Learning objectives

• Describe the implications and risk factors of awareness during anesthesia
• Prevent awareness during anesthesia
• Diagnose and manage patients who experienced awareness during anesthesia

Definition & mechanisms

• Rare but severe complication of anesthetic care
• Also referred to as “accidental awareness during general anesthesia” (AAGA)
• Mostly occurs during induction and emergence
• Can range from only auditory or tactile awareness to being fully awake with paralysis and pain
• Traumatic experience with possibly severe long-term effects (post-traumatic stress disorder)

Risk factors

• Neuromuscular blocking
• Female gender
• Pregnancy
• Cardiothoracic patients
• Obesity
• Total intravenous anesthesia
• Trauma & emergency surgery
• Ketamine, etomidate, and thiopental use
• Difficult intubation
• History of AAGA
• Chronic drug use
• Lack of monitoring

Psychological assessment and diagnosis

• Acute stress disorder (ASD): Occurs shortly after traumatic event (3 days to 1 month)
  • Diagnosis: at least 9 of the following symptoms:
    • Recurring, uncontrollable, and intrusive distressing memories of the event
    • Recurring nightmares of the event
    • Flashbacks of the event
    • Intense psychological or physical distress when reminded of the event 
    • Persistent inability to experience positive emotions 
    • Altered sense of reality 
    • Memory loss for an important part of the traumatic event
    • Efforts to avoid distressing memories, thoughts, or feelings associated with the event
    • Efforts to avoid external reminders associated with the event
    • Disturbed sleep
    • Irritability or angry outbursts
    • Hypervigilance
    • Concentration difficulties
    • Exaggerated startle response
• Post-traumatic stress disorder (PTSD): Diagnosed when symptoms persist for more than 1 month after the traumatic event

Prevention

• Check equipment and medications
• Depth of anesthesia monitoring (EEG is superior to BIS)
• Avoid or minimize the use of neuromuscular blocking agents
• Monitor neuromuscular block if neuromuscular blocking is necessary
• Use target-controlled infusion for total IV anesthesia

Management

Management is based on treating psychological symptoms:

• Early face-to-face postoperative meeting with the patient and consultation with a psychiatrist or psychologist
• Psychological interventions (e.g, cognitive behavioral therapy)
• Antidepressants
• Benzodiazepines for acute anxiety (beware of potential abuse)
• Antipsychotics may be helpful in some patients

Suggested reading

• Kim MC, Fricchione GL, Akeju O. Accidental awareness under general anaesthesia: Incidence, risk factors, and psychological management. BJA Education. 2021;21(4):154-61.
• Mashour GA, Avidan MS. Intraoperative awareness: controversies and non-controversies. Br J Anaesth. 2015;115 Suppl 1:i20-i26. 
• Tasbihgou SR, Vogels MF, Absalom AR. Accidental awareness during general anaesthesia – a narrative review. Anaesthesia. 2018;73(1):112-22.
• Mashour GA, Orser BA, Avidan MS, Warner DS. Intraoperative Awareness: From Neurobiology to Clinical Practice. Anesthesiology. 2011;114(5):1218-33.

Clinical updates

Jiang et al. (Anesthesiology, 2024) argue that current depth-of-anesthesia tools based on responsiveness and population-derived EEG indices (e.g., BIS, MAC) do not reliably measure true consciousness, leaving patients at risk for covert awareness despite adequate dosing. They propose “disconnected consciousness” as the optimal anesthetic target state and highlight emerging approaches, including brain connectivity metrics, transcranial stimulation paradigms, and AI-driven EEG analysis (with reported accuracy up to ~95.9% for classifying conscious states), as promising strategies to better detect and prevent intraoperative awareness.

• Read more about this study HERE.