Monitoring in TIVAMonitoring in TIVA

This can be done by:This can be done by:•Clinical Monitoring•Clinical Monitoring•Special Monitoring•Special Monitoring

Clinical MonitoringClinical Monitoring► Standard ASA recommended monitoring plus as per Standard ASA recommended monitoring plus as per

requirement of surgery/ individual patient.requirement of surgery/ individual patient. MONITORS-ECG , MONITORS-ECG , PULSE OXYMETRY, NIBP, ETCO2, TEMP PULSE OXYMETRY, NIBP, ETCO2, TEMP

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

lacrimation, sweating, pupillary dilatationlacrimation, sweating, pupillary dilatation2}ISOLATED FOREARM TECHNIQUE-2}ISOLATED FOREARM TECHNIQUE-

Short Coming of Clinical Short Coming of Clinical MonitoringMonitoring

Clinical assessment of anaesthetic depth has Clinical assessment of anaesthetic depth has become more challenging because IV become more challenging because IV anaesthetic techniques involve anaesthetic techniques involve combination of hypnotics, Opioids, muscle combination of hypnotics, Opioids, muscle relaxants and adjuvant drugs.relaxants and adjuvant drugs.

The interaction between these drugs result in The interaction between these drugs result in additive, supra additive, infra-additive, or additive, supra additive, infra-additive, or even antagonist effects making clinical even antagonist effects making clinical monitoring alone unreliable leading to the monitoring alone unreliable leading to the chances of chances of

““Awareness or Delayed awakening”Awareness or Delayed awakening”

Special MonitoringSpecial Monitoring

Two simple noninvasive monitor to measure Two simple noninvasive monitor to measure depth on anaesthesia could be:depth on anaesthesia could be:• • EEG & DERIVED INDICESEEG & DERIVED INDICES 1. Bispectral index(BIS)1. Bispectral index(BIS) 2.Entropy2.Entropy 3.Patient State Index (PSI)3.Patient State Index (PSI) 4.Narcotrend4.Narcotrend 5.5.Cerebral State IndexCerebral State Index 6.SNAP index6.SNAP index

••EVOKED POTENTIALS.EVOKED POTENTIALS. 1.MLAEP- AEP index1.MLAEP- AEP index

Definitions of Awareness and Definitions of Awareness and MemoryMemory

►      Awareness—Postoperative recall of events Awareness—Postoperative recall of events occurring during general anesthesia . occurring during general anesthesia . 

► Amnesic wakefulness—Responsiveness during Amnesic wakefulness—Responsiveness during general anesthesia without postoperative recallgeneral anesthesia without postoperative recall

►     Dreaming—Any experience (excluding Dreaming—Any experience (excluding awareness) that patients are able to recall awareness) that patients are able to recall postoperatively that they think occurred during postoperatively that they think occurred during general anesthesia and that they believe is general anesthesia and that they believe is dreamingdreaming..

►       Explicit memory—Conscious recollection of Explicit memory—Conscious recollection of previous experiences (“awareness” is evidence previous experiences (“awareness” is evidence of explicit memory)of explicit memory)

► Implicit memory—Changes in performance or Implicit memory—Changes in performance or behavior that are produced by previous behavior that are produced by previous experiences but without any conscious experiences but without any conscious recollection of those experiences (“unconscious recollection of those experiences (“unconscious memory formation” during general anesthesia)memory formation” during general anesthesia)..

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

High Risk Anesthetic TechniquesHigh Risk Anesthetic Techniques

Reduced anesthetic doses in presence Reduced anesthetic doses in presence of paralysisof paralysis

Total intravenous anesthesiaTotal intravenous anesthesia

Nitrous oxide-opioid anesthesiaNitrous oxide-opioid anesthesia

Rapid sequence inductionRapid sequence induction

TIVA and AwarenessTIVA and Awareness

►TIVA – independent high risk for awarenessTIVA – independent high risk for awareness►TIVA recipe: Propofol/opioid +/- ketamineTIVA recipe: Propofol/opioid +/- ketamine

Ketamine is controversial since Ketamine (as Ketamine is controversial since Ketamine (as well as Etomidate) enhance both SSEP’s and well as Etomidate) enhance both SSEP’s and MEP’s MEP’s

►Wake up test (rarely done anymore!)Wake up test (rarely done anymore!)►BIS monitoringBIS monitoring►Small bolus (eg, 1-2mg) of Midazolam Small bolus (eg, 1-2mg) of Midazolam

intraop (too much will affect monitoring!!)intraop (too much will affect monitoring!!)

10

SEA # 32 – RSEA # 32 – Reducing risk of educing risk of awarenessawareness

► Pre operative amnesticsPre operative amnestics► Deeper anesthesia during intubationDeeper anesthesia during intubation► Appropriate use of narcotics to prevent pain – Appropriate use of narcotics to prevent pain –

separate recall of events from painseparate recall of events from pain► Less profound muscle relaxationLess profound muscle relaxation► Appropriate considerations for substance-tolerant Appropriate considerations for substance-tolerant

patientspatients► Maintain accuracy of anesthesia delivery systemsMaintain accuracy of anesthesia delivery systems► Brain monitoringBrain monitoring► Better OR decorum – less talking and loud music at Better OR decorum – less talking and loud music at

times of expected light anesthesiatimes of expected light anesthesia► Post op review and counselingPost op review and counseling► Informed consent?Informed consent?

EEG monitoring limitations:EEG monitoring limitations:

Insensitive to nitrous oxide, ketamine, xenon Sensitive to Beta- blockers, muscle relaxants Hypothermia, hypoglycemia can affect the

reading 5-10% of normal population has congenitally low-voltage EEG Subject to artifact from other electrical

equipment in the OR.

Practical Problems with Practical Problems with EEG/BIS/Entropy…EEG/BIS/Entropy…

►AlgorithmicAlgorithmic Artifacts (diathermy, eye-Artifacts (diathermy, eye-

movements etc…)movements etc…) EMG and Burst SuppressionEMG and Burst Suppression

►InherentInherent Prediction of movement /MACPrediction of movement /MAC Other drugs… Other drugs… atropineatropine…… Disease…Disease…CNS… Systemic…CNS… Systemic…

Awake Awake (())

DrowsyDrowsy

Light GALight GA

Deeper Deeper GA (GA ())

Burst Burst suppressiosuppressionn

Spindle

Burst

EEG analysisEEG analysis

3 predominant methods3 predominant methods► time domain analysis methodstime domain analysis methods: analyse : analyse

the changes in the EEG signal in respect to the changes in the EEG signal in respect to timetime,,

► frequency domain analysis methodsfrequency domain analysis methods: : analyse the changes in the EEG potentials in analyse the changes in the EEG potentials in respect to respect to frequencyfrequency

► bispectral analysis methodsbispectral analysis methods: analyse EEG : analyse EEG signal in respect to its signal in respect to its amplitudeamplitude, its , its frequency frequency and its and its correlation between phase angle and correlation between phase angle and the frequency range the frequency range of the included waves.of the included waves.

Bispectral Index (BIS)Bispectral Index (BIS)

Bispectral IndexBispectral Index► BIS is a proprietary that converts a single channel of BIS is a proprietary that converts a single channel of

frontal EEG into an index of hypnotic level (BIS).frontal EEG into an index of hypnotic level (BIS).► To compute the BIS, several variables derived from the To compute the BIS, several variables derived from the

EEG time domain (burst-suppression analysis), EEG time domain (burst-suppression analysis), frequency domain (power spectrum, bispectrum: inter-frequency domain (power spectrum, bispectrum: inter-frequency phase relationships) are combined into a frequency phase relationships) are combined into a single index of hypnotic level.single index of hypnotic level.

► A multivariate logistic regression was used in offline A multivariate logistic regression was used in offline analysis and identified those features of the EEG analysis and identified those features of the EEG recordings that best correlated with clinical depth of recordings that best correlated with clinical depth of sedation/anaesthesia, and these were then fitted to a sedation/anaesthesia, and these were then fitted to a model. The resulting algorithm generates the BIS.model. The resulting algorithm generates the BIS.

► BIS model accounts for the nonlinear stages of EEG BIS model accounts for the nonlinear stages of EEG activity by allowing different parameters to dominate the activity by allowing different parameters to dominate the resulting BIS as the EEG changes its character with resulting BIS as the EEG changes its character with increasing plasma concentrations of various increasing plasma concentrations of various anaesthetics, resulting in a linear decrease in BIS.anaesthetics, resulting in a linear decrease in BIS.

► It is suggested that routine intraoperative events (e.g., It is suggested that routine intraoperative events (e.g., administration of depolarizing muscle relaxants, administration of depolarizing muscle relaxants, activation of electromagnetic equipment or devices, activation of electromagnetic equipment or devices, patient warming or planned hypothermia)may interfere patient warming or planned hypothermia)may interfere with BIS functioning.with BIS functioning.

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.

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 under GA

EntropyEntropy

ENTROPYENTROPY

►Based on acquisition and processing of Based on acquisition and processing of raw EEG and FEMG signalsraw EEG and FEMG signals

►describes the irregularity, complexity, describes the irregularity, complexity, or unpredictability characteristics of a or unpredictability characteristics of a signal. signal.

► EEG recordings change from irregular EEG recordings change from irregular to more regular patterns when to more regular patterns when anaesthesia deepens.anaesthesia deepens.

EntropyEntropy

Describes the irregularity, complexity or Describes the irregularity, complexity or unpredictable characteristics of a signalunpredictable characteristics of a signal

Single sine wave represents a completely Single sine wave represents a completely predictable 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 inadequate Response entropy: EMG activity from inadequate

analgesia analgesia

Entropy and AnaesthesiaEntropy and Anaesthesia

►Awake brainAwake brain = High Entropy => = High Entropy => ‘Freedom’ ‘Freedom’ ““Boiling Brain”Boiling Brain”

there are many available there are many available microstatesmicrostates energy spreads out easily spatial coherence energy spreads out easily spatial coherence

or decoherence?or decoherence? accurate & fast cortical information accurate & fast cortical information

processingprocessing

►Comatose brainComatose brain = Low Entropy = Low Entropy => ‘Prison’=> ‘Prison’

““Frozen BrainFrozen Brain”” few microstatesfew microstates slow inaccurate information processing slow inaccurate information processing

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

EEG & Power Spectrum - Alert EEG & Power Spectrum - Alert PatientPatient

Spectral Entropy = 0.9

EEG & Power Spectrum - EEG & Power Spectrum - AnaesthetisedAnaesthetised

Spectral Entropy = 0.4

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

91 (awake)-- the frequency range from 0.8 to 32 91 (awake)-- the frequency range from 0.8 to 32 Hz, reflecting the cortical state of the patient.Hz, reflecting the cortical state of the patient.

► Response entropy (RE) is an index ranging from Response entropy (RE) is an index ranging from 0 to 100 (awake)--a frequency range from 0.8 to 0 to 100 (awake)--a frequency range from 0.8 to 47 Hz, containing the higher EMG-dominated 47 Hz, containing the higher EMG-dominated frequencies, and will thus also respond to the frequencies, and will thus also respond to the increased EMG activity resulting from inadequate increased EMG activity resulting from inadequate analgesia.analgesia.

► Vakkuri A et al have been reported that entropy Vakkuri A et al have been reported that entropy monitoring assists better titration of propofol monitoring assists better titration of propofol especially during the last part of the procedures, especially during the last part of the procedures, as indicated by higher entropy values, decreased as indicated by higher entropy values, decreased consumption of propofol, and shorter recovery consumption of propofol, and shorter recovery times in the entropy group.times in the entropy group.

PSI(PATIENT STATE INDEX)PSI(PATIENT STATE INDEX)► The PSI monitor is based on a quantitative The PSI monitor is based on a quantitative

analysis of the α, β, Δ, and θ frequency bands as analysis of the α, β, Δ, and θ frequency bands as revealed by fast Fourier transformation, recorded revealed by fast Fourier transformation, recorded from anterior and posterior scalp sites, as input to from anterior and posterior scalp sites, as input to a multivariate algorithm that quantifies the most a multivariate algorithm that quantifies the most probable level of hypnosis.probable level of hypnosis.

► 4-channel EEG4-channel EEGPatient State Analyzer: self-norming techniquePatient State Analyzer: self-norming techniquevalues: 0 to 100values: 0 to 100► faster emergence and recovery from propofol-faster emergence and recovery from propofol-

alfentanil-nitrous oxide anesthesia, with modest alfentanil-nitrous oxide anesthesia, with modest decrease in the amount of propofol delivered.decrease in the amount of propofol delivered.

► useful in assessing patients receiving a useful in assessing patients receiving a combination of propofol and sufentanil.combination of 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 during during

electrocautery useelectrocautery use

PSI VALUESPSI VALUES

AUDITORY EVOKED AUDITORY EVOKED POTENTIALSPOTENTIALS

► The AEP is defined as the passage of electrical activity from The AEP is defined as the passage of electrical activity from the cochlea to the cortex, which produces a waveform the cochlea to the cortex, which produces a waveform consisting of 15 waves. The waveform can be divided into consisting of 15 waves. The waveform can be divided into three parts: three parts:

Brainstem Auditory Evoked Potential (BAEP) from Brainstem Auditory Evoked Potential (BAEP) from brainstem,brainstem,

Middle Latency Auditory Evoked Potential (MLAEP) from Middle Latency Auditory Evoked Potential (MLAEP) from medial geniculate body and the primary auditory cortex medial geniculate body and the primary auditory cortex and and

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

► Measures the brain’s reaction to acoustic stimuli.Measures the brain’s reaction to acoustic stimuli.► Hearing,a natural choice for measuring patient Hearing,a natural choice for measuring patient

consciousness under anaesthetic consciousness under anaesthetic ► The brainstem response is relatively insensitive to The brainstem response is relatively insensitive to

anaesthetics, whereas early cortical responses (MLAEPs), anaesthetics, whereas early cortical responses (MLAEPs), change predictably with increasing concentrations of both change predictably with increasing concentrations of both volatile and intravenous anaestheticsvolatile and intravenous anaesthetics

AEP monitoringAEP monitoring► From a mathematical analysis of the AEP waveform, the From a mathematical analysis of the AEP waveform, the

device generates an “AEP index” {from 0-100} or A-line device generates an “AEP index” {from 0-100} or A-line ARX Index(AAI){0–60 range }ARX Index(AAI){0–60 range }

► Re-usable headphones/earphones deliver the active Re-usable headphones/earphones deliver the active stimulation, cost-effective disposable surface electrodes are stimulation, cost-effective disposable surface electrodes are used to measure the AEP.used to measure the AEP.

► The AAI index is calculated in the 20–80 ms window of the The AAI index is calculated in the 20–80 ms window of the AEP and latency and amplitude changes in the AEP are AEP and latency and amplitude changes in the AEP are weighted equally. weighted equally.

► The typical AEP response to increasing anaesthetic The typical AEP response to increasing anaesthetic concentrations is increased latency and decreased concentrations is increased latency and decreased amplitude of the various waveform components.amplitude of the various waveform components.

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

► AAI recovered faster from the disturbance by AAI recovered faster from the disturbance by electrocautery than theBIS and the AAI may be a more electrocautery than theBIS and the AAI may be a more sensitive and useful detector of arousal than the BIS.sensitive and useful detector of arousal than the BIS.

AEP monitoring-AEP monitoring-A-line ARX Index(AAI)A-line ARX Index(AAI)

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

channel registration.channel registration.► After artifact exclusion and Fourier transformation EEG data After artifact exclusion and Fourier transformation EEG data

classified as:classified as: A(awake), B(sedated), C (light anaesthesia), D (general A(awake), B(sedated), C (light anaesthesia), D (general

anaesthesia), E (general anaesthesia with deep anaesthesia), E (general anaesthesia with deep hypnosis), F (general anaesthesia with increasing burst hypnosis), F (general anaesthesia with increasing burst suppression).suppression).

► 14 possible sub-stages: A, B0–2, C0–2, D0–2, E0–1, and F0–114 possible sub-stages: A, B0–2, C0–2, D0–2, E0–1, and F0–1► In the most recent version it is “translated” into a numerical In the most recent version it is “translated” into a numerical

scaling index system which called as the Narcotrend®index.scaling index system which called as the Narcotrend®index.► This is scaled quantitatively similar to BIS scale viz. 0 (deeply This is scaled quantitatively similar to BIS scale viz. 0 (deeply

anaesthetized) to 100(awake).anaesthetized) to 100(awake).

NARCOTRENDNARCOTREND►No clinical trials or other comparative No clinical trials or other comparative

studies were found that examine the studies were found that examine the impact of Narcotrend®monitoring on the impact of Narcotrend®monitoring on the incidence of intraoperative awareness.incidence of intraoperative awareness.

►found to reduce propofol consumptionfound to reduce propofol consumption

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

►unable to differentiate reliably between unable to differentiate reliably between conscious and unconscious patients conscious and unconscious patients during general anaesthesia when during general anaesthesia when neuromuscular blocking agentsare usedneuromuscular blocking agentsare used

SNAP indexSNAP index

SNAP indexSNAP index

► Raw EEG signals used by unique algorithm, which Raw EEG signals used by unique algorithm, which analyses both high(80-420 Hz) and low (0-20 Hz) analyses both high(80-420 Hz) and low (0-20 Hz) frequency components of the signal and results frequency components of the signal and results ranges from 100 (arbitrarily representing the fully ranges from 100 (arbitrarily representing the fully awake state)to 0. This is termed the SNAP index.awake state)to 0. This is 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 at whereas the BIS index remains below baseline at awakening, suggesting that the SNAP index may be awakening, suggesting that the SNAP index may be more sensitive to unintentional awareness.more sensitive to unintentional awareness.

► there is no evidence that SNAP is superior to others there is no evidence that SNAP is superior to others in generating more specific information about in generating more specific information about ‘depth of sedation’‘depth of sedation’

► Still being researched.Still being researched.

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

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

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

► The energy of the EEG is evaluated in specific frequency The energy of the EEG is evaluated in specific frequency bands. These are used to define two energy ratios called bands. These are used to define two energy ratios called αα and and ββ. .

► Both of these show a shift in energy content from the higher Both of these show a shift in energy content from the higher to the lower frequencies during anaesthesia. The relationship to the lower frequencies during anaesthesia. The relationship between these quantities is also analyzed as a separate between these quantities is also analyzed as a separate parameter (parameter (ββ--αα). ).

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

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

► The monitor also evaluates the amount of instantaneous burst The monitor also evaluates the amount of instantaneous burst suppression (BS) in each thirty-second period of the EEG.suppression (BS) in each thirty-second period of the EEG.

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

► The CSI is a unit-less scale from 0 to 100,where 0 indicates a The CSI is a unit-less scale from 0 to 100,where 0 indicates a flat EEG and 100 indicate EEG activity corresponding to the flat EEG and 100 indicate EEG activity corresponding to the awake state. The range of adequate anaesthesia is designed to awake state. The range of adequate anaesthesia is designed to be between 40 and 60.be between 40 and 60.

► CSI detects well the graduated levels of propofol anaesthesia CSI detects well the graduated levels of propofol anaesthesia when compared with the propofol effect site concentration and when compared with the propofol effect site concentration and the OAAS scorethe OAAS score

► It behaves as other depth of anaesthesia monitors with a It behaves as other depth of anaesthesia monitors with a progressive decrease during propofol induction but loss of progressive decrease during propofol induction but loss of consciousness with N2O results no change in CSI.consciousness with N2O results no change in CSI.

► No published literature was found for impact on intraoperative No published literature was found for impact on intraoperative awareness.awareness.

ASA Practice AdvisoryASA Practice Advisory

The decision to administer benzodiazepine The decision to administer benzodiazepine prophylactically should be made on a case-by-prophylactically should be made on a case-by-case basis for selected patientscase basis for selected patients

Intraoperative monitoring of depth of anesthesia Intraoperative monitoring of depth of anesthesia should rely on multiple modalities, including should rely on multiple modalities, including clinical techniques and conventional monitoring clinical techniques and conventional monitoring systems( ECG, BP, end-tidal gas analyzer)systems( ECG, BP, end-tidal gas analyzer)

ASA Practice AdvisoryASA Practice Advisory

The decision to use a brain function monitor The decision to use a brain function monitor should be made on a case-by-case basis.should be made on a case-by-case basis.

Cautions!!!Cautions!!!

Maintaining low brain function monitor values Maintaining low brain function monitor values in an attempt to prevent intraoperative in an attempt to prevent intraoperative awareness may conflict with other anesthesia awareness may conflict with other anesthesia goals (preservation vital functions)goals (preservation vital functions)

Opioid in tivaOpioid in tiva