Preliminary results of dialysis study: accuracy of a single pool variable-volume calcium kinetic model with different calcium dialysate concentrations

Background: The primary aim of the international study DialysIS (Dialysis therapy between Italy and Switzerland) is the increased personalization of hemodialytic treatments through a modellistic approach. Within the DialysIS study, we compare the accuracy of a single-pool variable volume calcium kinetic model (SPVV-CaKM) using two different dialysate calcium concentrations (CaD). Methods: Pre- and post-treatment relevant variables of 34 patients treated with nominal CaD of 1.5 mmol/l (Group 1) and 22 patients with nominal CaD of 1.75 mmol/l (Group 2) were analyzed. The accuracy was evaluated determining the difference between predicted (Ca2+pwtP) and measured (Ca2+pwt) plasma water ionized calcium concentrations at the end of the dialysis sessions. To account for the changes in blood pH during dialysis session, which is known to affect plasma water ionized calcium concentrations, Ca2+pwt values were normalized at pH of 7.40. Results: Fig. 1 indicate that the predicted values almost overlap t he normalized values for Group 1, while it’s significantly higher for Group 2. Conclusion: The SPVV-CaKM is accurate in Group 1 while it overestimates the Ca2+pwt Group 2. The Ca2+pwt of the two groups doesn’t seem to account for the increased CaD. This suggests the presence of an additional compartment. Our hypothesis is that the administered calcium, predicted by our model, that doesn’t appear plasma could be deposited in bones and/or soft tissues. It is then theoretically possible to estimate the total calcium deposition or accumulation from the difference between predicted and measured post-treatment values.