Effects of Intraarticular Tramadol Administration on Biochemical and Cytological Properties of Equine Synovial Fluid: Comparison with Lidocaine

Problem statement: Diagnostic and therapeutic arthroscopic surgeries are procedures performed quite frequently in equine practice; and are considered to cause some degree of postoperative pain. The aim of the present study was to evaluate the equine synovial fluid biochemical and cytological changes following intra-articular administration of tramadol as a potential analgesic. Approach: Six adult healthy donkeys were selected after clinical examination. Synovial fluid samples were taken from both middle carpal joints after routine preparation. Tramadol 2 mg kg^-1 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, 48-192 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. Comparison of treatments was performed by nonparametric sign test and Wilcoxon rank sum test. Significance level was set to p≤ 0.05. Results: Neither detectable lameness nor special side effect was observed throughout the study. Mucin clot quality test and viscosity, the amount of total nucleated cell count, glucose, ALP and LDH revealed no significant differences between various sampling times between the tramadol and lidocaine groups (P>0.05). Neutrophil count, total protein, specific gravity and AST activity were significantly different. Conclusion/Recommendations: Despite the slightly different results compared to the lidocaine, it seems that the injection of tramadol into the middle carpal joint has no adverse effects on the synovial fluid composition in this joint and it can be considered a good analgesic after arthroscopic surgery with the lowest side effects in horses.