Toxicity of intraocular lidocaine and bupivacaine

PURPOSE: To study the toxicity of intraocular lidocaine, bupivacaine, and a combination of the two anesthetics. METHODS: The right eyes of 34 rabbits were divided into eight groups, and each was injected intravitreally with 0.2 ml of lidocaine hydrochloride in a 2%, 1%, 0.5%, or 0.25% concentration, or bupivacaine hydrochloride in a 0.75%, 0.5%, or 0.25% concentration, or a 1:1 mixture of lidocaine 2% and bupivacaine 0.75%. The left eyes of four of these rabbits received an injection of balanced saline solution. Electroretinograms were recorded before injection and 30 minutes, 90 minutes, 3 hours, 6 hours, 24 hours, and 1 week after injection. The amplitude and the implicit time were analyzed. The rabbits were killed 1 week after injection and the eyes evaluated histo logically. RESULTS: No adverse clinical reaction and no histologic abnormality was observed in any of the nine groups after injection. The a- and b-waves of the electroretinograms in the control group injected with balanced saline solution, and the a-waves of the experimental groups that received injections of lidocaine, bupivacaine, or the mixture, were normal. The b-waves of the experimental groups demonstrated a marked decrease in the amplitude and an increase (P <.05) in the implicit time after intravitreal injection. Electroretinogram responses recovered within 24 hours. CONCLUSIONS: Intravitreal injection of 0.2 ml of lidocaine up to 2%, or of bupivacaine up to 0.75%, and the mixture of lidocaine 2% and bupivacaine 0.75%, induced reversible electroretinogram changes in the rabbit retina. No histologic abnormalities were observed.