| dc.description.abstract | Objective: To assess analgesia of intra-articularly administered opioid morphine and to assess specific pain behavioural parameters in horses with experimentally induced acute synovitis.
Study design: double blinded cross-over clinical study
Animals: eight warm blood horses (mares)
Procedure: Lameness was induced in each horse via injection of lipopolysaccharide (LPS) into the tarsocrural joint. One hour after LPS injection the horses were treated with an intra-articular injection of morphine (120 mg diluted with NaCl to a solution of 20 ml) or saline (20 ml) as control. The horses underwent three behavioural tests: human approach test, carrot test and palpation of the painful area test before (baseline) and at 4, 8 and 28 hours after LPS injection. At eight hours after LPS injection the horses underwent a fourth test named novel object test. Video recordings of the basic maintenance behaviour of the horses were made before (baseline) and at 5.15 or 6.5, 12 and 29.15 or 30.5 hours after LPS injection.Data are reported as mean ± SEM and were statistically analyzed using SPSS. Differences were considered significant at P < 0,05.
Results: The results of this study showed several significant differences between the morphine group and the control (placebo) group during the behavioural tests and during the behavioural observations in the box. The horses in the morphine group had significant lower average percentages of non-weight bearing on the injected limb with regards to the horses in the control group during the human approach test and the carrot test at 4 and 8 hours and the behavioural observations in the box at 5.0-6.5 and 12 hours after LPS injection. Palpation of the injected limb led to significant lower scores during treatment conditions at the lateral and medial palpation compared to the control group at 4 hours after LPS injection. During the behavioural observations in the box the morphine group had a significant higher average percentage of foraging activity and a lower average percentage lying down at 5.0-6.5 hours after LPS injection. There was a strong trend for the average percentage walk; the horses in the morphine group had higher average percentage walking with regards to the horses in the control group at 12 hours after LPS injection.
Conclusions and Clinical Relevance: Our results support the practice of intra-articular administration of morphine to reduce pain in horses with acute synovitis. We concluded that intra-articularly administered morphine is a potent analgesic medication for acute synovitis in horses.
Furthermore, this study established the value of some specific easy to assess objective behavioural parameters in determining equine acute limb pain in horses. We concluded that decreased foraging activity, increased percentage lying down, non-weight bearing on painful limb and reaction to palpation of the painful area are valuable specific pain behavioural parameters in horses with acute synovitis | |
