WO2015079355A1

WO2015079355A1 - Methods for estimating dosage of anesthetic agent and for determining depth of anesthesia

Info

Publication number: WO2015079355A1
Application number: PCT/IB2014/066083
Authority: WO
Inventors: Syed Waseem HAIDER; Nicolas Wadih Chbat
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-11-26
Filing date: 2014-11-17
Publication date: 2015-06-04

Abstract

A method includes obtaining, in electronic format, demographics, current hemodynamics, and current vital signs of a current patient. The method further includes obtaining, in electronic format, stored demographics, hemodynamics, vital signs, and administered anesthetic agent doses of previous patients. The method further includes estimating an anesthetic agent dose for the current patient based on the demographics, hemodynamics and vital signs of the current patient and the demographics, hemodynamics, vital signs, and administered anesthetic agent dose of the previous patients and generating a signal indicative of the estimate.

Description

METHODS FOR ESTIMATING DOSAGE OF ANESTHETIC AGENT AND

FOR DETERMINING DEPTH OF ANESTHESIA

The following generally relates to estimating a dose of an anesthetic agent for a patient and/or determining a depth of anesthesia of a patient.

General anesthesia is a medically induced coma and loss of protective reflexes resulting from a general anesthetic. The overall aim is ensuring sleep, amnesia, analgesia, relaxation of skeletal muscles, and loss of control of reflexes of the autonomic nervous system. The central nervous system is progressively depressed under general anesthesia. Different stages of anesthesia will accompany different physiological reflexes and responses. When deeply anesthetized, example responses include respiratory depression, severe muscle relaxation, bradycardia, no reflexes (palpebral, corneal), and pupils dilated. With very deep anesthesia, respiration ceases, cardiovascular function depresses and death ensues.

The American Society of Anesthesiologists (ASA) provides a guideline for the Depth of Sedation due to anesthesia and its assessment. They categorize the levels into four categories, minimal sedation anxiolysis, moderate sedation/analgesia ('Conscious Sedation*), deep sedation/analgesia, and general anesthesia. These categories serve anesthesiologists as assessment guidelines. Depth of anesthesia is dependent on the balance between two competing factors: the anesthetic dose and surgical stimulation. Optimal depth of anesthesia requires a sufficient amount of anesthetic to achieve and maintain

unconsciousness without compromising vital organ function.

The dilemma for the anesthesiologist is: give too small an anesthetic dose and the patient may experience intraoperative recall and too large an anesthetic dose may convey risk to the patient (e.g., decrease organ perfusion) and increase the incidence of troublesome side effects (e.g., delayed awakening). The optimal depth of anesthesia depends on finding a balance amongst multiple anesthetic goals while keeping patient safe and comfortable. Goals are: avoid intraoperative awareness; optimize quality of recovery; maintain optimal hemodynamics; avoid post-operative neurocognitive dysfunction, and avoid post-operative mortality. Typically, the anesthesiologist observes the patient and the vital signs of the patient and manually adjusts the amount of anesthetic agent administered with the above goals in mind. Unfortunately, the above noted goals can be difficult to achieve using this approach.

Aspects described herein address the above-referenced problems and others.

The following describes an approach for estimating a dose of an anesthetic agent for a patient for a procedure and/or assessing a current a dose of the anesthetic agent during a procedure. The latter entails determining a current depth of anesthesia metric. The estimate and/or the assessment are determined based hemodynamics, vital signs,

demographics, and previously administered anesthetic agents.

In one aspect, a method includes obtaining, in electronic format, demographics, current hemodynamics, and current vital signs of a current patient. The method further includes obtaining, in electronic format, stored demographics,

hemodynamics, vital signs, and administered anesthetic agent doses of previous patients. The method further includes estimating an anesthetic agent dose for the current patient based on the demographics, hemodynamics and vital signs of the current patient and the demographics, hemodynamics, vital signs, and administered anesthetic agent dose of the previous patients and generating a signal indicative of the estimate.

In another aspect, a system includes a computing system with at least one computer processor and computer readable storage medium encoded with computer readable instructions for an initial dose estimator. The at least one computer processor, in response to executing instructions of the initial dose estimator, estimates an anesthetic agent dose for a current patient based on demographics, current hemodynamics and current vital signs of the current patient and demographics, hemodynamics, vital signs, and administered anesthetic agent dose of previous patients.

In another aspect, a computer readable storage medium encoded with computer readable instructions, which, when executed by a processer, cause the processor to: obtain, in electronic format, demographics, current hemodynamics, and current vital signs of a current patient, obtain, in electronic format, stored demographics, hemodynamics, vital signs, and administered anesthetic agent doses of previous patients, and estimate an anesthetic agent dose for the current patient based on the demographics, hemodynamics and vital signs of the current patient and the demographics, hemodynamics, vital signs, and administered anesthetic agent dose of the previous patients and generate a signal indicative of the estimate. The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.

FIGURE 1 schematically illustrates a computing system with an initial dose estimator and a current dose assessor.

FIGURE 2 schematically illustrates an example of the initial dose estimator of

FIGURE 1.

FIGURE 3 schematically illustrates an example of the current dose assessor of

FIGURE 1.

FIGURE 4 illustrates an example method for estimating an initial anesthetic agent dose for a patient.

FIGURE 5 illustrates an example method for assessing a current anesthetic agent dose for a patient.

Initially referring to FIGURE 1, a clinical decision support (CDS) system 100 is schematically illustrated. The CDS system 100 is implemented via a computing system 102. Examples of the computing system 102 include, but are not limited to, a stand-alone or dedicated computer, an anesthesia apparatus, and/or other apparatus. The anesthesia apparatus is a device used by anesthesiologist, a nurse anesthetist, and/or an anesthesiologist assistant to support the administration of anesthesia to a patient.

The illustrated computing system 102 includes one or more hardware processors 104 (e.g., a central processing unit (CPU), a micro-processor (μ-processor), a controller, etc.) and computer readable storage medium 106 (which excludes transitory medium) such as physical memory encoded or embedded with computer readable

instructions. The instructions, when executed by the one or more processors 104 cause the one or more processors 104 to carry out functions, such as one or more functions described herein and/or other functions.

Additionally or alternatively, the one or more processors 104 execute instructions carried by transitory medium such as a signal or carrier wave. In FIGURE 1, the computer readable storage medium 106 is shown as a single element. However, it is to be appreciated that the computer readable storage medium 106 may include a plurality of separate hardware storage devices. The separate hardware storage devices include hardware storage devices local to the computing system 102, hardware storage devices external from the computing system 102, or hardware storage devices distributed between the computing system 102 and an external device(s).

Input/output (I/O) 108 receives information from one or more input devices 110 (e.g., a keyboard, a mouse, and the like) and/or conveys information to one or more output devices 112 (e.g., a display monitor, a printer, etc.) via a physical-mechanical and/or wireless interface. The I/O 108 is also configured to exchange data (in electronic format) with one or more apparatuses such as at least one physiologic parameter monitor apparatus 114, an anesthesia injector 116, and/or other device.

A suitable physiologic parameter monitor apparatus 114 senses and provides one or more of hemodynamics and/or vital signs such as central venous pressure (CVP), pulmonary artery pressure (e.g., systolic, diastolic, and/or mean), heart rate, Sao2 (arterial oxygen saturation), respiration, etc. A suitable anesthesia injector 116 administers anesthetic agents. The anesthesia injector 116 is part of an anesthetic machine, a stand-alone device, the computing system 102, and/or other device.

The I/O 108 is also configured to exchange data (in electronic format) with one or more data repositories 118. Examples of data repositories 118 include a hospital information system (HIS), an electronic medical record (EMR), a database, a server, an imaging system, a computer and/or other data repository. The data can be transferred via in formats such as Health Level 7 (HL7) and/or other formats. The information in the data repositories 118 includes demographics (current and previous patients), hemodynamics and/or vital signs of the previous patients, anesthetic doses administered to the previous patients, and/or other information.

The illustrated computer readable storage medium 106 stores software applications, software modules, and/or data. In the illustrated example, the computer readable storage medium 106 at least stores computer readable instructions for an initial dose estimator 120 and computer readable instructions for a current dose assessor 122. Both process data received over the I/O 108.

As described in greater detail below, in one non-limiting instance, the one or more processors 104, in response to executing the instructions of the initial dose estimator 120, estimates a dose of an anesthetic agent for a patient by determining a most likely dose based on current hemodynamics, vital signs and demographics of the current patient and stored hemodynamics, vital signs, demographics, and administered anesthetic agent dose for other patients previously under the same anesthetic agent. The one or more processors 104, in response to executing the instructions of the current dose assessor 122, additionally or alternatively assesses a current a dose of the anesthetic agent during a procedure based on current hemodynamics, vital signs and demographics of the patient and a most likely dose determined through the hemodynamics, vital signs, demographics, and administered anesthetic agent dose for other patients previously under the same anesthetic agent. This includes determining a current depth of anesthesia metric for the current patient under the anesthetic agent from such information.

In one non-limiting instance, the estimated dose and/or the current depth of anesthesia are visually displayed via a display of the output devices 110 and provided to an operator with information to mitigate potential risks from over and/or under dose.

Additionally or alternatively, the estimated dose and/or the current depth of anesthesia is conveyed, in electronic format, to the anesthesia injector 116 and/or anesthetic machine and sets and/or adjusts an anesthetic agent dose delivery parameter.

FIGURE 2 schematically illustrates a non-limiting example of the initial dose estimator 120. In this example, the initial dose estimator 120 estimates a dose of an anesthetic agent for the patient by determining the most likely dose for the patient, given the current hemodynamics and/or vital signs of the current patients along with the demographics of the patient and the hemodynamics, vital signs, demographics, and anesthetic agent dose administered to previous patients.

The current hemodynamics and/or vital signs of the patients are obtained from the at least one physiologic parameter monitor apparatus 114 (FIGURE 1). The

demographics of the patient are obtained from the one or more data repositories 118

(FIGURE 1). The hemodynamics, vital signs, demographics, and anesthetic agent dose administered to other patients are obtained from the one or more data repositories 118. Some or all of this information can alternatively be entered manually via the one or more input devices 110 (FIGURE 1).

In one instance, the initial dose estimator 120 estimates the anesthetic agent dose based on the likelihood function of EQUATION 1 :

EQUATION 1 :

. (. , /„ = ..[† f, ' » %« s/) , where P is a likelihood, or a most likely anesthetic agent dose ...(e.g., in units of milliliters per hour, or ml/hr, etc.), given input hemodynamics and vital signs (Vars) and demographics (Demogs). EQUATION 1 can be implemented using a classifier such as Bayesian classifier. In one example, the Bayesian classifier employs a Na,ve Bayes classification algorithm to identify the most likely anesthetic agent dose for the observed hemodynamics, vital signs, and demographics.

The output of the initial dose estimator 120 is a signal that indicates the estimated anesthetic agent dose. The signal is conveyed to a display of the output devices 112 (FIGURE 1) and/or other device, which displays the estimated anesthetic agent dose using alphanumeric characters. This information provides the anesthesiologist with information that can be used to determine the initial anesthetic agent dose to administer to a patient for a procedure. In one instance, the signal is also conveyed to the anesthesia injector 116 and/or an anesthetic machine to set, in connection with operator confirmation and/or validation, to set one or more parameters (e.g., agent delivery parameters) of the anesthesia injector 116 and/or anesthetic machine.

FIGURE 3 schematically illustrates a non-limiting example of the current dose assessor 122. In this example, the current dose assessor 122 assesses a current anesthetic agent dose provided to the patient based on the current hemodynamics, vital signs,

demographics, and anesthetic agent dose and a most likely dose determined through the hemodynamics, vitals, demographics, and anesthetic agent dose information for the other patients previously under the same anesthesia.

The current hemodynamics, vital signs, and anesthetic agent dose of the patients are obtained from the at least one physiologic parameter monitor apparatus 114 (FIGURE 1) and anesthesia injector (FIGURE 1), which can be part of an anesthetic machine. The demographics of the patient are obtained from the one or more data repositories 118 (FIGURE 1). The hemodynamics, vital signs, demographics, and anesthetic agent dose administered to other patients are obtained from the one or more data repositories 118. Some or all of this information can alternatively be entered manually via the one or more input devices 110 (FIGURE 1).

In one instance, the current dose assessor 122 assesses the current anesthetic agent dose based on EQUATION 2:

EQUATION 2:

— ((*. ., //.„. = = ..|.tr/,-„%* s/) .

/„· ^■■∑ · , /„ where · , /„ _< CE . is the current dose of the patient, · , /„■ - is the maximum dose

administered to a patient, · , /„■ ··. is the maximum dose administered to a patient, and

· ( · , /„ = . .|.††^" /, ·„%q S/) is the most likely anesthetic agent dose. As discussed herein at least in connection with FIGURE 2, P() can be determined using a classifier such as Bayesian classifier employing a Na,ve Bayes classification algorithm.

Generally, EQUATION 2 compares the offset between the current anesthetic agent dose and the most likely anesthetic agent dose, normalized to the total possible range of anesthetic agent dose, which provides a signed relative offset. The sign corresponds to over anesthetized or under anesthetized, meaning low or high depth of anesthesia. The range is between - 1 to 1, where /- l„means no depth of anesthesia and /l„means excessive or over depth of anesthesia, j0„is the desired depth of anesthesia.

The output of the current dose assessor 122 is a signal that indicates the depth of anesthesia for the current anesthetic agent dose. The signal is conveyed to a display of the output devices 112 (FIGURE 1) and/or other device, which displays the depth of anesthesia metric using alphanumeric characters. This information provides the anesthesiologist with information that can be used to determine, maintain and/or adjust the anesthetic agent dose administered to a patient during a procedure. In one instance, the signal is conveyed to the anesthetic injector 116 and/or anesthetic machine to adjust, in connection with operator confirmation and/or validation, one or more parameters (e.g., agent delivery parameters) of the anesthesia injector 116 and/or anesthetic machine.

It is to be appreciated that the ordering of the acts of these methods is not limiting. As such, other orderings are contemplated herein. In addition, one or more acts may be omitted and/or one or more additional acts may be included.

At 402, demographics of a current patient are obtained.

At 404, current hemodynamics of the current patient are obtained.

At 406, current vital signs of the current patient are obtained.

At 408, stored demographics of previous patients are obtained.

At 410, stored hemodynamics of the previous patients are obtained.

At 412, stored vital signs of the previous patients are obtained.

At 414, stored administered anesthetic agent doses of the previous patients are obtained. At 416, an estimated anesthetic agent dose for the patient is determined based on the demographics, hemodynamics and vital signs of the patient and the demographics, hemodynamics, vital signs, and anesthetic agent dose of the other patients, as describe herein and/or otherwise.

At 418, the estimated anesthetic agent dose is displayed via a display monitor and used to set initial anesthetic agent dose delivery parameters of an anesthesia injector and/or an anesthetic machine.

The above acts may be implemented by way of computer readable instructions, encoded or embedded on computer readable storage medium, which, when executed by a computer processor cause the processor to carry out the described acts. Additionally or alternatively, at least one of the computer readable instructions is carried by a signal, carrier wave and other transitory medium and implemented by the computer processor.

At 502, demographics of a current patient are obtained.

At 504, current hemodynamics of the current patient are obtained.

At 506, current vital signs of the current patient are obtained.

At 508, stored demographics of previous patients are obtained.

At 510, stored hemodynamics of the previous patients are obtained.

At 512, stored vital signs of the previous patients are obtained.

At 514, stored administered anesthetic agent doses of the previous patients are obtained.

At 516, a most likely anesthetic agent dose for the patient is determined based on the demographics, hemodynamics and vital signs of the patient and the

demographics, hemodynamics, vital signs, and anesthetic agent dose of the other patients, as describe herein and/or otherwise.

At 518, a current anesthetic agent dose of the current patient is obtained.

At 520, the current anesthetic agent dose is compared with the most likely anesthetic agent dose, and a result of the comparison indicates whether the current

anesthetic agent dose is greater than, about the same, or less than the most likely anesthetic agent dose. At 522, the result is displayed via a display monitor and used to adjust anesthetic agent dose delivery parameters of an anesthesia injector and/or an anesthetic machine in response to the result indicating the current anesthetic agent dose is greater than or less than the most likely anesthetic agent dose.

For example, where the depth of anesthesia metric has a numerical value in a range from negative one to one, where a value of negative one means no depth of anesthesia, of one means excessive depth of anesthesia, and of zero means desired depth of anesthesia, the current anesthetic agent dos is increased in response to the depth of anesthesia metric value being a range of negative one to approximately zero, decreased in response to the depth of anesthesia metric value being a range of one to approximately zero, and maintained in response to the value being approximately zero.

The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

CLAIMS:

1. A method, comprising:

obtaining, in electronic format, demographics, current hemodynamics, and current vital signs of a current patient;

obtaining, in electronic format, stored demographics, hemodynamics, vital signs, and administered anesthetic agent doses of previous patients; and

estimating an anesthetic agent dose for the current patient based on the demographics, hemodynamics and vital signs of the current patient and the demographics, hemodynamics, vital signs, and administered anesthetic agent dose of the previous patients and generating a signal indicative of the estimate.

2. The method of claim 1, further comprising:

setting an initial anesthetic agent dose delivery parameter based on the signal.

3. The method of any of claims 1 to 2, further comprising:

conveying the signal to an anesthetic agent dose delivery device; and setting the initial anesthetic agent dose delivery parameter for the anesthetic agent dose delivery device.

4. The method of any of claims 1 to 4, further comprising:

visually displaying the estimated anesthetic agent dose through a display monitor using alphanumeric characters.

5. The method of any of claims 1 to 4, further comprising:

computing the estimated anesthetic agent dose with a Bayesian classifier.

6. The method of any of claims 1 to 5, further comprising:

obtaining, in electronic format, a current anesthetic agent dose for the current patient;

comparing the current anesthetic agent dose with the estimated anesthetic agent dose;

generating a depth of anesthesia metric based on a result of the comparison; and

changing the current anesthetic agent dose to a next anesthetic agent dose in response to the depth of anesthesia metric.

7. The method of claim 6, further comprising:

computing the depth of anesthesia metric by determining a difference between the current anesthetic agent dose with the estimated anesthetic agent dose, normalized by a range from a minimum administered anesthetic agent dose to a maximum administered anesthetic agent dose.

8. The method of claim 7, wherein the depth of anesthesia metric has a numerical value in a range from negative one to one.

9. The method of claim 8, wherein a depth of anesthesia metric value of negative one means no depth of anesthesia, of one means excessive depth of anesthesia, and of zero means desired depth of anesthesia.

10. The method of any of claims 7 to 9, further comprising:

visually displaying the depth of anesthesia metric using alphanumeric characters.

11. The method of any of claims 7 to 10, further comprising:

conveying the signal to a device; and

adjusting the anesthetic agent dose delivery parameter of the device based on the depth of anesthesia metric value.

12. The method of any of claims 7 to 11, further comprising:

increasing an anesthetic agent dose delivery parameter in response to the depth of anesthesia metric value being a range of negative one to approximately zero.

13. The method of any of claims 7 to 11, further comprising:

decreasing an anesthetic agent dose delivery parameter in response to the depth of anesthesia metric value being a range of one to approximately zero.

14. The method of any of claims 7 to 11, further comprising:

maintaining a current anesthetic agent dose delivery parameter in response to the depth of anesthesia metric value being approximately zero.

15. A system (100), comprising:

a computing system (102), including:

at least one computer processor (104); and

computer readable storage medium (106) encoded with computer readable instructions for an initial dose estimator (118),

wherein, the at least one computer processor, in response to executing instructions of the initial dose estimator, estimates an anesthetic agent dose for a current patient based on demographics, current hemodynamics and current vital signs of the current patient and demographics, hemodynamics, vital signs, and administered anesthetic agent dose of previous patients.

16. The system of claim 15, wherein the at least one computer processor, in response to executing the instructions, sets an initial anesthetic agent dose delivery parameter based on the estimated anesthetic agent dose.

17. The system of any of claims 15 to 16, wherein the computer readable storage medium are further encoded with computer readable instructions for a current dose assessor (120), wherein the at least one computer processor, in response to executing the instructions for the current dose assessor, computes a depth of anesthesia based on a current anesthetic agent dose and a most likely anesthetic agent dose.

18. The system of claim 17, further comprising:

calculating the most likely anesthetic agent dose based on the demographics, the current hemodynamics and the current vital signs of the current patient and the demographics, the hemodynamics, the vital signs, and the administered anesthetic agent dose of previous patients.

19. The system of claim 18, wherein the at least one computer processor, in response to executing the instructions, adjusts the anesthetic agent dose delivery parameter based on the depth of anesthesia.

20. A computer readable storage medium encoded with computer readable instructions, which, when executed by a processer, cause the processor to:

obtain, in electronic format, demographics, current hemodynamics, and current vital signs of a current patient;

obtain, in electronic format, stored demographics, hemodynamics, vital signs, and administered anesthetic agent doses of previous patients; and

estimate an anesthetic agent dose for the current patient based on the demographics, hemodynamics and vital signs of the current patient and the demographics, hemodynamics, vital signs, and administered anesthetic agent dose of the previous patients and generate a signal indicative of the estimate.