ABSTRACT
BACKGROUND: Topical local anesthesia of the airway of anaesthetized children has many potential benefits. In our institution, lignocaine is topically instilled blindly into the back of the mouth with the expectation that it will come into contact with the larynx. The volume and method of application varies between clinicians. There is no published evidence to support the plausibility of this technique. AIM: To determine whether this technique of instillation results in the local anesthetic coming into contact with key laryngeal structures and whether this is influenced by volume or additional physical maneuvers. METHODS/MATERIALS: Sixty-three healthy anaesthetized children between 6 months and 16 years old had lignocaine stained with methylene blue poured into the back of their mouths. The volume and subsequent physical maneuver were determined by randomization. A blinded observer assessed staining of the vocal cords, epiglottis, vallecula and piriform fossae by direct laryngoscopy. Airway complications were recorded. RESULTS: Fifty-three of the 63 children had complete staining of all four areas. Four children had one area unstained, and all others had at least partial staining of all four structures. Nine children coughed following induction of anesthesia. Coughing was more likely in children with incomplete staining (P = 0.03), low volume lignocaine (P = 0.003) and following a head lift (P = 0.02). CONCLUSION: Oral administration of lignocaine without use of a laryngoscope frequently results in widespread coverage of key laryngeal structures and may reduce the risk of coughing.