Effects of Intravenous Flunixin Meglumine, Phenylbutazone, and Acupuncture on Ocular Pain Scores in the Horse: A Pilot Study

In this controlled, blinded, randomized block pilot study, the main objective was to evaluate the effectiveness of intravenous flunixin meglumine, phenylbutazone, and acupuncture on ocular pain relief using a multifactorial pain scale in the horse. Four experimental horses underwent corneal epithelial debridement in four sessions, when a randomly selected treatment or a control was used. All horses were pain scored before corneal wounding, then at 18 time points, when 11 parameters were allocated. Differences in the area under the curve of pain scores between the treatment groups were analyzed using a paired t-test. Corneal pain was significantly reduced by the third postoperative day (P = .03) when all 11 parameters were considered. Five ocular signs showed significant differences between treatments and proved to be good indicators of ocular pain. The other parameters (heart rate, corneal touch threshold, respond to palpation, and three behavioral parameters) were determined to be irrelevant when evaluating the degree of pain. When considering the five ocular signs, the lowest pain score was attributed to the flunixin meglumine group (1114), followed by the electroacupuncture group (1356), the phenylbutazone group (1397), and the control group (1580). There were significantly lower pain scores (P = .01) in the flunixin meglumine group when compared with those recorded in the control group during the first 46 hours. Flunixin meglumine was the most effective treatment at reducing ocular pain in the horse. In the future, a reduction in the number of pain score parameters and more precisely defined image evaluation criteria could be used.

Intracameral Use of Nepafenac: Safety and Efficacy Study

PURPOSE

To test the intracameral safety of nepafenac and its efficacy in inhibiting prostaglandin synthesis during phacoemulsification surgery.

METHODS

The safety evaluation was conducted in normal eyes of rabbits, 0.1ml of 0.3% and 1% nepafenac was injected intracamerally. Extensive studies to detect adverse response ranged from a gross examination of eyes under slit lamp biomicroscope, fluorescein dye test, Schirmer tear test, test for corneal sensitivity, intraocular pressure measurement (IOP), specular microscopy, electroretinography(ERG), and histopathological examination of intraocular tissues. Efficacy of nepafenac was studied by intracameral injection of 0.1%, 0.3% nepafenac, nepafenac 0.3%+1% lignocaine, and 1% lignocaine alone, before phacoemulsification surgery and intraoperative mydriasis along with PGE2(ProstaglandinE2) secretion were recorded.

RESULTS

Single 0.1ml of 0.3% or 1% nepafenac did not significantly (p > 0.05) alter physiological parameters and histology of cornea, iris, and retina. Nepafenac 0.3% effectively inhibited PGE2 secretion. No significant (p > 0.05) prevention of miosis was recorded with 0.1% or 0.3% nepafenac. However, a combination of 0.3% nepafenac + 1% lignocaine and 1% lignocaine alone significantly (p < 0.05) arrested miosis during the intraoperative period.

CONCLUSION

An intracameral concentration of up to 1% nepafenac does not adversely affect the rabbit eye. Nepafenac fails to prevent miosis but inhibits prostaglandin release during phacoemulsification surgery.

Effects of peribulbar anesthesia (sub-Tenon injection of a local anesthetic) on akinesia of extraocular muscles, mydriasis, and intraoperative and postoperative analgesia in dogs undergoing phacoemulsification

OBJECTIVE

To evaluate the effects of peribulbar anesthesia (sub-Tenon injection of lidocaine hydrochloride) on akinesia of extraocular muscles, mydriasis, and intraoperative and postoperative analgesia in dogs undergoing phacoemulsification.

ANIMALS

14 Beagles with ophthalmically normal eyes.

PROCEDURES

A blinded randomized controlled trial was performed. Dogs were anesthetized and assigned to 2 treatments: concurrent sub-Tenon injection of 2% lidocaine hydrochloride solution (2 mL) and IV injection of saline (0.9% NaCl) solution (0.02 mL/kg; lidocaine group [n = 7]) or concurrent sub-Tenon injection of saline solution (2 mL) and IV injection of 0.2 mg of atracurium/kg (0.02 mL/kg; control group [7]). Pupils were dilated by topical application of a combined tropicamide and phenylephrine ophthalmic solution. Ten minutes after the injections, pupil diameter was measured and phacoemulsification was performed. End-tidal isoflurane concentration was used to evaluate intraoperative pain. Subjective pain scores were recorded during the postoperative period.

RESULTS

Akinesia was induced and maintained throughout the surgery in all eyes. Mean ± SD pupil diameter was significantly greater in the lidocaine group (13.7 ± 0.7 mm) than in the control group (12.2 ± 0.8 mm). Isoflurane requirements were significantly lower in the lidocaine group than the control group. However, postoperative pain scores were not significantly different between the groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Sub-Tenon injection of lidocaine was an effective method for inducing akinesia of extraocular muscles, mydriasis, and intraoperative analgesia for phacoemulsification in dogs. Therefore, this could be another option for surgical field exposure and pain management during phacoemulsification in dogs.