Method for measuring the concentration of substances in living organisms using microdialysis and a device for carrying out said method

• US 20040168934A1
• Filed: 01/06/2004
• Published: 09/02/2004
• Est. Priority Date: 07/06/2001
• Status: Active Grant

• Current Assignee: Lukas Schaupp, Thomas Pieber
• Original Assignee: Lukas Schaupp, Thomas Pieber
• Inventors: Schaupp, Lukas, Pieber, Thomas
• Granted Patent: US 7,022,071 B2
• Time in Patent Office: Days
• US Class Current: 205/777.5
• CPC Class Codes: A61B 5/14525 using microdialysis
• CPC Class Codes: A61B 5/14528 invasively
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence

Abstract

The invention relates to a method for measuring the concentration of substances in living organisms using microdialysis, whereby bodily fluid is mixed with a perfusate and passed through a membrane and a substance value is determined for the bodily fluid with the aid of a sensor unit. According to the invention, to allow for the limited transport through the membrane, so that the measured substance value differs from the actual substance value in the organism, a reference substance present in said organism with a known value is also measured after passing through the membrane and mixing with the perfusate and the actual substance value is determined, based on the quotient from the known reference substance value divided by the measured reference substance value, multiplied by the measured substance value.

Claims

1. Method for measuring the concentration of substances in living organisms using microdialysis, wherein bodily fluid is mixed with a perfusate and passed through a membrane, and a substance value of the bodily fluid is determined using a sensor unit, characterized in that in order to take into consideration the restricted transport through the membrane, so that the measured substance value differs from the actual substance value in the organism, a reference substance present in the organism, having a known value, is measured after passing through the membrane and mixing with the perfusate, and the actual substance value is determined on the basis of the quotient of the known reference substance value divided by the measured reference substance value, multiplied by the measured substance value.

2. Method according to claim 1, characterized in that any different transport behavior of the reference substance and the substance to be measured is taken into consideration by means of a correction factor that is determined in advance.

3. Method according to claim 2, characterized in that the correction factor is determined in advance, in vitro, by mixing a solution with ions and the substance to be determined, and passing it through a membrane.

4. Method according to claim 2, characterized in that the correction factor is determined in advance, in vivo, by measuring the substance value in the blood.

5. Method according to one of claims 1 to 4, characterized in that the measurement of the value to be determined is performed on the basis of measuring the electrical conductivity, corresponding to the sum of ions.

6. Method according to one of claims 1 to 5, characterized in that in order to achieve high flow-through rates, the perfusate or the mixture of perfusate/bodily fluid is pumped into and out of the body.

7. Device for measuring the concentration of substances in living organisms using microdialysis, having a microdialysis catheter (3) that has a membrane (26), through which bodily fluid is mixed with a perfusate that is supplied from a perfusate reservoir (1), and having a sensor unit (4) for determining a substance value of the bodily fluid, characterized in that the membrane (26) is also set up for passage of a reference substance present in the organism, having a known value, and this reference substance is measured after passing through the membrane and mixing with the perfusate, using the sensor unit (4), to which an electronic evaluation unit (8) is connected, with which the actual substance value is determined on the basis of the quotient of the known reference substance value divided by the measured reference substance value, multiplied by the measured substance value.

8. Device according to claim 7, characterized in that a pump unit (2, 5) is arranged both in the inflow (24′

) and the outflow (25′

) of the microdialysis catheter (3).

9. Device according to claim 8, characterized in that the two pump units (2, 5) are synchronized.

10. Device according to claim 8 or 9, characterized in that the pump unit (5) on the outflow side is arranged behind the sensor unit (4), viewed in the flow direction.

11. Device according to one of claims 8 to 10, characterized in that the two pump units (2, 5) are formed by peristalsis pumps.

12. Device according to one of claims 7 to 11, characterized in that the sensor unit (4) has electrodes (46, 47, 48, 49;

42, 43) for determining the conductivity of the fluid that flows through.