Awareness: Monitoring versus remembering what happened

Area of Science:

• Anesthesiology
• Neuroscience
• Surgical Monitoring

Background:

• Postoperative interviews may underestimate awareness during anesthesia.
• Current monitoring like Bispectral Index (BIS) and verbal command response are not always standard.
• This study examined awareness during deep sedation (BIS 60-70) and monitoring effectiveness.

Purpose of the Study:

• To investigate patient response to command during deep sedation.
• To evaluate the ability of current monitoring techniques to indicate awareness.
• To assess the prediction of recall using intra-anesthetic monitoring.

Main Methods:

• Used the isolated forearm technique to assess response to command in 56 surgical patients.
• Monitored electroencephalographic (EEG) and hemodynamic variables during propofol-alfentanil infusion.
• Assessed conscious recall via structured interviews post-recovery.

Main Results:

• 82% of commands received no response, 5% equivocal, and 13% unequivocal response (awareness).
• 25% of patients with awareness reported recall; insights gained for management.
• BIS and EEG parameters predicted awareness (P < 0.0001); hemodynamics did not.
• EEG parameters did not predict recall, but heart rate and command responsiveness did.

Conclusions:

• Conscious recall underestimates the incidence of intra-anesthetic awareness.
• Behavioral and neurophysiologic measures can monitor awareness in real-time.
• Feedback during awareness can help patients manage stressful intra-anesthetic experiences.