Synergistic antinociceptive interaction between sevoflurane and intrathecal fentanyl in dogs.
This study determined the nature of the antinociceptive interaction between sevoflurane and intrathecal fentanyl on somatosympathetic reflexes in anaesthetized dogs. Afferent A delta- and C-fibre-mediated somatosympathetic reflexes, evoked by supramaximal electrical stimulation of tibial nerves, were recorded from renal sympathetic nerves. The effect of fentanyl alone, administered intrathecally (i.t.) in incremental doses from 2 to 64 micrograms, was compared with the effect of the same doses during the administration of 1.5% sevoflurane. The mean ED50s for the depressant effect of fentanyl (i.t.) on A delta and C reflexes were 35.6 micrograms and 14.2 micrograms while 1.5% sevoflurane, when administered alone, depressed them by 15.5% (P < 0.05) and 27.5% (P < 0.01) respectively. During the administration of 1.5% sevoflurane, the mean ED50s of fentanyl (i.t.) for the depression of A delta and C reflexes were reduced by 76% and 75%, to 8.5 micrograms and 3.5 micrograms respectively. The combined antinociceptive effects of sevoflurane and intrathecal fentanyl were not additive but exhibited a high degree of synergistic interaction.
Department of Anaesthetics and Intensive Care, Imperial College School of Medicine, Hammersmith Hospital, London.
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D
Ma
S M
SM
Sapsed-Byrne
M K
MK
Chakrabarti
J G
JG
Whitwam
D000701:Analgesics, Opioid / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004558:Electric Stimulation; D005283:Fentanyl / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008738:Methyl Ethers / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects*; D012018:Reflex / Q000187:drug effects; D000077149:Sevoflurane; D013564:Sympathetic Nervous System / Q000187:drug effects
D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D005283:Fentanyl