondaire le plus redouté est l’acidose lactique associée à la metformine (metformin-associated lactic acidosis [MALA]). Celle-ci est liée à une augmentation brutale de la concentration en metformine dans le sang et dans les tissus, que ce soit après ingestion d’une grande quantité de médicament ou plus souvent dans les suites d’une insuffisance rénale aiguë chez un patient traité au long cours. Dans ce contexte d’acidose métabolique majeure avec hyperlactatémie, la sévérité des défaillances d’organes conditionne le pronostic. La prise en charge thérapeutique est symptomatique avec recours précoce à une épuration extrarénale dans les formes sévères ou ne répondant pas au traitement initial. La prévention de la MALA repose avant tout sur le respect des contreindications de la metformine chez les patients diabétiques.

Regional citrate anticoagulation with a substitute containing calcium for continuous hemofiltration in children

Regional citrate anticoagulation (RCA) was recommended as the first treatment option for adults by the Kidney Disease Improving Global Outcomes Kidney Foundation in 2012, for the characteristic of sufficient anticoagulation in vitro, but almost no anticoagulation in vivo. Traditionally, the substitute for RCA is calcium-free. This study investigated a simplified protocol of RCA for continuous hemofiltration (CHF) in children using a commercially available substitute containing calcium.An analytical, observational, retrospective study assessed 59 pediatric patients with 106 sessions and 3580 hours of CHF. Values before and after treatment were compared, including Na, ionic calcium (iCa) and HCO3 concentrations, pH, and the ratio of total calcium to iCa (T/iCa). In addition, in vivo and in vitro iCa, treatment time, sessions with continuous transmembrane pressure >200 mm Hg, and sessions with clotting and bleeding were recorded.The average treatment time was 33.8 ± 10.1 hours. In vitro, 88.5% of iCa achieved the target (0.25-0.35 mmol/L), and in vivo, 95.4% of iCa achieved the target (1.0-1.35 mmol/L). There were 8 sessions with a transmembrane pressure >200 mm Hg and 3 sessions with filters clotted. After treatment, there were 2, 1, and 2 sessions with T/iCa > 2.5 (implying citrate accumulation), iCa < 0.9 mmol/L, and iCa > 1.35 mmol/L. No sodium disorders were recorded. There were fewer cases of acidemia and more cases of alkalemia after treatment compared to before.RCA-CHF with a substitute containing calcium and close monitoring could be a safe and effective treatment for children. In addition, the calcium test site in vitro and the adjustment of citrate should be given strict attention.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CO2 and O2 removal during continuous veno-venous hemofiltration: a pilot study

Background

Carbon dioxide (CO₂) accumulation is a challenging issue in critically ill patients. CO₂ can be eliminated by renal replacement therapy but studies are scarce and clinical relevance is unknown. We prospectively studied CO₂ and O₂ behavior at different sample points of continuous veno-venous hemofiltration (CVVH) and build a model to calculate CO₂ removal bedside.

Methods

In 10 patients receiving standard CVVH under citrate anticoagulation, blood gas analysis was performed at different sample points within the CVVH circuit. Citrate was then replaced by NaCl 0.9% and sampling was repeated. Total CO₂ (tCO₂), CO₂ flow (V̇CO₂) and O₂ flow (V̇O₂) were compared between different sample points. The effect of citrate on transmembrane tCO₂ was evaluated. Wilcoxon matched-pairs signed rank test was performed to evaluate significance of difference between 2 data sets. Friedman test was used when more data sets were compared.

Results

V̇CO₂ in the effluent (26.0 ml/min) correlated significantly with transmembrane V̇CO₂ (24.2 ml/min). This represents 14% of the average expired V̇CO₂ in ventilated patients. Only 1.3 ml/min CO₂ was removed in the de-aeration chamber, suggesting that CO₂ was almost entirely cleared across the membrane filter. tCO₂ values in effluent, before, and after the filter were not statistically different. Transmembrane tCO₂ under citrate or NaCl 0.9% predilution also did not differ significantly. No changes in V̇O₂ were observed throughout the CVVH circuit. Based on recorded data, formulas were constructed that allow bedside evaluation of CVVH-attributable CO₂ removal.

Conclusion

A relevant amount of CO₂ is removed by CVVH and can be quantified by one simple blood gas analysis within the circuit. Future studies should assess the clinical impact of this observation.

Trial registration

The trial was registered at https://clinicaltrials.gov with trial registration number NCT03314363 on October 192,017.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1378-y) contains supplementary material, which is available to authorized users.

Temperature-dependent irreversible conformational change of recombinant ADAMTS13 upon metal ion chelation

BACKGROUND

The catalytic domain of ADAMTS13 possesses one Zn2+ and up to three putative Ca2+ binding sites and can be inactivated by chelating agents. Although replenishment with an appropriate metallic cation is thought to restore the enzyme's proteolytic activity fully, ADAMTS13 stability in a metal ion-depleting environment has not been explored.

OBJECTIVES

To address the stability of ADAMTS13 in citrated human plasma.

METHODS

ADAMTS13 activity was measured using the FRETS-VWF73 fluorogenic assay. The molar ratio of metals bound to ADAMTS13 was determined by size exclusion chromatography inductively coupled plasma mass spectrometry (SEC-ICP-MS). Higher-order structural changes were analyzed using Fourier-transformed infrared spectroscopy and dynamic light scattering.

RESULTS

ADAMTS13 was stable at room temperature for up to 24 hours irrespective of the presence of citrate (0.38%). However, at 37°C, citrate caused a time-dependent activity decrease. No ADAMTS13 activity decrease was seen in heparinized plasma, but the addition of citrate again caused ADAMTS13 instability at 37°C. Scavenging of citrate by the addition of Ca2+ or Zn2+ prior to but not postincubation prevented the activity decrease of the enzyme. The SEC-ICP-MS analyses showed that ADAMTS13 only bound Zn2+ and that its reduced activity correlated with a gradual loss of bound Zn2+ . Concomitant higher-order structural analyses demonstrated structural changes in ADAMTS13 that are typical of less-ordered protein structures.

CONCLUSIONS

Zn2+ is required to stabilize ADAMTS13 structure at physiologic temperature, thereby preventing irreversible loss of enzyme activity. This finding is particularly important to consider when using citrated human plasma as a source of ADAMTS13 in clinical settings.

Energy expenditure and caloric targets during continuous renal replacement therapy under regional citrate anticoagulation. A viewpoint

BACKGROUND

Indirect calorimetry (IC) is the gold standard for measuring energy expenditure in critically ill patients However, continuous renal replacement therapy (CRRT) is a formal contraindication for IC use.

AIMS

To discuss specific issues that hamper or preclude an IC-based assessment of energy expenditure and correct caloric prescription in CRRT-treated patients.

METHODS

Narrative review of current literature.

RESULTS

Several relevant pitfalls for validation of IC during CRRT were identified. First, IC measures CO₂ production (VCO₂) and O₂ consumption to calculate resting energy expenditure (REE) with the Weir equation. VCO₂ measurements are influenced by CRRT because CO₂ is exchanged during the blood purification process. CO₂ exchange also depends on type of pre- and/or postdilution fluid(s). CO₂ dissolves in different forms with dynamic but unpredictable impact on VCO₂. Second, the effect of immunologic activation and heat loss on REE caused by extracorporeal circulation during CRRT is poorly documented. Third, caloric prescription should be adapted to CRRT-induced in- and efflux of different nutrients. Finally, citrate, which is the preferred anticoagulant for CRRT, is a caloric source that may influence IC measurements and REE.

CONCLUSION

Better understanding of CRRT-related processes is needed to assess REE and provide individualized nutritional therapy in this condition.

Safety and efficacy of regional citrate anticoagulation for continuous renal replacement therapy in liver failure patients: a systematic review and meta-analysis

Background

Regional citrate anticoagulation (RCA) is a widely used strategy for continuous renal replacement therapy (CRRT). Most of the current guidelines recommend liver failure as one of the contraindications for citrate anticoagulation. However, some studies suggested that the use of citrate for CRRT in liver failure patients did not increase the risk of citrate-related complications. The purpose of this systematic review is to summarize the current evidences on the safety and efficacy of RCA for CRRT in liver failure patients.

Methods

We performed a comprehensive search on PubMed, Embase, and the Cochrane Library databases from the inception to March 1, 2018. Studies enrolled adult (age > 18 years) patients with various levels of liver dysfunction underwent RCA-CRRT were included in this systematic review.

Results

After the study screening, 10 observational studies with 1241 liver dysfunction patients were included in this systematic review. The pooled rate of citrate accumulation and bleeding was 12% [3%, 22%] and 5% [2%, 8%], respectively. Compared with the baseline data, the serum pH, bicarbonate, and base excess (BE), the rate of metabolic alkalosis, the serum ionized calcium (ionCa) and total calcium (totCa) level, and the ratio of total calcium/ionized calcium (totCa/ionCa) significantly increased at the end of observation. However, no significant increase was observed in serum citrate (MD − 65.82 [− 194.19, 62.55]), lactate (MD 0.49 [− 0.27, 1.26]) and total bilirubin concentration (MD 0.79 [− 0.70, 2.29]) at the end of CRRT. Compared with non-liver failure patients, the live failure patients showed no significant difference in the pH (MD − 0.04 [− 0.13, 0.05]), serum lactate level (MD 0.69 [− 0.26, 1.64]), and totCa/ionCa ratio (MD 0.03 [− 0.12, 0.18]) during CRRT. The median of mean filter lifespan was 55.9 h, with a range from 22.7 to 72 h.

Conclusions

Regional citrate anticoagulation seems to be a safe anticoagulation method in liver failure patients underwent CRRT and could yield a favorable filter lifespan. Closely monitoring the acid base status and electrolyte balance may be more necessary during RCA-CRRT in patients with liver failure.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2317-9) contains supplementary material, which is available to authorized users.

A Rare Case of Severe Metabolic Alkalosis with Unusual Hyperproteinemia Treated with Continuous Renal Replacement Therapy and Regional Citrate Anticoagulation

A 23-year-old woman was referred to the tertiary centre with acute kidney injury and severe metabolic alkalosis following an accidental ethylene glycol poisoning. The patient had been treated with continuous haemodiafiltration and regional citrate anticoagulation, and a tracheostomy was performed due to pneumonia. Besides severe metabolic alkalosis and hypernatremia, the laboratory tests revealed total protein of 108 g/L on admission to the tertiary centre. The haemodiafiltration with regional citrate anticoagulation continued with parallel correction of the alkalosis and normalisation of the total plasma protein. The tracheostomy was decannulated and the patient was discharged to the district hospital. The case demonstrates the usefulness of regional citrate anticoagulation even in severe metabolic alkalosis which was likely related to the method setting prior to admission and to an overcompensation of the initial severe metabolic acidosis. The unusual hyperproteinaemia might be interpreted with the aid of the Stewart-Fencl model of the acid-base regulation.

Good Tolerance of Citrate Accumulation due to Plasma Exchange among Patients with Acute-on-Chronic Liver Failure: A Prospective, Observational Study

Aim

To assess the tolerance of citrate accumulation due to plasma exchange (PE) among patients with acute-on-chronic liver failure (ACLF).

Methods

A prospective, observational study was conducted among patients with ACLF who received heparin anticoagulation during PE-centered therapy without filtration and dialysis. Citrate accumulation was defined as the value of total calcium (Catot) to ionized calcium (Caion) ratio (Catot/Caion) greater than or equal to 2.5 (Catot/Caion ≥ 2.5).

Results

Fifty-four patients were enrolled. The mean age and MELD score were 50.0 ± 11.3 years old and 25 ± 7, respectively. Thirty-three patients had liver cirrhosis. The total 3-month survival rate was 57.4% (31/54). The mean Catot/Caion at the time before PE was 2.05 ± 0.14. Catot/Caion ≥ 2.5 occurred in 100.0% (54/54) and 29.6% (16/54) of patients with mean Catot/Caion of 4.34 ± 1.52 and 2.36 ± 0.32 immediately after PE and 1 hour after PE, respectively, and these levels were much higher than those before PE (p < 0.01). However, all values returned to lower than 2.5 by the next morning with no difference from those before PE (2.10 ± 0.14 versus 2.05 ± 0.14, p > 0.05). Hypocalcemia (ionized calcium) and mild alkalosis were the main metabolic alterations. No symptoms associated with hypocalcemia occurred.

Conclusions

Citrate accumulation is well tolerated by patients with ACLF who receive PE-centered therapy without filtration and dialysis. This study is regeristed with ChiCTR-OOC-17013618.

Use of regional citrate anticoagulation for continuous venovenous hemodialysis in critically ill cancer patients with acute kidney injury

PURPOSE

This study aimed to evaluate the safety and efficacy of a regional citrate anticoagulation (RCA) protocol for continuous venovenous hemodialysis (CVVHD) in cancer patients with acute kidney injury (AKI) in the intensive care unit (ICU) setting.

MATERIAL AND METHODS

One hundred twenty two consecutive ICU cancer patients with AKI treated with citrate-based CVVHD were prospectively evaluated in this prospective observational study.

RESULTS

A total of 7198 h of CVVHD therapy (250 filters) were performed. Patients were 61.3 ± 15.7 years old, 78% had solid cancer and the main AKI cause was sepsis (50%). The in-hospital mortality was 78.7%. Systemic ionized calcium (SCai) was 4.35 (4.10-4.60) mg/dL, severe hypocalcemia (SCai <3.6 mg/dL) was observed in 4.3% of procedures and post-filter ionized calcium was 1.60 (1.40-1.80) mg/dL. Median filter patency was 24.8 (11-43) hours. Factors related to filter clotting were: no tumor evidence (OR 0.44, CI 0.18-0.99); genitourinary tumor (OR 1.83, CI 1.18-2.81); platelets number (each 10,000/mm³) (OR 1.02, CI 1.00-1.04); International Normatized Ratio (INR) (OR 0.59, CI 0.41-0.85) and citrate dose (each 10 mL/h) (OR 0.88, CI 0.82-0.95).

CONCLUSION

Filter patency was relatively short and clotting was associated with active cancer disease, genitourinary tumor, lower citrate dose and lower INR.