Regional Citrate Anticoagulation for Hemodialysis: Calcium-Free Vs. Calcium Containing Dialysate - A Randomized Trial

BACKGROUND: The majority of citrate protocols for hemodialysis (HD) use calcium (Ca)-free dialysate, a limited number use dialysate with Ca, aiming to simplify the procedure. This randomized clinical study sought to compare the anticoagulant effect of citrate using Ca-free dialysate and dialysate with Ca 1.25 mmol/L. METHODS: Fifty HD procedures (in 5 chronic HD patients treated by chronic citrate anticoagulation) were randomly assigned to Ca-free dialysate (25 procedures) or Ca-1.25 dialysate (25 procedures), both with Mg 0.5 mmol/L, Na 138 mmol/L, and bicarbonate 28 mmol/L. Ca-free HD: 15% Na3 citrate 80 ml/hour was infused into the arterial line, and 1 M CaCl2, 14 ml/hour into the venous line. Ca-1.25 group: 15% Na3 citrate 100 ml/hour, 1 M CaCl2 2-4 ml/hour. Polyflux H dialyzers were used. Antithrombotic effect was assessed visually after HD at 3 points: dialyzer, arterial, and venous bubble traps, using a score of 5 (no clotting) to 1 (total clotting). RESULTS: Ca-free group: arterial bubble trap score 4.7 +/- 0.5, dialyzer 4.5 +/- 0.6, venous bubble trap 4.8 +/- 0.6. Ionized calcium (iCa) at dialyzer inlet 0.34 +/- 0.17, outlet 0.21 +/- 0.06 mmol/L. All HDs were completed successfully. Ca-1.25 group: arterial bubble trap score 4.7 +/- 0.5 (NS), dialyzer 2.6 +/- 1.04 (p<0.01), venous bubble trap 2.4 +/- 0.9 (p<0.01). Volume of clot in venous bubble trap was 1.9 +/- 1.8 mL (range 0.5-6 mL). iCa at dialyzer inlet 0.24 +/- 0.05 mmol/L (p<0.05), outlet 0.63 +/- 0.11 mmol/L (p<0.01). Four of 25 HD procedures (16%) were prematurely terminated due to threatening dialyzer clotting, in 6/25 HD procedures (24%), the venous line was changed (p<0.01). CONCLUSION: Citrate anticoagulation with Ca-1.25 dialysate resulted in significantly worse anticoagulation of dialyzer and venous bubble trap compared with Ca-free dialysate, despite higher citrate dose.