Remifentanil halves the EC50 of propofol for successful insertion of the laryngeal mask airway and laryngeal tube in pediatric patients

BACKGROUND: Propofol and remifentanil are the drugs of choice for insertion of the supraglottic airway without muscle relaxants for short duration surgery. In this study, we compared propofol concentrations required for insertion of laryngeal mask way (LMA) or laryngeal tube (LT) with and without remifentanil. METHODS: We included children scheduled for surgeries lasting < 2 h, and assigned, them to four groups in a randomized, double-blind manner: LMA with propofol + saline (LMA-P), LT with propofol + saline (LT-P), LMA with propofol +7.5 ng/mL remifentanil (LMA-PR), LT with propofol +7.5 ng/mL remifentanil (LT-PR). Anesthesia was conducted by target-controlled infusion in determined target effect site concentration of propofol and remifentanil with the STELPUMP program. The EC50 of propofol for airway device placement was determined using Dixon's up-and-down method. The concentration of propofol for consecutive patients in each group was determined by the response of the previous patient, using increments or decrements of 0.2 mu g/mL. RESULTS: In patients receiving remifentanil, propofol EC50 for insertion of a LMA was 2.57 +/- 0.22 mu g/mL and that of LT was 2.59 +/- 0.20 mu g/mL (n.s.). In patients receiving saline, the corresponding values were 5.45 +/- 0.21 mu g/mL and 5.58 +/- 0.23 mu g/mL (n.s.). Conditions were excellent in 64% (9 of 14) and 79% (11 of 14) of patients receiving remifentanil, but in patients receiving saline, the values were 18% (2 of 11) for the LMA and 40.0% (4 of 10) for the LT. CONCLUSIONS: Remifentanil 7.5 ng/mL reduced the propofol concentration required for airway insertion by half, and improved conditions for insertion. Propofol concentrations for insertion of the LMA and LT were similar.