BACKGROUND AND OBJECTIVES: Enantiomeric mixtures of bupivacaine in different formulations, S75-R25 or S90-R10, were proposed aiming at reducing the cardiotoxicity and with a satisfactory motor blockade. The aim of this study was to compare the length of time until the appearance of the motor blockade and its degree using 50% enantiomeric excess 0.5% bupivacaine (S75-R25), 0.5% racemic bupivacaine, and 2% lidocaine for facial nerve block by the O'Brien technique. METHODS: Forty-five patients, over 60 years old, scheduled for the surgical treatment of cataracts under retrobulbar block preceded by O'Brien paralysis participated in this study. Patients were randomly divided in three groups of 15 patients, according to the anesthetic used for the facial nerve block: Group L (Lidocaine), Group B (Bupivacaine), and Group M (S75-R25). Three milliliters of the solution were administered. The length of time for motor blockade to become apparent and the degree of the motor block (Grades 1, 2, and 3) were evaluated 15 seconds after the injection and every 15 seconds until it reached 180 seconds. RESULTS: The initial manifestations of the blockade were faster (15 s) in Group L. There were no differences between Groups B and M. Every patient in Group L showed Grade 3 motor block in up to 60 seconds, which was faster than Groups B and M (120 and 135 seconds, respectively). Groups B and M had similar behavior during the study, without any statistically significant difference. At 180 seconds, the incidence of Grade 3 motor block was similar in all three groups. CONCLUSIONS: The beginning of the motor blockade and its maximal degree were achieved faster with 2% lidocaine. The same degree was achieved by racemic bupivacaine and S75-R25, but it took longer. These two anesthetics showed the same behavior regarding the latency and the maximal degree of motor block, but at the end of 180 seconds there were no differences in the intensity of the blockade among the three groups.
ANESTHETICS, Local; ANESTHETIC TECHNIQUES, Regional
