Sevoflurane requirements for tracheal intubation with and without fentanyl

We studied 80 healthy ASA 1 patients (aged 20-52 yr) to determine iffentanyl affects sevoflurane requirements for achieving 50% probability ofno movement in response to laryngoscopy and tracheal intubation (MAC- TI).Patients were allocated randomly to one of four fentanyl dose groups (0, 1,2 and 4 micrograms kg-1). Patients in each group received sevoflurane at apre-selected end-tidal concentration according to an 'up-down' technique.After steady state sevoflurane concentration had been maintained for atleast 10 min, fentanyl was administered i.v. Tracheal intubation wasperformed 4 min after administration of fentanyl, and patients wereassessed as moving or not moving. Heart rate (HR) and mean arterialpressure (MAP) were recorded before induction of anaesthesia, just beforeadministration of fentanyl, just before laryngoscopy for intubation, andafter intubation. The MAC-TI of sevoflurane was 3.55% (95% confidenceintervals 3.32-3.78%), and this was reduced markedly to 2.07%, 1.45% and1.37% by addition of fentanyl 1, 2 and 4 micrograms kg-1, with nosignificant difference in the reduction between 2 and 4 micrograms kg-1,showing a ceiling effect. Fentanyl attenuated haemodynamic responses (HRand MAP) to tracheal intubation in a dose-dependent manner, even withdecreasing concomitant sevoflurane concentration. Fentanyl 4 microgramskg-1 suppressed the changes in HR and MAP more effectively than fentanyl 1or 2 micrograms kg-1 at sevoflurane concentrations close to MAC-TI.