Ca Flux across the Dialyzer

It is anticipated that we can describe Ca mass balance across the dialyzer as follows: the mechanism of transport of ionized Ca out of the blood compartment (JbCa) is dialysance (DCa) which is defined as:

for simplification the valence number is dropped but all flux equations assume ionized or diffusible Ca.

From mass balance across the blood compartment we can write:

Combine equations 1 and 2 to define dialysance as:

Fig. 2. Ca modeling equations must contain a term for rapid mobilization and sequestration of Ca during dialysis with a concentration gradient for Ca between plasma and dialysate.

Ca

M+Ca

CdiCa > CPiCa

buffer

d(Qa*VCa)/dt

JdCa = MCa + DCa(CdiCa - Cpi^,)

pool

M-Ca

CdiCa < CPiCa

Constant rate

Constant rate

From mass balance across the dialysate compartment we can write:

Since JpCa = JdCa, combine equations 3 and 4 to calculate Qe:

Qe = [(Cdoca - Cdica)*Qdica + Cdoca(Qf) - Cbica(Qf)]/

It is very likely that Qe, which is the effective blood diffusion volume flow rate, is equal to the plasma water flow rate but will require verification with in vivo data to solve equation 5. Note that all concentrations are expressed as the aqueous concentration of ionized Ca in the blood and dialysate compartments.

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