Development and validation of the facial scale (FaceSed) to evaluate sedation in horses.
Authors: de Oliveira Alice Rodrigues, Gozalo-Marcilla Miguel, Ringer Simone Katja, Schauvliege Stijn, Fonseca Mariana Werneck, Esteves Trindade Pedro Henrique, Prospero Puoli Filho José Nicolau, Luna Stelio Pacca Loureiro
Journal: PloS one
Summary
# FaceSed: A validated facial scale for equine sedation assessment Whilst equine practitioners routinely observe facial characteristics to gauge sedation depth, the reliability and clinical utility of these observations had never been formally validated. Researchers administered varying doses of detomidine (alone or combined with methadone) and acepromazine to seven horses, photographing their faces at baseline, peak sedation, intermediate, and recovery stages, then had four independent evaluators score ear position, orbital opening, and upper and lower lip relaxation across randomised images taken one month apart. The FaceSed demonstrated strong intra-observer reliability (0.74–0.94) and moderate-to-good inter-observer agreement (0.57–0.87), with excellent criterion validity against both numerical rating scales (0.92) and head height measurements (−0.75), whilst high internal consistency (Cronbach's α = 0.83) confirmed the four items measure a unified construct. Orbital opening and upper lip relaxation proved most specific for detecting absence of sedation (specificity 0.79 and 0.82), though all components showed good sensitivity (0.82–0.97) for detecting when sedation was present. For equine professionals, FaceSed offers a practical, evidence-based framework for objectively assessing sedation depth during clinical procedures, though practitioners should note the scale's development used still photographs and docile animals, meaning responsiveness to facial movement and performance in challenging horses requires further investigation.
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Practical Takeaways
- •FaceSed provides a validated, practical tool for field assessment of sedation depth using observable facial features without requiring numerical scales or equipment
- •Orbital opening and upper lip relaxation are the most reliable indicators for distinguishing when sedation has worn off, useful for timing procedures or additional dosing
- •The scale shows good consistency between observers, meaning different team members can reliably use it to communicate sedation status during procedures
Key Findings
- •FaceSed intraclass correlation coefficient for intra-observer reliability ranged 0.74-0.94 (good to very good) and inter-observer reliability 0.57-0.87 (moderate to very good)
- •Criterion validity showed strong correlation between FaceSed and numerical rating scale (Spearman correlation 0.92) and moderate negative correlation with head height above ground (-0.75)
- •Orbital opening and upper lip relaxation demonstrated highest specificity (0.79-0.82) for detecting absence of sedation, while all items showed high sensitivity (0.82-0.97) for detecting sedation
- •High internal consistency (Cronbach's α = 0.83) confirmed good intercorrelation among FaceSed items (ear position, orbital opening, lip relaxation)