Distorted perception of smell by volatile agents facilitated inhalational induction of anesthesia

Summary Background:  Unpleasant smell of halogenated volatile agents is one of the frustrating factors for inhalational induction. We developed a new modification that might enable children to enjoy the smell itself while incrementally elevating sevoflurane concentration. Troposmia is usually a pathological quality change of smell perception and an olfactory stimulus is distortedly perceived in this state, which we applied to inhalational induction. Methods:  At the preoperative visit an anesthetist told the children that the smell of a facemask could be magically changed from strawberry into anything and promised to change the smell as they requested. In the operating room, a strawberry scented facemask was fitted to the face and the anesthetist announced to them that the magical change of the smell would begin when sevoflurane was added. Whether children perceived the change of the smell as they requested was investigated in the troposmia group, and resistance to fit a facemask was compared between the troposmia group and a control group. Results:  Significantly fewer children resisted the facemask in the troposmia group (1 of 32 Vs 9 of 32; P = 0.0059). In the troposmia group 18, 22 and 25 of the 32 children said the smell of the facemask changed as they requested before they fell asleep, at the postoperative visit or both, respectively. Conclusions:  Troposmia can be intentionally induced to perceive the smell of sevoflurane on request. Troposmia might contribute to promote children's participation in anesthesia induction and facilitate inhalational induction.