Topical anesthesia with pH-adjusted versus standard lidocaine 4% for clear corneal cataract surgery

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Abstract
Purpose: To evaluate and compare the efficacy of a sodium-bicarbonate-adjusted preparation of lidocaine 4% (pH = 7.2) and standard lidocaine (pH = 5.2) for topical anesthesia in clear corneal cataract surgery. Setting: Department of Ophthalmology, University of Vienna, Austria. Methods: In a prospective, randomized, double-blind clinical trial, clear corneal cataract surgery was performed under topical anesthesia in 44 eyes of 34 patients. In 22 eyes, pH-adjusted lidocaine 4% was administered; in the other 22, standard lidocaine 4%. Aqueous and serum concentrations of lidocaine were measured by high-performance liquid chromatography and ultraviolet detection. Subjective pain was assessed using a visual analog scale of no pain (0%) to worst imaginable pain (100%). On the first postoperative day, visual acuity, intraocular pressure, and corneal staining with fluorescein were examined. Results: In the pH-adjusted lidocaine group, significantly higher lidocaine concentrations were found in the aqueous humor (15.06 μg/mL ± 8.2 [SD] versus 4.75 ± 3.5 μg/mL; P < .0001). In all samples (n = 8), serum lidocaine concentrations were below a minimum detectable level of 0.02 μg/mL. Subjective pain ratings were similar in the pH-adjusted and standard lidocaine groups (mean 9.73 ± 10.4% and 10.0 ± 15.4%, respectively). There was no significant between-group difference in intraoperative and postoperative outcomes. Conclusions: In this study, pH-adjusted lidocaine 4% was a safe, effective topical anesthetic for clear corneal surgery and had minimal local and systemic toxicity. Administration of pH-adjusted lidocaine 4% resulted in significantly higher aqueous humor lidocaine concentrations than administration of standard lidocaine 4%.