Effects of different target plasma concentrations of remifentanil on minimum alveolar concentration of sevoflurane for tracheal intubation in children

Objective To investigate the effects of different target plasma concentrations of remifentanil given by TCI on the minimum alveolar concentration(MAC)of sevoflurane for induction of tracheal intubation in children.Methods One hundred and twenty.six ASA Ⅰ or Ⅱ children aged 3-8 yr undergoing elective surgery under general anesthesia were randomly divided into 4 groups:control group(C,n=30),and target plasma concentration of remifentanil 1 ng/group(R1,n=30),2 ng/ml group(B2,n=30)and 3 ng/ml group(R3,n=36).Anesthesia WM induced with 5% sevoflurane.A catheter connected to gas analyzer was inserted into nasal cavity when the children lost eyelash reflex.Venous access was established,atropine 0.01 mg/kg was injected iv in group C,and remifentanil was given by TCI in group R1-3. After atropine Was injected in group C and the plasma and effect-site concentrations of remifentanil reached the balance,the up-and-down sequential experiment was performed.The initial end-tidal concentration of sevoflurane was and the ratio of the two 8uccessive concentrations was 1.2. After the end.tidal concentration of sevoflurane reached the predetermined value.it was maintained for 10 rain and tracheal intubation Was then performed.Satisfactory tracheal intubation condition was defined as the inlubation score = 6. MAC of sevoflurane in each group was calculated. Adverse effect were also recorded.Results The MAC of sevoflurane for tracheal intubation was 5%,3%,2%and 1% in group C and B1-3 respectively.No bradycardia and hypotension occurred in all the children.Tracheal intubation of 3 cases in group R2 and 8 cases in group R3 Was facilitated with iv injection of vecuronium because laryngoscope could not be inserted or the glottis was closed. Conclusion Remifentanil 1 ng/ml can reduce the MAC of sevoflurane for tracheal intubation and has less adverse effect in children. Key words: Piperidines; Drug delivery systems; Anesthetics, inhalation; Dose-response relationship, drug; Intubation, intracheal; Child