Local anaesthesia to the airway reduces sedation requirements in patients undergoing artificial ventilation

Patients in the intensive care unit require large doses of sedative/analgesic drugs to tolerate the presence of a tracheal tube and other unpleasant stimuli. The ideal regimen for sedatives and analgesics has not yet been found. We have investigated the effects of topical local anaesthesia to the pharynx and airway on sedative/analgesic requirements in 30 ICU patients (25-75 yr old) with no obvious brain injury, undergoing mechanical ventilation. Oral tracheal tubes were changed to a modified tube which allowed instillation of local anaesthetic solutions onto the pharyngeal, laryngeal and tracheal mucosa. Lignocaine 1% (5 ml) or 5 ml of 0.9% saline were instilled hourly for 12 h each for a total of 24 h, in a double-blind, randomized crossover design. Baseline sedation was maintained with propofol or alfentanil infusions, or both, which were titrated to patient comfort and to maintain an optimum sedation score throughout. Twenty-five patients completed the study. Mean total propofol and alfentanil requirements were 766 (SD 524) mg and 17 (7.6) mg, respectively, during 12 h of lignocaine instillation, and 1321 (862) mg and 25 (11.4) mg, respectively, during 12 h of saline instillation. There was a significant reduction (P<0.05) in the requirements for both agents during the period of lignocaine instillation.