Background and Objectives Alkalinization of local anesthetics has been shown to decrease the onset and prolong the duration of block for extraconal and intraconal application in ocular surgery. The objective of this study is to determine if alkalinization is also effective in sub-Tenon's block when hyaluronidase is added to the drug mixture.

Methods Twenty-nine patients were randomly assigned to 2 groups in a double-blind, prospective fashion to receive 5.125 mL of either a plain mixture LBH (2.5 mL lidocaine 2%, 2.5 mL bupivacaine 0.5%, 5 IU/mL hyaluronidase, and 0.125 mL isotonic saline) or pH-adjusted mixture LBH-PH (2.5 mL lidocaine 2%, 2.5 mL bupivacaine 0.5%, 5 IU/mL hyaluronidase, and 0.125 mL sodium bicarbonate 8.4%) of local anesthetics in a 1-quadrant sub-Tenon's block. Time to onset and time to full akinesia were determined every 30 seconds.

Results No difference was found between the study groups.

Conclusion pH adjustment of the local anesthetic mixture of lidocaine, bupivacaine, and hyaluronidase offered no additional benefit in sub-Tenon's technique in ocular procedures.