Assessment of intradialysis calcium mass balance by a single pool variable-volume calcium kinetic model.
A reliable method of intradialysis calcium mass balance quantification is far from been established. We herein investigated the use of a single-pool variable-volume Calcium kinetic model to assess calcium mass balance in chronic and stable dialysis patients.



Thirty-four patients on thrice-weekly HD were studied during 240 dialysis sessions. All patients were dialyzed with a nominal total calcium concentration of 1.50 mmol/L. The main assumption of the model is that the calcium distribution volume is equal to the extracellular volume during dialysis. This hypothesis is assumed valid if measured and predicted end dialysis plasma water ionized calcium concentrations are equal. A difference between predicted and measured end-dialysis ionized plasma water calcium concentration is a deviation on our main hypothesis, meaning that a substantial amount of calcium is exchanged between the extracellular volume and a nonmodeled compartment.



The difference between predicted and measured values was 0.02 mmol/L (range -0.08:0.16 mmol/L). With a mean ionized dialysate calcium concentration of 1.25 mmol/L, calcium mass balance was on average negative (mean ± SD -0.84 ± 1.33 mmol, range -5.42:2.75). Predialysis ionized plasma water concentration and total ultrafiltrate were the most important predictors of calcium mass balance. A significant mobilization of calcium from the extracellular pool to a nonmodeled pool was calculated in a group of patients.



The proposed single pool variable-volume Calcium kinetic model is adequate for prediction and quantification of intradialysis calcium mass balance, it can evaluate the eventual calcium transfer outside the extracellular pool in clinical practice.
Depatments of Nephrology and Dialysis, A. Manzoni Hospital, Lecco, Italy.
Salvatore
S
di Filippo
Depatments of Nephrology and Dialysis, A. Manzoni Hospital, Lecco, Italy.
Fabio
0000-0002-1378-1649
F
Carfagna
Depatments of Nephrology and Dialysis, A. Manzoni Hospital, Lecco, Italy.
Vincenzo
V
la Milia
Depatments of Nephrology and Dialysis, Sant'Anna Hospital, Como, Italy.
Antonio
A
Bellasi
Depatments of Chemistry, Material and Chemical Engineering, Politecnico di Milano, Milano, Italy.
Giustina
G
Casagrande
Depatments of Chemistry, Material and Chemical Engineering, Politecnico di Milano, Milano, Italy.
Camilla
C
Bianchi
Depatments of Chemistry, Material and Chemical Engineering, Politecnico di Milano, Milano, Italy.
Domenico
D
Vito
Depatments of Chemistry, Material and Chemical Engineering, Politecnico di Milano, Milano, Italy.
Maria Laura
ML
Costantino
Depatments of Nephrology and Dialysis, Hospital and Macchi Foundation, Varese, Italy.
Giuseppe
G
Rombolà
Depatments of Nephrology and Dialysis, Sant'Anna Hospital, Como, Italy.
Claudio
C
Minoretti
Depatments of Nephrology and Dialysis, Regional Hospital of Lugano, Lugano, Switzerland.
Carlo
C
Schönholzer
Depatments of Nephrology and Dialysis, A. Manzoni Hospital, Lecco, Italy.
Giuseppe
G
Pontoriero
Depatments of Nephrology and Dialysis, A. Manzoni Hospital, Lecco, Italy.
Francesco
F
Locatelli
D000368:Aged; D002118:Calcium / Q000378:metabolism*; D005260:Female; D015312:Hemodialysis Solutions / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008297:Male; D006435:Renal Dialysis / Q000379:methods*
D015312:Hemodialysis Solutions; D002118:Calcium
Calcium and phosphate metabolism; kinetics; mathematical models