Feedback control of ultrafiltration to prevent hypotension

• US 20020085951A1
• Filed: 12/29/2000
• Published: 07/04/2002
• Est. Priority Date: 12/29/2000
• Status: Active Grant

• Current Assignee: Gambro Lundia AB (Baxter International Inc.)
• Original Assignee: CHF Solutions, Inc.
• Inventors: Levin, Howard R., Gelfand, Mark, OʼMahony, John
• Granted Patent: US 6,706,007 B2
• Time in Patent Office: Days
• US Class Current: 422/44
• CPC Class Codes: A61M 1/34 Filtering material out of the blood by passing it through a membrane, i.e. hemofiltration or diafiltration
• CPC Class Codes: A61M 1/341 by measuring the filtrate rate or volume
• CPC Class Codes: A61M 1/36 Other treatment of blood in a by-pass of the natural circulatory system, e.g. temperature adaptation, irradiation ; Extra-corporeal blood circuits
• CPC Class Codes: A61M 2205/3303 Using a biosensor
• CPC Class Codes: A61M 2205/3306 Optical measuring means
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3375 Acoustical, e.g. ultrasonic, measuring means
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)

Abstract

A method and system for the extracorporeal treatment of blood to remove fluid from the fluid overloaded patient is disclosed that non-invasively measures an oxygen level in the venous blood. The oxygen blood level is used to detect when hypotension is about to occur in a patient. The oxygen level measurements are used as feedback signals. These feedback signals are applied to automatically control the rate of fluid extraction to achieve the desired clinical outcome and avoid precipitating a hypotensive crisis in the patient.

Claims

1. A method for preventing hypotension in a mammalian patent whose blood is being withdrawn, treated in a blood treatment device of an extracorporeal blood circuit for removal of fluid, and infused into the patient, said method comprising the steps of:

a. monitoring oxygen concentration in blood flowing through the circuit, and

b. adjusting a flow rate of ultrafiltrate extracted from blood if the oxygen concentration in blood varies from a predetermined target value.

2. A method for preventing hypotension as in claim 1 wherein the oxygen concentration is a mixed venous oxygen saturation (SvO₂) level.

3. A method for preventing hypotension as in claim 1 wherein the oxygen concentration is a venous oxygen saturation (SvO₂) level of blood taken from a peripheral vein.

4. A method as in claim 1 where oxygen concentration is measured at a blood withdrawal tube of the extracorporeal circulation circuit between a patient connection and a blood pump

5. A method for preventing hypotension as in claim 2 wherein the target value is the sum of an oxygen concentration level determined during an initial phase of treating the blood in the circuit and a predetermined oxygen change value.

6. A method for preventing hypotension as in claim 5 wherein the predetermined change value is selected by an operator.

7. A method for preventing hypotension as in claim 5 wherein the predetermined change value is no greater than a seven percent difference than the determined initial oxygen saturation level.

8. A method for preventing hypotension as in claim 1 wherein the target value is preprogrammed in a controller for the circuit.

9. A method for preventing hypotension as in claim 1 wherein the oxygen concentration is determined using an optical biosensor.

10. A method for preventing hypotension as in claim 1 wherein the oxygen concentration is applied to estimate cardiac output and, in step b, reducing filtration if the estimated cardiac output falls a predetermined amount.

11. A method for preventing hypotension as in claim 1 wherein the oxygen concentration is relative to an initial oxygen concentration level.

12. A method for preventing hypotension as in claim 1 wherein the oxygen concentration is an oxygen concentration of blood in the circuit.

14. A method of controlling an extracorporeal blood circuit as in claim 13 wherein the cardiac output level is determined by monitoring oxygen level of the venous blood.

15. A method of controlling an extracorporeal blood circuit as in claim 13 wherein the blood circuit includes an oxygen saturation sensor having an emitter and a receiver mounted on opposite sides of a bloodline of said circuit.

16. A method of controlling an extracorporeal blood circuit as in claim 13 wherein the controlled filtration rate is reduced by temporarily stopping filtration.

17. A method of controlling an extracorporeal blood circuit as in claim 13 wherein the controlled filtration rate is reduced by slowing an ultrafiltration pump.

18. A method of controlling an extracorporeal blood circuit as in claim 13 wherein the controlled filtration rate is determined by cyclically starting and stopping the filtration of fluids in accordance with a duty cycle, and the filtration rate is reduced by reducing an OFF period of the duty cycle.

20. A system as in claim 19 wherein the feedback signal is indicative of an oxygen level in the venous blood.

21. A system as in claim 19 wherein the feedback signal threshold is determined based on a sum of a feedback signal obtained during an initial phase of a treatment of the patient and a predetermined current feedback signal change.

22. A system as in claim 19 wherein the filter is a hemofilter.

23. A system as in claim 19 wherein the treatment device is a dialysis filter.

24. A system as in claim 19 wherein the treatment device is an ultrafiltration filter.

13. A method of controlling an extracorporeal blood circuit comprising the steps of:

a. withdrawing blood from a withdrawal blood vessel in a patient into the extracorporeal circuit;

b. filtering fluids from blood flowing through the circuit at a controlled filtration rate;

c. estimating a cardiac output level of the patient;

d. reducing the filtration flow rate if the measured cardiac output falls below a threshold level.

19. A system for treating blood from a patient comprising:

an extracorporeal circuit having a blood passage including a blood withdrawal tube, a filter and an infusion tube,

said filter having filter blood passage in fluid communication with the withdrawal tube, a blood outlet in fluid communication with the infusion tube, a filter membrane in fluid communication with the blood passage, a filter output section on a side of the membrane opposite to the blood passage, and a filtrate output line in fluid communication with the filter output section;

a biosensor coupled to said extracorporeal circuit and generating a feedback signal indicative of cardiac output of the patient;

a filtrate pump coupled to the filtrate output line and adapted to draw filtrate fluid from the filter at a controlled filtration rate, and

a filtrate pump controller regulating the controlled filtration rate based on the feedback signal, wherein the pump controller includes a processor and a memory storing a control algorithm to determine whether a feedback signal threshold is exceeded by the feedback pressure signal, said controller reducing the controlled filtration if the feedback signal exceeds the feedback signal threshold.