Regional citrate anticoagulation and influence of recirculation on ionized calcium levels in the circuit

Regional citrate anticoagulation is now widely used during continuous renal replacement therapy (CRRT), and especially in patients at risk for hemorrhagic complications. A close monitoring is required to avoid citrate overload, leading to metabolic alkalosis or citrate intoxication causing metabolic acidosis. This case report describes a dysfunction of the regional citrate anticoagulation due to the development of a deep vein thrombosis close to the site of insertion of the venous CRRT catheter. The result was a local recirculation in the circuit with a local citrate overload (acidosis and non-measurable calcium). In the patient’s blood samples, the [calcium_total/Ca²⁺_systemic] ratio remained normal as a proof of local citrate accumulation without systemic effects. Initially, CRRT remained effective, but due to the progressive decrease of serum creatinine and cystatin C clearance, the site of catheter insertion was changed.