Propofol and methohexital have no significant effect on mucus secretion orclearance in the anesthetized dog

Objective: Anecdotal reports suggest that propofol (Diprivan) may stimulate mucus hypersecretion in patients without pulmonary disease. The purpose of this study was to evaluate the effect of methohexital or propofol anesthes ia on the physical and transport properties of airway mucus in spontaneousl y breathing dogs. Design: Randomized, controlled, crossover laboratory study. Setting: University laboratory. Subjects: Four healthy, purpose-bred female beagle dogs. Interventions: Dogs were anesthetized with 5 mg/kg of propofol by intraveno us bolus followed by a maintenance infusion at 0.4 mg kg(-1).min(-1) or 4 m g/kg of methohexital followed by an infusion at 0.3 mg.kg(-1).min(-1). Prem edication with 0.05 mg/kg of acepromazine was given, and either atropine (0 .2 mg) or saline was given by intravenous bolus at the time of induction. D ogs were intubated but spontaneously breathing throughout the experiment. T racheal secretions were collected after induction and again after 40 mins. Measurements and Main Results: The volume of secretions collected on the en dotracheal tube during the 1.5-hr experiment and on a bronchoscopy brush ov er 10 mins during the experiment was measured. Tracheal epithelial potentia l difference was measured bronchoscopically by saturated agar bridges, and tracheal mucus transport velocity was determined by timing particle transpo rt. The dynamic viscoelasticity of collected mucus was assessed by microrhe ometry, and secretion mucociliary transportability was measured in vitro. T here were no differences in any physical or transport properties of airway secretions that could be attributed to the anesthetic agent. Secretion volu me was significantly lower (p < .05) and epithelial potential difference wa s significantly higher (p = .03) with atropine premedication. Despite this, there were no differences in tracheal mucus transport velocity, viscoelast icity, or secretion mucociliary transportability with either anesthetic age nt or with atropine. Conclusions: This study suggests that neither methohexital nor propofol sig nificantly affects mucus secretion or clearance in healthy dogs.