Evaluation of Filters Useful Life, Metabolic Control, Electrolyte Profile and Acid-base Balance During Regional Anticoagulation With 4% Trisodium Citrate in Patients Undergoing CVVHDF: Effects of Increased Blood Flow

Acute kidney injury (AKI) is a clinical syndrome with a high incidence and prevalence in Intensive care units (ICU). It is estimated that 50% of ICU patients have AKI at some point.

About 10-15% of these individuals require renal replacement therapy (RRT). Although studies have not conclusively shown the superiority of continuous methods, the most severe patients are usually referred for this type of therapy.

The main indications for continuous therapies are hemodynamic instability, cardiogenic shock, severe respiratory insufficiency, risk situations for brain edema, hypercatabolism, need for strict volume control, acute liver disease and major sodium disturbances. One of the main disadvantages of continuous therapies is the necessity of anticoagulation. Critically ill patients have a pro-clotting state (inflammation) and several risk factors for bleeding (coagulopathies, postoperative, large vessel puncture). On the one hand, the lack or ineffective anticoagulation compromises the efficiency of the procedure, shortens the life of the extracorporeal system, consumes resources and increases blood loss due to unexpected and early filter coagulation. On the other hand, excessive use of anticoagulants, especially heparin, is associated with bleeding and increased transfusions.

In this scenario, regional anticoagulation with citrate (RCA) has become the method of choice in the different modalities of continuous dialysis. When compared to heparin, the use of regional citrate anticoagulation is associated with less bleeding and transfusion need and longer life of the extracorporeal system. It also seems to decrease endothelial activation, neutrophil degranulation and activation of the complement system.

The anticoagulate property of citrate is based on its binding to calcium (Ca). Citrate quenches Ca in the extracorporeal system, an essential cofactor in several steps of coagulation. Optimal anticoagulation is achieved when ionic Ca concentration in the extracorporeal circuit is maintained between 0.25 and 0.35 mmol/L. This is usually achieved with a citrate level in the circuit around 4mmol/L of blood. Depending on the modality chosen and other factors, up to 60% of the citrate-Ca complex is eliminated during passage through the filter (molecular weigh of 298 Daltons and partition coefficient of 1.0). The rest is metabolized in the Krebs cycle mainly in the liver, kidneys and skeletal muscles. Each mol of trisodium citrate causes 3 moles of bicarbonate thus correctly, partially or completely, the metabolic acidosis resulting from renal failure. Ca and sodium (Na) are released into the systemic circulation. Trisodium citrate also increases the strong ion difference due to the high sodium concentration in the solution, thus increasing the buffering capacity. In parallel it is necessary the Ca replacement to maintain normal calcemia. The citrate also quenches magnesium, which can lead to a disturbance of this electrolyte.