Abstract
The aim of this randomised, controlled trial was to determine the optimum dose of fentanyl in combination with propofol 2.5 mg.kg-1 when inserting the Classic™ Laryngeal Mask Airway.
Seventy-five ASA I or II patients were randomly assigned to five groups of fentanyl dosage: 0 μg.kg-1 (placebo), 0.5 μg.kg-1, 1.0 μg.kg-1, 1.5 μg.kg-1 and 2.0 μg.kg-1 Anaesthesia was induced by first injecting the study drug over 10 seconds. Three minutes after the study drug was injected, propofol (2.5 mg.kg-1) was injected over 10 seconds. The Classic™ Laryngeal Mask Airway was inserted four minutes and 30 seconds after injection of the study drug. Insertion conditions were evaluated using a four-category score.
Thirty-nine males and 36 females aged 19 to 59 years were studied. The incidence of prolonged apnoea increased as fentanyl dose increased. We found that there was a high rate of successful first attempt at insertion with 1 μg.kg-1 and 1.5 μg.kg-1, 93% and 87% respectively, compared to 87% in the 2.0 μg.kg-1 group. The 1.0 μg.kg-1 group also achieved an 80% optimal insertion conditions score of 4, compared to 73% in the 1.5 μg.kg-1 group and 80% in the 2 μg.kg-1 group. Therefore we recommend 1.0 pg.kg-1 as the optimal dose of fentanyl when used in addition to propofol 2.5 mg/kg for the insertion of the Classic™ Laryngeal Mask Airway.