A Comparison of Different Concentrations of Lignocaine Hydrochloride used for Topical Anaesthesia of the Larynx of the Cat

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Abstract
Electromyographic (EMG) recordings were made from the intrinsic laryngeal muscles (cricothyroid, thyroarytenoid) and the diaphragm of the cat to compare the effect of the same dose of different concentrations of lignocaine hydrocholoride applied topically to the laryngeal mucosa. All concentrations of lignocaine hydrochloride tested, two, five and ten per cent, produced desensitisation of the larynx, as demonstrated by a loss of response of the crocothyroid and thyroarytenoid to mechanical stimulation of the mucosa. Desensitisation was produced in a mean of 1.80 minutes in the thirty experiments performed. Return of baseline response took significantly longer when 5 or 10% lignocaine was used compared with that when 2% was used (p