Structural differences of supraglottic airway devices could influence the different compressive forces in the oropharyngeal cavities, and require different depth of anesthesia. The addition of remifentanil during propofol anesthesia facilitates the insertion of laryngeal mask airway (LMA) with minimal adverse hemodynamic disturbances. This study was designed to determine the effect-site concentration of remifentanil in 50% of patients (EC50) and 95% of patients (EC95) for successful i- gel insertion, and compare those for LMA insertion during propofol target-controlled infusion (TCI).

Anesthesia was induced with propofol TCI at the effect-site concentration of 5 μg/ml, and the predetermined effect-site concentration of remifentanil was started simultaneously. The remifentanil concentration was determined using modified Dixon's up-and-down method (initial concentration: 3.0 ng/ml, step size: 0.5 ng/ml). Five minutes later, i- gel or LMA insertion was attempted. The response of the patients to the insertion of LMA was classified as either 'movement' or 'no movement'.

Inclusion Criteria:

• ASA I-II patients undergoing general anesthesia for short elective surgery (<2 hr)

Exclusion Criteria:

• G-E reflux
• obesity (BMI>30)
• anticipated difficult airway