Effect of perfusate volume on amikacin concentrations after saphenous intravenous regional limb perfusion in standing, sedated horses

Abstract

The objective of this study was to determine the influence of perfusate volume on synovial fluid amikacin concentrations in the joints of the hind limb after standing saphenous intravenous regional limb perfusion (IV-RLP). A randomized cross-over study design was utilized, and six adult horses served as animal subjects. Saphenous IV-RLP was performed in six standing horses with 1 g of amikacin diluted with 0.9% NaCl to volumes of 10 mL, 60 mL, and 120 mL. Samples of synovial fluid from the tarsocrural, metatarsophalangeal, and hind limb distal interphalangeal joints were collected at 15 and 30 minutes after perfusate administration. Concentrations of 40 µg/mL and 160 µg/mL were considered therapeutic for susceptible and resistant pathogens, respectively. No difference in synovial fluid amikacin concentrations was detected between volumes in any joint (p=0.4). All synovial fluid amikacin concentrations were higher at 30 minutes compared to 15 minutes (p=0.003). All median synovial fluid amikacin concentrations at 30 minutes were > 40 µg/mL using the 60 mL and 120 mL volumes. Synovial fluid amikacin concentrations > 40 µg/mL were only reached in the distal interphalangeal joint when the 10 mL volume was used. All median synovial fluid amikacin concentrations observed were < 160 µg/mL. Target concentrations for pathogens considered susceptible were consistently reached with perfusate volumes of 60 mL and 120 mL. However, median synovial fluid amikacin concentrations did not reach target levels for resistant pathogens. Perfusate volumes of 60 mL or 120 mL are recommended to treat infections due to susceptible pathogens in the joints of the distal hind limb. These results justify investigation of saphenous IV-RLP with different perfusate volumes using higher doses of amikacin.