33 Citrate Anticoagulation during Plasma Exchange in Patients with Thrombotic Thrombocytopenic Purpura – Short Heparin‐Free Hemodialysis Helps to Remove Citrate Load

Abstract

Background Treatment of thrombotic thrombocytopenic purpura (TTP) requires daily or even twice daily plasma exchanges (PE) with fresh frozen plasma as a replacement solution. If citrate anticoagulation is needed, citrate load (both from fresh frozen plasma and citrate as an anticoagulant) can be significant, causing severe alkalosis. Citrate as a small molecule is easily dialyzable, so short heparin‐free hemodialyses performed periodically after or between PE procedures can help to remove citrate load. The aim of our report is to present our experience with citrate anticoagulation in patients with TTP treated with daily PEs.Methods Fifteen protocols of plasma exchange procedures performed in a 46‐year‐old female with TTP were analyzed. Blood flow in all procedures was 100 mL/min, 4% trisodium citrate was used as anticoagulant, infused into the arterial line at rate 130 mL/h. 1 m CaCl2 was infused into the venous line in a dose adjusted to maintain ionized calcium (iCa) within normal limits (mean dose of 11.5 ± 1.5 mL/h). Fresh frozen plasma was used as a replacement solution, 3258 ± 548 mL per procedure.Results Ionized calcium before PE ranged from 1.10–1.45 mmol/L (mean 1.27 ± 0.12). The initial iCa level gradually increased after several procedures, as a consequence of citrate‐calcium complex metabolism between the procedures. Levels of iCa during PE were: 1.15 ± 0.09 mmol/L after 1 hour, 1.18 ± 0.06 after 2 hours and 1.16 ± 0.09 after 3 hours. Significant alkalosis occurred after several PEs with plasma pH 7.51 and bicarbonate 40.7 mmol/L. It was corrected by a 2‐hour heparin‐free hemodialysis with dialysate: K 4.0 mmol/L, calcium 1.5 mmol/L, sodium 140 mmol/L and bicarbonate set to 24 mmol/L. After dialysis pH was 7.38 and bicarbonate 28.5 mmol/L. Such hemodialysis was repeated during PE treatment.Conclusion Citrate anticoagulation can be safely performed in patients treated with PE by daily plasma exchanges. Periodically performed short heparin‐free hemodialysis can remove excess citrate and help to correct and avoid severe metabolic alkalosis.