The sevoflurane-sparing effect of nitrous oxide: a clinical study

Background: We studied the sevoflurane-sparing effect of nitrous oxide in a prospective randomised study. Methods: Forty-two ASA I-II patients scheduled for elective knee arthroscop y under general anaesthesia were randomly assigned to a fresh gas flow cons isting of oxygen in air or oxygen in nitrous oxide 1:2. All patients receiv ed a standardised anaesthesia consisting of induction with fentanyl and pro pofol and maintenance with sevoflurane adjusted according to clinical signs . The sevoflurane consumption was studied by means of weighing the vaporise r before and after every anaesthesia. Results: The mean sevoflurane consumption was reduced from 0.62 to 0.25 g/m in, a 60% reduction, by the use of oxygen in nitrous oxide 1:2 in the fresh gas flow. The emergence was faster for the patients receiving nitrous oxid e. No major differences were observed during recovery. Conclusion: Nitrous oxide was found to be cost-effective for use during sho rt ambulatory knee arthroscopy.