The effect of propofol infusion on minimum alveolar concentration of sevoflurane for smooth tracheal intubation.

Purpose: This study was conducted to determine the effect of propofol infusion on the minimum alveolar concentration necessary for smooth tracheal intubation (MACEI) of sevoflurane.

Methods: Sixty-nine patients, American Society of Anesthesiologists (ASA) status I, aged 30-49 years, were randomly assigned to one of three groups according to the agents used for tracheal intubation (n = 23 for each group): the SP group, in whom the intubation was attempted under sevoflurane plus propofol infusion; the S group, tracheal intubation under sevoflurane alone; and the P group, tracheal intubation under propofol infusion alone. Anesthesia was induced with propofol 2.5 mg.kg(-1) i.v. bolus. Prior to the tracheal intubation attempt, propofol infusion, 10 mg.kg(-1).h(-1), was given for 15 min in the SP and P groups, and sevoflurane equilibration was established in the SP and S groups. All tracheal intubation attempts were made 15 min after anesthetic induction. The end-tidal sevoflurane concentration at which tracheal intubation was attempted was predetermined by the up-and-down method (with 0.5% as a step size). MACEI was determined using a logistic regression test.

Results: The MACEI of sevoflurane was 1.73% in the SP group, and 2.99% in the S group. Laryngoscopy was not possible in the P group patients.

Conclusion: Propofol infusion reduced sevoflurane MACEI. This finding suggests that propofol would be an excellent adjuvant to use with sevoflurane for tracheal intubation.