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Auditory information processing during adequate propofol anesthesia monitored by electroencephalogram bispectral
C Kerssens1, J Klein, A van der Woerd
1Department of Medical Psychology and Psychotherapy, Netherlands Institute of Health Sciences, Erasmus University Rotterdam, P.O. Box 1738, NL-3000 DR, Rotterdam, the Netherlands. kerssens@mpp.fgg.eur.nl
Anesthesia and Analgesia
|April 27, 2001
Summary
Adequate anesthesia using the bispectral index (BIS) monitor (40-60) may prevent intraoperative memory formation in surgical patients. This study found no explicit or implicit memory of auditory stimuli during monitored anesthesia.
Area of Science:
- Anesthesiology
- Neuroscience
- Cognitive Psychology
Background:
- Intraoperative awareness and memory can occur with inadequate anesthesia.
- Continuous monitoring of the hypnotic state is crucial for adequate anesthesia.
- Electroencephalogram bispectral index (BIS) monitoring helps maintain anesthesia at target levels (BIS 40-60).
Purpose of the Study:
- To investigate memory formation in elective surgical outpatients under target-controlled propofol anesthesia.
- To assess the impact of adequate hypnosis (BIS 40-60) on explicit and implicit memory.
- To evaluate the role of BIS monitoring in preventing intraoperative memory.
Main Methods:
- Target-controlled propofol anesthesia supplemented with alfentanil was used in 82 elective surgical outpatients.
- Patients listened to familiar word exemplars (Experimental group) or bird sounds (Control group) while BIS remained between 40 and 60.
- Post-recovery memory was assessed using direct recall and indirect tests (category exemplar generation).
Main Results:
- No patients consciously recalled intraoperative events.
- No significant difference in word recognition or category exemplar generation between groups.
- No explicit or implicit memory effect was found for words presented during adequate anesthesia (BIS 40-60).
Conclusions:
- Stable, adequate hypnosis (BIS 40-60) appears to prevent information processing and memory formation during general anesthesia.
- Electroencephalogram bispectral index (BIS) monitoring is a feasible tool for ensuring adequate anesthesia levels.
- Maintaining BIS between 40 and 60 may prevent intraoperative awareness and memory in surgical patients.