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Objectives: To determine the effects of experimentally induced synovitis of the radiocarpal joint on the intra-articular pharmacokinetics and pharmacodynamics of amikacin after intravenous regional limb perfusion (IVRLP)., Study Design: Randomized crossover experimental design., Animals: Adult horses (n = 8)., Methods: Horses were randomly assigned into 2 trials: synovitis and no-synovitis. Radiocarpal joint synovitis was induced with lipopolysaccharide 6 hours before IVRLP. IVRLP (5-mg/kg amikacin qs 60 mL) was performed with a pneumatic tourniquet under general anesthesia. Synovial fluid was obtained before and 0.5, 1, 3, 5, 12, 24, 48 hours after IVRLP. Amikacin concentrations at each time point and pharmacokinetic values were compared between synovitis and no-synovitis trials with Student's t-test., Results: Amikacin synovial fluid concentrations indicated suspected tourniquet failure on 3 occasions (2 synovitis, 1 no-synovitis) on 3 different horses. Data from both trials in these 3 horses were excluded from further analysis. Observed time to maximal concentration (T(max); mean ± SD = 54 ± 13.42 min) was reached earlier in synovitis joints (5/5, 30 min) than in no-synovitis joints (1/5, 30 min and 4/5, 1 h; P = .0476) (P = .0161). Mean observed maximal concentration (C(max)) was higher in synovitis joints (144.48 ± 43.17 μg/mL) than in no-synovitis joints (60.02 ± 28.81 μg/mL; P = .0301). The recommended C(max): minimum inhibitory concentration ratio of 8 was achieved in 3/5 of the successfully perfused joints with induced synovitis, but this ratio was not achieved in any of the clinically normal joints., Conclusion: Synovitis of the radiocarpal joint resulted in an earlier observed T(max) and higher observed C(max) of intra-articular amikacin after IVRLP compared with normal joints., (© Copyright 2011 by The American College of Veterinary Surgeons.)

Objective: To determine (1) if clinically useful concentrations of amikacin sulfate can be obtained in synovial fluid during regional limb perfusion (RLP) performed above the carpus in standing sedated horses and (2) to determine the efficacy of 3 tourniquet types (narrow rubber [NR], wide rubber [WR], pneumatic [PN])., Animals: Horses (n=9)., Methods: Bilateral forelimb RLP with amikacin sulfate (2.5 g) were administered through the cephalic vein in standing sedated horses. Limbs were randomly assigned to the 3 tourniquet types (NR, WR, PN) applied above the carpus. Metacarpophalangeal synovial fluid was obtained 0.5 hour after perfusion. Amikacin concentration in the synovial fluid was detected using fluorescence polarization immunoassay., Results: Mean synovial concentrations of amikacin in the PN (mean 236 μg/mL; range 23-913 μg/mL) and WR (mean 64.2 μg/mL; range 7-315 μg/mL) were significantly higher (P=.000 and .032, respectively) than the NR tourniquet (mean 2.1 μg/mL; range 0.9-3.3 μg/mL)., Conclusions: The PN tourniquet resulted in the highest synovial fluid amikacin concentrations in all horses, although administration with PN and WR tourniquets achieved adequate amikacin concentrations. NR tourniquet is ineffective and should not be used for RLP above the carpus in the standing horse., (© Copyright 2010 by The American College of Veterinary Surgeons.)

Objective: To determine whether topical application of 1% diclofenac sodium cream would decrease inflammation at sites of IV regional limb perfusion (IVRLP) in healthy horses., Animals: 6 healthy adult horses (12 forelimbs)., Procedures: Bilateral IVRLP with 2.5 g of amikacin sulfate was performed twice in each horse, with 24 hours between each session. Horses were treated with topical 1% diclofenac liposomal cream (treated limbs) or a placebo cream (control limbs). All injection sites were evaluated before the first IVRLP session and 24 hours after the second session by means of ultrasonographic examination by a trained ultrasonographer who was unaware of the treatment received. Circumferential measurements and subjective visible inflammation scores were recorded by a veterinarian who was also unaware of treatment received., Results: After IVRLP, control limbs had a significantly greater increase in subcutaneous thickness, compared with treated limbs. Ultrasonographic and visual assessment scores were significantly higher in control versus treated limbs. The mean change in limb circumference was greater, but not significantly so, in control limbs, compared with treated limbs., Conclusions and Clinical Relevance: Topical application of 1% diclofenac sodium liposomal cream to sites of IVRLP in healthy horses decreased inflammation as judged by visual assessment and ultrasonography. Decreased inflammation may allow extended use of IVRLP and may result in a reduction in pain in treated horses.