Objective: In extracorporeal blood purification, citrate anticoagulation offers several substantial advantages over conventional heparin anticoagulation. However, there is still a lack of information on citrate kinetics, especially on the citrate clearance of conventional hemodialyzers. The aim of this study was to investigate the citrate clearance for different hemodialysis filters as a basis for the development of an intelligent citrate-calcium infusion algorithm.
Materials and methods: For our experiments, the Fresenius 4008H dialysis machine and the dialysis filters FX 60, F6 HPS, F8 HPS (Fresenius Medical Care, Bad Homburg, Germany), Polyflux 140H and 14L (Gambro Holding, Stockholm, Sweden), Xenium 130 (Baxter AG, Vienna, Austria) and APS-650 (ASAHI Kasei Kuraray Medical, Chiyoda-ku, Japan) were used. Clearance calculations were performed based on plasma/blood flow rate and the citrate concentrations at filter inlet and outlet. All experiments were carried out in vitro with fresh frozen plasma (FFP) or whole blood.
Results: The results prove that citrate clearance is significantly higher with high-flux filters than with low-flux filters. Higher dialysate flow rates cause a more effective removal of citrate. The citrate clearance for low-flux and high-flux filters was 71 ± 7 and 86 ± 1% of the urea clearance, respectively.
Conclusions: Citrate can efficiently be removed with standard hemodialysis. However, depending on the infused amounts as well as on the patient - especially in patients with impaired liver function - the use of a high-flux dialysis filter and a high dialysate flow rate should be considered to minimize the risk of citrate accumulation.