If a horse has a severe lower limb infection, the veterinarian must treat it immediately and aggressively, using the appropriate antibiotics. To do so, some use a technique called regional limb perfusion (RLP), in which the practitioner places a tourniquet above the injury site, isolating blood flow to the lower limb before injecting antibiotics directly into the vein below the tourniquet. This localizes high concentrations of appropriate antibiotics at the site of infection, injury, or fracture.

Using an anesthetic during this procedure is important, but some antibiotics become ineffective when combined with other drugs.

Aimee Colbath, VMD, of Colorado State University’s Orthopaedic Research Center, in Fort Collins, described her study evaluating a combination of the antibiotic amikacin with the anesthetic mepivacaine at the 2015 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas

Colbath noted that, because mepivicaine is an effect anesthetic, this combination could be very useful for repairing wounds or flushing synovial (joint) structures in the sedated, standing horse without having to resort to general anesthesia, which can have its own set of complications. Historically researchers have shown that combining amikacin with another antibiotic (ticarcillin) reduced amikacin levels and effectiveness, so Colbath wanted to be sure it wouldn’t be the case with mepivacaine, amikacin, and RLP. In this study she aimed to answer three questions:

  1. Does mepivacaine in this combination sufficiently reduce the mechanical nocioceptive threshold (essentially, the horse’s nerve cells’ abilit