1. Monitoring Depth of
Anaesthesia
Presentation by :
Dr. Ketaki Didolkar
Guided by :
Dr. Abhay Bodhey

3. AIM OF MONITORING :AIM OF MONITORING :
 Guarantee the safety of anaesthesia as well as theGuarantee the safety of anaesthesia as well as the
painlessness of surgery.painlessness of surgery.
 Overall incidence of intra-operative awareness-Overall incidence of intra-operative awareness-
0.2-3 %0.2-3 %
 Incidence >40% in patients of cardiac surgery,Incidence >40% in patients of cardiac surgery,
caesarean section, multiple trauma &caesarean section, multiple trauma &
haemodynamically unstable patients.haemodynamically unstable patients.
 A 2001 study reported that 56.3% of a group of
patients who had awakened during surgery met the
diagnostic criteria for ‘post traumatic stress disorder’—
as late as 17 years after their operation.

5. AIM OF MONITORING :AIM OF MONITORING :
Intra-operative awareness isIntra-operative awareness is
a major medicolegal liabilitya major medicolegal liability
to anaesthetists & it is ourto anaesthetists & it is our
prime responsibility toprime responsibility to
diagnose and avoid it at alldiagnose and avoid it at all
costs !!!!costs !!!!

6. HISTORICAL BACKGROUND :HISTORICAL BACKGROUND :
 DioscoridesDioscorides first used the term ‘anaesthesia’ tofirst used the term ‘anaesthesia’ to
describe narcotic effect of plant mandragora.describe narcotic effect of plant mandragora.
 O.W. HolmesO.W. Holmes coined the term ‘anaesthesia’ tocoined the term ‘anaesthesia’ to
describe the new phenomenon that made surgicaldescribe the new phenomenon that made surgical
procedures possible.procedures possible.
 PlomleyPlomley (1847) first attempted to define depth of(1847) first attempted to define depth of
anaesthesia by describing 3 stages- intoxication,anaesthesia by describing 3 stages- intoxication,
excitement and narcosis.excitement and narcosis.
 John SnowJohn Snow (1847) described ‘five degrees of(1847) described ‘five degrees of
narcotism’ ; the first 3 included induction ofnarcotism’ ; the first 3 included induction of
anaesthesia by ether & last 2 represented surgicalanaesthesia by ether & last 2 represented surgical
anaesthesia.anaesthesia.

7. HISTORICAL BACKGROUND :HISTORICAL BACKGROUND :
 GuedelGuedel (1937) gave the classic description of clinical signs of(1937) gave the classic description of clinical signs of
ether anaesthesia. Included 4 stages: analgesia, delirium,ether anaesthesia. Included 4 stages: analgesia, delirium,
surgical anaesthesia & respiratory paralysis.surgical anaesthesia & respiratory paralysis.

8. HISTORICAL BACKGROUND :HISTORICAL BACKGROUND :
 ArtusioArtusio (1954) expanded Guedel’s stage 1 into 3 planes :(1954) expanded Guedel’s stage 1 into 3 planes :
1)1) No amnesia & analgesiaNo amnesia & analgesia
2)2) Total amnesia & partial analgesiaTotal amnesia & partial analgesia
3)3) Complete amnesia & analgesiaComplete amnesia & analgesia
 WoodbridgeWoodbridge (1957) defined 4 components of anaesthesia :(1957) defined 4 components of anaesthesia :
I.I. Sensory blockade of afferent impulsesSensory blockade of afferent impulses
II.II. Motor blockade of efferent impulsesMotor blockade of efferent impulses
III.III. Reflex blockade of RS, CVS, GI tractReflex blockade of RS, CVS, GI tract
IV.IV.Mental block or unconsciousnessMental block or unconsciousness
 Prys – RobertsPrys – Roberts (1987) defined anaesthesia as a state in(1987) defined anaesthesia as a state in
which the patient neither perceives nor recalls noxious stimuliwhich the patient neither perceives nor recalls noxious stimuli
as a result of drug induced unconsciousness.as a result of drug induced unconsciousness.

9. MODERN CONCEPT :MODERN CONCEPT :
 In modern times, anaesthesia is a complex interactionIn modern times, anaesthesia is a complex interaction
of multiple stimuli applied, the diverse responsesof multiple stimuli applied, the diverse responses
measured & the drug induced probability ofmeasured & the drug induced probability of
nonresponsiveness to stimuli.nonresponsiveness to stimuli.
 TheThe hypnotic agentshypnotic agents produce such profound CNSproduce such profound CNS
depression that the most powerful surgical stimulusdepression that the most powerful surgical stimulus
cannot arouse patient from state ofcannot arouse patient from state of
nonresponsiveness.nonresponsiveness.
 TheThe analgesicsanalgesics && LALA attenuate the surgical stimuli.attenuate the surgical stimuli.
 The interaction between analgesics & hypnotics isThe interaction between analgesics & hypnotics is
thus fundamental to understanding & definingthus fundamental to understanding & defining
anaesthetic depth.anaesthetic depth.

11. PAIN & ANAESTHETICSPAIN & ANAESTHETICS

12. FACTORS AFFECTING CORRECT DRUGFACTORS AFFECTING CORRECT DRUG
DOSES:DOSES:
 The lack of a universally acceptedThe lack of a universally accepted definition ofdefinition of
"consciousness.”"consciousness.”
 The increased use ofThe increased use of combinations of anaestheticcombinations of anaesthetic
agents rather than single drugs.agents rather than single drugs.
 Changes in the patient's response to anaesthesia overChanges in the patient's response to anaesthesia over
thethe course of the operation.course of the operation.
 AgeAge-related differences in responsiveness to specific-related differences in responsiveness to specific
anaestheticsanaesthetics
 SexSex : Women appear to emerge from anaesthesia: Women appear to emerge from anaesthesia
more rapidly than men.more rapidly than men.
 Individual variationIndividual variation in sensitivity to anaesthesiain sensitivity to anaesthesia

13. MEMORY AND ANAESTHESIA:MEMORY AND ANAESTHESIA:
 Anaesthesia , with increasing depth , progressivelyAnaesthesia , with increasing depth , progressively
decreases the ability of brain to carry out tasks and todecreases the ability of brain to carry out tasks and to
remember them afterwards.remember them afterwards.
 Memory is affected much before noticeable autonomicMemory is affected much before noticeable autonomic
responses are seen.responses are seen.
 Types of memory :-Types of memory :-
 Short -termShort -term
 Long –termLong –term
 Procedural / ImplicitProcedural / Implicit }} effortlesseffortless
retrievalretrieval
 Declarative : 1) Somatic / ImplicitDeclarative : 1) Somatic / Implicit
2) Episodic / Explicit - efforts required2) Episodic / Explicit - efforts required

14. STAGES OF AwARENESS :STAGES OF AwARENESS :
(GRIFFITH & JONES)(GRIFFITH & JONES)
1.1. Conscious awareness with explicit recallConscious awareness with explicit recall
2.2. Conscious awareness with no explicit recallConscious awareness with no explicit recall
3.3. Unconscious awareness with implicit recallUnconscious awareness with implicit recall
4.4. No awarenessNo awareness

19. Specific drugS & depth ofSpecific drugS & depth of
anaeStheSia :anaeStheSia :

20. inhalational agentS :inhalational agentS :
 Purposeful movement of any part of the body inPurposeful movement of any part of the body in
response to noxious perioperative stimuli is the mostresponse to noxious perioperative stimuli is the most
useful clinical sign of depth of anaesthesiauseful clinical sign of depth of anaesthesia
 Eger & Merkel therefore defined MAC as the minimumEger & Merkel therefore defined MAC as the minimum
alveolar concentration of inhaled anaesthetic requiredalveolar concentration of inhaled anaesthetic required
to prevent 50% of subjects from responding to painfulto prevent 50% of subjects from responding to painful
stimuli with gross purposeful movementstimuli with gross purposeful movement
Tracheal intubation represents stronger noxious
stimulus than all surgical stimuli

21. inhalational agentS :inhalational agentS :
MAC has been expanded as :MAC has been expanded as :
 MAC-awake :(Stoelting)minimum alveolarMAC-awake :(Stoelting)minimum alveolar
concentration that would allow opening of eyes onconcentration that would allow opening of eyes on
verbal command during emergence from anaesthesiaverbal command during emergence from anaesthesia
 MAC-intubation : (Yakaitis)minimum alveolarMAC-intubation : (Yakaitis)minimum alveolar
concentration that would inhibit movement & coughingconcentration that would inhibit movement & coughing
during endotracheal intubation.during endotracheal intubation.
MAC-BAR : (Roizen)minimum alveolar concentration
that would prevent adrenergic response to skin incision
as measured by venous concentration of
catecholamines

22.  MAC may be modified by use of nitrous oxide,opioidsMAC may be modified by use of nitrous oxide,opioids
& other anaesthetics& other anaesthetics
 The haemodynamic responses to surgical stimuli doThe haemodynamic responses to surgical stimuli do
not correlate well with end tidal concentration ofnot correlate well with end tidal concentration of
inhaled anaesthetics.inhaled anaesthetics.
inhalational agentS :inhalational agentS :

23. nonopioid intravenouS agentS:nonopioid intravenouS agentS:
induction of anaeStheSiainduction of anaeStheSia
Plasma drug concentration peaks in half to one minutePlasma drug concentration peaks in half to one minute
& declines rapidly due to redistribution& declines rapidly due to redistribution
Depth of anaesthesia follows plasma drugDepth of anaesthesia follows plasma drug
concentrationconcentration
Clinical endpoints for assessment-Clinical endpoints for assessment-
1.1. Loss of verbal responsivenessLoss of verbal responsiveness
2.2. Loss of eyelid reflexLoss of eyelid reflex
3.3. Loss of corneal reflexLoss of corneal reflex
 Strongest stimulation during induction is laryngoscopyStrongest stimulation during induction is laryngoscopy
& intubation& intubation
 Analgesics are needed to maintain haemodynamicsAnalgesics are needed to maintain haemodynamics

24. nonopioid intravenouS agentS:nonopioid intravenouS agentS:
Maintenance of anaeStheSiaMaintenance of anaeStheSia
Plasma levels of anaesthetic agents are accuratePlasma levels of anaesthetic agents are accurate
predictors of brain levels of the drug & good indicatorspredictors of brain levels of the drug & good indicators
of anaesthetic depthof anaesthetic depth
Clinical endpoints for assessment :Clinical endpoints for assessment :
1.1. Loss of eyelid reflexLoss of eyelid reflex
2.2. Loss of corneal reflexLoss of corneal reflex
3.3. Absence of movement in response to sqeezingAbsence of movement in response to sqeezing
trapeziustrapezius
Opioids in large doses need to be added when preciseOpioids in large doses need to be added when precise
haemodynamic control is necessary as in CADhaemodynamic control is necessary as in CAD

25. t.i.v.a.t.i.v.a.
‘‘Minimum infusion rate’ is used to compareMinimum infusion rate’ is used to compare
requirements of anaestheticsrequirements of anaesthetics
The 50% effective dose & 95 % effective doseThe 50% effective dose & 95 % effective dose
infusion rates are calculated using movementinfusion rates are calculated using movement
response to skin incisionresponse to skin incision
IV bolus of anaesthetic combined with maintenanceIV bolus of anaesthetic combined with maintenance
infusion can produce steady state plasmainfusion can produce steady state plasma
concentration of the drug to maintain anaestheticconcentration of the drug to maintain anaesthetic
depth.depth.

26. opioidS :opioidS :
CpCp5050 is steady state plasma concentration of opioidis steady state plasma concentration of opioid
which will prevent purposeful movement to noxiouswhich will prevent purposeful movement to noxious
stimuli in 50% populationstimuli in 50% population
Clinical events which indicate inadequate infusionClinical events which indicate inadequate infusion
rates-rates-
1)1) Increase in systolic BP more than 15 mmHg aboveIncrease in systolic BP more than 15 mmHg above
normal for the patientnormal for the patient
2)2) Heart rate > 90/m in absence of hypovolemiaHeart rate > 90/m in absence of hypovolemia
3)3) Somatic : movement, swallowing, coughing or openingSomatic : movement, swallowing, coughing or opening
eyeseyes
4)4) Autonomic : lacrimation, sweating, flushingAutonomic : lacrimation, sweating, flushing

27. aSSeSSMent of depthaSSeSSMent of depth
of anaeStheSia :of anaeStheSia :

28. Subjective methodsSubjective methods ::
– Autonomic changesAutonomic changes
– Changes in pupil diameterChanges in pupil diameter
– Isolated forearm techniqueIsolated forearm technique
Objective methodsObjective methods ::
– E.E.G. & derived indicesE.E.G. & derived indices
– Spontaneous surface electromyogramSpontaneous surface electromyogram
– Lower oesophageal contractilityLower oesophageal contractility
– Heart rate variabilityHeart rate variability
– Evoked potentialsEvoked potentials
claSSification of MethodS :claSSification of MethodS :

29. SuBJective MethodS :SuBJective MethodS :

30. 1. autonoMic changeS :1. autonoMic changeS :
 Include sudden hypertension, tachycardia, sweating,Include sudden hypertension, tachycardia, sweating,
tearing or mydriasistearing or mydriasis
 Commonly used as clinical indicators of lightening ofCommonly used as clinical indicators of lightening of
depth of anaesthesiadepth of anaesthesia
 Patient response to surgical stimulus (PRST) scorePatient response to surgical stimulus (PRST) score
includes 4 haemodynamic parameters : Pressureincludes 4 haemodynamic parameters : Pressure
(BP), Rate (pulse rate), Sweating & Tearing(BP), Rate (pulse rate), Sweating & Tearing

31. p.r.S.t. Scorep.r.S.t. Score
INDEX : CONDITION : SCORE :
Pressure <control + 15
<control + 30
>control + 30
0
1
2
Pulse Rate <control + 15
<control + 30
>control + 30
0
1
2
Sweating Nil
Skin moist
Visible beads of sweat
0
1
2
Tears No excess tears in open eyes
Excess tears in open eyes
Tears over flowing
0
1
2

32. diSadvantageS :diSadvantageS :
 These changes are also seen with intra-operativeThese changes are also seen with intra-operative
events like hypotension, dehydration, hypoxia,events like hypotension, dehydration, hypoxia,
hypothermia, hyperthermia or sudden blood loss.hypothermia, hyperthermia or sudden blood loss.
 Patient factors like built & baseline tone also affectPatient factors like built & baseline tone also affect
 Drugs like beta blockers , inotropes, vasodilators, anti-Drugs like beta blockers , inotropes, vasodilators, anti-
hypertensives also lead to such haemodynamichypertensives also lead to such haemodynamic
changes while opioids & muscle relaxants suppresschanges while opioids & muscle relaxants suppress
them.them.
 Haemodynamic response to noxious stimuli does notHaemodynamic response to noxious stimuli does not
necessarily signify awareness nor does lack ofnecessarily signify awareness nor does lack of
haemodynamic changes guarantee unconsciousnesshaemodynamic changes guarantee unconsciousness

33. 2. changeS in pupil diaMeter :2. changeS in pupil diaMeter :
 Guedel’s stages of ether anaesthesia describe initialGuedel’s stages of ether anaesthesia describe initial
pupillary constriction followed by dilatation aspupillary constriction followed by dilatation as
anaesthesia deepens.anaesthesia deepens.
 These changes are affected by circulatingThese changes are affected by circulating
catecholamines, atropine & opioids.catecholamines, atropine & opioids.
 Pupillary light reflex is also affected by opioids &Pupillary light reflex is also affected by opioids &
anoxia .anoxia .

34. 3.iSolated forearM techniQue :3.iSolated forearM techniQue :
 Tourniquet inflated on an arm of patient prior toTourniquet inflated on an arm of patient prior to
administering intravenous muscle relaxant isolatesadministering intravenous muscle relaxant isolates
forearm & allows it to remain free to move in responseforearm & allows it to remain free to move in response
to verbal command in light plane of anaesthesia.to verbal command in light plane of anaesthesia.
 Limitations :Limitations :
 Nonspecific startle response may be wronglyNonspecific startle response may be wrongly
interpreted as consciousnessinterpreted as consciousness
 Higher dose of muscle relaxant required in IFT toHigher dose of muscle relaxant required in IFT to
prevent movementprevent movement
 Inability to move arm despite consciousness isInability to move arm despite consciousness is
complained by some patientscomplained by some patients

35. oBJective MethodS :oBJective MethodS :

36. 1.electroencephalograM :1.electroencephalograM :
 EEG is a low voltage (1-50 µv) deflection recordedEEG is a low voltage (1-50 µv) deflection recorded
from surface of scalp by electrodes.from surface of scalp by electrodes.
 Noninvasive indicator of cerebral functionNoninvasive indicator of cerebral function
 Represents cortical electrical activity derived fromRepresents cortical electrical activity derived from
excitatory & inhibitory postsynaptic activityexcitatory & inhibitory postsynaptic activity
 This electrical activity has physiologic correlatesThis electrical activity has physiologic correlates
relevant to depth of anaesthesiarelevant to depth of anaesthesia
 Cerebral physiology & metabolism both affect the EEGCerebral physiology & metabolism both affect the EEG
& anaesthetic drugs affect both cerebral physiology && anaesthetic drugs affect both cerebral physiology &
EEGEEG

37. 1.ELECTROENCEPHALOGRAM :1.ELECTROENCEPHALOGRAM :
 Effects of noxious stimulus on EEG :Effects of noxious stimulus on EEG :
 Desynchronization with appearance of fast rhythmsDesynchronization with appearance of fast rhythms
 Appearance of 6 -10 Hz spindlesAppearance of 6 -10 Hz spindles
 Bursts of 1-3 Hz slow wavesBursts of 1-3 Hz slow waves
 Anaesthetic drugs result in low frequency EEG & burstAnaesthetic drugs result in low frequency EEG & burst
suppression at high concentrationsuppression at high concentration

39. EEG INDICES :EEG INDICES :
1) Compressed spectral array (CSA):1) Compressed spectral array (CSA):
 The individual frequency distributions of EEG can beThe individual frequency distributions of EEG can be
considered as time slices and joined together into aconsidered as time slices and joined together into a
3D plot is called CSA3D plot is called CSA
 During peaks of anaesthesia, CSA shows lowDuring peaks of anaesthesia, CSA shows low
frequency activityfrequency activity
 At recovery and lighter planes CSA shows highAt recovery and lighter planes CSA shows high
frequency activity with decreased low frequencyfrequency activity with decreased low frequency
waveswaves
 Disadvantages include difficulty to comprehend theDisadvantages include difficulty to comprehend the
changes & to quantify themchanges & to quantify them

41. EEG INDICES :EEG INDICES :
2) Spectral edge frequency (SEF) : Defined as2) Spectral edge frequency (SEF) : Defined as
frequency below which 95 % of EEG power isfrequency below which 95 % of EEG power is
contained.contained.
3) Median frequency (MF) : Defined as frequency above3) Median frequency (MF) : Defined as frequency above
& below which 50% of EEG power spectrum is& below which 50% of EEG power spectrum is
distributed.distributed.
4) Bispectral index (BIS)4) Bispectral index (BIS)

42. BISPECTRALBISPECTRAL
INDEXINDEX

43. BISPECTRAL INDEX :BISPECTRAL INDEX :
 Developed in 1987, by Aspect Medical Systems inDeveloped in 1987, by Aspect Medical Systems in
MassachusettsMassachusetts




 It is a numerical index ranging from 100 (awake) to 0It is a numerical index ranging from 100 (awake) to 0
(no detectable EEG activity)(no detectable EEG activity)
 The BIS correlates with level of responsiveness &The BIS correlates with level of responsiveness &
provides an excellent prediction of the level ofprovides an excellent prediction of the level of
consciousness with propofol, midazolam & isofluraneconsciousness with propofol, midazolam & isoflurane
anaesthesiaanaesthesia
 The bispectral index itself is a complex mathematical
algorithm that allows a computer inside the BIS
monitor to analyze data from a patient's
electroencephalogram (EEG) during surgery.

44.  Multiple clinically relevant measures like movement,Multiple clinically relevant measures like movement,
haemodynamics, drug concentrations, consciousness,haemodynamics, drug concentrations, consciousness,
recall are considered alongwith concurrent EEG data.recall are considered alongwith concurrent EEG data.
 Advanced multivariate statistical analysis is used toAdvanced multivariate statistical analysis is used to
correlate components of the multiple EEG signalcorrelate components of the multiple EEG signal
processing approaches with the clinical data to createprocessing approaches with the clinical data to create
the univariate BIS indexthe univariate BIS index
 The BIS index measures hypnotic components of theThe BIS index measures hypnotic components of the
anaesthetic & is insensitive to analgesic components.anaesthetic & is insensitive to analgesic components.
 BIS is useful monitor to adjust anaesthetic dosages &BIS is useful monitor to adjust anaesthetic dosages &
decreases incidence of haemodynamic disturbances &decreases incidence of haemodynamic disturbances &
leads to improved recoveryleads to improved recovery
BISPECTRAL INDEX :BISPECTRAL INDEX :

45. DESCRIPTION :DESCRIPTION :
 The BIS system is integrated into patientThe BIS system is integrated into patient
monitoring devices .monitoring devices .
 The BIS system displays both raw data fromThe BIS system displays both raw data from
the EEG and a single number between 100the EEG and a single number between 100
(indicating an awake patient) and 0 (indicating(indicating an awake patient) and 0 (indicating
the absence of brain activity) that representsthe absence of brain activity) that represents
the patient's degree of sedation.the patient's degree of sedation.
 The target number for most anesthetizedThe target number for most anesthetized
patients is between 40 and 60.patients is between 40 and 60.

46. BIS ELECTRODESBIS ELECTRODES::

49. DEvELOPING THE BIS INDEX :DEvELOPING THE BIS INDEX :

50. BIS & DOSAGE TITRATIONBIS & DOSAGE TITRATION
Physical signs Clinical
picture
BIS
value
Management
1. Hypertension Light High Consider hypnotic / analgesic doses
Tachycardia 40-60 Analgesic dose / antihypertensive
Movement Low Decrease hypnotic dose / start
antihypertensive
Autonomic response
2.Stable vitals Adequate High Consider hypnotic / analgesic doses
40-60 Observe
Low Consider decrease in both drug doses
3.Hypotension Deep High Consider hypnotic / analgesic doses
Arrhythmias Rule out other etiologies
BP support
40-60 Rule out other etiologies
BP support

51. LIMITATIONS Of BIS :LIMITATIONS Of BIS :
BIS values are affected by the choice of anestheticBIS values are affected by the choice of anesthetic
agent. A patient with a BIS score of 60agent. A patient with a BIS score of 60
anesthetized with one combination of agents mayanesthetized with one combination of agents may
be more deeply sedated than another patient withbe more deeply sedated than another patient with
the same score but anesthetized with a differentthe same score but anesthetized with a different
combination of drugs.combination of drugs.
The BIS monitor appears unable to accuratelyThe BIS monitor appears unable to accurately
track changes in consciousness produced bytrack changes in consciousness produced by
certain anaesthetics, specifically ketamine andcertain anaesthetics, specifically ketamine and
nitrous oxide.nitrous oxide.
The changes in the BIS algorithm resulting fromThe changes in the BIS algorithm resulting from
updating and refinement of the producer’supdating and refinement of the producer’s

52. LIMITATIONS Of BIS :LIMITATIONS Of BIS :
database make it difficult to compare resultsdatabase make it difficult to compare results
obtained by different investigators using differentobtained by different investigators using different
versions of the BIS monitor.versions of the BIS monitor.
BIS values are difficult to correlate with otherBIS values are difficult to correlate with other
measurements of anaesthetic depth or alteredmeasurements of anaesthetic depth or altered
consciousness like serum concentrations ofconsciousness like serum concentrations of
anesthetic agents.anesthetic agents.
Standard BIS scores are not useful in monitoringStandard BIS scores are not useful in monitoring
special patient populations, particularly critically illspecial patient populations, particularly critically ill
patients with unstable body temperatures andpatients with unstable body temperatures and
patients with dementia.patients with dementia.

53. USES Of BIS :USES Of BIS :
Reduces cost by decreasing anaesthetic use & stay inReduces cost by decreasing anaesthetic use & stay in
PACUPACU
Provides a useful guide for titration of anaestheticProvides a useful guide for titration of anaesthetic
agents in cardiac surgery, elderly & paediatric patientsagents in cardiac surgery, elderly & paediatric patients
Reduces the incidence of intraoperative awarenessReduces the incidence of intraoperative awareness

54. SPONTANEOUS SURfACESPONTANEOUS SURfACE
ELECTROMyOGRAMELECTROMyOGRAM

55. SpontaneouS SurfaceSpontaneouS Surface
electromyogramelectromyogram
 In patients who are not completely paralyzed,In patients who are not completely paralyzed,
spontaneous surface electromyogram (SEMG) can bespontaneous surface electromyogram (SEMG) can be
recorded from various muscle groups, especiallyrecorded from various muscle groups, especially
facial, abdominal and neck muscles.facial, abdominal and neck muscles.
 The level of SEMG has been observed to fall duringThe level of SEMG has been observed to fall during
anaesthesia and to rise to pre-anaesthetic levels justanaesthesia and to rise to pre-anaesthetic levels just
before awakening.before awakening.

56. lower oeSophageallower oeSophageal
contractilitycontractility

57. lower oeSophageallower oeSophageal
contractilitycontractility
 The non-striated muscles in the lower half ofThe non-striated muscles in the lower half of
oesophagus retain their potential activity even after fulloesophagus retain their potential activity even after full
skeletal muscle paralysis.skeletal muscle paralysis.
 Provide two prime derivativesProvide two prime derivatives
1] Spontaneous lower oesophageal1] Spontaneous lower oesophageal
contractions(SLOG)contractions(SLOG)
These are non-propulsive spontaneous contractionsThese are non-propulsive spontaneous contractions
mediated via vagal motor nuclei and reticularmediated via vagal motor nuclei and reticular
activating system in the brain stem. The frequency ofactivating system in the brain stem. The frequency of
these movements is increased as the dose of thethese movements is increased as the dose of the
anaesthetic is reduced.anaesthetic is reduced.

58. lower oeSophageallower oeSophageal
contractilitycontractility
2] Provoked lower oesophageal contractions(PLO)2] Provoked lower oesophageal contractions(PLO)
These are obtained by inflation of a small balloon inThese are obtained by inflation of a small balloon in
the lower oesophagus. The brief inflation of smallthe lower oesophagus. The brief inflation of small
balloon provokes a secondary pulsatile response,balloon provokes a secondary pulsatile response,
which increases in amplitude as anaesthetic depthwhich increases in amplitude as anaesthetic depth
decreases.decreases.

59. heart rateheart rate
variabilityvariability

60. heart rate variabilityheart rate variability
 Normally heart rate increases during inspiration andNormally heart rate increases during inspiration and
decreases during expiration, through a predominantlydecreases during expiration, through a predominantly
parasympathetic reflex connecting stretch receptors inparasympathetic reflex connecting stretch receptors in
the lungs and aorta to vagal motor neuronsthe lungs and aorta to vagal motor neurons
innervating the heart. This is calledinnervating the heart. This is called respiratory sinusrespiratory sinus
arrhythmia(RSA).arrhythmia(RSA).
 It is typically characterized by greater than 10%It is typically characterized by greater than 10%
variation in the ECG P-wave interval over 5 minutesvariation in the ECG P-wave interval over 5 minutes
 There is reduction in RSA during anaesthesia togetherThere is reduction in RSA during anaesthesia together
with increase in RSA during recovery or light planes.with increase in RSA during recovery or light planes.

61. heart rate variabilityheart rate variability
 In addition, surgical stimulation during lightIn addition, surgical stimulation during light
anaesthesia elicits a greater increase on RSA thananaesthesia elicits a greater increase on RSA than
seen during lightening anaesthesia alone.seen during lightening anaesthesia alone.

62. evoked potentialSevoked potentialS

63. evoked potentialS (ep)evoked potentialS (ep)
 Show the response of more localized areas of theShow the response of more localized areas of the
brainstem, midbrain and cerebral cortex to specificbrainstem, midbrain and cerebral cortex to specific
areas.areas.
 Recording of EPs consisting of recording EEG epochsRecording of EPs consisting of recording EEG epochs
and time-referencing them to sensory stimuli that haveand time-referencing them to sensory stimuli that have
been applied in a repeated fashion.been applied in a repeated fashion.
 For intra-operative monitoring, 3 types of EPs areFor intra-operative monitoring, 3 types of EPs are
commonly used:commonly used:
1}SEP (somatosensory EP) is recorded over the1}SEP (somatosensory EP) is recorded over the
somatosensory cortex in response to tibial, peronial orsomatosensory cortex in response to tibial, peronial or
median nerve stimulation.median nerve stimulation.
2}VEP (Visual EP)is recorded over occipital cortex in2}VEP (Visual EP)is recorded over occipital cortex in
response to photic stimulation of the eyes.response to photic stimulation of the eyes.

64. evoked potentialS (ep)evoked potentialS (ep)
3}AEP (auditory EP) is recorded at primary auditory3}AEP (auditory EP) is recorded at primary auditory
cortex in response to auditory canal stimulation bycortex in response to auditory canal stimulation by
audible clicks.audible clicks.It is most commonly used for theIt is most commonly used for the
assessment of anaesthetic drug effect.assessment of anaesthetic drug effect.
• As the concentration of potent inhaled anaestheticAs the concentration of potent inhaled anaesthetic
increases, the latencies of SEP, VEP and AEPincreases, the latencies of SEP, VEP and AEP
increase and amplitudes decrease.increase and amplitudes decrease.
• In contrast, NIn contrast, N22O produces a dose-related decrease inO produces a dose-related decrease in
the amplitude of VEP and SEP, but no effect onthe amplitude of VEP and SEP, but no effect on
latency.latency.

65. auditory evoked potentialauditory evoked potential
indexindex
 Derived from auditory evoked potential and representsDerived from auditory evoked potential and represents
a single numerical variable for monitoring depth ofa single numerical variable for monitoring depth of
anaesthesia.anaesthesia.
 Calculated from the amplitude difference betweenCalculated from the amplitude difference between
successive segments of the AEP curve.successive segments of the AEP curve.
 AEP index of 37 is 100% specific and 52% sensitiveAEP index of 37 is 100% specific and 52% sensitive
for unconsciousness.for unconsciousness.
 AEP index is highly sensitive for distinguishing theAEP index is highly sensitive for distinguishing the
transition from unconsciousness to consciousness.transition from unconsciousness to consciousness.

66. futurefuture

67. futurefuture
The only reliable way of determiningThe only reliable way of determining
depth of anaesthesia will require adepth of anaesthesia will require a
measure of cerebral activity andmeasure of cerebral activity and
localization of the activity to specificlocalization of the activity to specific
cortical regions and areas incortical regions and areas in
brainstem, in real time.brainstem, in real time.

68. poSition emiSSion tomography (pet)poSition emiSSion tomography (pet)
 PET scanning studies havePET scanning studies have
revealed that propofol anaesthesiarevealed that propofol anaesthesia
has a widespread suppressive effecthas a widespread suppressive effect
on cerebral metabolism.on cerebral metabolism.

69. ultra SenSitive Super conductingultra SenSitive Super conducting
quantum interference device (SquidS)quantum interference device (SquidS)
Non invasive method, which measuresNon invasive method, which measures
functional activity of brain.functional activity of brain.
 Although expensive at present this mayAlthough expensive at present this may
provide the ultimate monitor to theprovide the ultimate monitor to the
anaesthesiologists.anaesthesiologists.

70. thank you ….