Citrate for CRRT

Q: What's the rationale behind using citrate (when heparin is not used) to avoid filter clotting in continuous renal replacement therapy (CRRT)?

Answer: Citrate combines with calcium resulting in extracorporeal chelation, which blocks calcium-dependent steps of clotting cascade. When extracorporeal blood mixes with venous blood, the ionized calcium level is restored, and systemic anticoagulation is avoided. 

Citrate is also metabolized via the liver, and chelated calcium is released back into circulation, which prevents hypocalcemia (though frequent checks are required, particularly in liver insufficiency).

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Recommended readings: 

1. Honoré PM, Rimmelé T, Joannes-Boyau O. Citrate anticoagulation for continuous renal replacement therapy. Intensive Care Med. 2024 Sep;50(9):1553-1556. doi: 10.1007/s00134-024-07531-3. Epub 2024 Jul 22. PMID: 39037609.

2. Jacobs R, Verbrugghe W, Dams K, Roelant E, Couttenye MM, Devroey D, Jorens P. Regional Citrate Anticoagulation in Continuous Renal Replacement Therapy: Is Metabolic Fear the Enemy of Logic? A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Life (Basel). 2023 May 17;13(5):1198. doi: 10.3390/life13051198. PMID: 37240843; PMCID: PMC10221969.

3. Poh CB, Tan PC, Kam JW, Siau C, Lim NL, Yeon W, Cui HH, Ding HT, Song XY, Yan P, Chea KL, Liu JS, Chionh CY. Regional Citrate Anticoagulation for Continuous Renal Replacement Therapy - A Safe and Effective Low-Dose Protocol. Nephrology (Carlton). 2020 Apr;25(4):305-313. doi: 10.1111/nep.13656. Epub 2019 Sep 16. PMID: 31469465.

4. Oudemans-van Straaten HM, Ostermann M. Bench-to-bedside review: Citrate for continuous renal replacement therapy, from science to practice. Crit Care. 2012 Dec 7;16(6):249. doi: 10.1186/cc11645. PMID: 23216871; PMCID: PMC3672558.