Propofol requirement for insertion of cuffed oropharyngeal airway versus laryngeal mask airway with and without fentanyl: a dose-finding study.

BACKGROUND

The cuffed oropharyngeal airway (COPA) is a modified Guedel-type oral airway with a cuff at its distal end. The objectives of this prospective, randomized study were to compare the COPA and the laryngeal mask airway (LMA) in terms of propofol requirement with and without fentanyl pretreatment for smooth insertions.

METHODS

Seventy-five patients undergoing general anaesthesia were randomly assigned to either a COPA (n=38) or LMA (n=37) group for airway management, and each group was further randomized to a saline-propofol or fentanyl-propofol group for anaesthesia induction. The saline-propofol group received i.v. saline and the fentanyl-propofol group received i.v. fentanyl 1 micro g kg(-1) followed 30 s later by i.v. propofol. Insertion of the device was attempted 90 s after propofol administration without the use of neuromuscular blocking agents or other adjuvants, and the responses of 'movement' or 'no movement' were judged by three observers blinded to the drug dose. Each dose of propofol at which insertion was attempted was predetermined by modification of Dixon's up-and-down method with 0.5 mg kg(-1) as the step size, and 2 mg kg(-1) as an initial dose.

RESULTS

Without fentanyl pretreatment, propofol requirement [mean (SD), 95% CI] for COPA placement [2.17 (0.38), 1.77-2.56 mg kg(-1)] was significantly less than for LMA insertion [3.42 (0.26), 3.15-3.69 mg kg(-1), P<0.001]. In contrast, propofol requirements after fentanyl were comparable between the COPA and LMA groups [1.50 (0.42), 1.06-1.94 and 1.42 (0.26), 1.15-1.69 mg kg(-1), respectively], but were less than for the placebo group with both devices (P<0.05). Haemodynamic changes and duration of apnoea were similar with both devices irrespective of fentanyl pretreatment.

CONCLUSIONS

Insertion of the COPA can be accomplished with a smaller bolus dose of propofol compared with the LMA, but propofol requirements are similar with both devices after a small dose of fentanyl.