Sevoflurane requirements for tracheal intubation with and without fentanyl

We studied 80 healthy ASA I patients (aged 20-52 yr) to determine if fentan yl affects sevoflurane requirements for achieving 50% probability of no mov ement in response to laryngoscopy and tracheal intubation (MAC-TI). Patient s were allocated randomly to one of four fentanyl dose groups (0, 1, 2 and 4 mu g kg(-1)). Patients in each group received sevoflurane at a pre-select ed end-tidal concentration according to an 'up-down' technique. After stead y state sevoflurane concentration had been maintained for at least 10 min, fentanyl was administered i.v. Tracheal intubation was performed 4 min afte r administration of fentanyl, and patients were assessed as moving or not m oving. Heart rate (HR) and mean arterial pressure (MAP) were recorded befor e induction of anaesthesia, just before administration of fentanyl, just be fore laryngoscopy for intubation, and after intubation. The MAC-TI of sevof lurane was 3.55% (95% confidence intervals 3.32-3.78%), and this was reduce d markedly to 2.07%, 1.45% and 1.37% by addition of fentanyl 1, 2 and 4 mu g kg(-1), with no significant difference in the reduction between 2 and 4 m u g kg(-1), showing a ceiling effect. Fentanyl attenuated haemodynamic resp onses (HR and MAP) to tracheal intubation in a dose-dependent manner, even with decreasing concomitant sevoflurane concentration. Fentanyl 4 mu g kg(- 1) suppressed the changes in HR and MAP more effectively than fentanyl I or 2 mu g kg(-1) at sevoflurane concentrations close to MAC-TI.