Dexmedetomidine prolongs the duration of action of mepivacaine on anesthesia of the palmar digital nerves of horses.

The research paper investigates the effects of combining mepivacaine and dexmedetomidine in anesthetizing the palmar digital nerves in horses, showing that the combination prolongs the effect of the anesthetic.

Objective and Methodology

• The study aimed to determine whether a combination of dexmedetomidine and mepivacaine would prolong the duration of nerve blockade against mechanical force in the palmar digital nerves (PDN) of horses compared to using either drug alone.
• The research used a randomized, crossover, blinded, and experimental study design involving eight healthy mares without lameness.
• In each experiment, the PDNs of a single forelimb were anesthetized by perineural injection with either 30mg of mepivacaine alone, 250µg of dexmedetomidine alone, or a combination of 30mg mepivacaine and 250µg of dexmedetomidine.
• Each horse received all three treatments in random order, with a gap of at least two weeks between treatments to prevent carry-over effects.

Measurement Procedure and Results

• Mechanical nociceptive threshold, or the sensitivity to pain caused by force, was measured using a digital force gauge at an area between the heel bulbs of the horse’s foot.
• Measurements were taken before the treatment and at 15-minute intervals afterwards, to track the onset and duration of effect.
• Overall, the mean duration of sensory blockade (numbness) was twice as long when mepivacaine was combined with dexmedetomidine (371 minutes), compared to using mepivacaine alone (186 minutes).
• Dexmedetomidine used alone did not change the nociceptive threshold significantly from its baseline value and caused no clinical signs of sedation.

Conclusions

• The results suggest that combining mepivacaine with dexmedetomidine for PDN blockade can extend the duration of relief from digital pain in horses.
• This finding could improve veterinary anesthesia strategies for procedures involving the horse’s digits, potentially offering longer-lasting and more effective pain relief.