Continuous veno-venous hemofiltration using a phosphate-containing replacement fluid in the setting of regional citrate anticoagulation

Purpose The need for prolonged anticoagulation and the occurrence of hypophosphatemia are well known drawbacks of continuous renal replacement therapies (CRRT). The aim was to evaluate the effects on acid-base status and serum phosphate of a regional citrate anticoagulation (RCA) protocol for continuous veno-venous hemofiltration (CVVH) combining the use of citrate with a phosphate-containing replacement fluid. Methods In a small cohort of heart surgery patients undergoing CRRT for acute kidney injury, we adopted an RCA-CVVH protocol based on a commercially available citrate solution (18 mmol/l) combined with a recently introduced phosphate-containing replacement fluid (HCO3− 30 mmol/l, phosphate 1.2), aimed at preventing phosphate depletion. Results In 10 high bleeding-risk patients, the RCA-CVVH protocol provided an adequate circuit lifetime (46.8 ± 30.3 h) despite the adoption of a low citrate dose and a higher than usual target circuit Ca2+ (≤0.5 mmol/l). Acid-base status was adequately maintained without the need for additional interventions on RCA-CVVH parameters and without indirect sign of citrate accumulation [(pH 7.43 (7.41-7.47), bicarbonate 24.4 mmol/l (23.2-25.6), BE 0 (-1.5 to 1.1), calcium ratio 1.97 (1.82-2.01); median (IQR)]. Serum phosphate was steadily maintained in a narrow range throughout RCA-CVVH days [1.1 mmol/l (0.9-1.4)]. A low amount of phosphorus supplementation (0.9 ± 2 g/day) was required in only 30% of patients. Conclusions Although needing further evaluation, the proposed RCA-CVVH protocol ensured a safe and effective RCA without electrolyte and/or acid-base derangements. CRRT-induced hypophosphatemia was prevented in most of the patients by the adoption of a phosphate-containing replacement solution, minimizing phosphate supplementation needs.