Effect of Regional Intravenous Limb Perfusate Volume on Synovial Fluid Concentration of Amikacin and Local Venous Blood Pressure in the Horse.

This study observes the impact of varying the volume of amikacin, an antibiotic, in regional intravenous limb perfusion in horses. The researchers sought to measure the antibiotic concentration in the synovial fluid in two distinct joints, its presence in the systemic circulation, and the regional intravenous pressure.

Introduction to the Study

• Regional intravenous limb perfusion (IVRLP) is a technique often employed in treating limb infections in horses. In this method, a tourniquet is applied to a limb and a high dose antibiotic is delivered into a vein, allowing higher drug concentrations at the infected site.
• This investigation examines the result of different delivery volumes of IVRLP amikacin, where it is injected through the cephalic vein of standing, sedated horses.
• The study aims to assess the impact these variations have on the concentrations of amikacin in the synovial fluid of the radiocarpal joint (RCJ) and distal interphalangeal joint (DIPJ), its presence in the systemic circulation, and the induced regional intravenous pressure.

Methodology

• Six adult horses served in this study. Each one received IVRLP with one gram of amikacin, with four potential perfusate volumes (10, 30, 60, or 120 ml) in a random order. A minimum of one week was ensured between sessions for washout.
• The perfusion was facilitated with 0.9% NaCl, a saline solution, applied post the application of a pneumatic tourniquet.
• Sampling of synovial fluid from the RCJ and DIPJ, along with systemic and regional venous blood, and the measurement of regional blood pressure, were all performed before the perfusion and then fifteen and thirty minutes after perfusion, but prior to the release of the tourniquet.

Results

• Different perfusate volumes did not lead to significant changes in average amikacin synovial fluid concentration.
• Regardless of volume, amikacin concentration was consistently higher in the DIPJ synovial fluid than in the RCJ, with the RCJ concentration not reaching the therapeutic level needed for resistant pathogens.
• However, DIPJ synovial fluid did reach the resistant pathogens’ therapeutic level when using the 10, 60, or 120 mL volumes.
• All volumes caused an immediate increase in the average regional intravascular pressure following perfusion.

Conclusion

• Performing cephalic IVRLP on horses utilizing 1 gram of amikacin diluted in varying volumes of 10-120 mL with 0.9% NaCl can achieve therapeutic levels of the medication in the synovial fluid sourced from the DIPJ, but not the RCJ.
• The results suggest that this method could be effective in treating infections in the DIPJ, but less so for those located in the RCJ.