Plasma lignocaine concentrations following endotracheal spraying with an aerosol

Plasma concentrations of lignocaine were measured in three groups of anaesthetized patients following spraying of the trachea and larynx with a lignocaine 10% aerosol spray. Greater venous plasma concentrations occurred in patients who were paralysed with suxamethonium. A mean plasma concentration of 0.1 mug/ml of lignocaine resulted from each 10 mg of lignocaine used in spontaneously breathing patients, and 0.15 mug/ml in paralysed patients. In individual patients a concentration 50% in excess of the mean value may occur. The use of lignocaine 100 mg as a 10% aerosol spray can be considered safe.