FRCA Notes

Accidental Awareness Under General Anaesthesia

AAGA featured as part of a joint AAGA/TIVA CRQ in the September 2022 exam (22% pass rate).

A CRQ solely on AAGA featured in the September 2024 exam; marks were lost on the 'EEG characteristics with propofol anaesthesia and the NAP5 tool to grade awareness'.

Resources

Awareness under general anaesthesia is the ability to perceive, feel or be consciously aware of one's surroundings ± the feeling of pain

  • It is a rare, but serious complication of anaesthetic care
  • May take the form of:
    • Explicit memory/recall - the intentional recollection of events with conscious perception
    • Implicit memory/recall - the non-intentional recollection of events with sub-conscious perception
  • It may have serious psychological sequelae
    • 43% of those experiencing AAGA will develop symptoms that fit diagnostic criteria for PTSD
    • Nearly 75% of cases of AAGA were deemed preventable by NAP5

  • Incidence has remained steady despite advances in monitoring and understanding of the mechanisms underlying anaesthesia
  • The overall incidence according to NAP5 was 1 in 19,000
  • This figure is highly changeable based on factors such as:
    • Presence (1 in 8,000) or absence (1 in 136,000) of NMBA
    • Surgery performed e.g. LSCS (1 in 670) or cardiothoracic surgery (1 in 8,600)


Patient factors Anaesthetic factors Surgical factors
Female gender Use of an RSI technique Obstetric surgery
Previous AAGA Use of NMBA Cardiothoracic surgery
Young adults Thiopentone Neurosurgery
Obesity TIVA technique OOH surgery
↑ reistance to anaesthetic agents Inadequate MAC Emergency surgery
Difficult airway Drug error (10% of all reports)
Junior anaesthetist

  • 65-75% of AAGA occurs in females - gender susceptibility or reporting bias?
  • Increased resistance to anaesthetic agents may be from hypermetabolic state (febrile, hyperthyroid) or other resistance (chronic EtOH or recreational drugs)

Timing of awareness

  • 2/3rds of cases happened during either induction or emergence
  • During transfer e.g. anaesthetic room to theatre, theatre to ICU

AAGA during TIVA

  • The commonest causes of AAGA during TIVA were:
    1. Failure to deliver the intended dose of drug
      • Propofol syringe in remifentanil-programmed TCI pump
      • Cannula-related issues
      • Inappropriatley low rate of fixed-rate propofol infusion inc. during volatile-to-TIVA changeover
      e.g. propofol syringe in remi-programmed TCI pump, cannula-related issues
    2. Poor understanding of the underlying pharmacological principles

  • Given the association between NMBA, TIVA and AAGA, one should:
    • Use pEEG whenever NMBA used with TIVA
    • Commence pEEG monitoring prior to administration of NMBA
    • Continue monitoring until full reversal as assessed by quantitative ToF

  • This is a serious situation with potentially devastating consequences to the patient and anaesthetist
  • NAP5 found that 41% of patients with AAGA experienced moderate-severe long-term sequelae
  • Active, early support for the patient was often followed by good outcomes

    • Steps if a complaint of AAGA is made

  • Seek senior (consultant) advice
  • Visit the patient as soon as possible with a consultant present
    • Full history to elicit exact nature of the awareness and their sensation inc. presence of pain
    • Document the conversation
  • Review medical and anaesthetic notes to ascertain cause
  • Full explanation to patient; be sympathetic and apologise if true AAGA suspected

  • Offer:
    • Follow-up
    • Psychological support
    • Reassurance it won't happen again
  • There is a lack of evidence base over best treatment - ?SSRI's

  • Fill in a critical incident form
  • Inform GP, hospital administrator and MPS
  • Debrief with consultant to check what could have been done differently