Increased dosage of propofol in anesthesia induction cannot control the patient's responses to insertion of a laryngeal mask airway.

An increased dosage of propofol is frequently administered to reduce responses to insertion of the laryngeal mask airway (LMA). However, its clinical effect remains unknown. We investigated whether an increased dosage of propofol reduces responses to LMA insertion. Sixty adult patients were divided into 3 groups according to induction dosage of propofol (2.0 mg/kg, 2.5 mg/kg and 3.0 mg/kg). The patient's responses including body movement and the upper airway reflex were observed. The bispectral index (BIS) score as the index of the sedation level was monitored. There were no significant differences among the three groups in responses to LMA insertion, and no correlation was seen between the BIS score and the responses. These results suggest that propofol alone at clinical dosage levels does not completely control responses to LMA insertion. It is also suggested that the monitoring of BIS score is not effective in predicting responses to LMA insertion. Combination of propofol and analgesics such as fentanyl may be useful in reducing responses to LMA insertion.