The effects of subconjunctival bupivacaine, lidocaine, and mepivacaine on corneal sensitivity in healthy horses.
Abstract: To compare the efficacy and duration of effect of three local anesthetics on corneal sensitivity when administered subconjunctivally in horses. Methods: Eight healthy adult horses. Methods: A randomized, masked, crossover study design was used, with a two-week washout period between trials. The subconjunctival space of the randomly selected eye was injected with 0.2 mLs of bupivacaine (0.5%), lidocaine (2%), mepivacaine (2%), or saline. All horses received each medication once. The contralateral eye served as a control. The corneal touch threshold (CTT) was measured in both eyes with a Cochet-Bonnet esthesiometer prior to sedation with xylazine, after sedation, and at 10-min intervals after subconjunctival injection until corneal sensitivity returned to baseline. The total time of decreased CTT and the maximum decrease in CTT were compared for each medication using a general linear mixed model (P < 0.05). Results: Total time of decreased CTT was 105.0 min for bupivacaine, 103.8 min for lidocaine, 138.8 min for mepivacaine, and 7.5 min for saline. All local anesthetics decreased CTT longer than saline (P < 0.001) and mepivacaine decreased CTT longer than lidocaine (P = 0.04). The mean minimum CTT was 1.67 cm for bupivacaine, 1.42 cm for lidocaine, and 0.73 cm for mepivacaine, which were all significantly less (P < 0.001) than saline (4.73 cm). No evidence of corneal toxicity was noted with any treatment. Conclusions: Subconjunctival injections of lidocaine, bupivacaine, and mepivacaine effectively and safely reduce corneal sensitivity in eyes of healthy horses for 1.5-2 h, and may be useful for providing perioperative analgesia for equine corneal procedures.
© 2017 American College of Veterinary Ophthalmologists.
Publication Date: 2017-12-12 PubMed ID: 29232029DOI: 10.1111/vop.12537Google Scholar: Lookup
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- Journal Article
- Randomized Controlled Trial
Summary
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The research article investigates how three local anesthetic drugs – bupivacaine, lidocaine, and mepivacaine – reduce the sensitivity of the corneas when injected into the conjunctiva, or whites of the eyes, of healthy horses. The study concluded that all three medicines were effective and safe, potentially useful for managing pain in equine corneal procedures.
Experimental Design
- The research experiment involved eight horses and used a randomised, masked, crossover study design. This approach ensures blinding to avoid any potential bias, and each horse received each treatment, but in a different order and with a two-week interval between trials to allow any effects from the previous trial to wear off.
- Each horse received an injection of either 0.2 mL of bupivacaine (0.5%), lidocaine (2%), mepivacaine (2%), or a saline solution, into the conjunctiva of one randomly selected eye. The opposite eye served as a control.
- Researchers used a Cochet-Bonnet esthesiometer to measure the corneal touch threshold (CTT) or corneal sensitivity in both eyes before and after sedation, and at 10-minute intervals post injection until the sensitivity returned to its baseline level.
Results of the Experiment
- The study found that all three anesthetics were more effective than the saline solution in decreasing CTT, and mepivacaine was more effective than lidocaine. The longest period of reduced CTT was observed with mepivacaine (138.8 minutes), followed by bupivacaine (105.0 minutes), and lidocaine (103.8 minutes).
- The mean minimum CTT was lowest with mepivacaine (0.73 cm), followed by lidocaine (1.42 cm), bupivacaine (1.67 cm), and each of these was significantly lower than the saline control (4.73 cm).
- Importantly, the researchers observed no signs of corneal toxicity with any of the treatments administered, indicative of the safety of these drugs for this application.
Conclusions
- The study concluded that subconjunctival injections of the three local anesthetics – bupivacaine, lidocaine, or mepivacaine – were effective in safely reducing corneal sensitivity in the eyes of healthy horses for a period of 1.5 to 2 hours.
- This discovery suggests their potential utility in providing perioperative pain relief during equine corneal procedures.
Cite This Article
APA
Jinks MR, Fontenot RL, Wills RW, Betbeze CM.
(2017).
The effects of subconjunctival bupivacaine, lidocaine, and mepivacaine on corneal sensitivity in healthy horses.
Vet Ophthalmol, 21(5), 498-506.
https://doi.org/10.1111/vop.12537 Publication
Researcher Affiliations
- Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
- Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
- Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
- Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
MeSH Terms
- Anesthetics, Local / pharmacology
- Animals
- Bupivacaine / pharmacology
- Cornea / drug effects
- Cross-Over Studies
- Double-Blind Method
- Female
- Horses / physiology
- Lidocaine / pharmacology
- Male
- Mepivacaine / pharmacology
- Ophthalmic Solutions / administration & dosage
- Ophthalmic Solutions / pharmacology
- Ophthalmologic Surgical Procedures / veterinary
- Reference Values
- Treatment Outcome
Grant Funding
- Mississippi State University College of Veterinary Medicine
- Office of Research and Graduate Studies
Citations
This article has been cited 4 times.- Wan SJ, Datta A, Flandrin O, Metruccio MME, Ma S, Nieto V, Kroken AR, Hill RZ, Bautista DM, Evans DJ, Fleiszig SMJ. Nerve-associated transient receptor potential ion channels can contribute to intrinsic resistance to bacterial adhesion in vivo. FASEB J 2021 Oct;35(10):e21899.
- Mora-Pereira M, Abarca EM, Duran S, Ravis W, McMullen RJ Jr, Fischer BM, Lee YP, Wooldridge AA. Sustained-release voriconazole-thermogel for subconjunctival injection in horses: ocular toxicity and in-vivo studies. BMC Vet Res 2020 Apr 16;16(1):115.
- Flandrin O, Yang Y, Abboud S, Kumar NG, Datta A, Jedel E, Bautista D, Evans D, Fleiszig SMJ. TRPV1 Defends the Healthy Murine Cornea Against Staphylococcus aureus Adhesion Independently of Sensory Nerve Firing. Invest Ophthalmol Vis Sci 2025 Jul 1;66(9):61.
- Flandrin O, Yang Y, Abboud S, Kumar NG, Datta A, Jedel E, Bautista D, Evans D, Fleiszig S. TRPV1 Defends the Healthy Murine Cornea against Staphylococcus aureus Adhesion Independently of Sensory Nerve Firing. bioRxiv 2025 Apr 12;.
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