INTRODUCTION. Regional citrate anticoagulation (RCA) is now considered the preferred anticoagulation protocol in high bleeding risk patients and different combination of citrate and CRRT solutions can affect acid-base balance. Regardless of the anticoagulation protocol, hypophosphatemia occurs frequently in CRRT. In this case report, we evaluated safety and effects on acid-base status of a new RCA-CVVH protocol using a 18 mmol/L citrate solution combined with a phosphate-containing replacement fluid, compared with a 12 mmol/L RCA-CVVH protocol with conventional replacement solution.

METHODS. Until september 2011, RCA-CVVH was routinely performed in our center with a 12 mmol/L citrate solution (Prismocitrate 10/2) and a post-dilution replacement fluid with bicarbonate (Prismasol 2; HCO3- 32, Ca++ 1.75, Mg++ 0.5, K+ 2 mmol/L) (protocol A). In case of persistent acidosis, not related to citrate accumulation, bicarbonate infusion was scheduled. In order to optimize buffers balance, a new RCA-CVVH protocol has been designed using recently introduced solutions: 18 mmol/L citrate solution (Prismocitrate 18), phosphate-containing post-dilution replacement fluid with bicarbonate (Phoxilium; HCO3- 30, Phoshate 1.2, Ca++ 1.25, Mg++ 0.6, K+ 4 mmol/L) (protocol B).

RESULTS. In a cardiac surgery patient with AKI, acid-base status and electrolytes have been evaluated comparing protocol A (5 circuits, 301 hours) vs protocol B (2 circuits, 97 hours): pH 7.39±0.03 vs 7.44±0.03 (p<0.0001), bicarbonate 22.3±1.8 vs 22.6±1.4 mmol/L (NS), BE -2.8±2.1 vs -1.6±1.2 (p=0.007), phosphate 0.85±0.2 vs 1.3±0.5 mmol/L (p=0.027). Protocol A required bicarbonate and sodium phosphate infusion (8.9±2.8 mmol/h and 5g/day, respectively) while protocol B allowed to stop both supplementations. Furthermore, the need for KCl infusion was significantly lower with protocol B (4±0.2 vs 1.4±1.5 mmol/h; p<0.0001).

CONCLUSIONS. In this preliminary, single patient report, protocol B provided a buffers balance more positive than protocol A and allowed to adequately control acid-base status without additional bicarbonate infusion and in absence of alkalosis, despite the use of a standard bicarbonate concentration replacement solution. Furthermore, the combination of a phosphate-containing replacement fluid appeared effective to prevent hypophosphatemia.