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

Abstract

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.