The effect of adding nitrous oxide on MAC of sevoflurane combined with two target-controlled concentrations of remifentanil in women

Eur J Anaesthesiol. 2005 Jun;22(6):431-7. doi: 10.1017/s0265021505000736.


Background and objective: The aim of this prospective, randomized, double-blind study was to determine the effects of adding nitrous oxide on sevoflurane requirement for blunting sympathetic responses after surgical incision combined with two different target-controlled concentrations of remifentanil (1 and 3 ng mL(-1)) in female.

Methods: 102 female patients, aged 20-50 yr, ASA I, undergoing general anaesthesia for elective abdominal surgery were enrolled and randomly allocated to receive sevoflurane anaesthesia alone (Group A, n=53), or with the addition of 60% nitrous oxide (Group N, n=49). Patients of both groups were further assigned to receive a target-controlled remifentanil infusion with an effect-site concentration of either 1 ng mL(-1) (Group N1, n=27; Group A1, n=30), or 3 ng mL(-1) (Group N3, n=22; Group A3, n=23). Sympathetic responses to surgical incision were determined after a 20-min period of stable end-tidal sevoflurane and target-controlled remifentanil concentrations. Predetermined end-tidal sevoflurane concentrations and minimum alveolar concentration (MAC) for each group were determined using an up-and-down sequential allocation technique.

Results: The MAC of sevoflurane was 3.96% (95% confidence interval, CI95: 3.69-4.23%) in Group A1 and 1.2% (CI95: 0.9-1.3%) in Group N1 (P < 0.01), while in Groups A3 and N3 the MAC of sevoflurane was 0.36% (CI95: 0.24-0.47%) and 0.18% (CI95: 0.1-0.3%), respectively (P < 0.05).

Conclusion: Adding 60% nitrous oxide reduces the MAC of sevoflurane by 70% when using a remifentanil concentration of 1 ng mL(-1) and 50% when using a remifentanil concentration of 3 ng mL(-1).

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anesthesia, General*
  • Anesthetics, Inhalation*
  • Anesthetics, Intravenous* / administration & dosage
  • Anesthetics, Intravenous* / pharmacokinetics
  • Blood Pressure / drug effects
  • Double-Blind Method
  • Drug Delivery Systems
  • Female
  • Heart Rate / drug effects
  • Humans
  • Logistic Models
  • Methyl Ethers*
  • Nitrous Oxide*
  • Piperidines* / administration & dosage
  • Piperidines* / pharmacokinetics
  • Prospective Studies
  • Pulmonary Alveoli / metabolism*
  • Remifentanil
  • Sevoflurane


  • Anesthetics, Inhalation
  • Anesthetics, Intravenous
  • Methyl Ethers
  • Piperidines
  • Sevoflurane
  • Nitrous Oxide
  • Remifentanil