To determine propofol concentration of plasma 50% (Cp₅₀, concentration at which there is a 50% chance that patients show no movement in response) for the Classic-, Fastrach-, and ProSeal-type laryngeal mask airway (LMA) insertion using target-controlled infusion (TCI) technique.

Prospective, randomized, comparative study.

University-affiliated hospital.

Sixty American Society of Anesthesiologists physical status I and II women scheduled for minor gynecologic operations.

Propofol TCI (Diprifusor pharmacokinetic model) was started at target concentration using an anesthesia pump. After reaching target effect-site concentration of propofol, 1 of the 3 types of LMA was inserted. We recorded patient responses to LMA insertion as “movement” or “no movement.” Test propofol concentrations started from a dosage of 4 μg/mL. Concentrations were then predetermined by a modified Dixon's up-and-down method with 0.4 μg/mL step size.

Patient response to LMA insertion was classified as either of “no movement” or “movement.” The midpoint was defined as the average concentration value of crossover (movement/no movement) response. The Cp₅₀ value was defined as the average of the crossover midpoints in each group, and it was estimated from calculating the midpoints.

Cp₅₀ of the Classic, Fastrach, and ProSeal LMA insertion were 3.2 ± 0.34, 4.0 ± 0.22, and 4.9 ± 0.20 μg/mL (mean ± SD), respectively.

Required propofol TCI concentrations for LMA insertion were significantly highest for the ProSeal, second highest for the Fastrach, and lowest for the Classic LMA.