Recirculating dialysate fluid circuit for blood measurement
A blood based solute monitoring system for measuring at least one blood solute species that has a first recirculation flow path in fluid communication with a dialyzer. The first recirculation flow path is configured to allow a fluid to recirculate through a dialyzer such that the concentration of at least one solute species in the fluid becomes equilibrated to the solute species concentration of the blood in a blood compartment of the dialyzer. The blood solute monitoring system has at least one sensor to measure a fluid characteristic.
1. A method for determining an effective clearance of a dialyzer, comprising:
measuring a first conductivity value of a dialysate flowing from an outlet of the dialyzer not having contacted a urease containing material layer of a sorbent regeneration system;
measuring a second conductivity value of the dialysate flowing from the outlet of the dialyzer after the dialysate has contacted the urease containing material layer of the sorbent regeneration system;
intermittently providing an electrolyte bolus or diluent to a dialysate flow path and measuring a bolus conductivity of the dialysate passing to the dialyzer to provide a third conductivity value;
measuring a bolus conductivity of the dialysate passing from the dialyzer to provide a fourth conductivity value;
measuring a dialysate flow rate; and
determining the effective clearance of the dialyzer from the third and fourth conductivity values.
2. The method of claim 1 , further comprising:
determining a BUN (blood urea nitrogen) and/or a blood concentration of a solute from the effective clearance of the dialyzer from the first and second conductivity values.
3. The method of claim 1 , further comprising the step of determining a urea content of the dialysate flowing from the dialyzer based at least in part on a difference in conductivity between the first and second conductivity values.
4. The method of claim 1 , wherein the dialysate contacts a plurality of materials of the sorbent regeneration system in a sequential order; wherein the plurality of materials are contained in one or more sorbent cartridges, and wherein at least one material includes an ion exchange resin selective for calcium ions and magnesium ions and releasing hydrogen ions in exchange.
5. The method of claim 1 , further comprising:
determining a third conductivity value of the equilibrated dialysate that has contacted an additional material layer other than the material layer(s) contacted by the dialysate of the first or second conductivity value; and
determining a blood solute concentration of at least a second blood solute from either the second and third conductivity values or the first and third conductivity values.
6. The method of claim 1 , further comprising calculating one or more of the selected measures: URR (urea reduction ratio), Kt/V, eKt/V (equilibrated Kt/V), and PCR (protein catabolic rate), wherein K stands for dialyzer clearance rate, t stands for dialysis time, and V stands for volume of distribution of urea; and wherein Kt/V, eKt/V and PCR are each determined based on a difference between the first and second conductivity values; and wherein URR is determined by calculating a first BUN (blood urea nitrogen) prior to dialysis and a second BUN (blood urea nitrogen) post dialysis.