Effects of inhaled lidocaine on airway function in asthmatic subjects.

We measured the effect of inhaled lidocaine on pulmonary function in 8 asthmatic subjects. Plethysmographic specific airways conductance (SGaw) and the 1-sec forced expired volume (FEV1) were measured before and after the inhalation of 2cm3 of lidocaine (4%). Responses were also measured after patients were pretreated with either aerosolized isoproterenol, aerosolized atropine, or intramuscular atropine. In response to lidocaine alone, we observed a 23.4 +/- (SE) 4.8% fall in FEV1 and a 64.1 +/-(SE)3.8% fall in SGaw (p is less than 0.001). These effects were reversed with aerosolized atropine or isoproterenol. After pretreatment with aerosolized atropine or isoproterenol, the bronchoconstrictor effect of lidocaine were either prevented or markedly reduced. The protective effects of intramuscular atropine varied in different subjects, but in general, aerosolized bronchodilators afforded better protection against the bronchoconstrictor effect of lidocaine. Although lidocaine is theoretically capable of blocking neurogenic reflexes in the lung, our studies indicate that this topical anesthetic agent produces untoward reflex-mediated bronchoconstriction in patients with asthma and hyperirritable airways.