Pain relief from lidocaine eye injection during dog cataract surgery

Abstract

OBJECTIVE: To evaluate the intraoperative and postoperative analgesic effects of intracameral lidocaine hydrochloride injection in dogs undergoing phacoemulsification. ANIMALS: 12 healthy Beagles with healthy eyes. PROCEDURES: Dogs were randomly assigned to receive 1 of 2 intracameral injections: 2% lidocaine hydrochloride solution (0.3 mL) or an equivalent amount of balanced salt solution (BSS). All dogs were treated with acepromazine (0.05 mg/kg, i.v.) and cefazolin (30 mg/kg, i.v.), and tropicamide drops were topically applied to the eyes. Anesthesia was induced with propofol and maintained with isoflurane. The initial end-tidal isoflurane concentration was maintained at 1.2%. Heart rate, respiratory rate, arterial blood pressure, esophageal temperature, inspired and end-tidal isoflurane concentrations, and oxygen saturation were recorded every 5 minutes. The allocated agent was injected intracamerally after aspiration of the same volume of aqueous humor. Ten minutes after injection, phacoemulsification was performed. After surgery began, the isoflurane concentration was adjusted according to heart rate and mean arterial blood pressure. Pain scores were recorded before surgery and at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, 8, 16, and 24 hours after extubation. RESULTS: Isoflurane requirements were significantly higher in the BSS group than in the lidocaine group. Mean +/- SD time to administration of supplementary analgesia was significantly shorter in the BSS group (1.4 +/- 1.2 hours) than in the lidocaine group (4.9 +/- 1.2 hours). CONCLUSIONS AND CLINICAL RELEVANCE: Intracameral lidocaine injection had significant analgesic effects in dogs undergoing cataract surgery. Results of this study suggest the value of intracameral lidocaine injection as an analgesic for intraocular surgery in dogs.