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Accidental Awareness During General Anaesthesia (AAGA)

Definition & Incidence

• AAGA: Explicit recall of intra-operative events under intended general anaesthesia—e.g., sounds, pressure, pain, paralysis.
• Incidence: Approximately 1:1,000 in structured studies like NAP5, ranging from 1:600 to 1:17,000 depending on methodology.

Sedation Depth Monitoring

Technique	Pros	Cons
Autonomic/Somatic signs (BP, HR, tears)	Readily available	Low specificity
Movement/EMG	Simple	Blocked by NMB, not reliable
Isolated Forearm Technique	Detects consciousness during paralysis	Research tool only
Processed EEG (BIS, Entropy)	Quantifies sedation	Affected by EMG, NMB
Burst suppression	Indicates profound depth	Not protective from awareness

• Key trial: BALANCE trial showed no mortality or major outcome differences by targeting BIS 50 vs 35—even though burst suppression depth varied.

Risk Factors for AAGA

• Emergency or obstetric procedures
• Rapid-sequence induction
• Use of neuromuscular blockers
• Obesity, difficult airway
• Interruption in anaesthetic delivery (e.g., during transport)
• Junior anaesthetist involvement
• Out-of-hours surgery
• Previous awareness
• Cardiac/thoracic surgery
• Young adult age (but not infants)

Clinical Evidence and Trials

Trial	Design	Findings
B‑Aware (2004)	BIS 40–60 vs routine	Awareness 0.17% vs 0.91%; ARR 0.74%, NNT ≈ 697
B‑Unaware (2008)	BIS vs MAC-targeted volatile	No difference in awareness (0.21% both)
BAG‑RECALL (2011)	BIS vs MAC	No significant difference; BIS 0.28%, MAC 0.07%
MACS (2012)	BIS-guided vs routine care	No impact on awareness; trial stopped early
NAP5 (2014)	UK/Ireland survey	Overall incidence ~1:19,600; cardiothoracic procedures ~1:8,333; 41% had lasting psychological impact

Prevention Strategy

Preoperative

• Identify high-risk groups
• Pre-op counselling with reassurance
• Premedicate (e.g., benzodiazepines) to reduce risk (not universally applied

Intraoperative

• Maintain age-adjusted MAC > 0.7
• Use processed EEG (BIS or entropy) for TIVA or NMB cases
• Monitor drug delivery and avoid interruptions
• Titrate NMB closely with objective monitoring
• Use infusion pumps with safety features

Postoperative

• Ask using the Modified Brice questionnaire in PACU and again within 24–72 hours

Management if Awareness Occurs

1. Convene independent witness (colleague)
2. Document event thoroughly
3. Provide psychological support at 24 hours and 2 weeks; consider PTSD referral
4. Report incident as a critical event

Patient Survey: Modified Brice Questions

1. Last memory before sleep?
2. First memory after waking?
3. Any recollection during anaesthesia?
4. Did you dream?
5. Worst part of the experience?

• Helps distinguish awareness vs dreaming and assess patient distress.

Impacts of Awareness

• Short-term: anxiety, nightmares, flashbacks
• Long-term: PTSD, sleep disturbances, fear of future anaesthesia, medical avoidance

Clinical Recommendations

• Use depth-of-anaesthesia monitoring (BIS/entropy) in high-risk cases
• Keep volatile MAC ≥ 0.7 when used
• Ensure safe drug delivery—avoiding disconnections/delays
• Maintain vigilance during induction, emergence, transport phases
• Use postoperative screening (Brice tool) to detect and manage AAGA early

Awareness VIVA

Scenario: Counselling a patient with a past experience of awareness during a surgeon-led gastroscopy under midazolam, now scheduled for a laparoscopic cholecystectomy under general anaesthesia.

1. Building Rapport & Setting the Scene (3 marks)

• Greet the patient, introduce myself and my role as the anaesthetist.
• Explain: “I’d like to talk about your previous experience during your gastroscopy and discuss how we can minimise the risk of anything similar happening again.”
• Acknowledge their prior distress: “I understand that this was very distressing for you, and it’s completely reasonable to feel anxious before your next surgery.”

2. Information Gathering–Previous Event (3 marks)

• Use the Brice Questionnaire (or similar) to explore awareness:
  • “What was the last thing you remember before going to sleep?”
  • “What was the first thing you remember after waking?”
  • “Do you remember anything in between?”
  • “Did you have any dreams or sensations?”
• Clarify that the previous procedure was a surgeon-led gastroscopy using midazolam only, without an anaesthetist.
• Establish what they experienced (e.g., hearing voices, feeling discomfort, anxiety, partial recall).

3. Explains Nature of Prior Event (4 marks)

• Differentiate the event:
  • “It sounds like your experience was due to inadequate sedation rather than true intraoperative awareness under general anaesthesia.”
• Explain contributing factors:
  • “Midazolam causes sedation and some amnesia but doesn’t guarantee complete unconsciousness.”
  • “Because there was no anaesthetist and the sedation may have been light, your awareness was not unexpected.
• Reassure:
  • “You were not given any muscle relaxants or anaesthetic agents that cause full paralysis, so your safety wasn’t compromised in that regard.”

4. Discusses Awareness Under General Anaesthesia (3 marks)

• Define:
  • “Awareness under general anaesthesia refers to a patient becoming conscious during surgery and having recall of events, which can be distressing.”
• Incidence
  • “This occurs in about 1–2 cases per 1000 general anaesthetics.”
• Risk Factors:
  • Previous awareness
  • Equipment malfunction
  • Emergency surgery
  • Hypotension requiring lighter anaesthesia
  • Elderly patients or those with altered physiology
• Acknowledge:
  • “Having experienced awareness before slightly increases your risk, but we can take steps to greatly reduce it.”

5. Preventive Strategies for Upcoming Surgery (3 marks)

• Ensure continuous anaesthetist presence throughout the procedure.
• Use depth of anaesthesia monitoring (e.g., BIS or EEG-based monitoring) to titrate drug delivery.
• Conduct thorough equipment checks, ensure alarms are functioning, and confirm drug availability.
• Provide adequate analgesia and amnestic drugs.
• Arrange postoperative follow-up to address any concerns

6. Communication Skills (4 marks)

• Use open-ended questions: “How has this experience affected your confidence in undergoing surgery again?”
• Reflective listening and empathy: “It’s completely understandable to feel nervous—what you went through was very real.”
• Avoid minimising language (e.g., not saying “That’s rare, don’t worry”).
• Use simple language:
  • “We’ll be closely watching your brain activity to ensure you’re deeply asleep.”
• Check understanding regularly: “Does that make sense so far? Any part you’d like me to explain more?”

7. Handles Patient Questions & Concerns (3 marks)

• “Will it happen again?”
  • “The risk is low, and we are taking several steps to ensure it doesn’t.”
• “How will you know I’m asleep?”
  • “We use monitors that assess depth of sleep and constant clinical observation.”
• “What if the equipment fails?”
  • “We regularly test all equipment, and we have backups and alarms for every critical system.”
• Offer pre-medication (e.g., anxiolytics) or psychological support if desired.
• Acknowledge uncertainty when appropriate: “There is always a very small risk, but I’ll do everything I can to minimise it.”
• Offer further resources: “I can provide written information or refer you for a second opinion if you wish.”

8. Structure & Professionalism (2 marks)

• Logical and clear structure:
  • Set the agenda → gather history → explain past → outline risks → propose strategy → answer concerns → summarise.
• Summarise:
  • “To summarise: your previous experience was likely due to light sedation without anaesthetic drugs. Your upcoming surgery will be different—we’ll provide continuous monitoring, deeper anaesthesia, and post-op follow-up.”
• Invite further questions:
  • “Do you have any other concerns you’d like to talk about?”
• Thank the patient for their time and openness.

BART

BE-UNAWARE

Links

• Bispectral Index (BIS)
• Geriatrics
• Morbidity and mortality in Anaesthesia

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References:

1. Tasbihgou, S. R., Vogels, M. F., & Absalom, A. (2017). Accidental awareness during general anaesthesia–a narrative review. Anaesthesia, 73(1), 112-122. https://doi.org/10.1111/anae.14124
2. Kim, M. C., Fricchione, G. L., & Akeju, O. (2021). Accidental awareness under general anaesthesia: incidence, risk factors, and psychological management. BJA Education, 21(4), 154-161. https://doi.org/10.1016/j.bjae.2020.12.001
3. Pandit JJ, Cook TM, Jonker WR, et al. NAP5: Accidental awareness under general anaesthesia in the UK and Ireland. Anaesthesia. 2014;69(6):523–531.
4. Myles PS, Leslie K, McNeil J, et al. BIS versus MAC for awareness prevention (BAG-RECALL). N Engl J Med. 2011;365(7):591–600.
5. Avidan MS, Zhang L, Burnside BA, et al. Anesthesia awareness and BIS (B‑Aware). N Engl J Med. 2004;350:637–646.
6. Monk TG, Saini V, Weldon BC, Sigl JC. Intraoperative Bispectral Index monitoring and awareness (B‑Unaware). Anesthesiology. 2008;109(3):613–620.
7. Abend NS, Stain SC. PTSD after awareness under anesthesia. Anesthesiology. 2015;122(2):416–417.
8. Bouafif‑Bossert MY, Bohnen NI. Depth of anesthesia monitoring: BIS and processed EEG in anaesthetic practice. BJA Educ. 2021;21(5):175–184.
9. Everitt SJ, Management of intraoperative awareness. AAGBI Safety Guideline. 2020.

Summaries:
Awareness
EEG

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© 2025 Francois Uys. All Rights Reserved.

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