Local anesthetics and bronchial hyperreactivity

Patients with bronchial hyperreactivity are at increased risk for bronchospasm particularly during airway instrumentation such as with intubation, extubation, or bronchoscopy. Pretreatment with either lidocaine or salbutamol is suggested, since application of lidocaine intravenously or salbutamol as an aerosol has been shown to be similarly effective in increasing the (2,2 resp. 2,6fold) threshold for histamine evoked bronchoconstriction. Furthermore, combined salbutamol and lidocaine pretreatment has an additive effect and increases 4,8 fold the histamine-threshold. Thus, lidocaine treatment can be applied to patients with airway disease treated with beta (2)-mimetics also. Inhaled and injected lidocaine is equally effective in decreasing histamine threshold although at different plasma concentrations, i.e., lidocaine is effective at approx. 0.7 mug/ml after inhalation but at up to 2 mug/ml after injection. While inhaled lidocaine results in lower plasma concentrations it can evoke an initial bronchoconstriction. Furthermore, local anesthesia of pharynx and larynx associated with inhalation may not be tolerable in some patients. Intravenous lidocaine, in contrast, results in higher plasma concentrations and side-effects are seen more often. While several case reports have described beneficial effects of lidocaine in the treatment of bronchospasm no clinical studies have been performed. Overall, both inhaled and injected local anesthetics are effective in mitigating reflex mediated bronchoconstriction.