Application of a Composite Pain Scale to Objectively Monitor Horses with Somatic and Visceral Pain under Hospital Conditions

Pain recognition and management in animals has advanced considerably in the last decade and currently animal welfare is receiving increasing public interest. However, the comprehensive assessment of pain has been inadequately addressed in horses and till recently composite pain scales (CPSs) have hardly been validated for use in patients. We investigated the reliability and clinical applicability of a CPS, originally developed under experimental conditions for assessing pain in horses with various acute soft-tissue and orthopedic conditions before and after general anesthesia and/or (non)elective surgery. These clinical cases (n = 94) were scored by means of the CPS twice daily. Horses without painful conditions and horses admitted for nonpainful diagnostic procedures under general anesthesia were compared with those that were admitted with either acute or chronic surgical and nonsurgical painful conditions of both visceral and somatic origin. Scores of observer 1 were compared with observer 2 to study inter-observer reliability. Composite pain scores showed low baseline values in healthy animals with nonpainful conditions and were not affected when general anesthesia was the only intervention. Inter-observer reliability was very high (n = 23 horses; weighted kappa correlation coefficient, κ = 0.81). Horses with painful conditions responding well to analgesic treatment could be discriminated from horses that had to be euthanized on humane grounds because of painful nonresponsive conditions. We found the CPS to be a promising tool that has the potential to provide a good basis for direct day-to-day assessment of pain status in equine patients with various painful conditions in the future.