Citrate plasma levels in patients under regional anticoagulation in continuous venovenous hemofiltration

A Comparison of the Anticoagulation Efficacy and Safety of Epoprostenol to Heparin and Citrate in Children Receiving Continuous Renal Replacement Therapy

INTRODUCTION

Anticoagulants are used in continuous renal replacement therapy (CRRT) to prolong filter life. There are no prior investigations directly comparing epoprostenol to more commonly used forms of anticoagulation in children. Therefore, the primary aim of this study was to assess the efficacy and safety of epoprostenol as compared to heparin and citrate anticoagulation in a pediatric cohort.

METHODS

We performed a retrospective analysis of all patients <18 years of age admitted to an academic quaternary care children's hospital from 2017-2022 who received epoprostenol, heparin, or citrate exclusively for CRRT anticoagulation. Efficacy was evaluated by comparing the hours to the first unintended filter change and the ratio of filters used to CRRT days. Safety was assessed by evaluating changes in platelet count and vasoactive-ionotropic score (VIS).

RESULTS

Of 101 patients, 44 received epoprostenol (43.6%), 38 received heparin (37.6%), and 19 received citrate (18.8%). The first filter change was more commonly planned in patients receiving anticoagulation with epoprostenol (43%) as compared to citrate (11%) or heparin (29%) (p = 0.034). Of those patients where the first filter change was unintended (n = 33), there were greater median hours until the filter was replaced in those receiving epoprostenol (29) when compared to citrate (21) (p = 0.002) or heparin (18) (p = 0.003). There was a smaller median ratio of filters used to days on therapy in the patients that received epoprostenol (0.53) when compared to citrate (1) (p = 0.003) or heparin (0.75) (p = 0.001). For those receiving epoprostenol, there was no significant decrease in platelet count when comparing values prior to CRRT initiation through 7 days of therapy. There was no significant difference in VIS when comparing values prior to CRRT initiation through the first 2 days of CRRT.

CONCLUSIONS

Epoprostenol-based anticoagulation is effective when compared to other anticoagulation strategies used in pediatric CRRT with a favorable side effect profile.

Clinical effect of regional citrate anticoagulation continuous renal replacement therapy in three patients with hypercalcemic crisis

In this study, we investigated the effectiveness of regional citrate anticoagulation continuous renal replacement therapy (RCA-CRRT) in reducing blood calcium levels in three patients with hypercalcemia crisis caused by different etiologies. The sodium citrate chelation of calcium ions was utilized as an anticoagulant for treating severely affected patients. By adjusting the citrate anticoagulant dose and monitoring treatment indicators, RCA-CRRT parameters were actively modified to alleviate the hypercalcemia crisis and provide time for surgery or specialized treatment. Two patients experienced rapid and effective reductions in blood calcium levels, allowing for further treatment, while the third patient exhibited a repeated increase in blood calcium, which eventually decreased after parathyroid adenoma resection, leading to clinical discharge. Our findings suggest that RCA-CRRT can help alleviate hypercalcemia crisis, stabilize the patient's internal environment, and provide valuable time for clinical treatment in cases of various medical conditions causing abnormal blood calcium elevations.

Construction and validation of a prediction model for the risk of citrate accumulation in patients with hepatic insufficiency receiving continuous renal replacement therapy with citrate anticoagulation

BACKGROUND

To construct and validate a prediction model of the risk of citrate accumulation in patients with hepatic dysfunction receiving continuous renal replacement therapy with regional citrate anticoagulation (RCA-CRRT), which reduces the risk of citrate accumulation.

METHODS

All patients who received RCA-CRRT from 2021 to 2022 and were hospitalized in the First Affiliated Hospital of Zhejiang University were considered for study participation. Logistic regression analysis was used to identify the risk factors for citrate accumulation, based on which a nomogram model was constructed and validated in the validation group.

RESULTS

Six factors were finally identified, from which a nomogram was created to predict the risk of citrate accumulation. The area under the curve of the prediction model was 0.814 in the training group and 0.819 in the validation group, and the model showed acceptable agreement between the actual and predicted probabilities. Decision curve analysis also demonstrated that the model was clinically useful.

CONCLUSIONS

The model constructed from six factors reliably predicted the risk of citrate accumulation in patients with hepatic insufficiency who received RCA-CRRT.

Nafamostat mesylate versus regional citrate anticoagulation for continuous renal replacement therapy in patients at high risk of bleeding: a retrospective single-center study

PURPOSE

The choice of continuous renal replacement therapy (CRRT) anticoagulation program for patients at high risk of bleeding has always been a complex problem in clinical practice. Clinical regimens include regional citrate anticoagulation (RCA) and nafamostat mesylate (NM). This study aimed to evaluate the efficacy and safety of these two anticoagulants for CRRT in patients at high risk of bleeding to guide their clinical use better.

PATIENTS AND METHODS

Between January 2021 and December 2022, 307 patients were screened for this study. Forty-six patients were finally enrolled: 22 in the regional citrate anticoagulation group and 24 in the nafamostat mesylate group. We collected patients' baseline characteristics, laboratory indicators before CRRT, and CRRT-related data. We then performed a statistical analysis of the data from both groups of patients.

RESULTS

In our study, the baseline characteristics did not differ significantly between the two groups; the baseline laboratory indicators before CRRT of patients in the two groups were not significantly different. The duration of CRRT was 600 min in the regional citrate anticoagulation (RCA) group, 615 min in the nafamostat mesylate (NM) group; the success rate was 90.7% in the RCA group, and 85.6% in the NM group, the anticoagulant efficacy between the two groups was comparable. There was no significant difference in the safety of anticoagulation between the two groups. We used Generalized Estimating Equations (GEE) to test whether different anticoagulation methods significantly affected the success rate of CRRT and found no statistical difference between RCA and NM.

CONCLUSION

Our study suggests that nafamostat mesylate's anticoagulant efficacy and safety are not inferior to regional citrate anticoagulation for continuous renal replacement therapy in patients at high risk of bleeding.

Hypercitratemia is a mortality predictor among patients on continuous venovenous hemodiafiltration and regional citrate anticoagulation

The use of regional citrate anticoagulation (RCA) in liver failure (LF) patients can lead to citrate accumulation. We aimed to evaluate serum levels of citrate and correlate them with liver function markers and with the Cat/Cai in patients under intensive care and undergoing continuous venovenous hemodiafiltration with regional citrate anticoagulation (CVVHDF-RCA). A prospective cohort study in an intensive care unit was conducted. We compared survival, clinical, laboratorial and dialysis data between patients with and without LF. Citrate was measured daily. We evaluated 200 patients, 62 (31%) with LF. Citrate was significantly higher in the LF group. Dialysis dose, filter lifespan, systemic ionized calcium and Cat/Cai were similar between groups. There were weak to moderate positive correlations between Citrate and indicators of liver function and Cat/Cai. The LF group had higher mortality (70.5% vs. 51.8%, p = 0.014). Citrate was an independent risk factor for death, OR 11.3 (95% CI 2.74-46.8). In conclusion, hypercitratemia was an independent risk factor for death in individuals undergoing CVVHDF-ARC. The increase in citrate was limited in the LF group, without clinical significance. The correlation between citrate and liver function indicators was weak to moderate.

Simplified regional citrate anticoagulation protocol for CVVH, CVVHDF and SLED focused on the prevention of KRT-related hypophosphatemia while optimizing acid-base balance

BACKGROUND

Hypophosphatemia is a common electrolyte disorder in critically ill patients undergoing prolonged kidney replacement therapy (KRT). We evaluated the efficacy and safety of a simplified regional citrate anticoagulation (RCA) protocol for continuous venovenous hemofiltration (CVVH), continuous venovenous hemodiafiltration (CVVHDF) and sustained low-efficiency dialysis filtration (SLED-f). We aimed at preventing KRT-related hypophosphatemia while optimizing acid-base equilibrium.

METHODS

KRT was performed by the Prismax system (Baxter) and polyacrylonitrile AN69 filters (ST 150, 1.5 m2, Baxter), combining a 18 mmol/L pre-dilution citrate solution (Regiocit 18/0, Baxter) with a phosphate-containing solution (HPO42- 1.0 mmol/L, HCO3- 22.0 mmol/L; Biphozyl, Baxter). When needed, phosphate loss was replaced with sodium glycerophosphate pentahydrate (Glycophos™ 20 mmol/20 mL, Fresenius Kabi Norge AS, Halden, Norway). Serum citrate measurements were scheduled during each treatment. We analyzed data from three consecutive daily 8-h SLED-f sessions, as well as single 72-h CVVH or 72-h CVVHDF sessions. We used analysis of variance (ANOVA) for repeated measures to evaluate differences in variables means (i.e. serum phosphate, citrate). Because some patients received phosphate supplementation, we performed analysis of covariance (ANCOVA) for repeated measures modelling phosphate supplementation as a covariate.

RESULTS

Forty-seven patients with acute kidney injury (AKI) or end stage kidney disease (ESKD) requiring KRT were included [11 CVVH, 11 CVVHDF and 25 SLED-f sessions; mean Acute Physiology and Chronic Health Evaluation II (APACHE II) score 25 ± 7.0]. Interruptions for irreversible filter clotting were negligible. The overall incidence of hypophosphatemia (s-P levels <2.5 mg/dL) was 6.6%, and s-P levels were kept in the normality range irrespective of baseline values and the KRT modality. The acid-base balance was preserved, with no episode of citrate accumulation.

CONCLUSIONS

Our data obtained with a new simplified RCA protocol suggest that it is effective and safe for CVVH, CVVHDF and SLED, allowing to prevent KRT-related hypophosphatemia and maintain the acid-base balance without citrate accumulation.

TRIAL REGISTRATION

NCT03976440 (registered 6 June 2019).

Management of regional citrate anticoagulation for continuous renal replacement therapy: guideline recommendations from Chinese emergency medical doctor consensus

Continuous renal replacement therapy (CRRT) is widely used for treating critically-ill patients in the emergency department in China. Anticoagulant therapy is needed to prevent clotting in the extracorporeal circulation during CRRT. Regional citrate anticoagulation (RCA) has been shown to potentially be safer and more effective and is now recommended as the preferred anticoagulant method for CRRT. However, there is still a lack of unified standards for RCA management in the world, and there are many problems in using this method in clinical practice. The Emergency Medical Doctor Branch of the Chinese Medical Doctor Association (CMDA) organized a panel of domestic emergency medicine experts and international experts of CRRT to discuss RCA-related issues, including the advantages and disadvantages of RCA in CRRT anticoagulation, the principle of RCA, parameter settings for RCA, monitoring of RCA (mainly metabolic acid-base disorders), and special issues during RCA. Based on the latest available research evidence as well as the paneled experts' clinical experience, considering the generalizability, suitability, and potential resource utilization, while also balancing clinical advantages and disadvantages, a total of 16 guideline recommendations were formed from the experts' consensus.

Impact of Continuous Veno-Venous HemoDiALYsis with Regional Citrate Anticoagulation on Non-NUTRItional Calorie Balance in Patients on the ICU-The NUTRI-DAY Study

Background: Malnutrition as well as overfeeding can have negative impacts on clinical outcomes in critically ill patients. Continuous veno-venous hemodialysis (CVVHD) with regional citrate anticoagulation (RCA) using trisodium citrate 4% (TSC) might play a role in nutrient disposition in patients in the ICU. Methods: In 33 consecutive patients on CVVHD with RCA, energy uptake or loss was calculated. Three macronutrients (lactate, glucose and citrate) were analyzed by taking prefilter blood and effluent samples. Results: Glucose and lactate clearance through CVVHD made up for a loss of 61 kcal/d (IQR 25−164 kcal/d) and 38 kcal/d (IQR 23−59 kcal/d), respectively. Two patients with hyperglycemic state (>350 mg/dL) lost around 600 kcal/d during CVVHD. Net post-filter citrate caloric delivery through RCA was 135 kcal/d (IQR: 124−144 kcal/d). Adding the three macronutrients, net caloric gain through CVVHD was 10 kcal/d (IQR: −63−75 kcal/d). Conclusion: In non-hyperglycemic patients on CVVHD with RCA, the metabolic contribution of the three macronutrients lactate, glucose and citrate is neglectable.

A prospective study on serum citrate levels and clinical correlations in patients receiving regional citrate anticoagulation

Background

Current ways to diagnose citrate accumulation (CA) in patients receiving regional citrate anticoagulation (RCA) continuous renal replacement therapy (CRRT) are confounded by various clinical factors. Serum citrate measurement emerges as a more direct way to diagnose CA, but its clinical utility and optimal cut-off values remain undefined. This study examined serum citrate kinetics and its diagnostic performance for CA in patients receiving RCA CRRT.

Methods

A multicentre prospective study was carried out in two tertiary referral centre intensive care units in Hong Kong with serum citrate levels measured at baseline and 2, 6, 12, 24, 36, 48 and 72 h after initiation of RCA CRRT and their relationships with the development of CA.

Results

Among the 133 patients analysed, 18 patients (13.5%) developed CA. The serum citrate levels at baseline and 2, 6 and 12 h after initiation of RCA CRRT in patients who had CA were significantly higher than the non-CA group (P < .001 for all). The CA group also had higher serum citrate levels than the non-CA group {median 0.93 mmol/L [interquartile range (IQR) 0.81-1.16) versus 0.37 mmol/L (IQR 0.26-0.57), P < .001}. Using a cut-off of 0.85 mmol/L, the serum citrate level had a sensitivity of 0.77 and a specificity 0.96 for the diagnosis of CA [area under the receiver operating characteristics curve (AUROC) 0.90, P < .001]. The 2-h and 6-h serum citrate levels had good discriminatory abilities for predicting subsequent development of CA (AUROC 0.86 and 0.83 for 2-h and 6-h citrate levels using cut-off values of 0.34 and 0.63 mmol/L, respectively; P < .001).

Conclusion

Serum citrate levels were significantly higher in patients with CA compared with patients without CA. Serum citrate levels showed good performance in diagnosing and predicting the development of CA.

Automated regional citrate anticoagulation based on online monitoring of ionized calcium concentration: Proof of concept

BACKGROUND

Regional citrate anticoagulation (RCA), a complex and effective technique, is recommended as the anticoagulation of choice for continuous renal replacement therapy. One of its key objectives is to keep the ionized calcium in the targeted range. In this study, we aimed to develop an automated RCA based on online monitoring of the ionized calcium concentration and closed-loop feedback.

METHODS

We constructed calcium-selective electrodes with liquid inner contact, which measured a potentiometric signal as the output. We tested the responses, stability, and selectivity of the electrodes in flowing fluid containing calcium chloride. We compared the measurement accuracy between the electrodes and an i-STAT system in vivo. Moreover, we established closed-loop feedback using a proportional-integral-derivative controller model. We performed simulated automated RCA both in vivo and in vitro.

RESULTS

The electrode gave a Nernstian response to the variation of ionized calcium concentration. It showed high stability and a relatively short response time. Changes in the fluid flow rate, solution PH, and addition of metal ions including Mg²⁺ and K⁺ did not interfere with the measurements of ionized calcium. These measurements in whole blood by the electrode were very close to those assessed by the i-STAT system. The feedback control system responded quickly to an abnormal ionized calcium concentration and regulated the infusion rates of calcium or citrate to maintain the concentration of ionized calcium within the targeted range.

CONCLUSIONS

We successfully trialed automated RCA, which may help simplify the complexities of RCA in the future.

A Comparison of the Commonly Used Surrogate Markers for Citrate Accumulation and Toxicity during Continuous Renal Replacement Therapy with Regional Citrate Anticoagulation

INTRODUCTION

Continuous renal replacement therapy using regional citrate anticoagulation is commonly used as a modality of organ support in the critically ill population. Currently, citrate accumulation or toxicity is assessed using surrogate markers, notably the uncorrected total-to-ionized calcium ration. The accuracy and utility of this method have been questioned.

OBJECTIVES/AIMS

The aim of this study was to compare the surrogate markers used for assessing citrate accumulation or toxicity using the measurement of plasma citrate as the gold standard.

METHODS

Blood was sampled from 20 patients before, during, and after episodes of filtration with citrate concentration measured using spectrophotometry. Demographic and other clinical and biochemical data were also collected. According to protocol, a 15 mmol/L solution of trisodium citrate was used as the prefilter anticoagulant. Results were analyzed using STATA (v16.0) and presented as mean (SD), median (IQR), or simple proportion. Univariate linear regression using citrate concentration as the dependent variable was performed with all surrogate markers.

RESULTS

Twenty patients (17 males) were enrolled in the study with a mean (SD) age of 62.7 (9.9) years. The uncorrected calcium ratio had the best fit to the citrate data with an R2 value of 0.39. The albumin-corrected calcium ratio, pH, anion gap (AG), albumin-corrected AG, standard base excess, and strong ion gap all had R2 values less than 0.05.

CONCLUSION(S)

In the absence of direct measurement of citrate concentration, uncorrected total-to-ionized calcium ratio is superior to other surrogate markers, though not ideal, in assessing citrate accumulation or toxicity.

Review of Anticoagulation in Continuous Renal Replacement Therapy

Continuous renal replacement therapy is an important, yet challenging, treatment of critically ill patients with kidney dysfunction. Clotting within the dialysis filter or circuit leads to time off therapy and impaired delivery of prescribed treatment. Anticoagulation can be used to prevent this complication; however, doing so introduces risk for unintended complications such as bleeding or metabolic derangements in patients who are already critically ill. A thorough understanding of indications, therapeutic options, and monitoring principles is necessary for safe and effective use of this strategy. This review provides clinicians important information regarding when to anticoagulate, differences in pharmacologic agents, recommended doses, routes of drug delivery, and appropriate laboratory monitoring for patients receiving anticoagulation to support continuous renal replacement therapy.

Feasibility and efficacy of modified fixed citrate concentration protocol using only commercial preparations in critically ill patients: a prospective cohort study with a historical control group

BACKGROUND

The cumbersome program and the shortage of commercial solution hindered the regular application of regional citrate anticoagulation (RCA). It is urgent to simplify the protocol using only commercial preparations. The aim of this study was to explore the feasibility and efficacy of the modified protocol for continuous veno-venous hemofiltration (CVVH) in unselected critically ill patients.

METHODS

A prospective cohort study was conducted in 66 patients who received a new protocol combining fixed citrate concentration with modified algorithm for supplements (i.e., fixed protocol), and compared the efficacy, safety and convenience for this group to a historical control group with a traditional protocol (n = 64), where citrate was titrated according to the circuit ionized calcium concentration (i.e., titrated protocol). The convenience was defined as the demand for monitoring test and dose adjustment of any supplement.

RESULTS

The filter lifespan was 63.2 ± 16.1 h in the fixed group and 51.9 ± 17.7 h in the titrated group, respectively. Kaplan-Meier survival analysis demonstrated longer circuit lifetime for fixed group (log-rank, p = 0.026). The incidence of circuit clotting was lower in the fixed protocol (15.2% vs. 29.7% in the titrated protocol, p = 0.047). Moreover, compared with the titrated group, patients with fixed protocol had less demand for monitoring test and dose adjustment of any supplement (the number of times per person per day) (3.3 [IQR 2.3-4.5] vs. 5.7 [IQR 3.3-6.9], p = 0.001 and 1.9 [IQR 0.5-2.7] vs. 6.3 [IQR 4.2-7.9], p < 0.001; respectively). No new onset bleeding complications occurred in all patients. The overall incidence of suspected citrate accumulation was 4.6% and there was no difference between the two groups (p = 0.969), yet a lower rate of metabolic alkalosis was found in the fixed group (3.0% vs. 14.1%, p = 0.024).

CONCLUSIONS

Our modified fixed citrate concentration protocol is feasible, safe and effective to enhance the circuit lifespan and the convenience of implementation while maintaining a similar safety when compared to the traditional protocol. Using only commercial preparations may be helpful for widespread application of RCA.

TRIAL REGISTRATION

Clinicaltrials.gov. NCT02663960 . Registered 26 January 2016.

Anticoagulation strategies in continuous renal replacement therapy

The most common anticoagulant options for continuous renal replacement therapy (CRRT) include unfractionated heparin (UFH), regional citrate anticoagulation (RCA), and no anticoagulation. Less common anticoagulation options include UFH with protamine reversal, low-molecular weight heparin (LMWH), thrombin antagonists, and platelet inhibiting agents. The choice of anticoagulant for CRRT should be determined by patient characteristics, local expertise, and ease of monitoring. The Kidney Disease Improving Global Outcomes (KDIGO) acute kidney injury guidelines recommend using RCA rather than UFH in patients who do not have contraindications to citrate and are with or without increased risk of bleeding. Monitoring should include evaluation of the anticoagulant effect, circuit life, filter efficacy, and complications.

Measurement of the Concentration of Citrate in Human Biofluids in Patients Undergoing Continuous Renal Replacement Therapy Using Regional Citrate Anticoagulation: Application of a Two-Step Enzymatic Assay

BACKGROUND

Continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA) is now commonly used to treat acute kidney injury in critically ill patients. The concentration of citrate is not routinely measured, with citrate accumulation and/or toxicity primarily assessed using surrogate measures.

OBJECTIVES

The aim of this study was to measure the concentration of citrate in plasma and ultrafiltrate in patients receiving CRRT with RCA using a modified commercial enzymatic assay.

METHODS

After meeting inclusion criteria, blood was sampled from 20 patients before, during, and after episodes of filtration. Using spectrophotometry, samples were tested for citrate concentration. Demographic and other clinical and biochemical data were also collected. Throughout, a 15 mmol/L solution of trisodium citrate was used as the prefilter anticoagulant. Results were analysed using STATA (v15.0) and presented as mean (SD), median (IQR), or simple proportion. Comparisons were made using either the Student t test or the Wilcoxon rank-sum test. Correlation was assessed using Pearson's r.

RESULTS

Twenty patients (17 males) were enrolled in the study. Mean (SD) age was 63.7 years (9.9). Median (IQR) ICU length of stay was 281 h (199, 422) with 85% undergoing intermittent positive pressure ventilation. Median APACHE 3 score was 95 (87, 117) with an overall 30% mortality rate. Median filtration time was 85 h (46, 149). No difference was found between pre- and post-filtration plasma citrate concentrations (79 µmol/L [50] vs. 71 µmol/L [42], p = 0.65). Mean citrate concentration during filtration was 508 µmol/L (221) with a maximum of 1,070 µmol/L. This was significantly higher than the pre/post levels (p < 0.001).

CONCLUSIONS

Plasma concentrations of citrate rose significantly during episodes of CRRT using RCA returning back to normal after cessation of treatment.

Sustained low-efficiency dialysis with regional citrate anticoagulation for patients with liver impairment in intensive care unit: A single-center experience

Regional citrate anticoagulation (RCA) is a recommended method for extracorporeal circuit anticoagulation during renal replacement therapy (RRT). Increased risk of citrate accumulation by default of hepatic metabolism limits its use in liver failure patients. A Ca_tot /Ca_ion ratio ≥2.5 is established as an indirect control of plasma citrate poisoning. To investigate the safety of RCA in patients with liver impairment during sustained low-efficiency dialysis (SLED), we conducted a retrospective study of 41 patients with acute or chronic hepatocellular failure requiring RRT between January 2014 and June 2015 in the intensive care unit of the Groupe Hospitalier Sud Ile de France. Sixty-seven SLED sessions were performed. At admission, 32 (78%) patients had acute liver dysfunction and nine (22%) patients had cirrhosis with a median MELD score of 27 (IQR: 18.8, 42.0). Despite a majority of poor prognosis patients (SAPS-II (Simplified Acute Physiology Score II) score 71 [IQR: 58; 87]), with acute liver impairment as a part of multi-organ failure, no dosage of Ca_tot /Ca_ion ratio after SLED sessions exceeded the critical threshold of 2.5. Of the 63 complete sessions, neither dyscalcemia nor major dysnatremia, nor extracorporeal circuit thrombosis were noticed. Observed acid-base disturbances (16.4%) were not significantly correlated with the Ca_tot /Ca_ion ratio (P = .2155). In this retrospective study using RCA during intermittent RRT in ICU patients with severe liver dysfunction, we did not observe any citrate accumulation but monitoring of acid-base status and electrolytes remains necessary to ensure technique safety.

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.

Regional citrate anticoagulation versus no-anticoagulation for continuous venovenous hemofiltration in patients with liver failure and increased bleeding risk: A retrospective case-control study

Objective

There are controversial opinions on anticoagulation for continuous venovenous hemofiltration (CVVH) in patients with liver failure (LF) and increased bleeding risk. Therefore, we conducted a retrospective study to evaluate the efficacy and safety of regional citrate anticoagulation (RCA) versus no-anticoagulation for CVVH in these patients.

Methods

The included patients were divided into RCA and no-anticoagulation group according to the CVVH anticoagulation strategy they accepted for CVVH. Filter lifespan, bleeding, citrate accumulation, catheter occlusion, and totCa/ionCa ratio were evaluated as outcomes.

Results

In the original cohort, the filter lifespan of the RCA group (41 patients, 79 filters) was significantly longer than the no-anticoagulation group (62 patients, 162 filters) (> 72 hours vs 39.5 hours (IQR 31.2–47.8), P = 0.002). The adjusted results demonstrated that RCA could significantly reduce the risk of filter failure (HR = 0.459, 95%CI 0.26–0.82, P = 0.008). Four episodes of totCa/ionCa > 2.5 were observed in the RCA group and continuously accepted RCA-CVVH after the reduction of citrate dose and blood flow. No obvious citrate accumulation was observed in these patients. In the matched cohort, the filter lifespan of the RCA group was significantly longer than the no-anticoagulation group (P = 0.013) as well. No significant difference in the episodes of totCa/ionCa > 2.5 was observed between the two matched groups (P = 0.074). Both in the original cohort and the matched cohort, the bleeding, acidosis, alkalosis, and catheter occlusion incidences were not significantly different between the two groups.

Conclusions

In LF patients with increased bleeding risk who underwent CVVH, RCA could prolong the filter lifespan and be safely used with careful blood gas monitoring and citrate dose adjusting. Further prospective, randomized, control studies are warranted to obtain robust evidences.

Regional citrate anticoagulation for continuous renal replacement therapy

PURPOSE OF REVIEW

The delivery of an effective dialysis dose in continuous renal replacement therapy (CRRT) depends on adequate anticoagulation of the extracorporeal circuit. In most patients, either systemic heparin anticoagulation (SHA) or regional citrate anticoagulation (RCA) is used. This review will outline the basics and rationale of RCA and summarize data on safety and efficacy of both techniques.

RECENT FINDINGS

The basic principle of RCA is to reduce the level of ionized calcium in the extracorporeal circuit via infusion of citrate. This way, effective anticoagulation restricted to the extracorporeal circuit is achieved. SHA and RCA were compared in a variety of studies. RCA significantly prolonged filter lifetime, reduced bleeding complications and provided excellent control of uremia and acid-base status. RCA was also safe in the majority of patients with impaired liver function, whereas caution must be exerted in those with severe multiorgan failure and persistent hyperlactatemia.

SUMMARY

RCA per se is safe and effective for anticoagulation of CRRT. Compared to SHA, efficacy of anticoagulation is improved and adverse effects are reduced. RCA can be recommended as the anticoagulation mode of choice for CRRT in most ICU patients.

Protective Effect of Citric Acid Against Hepatic Ischemia Reperfusion Injury in Sprague-Dawley Rats

OBJECTIVE

Hepatic ischemia reperfusion (I/R) injury is regarded as a serious concern in clinical practice. Citric acid reduces oxidative stress and inflammation during hypoxia and reoxygenation. Our objective was to investigate the protective effect of citric acid against hepatic I/R injury in rats.

METHODS

We fed Sprague-Dawley rats either citric acid (100 mg/kg/d) or saline. One week later, ischemia was induced by clamping the rats' common hepatic artery and portal vein for 30 minutes. The rats were randomly divided into 3 major groups that were treated as follows: 1. the sham operated group; 2. the I/R group; and 3. the I/R-citric acid group.

RESULTS

Compared to the sham group, the I/R group had higher expression of aspartate aminotransferase and alanine aminotransferase and lower expression of catalase, superoxide dismutase, glutathione peroxidase, antioxidant, nitric oxide, and albumin. Compared to the I/R group, the I/R-citric acid group had higher expression of catalase, superoxide dismutase, antioxidants, and nitric oxide, and lower expression of aspartate aminotransferase and alanine aminotransferase.

CONCLUSIONS

These results suggest that citric acid therapy has significant therapeutic potential in ischemic liver injury.

In silico model of the dilutional effects of conventional component therapy versus whole blood in the management of massively bleeding adult trauma patients

BACKGROUND

There are multiple approaches to the blood product and fluid resuscitation of a bleeding trauma patient. An in silico model of different trauma resuscitation strategies was constructed to predict their effects on the volumes of the different body fluid compartments and on several important hemostatic factors.

STUDY DESIGN AND METHODS

This multicompartment dynamic deterministic model comprised four interconnected modules (hemostatic, resuscitation, body fluid compartment, and dilutional coagulopathy). The model was divided into five resuscitation phases with simulations using six different resuscitation strategies: whole blood (WB) only, conventional component therapy (CCT) only or 10 units of WB followed by CCT, with either 1 L of crystalloid or 1.5 units of WB or red blood cells in the prehospital phase.

RESULTS

At the end of the simulations using 1 L of crystalloid fluids in the prehospital resuscitation phase, the use of WB led to a 1.4 g/dL higher hemoglobin concentration, 32 mg/dL higher fibrinogen concentration, and 0.9 L lower total extracellular fluid volume compared to CCT. Prehospital blood product transfusion in place of crystalloid resulted in higher hemoglobin and fibrinogen concentrations and a lower international normalized ratio throughout the resuscitation regardless of the resuscitation strategy used. Throughout both the prehospital crystalloid and prehospital blood product transfusion simulations, the hemoglobin and fibrinogen concentrations and platelet counts were higher, and the international normalized ratio was lower, when WB was used compared to CCT.

CONCLUSIONS

This model predicted improved hemostatic factor levels and a smaller total extracellular fluid volume volume when WB was transfused instead of CCT to bleeding trauma patients.

[Regional citrate anticoagulation in renal replacement therapy in the intensive care station : Recommendations from the renal section of the DGIIN, ÖGIAIN and DIVI]

BACKGROUND

Regional citrate anticoagulation (RCA) in continuous renal replacement therapy can effectively anticoagulate dialysis circuits without having adverse effects on systemic heparin application. In particular, in continuous renal replacement therapy RCA is well established and represents a safe procedure with longer filter lifetimes and fewer bleeding complications.

OBJECTIVES

To provide guidance on the indications, advantages and disadvantages, and use of RCA, current recommendations from the renal section of the DGIIN (Deutschen Gesellschaft für Internistische Intensivmedizin und Notfallmedizin), ÖGIAIN (Österreichischen Gesellschaft für Internistische und Allgemeine Intensivmedizin und Notfallmedizin) and DIVI (Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin) are stated.

MATERIALS AND METHODS

The recommendations in this paper are based on the current KDIGO (Kidney Disease: Improving Global Outcomes) guidelines, other published guidelines and protocols as well as the expert knowledge and clinical experience of the authors.

RESULTS

The use of commercially available machines with coupled pumps and integrated safety features, effective personal training and standardized protocols for clinical usage (SOP) is particularly important for the safe clinical use of RCA in renal replacement therapy. Contrary to previous recommendations, even liver failure or shock with lactic acidosis may no longer be an absolute contra-indication for RCA. However, these particular patients have to be carefully monitored for signs of citrate accumulation.

Long-term continuous renal replacement therapy and anticoagulation with citrate in critically ill patients with severe liver dysfunction

Background

As of 2009, anticoagulation with citrate was standard practice in continuous renal replacement therapy (CRRT) for critically ill patients at the University Medical Centre of Saarland, Germany. Partial hepatic metabolism of citrate means accumulation may occur during CRRT in critically ill patients with impaired liver function. The aim of this study was to evaluate the actual influence of hepatic function on citrate-associated complications during long-term CRRT.

Methods

In a retrospective study conducted between January 2009 and November 2012, all cases of dialysis therapy performed in the interdisciplinary surgical intensive care unit were analysed. Inclusion criteria were CRRT and regional anticoagulation with citrate, pronounced liver dysfunction, and pathologically reduced indocyanine green plasma disappearance rate (ICG-PDR).

Results

A total of 1339 CRRTs were performed in 69 critically ill patients with liver failure. At admission, the mean Model for End-stage Liver Disease score was 19.2, and the mean ICG-PDR was 9.8%. Eight patients were treated with liver replacement therapy, and 30 underwent transplants. The mortality rate was 40%. The mean duration of dialysis was 19.4 days, and the circuit patency was 62.2 h. Accumulation of citrate was detected indirectly by total serum calcium/ionised serum calcium (tCa/iCa) ratio > 2.4. This was noted in 16 patients (23.2%). Dialysis had not to be discontinued for metabolic disorder or accumulation of citrate in any case. In 26% of cases, metabolic alkalosis occurred with pH > 7.5. Interestingly, no correlation between citrate accumulation and liver function parameters was detected. Moreover, most standard laboratory liver function parameters showed poor predictive capabilities for accumulation of citrate.

Conclusions

Our findings indicate that extra-hepatic metabolism of citrate seems to exist, avoiding in most cases citrate accumulation in critically ill patients despite impaired liver function. Because the citric acid cycle is oxygen-dependent, disturbed microcirculation would result in inadequate citrate metabolism. Raising the tCa/iCa ratio would therefore be an indicator of severity of illness and mortality rather than of liver failure. However, further studies are warranted for confirmation.

Heparin-Free Prolonged Intermittent Hemodialysis Using Calcium-Free Citrate Dialysate in Critically Ill Patients

OBJECTIVES

Critically ill patients who have a high risk of bleeding but require prolonged intermittent dialysis need a heparin-free easy-to-use alternative type of anticoagulation within the dialysis circuit. We assessed the safety and efficiency of heparin-free regional citrate anticoagulation of the dialysis circuit using a calcium-free citrate-containing dialysate, with calcium reinjected according to ionic dialysance.

DESIGN

Prospective cohort study.

SETTING

Critical care units.

PATIENTS

Critically ill patients who required renal replacement therapy.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 101 dialysis sessions were performed in 35 patients (mechanical ventilation n = 78; norepinephrine n = 13). Median duration of dialysis was 294 minutes (interquartile range, 240-300), and median ultrafiltration volume was 2.3 L (1-2.8). Urea and β2-microglobulin reduction rates were 64.5% ± 0.4% and 48% ± 0.13%, respectively. Postfilter ionized calcium was 0.35 ± 0.17 and 0.38 ± 0.14 mmol/L at 1 and 3 hours, respectively, within the extracorporeal circuit. A major clotting event that led to premature termination of the session occurred in only three of 101 sessions. In these three cases, major catheter dysfunction occurred before clotting within the circuit. Prefilter ionized calcium remained within narrow ranges (before/after change +0.07 ± 0.006 mmol/L), and total-to-ionized calcium ratio, a surrogate marker for citratemia, was unchanged.

CONCLUSIONS

Dialysis anticoagulation with calcium-free citrate-containing dialysate and calcium reinjection according to ionic dialysance is an easy-to-use, efficient, and inexpensive form of heparin-free regional anticoagulation. It allows prolonged hemodialysis sessions in critically ill patients without the need to systemically monitor ionized calcium. Furthermore, sessions can be safely extended according to the hemodynamic tolerance to ensure an adequate dose of dialysis and a negative water balance, a major point in patients with severe acute kidney disease.

Is Regional Citrate Anticoagulation the Future of Hemodialysis?

Citrate has many characteristics of the ideal anticoagulant for hemodialysis. In addition to immediate and complete anticoagulation in the dialysis circuit, citrate has important effects beyond anticoagulation, mainly in reducing inflammatory response induced by hemodialysis. Citrate has already become the standard anticoagulant in acute kidney injury requiring continuous renal replacement therapy (CRRT), both for adults and children, with the citrate module being a part of modern CRRT monitors. Although the citrate module is not yet available for intermittent hemodialysis, precise infusion pumps, point-of-care ionometers and high citrate clearance from high flux dialyzers increase safety while reducing the risk of metabolic complications, both in adult and pediatric patients. Slovenia has a long tradition, high volume and expansion of citrate use in hemodialysis, including long-term citrate anticoagulation in selected patients. At the Department of Nephrology, University Medical Centre Ljubljana, more than 10 000 citrate procedures were performed in 2015. We believe that regional citrate anticoagulation may replace heparin as the main anticoagulant for intermittent hemodialysis in the not so distant future.

Hyperlactatemia, Lactate Kinetics and Prediction of Citrate Accumulation in Critically Ill Patients Undergoing Continuous Renal Replacement Therapy With Regional Citrate Anticoagulation

OBJECTIVES

Citrate accumulation is a major complication of regional citrate anticoagulation during continuous renal replacement therapy. We studied the prediction of citrate accumulation during continuous veno-venous hemodialysis with regional citrate anticoagulation by initial lactate concentrations and lactate kinetics.

DESIGN

A retrospective follow-up analysis from a cohort of critically ill patients.

SETTING

Mixed medical-surgical ICUs at a university hospital.

PATIENTS

All adult patients with acute kidney injury and treated with regional citrate anticoagulation-continuous veno-venous hemodialysis during a 3-year period (n = 1,070) were included in this retrospective study and screened for metabolic signs of citrate accumulation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The frequency of citrate accumulation during the first 48 hours of therapy was 2.26%. In patients with initial normal lactate (< 2.2 mmol/L), elevated lactate (≥ 2.2 to < 4 mmol/L), or severe hyperlactatemia (≥ 4 mmol/L), the frequency of citrate accumulation was 0.77%, 2.70%, and 6.33%, respectively. Receiver operating characteristics-area under the curve of initial lactate concentration was 0.789 for the prediction of citrate accumulation. Optimal cutoff from receiver operating characteristics (2.39 mmol/L) showed strong negative prediction (99.28%), but weak positive prediction (5.21%). The slope intercept of lactate kinetics over 48 hours was positive and significantly higher in patients with citrate accumulation compared to those without (+0.2 vs -0.006 mmol/L/hr; p < 0.001). In patients with initial severe hyperlactatemia (≥ 4 mmol/L), the median calculated lactate clearance at 6, 12, and 18 hours was 24.0%, 48.1%, and 59.4% in the nonaccumulation group. These clearance rates were significantly higher at each time-point compared to patients with citrate accumulation (-9.8%, -20.5%, and 2.3%, respectively; p < 0.001 for each time-point). The highest receiver operating characteristics-area under the curve for citrate accumulation was observed for 12-hour values of lactate clearance (area under the curve = 0.839; 95% CI, 0.751-0.927) with an optimal cut-off value of 24.3%.

CONCLUSIONS

Risk of citrate accumulation during regional citrate anticoagulation in a well-selected cohort of patients is low even in case of initial severe hyperlactatemia. Lactate kinetics rather than initially elevated lactate concentration should be considered in assessing the risk of citrate accumulation.

Renal replacement therapy and anticoagulation

Today, up to 20% of all intensive care unit patients require renal replacement therapy (RRT), and continuous renal replacement therapies (CRRT) are the preferred technique. In CRRT, effective anticoagulation of the extracorporeal circuit is mandatory to prevent clotting of the circuit or filter and to maintain filter performance. At present, a variety of systemic and regional anticoagulation modes for CRRT are available. Worldwide, unfractionated heparin is the most widely used anticoagulant. All systemic techniques are associated with significant adverse effects. Most important are bleeding complications and heparin-induced thrombocytopenia (HIT-II). Regional citrate anticoagulation (RCA) is a safe and effective technique. Compared to systemic anticoagulation, RCA prolongs filter running times, reduces bleeding complications, allows effective control of acid-base status, and reduces adverse events like HIT-II. In this review, we will discuss systemic and regional anticoagulation techniques for CRRT including anticoagulation for patients with HIT-II. Today, RCA can be recommended as the therapy of choice for the majority of critically ill patients requiring CRRT.

Albumin-corrected total/ionized calcium ratio is not superior to total/ionized calcium ratio as an indicator of citrate accumulation

BACKGROUND

Total/ionized calcium ratio has been used as an indirect index of increased plasma citrate concentration during citrate anticoagulation. However, they were obtained without any adjustment of total calcium for albumin. Herein, we investigated whether the albumin-corrected total/ionized calcium ratio performed better than total/ionized calcium ratio.

METHODS

20 critically ill patients were treated with continuous venovenous hemofiltration (CVVH) using citrate anticoagulation. The systemic total, ionized calcium and albumin levels were dynamically measured, and correlations between different calcium parameters and plasma citrate levels were analyzed.

RESULTS

The highest correlation was found between plasma citrate level and total/ionized calcium ratio at the third hour (R = 0.88, p<0.001). The albumin-corrected total/ionized calcium ratio was not superior to total/ionized calcium ratio.

CONCLUSIONS

The total/ionized calcium ratio at the third hour after the start of citrate-CVVH is an early and simple indicator to reflect increased plasma citrate level. Adjustment of systemic total calcium for serum albumin is not necessary.

Citrate shows protective effects on cardiovascular and renal function in ischemia-induced acute kidney injury

BACKGROUND

Ischemia and reperfusion (I/R) is one of the major causes of acute kidney injury (AKI). Citrate reduces hypoxia-induced mitochondrial energetic deficits in isolated proximal tubules. Moreover, citrate anticoagulation is now frequently used in renal replacement therapy. In the present study a rat model of I/R-induced AKI was utilized to examine renal protection by citrate in vivo.

METHODS

AKI was induced by bilateral renal clamping (40 min) followed by reperfusion (3 h). Citrate was infused at three different concentrations (0.3 mmol/kg/h; 0.6 mmol/kg/h and 1.0 mmol/kg/h) continuously for 60 min before and 45 min after ischemia. Plasma calcium concentrations were kept stable by infusion of calcium gluconate. The effect of citrate was evaluated by biomonitoring, blood and plasma parameters, histopathology and tissue ATP content.

RESULTS

In comparison to the normoxic control group bilateral renal ischemia led to an increase of creatinine and lactate dehydrogenase activity and a decrease in tissue ATP content and was accompanied by a drop in mean arterial blood pressure. Infusion of 1.0 mmol/kg/h citrate led to lower creatinine and reduced LDH activity compared to the I/R control group and a tendency for higher tissue ATP content. Pre-ischemic infusion of 1.0 mmol/kg/h citrate stabilized blood pressure during ischemia.

CONCLUSIONS

Citrate has a protective effect during I/R-induced AKI, possibly by limiting the mitochondrial deficit as well as by beneficial cardiovascular effects. This strengthens the rationale of using citrate in continuous renal replacement therapy and encourages consideration of citrate infusion as a therapeutic treatment for AKI in humans.

Effectiveness and Safety Assessment of Citrate Anticoagulation During Albumin Dialysis in Comparison to Other Methods of Anticoagulation

Liver failure is a serious and often deadly disease often requiring MARS (Molecular Adsorbent Recirculating System) therapy. Choosing the safe and effective method of anticoagulation during artificial liver support systems seems to be very difficult and extremely important. The aim of this study was to assess effectiveness and safety of regional anticoagulation with citrate in liver failure patients during MARS. We used a single center observational study. We analyzed 158 MARS sessions performed in 65 patients: 105 (66.5%) sessions in 41 patients with heparin anticoagulation, 40 (25.3%) sessions in 19 patients with citrate, and 13 (8%) sessions in only five patients without anticoagulation, that were excluded from part of the analysis. To determine the effectiveness of regional anticoagulation with citrate, probability of filter survival and changes in laboratory parameters were analyzed according to the applied method of anticoagulation. The safety of citrate was determined by Ca/Ca²⁺ ratio, acid-base balance, bleeding complications, and the need for blood product transfusions. The probability of filter survival in the citrate group was 94% and in the heparin group 82% (P = 0.204). There was no relationship between the method of anticoagulation and effectiveness of MARS therapy in lowering the levels of the analyzed parameters. Only one patient had a Ca/Ca²⁺ ratio higher than he safety margin. There were no statistically significant changes in pH and lactate level irrespective of anticoagulation; bicarbonate dropped significantly only in the heparin group (P = 0.03). The frequency of bleeding complications and the need for transfusions did not differ significantly between groups. Regional anticoagulation with citrate can be an effective and safe method of anticoagulation during MARS therapy, but requires attentive monitoring and further studies in liver failure patients.

Prostacyclin as an Anticoagulant for Continuous Renal Replacement Therapy in Children

Effective delivery of continuous renal replacement therapy (CRRT) depends on the longevity of the filter and circuit used in the CRRT machine. Safe and effective anticoagulation is crucial for maintaining the patency of these circuits. In children, heparin and citrate are the commonly used anticoagulants but they are limited by serious side effects and thus calls for meticulous monitoring. In conditions where neither of these can be used, prostacyclin can be an effective alternative. Prostacyclin is a platelet inhibitor that can be safely used as an efficient anticoagulant in CRRT. When combined with heparin, it induces a heparin-sparing effect, which can reduce the dosage and side effects of heparin. Furthermore, there is no need for performing time-consuming monitoring tests. Although prostacyclin seems to be an attractive option, there is scanty evidence about its use as an anticoagulant in CRRT in children. We review the evidence and practicalities, and propose a guideline for the use of prostacyclin as an anticoagulant in children requiring CRRT.

Sustained low-efficiency dialysis with regional citrate anticoagulation in medical intensive care unit patients with liver failure: A prospective study

PURPOSE

Patients with liver failure requiring dialysis are at increased risk for citrate accumulation during sustained low-efficiency dialysis (SLED). The aim of this study was to evaluate the feasibilty of citrate SLED in critical ill patients with liver failure and investigate predictive parameters regarding citrate accumulation.

MATERIALS AND METHODS

This is a prospective study in 24 medical intensive care unit patients with liver failure and a total of 43 SLED runs (maximum of 3 runs per patient) using citrate anticoagulation. Liver function was characterized before SLED using not only laboratory parameters but also determination of the plasma disappearance rate of indocyanine green. In addition, blood gas parameters as well total calcium and citrate in serum were measured at baseline and defined time points during SLED.

RESULTS

Accumulation of citrate could be observed in all SLED runs, which were nearly normalized until the end of SLED and 24 hours after SLED, respectively. However, the critical threshold of total calcium/ionized calcium on ratio of greater than 2.5 was exceeded in only 1 patient. Equalization of initial metabolic acidosis was possible without major disturbances of acid base and electrolyte status. Liver function parameters showed poor predicitve capabilities regarding citrate accumulation.

CONCLUSIONS

Despite substantial accumulation of citrate in serum, SLED is save and feasible in patients with liver failure using a citrate anticoagulation. Careful monitoring of electrolytes and acid base status is mandatory to ensure patient safety.

[Treatment of acute renal failure in Germany: Analysis of current practice]

BACKGROUND AND OBJECTIVES

There are currently no reliable data on the differential use of renal replacement therapy (RRT) options for critically ill patients with acute renal failure in Germany.

PATIENTS AND METHODS

A questionnaire-based survey was delivered to 2265 German intensive care units. The questionnaire contained 19 questions regarding RRT.

RESULTS

A total of 423 German intensive care units participated in the survey. The offered modalities of RRT varied significantly: the smaller the facility, the fewer different RRT options were available. Intermittent dialysis procedures were available in only 35% of hospitals with up to 400 beds. In university hospitals, hemodynamically unstable patients were exclusively treated by continuous RRT, whereas in hospitals with up to 400 beds, intermittent RRT was also used. In addition, treatment practice was also dependent on the specialization of the treating physicians: Isolated acute renal failure was treated more often intermittently by nephrologists compared to anesthesiologists (79.7 vs. 43.3%). Nephrologists also used extracorporeal RRT more often in cardiorenal syndrome (54.3 vs. 35.8%), whereas anesthesiologists preferred them in sepsis (37.3 vs. 23.1%). The choice of anticoagulant varied as well: Hospitals with up to 400 beds offered regional citrate anticoagulation in only 50% compared to 90% of university hospitals.

CONCLUSIONS

Currently, RRT treatment in acute renal failure on German intensive care units seems to be dependent on the size, local structures, and education of the intensivists rather than patient needs. Our results demonstrate the necessity to establish cross-disciplinary standards for the treatment of acute renal failure in German intensive care units.

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.

[Citrate anticoagulation in acute renal replacement therapy : Method of choice]

BACKGROUND

Anticoagulation is prerequisite for efficient continuous renal replacement therapy (CRRT). Premature clotting of the extracorporeal system leads to therapy interruptions, is costly, and causes relevant blood losses.

REGIONAL ANTICOAGULATION

Regional citrate anticoagulation (RCA) achieves reliable coagulation inhibition and is clearly superior to heparin with regard to filter survival time. Due to its mode of action, a bleeding risk can be excluded. RCA with the commercial machine solutions is safe and has been promoted as the new standard anticoagulant for CRRT. Bioincompatibility reactions like leukocyte degranulation and complement system activation are ameliorated under RCA.

DISCUSSION

An assumed survival advantage of RCA could not be confirmed. In case of severe liver insufficiency and lactic acidosis, RCA can lead to metabolic complications. Despite calcium supplementation, the calcium net balance of RCA is often negative. Long treatment durations can therefore cause secondary hyperparathyroidism and in extreme cases osteomalacia. RCA is also a valuable option in intermittent hemodialysis.

Continuous veno-venous hemofiltration using a phosphate-containing replacement fluid in the setting of regional citrate anticoagulation

PURPOSE

The need for prolonged anticoagulation and the occurrence of hypophosphatemia are well known drawbacks of continuous renal replacement therapies (CRRT). The aim was to evaluate the effects on acid-base status and serum phosphate of a regional citrate anticoagulation (RCA) protocol for continuous veno-venous hemofiltration (CVVH) combining the use of citrate with a phosphate-containing replacement fluid.

METHODS

In a small cohort of heart surgery patients undergoing CRRT for acute kidney injury, we adopted an RCA-CVVH protocol based on a commercially available citrate solution (18 mmol/l) combined with a recently introduced phosphate-containing replacement fluid (HCO3 -30 mmol/l, phosphate 1.2), aimed at preventing phosphate depletion.

RESULTS

In 10 high bleeding-risk patients, the RCA-CVVH protocol provided an adequate circuit lifetime (46.8 ± 30.3 h) despite the adoption of a low citrate dose and a higher than usual target circuit Ca2+ (≤0.5 mmol/l). Acid-base status was adequately maintained without the need for additional interventions on RCA-CVVH parameters and without indirect sign of citrate accumulation [(pH 7.43 (7.41-7.47), bicarbonate 24.4 mmol/l (23.2-25.6), BE 0 (-1.5 to 1.1), calcium ratio 1.97 (1.82-2.01); median (IQR)]. Serum phosphate was steadily maintained in a narrow range throughout RCA-CVVH days [1.1 mmol/l (0.9-1.4)]. A low amount of phosphorus supplementation (0.9 ± 2 g/day) was required in only 30% of patients.

CONCLUSIONS

Although needing further evaluation, the proposed RCA-CVVH protocol ensured a safe and effective RCA without electrolyte and/or acid-base derangements. CRRT-induced hypophosphatemia was prevented in most of the patients by the adoption of a phosphate-containing replacement solution, minimizing phosphate supplementation needs.

Incidence and outcome of metabolic disarrangements consistent with citrate accumulation in critically ill patients undergoing continuous venovenous hemodialysis with regional citrate anticoagulation

BACKGROUND

Systemic citrate accumulation is a complication of regional citrate anticoagulation (RCA) during continuous renal replacement therapy (CRRT). Our objective was to determine the incidence of clinical signs consistent with citrate accumulation in a large and representative cohort of intensive care unit patients undergoing RCA-CRRT.

METHODS

Patients treated with RCA-CRRT during 2008-2010 were retrospectively analyzed. Decreased systemic ionized calcium (iCa), increased demand for calcium substitution, elevated total calcium to iCa ratio, and metabolic acidosis were evaluated as indicators for citrate accumulation.

RESULTS

In the 3-year period, 1070 patients were treated with RCA-continuous venovenous hemodialysis. Metabolic signs of citrate accumulation occurred in 32 patients (2.99%, 64.5 ± 14.0 years, 65.6% male, Acute Physiology and Chronic Health Evaluation score 34.2 ± 9.7): systemic iCa decreased to 1.01 ± 0.10 mmol/L with a simultaneous increase of the calcium substitution rate to 129% ± 26%, and the mean total calcium to iCa ratio increased to 2.51 ± 0.54. All 32 patients had therapy-resistant shock with severe lactic acidosis (pH 7.20 ± 0.11, lactate 136 ± 61 mg/dL), indicating severe intracellular hypoxia. None of the patients survived.

CONCLUSIONS

The incidence of disarrangements consistent with citrate accumulation in patients undergoing RCA-continuous venovenous hemodialysis was low, taking place exclusively in patients with severe lactic acidosis due to multiorgan failure. This suggests that the appearance of citrate accumulation is secondary to a severe failure of cellular respiration.

Continuous venovenous hemodiafiltration with a low citrate dose regional anticoagulation protocol and a phosphate-containing solution: effects on acid-base status and phosphate supplementation needs

BACKGROUND

Recent guidelines suggest the adoption of regional citrate anticoagulation (RCA) as first choice CRRT anticoagulation modality in patients without contraindications for citrate. Regardless of the anticoagulation protocol, hypophosphatemia represents a potential drawback of CRRT which could be prevented by the adoption of phosphate-containing CRRT solutions. The aim was to evaluate the effects on acid-base status and phosphate supplementation needs of a new RCA protocol for Continuous Venovenous Hemodiafiltration (CVVHDF) combining the use of citrate with a phosphate-containing CRRT solution.

METHODS

To refine our routine RCA-CVVH protocol (12 mmol/l citrate, HCO3- 32 mmol/l replacement fluid) (protocol A) and to prevent CRRT-related hypophosphatemia, we introduced a new RCA-CVVHDF protocol (protocol B) combining an 18 mmol/l citrate solution with a phosphate-containing dialysate/replacement fluid (HCO3- 30 mmol/l, Phosphate 1.2). A low citrate dose (2.5-3 mmol/l) and a higher than usual target circuit-Ca(2+) (≤ 0.5 mmol/l) have been adopted.

RESULTS

Two historical groups of heart surgery patients (n = 40) underwent RCA-CRRT with protocol A (n = 20, 102 circuits, total running time 5283 hours) or protocol B (n = 20, 138 circuits, total running time 7308 hours). Despite higher circuit-Ca(2+) in protocol B (0.37 vs 0.42 mmol/l, p < 0.001), circuit life was comparable (51.8 ± 36.5 vs 53 ± 32.6 hours). Protocol A required additional bicarbonate supplementation (6 ± 6.4 mmol/h) in 90% of patients while protocol B ensured appropriate acid-base balance without additional interventions: pH 7.43 (7.40-7.46), Bicarbonate 25.3 (23.8-26.6) mmol/l, BE 0.9 (-0.8 to +2.4); median (IQR). No episodes of clinically relevant metabolic alkalosis, requiring modifications of RCA-CRRT settings, were observed. Phosphate supplementation was needed in all group A patients (3.4 ± 2.4 g/day) and in only 30% of group B patients (0.5 ± 1.5 g/day). Hypophosphatemia developed in 75% and 30% of group A and group B patients, respectively. Serum phosphate was significantly higher in protocol B patients (P < 0.001) and, differently to protocol A, appeared to be steadily maintained in near normal range (0.97-1.45 mmol/l, IQR).

CONCLUSIONS

The proposed RCA-CVVHDF protocol ensured appropriate acid-base balance without additional interventions, providing prolonged filter life despite adoption of a higher target circuit-Ca(2+). The introduction of a phosphate-containing solution, in the setting of RCA, significantly reduced CRRT-related phosphate depletion.

Simplified regional citrate anticoagulation using a calcium-containing replacement solution for continuous venovenous hemofiltration

Regional citrate anticoagulation (RCA) is not widely used because it requires complex therapeutic modalities, a specialized calcium-free replacement solution, and continuous intravenous calcium infusion. We designed a simplified protocol for RCA using a commercial calcium-containing replacement solution for continuous venovenous hemofiltration (CVVH). Thirty-six patients were treated with RCA-based pre-dilution CVVH using a calcium-containing replacement solution (ionized calcium 1.50 mmol/L). We pumped a 4 % trisodium citrate solution into the arterial line of extracorporeal circulation at a starting rate of 200 mL/h while adjusting the rate to achieve a post-filter ionized calcium level of between 0.25 and 0.5 mmol/L. The initial blood flow was set at 150 mL/min. The replacement solution was delivered at 35 mL/kg/h. We measured the serum and effluent citrate concentration during CVVH at 0, 24, 48, and 72 h. The mean hemofilter survival was 61.3 ± 21.6 h (range 14-122 h). The mean 4 % trisodium citrate solution pumped was 207 (190-230) mL/h, and the mean pre-filter and post-filter ionized calcium levels were 0.96-1.02 and 0.34-0.38 mmol/L, respectively. Ninety-two, 63, and 48 % of the hemofilters were patent at 24, 48, and 72 h. The mean serum citrate concentration was not significantly different at 24, 48, and 72 h. No bleeding episodes were found, and no patient showed the symptoms and signs of hypocalcemia or citrate toxicity. Our simplified RCA protocol using a calcium-containing replacement solution for CVVH is effective and safe, and obviates the need for a separate peripheral or central venous catheter for continuous intravenous calcium infusion.

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.

Continuous venovenous hemodialysis with regional citrate anticoagulation in patients with liver failure: a prospective observational study

Introduction

Liver failure patients might be at risk for citrate accumulation during continuous venovenous hemodialysis (CVVHD) with regional citrate anticoagulation. The aim of this study was to investigate the predictive capability of baseline liver function parameters regarding citrate accumulation, expressed as an increase in the calcium total/calcium ionized (Ca_tot/Ca_ion) ratio ≥2.5, and to describe the feasibility of citrate CVVHD in liver failure patients.

Methods

We conducted a prospective observational study in medical ICU patients treated in a German university hospital. We performed 43 CVVHD runs using citrate for regional anticoagulation in 28 critically ill patients with decompensated liver cirrhosis or acute liver failure (maximum of two CVVHD runs per patient). Liver function was characterized before CVVHD using laboratory parameters, calculation of Child-Pugh and Model of End-stage Liver Disease scores, and determination of the plasma disappearance rate of indocyanine green. In addition to blood gas analysis, we measured total calcium and citrate in serum at baseline and after definitive time points for each CVVHD run.

Results

Accumulation of citrate in serum correlated with an increase in the Ca_tot/Ca_ion ratio. Although the critical upper threshold of Ca_tot/Ca_ion ratio ≥2.5 was exceeded 10 times in seven different CVVHD runs, equalization of initial metabolic acidosis was possible without major disturbances of acid-base and electrolyte status. Standard laboratory liver function parameters showed poor predictive capabilities regarding citrate accumulation in terms of an elevated Ca_tot/Ca_ion ratio ≥2.5. In contrast, serum lactate ≥3.4 mmol/l and prothrombin time ≤26% predicted an increase in the Ca_tot/Ca_ion ratio ≥2.5 with high sensitivity (86% for both lactate and prothrombin time) and specificity (86% for lactate, 92% for prothrombin time).

Conclusions

Despite substantial accumulation of citrate in serum, CVVHD with regional citrate anticoagulation seems feasible in patients with severely impaired liver function. Citrate accumulation in serum is reflected by an increase in the Ca_tot/Ca_ion ratio. To identify patients at risk for citrate accumulation in terms of a Ca_tot/Ca_ion ratio ≥2.5, baseline serum lactate (threshold ≥3.4 mmol/l) and prothrombin time (threshold ≤26%) may be useful for risk prediction in daily clinical practice. Careful monitoring of electrolytes and acid-base status is mandatory to ensure patient safety.

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.