Systemic absorption of lignocaine ointment from tracheal tubes

Arterial plasma concentrations of lignocaine were studied in fifteen adult patients following insertion of a tracheal tube whose cuff area was smeared with 5% lignocaine ointment. Twelve patients had 2 ml of ointment (114 mg) and samples were taken every 5 minutes until 30 minutes and in eight of the 12 patients at 40, 50 and 60 minutes after insertion and inflation of the tracheal tube and cuff. Three patients had 1 ml of ointment on the tube and were studied over 60 minutes. Plasma concentrations were determined using gas liquid chromatography. In the 2 ml lignocaine group mean plasma lignocaine levels were 1.9 (SD 0.9) micrograms/ml at 10 minutes, 2.3 (SD 0.8) micrograms/ml at 20 minutes, 2.3 (SD 0.8) micrograms/ml at 30 minutes and 1.7 (SD 1.0) micrograms/ml at 60 minutes. After 1 ml of lignocaine, levels were 1.2 (SD 0.1) micrograms/ml at 10 minutes, 1.1 (SD 0.7) micrograms/ml at 20 minutes, 0.8 (SD 0.3) micrograms/ml at 30 minutes and 0.75 (SD 0.1) micrograms/ml at 60 minutes.