Cytotoxicity of lidocaine or bupivacaine on corneal endothelial cells in a rabbit model

Purpose: To investigate the corneal endothelial cytotoxicity of commercial formulations of agents used for intracameral anesthesia in cataract and other ocular surgery. Methods: Cultured corneal endothelial cells (CECs) of New Zealand White rabbits were exposed for 1 minute to balanced salt solution (control); Xylocaine (lidocaine) 1% E (with epinephrine), 2% E, 2%, or 4%; or Marcaine (bupivacaine) 0.5% or 0.5% spinal heavy. The degree of cytotoxicity was determined by in vitro staining with trypan blue and light microscopic evaluation of cell morphology. The effect of longer exposure (up to 16 minutes) to lidocaine 1% E was also investigated. Results: CECs were not significantly damaged by 1-minute exposure to lidocaine 1% E or 2% E; however, significant cytotoxicity was seen after 1-minute exposure to lidocaine 2% or 4% or bupivacaine 0.5% or 0.5% spinal heavy. Exposure to lidocaine 1 % E showed a trend toward time-dependent cytotoxicity that reached significance at 16 minutes. Conclusions: One-minute exposure to lidocaine 1% E or 2% E appears to be safe for cultured rabbit CECs, although longer exposures could cause time-dependent cytotoxicity, which should be considered in planning cataract or other ocular surgery. Because bupivacaine 0.5% and 0.5% spinal heavy cause cytotoxic effects within the first minute of contact with CECs, they should be used with great caution, if at all, in the anterior chamber of human eyes.