Evaluation of lidocaine for auriculopalpebral nerve block in dogs: Onset, duration, and effects on intraocular pressure and eye examination.

Objectives: Accurate intraocular pressure (IOP) measurement is essential for managing glaucoma, requiring tonometry. Local anesthesia is typically used, but nerve blocks may be needed for blepharospasm. This study investigated the efficacy of auriculopalpebral nerve block with lidocaine in achieving eyelid akinesia and its influence on IOP in dogs.

Animals and procedures: In a randomized, blinded trial, 12 healthy adult mixed-breed dogs (24 eyes) received either auriculopalpebral nerve block with 2% lidocaine (n = 12 eyes) or no block (n = 12 eyes). Tetracaine drops were used for topical anesthesia in half of blocked/non-blocked eyes, and the rest of the eyes got artificial tears as control. The impact of nerve block was evaluated through assessments of menace response, palpebral reflex, and IOP before the block, after drop instillation, and at 15-min intervals until block dissipation.

Results: Auriculopalpebral nerve block provided effective eyelid akinesia in 58.5% (7/12 eyes) at 15 min, reaching 91.7% (11/12 eyes) at 30 min, indicating peak efficacy. Subsequently, the block gradually diminished, with 66.7% (8/12 eyes) and 33.3% (4/12 eyes) maintaining akinesia at 45 and 60 min, respectively. Importantly, neither auriculopalpebral nerve block nor tetracaine administration significantly affected IOP measurements (p > .05).

Conclusions: Auriculopalpebral nerve block using lidocaine demonstrated efficient eyelid akinesia, peaking at 30 min postinjection. This technique proved to be safe with no notable alterations in IOP, suggesting its potential utility in canine ophthalmology for procedures requiring eyelid akinesia, particularly in the management of glaucoma where maintaining accurate IOP measurements is crucial for diagnosis, treatment, and monitoring the disease.