Depth of Anaesthesia by Medical Device Management

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Depth of Anaesthesia byMedical Device Management

• aepEX

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auditory evoked potential Index

• aepEX

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auditory evoked potential IndEX

• aepEX

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aepEX Depth of Anaesthesia

• Confidence in the palm of your hand

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aepEX
Benefits

• Compact
• Simple to Use
• Robust Proven Technology
• Consistent Results with most Anaesthetic Agents
• Results unaffected by patients body temperature
• Clearly defined awake/asleep threshold

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aepEX
Todays Presentation

• What is Depth of Anaesthesia
• How do we measure Depth of anaesthesia
• What is the difference between aepEX and other
  systems
• aepEX and how it works

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Depth of Anaesthesia
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Depth of Anaesthesia

• One persons comments on awareness
• 'I just started to scream inside my head and
  prayed that I would not die'
• 'I could hear my skin tearing and ripping and
  it felt like someone took a blow torch to my
  stomach'

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Depth of Anaesthesia

• One persons comments on awareness
• 'my awareness during surgery has dramatically
  changed my life'
• 'not a minute goes by that I don't remember the
  horror of my surgery'
• 'in many respects my life has been a nightmare
  since my surgery'

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Depth of Anaesthesia

• Awareness
• Authors Date Aware Dreams Sample
• Hutchison et al 1960 1.2 3.0
  656
• Harris et al 1971 1.6 26.0 120
• McKenna Wilton 1973 1.5 - 200
• Wilson et al 1975 0.8 7.7 490
• Liu et al 1991 0.2 0.9 (1000)
• Dowd et al 1998 0.3 - 608
• Sandin et al 2000 0.18 - 11,785

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Depth of Anaesthesia

• Awareness
• may not be identifiable from the observation of
  cardiovascular data
• can cause major trauma
• may lead to longer term effects

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Depth of Anaesthesia

• Awareness
• mental depression
• personality transformation
• sleep disturbances including dreams, nightmares
  and insomnia

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Depth of Anaesthesia

• Awareness
• The number of cases is difficult to identify
  because of the amnesic affect of the anaesthetic
  agents

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Depth of Anaesthesia

• Measuring Anaesthesia
• patient movement
• autonomic effects
• lower oesophageal contractility
• analysis of the EEG
• median frequency
• spectral edge
• bispectral analysis
• auditory evoked response

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Depth of Anaesthesia

• Measuring Anaesthesia
• Transition between conscious and unconscious
  state - no relaxants
• loss of verbal contact
• loss of motor control
• loss of eyelash reflex

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Depth of Anaesthesia

• Measuring Anaesthesia
• Transition between conscious and unconscious
  state - with relaxants
• PRST scoring system
• isolated forearm technique

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Depth of Anaesthesia

• Analysis of the EEG
• median frequency
• spectral edge
• bispectral analysis
• auditory evoked response

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Depth of Anaesthesia

• Analysis of the EEG
• bispectral analysis
• auditory evoked response

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Depth of Anaesthesia

• The Gold Standard
• What should we look for in a
• Depth of Anaesthesia Monitor?

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Depth of Anaesthesia

• The Gold Standard
• Provide information to permit satisfactory
  anaesthetic conditions
• Patient breathing spontaneously
• Undergoing a surgical procedure

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Depth of Anaesthesia

• The Gold Standard
• Similar values for different agents
• Appropriate change during surgery
• Index at induction similar to index at recovery
• Unaffected by temperature or CVS changes or drugs
• Marked awake-asleep difference with no recall for
  events during anaesthesia

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Depth of Anaesthesia

• The Gold Standard
• The ultimate test for a depth of anaesthesia
  monitor
• To control automatically the delivery of an
  anaesthetic agent to produce
• Satisfactory anaesthesia in patients breathing
  spontaneously during surgery

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Depth of Anaesthesia

• Bispectral edge analysis
• For comparison we will look at the Bispectral
  edge analysis

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Depth of Anaesthesia

• bispectral edge analysis
• quantifies the phase coupling between any two
  frequencies and a third frequency (harmonic) and
  their sum (or difference)
• the extent of the coupling between two
  frequencies (bicoherence) can vary
• from 0 if no harmonic is being generated
• to 100 if a harmonic is generated for the
  duration of the period analysed
• Result is compared to expert Data Base

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Depth of Anaesthesia

• bispectral edge analysis
• The system has been referred to as an expert
  reference system not a monitor
• The system references historic data which does
  not account for the changes in clinical practice
  or patient variables
• It is a better predictor of blood concentration
  than depth of anaesthesia

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Depth of Anaesthesia

• The next step
• Bispectral edge is a passive system
• Bispectral edge is NOT a real time system
• Auditory Evoked Potential is an active system
• AEP is stimulation followed by Response
• AEP is a real time system
• aepEX the future

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Depth of Anaesthesia

• aepEX Development
• Over 10 years development
• Glasgow University
• Numerous Papers and thousands of patients

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aepEX Development
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Depth of Anaesthesia
aepEX

• aepEX

AEP
EEG
Sound 7Hz
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Depth of Anaesthesia

• aepEX

latency increased
amplitude decreased
sound stimulus
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Depth of Anaesthesia

• Anaesthesia is a balanced combination of three
  basic elements
• Hypnotics
• Analgesics
• Surgical stimulation

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Surgery
Stimulation
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Surgery
Autonomic Effects
Awareness
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Surgery
Awareness
Recall
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Surgery
Awareness
Recall
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Surgery
Awareness
Recall
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Surgery
Awareness
Recall
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Surgery
Awareness
Recall
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Propofol-Remifentanil Interaction
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Depth of Anaesthesia

• aepEX
• A real time monitor
• Monitoring the response to a specific stimulation
• Not a historic comparison
• Monitoring all 3 key aspects of the depth of
  Anaesthesia

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Depth of Anaesthesia

• Review of Clinical Papers

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Depth of Anaesthesia

• Middle latency auditory evoked potentials during
  repeated transitions from consciousness to
  unconsciousness
• Davies FW, Mantzaridis H, Fisher AC Kenny GN.
  (1996) Anaesthesia 51, 107-113

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Depth of Anaesthesia

• aepEX

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Depth of Anaesthesia

• Analysis of the EEG bispectrum, auditory evoked
  potentials and the EEG power spectrum during
  repeated transitions from consciousness to
  unconsciousness
• Gajraj RJ, Doi M, Mantzaridis H and Kenny GN.
  Br.J.Anaesth. 1997 80 46-52

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Depth of Anaesthesia
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Depth of Anaesthesia

• Relationship between calculated blood
  concentration of Propofol and electrophysiological
  variables during emergencefrom anaesthesia
• Doi M, Gajraj RJ, Mantzaridis H Kenny GN. Br.
  J. Anaesth. 1997 78, 180-184

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Depth of Anaesthesia

• Effects of cardiopulmonary bypass and hypothermia
  on electroencephalographic variables
• Doi, M., Gajraj, R.J., Mantzaridis, H., Kenny,
  G.N. anaesthesia 1997 52 1046-55

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aepEX compared to Bispectral Edge
Bispectral Edge
aepEX
n
12
mean (range)




















plt0.05 vs 5 min before CPB
Cardiopulmonary Bypass
5
10
20
30
5 min
5 min
30 min
Before
5 min
5 min
before
after
induction
after
before
end of
CPB
induction
CPB
CPB
stopped
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Depth of Anaesthesia

• Comparison Of Bispectral EEG Analysis With
  Auditory Evoked Potentials In Anaesthetised
  Patients
• Gajraj RJ, Doi M, Mantzaridis H Kenny GN.
  Anesthesiol. 1996 78

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Depth of Anaesthesia

aepEX
100
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Depth of Anaesthesia

Bispectral Edge
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Depth of Anaesthesia

• Some Quotations

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Depth of Anaesthesia

• The aepEX technology can accurately reflect
  anaesthesia produced by different types of
  anaesthetic agents, helping the anaesthetist to
  avoid excessive dosing
• Professor Gavin Kenny
• Head of Department of Anaesthesia
• University of Glasgow

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Depth of Anaesthesia

• With respect to AEPs middle latency (early
  Cortical) response is clearly the section on
  which to focus
• It shows appropriate sensitivity to general
  anaesthesia with similar graded changes with a
  whole range of agents
• Responds to noxious stimulation, surgery,
  intubation
• Dr Christine Thorton
• Northwick Park Hospital London

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Depth of Anaesthesia

• Auditory Evoked Potentials index offers better
  discriminatory power in describing the transition
  from the conscious to the unconscious state in
  the individual patient
• International Anaesthesia Research Society
• Anesthesia and Analgesia 1999891311

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Depth of Anaesthesia

• The Gold Standard
• aepEX meets the gold standard

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Depth of Anaesthesia

• The Gold Standard
• aepEX provides information to permit satisfactory
  anaesthetic conditions with
• Patient breathing spontaneously
• Undergoing a surgical procedure

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Depth of Anaesthesia

• aepEX provides
• Similar values for different agents
• Appropriate change during surgery
• Value at induction similar to value at recovery
• Unaffected by temperature or CVS changes or drugs
• Marked awake-asleep difference with no recall for
  events during anaesthesia

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Depth of Anaesthesia

• aepEX has achieved
• The ultimate test for a depth of anaesthesia
  monitor
• To control automatically the delivery of an
  anaesthetic agent to produce
• Satisfactory anaesthesia in patients breathing
  spontaneously during surgery

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aepEX
Benefits

• Meets the requirements of the Gold Standard
• Compact
• Simple to Use
• Robust Proven Technology
• Consistent Results with most Anaesthetic Agents
• Results unaffected by patients body temperature
• Clearly defined awake/asleep threshold

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aepEX Depth of Anaesthesia

• Confidence in the palm of your hand

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aepEX Depth of Anaesthesia

• Confidence in the palm of your hand