Effect of intrathecal amikacin administration and repeated centesis on digital flexor tendon sheath synovial fluid in horses.
Authors: Dykgraaf Susanne, Dechant Julie E, Johns Jennifer L, Christopher Mary M, Bolt David M, Snyder Jack R
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Intrathecal amikacin therapy and repeated needle sampling of the digital flexor tendon sheath (DFTS) both trigger measurable synovial fluid changes in horses, yet distinguishing iatrogenic inflammation from genuine infection remains clinically challenging. Researchers administered either amikacin (250 mg) or lactated Ringer's solution into the DFTS of eight horses in a crossover design, then repeatedly sampled synovial fluid over 72 hours to track total nucleated cell count, total protein concentration, and cell populations. Both treatments provoked similar inflammatory responses—peak increases in neutrophil percentages, total protein, and cell counts occurred within 12–24 hours of injection before declining toward baseline—indicating that needle penetration itself, rather than the antimicrobial agent, drives the initial synovial reaction. Despite these measurable changes in synovial fluid analytes, horses showed no lameness at walk, and values normalised within 24 hours in most cases, though the authors emphasise that individual variation exists: some horses mounted disproportionately marked responses that could be misinterpreted as sepsis. Clinically, this work underscores the importance of baseline synovial samples before treatment, careful timing of follow-up sampling (avoiding the 12–24 hour peak), and recognition that elevated cell counts and protein alone cannot distinguish therapeutic injection effects from infection without supporting clinical signs and culture results.
Read the full abstract on PubMed
Practical Takeaways
- •Both needle injection alone and intrathecal amikacin cause transient synovial inflammation in normal tendon sheaths—this mild response is expected and typically resolves quickly without clinical lameness
- •Interpret elevated synovial fluid values cautiously in the first 24 hours post-injection, as increases may reflect procedural inflammation rather than infection, though some horses show exaggerated responses warranting close monitoring
- •For practitioners: repeated centesis and intrathecal therapy appear safe in normal sheaths, but individual variation exists—monitor individual horses closely and consider baseline samples before treatment when possible
Key Findings
- •Both amikacin and lactated Ringer's solution injection caused mild increases in synovial fluid total protein, nucleated cell count, and neutrophil percentages that peaked at 12-24 hours post-injection
- •No significant difference was found between amikacin and LRS treatment effects on synovial fluid parameters
- •Synovial inflammation resolved within 12-24 hours without causing lameness at walk in most horses, though some individuals developed marked analyte increases mimicking sepsis