Optimal remifentanil dose for laryngeal mask airway insertion when co-administered with a single standard dose of propofol.

Purpose: This dose-response study aimed to determine the optimal dose of remifentanil combined with propofol 2.5 mg.kg(-1) iv in order to achieve excellent conditions for laryngeal mask airway (LMA) insertion in 95% of adult female patients.

Methods: Sixty-eight adult premedicated female patients, American Society of Anesthesiologists (ASA) physical status I and II requiring anesthesia for ambulatory surgery, were randomly allocated to one of four remifentanil dose groups (0.25, 0.5, 1, or 2 microg.kg(-1)). Induction of anesthesia was achieved with one of the four blinded doses of remifentanil infused over 60 sec and simultaneously co-administered with propofol 2.5 mg.kg(-1) iv infused over 45 sec. Insertion of the LMA was attempted 150 sec after the beginning of the induction sequence. Insertion conditions were assessed using a six-category score according to resistance to mouth opening and insertion, swallowing, coughing and gagging, movement, and laryngospasm. A probit analysis was performed to calculate the effective dose for insertion of the LMA in 95% of patients (efficient dose [ED](95)). The changes in heart rate (HR) and mean arterial blood pressure (MAP) in response to LMA insertion were recorded and compared as secondary outcome variables.

Results: The ED(95) of remifentanil was 1.32 (95% confidence interval [CI] 0.99-2.46) microg.kg(-1). Changes in heart rate and mean arterial pressure were modest and similar over time across groups, with maximum decreases in heart rate and mean arterial pressure < 30% each during induction of anesthesia.

Conclusions: The required dose of remifentanil is 1.32 (95% CI 0.99-2.46) microg.kg(-1) to achieve excellent LMA insertion conditions in 95% of patients when co-administered with propofol 2.5 mg.kg(-1) in healthy premedicated female patients undergoing elective ambulatory surgery.