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

This research examined the impact of perfusate volume, or the liquid infused into a horse’s limb, on the concentrations of the antibiotic amikacin in the synovial fluid of the horse’s hind limb joints. The study found that perfusate volumes of 60 ml or 120 ml achieved desirable antibiotic concentrations for certain pathogens, but not for resistant ones, which calls for further research using higher doses of amikacin.

Methods

• The study followed a randomized crossover design using six adult horses.
• The method under investigation, known as saphenous intravenous regional limb perfusion (IVRLP), involved introducing amikacin, an antibiotic, into the horse’s limb for treating joint infections.
• Three different volumes of perfusate were used — 10 ml, 60 ml, and 120 ml — each diluted with 0.9% sodium chloride (NaCl) and mixed with one gram of amikacin.
• Samples of synovial fluid from three different joints in the horse’s hind limb were collected at two different time intervals — 15 minutes and 30 minutes after introducing the perfusate.
• The study defined two therapeutic concentrations of amikacin: 40 μg/ml for susceptible pathogens and 160 μg/ml for resistant pathogens.

Results

• There was no measurable difference in antibiotic concentration between the varying volumes of perfusate in any of the joints studied.
• The concentration of amikacin in the synovial fluid increased from the 15-minute mark to the 30-minute mark in all examples.
• Sufficient therapeutic levels (> 40 μg/ml) for treating susceptible pathogens were achieved in all instances using the 60 ml and 120 ml volumes. For the 10 ml volume, this level was only achieved in one specific joint, the hind limb distal interphalangeal joint.
• The therapeutic concentration (160 μg/ml) for the resistant pathogens was not achieved in any cases.

Conclusions

• The study concluded that a perfusate volume of 60 ml or 120 ml is recommended to treat infections due to susceptible pathogens in the joints of a horse’s hind limb.
• For resistant pathogens, these volumes did not result in effective treatment. Given these findings, additional investigation is recommended, possibly adjusting the dosage of amikacin or the perfusate volume.