Effect of alkalinization and/or hyaluronidase adjuvancy on a local anesthetic mixture for sub-Tenon's ophthalmic block

Background and objectives: pH adjustment and/or addition of hyaluronidase to local anesthetic drugs decrease the time to onset and prolong the duration of regional anesthetic techniques for ocular surgery. The objective of this study was to investigate whether these factors are effective also in sub-Tenon's block. Methods: Sixty patients were randomly assigned to four groups in a double blind, prospective fashion, and received 5.125 ml mixtures as follows: 2.5 ml lignocaine 2%, 2.5 ml bupivacaine 0.5% and 0.125 ml isotonic saline (group LB); 2.5 ml lignocaine 2%, 2.5 nil bupivacaine 0.5%, 15 IU hyaluronidase/ml and 0.125 ml isotonic saline (group LBH); 2.5 ml lignocaine 2%, 2.5 ml bupivacaine 0.5% and 0.125 ml sodium bicarbonate 8.4% (group LBpH); and 2.5 ml lignocaine 2%, 2.5 ml bupivacaine 0.5%, 15 IU hyaluronidase/ml and 0.125 ml sodium bicarbonate 8.4% (group LBHpH). This measurement was based on one quadrant sub-Tenon's block. Akinesia was assessed every 30 s. Results: No statistically significant differences were found between the groups regarding mean times to onset and to complete akinesia. Group LBH displayed a significantly lower frequency of patients experiencing pain and a lower need for rescue medication during surgery than the other groups. Conclusion: pH adjustment and/or addition of hyaluronidase to a mixture of lignocaine and bupivacaine did not shorten the time to onset of akinesia following sub-Tenon's technique. However, the addition of hyaluronidase was associated with a lower fraction of patients experiencing pain during surgery.