Analgesic efficacy of intra-articular morphine in experimentally induced radiocarpal synovitis in horses

Casper Lindegaard, Maj Halling Thomsen, Stig Larsen, Pia Haubro Andersen

    63 Citations (Scopus)

    Abstract

    Objective: To compare the analgesic effect of intra-articular (IA) and intravenous (IV) morphine in horses with experimentally induced synovitis. Animals: Eight adult horses. Study design: Randomized, observer blinded, double dummy trial with sequential crossover design. Methods: Radiocarpal synovitis was induced by IA injection of lipopolysaccharide on two occasions separated by a 3-week washout period. In one study period horses received treatment IA; morphine IA (0.05 mg kg-1) plus saline IV and in the other study period they received treatment IV; saline IA plus morphine IV (0.05 mg kg-1). Lameness and pain were evaluated repeatedly by two observers throughout each of the two 168-hour study periods. Pain was evaluated by use of a visual analogue scale of pain intensity (VAS) and a composite measure pain scale (CMPS). Comparison of treatments was performed by analysis of variance with repeated measurements. Significance level was set to p ≤ 0.05. Inter-observer agreement and agreement between the VAS and CMPS was assessed by use of the Bland-Altman method. Results: Intra-articular injection of LPS elicited a marked synovitis resulting in lameness and pain. IA morphine resulted in significantly less lameness than IV morphine (p = 0.03). CMPS (p = 0.09) and VAS (p = 0.10) pain scores did not differ significantly between treatments. Inter-observer agreement of the CMPS was classified as good, but only fair for the VAS. Agreement between the two pain scales was considered fair. Conclusions and clinical relevance: An analgesic effect of IA morphine was demonstrated by significantly reduced lameness scores. The results support the common practice of including IA morphine in a multimodal analgesic protocol after arthroscopic surgery, although further studies in clinical cases are needed. The employed CMPS had good reproducibility, and was easy to use, but may have limited sensitivity at mild intensity pain.

    Original languageEnglish
    JournalVeterinary Anaesthesia and Analgesia
    Volume37
    Issue number2
    Pages (from-to)171-185
    Number of pages15
    ISSN1467-2987
    DOIs
    Publication statusPublished - Mar 2010

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