Intra-articular ketamine administration in equine midcarpal joint: clinical, biochemical and cytological evaluations

Providing suitable analgesia following diagnostic and therapeutic arthroscopic surgeries, that are
considered to cause some degree of postoperative pain, is a necessity in equine practice. The aim of the
present study was to evaluate the equine synovial fluid biochemical and cytological changes as well as
clinical assessments of the joint following intra-articular administration of ketamine. Six adult healthy
donkeys were selected after clinical examination. Synovial fluid samples were taken from both middle carpal
joints after routine preparation. Ketamine 2 mg/kg and 100 mg lidocaine 2% were administered to the right
and left joints, respectively. Synovial fluid collection from the joints was performed at 12, 24, 48 and 192 h
after medication. Cytological examination, total protein, glucose, specific gravity, alkaline phosphates (ALP),
aspartate aminotransferase (AST), lactate dehydrogenase (LDH), viscosity and quality of mucin clot were
measured. Joint circumference, flexion test and lameness examination, stimulation of the joint skin area and radiographic examination were performed as clinical evaluations. Comparison of treatments was performed by nonparametric sign test and Wilcoxon rank sum test. Significance level was set to P≤0.05. In the ketamine group, increased joint circumference, positive flexion test and negative response to the ball-point pressure of the joint skin area were seen, unlike that of lidocaine. Mucin clot quality test and viscosity, the amount of total nucleated cell count (TNCC), mononuclear and neutrophil count, specific gravity, total protein content, ALP, AST and LDH of the ketamine treated joints revealed considerable differences between various sampling times compared to the 0 time and also between the ketamine and lidocaine groups (P>0.05). It was concluded that intra-articular ketamine administration in equine carpal joint resulted in acute inflammatory changes, and failed to demonstrate analgesia; therefore, it is not safe to the joint environment and is not recommended as a local analgesic following arthroscopic surgeries.