No pain, more gain? Evaluating pain alleviation post equine orthopedic surgery using subjective and objective measurements

Abstract: As “you can’t manage what you can’t measure,” there has been a quest to identify the best measures of pain to effectively and timely manage equine pain. Adequate pain management after a surgical procedure is imperative to address postoperative pain that negatively affects numerous organs. Arthroscopy is a frequently used surgical procedure: making an evaluation of equine post-arthroscopic pain cardinal. Furthermore, an evaluation of such pain using subjective pain scoring and objective four beat gait analysis scoring had yet to be explored. The objectives of this case study series were to: study a potential varying degree of pain after equine arthroscopy in relation to varying intra-articular tissue damage; survey the pain relief of systemic NSAID analgesics post equine arthroscopy; and to observe a possible difference in equine pain behavior in human presence vs. absence. This observational unmatched paired cross-sectional qualitative case study series included six horses. The study used three subjective modalities and one objective modality to score pain: a composite Equine Pain Scale (EPS) score based on blinded-rated video footage; an Arthro and a VAS score as proxies for tissue damage; and an objective optical symmetry measurement (OS) score to evaluate low-grade lameness at walk. These modalities were used to compare potential pain states 12 hours before and 8-48 hours after surgery before and after NSAID administration. During the two months collection period, 277 individual video segments were recorded and 40 OS-readings were collected and analyzed. The results are illustrated in descriptive graphics. The contradictory Arthro/VAS score findings illustrate the complexity of pathology and subsequent pain expression as well as the difficulty of designing a general tool to foresee individual future pain scenarios. However, both the subjective EPS and the objective OS scores seem to illustrate a common undulating pattern that could be a mirroring of an increased pain state before NSAID-administration and a decreased pain state post NSAID-administration, with the one caveat that there were two differing OS parameters of interest. This study also raised questions in relation to a differing efficacy of the analgesic and the duration of a postsurgery pain state. These findings could point to a potential clinical need for an alternate multi-modal medical approach and/or prolonged medication duration/increased intervals as needed for certain cases. Finally, in regard to hidden pain behaviors, there were examples of an equine increase in gross pain behavior, restless activity, and horses positioning themselves towards the back of the stall when there were no humans present. Overall, this case study series seems to suggest the usefulness of a simple and cheap subjective pain score measuring system such as the EPS as it is possibly reflected by a high-tech complex objective optical symmetry measurement system. The results of the latter are among the first reported for the use of this new algorithm of fall 2015. As there is no golden standard for uncovering the true equine pain state, there might be added power in attempting to describe pain states using differing but complimentary pain modalities. Nevertheless, any suggested findings of this highly limited case study series should primarily be regarded as potential seeds for future hypotheses generation for future large targeted quantifying studies to validate or refute this study’s suggested findings and possible clinical relevance. No pain, more gain?