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). 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.