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Experimental basis for lidocaine therapy in cochlear disorders.
E Laurikainen1, A L Nuttall, J M Miller
1Kresge Hearing Research Institute, University of Michigan, Ann Arbor.
Acta Oto-Laryngologica
|September 1, 1992
Summary
Lidocaine applied locally to the inner ear affects auditory nerve function, particularly at high frequencies. Systemic lidocaine does not impact cochlear potentials, suggesting it does not cross the blood-cochlear barrier.
Area of Science:
- Ototoxicology
- Neuropharmacology
- Auditory Neuroscience
Background:
- Lidocaine hydrochloride is a common anesthetic.
- Its precise effects on the inner ear are not fully understood.
- Investigating local vs. systemic administration is crucial.
Purpose of the Study:
- To elucidate the effects of lidocaine on cochlear potentials and blood flow.
- To differentiate effects based on administration route: intravenous (i.v.), anterior inferior cerebellar artery (AICA), and round window (RW).
- To explore lidocaine's pharmacological action within the inner ear.
Main Methods:
- Administered lidocaine hydrochloride via i.v., AICA microinfusion, and RW application in guinea pigs and rats.
- Measured cochlear potentials (Compound Action Potentials - CAP, Cochlear Microphonics - CM, Endocochlear Potentials - EP).
- Monitored cerebral blood flow (CBF) and systemic blood pressure (BP).
Main Results:
- Local RW lidocaine application caused dose-dependent decreases in CAP and CM, especially at high frequencies.
- Topical lidocaine did not alter basal EP, suggesting direct effects on the organ of Corti.
- Neither i.v. nor AICA lidocaine affected CAP or CM; i.v. lidocaine reduced BP, proportionally affecting CBF.
Conclusions:
- Lidocaine exerts specific pharmacological effects on the inner ear beyond simple nerve anesthesia.
- Local application impacts cochlear hair cell function.
- Systemic lidocaine likely does not cross the blood-cochlear barrier, and its cochlear effects are not mediated by altered ion transport or CBF changes.