Fentanyl decreases propofol requirement for laryngeal mask airway insertion

Background: Since fentanyl is a potent depressant of the upper airway reflex, preadministration of fentanyl may facilitate insertion of the laryngeal mask airway (LMA(TM)) using propofol. Accordingly, we tested the hypothesis that fentanyl pretreatment would reduce the dose of propofol required for the LMA insertion. Methods: Forty-one healthy patients without sedative premedication were randomly assigned to either fentanyl group, receiving fentanyl 2 mug kg(-1) intravenously, or control group, receiving equal volumes of normal saline. Then, 3 ml of 2% lidocaine was given intravenously to alleviate pain associated with propofol administration. Thirty s after the fentanyl or saline injection, a predetermined dose of 1% propofol was given at a rate of 100 mg min(-1). Insertion of the LMA was attempted 90 s after the completion of the propofol injection. The dose of propofol given to a particular patient was determined by the response of the preceding patient in that group to a higher or lower dose, using the up-and-down method. The first patient in each group received 2.5 mg kg(-1) of propofol, while the step-size was 0.25 mg kg(-1). Patients responses were assessed by a blinded observer. Results: ED50 and ED95 of propofol requirements were significantly less in the fentanyl group (0.82, 1.17 mg kg(-1), respectively) than those in the control group (2.39, 2.62 mg kg(-1), P < 0.001). Conclusion: Our results indicate that preadministration of fentanyl 2 μg kg(-1) decreases the propofol requirement for the LMA insertion.