A Tiva & Moni-Awarenes

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Clinical MonitoringClinical Monitoring Standard ASA recommended monitoring plus as per requirement ofStandard ASA recommended monitoring plus as per requirement of

surgery/ individual patient.surgery/ individual patient. MONITORSMONITORS--ECG , PULSE OXYMETRY,ECG , PULSE OXYMETRY,NIBP, ETCO2, TEMPNIBP, ETCO2, TEMP

SUBJECTIVE METHOD:SUBJECTIVE METHOD:1}AUTONOMIC RESPONSE1}AUTONOMIC RESPONSE--hemodynamic changes, lacrimation,hemodynamic changes, lacrimation,

sweating, pupillary dilatationsweating, pupillary dilatation2}ISOLATED FOREARM TECHNIQUE2}ISOLATED FOREARM TECHNIQUE--


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Short Coming of ClinicalShort Coming of ClinicalMonitoringMonitoring

Clinical assessment of anaesthetic depth hasClinical assessment of anaesthetic depth hasbecome more challenging because IVbecome more challenging because IVanaesthetic techniques involve combination ofanaesthetic techniques involve combination ofhypnotics, Opioids, muscle relaxants andhypnotics, Opioids, muscle relaxants andadjuvant drugs.adjuvant drugs.

The interaction between these drugs result inThe interaction between these drugs result inadditive, supra additive, infraadditive, supra additive, infra--additive, or evenadditive, or evenantagonist effects making clinical monitoringantagonist effects making clinical monitoringalone unreliable leading to the chances ofalone unreliable leading to the chances of

Awareness or Delayed awakeningAwareness or Delayed awakening


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Special MonitoringSpecial Monitoring

Two simple noninvasive monitor to measureTwo simple noninvasive monitor to measuredepth on anaesthesia could be:depth on anaesthesia could be: EEG & DERIVED INDICES EEG & DERIVED INDICES

1. Bispectral index(BIS)1. Bispectral index(BIS)

2.Entropy2.Entropy3.Patient State Index (PSI)3.Patient State Index (PSI)4.Narcotrend4.Narcotrend5.5.Cerebral State IndexCerebral State Index

6.SNAP index6.SNAP index

EVOKED POTENTIALS.EVOKED POTENTIALS.1.MLAEP1.MLAEP-- AEP indexAEP index


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e n ons o wareness ane n ons o wareness anMemoryMemory

AwarenessAwarenessPostoperative recall of eventsPostoperative recall of eventsoccurring during general anesthesiaoccurring during general anesthesia ..

Amnesic wakefulnessAmnesic wakefulnessResponsiveness duringResponsiveness duringgeneral anesthesia without postoperative recallgeneral anesthesia without postoperative recall

DreamingDreamingAny experience (excluding awareness)Any experience (excluding awareness)

that patients are able to recall postoperatively thatthat patients are able to recall postoperatively thatthey think occurred during general anesthesia andthey think occurred during general anesthesia andthat they believe is dreamingthat they believe is dreaming..

Explicit memoryExplicit memoryConscious recollection ofConscious recollection ofprevious experiences (awareness is evidence ofprevious experiences (awareness is evidence ofexplicit memory)explicit memory)

Implicit memoryImplicit memoryChanges in performance orChanges in performance orbehavior that are produced by previous experiencesbehavior that are produced by previous experiencesbut without any conscious recollection of thosebut without any conscious recollection of thoseexperiences (unconscious memory formationexperiences (unconscious memory formationduring general anesthesia)during general anesthesia)..


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High Risk Patient CharacteristicsHigh Risk Patient Characteristics

Substance use or abuse

Limited hemodynamic reserve

ASA IV V

Previous episode of intraoperative awareness

Chronic pain patients Younger age

Tobacco smoking


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High Risk Anesthetic TechniquesHigh Risk Anesthetic Techniques

Reduced anesthetic doses in presenceReduced anesthetic doses in presence

of paralysisof paralysis

Total intravenous anesthesiaTotal intravenous anesthesia

Nitrous oxideNitrous oxide--opioid anesthesiaopioid anesthesia

Rapid sequence inductionRapid sequence induction


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TIVA and AwarenessTIVA and Awareness

TIVATIVA independent high risk for awarenessindependent high risk for awareness

TIVA recipe: Propofol/opioid +/TIVA recipe: Propofol/opioid +/-- ketamineketamine

Ketamine is controversial since Ketamine (asKetamine is controversial since Ketamine (aswell as Etomidate) enhance both SSEPs andwell as Etomidate) enhance both SSEPs andMEPsMEPs

Wake up test (rarely done anymore!)Wake up test (rarely done anymore!)

BIS monitoringBIS monitoring


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RReducing risk of awarenesseducing risk of awareness

Pre operative amnesticsPre operative amnestics

Deeper anesthesia during intubationDeeper anesthesia during intubation

Appropriate use of narcotics to prevent painAppropriate use of narcotics to prevent pain separateseparaterecall of events from painrecall of events from pain

Less profound muscle relaxationLess profound muscle relaxation

Appropriate considerations for substanceAppropriate considerations for substance--tolerant patientstolerant patients Maintain accuracy of anesthesia delivery systemsMaintain accuracy of anesthesia delivery systems

Brain monitoringBrain monitoring

Better OR decorumBetter OR decorum less talking ,loud music at times ofless talking ,loud music at times ofexpected light anesthesiaexpected light anesthesia

Post op review and counselingPost op review and counseling


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EEGmonitoring limitations:EEGmonitoring limitations:

unaffected by nitrous oxide.

Unreliable with ketamine use.

Sensitive to Beta- blockers, atropine

Hypothermia, hypoglycemia, cns diseases can

affect the reading

5-10% of normal population has congenitally

low-voltage EEG

Subject to artifact from other electrical

equipment in the OR.

Does not predict movement


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Awake (Awake (EE))

DrowsyDrowsy

Light GALight GA

DeeperDeeper

GA (GA (HH))

BurstBurst

suppressionsuppression

Spindle

Burst


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EEG analysisEEG analysis

3 predominant methods3 predominant methods

time domain analysis methodstime domain analysis methods: analyse the: analyse thechanges in the EEG signal in respect tochanges in the EEG signal in respect to timetime,,

frequency domain analysis methodsfrequency domain analysis methods: analyse: analysethe changes in the EEG potentials in respect tothe changes in the EEG potentials in respect tofrequencyfrequency

bispectral analysis methodsbispectral analysis methods: analyse EEG: analyse EEG

signal in respect to itssignal in respect to its amplitudeamplitude, its, its frequencyfrequencyand itsand its correlation between phase angle and thecorrelation between phase angle and thefrequency rangefrequency range of the included waves.of the included waves.


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Bispectral Index (BIS)Bispectral Index (BIS)


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BIS Range GuidelinesBIS Range Guidelines

Titration of sedatives to BIS ranges should be dependent upon the individual goals

for sedation that have been established for each patient.

These goals and associated BIS ranges may vary over time, in the context of patient

status and treatment plan.


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Bispectral Index (BIS)Bispectral Index (BIS)

Proprietary algorithm converts a single channel of

frontal EEG into an index of hypnotic level

BIS values scaled from 0-100

Specific range of 40-60 = low probability of

consciousness underGA


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EntropyEntropy


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ENTROPYENTROPY

Based on acquisition and processing of rawBased on acquisition and processing of rawEEG and FEMG signalsEEG and FEMG signals

describes the irregularity, complexity, ordescribes the irregularity, complexity, orunpredictability characteristics of a signal.unpredictability characteristics of a signal.

EEG recordings change from irregular toEEG recordings change from irregular tomore regular patterns when anaesthesiamore regular patterns when anaesthesiadeepens.deepens.


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EntropyEntropy

Describes the irregularity, complexity orDescribes the irregularity, complexity or

unpredictable characteristics of a signalunpredictable characteristics of a signal

Single sine wave represents a completelySingle sine wave represents a completelypredictable signal (entropy = 0)predictable signal (entropy = 0)

Noise represents entropy = 1Noise represents entropy = 1

State entropy: cortical state (hypnosis)State entropy: cortical state (hypnosis) Response entropy: EMG activity from inadequateResponse entropy: EMG activity from inadequate

analgesiaanalgesia


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Entropy and AnaesthesiaEntropy and Anaesthesia

Awake brainAwake brain=High Entropy =>=High Entropy =>FreedomFreedomBoiling BrainBoiling Brain

there are many availablethere are many available microstatesmicrostates energy spreads out easily spatial coherence orenergy spreads out easily spatial coherence or

decoherence?decoherence? accurate & fast cortical information processingaccurate & fast cortical information processing

Comatose brainComatose brain= Low Entropy =>= Low Entropy =>PrisonPrison

Frozen BrainFrozen Brain few microstatesfew microstates slow inaccurate information processingslow inaccurate information processing


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ENTROPY AND ANAESTHESIAENTROPY AND ANAESTHESIA

Awake

0.90(0.03)

Loss-of-Consciousness

0.69(0.06)

Deep GA

0.74(0.02)

Increasing Anaesthetic Effect


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ower pec rumower pec rum -- ererPatientPatient

Spectral Entropy = 0.9


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EEG & Power SpectrumEEG & Power Spectrum -- AnaesthetisedAnaesthetised

Spectral Entropy = 0.4


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State/ Response entropyState/ Response entropy State entropy (SE) is an index ranging from 0 to 91State entropy (SE) is an index ranging from 0 to 91

(awake)(awake)---- the frequency range from 0.8 to 32 Hz,the frequency range from 0.8 to 32 Hz,reflecting the cortical state of the patient.reflecting the cortical state of the patient.

Response entropy (RE) is an index ranging from 0 toResponse entropy (RE) is an index ranging from 0 to100 (awake)100 (awake)----a frequency range from 0.8 to 47 Hz,a frequency range from 0.8 to 47 Hz,containing the higher EMGcontaining the higher EMG--dominated frequencies, anddominated frequencies, andwill thus also respond to the increased EMG activitywill thus also respond to the increased EMG activityresulting from inadequate analgesia.resulting from inadequate analgesia.

Vakkuri A et al have been reported that entropyVakkuri A et al have been reported that entropy

monitoring assists better titration of propofol especiallymonitoring assists better titration of propofol especiallyduring the last part of the procedures, as indicated byduring the last part of the procedures, as indicated byhigher entropy values, decreased consumption ofhigher entropy values, decreased consumption ofpropofol, and shorter recovery times in the entropypropofol, and shorter recovery times in the entropygroup.group.


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PSI(PATIENT STATE INDEX)PSI(PATIENT STATE INDEX) The PSI monitor is based on a quantitative analysis ofThe PSI monitor is based on a quantitative analysis of

thethe ,, ,, , and, and frequency bands as revealed by fastfrequency bands as revealed by fastFourier transformation, recorded from anterior andFourier transformation, recorded from anterior andposterior scalp sites, as input to a multivariate algorithmposterior scalp sites, as input to a multivariate algorithmthat quantifies the most probable level of hypnosis.that quantifies the most probable level of hypnosis.

44--channel EEGchannel EEG

Patient State Analyzer: selfPatient State Analyzer: self--norming techniquenorming techniquevalues: 0 to 100values: 0 to 100 faster emergence and recovery from propofolfaster emergence and recovery from propofol--alfentanilalfentanil--

nitrous oxide anesthesia, with modest decrease in thenitrous oxide anesthesia, with modest decrease in theamount of propofol delivered.amount of propofol delivered.

useful in assessing patients receiving a combination ofuseful in assessing patients receiving a combination ofpropofol and sufentanil.propofol and sufentanil.

the influence of muscle activity: uncertain.the influence of muscle activity: uncertain. less interference with the PSI readingsless interference with the PSI readings duringduring

electrocautery useelectrocautery use


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PSI VALUESPSI VALUES


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AUDITORY EVOKED POTENTIALSAUDITORY EVOKED POTENTIALS The AEP is defined as the passage of electrical activity from theThe AEP is defined as the passage of electrical activity from the

cochlea to the cortex, which produces a waveform consisting of 15cochlea to the cortex, which produces a waveform consisting of 15waves. The waveform can be divided into three parts:waves. The waveform can be divided into three parts:

Brainstem Auditory Evoked Potential (BAEP) from brainstem,Brainstem Auditory Evoked Potential (BAEP) from brainstem, Middle Latency Auditory Evoked Potential (MLAEP) from medialMiddle Latency Auditory Evoked Potential (MLAEP) from medial

geniculate body and the primary auditory cortex andgeniculate body and the primary auditory cortex and

Long Latency Auditory Evoked Potential (LLAEP) from frontal cortexLong Latency Auditory Evoked Potential (LLAEP) from frontal cortexand association areas.and association areas.

Measures the brains reaction to acoustic stimuli.Measures the brains reaction to acoustic stimuli. Hearing,a natural choice for measuring patient consciousness underHearing,a natural choice for measuring patient consciousness under

anaestheticanaesthetic The brainstem response is relatively insensitive to anaesthetics,The brainstem response is relatively insensitive to anaesthetics,

whereas early cortical responses (MLAEPs), change predictably withwhereas early cortical responses (MLAEPs), change predictably withincreasing concentrations of both volatile and intravenousincreasing concentrations of both volatile and intravenousanaestheticsanaesthetics


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AEP monitoringAEP monitoring From a mathematical analysis of the AEP waveform, the deviceFrom a mathematical analysis of the AEP waveform, the devicegenerates an AEP index {from 0generates an AEP index {from 0--100} or A100} or A--line ARX Index(AAI){0line ARX Index(AAI){0

60 range }60 range } ReRe--usable headphones/earphones deliver the active stimulation,usable headphones/earphones deliver the active stimulation,

costcost--effective disposable surface electrodes are used to measure theeffective disposable surface electrodes are used to measure theAEP.AEP.

The AAI index is calculated in the 20The AAI index is calculated in the 2080 ms window of the AEP and80 ms window of the AEP andlatency and amplitude changes in the AEP are weighted equally.latency and amplitude changes in the AEP are weighted equally. The typical AEP response to increasing anaesthetic concentrations isThe typical AEP response to increasing anaesthetic concentrations is

increased latency and decreased amplitude of the various waveformincreased latency and decreased amplitude of the various waveformcomponents.components.

AAI responded to LMA insertion or surgical incision, but not the BIS,AAI responded to LMA insertion or surgical incision, but not the BIS,and the AAI had smaller variations.and the AAI had smaller variations.

AAI recovered faster from the disturbance by electrocautery thanAAI recovered faster from the disturbance by electrocautery thantheBIS and the AAI may be a more sensitive and useful detector oftheBIS and the AAI may be a more sensitive and useful detector ofarousal than the BIS.arousal than the BIS.


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AEP monitoringAEP monitoring--

AA--line ARX Index(AAI)line ARX Index(AAI)


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NARCOTRENDNARCOTREND

Frontal EEG monitor to measure the depth of anaesthesiaFrontal EEG monitor to measure the depth of anaesthesia recorded by standard ECG electrodes for singlerecorded by standard ECG electrodes for single-- and doubleand double--channelchannel

registration.registration. After artifact exclusion and Fourier transformation EEG data classifiedAfter artifact exclusion and Fourier transformation EEG data classified

as:as:

A(awake), B(sedated), C (light anaesthesia), D (generalA(awake), B(sedated), C (light anaesthesia), D (generalanaesthesia), E (general anaesthesia with deep hypnosis), Fanaesthesia), E (general anaesthesia with deep hypnosis), F(general anaesthesia with increasing burst suppression).(general anaesthesia with increasing burst suppression).

14 possible sub14 possible sub--stages: A, B0stages: A, B02, C02, C02, D02, D02, E02, E01, and F01, and F011 In the most recent version it is translated into a numerical scalingIn the most recent version it is translated into a numerical scaling

index system which called as the Narcotrendindex.index system which called as the Narcotrendindex.

This is scaled quantitatively similar to BIS scale viz. 0 (deeplyThis is scaled quantitatively similar to BIS scale viz. 0 (deeplyanaesthetized) to 100(awake).anaesthetized) to 100(awake).


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NARCOTRENDNARCOTREND

No clinical trials or other comparativeNo clinical trials or other comparativestudies were found that examine thestudies were found that examine theimpact of Narcotrendmonitoring on theimpact of Narcotrendmonitoring on the

incidence of intraoperative awareness.incidence of intraoperative awareness.found to reduce propofol consumptionfound to reduce propofol consumption

compared to a conventional clinical practice.compared to a conventional clinical practice.

unable to differentiate reliably betweenunable to differentiate reliably betweenconscious and unconscious patients duringconscious and unconscious patients duringgeneral anaesthesia when neuromusculargeneral anaesthesia when neuromuscularblocking agentsare usedblocking agentsare used


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No clinical trials or other comparativeNo clinical trials or other comparativestudies were found that examine thestudies were found that examine theimpact of Narcotrendmonitoring on theimpact of Narcotrendmonitoring on theincidence of intraoperative awareness.incidence of intraoperative awareness.

found to reduce propofol consumptionfound to reduce propofol consumptioncompared to a conventional clinicalcompared to a conventional clinicalpractice.practice.unable to differentiate reliably betweenunable to differentiate reliably betweenconscious and unconscious patients duringconscious and unconscious patients duringgeneral anaesthesia when neuromusculargeneral anaesthesia when neuromuscular

blocking agentsare usedblocking agentsare used


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SNAP indexSNAP index


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SNAP indexSNAP index

Raw EEG signals used by unique algorithm, which analysesRaw EEG signals used by unique algorithm, which analysesboth high(80both high(80--420 Hz) and low (0420 Hz) and low (0--20 Hz) frequency20 Hz) frequencycomponents of the signal and results ranges from 100components of the signal and results ranges from 100(arbitrarily representing the fully awake state) to 0. This is(arbitrarily representing the fully awake state) to 0. This istermed the SNAP index.termed the SNAP index.

SNAP index returns to baseline before awakening,SNAP index returns to baseline before awakening,whereas the BIS index remains below baseline atwhereas the BIS index remains below baseline at

awakening, suggesting that the SNAP index may be moreawakening, suggesting that the SNAP index may be moresensitive to unintentional awareness.sensitive to unintentional awareness.

there is no evidence that SNAP is superior to others inthere is no evidence that SNAP is superior to others ingenerating more specific information about depth ofgenerating more specific information about depth ofsedationsedation

Still being researched.Still being researched.


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Cerebral State Monitor/CerebralCerebral State Monitor/CerebralState Index (CSI)State Index (CSI)

The EEG waveform is derived from the signal recorded between theThe EEG waveform is derived from the signal recorded between thefrontal and mastoid electrodes. The frequency content is 2frontal and mastoid electrodes. The frequency content is 2--35 Hz.35 Hz.

CSI is based on the analysis of the frequency content of the EEGCSI is based on the analysis of the frequency content of the EEGsignal. It analyses the frequency shifts that take place in the EEGsignal. It analyses the frequency shifts that take place in the EEGsignal as the level of consciousness changes.signal as the level of consciousness changes.

The energy of the EEG is evaluated in specific frequency bands. TheseThe energy of the EEG is evaluated in specific frequency bands. Theseare used to define two energy ratios calledare used to define two energy ratios called andand .. Both of these show a shift in energy content from the higher to theBoth of these show a shift in energy content from the higher to the

lower frequencies during anaesthesia. The relationship between theselower frequencies during anaesthesia. The relationship between thesequantities is also analyzed as a separate parameter (quantities is also analyzed as a separate parameter (--).).

The monitor incorporates an EMG filter.The monitor incorporates an EMG filter.


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Cerebral State Monitor/CerebralCerebral State Monitor/CerebralState Index (CSI)State Index (CSI)

The monitor also evaluates the amount of instantaneous burstThe monitor also evaluates the amount of instantaneous burstsuppression (BS) in each thirtysuppression (BS) in each thirty--second period of the EEG.second period of the EEG.

The four parameters (The four parameters ( ratio,ratio, ratio,ratio, -- shift & BS) are used as inputshift & BS) are used as inputto a fuzzy logic classifier system that calculates the CSI.to a fuzzy logic classifier system that calculates the CSI.

The CSI is a unitThe CSI is a unit--less scale from 0 to 100,where 0 indicates a flat EEGless scale from 0 to 100,where 0 indicates a flat EEG

and 100 indicate EEG activity corresponding to the awake state. Theand 100 indicate EEG activity corresponding to the awake state. Therange of adequate anaesthesia is designed to be between 40 and 60.range of adequate anaesthesia is designed to be between 40 and 60. CSI detects well the graduated levels of propofol anaesthesia whenCSI detects well the graduated levels of propofol anaesthesia when

compared with the propofol effect site concentration and the OAAScompared with the propofol effect site concentration and the OAASscorescore

It behaves as other depth of anaesthesia monitors with a progressiveIt behaves as other depth of anaesthesia monitors with a progressivedecrease during propofol induction but loss of consciousness with N2Odecrease during propofol induction but loss of consciousness with N2Oresults no change in CSI.results no change in CSI.

No published literature was found for impact on intraoperativeNo published literature was found for impact on intraoperativeawareness.awareness.


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ASA Practice AdvisoryASA Practice Advisory

The decision to administer benzodiazepineThe decision to administer benzodiazepineprophylactically should be made on a caseprophylactically should be made on a case--byby--case basis for selected patientscase basis for selected patients

Intraoperative monitoring of depth of anesthesiaIntraoperative monitoring of depth of anesthesiashould rely on multiple modalities, includingshould rely on multiple modalities, including

clinical techniques and conventional monitoringclinical techniques and conventional monitoringsystems( ECG, BP, endsystems( ECG, BP, end--tidal gas analyzer)tidal gas analyzer)


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ASA Practice AdvisoryASA Practice Advisory

The decision to use a brain function monitorThe decision to use a brain function monitor

should be made on a caseshould be made on a case--byby--case basis.case basis.

Cautions!!!Cautions!!!

Maintaining low brain function monitor valuesMaintaining low brain function monitor values

in an attempt to prevent intraoperativein an attempt to prevent intraoperative

awareness may conflict with other anesthesiaawareness may conflict with other anesthesia

goals (preservation vital functions)goals (preservation vital functions)


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