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.