Comparison of preservative-free bupivacaine vs. lidocaine for intracameral anesthesia: a randomized clinical trial and in vitro analysis.

PURPOSE: To determine whether intracameral bupivacaine hydrochloride 0.5% is as effective as lidocaine hydrochloride 1.0% in controlling discomfort of patients during phacoemulsification and posterior chamber intraocular lens implantation. In rabbits, corneal endothelial cell function, ultrastructure, and viability were evaluated after in vitro perfusion of bupivacaine 0.5%.

METHODS: In a double-masked, controlled trial, 48 eyes of 48 patients with uncomplicated age-related cataract were randomly assigned to receive bupivacaine 0.5% or lidocaine 1.0% intracamerally before phacoemulsification with a posterior chamber intraocular lens. Outcome measures such as pain, visual acuity, amount of sedation, length of surgery, pupil size, intraocular pressure, corneal clarity, and anterior chamber reaction were compared. In laboratory studies, paired rabbit corneas were evaluated by endothelial cell perfusion with either bupivacaine 0.5%, bupivacaine 0.5% and glutathione bicarbonate Ringer solution in a 1:1 ratio or bupivacaine 0.5% buffered to a pH of 7.0. The paired control corneas were perfused with glutathione bicarbonate Ringer solution and rates of corneal swelling were determined. Cell ultrastructure and viability were also evaluated.

RESULTS: In the randomized trial, there was no significant difference in the pain patients had during surgery or in the early or late postoperative period. No statistically significant difference was seen between the two groups in terms of pupil size, intraocular pressure, corneal edema, anterior chamber reaction, or visual acuity immediately after the operation or on postoperative day 1. Paired rabbit corneas perfused with bupivacaine 0.5% and bupivacaine 0.5% buffered to a pH of 7.0 swelled significantly (P<.001, P = .009, respectively), and had corneal endothelial cell damage. Dilution of the bupivacaine 1:1 with glutathione bicarbonate Ringer solution prevented corneal edema and damage to the corneal endothelium. Endothelial cell viability was also decreased after perfusion of bupivacaine 0.5% (P<.001).

CONCLUSIONS: Clinically, bupivacaine 0.5% is as effective as lidocaine 1.0% for anesthesia during phacoemulsification and posterior chamber intraocular lens implantation. However, in vitro perfusion of bupivacaine 0.5% damaged the corneal endothelium of rabbits except when the drug was diluted 1:1 with glutathione bicarbonate Ringer solution. Surgeons who use 0.2 to 0.5 ml of intracameral bupivacaine 0.5% should be aware of its potential to cause endothelial cell damage because of its lipid solubility. The bupivacaine 0.5% should be diluted at least 1:1 with balanced salt solution before intracameral injection, followed immediately by phacoemulsification. The surgeon should ensure that the bupivacaine 0.5% is nonpreserved and packaged in single-use vials or flip-top containers.