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Bispectral EEG index during nitrous oxide administration
I J Rampil1, J S Kim, R Lenhardt
1Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0648, USA. ira_rampil@vaxine.ucsf.edu
Anesthesiology
|September 22, 1998
Summary
Nitrous oxide (N2O) showed some EEG changes but did not significantly alter sedation levels or the Bispectral Index (BIS) in healthy adults, indicating it is a weak sedative.
Area of Science:
- Anesthesiology and Pharmacology
- Neuroscience and Electrophysiology
Background:
- Nitrous oxide (N2O) is a common sedative for medical and dental procedures.
- Understanding its precise sedative effects on quantitative EEG measures is crucial.
Purpose of the Study:
- To investigate the impact of varying nitrous oxide (N2O) concentrations on quantitative electroencephalographic (EEG) variables.
- To assess the correlation between N2O administration and the Bispectral Index (BIS) as a measure of sedation.
Main Methods:
- Healthy volunteers (n=13) received graded concentrations of N2O (10-50%) via face mask.
- Continuous EEG monitoring was performed, with sedation assessed using the Observer Assessment of Alertness/Sedation (OAA/S) scale.
Main Results:
- 50% N2O increased theta, beta, and specific high-frequency EEG band powers.
- No significant changes in BIS or OAA/S scores were observed at tested N2O concentrations.
- Transient EEG slowing occurred with abrupt N2O concentration decreases.
Conclusions:
- Nitrous oxide (N2O) exhibits weak sedative properties at concentrations up to 50%, as evidenced by maintained cooperation and responsiveness.
- EEG spectral content changes indicate a pharmacologic effect, but the stable BIS suggests it accurately reflects a lack of deep hypnosis.