Portal de Periódicos da CAPES

Relaxation of proximal and distal isolated human bronchi by halothane, isoflurane and desflurane

2002; European Respiratory Society; Volume: 20; Issue: 2 Linguagem: Inglês

10.1183/09031936.02.00275702

1399-3003

F.J. Mercier, Emmanuel Naline, Maine Luellah Demaret Bardou, O. Georges, A. Denjean, D. Benhamou, Charles Advenier,

Asthma and respiratory diseases

Volatile anaesthetics relax airway smooth muscle in vitro . The amount of relaxation might depend on the type and concentration of volatile anaesthetics, the calibre and precontraction level of the bronchi, and also on the species considered. These effects were investigated on isolated human bronchi. Isometric relaxations produced by halothane, isoflurane and desflurane bubbled on human bronchial rings precontracted with carbachol were recorded and compared with time controls. Volatile anaesthetics induced a concentration-dependent relaxation at 0.66, 1.33 and 2 minimum alveolar concentration (MAC). The relaxation was greater in mildly (carbachol 3×10 −7 M) than in highly (carbachol 2×10 −6 M) precontracted bronchi. Halothane was more potent in relaxing distal as compared to proximal bronchi; this differential effect was less pronounced with isoflurane and not observed with desflurane. While the three volatile anaesthetics induced similar relaxation on proximal bronchi, halothane was significantly more potent than desflurane on distal bronchi, with isoflurane being intermediate. The relaxation induced by 1.33 MAC of halothane, isoflurane and desflurane on moderately precontracted distal bronchi (carbachol 1×10 −6 M) was attenuated by pretreatment with glibenclamide 1×10 −5 M. In conclusion, halothane, isoflurane and desflurane exert direct but differential relaxant effects on human isolated bronchial smooth muscle. This may provide supplemental bronchodilation during anaesthesia. Although adenosine triphosphate-sensitive K + channels are involved in these relaxant effects, they are unlikely to explain the observed differences between the three volatile anaesthetics.