Effectiveness of Segmented Regional Citrate Anticoagulation in Paediatric Hemodialysis

Summary

This protocol describes a method to evaluate segmented versus single-segment regional citrate anticoagulation in pediatric hemodialysis, providing a standardized approach for clinical investigation.

Abstract

This study retrospectively compared the effectiveness and safety of segmented regional citrate anticoagulation (S-RCA) and single-segment RCA (SS-RCA) in pediatric hemodialysis. Fifty-two patients were divided into S-RCA (n = 26) and SS-RCA (n = 26) groups. Treatment parameters, ionized calcium, pH, bicarbonate, coagulation in the dialyzer and venous air trap, blood urea nitrogen (BUN), creatinine (Cr), electrolytes, total calcium, coagulation function, and complications were assessed. No significant differences were found in blood flow, dialysate flow, or ultrafiltration between groups. While anticoagulation efficacy in the dialyzer was similar, venous air trap anticoagulation was significantly better with S-RCA (p = 0.030). Post-dialysis, BUN and Cr levels decreased more significantly in the S-RCA group (p < 0.001). Electrolytes, total calcium, and coagulation parameters remained stable, with no severe adverse events. It was concluded that S-RCA provides superior anticoagulation efficacy and dialysis adequacy compared to SS-RCA in pediatric hemodialysis, offering an alternative anticoagulation regimen for this population.

Introduction

Hemodialysis (HD) is the removal of metabolic wastes, harmful substances, and excess water from the blood using the principles of diffusion and convection, and is one of the most commonly used renal replacement therapies for patients with end-stage renal disease, as well as for the treatment of acute kidney injury, drug or toxic poisoning¹. The effectiveness and safety of extracorporeal anticoagulation ensure safe and effective hemodialysis². The main anticoagulation methods for hemodialysis include: heparin-free, normal heparin anticoagulation, low molecular heparin anticoagulation, citrate anticoagulation, and so on. Currently, heparin anticoagulation is most commonly used in hemodialysis, but it increases the risk of bleeding and can lead to heparin-induced thrombocytopenia (HIT)³.

Regional citrate Anticoagulation (RCA) refers to the pumping of citrate in front of the dialyser, chelating the serum ionic calcium in the extracorporeal circulation, blocking the conversion of prothrombin to thrombin, to achieve the effect of anticoagulation, and at the same time, citrate can be metabolised in the body through the tricarboxylic acid cycle to physiological metabolites, with good biocompatibility⁴. RCA has a good effect of extracorporeal anticoagulation, and can avoid the occurrence of bleeding complications, but also has the advantages of improving the biocompatibility of the filtration membrane, etc., does not affect the coagulation status of the patient's body, etc., in recent years in the critical bleeding tendency of the patient, heparin or other contraindications to anticoagulants in patients has been widely used^5,6. Children's hemodialysis patients are mainly suffering from acute kidney injury, acute poisoning, and other critical illnesses, often combined with coagulation dysfunction. RCA can effectively reduce the risk of bleeding, and it is worth promoting the application of in children's hemodialysis^5,7.

RCA has obvious advantages in the application of hemodialysis in patients with critical bleeding tendency, and most of the development so far adopts a simplified way, that is, the use of calcium-containing dialysate for citrate anticoagulation, which simplifies the operation, and does not need additional calcium supplementation, but the simplified RCA method, anticoagulation effect is often not satisfactory, and often in the Venous air trap of coagulation^8,9. Traditional RCA, because the citrate root in the blood will be removed when passing through the dialyser, and at the same time the calcium ions in the calcium-containing dialysis fluid will also diffuse into the blood, increasing the calcium ion concentration in the circuit, leading to a reduction in the anticoagulation effect, and coagulation is often seen in the Venous air traps, which not only shortens the time of the patient's effective treatment, increases the cost of the treatment, but also results in a greater loss of blood¹⁰.

Based on the different infusion sites of citrate, regional citrate anticoagulation can be classified into the "single-segment" mode (SS-RCA) and the "segmented" mode (S-RCA). S-RCA has been reported in the literature to be safer and more efficacious¹¹, but there are fewer reports of clinical studies on the S-RCA technique in paediatric hemodialysis. This study was conducted to investigate the clinical application of S-RCA in pediatric hemodialysis. By comparing it with SS-RCA, we aimed to evaluate its feasibility, efficacy, and safety in this specific population. The primary objectives were to assess its impact on circuit anticoagulation, particularly in the venous air trap, and its effect on dialysis adequacy, as measured by the clearance of small molecules such as BUN and Cr. It was hypothesized that S-RCA would provide superior anticoagulation and dialysis adequacy compared to SS-RCA, thereby offering a safe and effective alternative anticoagulation strategy for children undergoing hemodialysis.

Therefore, the primary objective of this study was to evaluate the feasibility, efficacy, and safety of S-RCA compared to SS-RCA in a pediatric hemodialysis population. It was hypothesized that S-RCA would provide superior anticoagulation, particularly in the venous circuit, and achieve better dialysis adequacy without increasing the risk of adverse events, thereby offering an optimized anticoagulation strategy for children. Figure 1 illustrates a design flow chart for the study.

Protocol

This protocol for a retrospective comparative study was approved by the Ethics Committee of Guiyang Maternal and Child Health Hospital (Guiyang Children's Hospital) (Approval No.: 2022-36). The study was conducted in accordance with the principles of the Declaration of Helsinki. Signed informed consent was obtained from the legal guardians of all pediatric participants. The reagents and the equipment used are listed in the Table of Materials.

1. Patient selection and group allocation

1. Identify eligible patients
   NOTE: A retrospective review of electronic medical records was conducted for all pediatric patients who underwent hemodialysis for acute kidney injury (AKI) and end-stage renal disease (ESRD) at our institution between January 2023 and February 2025.
   1. Consider the following inclusion criteria: (1) clinical indications for hemodialysis; (2) predisposition to bleeding, but normal coagulation function; and (3) signed informed consent from a legal guardian.
   2. Consider the following exclusion criteria: severe hepatic failure, irreversible hypoxemia (PaO2 < 60 mmHg), hypotensive shock, severe acid-base balance disorders, hypernatremia, or the presence of coagulation abnormalities or active bleeding^12,13.
2. Allocate patients into study groups.
   1. Divide the 52 eligible patients into two groups based on the anticoagulation modality documented in their records: the Segmented Regional Citrate Anticoagulation (S-RCA) group (n = 26) and the Single-Segment Regional Citrate Anticoagulation (SS-RCA) group (n = 26).
      NOTE: This protocol describes a retrospective analysis. The anticoagulation modality (S-RCA or SS-RCA) was determined by the treating physician at the time of dialysis and is not assigned prospectively by the researcher.

2. Preparation for hemodialysis and anticoagulation setup

1. Prepare the hemodialysis circuit.
   1. Set up the hemodialysis machine, blood tubing set, dialyzer, and venous air trap according to the manufacturer's instructions and standard clinical protocols.
   2. Ensure all connections are secure. For all dialysis sessions, a commercially available calcium-containing dialysate with a calcium concentration of 1.5 mmol/L was used.
2. Prepare the citrate and calcium solutions.
   1. Use commercially available 4% trisodium citrate solution for anticoagulation. Have a calcium chloride or calcium gluconate solution ready for potential systemic calcium supplementation, though it is not routinely required with calcium-containing dialysate.
3. Prime the circuit.
   1. Prime the extracorporeal circuit with normal saline per standard procedure to remove air and prepare for patient connection.
4. Program the syringe pumps for citrate infusion. Load the citrate solution onto syringe pumps integrated with the dialysis machine.
   1. For the S-RCA group, program two separate syringe pumps.
      1. Pump 1 (Arterial End): Set the infusion rate (mL/h) to (0.5 – 1.0) × blood flow rate (mL/min). Connect this pump to the blood line immediately before the dialyzer inlet.
      2. Pump 2 (Venous Chamber): Set the infusion rate (mL/h) to (0.3 – 0.5) × blood flow rate (mL/min). Connect this pump to the venous air trap.
   2. For the SS-RCA group, program a single syringe pump.
      1. Set the infusion rate (mL/h) to (0.9 – 1.13) × blood flow rate (mL/min). Connect this pump to the blood line immediately before the dialyzer inlet.
         NOTE: The exact multiplier within the specified ranges is determined by the clinician based on patient characteristics and institutional protocol. Blood flow rate (BFR) is prescribed based on patient size and clinical status.

3. Conducting the hemodialysis session

1. Initiate the dialysis.
   1. Connect the patient to the primed dialysis circuit. Initiate blood pump flow gradually to the prescribed rate (typically 3–5 mL/kg/min in children). Start dialysate flow and ultrafiltration as prescribed.
2. Start the citrate infusion.
   1. Immediately initiate the pre-programmed citrate infusion(s) according to the assigned group (Step 2.4).
3. Monitor the treatment parameters.
   1. Continuously monitor and record the following parameters throughout the session:
      1. Monitor the blood flow rate (mL/min) via an ultrasonic Doppler flow meter.
      2. Record the dialysate flow rate (mL/min) from the dialysis machine's built-in flowmeter.
      3. Monitor the ultrafiltration volume (mL/kg/h) via the dialysis machine's volumetric control system.
      4. Record the citrate infusion rates (mL/h) from each pump via the pump's built-in flow sensor.
      5. Determine the transmembrane pressure (TMP) and venous pressure (VP) from the dialysis machine.
         CAUTION: A sharp, sustained rise in TMP (>250 mmHg) or VP suggests a high risk of circuit clotting. Inspect the dialyzer and venous chamber promptly if this occurs.

4. Sample collection and point-of-care testing

1. Collect blood samples at the following timepoints during a standard 4-h hemodialysis session: immediately before dialysis initiation (predialysis baseline), at 2 h of dialysis (samples from pre-filter, post-filter, and post-venous chamber lines), and immediately post-dialysis.
2. At each timepoint, draw approximately 0.5 mL of blood into a pre-heparinized blood gas syringe from the specified sampling port.
3. Analyze the sample immediately using a blood gas analyzer to measure: Ionized calcium (iCa²⁺), pH, Partial pressure of carbon dioxide (PaCO₂). Calculate the bicarbonate concentration using the Henderson-Hasselbalch equation: HCO₃⁻ = 0.03 × PaCO₂ × 10^(pH - 6.1). Record the value.

5. Assessment of circuit coagulation

1. Initiate visual monitoring of the extracorporeal circuit.
   1. Beginning immediately after the start of dialysis and continuing throughout the 4-h session, perform regular visual inspections of the dialyzer and venous air trap.
2. Visually inspect the dialyzer.
   1. Every 30–60 min, visually inspect the dialyzer fiber bundle against a white light background.
   2. Look for signs of coagulation, such as darkening of fiber color, streaky clots, or a general "frosting" appearance. Record any clotting event.
3. Visually inspect the venous air trap.
   1. Every 30–60 min, inspect the venous air trap for clot formation on the walls or for thickening of the blood-air interface foam layer. Record any clotting event.
4. Classify anticoagulation efficacy.
   1. At the end of the dialysis session, classify the circuit components:
      1. Classify the anticoagulation efficacy for the dialyzer and venous chamber at the end of each session as 'Effective' (no significant clotting, minimal fiber streaking, or a small clot in the venous chamber that did not require circuit intervention) or 'Ineffective' (clotting that led to a visible loss of >1 cm of fibers in the dialyzer, a large clot in the venous chamber requiring chamber change, or premature termination of the dialysis session due to circuit clotting).
      2. Calculate the effective rate as: (Number of effective cases / Total number of cases) × 100%.

6. Collection and processing of serum samples

1. At the predialysis and post-dialysis timepoints, draw 3–5 mL of venous blood into a serum separator tube. Gently invert the tube 5–8 times immediately after collection. Let the tube stand upright at room temperature for 30 min to allow complete clot formation.
2. Centrifuge the sample at 1500 × g for 10 min at 4 °C. Carefully aspirate the clear supernatant serum using a pipette, avoiding the buffy coat or red blood cells. Transfer the serum to pre-labeled cryovials.
   NOTE: The experiment can be paused here. Store serum aliquots at -80 °C for batch analysis.

7. Biochemical and coagulation analysis

1. Analyze for dialysis adequacy markers.
   1. Thaw frozen serum samples on ice. Use a fully automated biochemistry analyzer to measure: Blood Urea Nitrogen (BUN), Creatinine (Cr).
2. Analyze serum electrolytes and total calcium.
   1. Using the same or a separate serum aliquot, employ a fully automated biochemistry analyzer with ion-selective electrodes to measure: Potassium (K⁺), Sodium (Na⁺), Chloride (Cl⁻), Total Calcium (tCa²⁺) via a colorimetric method (e.g., arsenazo III).
3. Analyze coagulation function.
   1. Collect plasma samples. At predialysis and post-dialysis, draw 2 mL of venous blood into a 3.2% sodium citrate anticoagulation tube. Centrifuge at 2500 × g for 15 min at 4 °C to obtain platelet-poor plasma.
   2. Perform coagulation assays. Use a fully automated coagulation analyzer to measure: Activated Partial Thromboplastin Time (APTT), Prothrombin Time (PT), Thrombin Time (TT).

8. Monitoring and recording complications

1. Monitor for clinical symptoms.
   1. Throughout the dialysis session and in the immediate recovery period, ask the patient and observe for symptoms.
   2. Record the occurrence of: Numbness of lips/mouth or extremities, Muscle cramps, Nausea or vomiting.
2. Monitor hemodynamics.
   1. Measure and record blood pressure every 15–30 min. Document episodes of hypotension, defined as a drop in systolic blood pressure >20 mmHg from baseline or an absolute value <90 mmHg.
3. Assess for citrate accumulation.
   1. Using the measured post-dialysis tCa²⁺ (from Step 7.2) and iCa²⁺ (from Step 4.2) values, calculate the tCa²⁺ / iCa²⁺ ratio. A ratio > 2.5 suggests possible citrate accumulation¹⁴.

9. Data management and statistical analysis

1. Organize the data.
   1. Compile all recorded and measured data into a structured electronic database. Ensure patient identifiers are removed or coded for confidentiality.
2. Perform statistical analysis.
   1. Use statistical software (e.g., SPSS 26.0) for analysis. Test for normality. Perform normality tests (e.g., Shapiro-Wilk) on all continuous data. Compare continuous variables.
   2. Express normally distributed data as mean ± standard deviation (x̄ ± s). Use independent samples t-tests to compare parameters (e.g., iCa²⁺, BUN, Cr) between the S-RCA and SS-RCA groups at different timepoints. Use paired t-tests for within-group comparisons (pre vs. post-dialysis). Compare categorical variables.
   3. Express count data (e.g., anticoagulation efficacy, complication rates) as number (percentage). Use the Chi-squared (χ²) test to compare these variables between the two groups. Set significance level. Consider a P-value of < 0.05 as statistically significant for all tests.

Results

A total of 52 pediatric patients meeting the inclusion criteria were enrolled and divided into the S-RCA (n=26) and SS-RCA (n=26) groups. Baseline demographic and clinical characteristics were comparable between groups (P>0.05), as shown in Table 1.

As shown in Table 2, the total citrate dose was significantly higher in the S-RCA group than in the SS-RCA group (P<0.001), reflecting the additional venous chamber infusion in the S-RCA protocol. Arterial-en...

Discussion

The management of anticoagulation in paediatric hemodialysis has always been a major challenge in clinical practice. Due to the slender vasculature, small blood volume, and significant differences in metabolic characteristics between paediatric patients and adults, traditional systemic anticoagulation (e.g., heparin) is prone to hemorrhagic or thrombotic complications, with a higher risk, especially in children with a bleeding tendency, during the perioperative period, or with low body weight¹⁵

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Blood Gas Analyzer	Werfen	GEM Premier 5000	Used for measuring iCa2+, pH, PaCO2, and calculating HCO3-.
Ultrasonic Doppler Blood Flow Meter	Transonic Systems Inc.	HD02	On-line monitoring of blood flow rate during dialysis.
Fully Automated Biochemistry Analyzer	Roche Diagnostics	Cobas 8000	Used for measuring BUN, Cr, electrolytes (K+, Na+, Cl-), tCa2+, and albumin.
Fully Automated Coagulation Analyzer	Sysmex Corporation	CS-5100	Used for measuring APTT, PT, and TT.
Dialysis Machine (built-in syringe pump with flow sensor)	Gambro	AK 96	Built-in flow sensor with accuracy ±0.5 mL/h for citrate infusion; volumetric ultrafiltration control system for monitoring ultrafiltration volume.
Sodium Citrate Anticoagulation Tubes	BD Vacutainer	363083	2.7 mL tubes (3.2% sodium citrate) for coagulation tests.
Blood Pressure Monitor	GE Healthcare	Carescape V100	Non-invasive blood pressure monitoring during dialysis.
Dialyzer	Fresenius Medical Care	FX Paed	Low-volume, high-efficiency dialyzer designed for pediatric use.
Venous Air Trap / Chamber	Fresenius Medical Care	Integral venous chamber	Part of the extracorporeal circuit, regularly checked for coagulation.
Calcium-containing Dialysate	Fresenius Medical Care	GranuPac	Standard bicarbonate dialysate with calcium concentration of 1.25 or 1.5 mmol/L.
Citrate Solution	Baxter	4% trisodium citrate (46.7 mmol/L)	Used for regional citrate anticoagulation in SS-RCA and S-RCA modes.
Syringe Pump for Citrate Infusion	B. Braun	Perfusor Space	Programmable syringe pump used for precise citrate infusion at arterial and venous sites.
Continuous Venous Pressure Monitor	Gambro	AK 96	Monitors venous pressure (VP) to assess circuit patency and coagulation risk.
Transmembrane Pressure Monitor	Gambro	AK 96	Monitors TMP to detect dialyzer clotting.
Statistical Software	IBM	SPSS 26.0	Used for data analysis and statistical comparisons.