This study was performed to compare responses to the insertion of an intubating laryngeal mask airway (ILMA) and to the intubation of an endotracheal tube according to insertion time when used with sevoflurane and without muscle relaxant.

We used 50% N₂O-O₂-8% sevoflurane and a 10% topical lidocaine spray. Forty-eight patients were randomized into four groups according to insertion time (each, n = 12). The ILMA was inserted at 3, 4, 5, and 6 minutes after sevoflurane induction and intubation was performed at 1 minute after ILMA insertion. Responses to intubation, such as vital signs, jaw relaxation, coughing, biting, movements, and laryngospasm were compared according to ILMA insertion time.

At 3 minutes, overall responses to insertion and intubation were worse than at 4, 5, and 6 minutes (P < 0.05). At 4, 5, and 6 minutes, responses to the insertion of the ILMA and the intubation of endotracheal tube were satisfactory.

Insertion of ILMA at 4 minutes after sevoflurane induction proved satisfactory, and this could be applied in clinical practice.