Analgesic effects of epidural administration of hydromorphone in horses.
OBJECTIVE
To evaluate the effects of epidural administration of hydromorphone on avoidance threshold to noxious electrical stimulation of the perineal, sacral, lumbar, and thoracic regions in horses.


METHODS
6 healthy adult horses.


METHODS
Horses were assigned to receive hydromorphone (0.04 mg/kg) or a control solution (20 mL of sterile water) administered epidurally into in the first intercoccygeal space. Treatments were administered at time intervals of > or = 7 days. Electrical stimulation was applied for 6 hours after epidural injection over the dermatomes of the perineal, sacral, lumbar, and thoracic regions, and the avoidance threshold voltage was recorded.


RESULTS
Administration of sterile water did not change the avoidance threshold. Hydromorphone significantly increased the avoidance threshold by 20 minutes after injection, which lasted until 250 minutes after epidural administration in the perineal, sacral, lumbar, and thoracic regions. Profound analgesia (avoidance threshold > 40 V) was achieved only in the perineal region at 60 minutes after epidural administration of hydromorphone. Analgesia for all dermatomes was considered moderate for 250 minutes after epidural injection.


CONCLUSIONS
Epidural administration of hydromorphone increases the avoidance threshold to noxious electrical stimulation in the perineal, lumbar, sacral, and thoracic regions in horses for 250 minutes after injection. Hydromorphone epidural administration may prove useful in the management of horses with pain of moderate to mild intensity.
Natalini
Cláudio C
CC
Equine Health Studies Program, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
Linardi
Renata L
RL
D015360:Analgesia, Epidural / Q000662:veterinary*; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D004558:Electric Stimulation; D006736:Horses / Q000502:physiology*; D004091:Hydromorphone / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects*
D000701:Analgesics, Opioid; D004091:Hydromorphone