Free ionized calcium and other divalent cations (iCa)

Free ionized calcium (iCa) and other divalent cations, such as magnesium (Mg2+), are essential inorganic ions in the blood and dialysis fluid that serve as critical cofactors for physiological processes, including the blood coagulation cascade and neuromuscular signaling (NIH, 2023). In the context of extracorporeal therapies like hemodialysis or continuous renal replacement therapy (CRRT), these ions are the primary targets for regional anticoagulation using citrate (StatPearls, 2023). Citrate acts by chelating free ionized calcium, reducing its concentration below the levels required for the activation of calcium-dependent clotting factors, thereby preventing thrombus formation within the dialysis circuit (CJASN, 2016). Beyond coagulation, these cations are vital for maintaining cardiac rhythm and bone density, and their levels are strictly regulated by the parathyroid-kidney-bone axis (PubMed, 2015). Monitoring ionized calcium is a standard biomarker for assessing the efficacy and safety of these interventions, particularly to avoid complications like citrate toxicity or severe hypocalcemia (StatPearls, 2023).

Other names

Ionized calciumCa2+Divalent cationsMagnesium ionsMg2+Serum ionized calcium

Chelation of divalent cations to inhibit calcium-dependent enzymatic steps in the coagulation cascade (StatPearls, 2023).