title: Relaxant effect of propofol on the airway in dogs.
abstract: Propofol has been suggested to produce airway relaxant effects in vivo, although the mechanism is unclear. We have evaluated the bronchodilating effect of propofol using a direct visualization method with a superfine fibreoptic bronchoscope. We studied 21 mongrel dogs anaesthetized with pentobarbital 30 mg kg-1 i.v. and pancuronium 0.2 mg kg-1 h-1. The animals were allocated randomly to one of three groups (n = 7 in each): propofol group, atropine-propofol group and histamine-propofol group. The trachea was intubated using a tracheal tube that had a second lumen for insertion of the bronchoscope to monitor continuously bronchial cross-sectional area (BCA). BCA was measured using the NIH Image program. In the propofol group, dogs were given the following doses of propofol at 10-min intervals: 0 (saline), 0.2, 2.0 and 20 mg kg-1 i.v. In the atropine-propofol group, saline, atropine 0.2 mg kg-1 and propofol 20 mg kg-1 were given at 10-min intervals. In the histamine-propofol group, bronchoconstriction was elicited with histamine 10 micrograms kg-1 and 500 micrograms kg-1 h-1 until the end of the experiment. Thirty minutes after the start of infusion of histamine, propofol (0, 0.2, 2.0 and 20 mg kg-1) was administered. Changes in BCA were expressed as percentage of basal area. Histamine decreased BCA by 39.2 (SEM 5.4%). Propofol increased significantly basal and histamine-decreased BCA in a dose-dependent manner by 18.4 (4.5%) and 15.8 (4.9%), respectively after 20 mg kg-1 i.v. However, propofol following atropine i.v. did not increase BCA (129.9 (8.2)% after atropine vs 125.7 (8.9)% after propofol). Therefore, the relaxant effect of propofol may be a result of reduction in vagal tone.
authors.affiliation: Department of Anaesthesiology, University of Hirosaki School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hirota
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: Y
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: E
authors.initials: E
authors.lastname: Hashiba
authors.forename: T
authors.initials: T
authors.lastname: Kudo
authors.forename: H
authors.initials: H
authors.lastname: Ishihara
authors.forename: A
authors.initials: A
authors.lastname: Matsuki
mesh_terms: D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001980:Bronchi / Q000187:drug effects*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D001993:Bronchodilator Agents / Q000494:pharmacology; D001999:Bronchoscopy; D004285:Dogs; D005069:Evaluation Studies as Topic; D005336:Fiber Optic Technology; D006632:Histamine / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology*; D011897:Random Allocation
chemical_list: D018686:Anesthetics, Intravenous; D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents; D001285:Atropine; D006632:Histamine; D015742:Propofol