Topical analgesia of the upper airway with lignocaine. Absorption and its relationship to toxic and anti-arrhythmic levels.

After routine topical application of lignocaine to the upper airway before passage of an endotracheal tube during general anaesthesia, plasma lignocaine levels were assayed in 20 artificially ventilated and 21 spontaneously ventilating patients. Systemic absorption was found to be rapid but very variable. Mean peak level were attained 15 minutes before spraying and were well below the convulsive threshold for anaesthetized patients, while reputedly anti-arrhythmic levels were achieved by 5 minutes and maintained until 40 minutes. Levels in the ventilated group were significantly higher 20 minutes after administration.