When combined with intrathecal sufentanil 2.5 µg and intrathecal morphine 100 µg, the ED₉₅ of intrathecal levobupivacaine is 12.9 mg for Caesarean delivery. If doses of levobupivacaine less than the ED₉₅, particularly near the ED₅₀, are used, these doses should be administered under a CSE technique.

Purpose This dose-response study aimed to determine the optimal dose of remifentanil combined with propofol 2.5 mgÁkg -1 iv in order to achieve excellent conditions for laryngeal mask airway (LMA TM ) 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 lgÁkg -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 mgÁkg -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) lgÁkg -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) lgÁkg -1 to achieve excellent LMA insertion conditions in 95% of patients when co-administered with propofol 2.5 mgÁkg -1 in healthy premedicated female patients undergoing elective ambulatory surgery. RésuméObjectif L'objectif de cette e´tude de dose-re´ponse e´tait de de´terminer la dose optimale de re´mifentanil lors de l'administration conjointe de propofol 2,5 mgÁkg -1 iv afin d'obtenir des conditions excellentes pour l'insertion d'un masque larynge´(LMAÒ) chez 95 % de patientes adultes. Méthode Soixante-huit patientes adultes ASA I et II pre´me´dique´es et ne´cessitant une anesthe´sie pour une chirurgie ambulatoire ont e´te´randomise´es en quatre groupes selon la dose de re´mifentanil (0,25, 0,5, 1 ou 2 lgÁkg -1 ). L'induction de l'anesthe´sie a e´te´re´alise´e avec l'une des quatre doses de re´mifentanil en aveugle perfuse´e sur 60 secondes, administre´e simultane´ment a`du propofol 2,5 mgÁkg -1 iv perfuse´sur 45 secondes. L'insertion du Support was provided solely by institutional sources.

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