XXXI The Effects of Anesthetics upon the Ear

Abstract

In earlier papers 7,8 it was pointed out that the use of topical anesthetics is considered by many surgeons to be a suitable method for anesthetizing structures of the ear during surgery. The favorable conditions accompanying the use of topical anesthesia have been dis cussed by Pitkin 5 and Goodman and Gillman. 3 Among the favorable conditions which they discuss, the fact that the action of topical anesthetics is reversible and is followed by complete recovery is especially critical. It is clear that any topical anesthetic which ad versely affects the sensitive structures of the cochlea is totally unsuited for otological surgery. Whereas Goodman and Gillman 3 specifically point out that the action of local anesthetic drugs is followed by complete recovery of nerve function with no evident structural dam age to nerve fibers or adjacent cells, data obtained in this laboratory indicate that a number of topical anesthetics produce very serious disruptions of the normal functioning of the cochlea when these drugs are applied to middle ear structures. The major effect noted involves a reduction in the magnitude of the electrical response of the cochlea. These losses have very serious implications for hearing.The manner in which the cochlea transduces acoustical energy so as to stimulate the auditory nerve has been a source of speculation for many years. However, many auditory theorists have come to believe that the electrical response of the cochlea directly triggers the auditory nerve. 1 · 2 · 4 · 0 · 10 According to the electrical hypothesis of audi tory nerve stimulation, any reduction in the magnitude of the cochlear response cannot help but have deleterious effects upon hearing. Ex perimental evidence is now available to show that the magnitude