Optimal End-Tidal Sevoflurane Concentration for Rapid and Safe Insertion of Laryngeal Mask Airway and Endotracheal Tube in Children

Background: Laryngeal mask airway and sevoflurane are increasingly used in anesthesia for children undergoing minor and moderate surgical procedures. We aimed to determine end tidal sevoflurane concentration that allows insertion of either LMA or ETT without adverse airway events within clinically acceptable time (5 minutes).Methods: One hundred and sixty children (3-9 years) were randomly allocated into either LMA (70 children) or ETT group (90 children) according to method of airway securing. Patients in each group were further subdivided into subgroups (n= 10 each) according to the predetermined sevof¬lurane concentration that would be applied for 5 minutes, into LMA (7 subgroups) 1%, 1.5%, 2%, 2.5%, 3%, 3.5% and 4% and ETT (9 subgroups) 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% and 6%. Patient response to either LMA or ETT insertion was recorded as yes or no. Curves were constructed by plotting the value of end tidal sevoflurane concentration against percentage of non responders in each subgroup. Mean arterial pressure, heart rate, end tidal carbon dioxide and oxygen saturation were also recorded.Results: End tidal sevoflurane concentrations that achieved LMA insertion without response in 50% and 95% of children were 2.2 (0.2)% and 3.8 (0.24)% respectively meanwhile, those for endotracheal intubation were 3.8 (0.37)% and 5.9 (0.39)% respectively.Conclusion: Rapid (5 minutes) and safe insertion of LMA and ETT in 95% of children could be achieved at end tidal sevoflurane concentrations of 3.8 (0.24)% and 5.9 (0.39)% respectively.