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SummaryPlcr.vnii lignocaine levels were measured at 5 . I0 Anaesthesia for routine endoscopy of the upper airway in children at Great Ormond Strcct Hospital involves the usc of a spontaneous ventilation technique with local application of lignocaine to inhibit the laryngeal reflexes. Previous studiesl-~" have shown that high plasma levels of local anxsthelics may be achieved from topical absorplion. The ralc of absorption Is thought to be related to the moistness of the mucosa of the upper airway and hence the efficacy o f the premedication as a n antisialogogue.Thc purpose of this study was to correlate the plasma lcwls of lignocaine, following local application to the upper airway. t o the moistness o f the mucosa. MethodsThirty children were studied, with ages which ranged froin 8 months to 10 years, and weights from 7-24 kg. They had all heen referred to hospital for assessment of congcnital and acquired upper airway abnormalities and were otherwise healthy. Informed consent for the study was obtained froin thc parcnts.4 1 1 patients were premedicated with intramuscular atmpine 0.02 mg/kg one hour pre-operatively. Anaesthesia wax induced with either cyclopropane in oxygen or halothane in nitrous oxide and oxygen. A 23-gauge winged needle was put into a vein in the anteeubital fossa and suxamethonium 1 mgikg was administered once anaesthesia was achieved.Laryngoscopy was performcd by a consultant anaesthetist, after manual inflation of the lungs via a facemask with 100% oxygen, and a subjective assesment made of the degree of moistness of the upper airway mucosa using a previously agreed 1-5 scale. On this scale, 1 was taken to represent a very dry mucosa; 2 a dry mucosa; 3 a moist mucosa; 4 a wet mucosa; and 5 a very wet mucosa.The anaesthetist then sprayed the upper airway with lignocaine via a metered spray; each spray delivered 10 mg of lignocainc basc. A dose of 4 mg/kg was directed in equal proportions to the supraglottic. glottic and subglottic regions. The accuracy of this aerosol was verified by dissolving one spray into a known amount of normal saline and analybing this solution in the same way as the blood samples.A nasotracheal tube was passed and connected to an Ayre's T-piece. Anaesthesia was maintained with the patient breathing spontaneously halothane, nitrous oxide and oxygen. The distal end of the tube was withdrawn into the pharynx for the surgical part of the procedure.Serial venous blood samples were taken from the indwelling needle at 5. 10 and 15 minutes from application of the lignocaine. These samples were preserved in lithium heparin prior to analysis by high pressure liquid chromatography.s Blood was also taken for estimation of urea and electrolytes and liver function tests. The blood pressure and electrocardiograph were recorded throughout the procedure.

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