Determination of the anesthetic state of a patient

• US 20060217628A1
• Filed: 03/24/2005
• Published: 09/28/2006
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Huiku, Matti
• Granted Patent: US 7,925,338 B2
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: A61B 5/4076 Diagnosing or monitoring particular conditions of the nervous system A61B5/4821, A61B5/4824 take precedence
• CPC Class Codes: A61B 5/4821 Determining level or depth of anaesthesia A61B5/1106 takes precedence
• CPC Class Codes: A61B 5/4824 Touch or pain perception evaluation A61B5/4821 takes precedence
• CPC Class Codes: A61B 5/4839 combined with drug delivery

Abstract

The invention relates to the determination of the anesthetic state of a patient. In order to achieve a mechanism that enables establishment and maintenance of balanced anesthesia, values are established for a set of diagnostic indices. The set includes at least two diagnostic indices of which a first diagnostic index is indicative of the level of hypnosis and a second diagnostic index of the level of nociception in the patient. The combination of the at least two index values obtained is employed for indicating the anesthetic state of the patient. The combination of the at least two index values may further be employed to control the administration of drugs to the patient.

Claims

1. A method for determining the anesthetic state of a patient, the method comprising the steps of:

establishing values for a set of diagnostic indices, the set including at least two diagnostic indices of which a first diagnostic index is indicative of the hypnotic level in a patient and a second diagnostic index of the level of analgesia in the patient, whereby at least two index values are obtained; and

employing the at least two index values for indicating the anesthetic state of the patient.

2. A method according to claim 1, wherein the employing step includes the sub-steps of:

determining a location corresponding to the at least two index values in a space defined by said at least two diagnostic indices; and

employing the location as the indicator of the anesthetic state of the subject.

3. A method according to claim 1, wherein the employing step includes a sub-step of deriving at least one displacement measure indicative of the displacement of said location from at least one predetermined reference point in said space.

4. A method according to claim 3, wherein the at least one predetermined reference point comprises a domain defined by desired value ranges of the at least two diagnostic indices.

5. A method according to claim 3, wherein the at least one predetermined reference point comprises a single reference point defined by predetermined reference values of the at least two diagnostic indices.

6. A method according to claim 1, wherein the employing step includes a sub-step of indicating the at least two index values through an indicator unit to a user.

7. A method according to claim 2, wherein the employing step includes a sub-step of indicating the location through an indicator unit to a user.

8. A method according to claim 6, wherein the indicating sub-step includes displaying at least two curves, each curve representing the values of a corresponding diagnostic index during a preceding time period of a certain length.

9. A method according to claim 7, wherein the indicating sub-step further includes indicating at least one predetermined reference point in said space, the at least one reference point representing a targeted anesthetic state of the patient.

10. A method according to claim 1, further comprising a step of controlling administration of at least one drug to the patient, wherein the at least one drug belongs to a group of drugs including at least one analgesic drug and at least one hypnotic drug.

11. A method according to claim 3, further comprising a step of controlling administration of at least one drug to the patient, wherein the at least one drug belongs to a group of drugs including at least one analgesic drug and at least one hypnotic drug, the controlling step being performed based on the at least one displacement measure.

12. A method according to claim 11, wherein the at least one displacement measure is indicative of the distance and direction of the at least one predetermined reference point from said location.

13. A method according to claim 1, wherein the establishing step comprises the sub-steps of:

obtaining EEG signal data from the patient;

deriving a measure of the complexity of the EEG signal data; and

employing said measure as the first diagnostic index.

14. A method according to claim 13, wherein the deriving sub-step includes determining an entropy of the EEG signal data.

15. A method according to claim 1, wherein the establishing step comprises the sub-steps of:

acquiring a first measurement signal containing physiological data indicative of the cardiovascular function of the patient;

applying a first normalization transform to the first measurement signal, the first normalization transform being dependent on previous signal data of said first measurement signal, whereby a first normalized measurement signal having a predetermined value range is obtained;

forming an index proportional to the first normalized measurement signal; and

employing said index as the second diagnostic index.

16. A method according to claim 15, wherein the forming sub-step includes employing the first normalized signal directly as said index.

17. A method according to claim 15, further comprising the steps of

determining at least one patient-specific value for at least one predetermined parameter of the first measurement signal;

and

substituting the at least one patient-specific value for at least one parameter in a predetermined parameterized transform to obtain the first normalization transform.

18. A method according to claim 15, wherein the applying sub-step includes applying a histogram transform to the first measurement signal.

19. A method according to claim 18, wherein the acquiring sub-step includes deriving the first measurement signal from a plethysmographic signal measured from the patient.

20. A method according to claim 18, wherein the acquiring sub-step includes deriving the first measurement signal from a blood pressure signal measured from the subject.

21. A method according to claim 3, wherein the employing step further includes determining, based on the at least one displacement measure, a first measure indicative of the difference in the level of nociception between said location and the at least one predetermined reference point and a second measure indicative of the difference in the level of hypnosis between said location and the at least one predetermined reference point.

22. A method according to claim 21, further comprising a step of selecting at least one drug to be administered based on said first and second measures.

23. A method according to claim 22, wherein the selecting step includes employing a pharmacokinetic model.

24. A method according to claim 22, wherein the selecting step includes employing a pharmacodynamic model.

25. A method according to claim 1, wherein the establishing step includes establishing values for three diagnostic indices, wherein a third diagnostic index is indicative of the level of neuromuscular blockade in the patient.

26. A method according to claim 1, further comprising a step of determining, based on the second diagnostic index, at least one reference value serving as an instruction for administering a drug to the subject.

27. A method according to claim 1, further comprising a step of determining, based on the first diagnostic index, at least one reference value serving as an instruction for administering a drug to the subject.

28. An apparatus for determining the anesthetic state of a patient, the apparatus comprising:

first means for establishing values for a set of diagnostic indices, the set including at least two diagnostic indices of which a first diagnostic index is indicative of the hypnotic level in a patient and a second diagnostic index of the level of nociception in the patient, whereby at least two index values are obtained; and

second means for employing the at least two index values for indicating the anesthetic state of the patient.

29. An apparatus according to claim 28, wherein the second means are configured to determine a location corresponding to the at least two index values in a space defined by said at least two diagnostic indices.

30. An apparatus according to claim 29, wherein the second means include displacement determination means for deriving at least one displacement measure indicative of the displacement of said location from at least one predetermined reference point in said space.

31. An apparatus according to claim 30, wherein the at least one displacement measure is indicative of the distance and direction of the at least one predetermined reference point from said location.

32. An apparatus according to claim 28, further comprising drug delivery means for administering at least one drug to the patient, wherein the at least one drug belongs to a group including at least one analgesic drug and at least one hypnotic drug.

33. An apparatus according to claim 32, further comprising control means for controlling the drug delivery means, the control means being operably connected to the displacement determination means.

34. An apparatus according to claim 33, wherein the control means are configured to derive at least one displacement measure indicative of the displacement of said location from at least one predetermined reference point in said space.

35. An apparatus according to claim 34, wherein the control means are configured to determine, based on the at least one displacement measure, a first measure indicative of the difference in the level of nociception between said location and the at least one predetermined reference point and a second measure indicative of the difference in the level of hypnosis between said location and the at least one predetermined reference point.

36. An apparatus according to claim 28, wherein the first means comprise:

means for obtaining EEG signal data from the patient; and

calculation means for deriving a measure of the complexity of the EEG signal data, said measure serving as the first diagnostic index.

37. An apparatus according to claim 36, wherein the calculation means are configured to calculate an entropy of the EEG signal data.

38. An apparatus according to claim 28, wherein the first means comprise:

means for acquiring a first measurement signal containing physiological data indicative of the cardiovascular function of the patient;

first transform means for applying a first normalization transform to the first measurement signal, the first normalization transform being dependent on previous signal data of said first measurement signal, whereby a first normalized measurement signal having a predetermined value range is obtained; and

means for forming an index proportional to the first normalized measurement signal, said index serving as the second diagnostic index.

39. An apparatus according to claim 38, further comprising:

measurement means for determining at least one patient-specific value for at least one predetermined parameter of the first measurement signal; and

means for substituting the at least one patient-specific value for at least one parameter in a predetermined parameterized transform to obtain the first normalization transform.

40. An apparatus according to claim 38, wherein the first transform means are configured to apply a histogram transform to the first measurement signal.

41. An apparatus according to claim 28, further comprising an indicator unit for indicating the at least two index values to a user.

42. An apparatus according to claim 29, further comprising an indicator unit for indicating the location to a user.

43. An apparatus according to claim 42, wherein the indicator unit is configured to indicate at least one predetermined reference point in said space, the at least one reference point representing a targeted anesthetic state of the patient.

44. An apparatus according to claim 41, wherein the indicator unit is configured to display at least two curves, each curve representing the values of a corresponding diagnostic index during a preceding time period of a certain length.

45. An apparatus for determining the anesthetic state of a patient, the apparatus comprising:

a measurement device configured to establish values for a set of diagnostic indices, the set including at least two diagnostic indices of which a first diagnostic index is indicative of the hypnotic level in a patient and a second diagnostic index of the level of nociception in the patient, whereby at least two index values are obtained;

a first controller configured to employ the at least two index values for indicating the anesthetic state of the patient.

46. An apparatus according to claim 45, wherein the first controller is configured to determine a location in a space defined by said at least two diagnostic indices, the location being determined by the at least two index values.

47. A computer program product for determining the anesthetic state of the patient, the computer program product comprising:

a first program code portion configured to establish values for a set of diagnostic indices, the set including at least two diagnostic indices of which a first diagnostic index is indicative of the hypnotic level in a patient and a second diagnostic index of the level of nociception in the patient, whereby at least two index values are obtained; and

a second program code portion configured to employ the at least index values for indicating the anesthetic state of the patient.

48. A computer program product according to claim 47, wherein the second program code portion is configured to determine a location corresponding to the at least two index values in a space defined by said at least two diagnostic indices.

49. A method for controlling the anesthetic state of a patient, the method comprising the steps of:

establishing values for a set of diagnostic indices, the set including at least two diagnostic indices of which a first diagnostic index is indicative of the hypnotic level in a patient and a second diagnostic index of the level of analgesia in the patient, whereby at least two index values are obtained; and

controlling, based on the at least two index values, administration of at least one drug to the patient, wherein the at least one drug belongs to a group of drugs including at least one analgesic drug and at least one hypnotic drug.

50. A system for controlling the anesthetic state of a patient, the system comprising:

means for establishing values for a set of diagnostic indices, the set including at least two diagnostic indices of which a first diagnostic index is indicative of the hypnotic level in a patient and a second diagnostic index of the level of analgesia in the patient;

drug delivery means for administering at least one drug to the patient, wherein the at least one drug belongs to a group of drugs including at least one analgesic drug and at least one hypnotic drug; and

control means for controlling the drug delivery means based on the at least two diagnostic indices.