As horse owners and veterinarians, we have a responsibility to recognize when our horses and patients are in pain. Pain recognition is important for equine welfare, quality of life, accurate diagnosis and treatment of health conditions, monitoring a horse’s condition, horse and human safety, and equine performance.
“By prioritizing pain assessment, we not only fulfill our ethical obligation, but we also enhance the quality of life of horses and align with societal expectations,” said Emanuela Dalla Costa, DVM, PhD, DECAWBM (AWSEL), associate professor at the University of Milan, Italy. “It’s really important that we try as veterinarians to improve pain assessment not only in the clinics but also in the stables.”
Dalla Costa described the pain assessment tools available to equine veterinarians during Part 1 of VetPD’s 10-part series on Equine Pain Recognition, Assessment, and Management. The first-of-its-kind, interactive lecture series brings together 15 world-renowned specialists via livestreamed (and on-demand) weekly modules. Here are some of the takeaways from the first module, which Dalla Costa co-hosted with Alonso Guedes, DVM, MS, PhD, DACVAA.
Assessing Equine Pain Is Challenging
There is no gold standard for assessing a horse’s pain levels. We don’t have a thermometer or tool we can use to definitively tell us a horse is experiencing pain or to measure the intensity of that pain.
“This lack of standardization complicates the process of establishing and adjusting analgesic therapy, … evaluating the effectiveness of pain management, and monitoring the patient over time,” said Dalla Costa.
A valid, reliable, and practical pain scale would be valuable not only in clinical practice but also for horse owners and stable managers, so they can recognize when a horse starts to feel pain, she said. An effective pain assessment tool should be quick and easy to learn and have clear scores that are easy to interpret. Dalla Costa described six pain assessment scales veterinarians can choose from, depending on the situation and/or the patient’s pain condition.
Visual Analog Scale (VAS)
The visual analog scale is simply a horizontal line about 10 centimeters long. The left end indicates no pain, and the right is the worst pain imaginable. The veterinarian places a dot where he or she believes the horse’s pain level to be and measures the number of millimeters from the left end of the line to the dot.
“The visual analog scale is a continuous variable, and it can be easy to use,” said Dalla Costa. “I observe the horse for a while, and then I just judge the level of pain that horse is experiencing.”
Downsides include intra- and interobserver variability and interpretation, she noted.
Numeric Rating Scale (NRS)
The NRS is also a horizontal line but with numbers from zero (no pain) to 10 (the worst possible pain). The observer circles the number he or she thinks represents the horse’s level of pain. Because the variable is a discrete number, said Dalla Costa, it’s generally easier to have reliability between different observers than with the VAS. On the other hand, “it’s less sensitive to changes in the pain condition because we apply just a number, and the numbers aren’t always linked to the same difference in pain level perceived by the vet.” Thus, she said, the NRS is less sensitive than the VAS in detecting small changes in pain.
Simple Descriptive Scale
The simple descriptive scale comprises predefined categories that are linked to degrees of pain. Each one is assigned to a number, and these numbers can be used to calculate an overall score. Dalla Costa said this scale is easy to use, especially if you add classes or descriptions to each number. Disadvantages include reliability, especially with less experienced assessors.
This tool has proven useful for identifying lameness in horses, with common examples including the AAEP Lameness Scale and the OBEL Grading System.
Time/Activity Budget Analysis
Time budget represents the percentage of time a horse spent on a specific activity (e.g., eating, drinking, lying down, weight-shifting, etc.) over a 24-hour period. “Animal pain leads to changes in behavior, so we see changes in the normal activity patterns,” Dalla Costa explained. “This can be really useful, in my opinion, for monitoring chronic pain.”
The main downside is it requires a long observation period—at least 24 hours. “We can use video recordings, but then I need to watch the recording,” she said. “If I need to have an assessment straight away, for example in a clinic, it’s not possible to analyze 24 hours in one or two minutes.”
Continuous video monitoring is useful in a clinic setting, she added, because it removes the human from the equation and, thus, the chance of a human’s presence affecting the horse’s behavior.
In the future, said Dalla Costa, smart cameras or artificial intelligence might help veterinarians monitor time budget more easily. Don’t forget the technology costs associated with this method, she said.
Composite Pain Scale (CPS)
The composite pain scale is a multidimensional tool that measures both behavioral and physiological responses, allowing the veterinarian to score each variable individually.
“Pain is complex and evokes emotional, behavioral, and physiological responses,” Dalla Costa explained. “So, if we measure all these responses together, we are better able to identify and quantify pain, because we are measuring different things at the same time.”
The end result is a number or “score” that can be linked to the intensity of pain the horse is experiencing. Dalla Costa said it’s helpful for monitoring a horse’s pain daily and over time. Disadvantages include the training and experience needed to use the scale and the amount of time the assessment takes. “If I have 20 items (to assess), I can’t observe the horse for one minute and pick up everything,” she said. “Another possible disadvantage is that we have multiple composite pain scales that are pain-condition-specific (e.g., colic, orthopedic pain, post-castration pain).”
Facial Expression/Grimace Scale
The facial expression or grimace scale was developed to assess alterations in horses’ facial expressions. The veterinarian gives each feature (ears, eyes, chewing muscles, nose, and mouth) a score, which typically correlates with a description. “At the end, we have an overall score that can be added to other composite pain scales,” said Dalla Costa, adding that this method is easy to use and sensitive to mild pain conditions. The main disadvantages include the required training and reliability, “especially for some facial features that can be more difficult for inexperienced assessors.”
The scale is used for painful conditions such as castration, acute laminitis, dental pain, colic, head-related pain, orthopedic, and ophthalmic pain.
Take-Home Message
When choosing a pain assessment tool for your patient, it should be easy to apply, scores should be easily understood by different observers, and it shouldn’t require difficult calculations or specific instruments for collecting data, said Dalla Costa.
Set up criteria with clear descriptions or pictures or videos that make it easier for new assessors to learn. Also consider the time needed to perform the assessment. “If you have two different pain scales that are valid, and one needs half an hour and one needs five minutes, of course you will choose the shorter one,” she said.
If you need to assess the horse’s behavior, do that first. “For example, if you have a pain scale that has both behavioral items and physiological items, you need to assess behavior first, and then you can measure the heart rate variability or the respiration rate or whatever you need.”
She concluded by acknowledging we still have work to do when it comes to recognizing equine pain, but having a standardized approach to pain assessment is crucial for horse welfare.
View a short clip from the lecture here.
You can sign up to watch this module and the series in its entirety on VetPD.com.
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