Comparison of the sedative, cognitive, and analgesic effects of nitrous oxide, sevoflurane, and ethanol.
BACKGROUND
Anaesthetics which work by different mechanisms may have different patterns of effect. Measurement of these patterns thus may elucidate their mechanisms of action and allow therapeutic choices between the agents.


METHODS
We compared the effects of ethanol (approximately 80 mg per 100 ml), and different end-tidal concentrations of nitrous oxide (15% and 25%) and sevoflurane (0.3% and 0.5%) in volunteers. We measured speed and accuracy in psychomotor tests, reaction time and memory, touch and pain sensitivity to von Frey filaments, and subjective mood for a range of descriptors.


RESULTS
All treatments caused the same degree of overall abnormal feelings, but sevoflurane caused more obtunding (subjective drowsiness, slow reaction times, and loss of memory function) and nitrous oxide was more analgesic. Ethanol caused a marked feeling of drunkenness, but little drowsiness or analgesia.


CONCLUSIONS
In the same volunteer subjects, direct comparison of sub-anaesthetic doses of these agents showed a clear and characteristic pattern of effects. These support the possible mechanisms for these disparate agents and may help choose appropriate agents for specific desired anaesthetic outcomes such as sedation or analgesia.
Duarte
R
R
Department of Neuroscience, 1 George Square, Edinburgh EH8 9JZ, UK.
McNeill
A
A
Drummond
G
G
Tiplady
B
B
D000328:Adult; D000339:Affect / Q000187:drug effects; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D003071:Cognition / Q000187:drug effects*; D016292:Procedural Sedation; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects; D008738:Methyl Ethers / Q000494:pharmacology; D009609:Nitrous Oxide / Q000494:pharmacology; D010147:Pain Measurement / Q000379:methods; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D000431:Ethanol; D009609:Nitrous Oxide