BACKGROUND: Propofol and alfentanil are frequently combined for general anesthesia. The purpose of this study was to characterize the appropriate effect-site concentration of alfentanil combined with an effect-site concentration of propofol of 4 µg /ml during endotracheal intubation.

METHODS: One hundred and thirty patients, aged 40-70 years and scheduled for abdominal surgery were randomly allocated to four groups according to the target effect-site concentrations of alfentanil: 0 ng/ml in the placebo group, 50 ng/ml in the P₅₀ group, 75 ng/ml in the P₇₅ group, and 100 ng/ml in the P₁₀₀ group. All patients received a computer controlled infusion of propofol with an effect-site concentration of 4 µg/ml. After equilibration between plasma and effect-site was achieved, and the trachea of the patient was intubated. The assessments of hemodynamic changes were usually confined to the measurement of changes in systolic/diastolic blood pressure (SBP/DBP), mean arterial pressure (MAP), and heart rate (HR). Also, we checked the dose requirements of ephedrine and atropine used to correct hypotension and bradycardia.

RESULTS: The use of alfentanil (especially 50 or 75 ng/ml) was effective at blunting the SBP increase during the few minutes after intubation. However, the dose requirements of ephedrine and atropine in the P₁₀₀ group were significantly higher than those in other groups.

CONCLUSIONS: The appropriate effect-site concentration of alfentanil combined with an effect-site concentration of propofol of 4 µg/ml during endotracheal intubation lies between 50 and 75 ng/ml.