BACKGROUND: Although there is evidence that the volatile anaesthetic desflurane directly relaxes preconstricted airway smooth muscle in vitro, the anaesthetic increases the lung resistance in vivo. The constrictive mechanisms of desflurane are, however, still unknown. This study was conducted to clarify the increasing mechanisms of desflurane on lung resistance by examining the vagal nerve reflexes in guinea pigs. METHODS: The effects of desflurane and sevoflurane on total lung resistance (R(L)) and dynamic lung compliance (C(Dyn)) were investigated in animals that were either untreated, pretreated with atropine or vagotomy, pretreated with the tachykinin receptor antagonists sendide or MEN-10376, or given chronic pretreatment with capsaicin. RESULTS: Desflurane biphasically and dose-dependently increased R(L) (by 180% and 230% at the first and second peaks, respectively, at 2 minimum alveolar concentration) concomitant with a decrease in C(Dyn). However, sevoflurane had little effect on either R(L) or C(Dyn). Although vagotomy partially inhibited the first peak of R(L) by 30%, neither atropine nor vagotomy had any effect on the other respiratory responses to desflurane. Antagonization of tachykinin receptors of airway smooth muscles completely diminished the increase in R(L) induced by desflurane. Desflurane also had little effect on respiratory parameters after the capsaicin pretreatment, in which tachykinin containing afferent C-fibres was desensitized. CONCLUSIONS: Desflurane but not sevoflurane increased R(L) concomitant with a decrease in C(Dyn) in guinea pigs. The increase in lung resistance by desflurane might be due to antidromic tachykinin release from afferent C-fibres but not acetylcholine release from parasympathetic efferent nerves.
BACKGROUND: Although there is evidence that the volatile anaesthetic desflurane directly relaxes preconstricted airway smooth muscle in vitro, the anaesthetic increases the lung resistance in vivo. The constrictive mechanisms of desflurane are, however, still unknown. This study was conducted to clarify the increasing mechanisms of desflurane on lung resistance by examining the vagal nerve reflexes in guinea pigs. METHODS: The effects of desflurane and sevoflurane on total lung resistance (R(L)) and dynamic lung compliance (C(Dyn)) were investigated in animals that were either untreated, pretreated with atropine or vagotomy, pretreated with the tachykinin receptor antagonists sendide or MEN-10376, or given chronic pretreatment with capsaicin. RESULTS:Desflurane biphasically and dose-dependently increased R(L) (by 180% and 230% at the first and second peaks, respectively, at 2 minimum alveolar concentration) concomitant with a decrease in C(Dyn). However, sevoflurane had little effect on either R(L) or C(Dyn). Although vagotomy partially inhibited the first peak of R(L) by 30%, neither atropine nor vagotomy had any effect on the other respiratory responses to desflurane. Antagonization of tachykinin receptors of airway smooth muscles completely diminished the increase in R(L) induced by desflurane. Desflurane also had little effect on respiratory parameters after the capsaicin pretreatment, in which tachykinin containing afferent C-fibres was desensitized. CONCLUSIONS:Desflurane but not sevoflurane increased R(L) concomitant with a decrease in C(Dyn) in guinea pigs. The increase in lung resistance by desflurane might be due to antidromic tachykinin release from afferent C-fibres but not acetylcholine release from parasympathetic efferent nerves.