Magnesium Balance of Citrate-based Continuous Venovenous Hemofiltration, Effect of Citrate Dose.

Rationale: A higher citrate dose during continuous venovenous hemofiltration provides better anticoagulation but possibly a higher risk of citrate accumulation in case of metabolic limitations. A higher citrate dose also increases magnesium loss in ultrafiltrate, while a negative magnesium balance is unwanted. Objective: Aim of this study is to determine the magnesium balance of citrate-based continuous veno-venous hemofiltration (CVVH) and to determine whether and to which extent the magnesium balance depends on citrate dose. Study design and methods: A prospective randomized study conducted in critically ill patients with acute kidney injury (AKI), treated with CVVH, with either low dose citrate (2.5 mmol/L blood flow in the filter) or high dose citrate (4.5 mmol/L blood flow in the filter) as anti-coagulant, targeting a postfilter ionized Calcium (iCa) of resp. 1.3-1.6 mg/dL (0.325-0.4 mmol/L) and 0.8-1.1 mg/dL (0.2-0.275 mmol/L). Post-filter blood as well as effluent aliquots and bloodconcentrations in the patient are tested for the following variables: (0 , 2 , 4, 6, 12 and 24 hrs): Total Magnesium (tMg) and total Calcium (tCa), ionized Ca (iCa)(bloodgas analyzer). In addition, hematocrit, albumin, total protein, ureum and creatinine and parathormone (PTH) are determined in arterial blood at 0 and 24 hrs or at the time of protocol exit and citrate concentrations in postfilter and arterial blood at 1 and 24 hrs or at protocol exit. Sample sites: arterial line, postfilter port (after postdilution and calcium compensation), effluent sample. All flow rates to be noted. Study population: Twenty patients admitted to intensive care, requiring continuous renal replacement therapy (CRRT) for AKI. Intervention: Anti-coagulation with either low dose citraat (2.5 mmol/L blood flow) or high dose citraat (4.5 mmol/L blood flow) targeting postfilter iCa of resp. 1.3-1.6 and 0.8-1.1 mg/dL. Both regimens are within standard protocolled CVVH treatment in the intensive care department.

Blood flow according to weight.Target citrate concentration is 4,5 mmol/L blood flow delivered as prismocitrate 18/0 pre-filter. After correction for filtration fraction, the required further amount of substitution fluid is given post filter to achieve a hemofiltration rate of 30 ml/kg/hr. Blood citrate concentrations are tailored to achieve an iCa of 0.8-1.1 mg/dL.

Blood flow according to weight. Target citrate concentration is 2.5 mmol/L blood flow delivered as prismocitrate 18/0 pre-filter. After correction for filtration fraction, the required further amount of substitution fluid is given post filter to achieve a hemofiltration rate of 30 ml/kg/hr. Blood citrate concentrations are tailored to achieve an iCa of 1.3-1.6 mg/dL.

Inclusion Criteria: Critically ill patients requiring CRRT for AKI (RIFLE criteria) Written informed consent from the patient or legal representative Exclusion Criteria: pre-existing chronic renal insufficiency requiring dialysis chronic immunosuppression liver cirrhosis Child-Pugh C severe or shock-related hepatitis Pregnancy

Boer W, Fivez T, Vander Laenen M, Bruckers L, Gron HJ, Schetz M, Oudemans-van Straaten H. Citrate dose for continuous hemofiltration: effect on calcium and magnesium balance, parathormone and vitamin D status, a randomized controlled trial. BMC Nephrol. 2021 Dec 11;22(1):409. doi: 10.1186/s12882-021-02598-2.

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