Is isoflurane hyperalgesia modulated by nicotinic inhibition?
Since hyperalgesia occurs in vivo at isoflurane doses that antagonize nAChRs in vitro, is prevented by a nicotinic agonist, and is mimicked and potentiated by nicotinic antagonists, the authors conclude that isoflurane inhibition of nAChRs activation is involved in the pathway that causes hyperalgesia. At subanesthetic doses, isoflurane can either enhance pain responses (produce hyperalgesia) or be analgesic (antinociceptive). In rats, low volatile anesthetic concentrations (0.1-0.2 minimum alveolar concentration [MAC]) elicit hyperalgesia, while 0.4-0.6 MAC elicits antinociception.
ISO pretreatment induces hepatic HO-1 mRNA and protein followed by an increase in HO activity, thereby reducing portal resistance. These findings indicate a beneficial effect of ISO on hepatic hemodynamics in vivo.