Effects of subconjunctival ropivacaine, liposomal bupivacaine, and mepivacaine on corneal sensitivity in healthy horses.
Authors: Gonzalez Gabriel A, Betbeze Caroline, Wills Robert, Eddy Alison, Mochal-King Cathleen, Fontenot Robin L
Journal: Veterinary surgery : VS
Summary
# Corneal Anaesthesia in Equine Ophthalmology: Comparing Three Local Anaesthetic Options When performing ocular procedures in horses, selecting an appropriate local anaesthetic requires understanding both efficacy and duration of action. Gonzalez et al. (2023) compared subconjunctival administration of three local anaesthetics—ropivacaine (0.5%), liposomal bupivacaine (1.3%), and mepivacaine (2%)—by measuring corneal touch threshold in twelve healthy mares using a Cochet-Bonnet esthesiometer, with saline controls and adverse event monitoring across 168 hours post-injection. Both ropivacaine and liposomal bupivacaine provided substantially prolonged anaesthesia, maintaining corneal insensitivity for approximately 168 minutes compared to just 31 minutes for control, whilst mepivacaine's 103-minute duration fell between these values but did not reach statistical significance relative to either alternative; notably, injection-site haemorrhage reduced anaesthetic duration regardless of agent used. All three medications were well tolerated with no serious adverse effects, suggesting that ropivacaine and liposomal bupivacaine represent clinically viable options when prolonged corneal analgesia is required for equine ophthalmic procedures, though practitioners should note these findings derive from healthy eyes and further investigation in diseased ocular tissue remains necessary.
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Practical Takeaways
- •Ropivacaine and liposomal bupivacaine offer 5-6 times longer corneal anesthesia (2.8-2.9 hours) than mepivacaine when injected subconjunctivally, making them superior for procedures requiring sustained ocular analgesia
- •All three agents are safe options in healthy eyes with no reported adverse effects, but avoid injection site hemorrhage as it significantly shortens anesthesia duration
- •Further research needed to confirm efficacy in diseased or inflamed eyes before applying these findings to clinical corneal pathology cases
Key Findings
- •Ropivacaine and liposomal bupivacaine provided mean total anesthesia times of 168.3 and 169.2 minutes respectively, significantly longer than control (30.7 minutes, p<0.001 and p=0.001)
- •Mepivacaine (103.3 minutes) showed no statistically significant difference from ropivacaine, liposomal bupivacaine, or control
- •Injection site hemorrhage reduced corneal anesthesia duration regardless of local anesthetic agent used (p=0.047)
- •No adverse effects were attributed to any of the three subconjunctival local anesthetic injections in healthy horses