Dixon up-and-down method was used to determine 50% effective concentration of remifentanil by target controlled infusion for inhibiting the haemodynamic responses during DLT intubation with Airtraq videolaryngoscope or Macintosh laryngoscope.
The 50% effective concentration of remifentanil by target controlled infusion was not determined for inhibiting the haemodynamic response during double-lumen tube (DLT) intubation. Previous study showed that Airtraq videolaryngoscope provided more stable haemodynamics than Macintosh for double-lumen tube intubation. In this study, the investigators will compare the 50% effective concentration of remifentanil between Airtraq videolaryngoscope and Macintosh laryngoscope for inhibiting haemodynamic responses during DLT intubation.