A mathematical estimation for quantified calcium supplementation during intermittent hemodialysis using regional citrate anticoagulation

Background Regional citrate anticoagulation has been recommended as an alternative of anticoagulation for patients at high risk of bleeding undergoing intermittent hemodialysis. Precise calcium supplementation is important for the safety of regional citrate anticoagulation. In this study, we aimed to develop a possible method to optimize calcium supplementation for regional citrate anticoagulation in intermittent hemodialysis. Methods The investigation consisted of a pilot study and a validation study. 18 patients undergoing intermittent hemodialysis anticoagulated by citrate, and six types of filters were included in the pilot study. The ionized calcium levels were monitored and maintained in the targeted range. Calcium-free dialysate was used in the study. After linear regression analysis of the clearance of non-protein bound calcium and calculating the ratio of the non-protein bound calcium concentration to total calcium concentration, we developed a mathematical model for estimation of extracorporeal circuit calcium removal. Another 8 maintenance hemodialysis patients (12 sessions) were enrolled in the validation study to validate the new version of the calcium supplementation approach. Results In the pilot study, positive correlations were found between the clearance of non-protein bound calcium and the hematocrit-adjusted clearance of creatinine and phosphate given in the dialyzer leaflet (R-2 = 0.31, p = 0.0165). The ratio of the non-protein bound calcium concentration to total calcium concentration at the pre-filter point after infusion of citrate were constant about 0.75. In the validation study, we found that the systemic ionized calcium levels were stably maintained in the safe range and no filter clotting occurred during the hemodialysis when we used the new model of calcium supplementation. Conclusions We developed a possible method to quantify calcium supplementation for intermittent hemodialysis anticoagulated by citrate which may help to avoid negative calcium balance and reduce the incidence of complications.