Preventing and Managing the impact of Awareness during Anaesthesia

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 • 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

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 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 $1000 - $800,000