Ionic Homeostasis, Acid-base Balance and the Risk of Citrate Accumulation in Patients After Cardiovascular Surgery Treated With Continuous Veno-venous Haemo�ltration With Post-dilution Regional Citrate Anticoagulation

Background: Patients with known or new-onset acute renal failure after cardiovascular surgery, requiring renal replacement therapy, can bene�t from adequate non-heparin circuit anticoagulation. The idea behind not using heparin relates to the post-operative risk of bleeding. Simpli�ed regional citrate anticoagulation (RCA) protocol proposes the use of citric acid dextrose formula A (ACD-A) during post-dilutional continuous veno-venous hemo�ltration (CVVH) with standard bicarbonate buffered calcium containing replacement solution. Citrate accumulation diagnosed upon total to ionized calcium ratio (tCa/iCa) and low ionized calcium (iCa) are considered as the biggest risks related to regional citrate accumulation. Methods: This prospective observational study evaluated electrolyte and acid-base homeostasis in cardiovascular surgery patients with known chronic or new-onset acute renal failure treated with post-dilution continuous veno-venous haemo�ltration (CVVH) with a simpli�ed RCA protocol with ACD-A. In total, 50 consecutive cardiovascular surgery patients treated with CVVH with RCA were evaluated. Base excess; pH; bicarbonate, lactate, Na + , Cl - , Mg ++ , and inorganic phosphate concentrations; the total to ionized calcium ratio (tCa/iCa); and high anion gap metabolic acidosis were assessed during haemo�ltration treatment in survivors and non-survivors. Results: Thirty-three (66%) patients died. In total, 235 haemo�ltration sessions with a median circuit survival time of 57 hours (1-117) were evaluated. The therapies were very well balanced with regard to sodium and chloride homeostasis. The lactate concentration and anion gap decreased during CVVH sessions longer than 72 hours, but no inter-group difference was observed. The tCa/iCa ratio exceeded 2.5 in 11 of 246 (4.5%) readings and was signi�cantly higher in non-survivors (p=0.037). No correlation was observed between the lactate concentration before haemo�ltration and the tCa/iCa ratio during haemo�ltration. Magnesium and phosphate concentrations decreased during CVVH, additional supplementation with magnesium necessary. The magnesium concentration initial of to 1 L of normal saline, which resulted in a Ca ++ concentration of 4.6 mmol/L. We observed a low iCa plasma concentration in the �rst 10 patients, and this dose was increased to 20 mL of 10% calcium chloride. After the following 10 patients, 40 mL of 10% calcium chloride yielded a Ca ++ concentration of 18.4 mmol/L. The target calcium concentration in the plasma was increased from the initial 0.9–1.2 range to the 1.0-1.2 range. Furthermore, the original protocol was modi�ed by the additional routine infusion of at a �xed of g/hour (0.81 mmol/hour). �ltration ~ 20%. or bicarbonate haemo�ltration dose metabolic citrate dose and within hours, RCA was stopped [14]. on the Aquarius platform in cardiovascular surgery patients provides excellent sodium and chloride balance. Losses of magnesium and phosphate during CVVH therapy can the depletion of these simpli�ed RCA protocol provided insu�cient control of the acid-base balance, causing over-compensation for metabolic acidosis and leading to metabolic alkalosis. The evaluated protocol might be related to signi�cant incidences of hypocalcaemia and CA. these are higher than those associated with other RCA protocols should be clari�ed in a comparative study.