Late effects of topical anesthetics on the healing of guinea pig tympanic membranes after myringotomy.

BACKGROUND The optimal local anesthetic for myringotomies or the insertion of tympanostomy tubes in adults should be easy and rapid to use, be painless during application, provide good anesthesia, be reversible, be inexpensive, and not cause any long-term damage to the tympanic membrane (TM). OBJECTIVE To evaluate the histologic effects of topical anesthetic agents on the healing of the TM after myringotomy. METHODS Sixty male albino guinea pigs were randomly assigned to 1 of 5 groups. Of the 5 groups, 2 were used as controls: one group underwent a myringotomy and the other group did not. The remaining 3 groups had both TMs treated with a topical anesthetic (phenol, tetracaine base, and eutectic mixture of lidocaine and prilocaine in a cream) prior to myringotomy. All TMs were inspected periodically and then harvested at 3 months or 6 months postoperatively for histologic examination. RESULTS The TMs of the group treated with tetracaine appeared the most normal at 6 months (P=.001). However, histologic evaluation failed to demonstrate any significant differences in the thickness of the TM or the lamina propria (P=.45), the amount (P=.80) and orientation (P=.07) of collagen, or the number of infiltrating lymphocytes (P=.70). CONCLUSION Based on the histologic findings, all 3 topical anesthetic agents appear to cause equivalent changes to the TM when used for a myringotomy.