Myles PS, Leslie K, Chan MT et al. Avoidance of nitrous oxide for patients undergoing major surgery: a randomized controlled trial. Anesthesiology 2007; 107: 221.
RHH Journal Club. July 7th, 2012. Dr Juliette Fraser
Does avoidance of nitrous oxide in anaesthesia for major surgery lead to earlier discharge from hospital?
Type of Study:
Randomised controlled trial.
Multi centre trial
Not double blinded and only blinded to the surgical teams
Previous trial done which allowed for estimation of numbers that were needed for the trial.
Approximately 1000 patients in each arm of the trial.
Very confluent groups of patients within each arm of the trial.
Suggested anaesthetic within each group, so nitrous oxide group was to have 70% nitrous/30% oxygen mix and the non nitrous group was to have 80% oxygen/20% air mix.
However, oxygen concentrations could be increased/decreased if necessary or if the anaesthetist preferred
Trial questions: Does avoidance of nitrous oxide in anaesthesia for major surgery lead to earlier discharge from hospital?
And, if not using nitrous oxide then this allows for higher concentrations of oxygen and so does this reduce post operative complications
Results showed that the mean oxygen concentration in the non nitrous group was around 70% and in the nitrous group was around 30% so as planned.
Unfortunately there was no difference in length of hospital stay between the 2 groups, but there was a lower incidence of postoperative complications within the non-nitrous group which was statistically significant.
This could not be put down entirely to higher oxygen concentrations though.
The majority of the postoperative complications were related to atelectesis and pulmonary complications.
There was significantly less severe nausea and vomiting in the non-nitrous group
There was further subgroup analysis done which showed dietary supplements in the nitrous group did not confer any benefit.
Further preliminary analysis seemed to show less myocardial events in the non nitrous group but since the trial was not designed for this it was not adequately powered in this direction.
A further trial is planned to look specifically at this question.