Lidocaine, Ropivacaine, and Dyclonine Compared for Ability to Attenuate Histamine-induced Bronchospasm.Groeben et al. (page 423)

To assess the relation between attenuation of histamine-evoked bronchoconstriction and topical anesthesia, Groeben et al.  compared the effects of aerosolized lidocaine, ropivacaine, and dyclonine in 15 volunteers with bronchial hyperreactivity. At initial screening visits, lung function measurements were performed, including baseline vital capacity, forced expiratory volume in 1 s, and maximal inspiratory flow at 50% of the vital capacity. Volunteers also underwent inhalational challenge with histamine to confirm bronchial hyperreactivity.

On each of 4 study days, baseline lung function was assessed again. In random order, volunteers inhaled lidocaine (4%), ropivacaine (1%), dyclonine (1%), or saline (0.05 ml/kg). Lung function was assessed immediately after inhalation, and then histamine challenges were repeated. To effect the challenge, the team used starting concentrations of histamine diphosphate of 0.075 mg/ml and then trebled that on each subsequent challenge up to a dose of 18 mg/ml. Venous blood also was drawn at 5-min intervals for analysis of plasma concentrations of the anesthetics.

At the screening evaluations, the inhaled histamine concentration necessary for a 20% decrease of forced expiratory volume in 1 s was 7.0 ± 5.0 mg/ml. Lidocaine and ropivacaine significantly increased it to 16.1 ± 12.9 and 16.5 ± 13.6 mg/ml, respectively. Despite producing profound topical anesthesia, dyclonine did not attenuate histamine-induced bronchospasm. In addition, dyclonine also might be considered contraindicated even as a topical anesthetic in patients with bronchial hyperreactivity because it also caused significant airway irritation. Although the mechanisms for attenuating histamine-induced bronchospasm are unclear, effects on airway smooth muscle or neural structures may explain partially the effects of lidocaine and ropivacaine seen in this study.