Topical anaesthesia of the larynx: cocaine or lignocaine?

A double-blind, randomized study compared the cardiovascular responses and extubation conditions using lignocaine or cocaine for topical anaesthesia of the larynx. Absorption of both agents from the trachea was quantified by serial venous plasma concentrations. Serial blood pressure, ECG, O2 saturation and end-tidal carbon dioxide measurements were obtained. Conditions at extubation were assessed on duration of coughing, graded on a scale of 1-4 (1 = no coughing, 2 = single cough, 3 = coughing lasting less than 30 s, 4 = coughing lasting 30 s or more). No difference was found in cardiovascular measurements between the two groups. The patterns of absorption of cocaine and lignocaine from the laryngeal mucosa were very similar, with peak absorption occurring at 10-15 min after laryngeal spraying. Although cocaine reduced the incidence of post-operative coughing when compared with lignocaine, this did not reach statistical significance.