Magnesium Kinetics During Citrate-Anticoagulated CRRT

Total and Ionized Magnesium Kinetics During Citrate-Anticoagulated Continuous Renal Replacement Therapy

The goal of this observational study is to assess how continuous renal replacement therapy (CRRT), a type of dialysis used in critically ill patients, affects magnesium levels in adults treated in intensive care units (ICUs). The study focuses on CRRT using citrate, a substance that prevents blood clotting in the dialysis circuit. Participants will receive CRRT with citrate as part of their routine medical care.

The main questions it aims to answer are:

How does citrate affect the amount of free (ionized) magnesium in the blood How much magnesium is removed by the dialysis circuit during treatment? How do magnesium levels in the blood change over time during treatment? How does treatment affect calcium and phosphate levels and what changes occur in the body's acid-base balance and metabolism?

Researchers will:

Measure magnesium, calcium and phosphate levels in blood and dialysis circuit fluid samples collected before and during treatment, for up to 72 hours.

Measure additional blood markers to assess changes in metabolism and acid-base balance.

Record dialysis treatment settings and fluid flow rates.

The collected measurements will be used to better understand how magnesium and other electrolytes are affected during CRRT with citrate.

Study Overview

• Status: Not yet recruiting
• Conditions: Magnesium; Continuous Renal Replacement Therapy (CRRT)
• Intervention / Treatment: Other: Serial blood and dialysis circuit fluid sampling

Detailed Description

Regional citrate anticoagulation (RCA) is frequently used during continuous renal replacement therapy (CRRT) to prevent blood clotting within the extracorporeal circuit. Citrate works by binding ionized calcium, thereby inhibiting the coagulation cascade. However, citrate also binds ionized magnesium, which may affect magnesium levels and contribute to magnesium losses during treatment. Previous studies have reported magnesium losses during CRRT with RCA but most have focused on total magnesium concentrations. The effects of citrate on ionized magnesium, the biologically active fraction of magnesium, remain less well understood.

The primary objective of this prospective observational study is to characterize magnesium kinetics during CRRT with RCA by repeated measurements of both total and ionized magnesium concentrations in the patient's blood and at different locations within the extracorporeal circuit. The study will investigate citrate-associated magnesium binding, magnesium transport across the dialysis filter, magnesium mass balance within the circuit and changes in systemic magnesium concentrations over time.

Secondary objectives are to characterize calcium and phosphate kinetics during treatment and to explore associated changes in acid-base balance and metabolic parameters.

Approximately 35 adult patients receiving CRRT with RCA as part of routine clinical care at three intensive care units (ICUs), one in Sweden and two in Iceland. Eligible patients will be those receiving continuous veno-venous hemodiafiltration (CVVHDF) using the PrisMax system and an ST150 hemofilter. All treatment decisions, including citrate administration, dialysis settings, and fluid management, will follow routine clinical practice and will not be altered by the study. Study-specific sampling will continue for up to 72 hours or until the ongoing CRRT circuit is discontinued, whichever occurs first.

Blood samples will be collected before treatment initiation and at 2, 6, 12, 18, 24, 48, and 72 hours after treatment begins. Systemic blood samples will be obtained from the patient's arterial line, while additional samples will be collected from the pre-filter and post-filter blood sampling ports and from the effluent fluid of the extracorporeal circuit. Total and ionized magnesium and calcium concentrations, as well as phosphate concentrations, will be measured to assess changes over time and calculate electrolyte transport and balance within the circuit. Additional systemic blood measurements will be performed before treatment and at 24, 48, and 72 hours to assess metabolic and acid-base responses. Dialysis treatment parameters, such as blood flow, citrate dose, treatment fluid flow rates and fluid removal, will also be recorded.

By combining repeated measurements of total and ionized magnesium with measurements across the extracorporeal circuit, this study aims to improve understanding of magnesium handling during CRRT with RCA. The findings may help determine whether monitoring total magnesium alone adequately reflects changes in ionized magnesium and provide further insight into electrolyte and metabolic changes during treatment.

• Study Type: Observational
• Enrollment (Estimated): 35

Contacts and Locations

• Study Contact: Name: Marcus Ewert Broman; Phone Number: +46 70 289 84 25; Email: marcus.broman@med.lu.se
• Study Contact Backup: Name: Eyrun Arna Kristinsdottir; Phone Number: +46 76 560 88 01; Email: eyrun.kristinsdottir@skane.se

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

The study population will consist of adult patients (≥18 years) admitted to the intensive care units (ICUs) at Skåne University Hospital in Sweden and Landspitali University Hospital in Iceland, for whom a clinical decision has been made to initiate continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA). Eligible patients will be those scheduled to receive continuous veno-venous hemodiafiltration (CVVHDF) using the PrisMax system and an ST150 hemofilter as part of routine clinical care.

Description

Inclusion Criteria:

• Age ≥18 years.
• Clinical decision to initiate continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA).
• Planned treatment with continuous veno-venous hemodiafiltration (CVVHDF) using the PrisMax system and an ST150 hemofilter.
• Informed consent obtained in accordance with the approved study procedures.

Exclusion Criteria:

- None beyond failure to meet the inclusion criteria.

Study Plan

How is the study designed?

Design Details

• Observational Models: COHORT
• Time Perspectives: PROSPECTIVE

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in systemic total magnesium concentration	Changes in systemic total magnesium concentration (mmol/L), measured using conventional clinical laboratory methods, will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.
Changes in systemic ionized magnesium concentration	Changes in systemic ionized magnesium concentration (mmol/L), measured using ion-selective electrode technology, will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.
Citrate-associated changes in magnesium ionization	Changes in the ionized magnesium fraction (ionized magnesium/total magnesium) between systemic and pre-filter blood will be assessed following administration of citrate-containing predilution fluid, accounting for dilution. Ionized magnesium will be measured using ion-selective electrode technology and total magnesium using conventional clinical laboratory methods.	At 2, 6, 12, 18, 24, 48, and 72 hours after CRRT initiation.
Magnesium flux across the extracorporeal filter	Magnesium flux across the extracorporeal filter (mmol/h) will be calculated using total and ionized magnesium concentrations in pre-filter and post-filter blood and effluent fluid, accounting for blood flow rates, treatment fluid flow rates and fluid composition. Ionized magnesium will be measured using ion-selective electrode technology and total magnesium using conventional clinical laboratory methods.	At 2, 6, 12, 18, 24, 48, and 72 hours after CRRT initiation.
Net magnesium loss attributable to CRRT	Net magnesium loss attributable to CRRT (mmol/h) will be calculated from magnesium removal in the effluent, accounting for magnesium supplied through dialysate and post-filter replacement fluids. Calculations will use the actual treatment fluid composition and flow rates at each sampling time. Ionized magnesium will be measured using ion-selective electrode technology and total magnesium using conventional clinical laboratory methods.	At 2, 6, 12, 18, 24, 48, and 72 hours after CRRT initiation.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in systemic total calcium concentration	Changes in systemic total calcium concentration (mmol/L), measured using conventional clinical laboratory methods, will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.
Changes in systemic ionized calcium concentration	Changes in systemic ionized calcium concentration (mmol/L), measured using ion-selective electrode technology, will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.
Calcium flux across the extracorporeal filter	Calcium flux across the extracorporeal filter (mmol/h) will be calculated using total and ionized calcium concentrations in pre-filter and post-filter blood and effluent fluid, accounting for blood flow rates, treatment fluid flow rates and fluid composition. Ionized calcium will be measured using ion-selective electrode technology and total calcium using conventional clinical laboratory methods.	At 2, 6, 12, 18, 24, 48, and 72 hours after CRRT initiation.
Net calcium loss attributable to CRRT	Net calcium loss attributable to CRRT (mmol/h) will be calculated from calcium removal in the effluent, accounting for calcium supplied through dialysate and post-filter replacement fluids. Calculations will use the actual treatment fluid composition and flow rates at each sampling time. Ionized calcium will be measured using ion-selective electrode technology and total calcium using conventional clinical laboratory methods.	At 2, 6, 12, 18, 24, 48, and 72 hours after CRRT initiation.
Changes in systemic phosphate concentration	Changes in systemic phosphate concentration (mmol/L), measured using conventional clinical laboratory methods, will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.
Phosphate flux across the extracorporeal filter	Net phosphate flux across the extracorporeal filter (mmol/h) will be calculated using phosphate concentrations measured by conventional clinical laboratory methods in pre-filter and post-filter blood and effluent fluid, accounting for blood and treatment fluid flow rates and fluid composition.	At 2, 6, 12, 18, 24, 48, and 72 hours after CRRT initiation.
Net phosphate loss attributable to CRRT	Net phosphate loss attributable to CRRT (mmol/h) will be calculated using phosphate concentrations measured in effluent fluid by conventional clinical laboratory methods, accounting for phosphate supplied through dialysate and replacement fluids. Calculations will use the actual treatment fluid composition and flow rates at each sampling time.	At 2, 6, 12, 18, 24, 48, and 72 hours after CRRT initiation.
Changes in systemic blood pH during RCA-CRRT	Changes in systemic arterial blood pH will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation, using arterial blood gas analysis.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.
Changes in systemic bicarbonate concentration during RCA-CRRT	Changes in systemic bicarbonate concentration (mmol/L) will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation, using arterial blood gas analysis.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.
Changes in systemic base excess during RCA-CRRT	Changes in systemic base excess (mmol/L) will be assessed from baseline and over time during continuous renal replacement therapy with regional citrate anticoagulation, using arterial blood gas analysis.	Before CRRT initiation (baseline) and at 2, 6, 12, 18, 24, 48, and 72 hours after initiation.

Collaborators and Investigators

• Sponsor: Region Skane
• Collaborators: Nova Biomedical; Vantive Health LLC
• Investigators: Principal Investigator: Marcus Ewert Broman, Skåne University Hospital, Lund University

Study record dates

Study Major Dates

• Study Start (Estimated): November 1, 2026
• Primary Completion (Estimated): October 1, 2027
• Study Completion (Estimated): January 1, 2028

Study Registration Dates

• First Submitted: October 23, 2026
• First Submitted That Met QC Criteria: October 23, 2026
• First Posted (Actual): October 30, 2026

Study Record Updates

• Last Update Posted (Actual): November 12, 2026
• Last Update Submitted That Met QC Criteria: November 6, 2026
• Last Verified: November 1, 2026

More Information

Terms related to this study

• Keywords: Magnesium; Continuous Renal Replacement Therapy; Ionized Magnesium; Regional Citrate Anticoagulation; Magnesium kinetics
• Other Study ID Numbers: Dnr 2025-08131-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No