HEmoFiltration With Citric Acid Anticoagulation

All consecutive cardio-vascular surgery patients treated with post-dilution hemofiltration with regional citrate anticoagulation (HF RCA) from August 2015 through November 2017 were included to prospective audit. Indication to hemofiltration treatment was based on clinical assessment of patients renal function and clinical status by attending physician and conformed conventional indications to renal replacement therapy (RRT) in intensive care unit (ICU). Severe chronic liver disease or acute liver injury with INR \> 2 and refractory shock with lactate increasing above 8 mmol/L were considered as contraindication to RCA. Initially set blood flow was 5 times higher than filtrate flow, which makes filtration fraction of 20%. To reduce the risk of metabolic alkalosis, ACD-A citrate solution was proposed instead of most commonly used trisodium citrate solution, and relatively low target citrate concentration (2.8 mmol/L) was adopted. In case of pH increase above 7.5 or bicarbonate concentration above 40 mmol/L filtrate flow was decreased from initial 35 ml/kg/hour down to 25 ml/kg/hour which should reduce bicarbonate synthesis by 25%. If metabolic alkalosis persisted, the second step involved reduction of blood flow from initial 5 times down to 4 times filtrate flow, which reduced citrate flow by the same factor. In order to avoid hypomagnesemia resulting from magnesium binding to citrate, and its removal with ultrafiltrate not balanced with magnesium content in replacement fluid, the original protocol was modified by connecting magnesium sulfate solution 2g/50 ml 0.9% NaCl at the flow 1 mL/hour. All sessions stopped due to patients death before 48 hours of HF treatment were excluded from the analysis. Similarly, all cases where hemofiltration session was stopped before 48 hours of treatment due to organizational reasons, recovery of renal function, change of therapy, and when patients were treated with heparin infusion due to surgical indications were excluded from further circuit survival analysis. Blood gas parameters together with pH, bicarbonate concentration, Na, Cl, K, Ca, hemoglobin concentration, hematocrit, lactate, and anion gap were analyzed every 6 hours. Post filter ionized calcium concentration was not assessed. Serum phosphate, magnesium and total calcium was assessed every 24 hours during hemofiltration treatment with RCA.