The study looked at the effect of mepivacaine, dexmedetomidine, or mepivacaine and dexmedetomidine infiltration over the palmar digital (PD) nerve on the response to mechanical force applied to between the heel bulbs. They used 8 mares that had no signs of lameness. This PD block is commonly used in equine practice to provide analgesia to the foot. The authors reported that the combination of mepivacaine (30 mg) and dexmedetomidine (250 µg) resulted in reduced sensation to pressure for twice as long as over mepivacaine alone (371 vs. 186 min, respectively). The dexmedetomidine alone did not change the response from baseline. The effect is thought to be independent of the drug’s effect on adrenoreceptors, rather due to blockade of the current produced by hyperpolarization of specific channels (HCN – hyperpolarization-activated cyclic nucleotide-gated channels). The limitations of the study were that blockade of pain in deeper tissues was not assessed and only a single dose dexmedetomidine was used. There were no signs of sedation in response to the treatment.
This study was funded in house by the Large Animal Clinical Sciences Department at the University of Tennessee.
Dexmedetomidine prolongs the duration of action of mepivacaine on anesthesia of the palmar digital nerves of horses. Cailey Nichols and others from the University of Tennessee in the USA