Comparison of systemic atracurium, retrobulbar lidocaine, and sub-Tenon's lidocaine injections in akinesia and mydriasis in dogs.

OBJECTIVE: To compare the effect of sub-Tenon's lidocaine injections (ST) on akinesia and mydriasis to those of systemic atracurium (AT) and retrobulbar lidocaine injections in dogs. ANIMAL STUDIED: Ten healthy beagle dogs without apparent ocular disease. PROCEDURES: Three treatments were performed on 10 beagle dogs with a minimum 7-day washout period: intravenous injection of AT (0.2 mg/kg, AT group); retrobulbar (RB) injection of 2% lidocaine (2.0 mL, RB group) in one eye; and sub-Tenon's injection of 2% lidocaine (2.0 mL, ST group) in the opposite eye. When the akinesia was not obtained within 10 min, an additional 1 mL of lidocaine was administered in the RB and the ST groups. RESULTS: Onset of akinesia in the AT (1.5 ± 0.9 min) and the ST (3.8 ± 5.8 min) groups was significantly shorter than that in the RB group (9.0 ± 6.5 min). Duration of akinesia in the ST group (116.2 ± 32.8 min) was longer compared to the AT (60.6 ± 23.6 min) and the RB (89.0 ± 52.8 min) groups, even though there was only a significant difference between the AT and the ST groups. Mydriasis was achieved in five eyes in the RB group and nine eyes in the ST group. There was no significant difference in onset (3.6 ± 3.1 and 2.9 ± 2.3 min, respectively) or duration (91.4 ± 31.9 and 102.1 ± 35.8 min, respectively) of mydriasis between the groups. CONCLUSIONS: Sub-Tenon's lidocaine injections provide excellent akinesia and mydriasis compared to systemic AT and retrobulbar lidocaine injections. Therefore, sub-Tenon's anesthesia could be an alternative to the systemic administration of neuromuscular blockers and retrobulbar anesthesia for ophthalmic surgery in dogs.