Citrate anticoagulation for postdilutional online hemodiafiltration with calcium-containing dialysate and infusate: significant clotting in the venous bubble trap.

BACKGROUND: The aim of this prospective clinical study was to assess safety and antithrombotic efficacy of a regional citrate anticoagulation protocol for postdilutional online hemodiafiltration (HDF) with calcium-containing dialysate and infusate.
METHODS: Nineteen postdilutional online HDF procedures with citrate anticoagulation were performed in 9 end-stage renal disease patients. Calcium-containing (1.25 mmol/L dialysate/infusate, 15% (0.51 mol/L) trisodium citrate and 1 mol/L calcium chloride (when necessary) were used; the blood flow was 300 ml/min. Antithrombotic effect was assessed visually after HDF at 3 points: the dialyzer, arterial bubble trap, and venous bubble trap, using a score of 5 (excellent anticoagulation) to 1 (total clotting). The study was terminated prematurely due to frequent clotting in the venous bubble trap.
RESULTS: The mean duration of HDF was 4.3 +/- 0.9 hours; infusion volume was 13 +/- 2 L. Almost half of the HDF procedures (9/19, 47%) were completed with some difficulty: in 1 case (1/19, 5%) there was total system clotting; in the other 8 cases, system clotting was threatening and dialysis was terminated prematurely, but in only 4/19 cases (21%) prior to 4-hour duration. The main point of clot formation was the venous bubble trap (score 2.6 +/- 1.0), while anticoagulation was very good at the dialyzer (4.0 +/- 1.2) and excellent at the arterial bubble trap (4.8 +/- 0.9). No side effects were noted, and metabolic consequences were moderate.
CONCLUSIONS: Regional citrate anticoagulation using calcium-containing dialysate/infusate during postdilutional online hemodiafiltration results in a high incidence of venous bubble trap clotting.