DETERMINATION OF END-TIDAL SEVOFLURANE CONCENTRATION FOR TRACHEAL INTUBATION IN CHILDREN WITH THE RAPID METHOD

Purpose: Using the conventional method of determining the end-tidal co ncentration of inhalational anaesthetics for tracheal intubation, a co nstant end-tidal anaesthetic concentration is maintained for at least 15 min. As sevoflurane has a low tissue/gas partition coefficient, it seems possible in paediatric patients to determine end-tidal concentra tions for tracheal intubation more rapidly by using a high inspired co ncentration. We determined ED(50) and ED(95) of sevoflurane for trache al intubation, the end-tidal concentrations that prevented 50% and 95% of patients from coughing and gross purposeful muscular movements aft er intubation. Methods: Twenty-nine, ASA I, unpremedicated patients, a ged two to eight years, were enrolled. Anaesthesia was induced using a mask and 5% sevoflurane, inspired, in oxygen. When end-tidal sevoflur ane concentration attained a predetermined value laryngoscopy and trac heal intubation Mare performed using an uncuffed tracheal tube without neuromuscular relaxants or adjuvants. Each concentration at which lar yngoscopy and tracheal intubation were attempted was randomly predeter mined (with 0.5% as a step size). When tracheal intubation was accompl ished without gross purposeful muscular movements, it was considered a smooth tracheal intubation. Results: The ED(50) end-tidal sevoflurane concentration for tracheal intubation was 3.10% (95% confidence limit s: 2.43% and 3.78%), and the ED(95) was 4.68% (95% confidence limits: 3.91% and 12.74%). The times to end-tidal sevoflurane concentrations o f 3.0% and 4.5% were 149 +/- 15 sec (mean +/- SD) and 213 +/- 23 sec. Conclusion: In paediatric patients, this method enabled determination of ED(50) and ED(95) end-tidal sevoflurane concentrations for tracheal intubation without obtaining a long stabilization period.