Two intra-articular regimens of administration of tramadol after arthroscopic surgery in the horse: effects on pain control

The analgesic efficacy of intra-articular 50 mg tramadol is documented in human surgery. We aim to compare the analgesic effect of tramadol administered at two different doses in horses after arthroscopy. Twenty-two horses (413 ± 70 kg) underwent arthroscopy: after skin closure they received intra-articular tramadol, 1 mg kg-1, diluted in 10 (carpus, fetlock) or 20 (hock, stifle) mL 0.9% NaCl (group T), or 0.4% tramadol in the same final volumes (group TD). Pain was assessed pre-treatment (PRE), 15/30/60/120/360 minutes and 24 hours after standing with a modified Composite Pain Scale (CPS, total score 56; Bussières et al. 2008). Data were analyzed by Linear Mixed model (p ≤ 0.05) and reported as median, Q1-Q3. Group (p < 0.001), time (p < 0.001), their interaction (p = 0.05), and PRE (p < 0.05) affected CPS. At T15 (T: 8, 6-9; TD: 14, 11-15; p < 0.001), T30 (T: 9, 5-9; TD: 11, 11-12; p < 0.01), T60 (T: 6, 4-8; TD: 9, 8-9; p < 0.01), and T24 (T: 1, 0-3; TD: 4, 3-5; p < 0.01) CPS was higher in TD. The orthopaedic component of CPS (maximum score 6) was affected by group (p < 0.05), lesion’s severity (p < 0.001), and PRE (p < 0.001). At T24 (T: 0, 0-0; TD: 1, 1-1; p < 0.01) it was higher in TD. Intra-articular 0.4% tramadol was less effective than 1 mg kg-1 in horses after arthroscopy.