Early postoperative vomiting and volatile anaesthetics or nitrous oxide

Editor—The article by Apfel and colleagues¹ on volatileanaesthetics being the main cause of early postoperative vomitingis interesting. They separate out the effect of nitrous oxideand consider volatile anaesthetics to be the emetogenic factor.Have they considered the combined synergistic effect of nitrousoxide and volatile anaesthetics as the cause of postoperativenausea and vomiting? Furthermore, propofol may attenuate theeffect of the nitrous oxide if given before the inhalationalaspects. Buffington² has noted a 3.5-fold greater incidence of vomitingin patients given isoflurane