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Awareness Under Anesthesia 

 

 

Background

 

  • Also referred to as "accidental awareness during general anesthesia" (AAGA)

  • Most occur during induction & emergence, less during maintenance

  • Range from auditory to being full awake and in pain

  • Patients may suffer from PTSD-like symptoms afterwards

 

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Considerations

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  • Rare event (1 in 1000 anesthetics) --> incidence can be reduced by certain measures but not eradicated completely

  • Risk factors

    • Use of NMBA - biggest risk factor

    • TIVA

    • Trauma & Emergency surgery, Cardiac surgery with CPB, C-section

    • Difficult intubation

    • Obesity

    • Personal & Family Hx

    • Chronic drug use (EtOH, opioids, benzos)

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Prevention 

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  • Manage patient expectations (explain GA vs MAC)

  • Recognize HR and BP alone are unreliable for determining anesthetic depth

  • Avoid muscle relaxants if possible, otherwise use twitch monitor

  • Consider use of BIS, raw EEG is even better

  • End-tidal monitoring of volatile agents

    • Aim for MAC>0.7

    • Provides safety margin b/c MAC-movement > MAC-awake & MAC-amnesia

  • Use target-controlled infusion (TCI) for TIVA

  • Use isolated forearm technique

    • Before NMBA given, tourniquet applied to a forearm, so that later an aware patient can alert team

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Management 

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  • If AAGA has suspected to have occured:

      • Give benzodiazepines for amnesia, opioids or other analgesics for pain

      • Discuss event with patient afterwards for reassurance & potential further counselling

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References 

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  • Pandit, JJ. Accidental awareness after general anesthesia. In: UpToDate, Joshi, GP (Ed), UpToDate, Waltham, MA, 2023.

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