Presentation on theme: "Preventing and Managing the impact of Awareness during Anaesthesia"— Presentation transcript:
1Preventing 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
2Awareness during Anaesthesia DefinitionBrief historyIncidenceCausesAssociationsStagesPrevention:Detecting AwarenessPreventing AwarenessConsequences of intra-op awarenessPTSDPublic awarenessDealing with patients who complain of awareness during anaesthesiaMedico legal aspects
3DefinitionAwareness 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)
41895Horace Wells attempted to demonstrate N2O to physicians at MGH, BostonPatient moved & cried out!Surgeons considered the demonstration a failurePatient had no recall of his operation
51896 W.T.G. Morton demonstrated the use of Ether in the same venue Patient did not moveSurgeons considered it a ground breaking success!Morton’s patient Gilbert Abbot, reported that he had been aware during his surgery, while experiencing no pain
61943 Muscle relaxants came into clinical use Anaesthetists started giving lesser amount of anaesthetic agents
7Levinson 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 hypnosis4/10 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
8Levinson studyObvious methodological flaws: no controls, non-randomisation, absence of double blind study, asking leading questionsThirty years later, Levinson repeated this study but failed to replicate his original findings!
10General Anaesthesia is not an all or nothing phenomenon!
11Incidence of Awareness Reported incidence of awareness varies and is difficult to determineSwedish study: 0.06%American academic centres: 0.13%Overall incidence: ~0.2%Conscious awareness with pain: 1 in 20,000 – 40,000 anaesthetics
16Stages of Awareness Stage 1: Conscious awareness with explicit memory Stage 2: Conscious awareness without explicit memoryStage 3: Subconscious awareness with implicit memoryStage 4: No awareness
17Awareness with explicit memory Nearly always associated with neuromuscular blocking drug useMay or may not be associated with pain‘State of awful helplessness’Patients can go on to develop severe unexplained psychiatric disorder
18Awareness without explicit memory Tunstall: 9/12 pts showed arm movements during procedure (IFT) 4/9 appropriately – none recalledRussell: 61% were able to move arm to command (given thio/dtc/nitous/oxygen) – none recalledChanges in BP, pulse, sweating & tears were shown to be poor indicators of awareness
19Awareness without explicit memory 80% of patients induced with Midazolam & fentanyl and 70% induced with Midazolam & Alfentanil showed hand movementWhile breathing low doses of Isoflurane (<0.4% ET) subjects were able to comprehend and respond to words
20Subconscious 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
21Subconscious awareness with implicit memory Category generation, free association, stem completion tests are usedConflicting study resultsPositive suggestions intraop: stop smoking, faster recovery
22Preventing Awareness ‘High’ risk patients / situations Detecting / Monitoring anaesthetic depth intraopDrugsAvoiding certain anaesthetic techniquesPatient information
25Isolated Forearm Technique (IFT) First used by TunstallIsolate forearm with BP cuff before giving NMBPatients asked to squeeze hand for ‘Yes’Limitations: time; surgery on the handEven when patients responded, rarely did they have any memory of this after the operation
28BiS (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 anaestheticsApproved by the FDA in 1996Several hundred publications to date
29BiS 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
30The Bispectral IndexTM (BiS) Aspect Medical Systems
33The 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
40Dealing with patients who have a history of Awareness during Anaesthesia Take patient seriouslyInvestigate previous anaesthetic technique & circumstancesComorbidity / medicationsReassureSedative premedIntraop ET agent monitoring / BiSPostop visitGood Periop records
42Consequences of unintended awareness during Anaesthesia Fear of AnaesthesiaPost Traumatic Stress disorderFlashbacks, Anxiety, sustained emotional effectsAnger / litigationParanoia / loss of confidence / financial loss - Anaesthesiologist
44Awake, a 2007 film about anaesthetic awareness Anaesthesia, an award-winning horror film about anaesthesia awarenessReturn, a Korean thriller movie about anaesthesia awarenessIn 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.
46Dealing with patient who complaints of Awareness during Anaesthesia Don’t trivialise the problem – take patient’s complaint seriouslyVisit patient as soon as possible, along with a witnessDetailed history – modified Brice interview
47Modified 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?
48Dealing with patient who complaints of Awareness during Anaesthesia Document patient’s exact memoryAttempt to confirm validity of accountPatient anaesthetic records / theatre circumstancesTry to determine causeReassure / offer explanation / documentKeep a copy of recordsOffer psychological supportNotify medical defence / hospital admin / patient’s GP
49Medico legal aspects (American closed claims database: 1971 - 2001) Small fraction of patients initiate legal actionMost of them are women (>70%)Cases of intraop awareness with explicit recall are difficult to defendAwards to patients for awareness with recall range from $ $800,000