Desflurane and nitrous oxide, but not nonimmobilizers, affect nociceptive responses.
Nonimmobilizers (previously called nonanesthetics) do not prevent movement in response to a noxious stimulus, even at doses predicted to produce anesthesia. We hypothesized they would also lack antinociceptive effects. We tested this prediction using the tail-flick latency (TFL) test. As predicted, the two nonimmobilizers tested (1,2-dichlorohexafluorocyclobutane and perfluoropentane) did not alter TFL, whereas desflurane and nitrous oxide both lengthened TFL (nitrous oxide at a lower minimum alveolar anesthetic concentration [MAC]-multiple than desflurane). In addition, we found that 0.1 MAC desflurane had a hyperalgesic effect (shortened TFL).


CONCLUSIONS
We studied the response of animals inhaling anesthetics or nonimmobilizers (compounds predicted to be anesthetics from the Meyer-Overton relation) to painful stimuli. Nonimmobilizers had no effect on these responses; at a low partial pressure, desflurane was hyperalgesic; nitrous oxide and, at higher partial pressures, desflurane were antinociceptive.
Sonner
J
J
Department of Anesthesia, University of California-San Francisco, 94143-0464, USA. jim_sonner@quickmail.ucsf.edu
Li
J
J
Eger
E I
EI
D000818:Animals; D017402:Chlorofluorocarbons / Q000494:pharmacology*; D003503:Cyclobutanes / Q000494:pharmacology*; D000077335:Desflurane; D004305:Dose-Response Relationship, Drug; D005466:Fluorocarbons / Q000494:pharmacology*; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D009609:Nitrous Oxide / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D051381:Rats; D013047:Specific Pathogen-Free Organisms; D010420:Pentanes
D017402:Chlorofluorocarbons; D003503:Cyclobutanes; D000077335:Desflurane; D005466:Fluorocarbons; D007530:Isoflurane; D009609:Nitrous Oxide; C090640:1,2-dichloro-1,2,3,3,4,4-hexafluorocyclobutane; C008806:perfluoropentane; D010420:Pentanes