Evaluation of local anesthesia agents using a new force-sensitive lid speculum

Three commonly used injection anesthetics, bupivacaine .75%, mepivacaine 2%, and lidocaine 2% were evaluated for onset, completeness and duration of akinesia following modified O'Brien facial nerve block, using a new force-sensitive lid speculum. All three agents provided facial akinesia that was profound within six minutes of the time of injection. The onset and the depth of anesthesia were roughly the same with all three agents. However, bupivacaine induced akinesia of greatest duration, lasting up to six hours, the time of final measurement in this study. Akinesia produced by mepivacaine was adequate for about 90 minutes, and lidocaine for 15-30 minutes. A newly-described force-sensitive speculum was utilized in this study. It is an effective instrument for measuring completeness of akinesia, and may have clinical usefulness.