Urea monitoring during dialysis for improved quality control and treatment guidance

1 . A method of conducting dialysis, comprising:

measuring a concentration of urea in a dialysis effluent over time;

determining a rate of change in urea concentration;

identifying a rate of peripheral perfusion and changes in the rate of peripheral perfusion from the rate of change in urea concentration in real-time or near real-time using a multi-compartment model, and

operating a dialysis machine based on the identified rate of peripheral perfusion and changes in the rate of peripheral perfusion,

wherein the rate of peripheral perfusion is determined from the following equations:

dU

c

dt

=

-

K

V

c

⁢

U

c

+

Q

p

(

U

p

-

U

c

)

⁢

and

⁢

dU

p

dt

=

-

Q

p

(

U

p

-

U

c

)

V

p

;

wherein U p is a peripheral concentration,

wherein U c is a core concentration,

wherein Q p is the rate of peripheral perfusion,

wherein V p is a peripheral volume

wherein V c is a core volume, and

wherein K is a dialyzer clearance value.

2 . The method of claim 1 , wherein the concentration of urea is measured in real time or near-real time.

3 . The method of any of claim 1 , wherein the concentration of urea is measured via a near-infrared spectroscopic sensor or electrochemical biosensor.

4 . The method of any of claim 1 , wherein the concentration of urea is measured on a dialysate effluent line.

5 . The method of any of claim 1 , wherein the concentration of urea is measured on a dialysis machine after a dialyzer.

6 . The method of any of claim 1 , further comprising storing urea concentration data for a patient over multiple dialysis treatments generating a urea concentration profile.

7 . The method of any of claim 1 , further comprising alerting a user to a change in the rate of peripheral perfusion that is indicative of an adverse hemodynamic event.

8 . The method of any of claim 1 , further comprising determining a dialysis dosage actually given.

9 . The method of any of claim 1 , further comprising measuring the concentration of urea before and after a dialyzer to measure urea clearance by a dialyzer membrane.

10 . A system for monitoring dialysis, comprising:

(a) a dialysis machine;

(b) a urea monitoring sensor disposed on the dialysis machine, the urea monitoring sensor configured to measure a concentration of urea over time; and

(c) a processor in communication with the urea monitoring sensor, wherein the processor determines a rate of change in the concentration of urea over time using a multi-compartment model, and wherein the processor determines a rate of peripheral perfusion;

wherein the dialysis machine is configured to control dialysis parameters based on a determination of the rate of peripheral perfusion;

wherein the rate of peripheral perfusion is determined from the following equations:

dU

c

dt

=

-

K

V

c

⁢

U

c

+

Q

p

(

U

p

-

U

c

)

and

dU

p

dt

=

-

Q

p

(

U

p

-

U

c

)

V

p

;

wherein U p is a peripheral concentration,

wherein U c is a core concentration,

wherein Q p is the rate of peripheral perfusion,

wherein V p is a peripheral volume

wherein V c is a core volume, and

wherein K is a dialyzer clearance value.

11 . The system of claim 10 , wherein the urea monitoring sensor is a non-destructive near infrared spectroscopic sensor or an electrochemical biosensor.

12 . The system of any of claim 10 , wherein the urea monitoring sensor is in communication with a dialysate effluent line of the dialysis machine.

13 . The system of any of claim 10 , wherein the urea monitoring sensor is located adjacent to a dialyzer of the dialysis machine.

14 . The system of any of claim 10 , further comprising an ultrafiltration port and wherein the urea monitoring sensor is configured to measure urea concentration in a blood ultrafiltrate from the ultrafiltration port.

15 . The system of any of claim 10 , wherein the calculation of the rate of peripheral perfusion is adjusted to account for one or more of urea generation during dialysis, residual kidney clearance, ultrafiltration, interruptions to dialysis due to bypass or machine warnings, and changes in the dialysis parameters.

16 . The system of any of claim 10 , wherein the processor is configured to detect inadequate perfusion or changes in peripheral perfusion that signal the onset of hemodynamic instability and/or impending hypotensive events.

17 . A method of conducting hemodialysis measuring peripheral perfusion during hemodialysis comprising:

measuring urea concentration in used dialysate;

generating a urea concentration profile;

determining a rate of change in urea concentration over time; and

determining a rate of peripheral perfusion from the following equations:

dU

c

dt

=

-

K

V

c

⁢

U

c

+

Q

p

(

U

p

-

U

c

)

and

dU

p

dt

=

-

Q

p

(

U

p

-

U

c

)

V

p

;

wherein U p is a peripheral concentration,

wherein U c is a core concentration,

wherein Q p is the rate of peripheral perfusion,

wherein V p is a peripheral volume,

wherein V c is a core volume, and

wherein K is a dialyzer clearance value; and

operating a dialysis machine based on the identified rate of peripheral perfusion and changes in the rate of peripheral perfusion.