Preventing and Managing the impact of Awareness during Anaesthesia

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Preventing and Managing the impact of Awareness
during Anaesthesia

• Dr. Subbiah Chelliah MBBS, DA (UK), FRCA (UK),
  DESA (Sweden)
• Consultant Anaesthesiologist,
• Kovai Medical Centre Hospitals, Coimbatore

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Awareness during Anaesthesia

• Awareness
• Definition
• Brief history
• Incidence
• Causes
• Associations
• Stages
• Prevention
• Detecting Awareness
• Preventing Awareness
• Consequences of intra-op awareness
• PTSD
• Public awareness
• Dealing with patients who complain of awareness
  during anaesthesia
• Medico legal aspects

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Definition

• Awareness is the conscious experiencing of an
  event at the time that it occurs. (Guerra 1986)
• Recall denotes the retention of an event in
  memory after it has occurred. (Guerra 1986)

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1895

• Horace Wells attempted to demonstrate N2O to
  physicians at MGH, Boston
• Patient moved cried out!
• Surgeons considered the demonstration a failure
• Patient had no recall of his operation

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1896

• W.T.G. Morton demonstrated the use of Ether in
  the same venue
• Patient did not move
• Surgeons considered it a ground breaking success!
• Mortons patient Gilbert Abbot, reported that he
  had been aware during his surgery, while
  experiencing no pain

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1943

• Muscle relaxants came into clinical use
• Anaesthetists started giving lesser amount of
  anaesthetic agents

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Levinson study (1965)

• 10 pts undergoing dental extraction with ether
  shortly after induction, the anaesthetist called
  to the surgeon STOP THE OPERATION, I dont like
  the patients color. His/her lips are turning too
  blue. I am going to give a little oxygen!
• One month later, probed for assimilation of
  crisis by hypnosis
• 4/10 patients were able to quote verbatin the
  words spoken by the anaesthetist 4 more showed
  evidence of having registered the event, in the
  form of emotional distress

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Levinson study

• Obvious methodological flaws no controls,
  non-randomisation, absence of double blind study,
  asking leading questions
• Thirty years later, Levinson repeated this study
  but failed to replicate his original findings!

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• General Anaesthesia is not an all or nothing
  phenomenon!

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Incidence of Awareness

• Reported incidence of awareness varies and is
  difficult to determine
• Swedish study 0.06
• American academic centres 0.13
• Overall incidence 0.2
• Conscious awareness with pain 1 in 20,000
  40,000 anaesthetics

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Incidence of Awareness

• Cardiac surgery 1 1.5
• Trauma surgery 11 43
• Cesarian section 0.4

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Causes

• Lack of complete understanding of kinetics
  dynamics of drugs
• Induction of anaesthesia
• Coughing
• difficult intubation

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Causes / Associations

• Patient factors
• Limited cardiac reserve (ASA IV V)
• On going blood loss / hypotension
• Patients on beta blockers, Calcium channel
  blockers
• Drug / alcohol abusers / addicts
• Patients on regular opiates /sedative medications

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Associations

• Opioid based anaesthesia / Neuroleptanaesthesia
• Regional anaesthesia Light GA
• Muscle relaxants
• Disconnection / empty vaporiser
• Caesarian section, Trauma, Cardiac bypass

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Stages of Awareness

• Stage 1 Conscious awareness with explicit
  memory
• Stage 2 Conscious awareness without explicit
  memory
• Stage 3 Subconscious awareness with implicit
  memory
• Stage 4 No awareness

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Awareness with explicit memory

• Nearly always associated with neuromuscular
  blocking drug use
• May or may not be associated with pain
• State of awful helplessness
• Patients can go on to develop severe unexplained
  psychiatric disorder

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Awareness without explicit memory

• Tunstall 9/12 pts showed arm movements during
  procedure (IFT) 4/9 appropriately none recalled
• Russell 61 were able to move arm to command
  (given thio/dtc/nitous/oxygen) none recalled
• Changes in BP, pulse, sweating tears were
  shown to be poor indicators of awareness

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Awareness without explicit memory

• 80 of patients induced with Midazolam fentanyl
  and 70 induced with Midazolam Alfentanil
  showed hand movement
• While breathing low doses of Isoflurane (lt0.4
  ET) subjects were able to comprehend and respond
  to words

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Subconscious awareness with implicit memory

• Increasing anaesthetic concentration leads to
  reduction in working memory, then loss of
  conciousness and explicit memory, whereas
  implicit memory of intraop events may remain!!
• Indirect tests of memory must be used to
  demonstrate evidence of implicit memory learning

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Subconscious awareness with implicit memory

• Category generation, free association, stem
  completion tests are used
• Conflicting study results
• Positive suggestions intraop stop smoking,
  faster recovery

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Preventing Awareness

• High risk patients / situations
• Detecting / Monitoring anaesthetic depth intraop
• Drugs
• Avoiding certain anaesthetic techniques
• Patient information

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Detection of Awareness

• Clinical signs
• Clinical experience
• IFT
• Lower oesophageal contractility
• Frontalis EMG
• Respiratory sinus arrhythmia
• EEG
• Raw EEG
• Processed EEG
• BiS
• AEP

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PRST Score
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Isolated Forearm Technique (IFT)

• First used by Tunstall
• Isolate forearm with BP cuff before giving NMB
• Patients asked to squeeze hand for Yes
• Limitations time surgery on the hand
• Even when patients responded, rarely did they
  have any memory of this after the operation

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Monitoring Awareness

• Clinical experience
• Lower oesophageal contractility
• Frontalis EMG
• Heart rate variability (Respiratory sinus
  arrhythmia)

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EEG
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BiS (BiSpectral index monitoring)

• Complex EEG parameter under development by Aspect
  Medical systems since 1985 using clinical data
  from 1500 anaesthetic regimes and 500hrs of EEG
  signals gathered under anaesthetics
• Approved by the FDA in 1996
• Several hundred publications to date

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BiS

• Direct measure of the effects of anaesthetics on
  the brain
• BIS monitoring allows anaesthesia providers to
  administer the appropriate amount of drug that
  each patient needs

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The Bispectral IndexTM (BiS) Aspect Medical
Systems
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Auditory Evoked Potential
Auditory Evoked Potential
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The early cortical AEP waves called Pa and Nb,
which occurs between 20 and 80 ms reflects the
activity in the temporal lobe/primary auditory
cortex ( the site of sound registration) Changes
in the latency of these waves ( in particular
the Nb wave) are highly correlated with a
transition from awake to loss of consciousness
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Mid-latency AEP
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AEP

• Limitations hearing impaired head neck surgery

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Other processed EEG monitors

• Narcotrend Index
• Cerebral state index (CSI)
• Entropy
• Snap index

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Preventing Awareness
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Preventing Awareness
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Dealing with patients who have a history of
Awareness during Anaesthesia

• Take patient seriously
• Investigate previous anaesthetic technique
  circumstances
• Comorbidity / medications
• Reassure
• Sedative premed
• Intraop ET agent monitoring / BiS
• Postop visit
• Good Periop records

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Consequences of unintended awareness during
Anaesthesia

• Fear of Anaesthesia
• Post Traumatic Stress disorder
• Flashbacks, Anxiety, sustained emotional effects
• Anger / litigation
• Paranoia / loss of confidence / financial loss -
  Anaesthesiologist

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• Awake, a 2007 film about anaesthetic awareness
• Anaesthesia, an award-winning horror film about
  anaesthesia awareness
• Return, a Korean thriller movie about anaesthesia
  awareness
• In an episode of Nip/Tuck a woman experiences
  anaesthesia awareness while having surgery to
  repair scarring on her face.
• Wide Awake, a Korean horror/thriller movie was
  mainly about the outcomes mentally after
  anaesthesia awareness.

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Patient associations / support groups
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Dealing with patient who complaints of Awareness
during Anaesthesia

• Dont trivialise the problem take patients
  complaint seriously
• Visit patient as soon as possible, along with a
  witness
• Detailed history modified Brice interview

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Modified Brice Interview

1. What is the last thing you remember before
   surgery?
2. What is the first thing you remember after
   surgery?
3. Do you remember anything happening during
   surgery?
4. Did you have any dreams during surgery?
5. What is the worst thing about your surgery?

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Dealing with patient who complaints of Awareness
during Anaesthesia

• Document patients exact memory
• Attempt to confirm validity of account
• Patient anaesthetic records / theatre
  circumstances
• Try to determine cause
• Reassure / offer explanation / document
• Keep a copy of records
• Offer psychological support
• Notify medical defence / hospital admin /
  patients GP

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Medico legal aspects(American closed claims
database 1971 - 2001)

• Small fraction of patients initiate legal action
• Most of them are women (gt70)
• Cases of intraop awareness with explicit recall
  are difficult to defend
• Awards to patients for awareness with recall
  range from 1000 - 800,000

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"Awareness with analgesia is regrettable
awareness with pain is unforgivable"Thank
you!