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Preventing and Managing the impact of Awareness during Anaesthesia

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Presentation on theme: "Preventing and Managing the impact of Awareness during Anaesthesia"— Presentation transcript:

1 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

2 Awareness during Anaesthesia
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

3 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)

4 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

5 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! Morton’s patient Gilbert Abbot, reported that he had been aware during his surgery, while experiencing no pain

6 1943 Muscle relaxants came into clinical use
Anaesthetists started giving lesser amount of anaesthetic agents

7 Levinson study (1965) 10 pts undergoing dental extraction with ether; shortly after induction, the anaesthetist called to the surgeon ‘STOP THE OPERATION, I don’t like the patient’s 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

8 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!


10 General Anaesthesia is not an all or nothing phenomenon!

11 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

12 Incidence of Awareness
Cardiac surgery: 1 – 1.5% Trauma surgery: 11 – 43% Cesarian section: 0.4%

13 Causes Lack of complete understanding of kinetics & dynamics of drugs
Induction of anaesthesia: Coughing difficult intubation

14 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

15 Associations Opioid based anaesthesia / Neuroleptanaesthesia
Regional anaesthesia & ‘Light’ GA Muscle relaxants Disconnection / empty vaporiser Caesarian section, Trauma, Cardiac bypass

16 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

17 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

18 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

19 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 (<0.4% ET) subjects were able to comprehend and respond to words

20 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

21 Subconscious awareness with implicit memory
Category generation, free association, stem completion tests are used Conflicting study results Positive suggestions intraop: stop smoking, faster recovery

22 Preventing Awareness ‘High’ risk patients / situations
Detecting / Monitoring anaesthetic depth intraop Drugs Avoiding certain anaesthetic techniques Patient information

23 Detection of Awareness
Clinical signs Clinical experience IFT Lower oesophageal contractility Frontalis EMG Respiratory sinus arrhythmia EEG Raw EEG Processed EEG BiS AEP

24 PRST Score

25 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

26 Monitoring Awareness…
Clinical experience Lower oesophageal contractility Frontalis EMG Heart rate variability (Respiratory sinus arrhythmia)

27 EEG

28 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

29 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

30 The Bispectral IndexTM (BiS) Aspect Medical Systems


32 Auditory Evoked Potential

33 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

34 Mid-latency AEP


36 AEP Limitations: hearing impaired; head & neck surgery

37 Other processed EEG monitors
Narcotrend Index Cerebral state index (CSI) Entropy Snap index

38 Preventing Awareness

39 Preventing Awareness

40 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


42 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


44 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.

45 Patient associations / support groups

46 Dealing with patient who complaints of Awareness during Anaesthesia
Don’t trivialise the problem – take patient’s complaint seriously Visit patient as soon as possible, along with a witness Detailed history – modified Brice interview

47 Modified Brice Interview
What is the last thing you remember before surgery? What is the first thing you remember after surgery? Do you remember anything happening during surgery? Did you have any dreams during surgery? What is the worst thing about your surgery?

48 Dealing with patient who complaints of Awareness during Anaesthesia
Document patient’s 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 / patient’s GP

49 Medico legal aspects (American closed claims database: 1971 - 2001)
Small fraction of patients initiate legal action Most of them are women (>70%) Cases of intraop awareness with explicit recall are difficult to defend Awards to patients for awareness with recall range from $ $800,000


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

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