Recirculating dialysate fluid circuit for blood measurement

A method for measuring the solute concentration of at least one blood solute species during a fluid therapy, comprising the steps of:

• switching fluid flow from a first flow path to a dialyzer recirculation flow path;
• equilibrating a dialysate with a blood side of a dialyzer;
• and
• measuring the solute concentration in the dialysate that has been equilibrated with the blood side of the dialyzer.

A method for measuring BUN via the use of fluid therapy device including a sorbent regeneration system and a dialyzer, comprising the steps of:

• switching fluid flow in the fluid therapy device from a first flow path to a sorbent bypass fluid path;
• recirculating a dialysate through the dialyzer;
• and
• equilibrating the dialysate with blood in the blood side of the dialyzer.

A method for measuring the solute concentration of at least one blood solute species, comprising the steps of:

• switching fluid flow in a fluid therapy device having a sorbent regeneration system and a dialyzer from a first flow path to a sorbent bypass fluid path;
• recirculating a dialysate through the dialyzer;
• and
• equilibrating the dialysate with blood in the blood side of the dialyzer;
• and
• measuring the conductivity of the equilibrated dialysate before the dialysate has contacted a predetermined layer or sequence of layers to provide a first conductivity value;
• and
• switching the fluid flow from the sorbent bypass fluid path to cause the equilibrated dialysate to contact a predetermined material layer or sequence of material layers in the sorbent system;
• and
• measuring the conductivity of the equilibrated dialysate after it has contacted the predetermined material layer or sequence of material layers to provide a second conductivity value.

A method to measure BUN (blood urea nitrogen), comprising:

• measuring a first conductivity value of a dialysate flowing from an outlet of a 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 fluid 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;
• and
• determining the effective clearance of the dialyzer from the third and fourth conductivity values.