Detomidine Sedation and Eye Pressure in Horses (AAEP 2010)

If your horse has to be sedated, the effect of that sedative on the fluid pressure within his eyes (intraocular pressure) might be the last thing you're worried about. Unless, of course, he is being sedated for an eye procedure--then this issue becomes quite important. At the 2010 American Association of Equine Practitioners convention, held Dec. 4-8 in Baltimore, Md., one veterinarian discussed a study of detomidine's effect on intraocular pressure in horses.

Some sedatives significantly increase intraocular pressure (IOP), which can cause further problems in compromised eyes such as globe (eye) perforation and glaucoma (permanent optic nerve damage due to elevated IOP), explained Dana Holve, DVM, of Eye Care for Animals in Tustin, Calif. Thus, it is helpful to know which sedatives might not have that effect, so you know which ones to select for ophthalmic (eye) procedures.

For the current study, investigators gave 15 healthy horses from six to 25 years of age complete physical and ophthalmologic exams, then recorded their IOPs before and 10 minutes afteradministering intravenous detomidine sedation at 0.02 mg/kg of body weight. They also measured seven horses 20 minutes after sedation. Holve found that IOP decreased by an average of 3.6 and 4.3 mmHg at 10 and 20 minutes after detomidine administration.

She also applied topical anesthesia to the eyes of a second group of horses to see if that modified detomidine's effect on IOP, and found that topical anesthesia did not change detomidine's IOP-reducing effects.

Additional variables that can artificially raise IOP in horses include manipulation of the eyes and nearby tissues, stress, and low head carriage (head held below the heart), she added.

"Detomidine causes a decrease in equine IOP," Holve concluded. "Given the many advantages of standing sedation and analgesia, detomidine is a safe alternative when performing ophthalmological procedures in the horse when increased IOP is a concern."

Areas for future investigation include evaluating the duration of the IOP reduction and determining if the effect is dose-dependent, she added.

The study manuscript is currently in press with the Journal of Veterinary Internal Medicine.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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