Lower limb injuries in horses can be complicated to treat, not only because of the area’s many complex joints but also due to a limited blood supply that makes it difficult for systemic antibiotics to reach affected tissues. Veterinarians often turn to a technique called regional limb perfusion, or RLP, in which they place a tourniquet on the limb and inject antibiotic into a vein below it to deliver treatment directly where it needs to go.

“When performing regional limb perfusion, tourniquet applications of up to 25 to 30 minutes have been reported in previous studies,” said Isabelle Kilcoyne, MVB, Dipl. ACVS, an equine surgeon at the University of California, Davis, School of Veterinary Medicine. However, researchers didn’t know how long it takes for the drug to reach peak synovial (within the joint) concentration and the optimal time to leave the tourniquet in place. If a shorter application time were just as effective, she said, it could improve the horse’s comfort, require less sedation, and be more efficient overall.

So, she and colleagues recently evaluated how long it takes amikacin—a drug that’s effective against most bacteria implicated in wounds or synovial sepsis—to reach peak synovial concentration in healthy adult horses’ coffin joints. She presented the results of the study at the 2017 American Association of Equine Practitioners Convention, held Nov. 17-21 in San Antonio, Texas.

The research team diluted 2 g of amikacin with 60 mL of saline and administered it via RLP. They collected synovial fluid samples from joints at 5, 10, 15, 20, 25, and 30 minutes after completely instilling the medication and removed the tourniquet after taking the 20-minute sample. The team also collected blood samples from the jugular 5, 10, 15, 19, 21, 25, and 30 minutes after administration to check for medication leakage from the RLP site