Propofol and methohexital have no significant effect on mucus secretion or clearance 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 anesthesia on the physical and transport properties of airway mucus in spontaneously 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 intravenous bolus followed by a maintenance infusion at 0.4 mg kg(-1).min(-1) or 4 mg/kg of methohexital followed by an infusion at 0.3 mg.kg(-1).min(-1). Premedication 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. Dogs were intubated but spontaneously breathing throughout the experiment. Tracheal secretions were collected after induction and again after 40 mins. Measurements and Main Results: The volume of secretions collected on the endotracheal tube during the 1.5-hr experiment and on a bronchoscopy brush over 10 mins during the experiment was measured. Tracheal epithelial potential difference was measured bronchoscopically by saturated agar bridges, and tracheal mucus transport velocity was determined by timing particle transport. The dynamic viscoelasticity of collected mucus was assessed by microrheometry, and secretion mucociliary transportability was measured in vitro. There were no differences in any physical or transport properties of airway secretions that could be attributed to the anesthetic agent. Secretion volume was significantly lower (p < .05) and epithelial potential difference was significantly higher (p = .03) with atropine premedication. Despite this, there were no differences in tracheal mucus transport velocity, viscoelasticity, or secretion mucociliary transportability with either anesthetic agent or with atropine. Conclusions: This study suggests that neither methohexital nor propofol significantly affects mucus secretion or clearance in healthy dogs.