Awareness under general anaesthesia

What “awareness” means

Accidental awareness with recall is postoperative memory of events during intended general anaesthesia. It is distinct from dreaming or brief recall during emergence.

How common is it?

Many reviews quote an incidence around 1–2 per 1,000 general anaesthetics, though estimates vary by population and methodology.

Who is at higher risk?

• Emergency surgery, trauma, obstetrics (where dose may be limited by physiology)
• Very sick patients where deep anaesthesia is avoided due to low blood pressure
• TIVA if infusion is interrupted or under-dosed
• History of awareness, substance tolerance, or certain high-risk surgeries

BIS / processed EEG monitoring

BIS and related monitors use EEG features to estimate depth of hypnosis. They can help titrate anaesthesia and may reduce awareness in some high-risk settings, but they are not perfect: artifacts, drug-specific effects, and individual variability can mislead.

Cost-benefit framing

• Potential benefit: better titration, potentially fewer episodes of overly light anaesthesia in selected cases.
• Costs: disposable sensors, equipment, and staff workflow.
• Best use: higher-risk awareness situations, complex TIVA cases, or when minimizing anaesthetic dose is desired.