Anesthesia affects olfaction and chemosensory event-related potentials

Objective: Olfactory and trigeminal systems interact and contribute to the perception of odorants. This study was aimed at investigating the effect of local anesthesia on olfaction. Methods: One percent of tetracaine on a cotton swab was applied intranasally at three different locations in 20 volunteers and 4% of lidocaine was applied to the olfactory cleft in a head-down position. Before and after anesthesia, self-assessment, psychometric testing and olfactory event-related potentials [OERPs, using H2S and phenyl ethyl alcohol (PEA)], and chemosomatosensory event-related potentials (CSSERPs, Using CO2) were examined. Results: Anesthesia at all four locations significantly lowered the perceived self-assessment of olfaction, while using the cotton swab only anesthesia in the middle meatus elevated threshold (P = 0.020), lowered discrimination (P = 0.015) and prolonged OERP (PEA, P = 0.008; H2S, P = 0.016), as well as CSSERPs latencies (CO2, P = 0.020). However, complete temporary anosmia was only achieved after applying 4% lidocaine into the olfactory cleft. Conclusions: Intranasal anesthesia applied with a swab reduced self-assessment of olfaction but was unable to produce anosmia. Psychometric test results were concordant with changes in chemosensory event-related potentials. Significance: Temporary anosmia is technically difficult to achieve but could be demonstrated for the first time using local anesthesia. Even though anesthesia influences self-assessment, measurable olfactory function can remain unchanged. (C) 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.