Potentially toxic serum lidocaine concentrations following spray anesthesia for bronchoscopy.

Serum lidocaine concentrations were measured in a series of ten patients during and after topical lidocaine spray anesthesia used for diagnostic fiberoptic bronchoscopy. Mean total dose of lidocaine ranged from 480-720 mg. Peak serum lidocaine concentrations averaged 3.6 micrograms/ml (range: 1.9 to 7.4 micrograms/ml), and were attained shortly after the start of the procedure. Repeated topical administration of lidocaine spray therefore may lead to large cumulative doses and serum concentrations which are in the therapeutic or potentially toxic range.