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Conference abstract2016

Optimizing thermal testing system in the horse

Olsén, Lena; Ingvast Larsson, Carina

Abstract

Background: Accurate, repeatable and reliable pain recognition and quantification of analgesia are essential for development of effective analgesic protocols and necessary for adequate pain management. Thermal threshold testing techniques have valuable roles in both the identification of altered nociceptive function and the pre-clinical evaluation of analgesics in horses. When using test systems, definition of a clear cut end-point of stimulation, such as skin twitching, shaking or hoof withdrawal is crucial for reliable and repeatable determination of the nociceptive threshold. End-point behaviour might be reflex related or may represent conscious perception of pain but could also be influenced by the environment and the horse's willingness to show pain. Objectives: The overall aim was to optimise the reliability and repeatability of the testing procedures in a future study assessing analgesic treatment protocols. The optimal settings of the testing system was evaluated. Furthermore, the type of end-point behavior showed by different horses was investigated. Materials and methods: Fifteen Standardbred horses were evaluated using a thermal threshold testing system adopted for use in horses (Topcat Metrology). All horses were tested by heating with a thermal probe on skin at the withers until an end-point behaviour (threshold temperature) or a cut-out temperature (58 °C) was reached. The type of end-point behaviour, the willingness to wear the testing system and to show pain related behaviour was evaluated. Also the skin temperature before heating, the rate of heating (0.5 vs 1.0 °C/s) and repeatability was examined. The study was blinded with cross-over design. Results: No differences in mean threshold temperature (49.5 and 50.7 °C, respectively) between the rates of heating of 0.5 vs 1.0 °C/s, nor in delta temperature (14.0 and 14.4 °C, respectively). There were individual differences in type of behaviour and easiness to observe their end-point behaviour and some horses did not produce an identifiable end-point behaviour before cut-out temperature. We identified and selected horses showing easy recognized skin twitch as end-point behavior to be included in our future study of analgesic treatments. Conclusions: Thermal threshold testing appears not to be an appropriate test technique in all individual horses. As higher cut-out temperatures could possibly damage the skin it is not appropriate to include more "stoic" horses. This implies that if pain is more easily identified in extrovert individuals the relationships between pain behavior and personality in horses should be clarified for better study design in pain management. Acknowledgements: Supported by The Swedish-Norwegian Foundation for Equine Research.

Published in

Acta Veterinaria Scandinavica
2016, Volume: 58, number: Suppl2

Conference

9th international symposium on veterinary rehabilitation and physical therapy, 2016-08-08--2016-08-12, Uppsala, Sweden