Certificate in Client Care ServicesWRITTEN BY: Nicola WILKINSON
PGCertVetAnA, BSc (CVN), DipAVN (Small Animal), DipHECVN, RVN, TAA.
First Published: 19th March 2025
Pain management is at the heart of patient welfare. As veterinary nurses, we have an ethical responsibility to recognise and report pain, ensuring our patients receive the care they need.
Beyond the obvious welfare concerns, unaddressed pain can increase fear, anxiety, and stress; delay wound healing; impair respiration; and prolong hospitalisation.
But pain assessment isn’t always straightforward. Personal bias and subjective observations can make it difficult to measure pain accurately. That’s why standardised pain assessment tools are essential.
What is Pain?
Pain is described as an unpleasant physical and emotional response to trauma or potential trauma (Self, 2013). It can be:
- Acute – Short-term, usually caused by injury, surgery, or illness.
- Chronic – Long-term, persisting beyond normal healing time (e.g., osteoarthritis).
Unlike humans, our patients cannot easily communicate the character of their pain (location, intensity, sensations) and signs can vary significantly between species. This makes pain assessment complex, requiring keen observation of both behavioural and physiological indicators.
Recognising Pain: Behavioural & Physiological Signs
Signs of pain can be evaluated in two ways, behaviourally and physiologically.
Behavioural signs are often the most accurate indicators. However, pain presentation varies by species:
- Dogs: Panting, reluctance to move, excessive licking, whining, or aggression.
- Cats: Withdrawn behaviour, lack of grooming, aggression, or reluctance to jump.
- Prey species (rabbits, rodents): Subtle signs like reduced movement, hiding, or changes in feeding habits.
Some animals mask pain due to survival instincts (e.g., prey species, cats). Others may react differently based on personality, age, or past experiences.
Physiological signs of pain can support behavioural observations but may be affected by stress, drugs, or other medical conditions
- Increased heart rate (tachycardia)
- Increased respiratory rate or effort
- Dilated pupils (cats)
- Hypertension.
As nurses, we must also differentiate between a patient displaying signs of pain and that of a dysphoric episode. Patients that are crying or howling in hospital could be mistaken for being painful and vice versa, a patient’s pain level may be ignored due to the thought that they are unhappy with their environment or having a reaction to an anaesthetic or analgesic drug.
THE IMPORTANCE OF MEASURING PAIN
We can reasonably assume pain exists in contexts that we expect to be painful (inflammation, trauma, noxious stimuli) and can treat it with the use of analgesics such as non-steroidal anti-inflammatory drugs, opioids, local anaesthetics and other drugs. However, the use of these drugs is accompanied by side effects that may be detrimental to the patients’ health, therefore it is important to ascertain that analgesia is warranted and used appropriately.
So, the question is, how do we measure pain?
PAIN ASSESSMENT
Pain is measured through regular pain assessment. The frequency and type will depend on individual hospital protocols and the types of analgesia in use. Most hospitals assess post operative patients every four hours, as this is the effective duration of many common analgesics, especially opioids.
Non-surgical patients can be charted for pain assessment to be carried out four times per day (every 6 hours) in conjunction with their regular TPRs. Alternatively, the attending veterinarian may chart assessment more frequently at their discretion and the patient’s clinical context.
As nurses, we should be constantly aware of any patients that exhibit signs of pain and report such findings to the attending veterinarian. It should be noted that although all animals experience pain, expression of pain varies with age and species, as well as among individuals.
HOW DO I BEGIN A PAIN ASSESSMENT?
Establish a Baseline
Just like a pre-op TPR assessment, a baseline pain assessment is essential for comparison. You cannot identify your abnormal data if you don’t know what normal looks like!
- First: Observe the patient from a distance – Note posture, respiratory pattern, rate, depth, facial expression, ear position and overall demeanour.
- Assess while at rest – Do not wake a sleeping patient unnecessarily.
- Second – Perform a hands-on exam – Physical exam should not cause stress! Gently auscultate heart rate and pulses. If tolerated, gently palpate to check for reactions. Start with non-painful areas first.
- Consider the presence of the owner – Some animals show anxiety behaviours which can impact the assessment. Those with separation anxiety may be better assessed with the owner present.
The hands-on exam should include gentle handling and palpation. The painful area to be assessed should be left until last once other areas have been assessed. Heart rate should be taken before any potentially distressing procedures and blood pressure should not be attempted until the patient has settled (place the cuff ready in advance, then allow to settle). Physiological changes by stimulation of the sympathetic nervous system can be influenced by other factors, such as surgery complications or a clinical condition such as hypertension. Pain assessment by tactile manipulation or palpation of affected areas may be the only way to determine if pain is present and most animals will show obvious signs of pain or discomfort when this is performed. Temperature taking should be done last (if this is required) to avoid false elevations of heart rate, blood pressure and signs of stress which could indicate pain.
PAIN SCALES
Pain scales reduce bias through standardised assessment. Their ‘rules’ of assessment reduce or eliminate variables (bias, subjectivity) that can occur when different staff assess patients.
Some clinics will design their own pain scales, however if they are too complicated and take too long, they may be rushed through rather than properly followed, there is also the risk that these self-developed scales do not give consistent, reliable assessments of pain!
When choosing a scale, it is important to take this into consideration and ensure that all team members are trained in its interpretation and use. There are now several quick and easy-to-use adaptations available. There are many, researched and validated pain score systems for a variety of species that we can quickly use in clinic. Validated means it has been proven to provide consistent results in a range of contexts and applications. They give a reliably accurate and consistent pain score across different users and animals. Where possible, we should use validated systems in clinic; however, non-validated tools are very useful and should not be discounted from use just because they don’t have the validated tick of approval. They are often quick and easy to apply.
An ideal pain scale is:
✔ Simple – Easy to apply in a busy clinic.
✔ Reliable – Provides consistent results across users.
✔ Validated – Proven to accurately assess pain.
CURRENT PAIN SCORING SYSTEMS
Canine
VALIDATED:
- Glasgow Composite Measures Pain Scale (CMPS – Canine), University of Glasgow
NON VALIDATED:
- CSU Acute Pain Scoring, Colorado State University
- 4A-VET Post Operative Pain Scale, French Association for Animal Anaesthesia and Analgesia & University of Montreal
Feline
VALIDATED:
- Glasgow Composite Measures Pain Scale for Cats (CMPS – Feline), University of Glasgow
- UNESP-Botucatu Multidimensional Composite Pain Scale for assessing postoperative pain in cats, UNESP-Botucatu
- Feline Grimace Scale, University of Montreal
NON VALIDATED:
- CSU Acute Pain Scoring, Colorado State University
- 4A-VET Post Operative Pain Scale, French Association for Animal Anaesthesia and Analgesia & University of Montreal
Equine
VALIDATED:
- Horse Grimace Scale, University of Milan, & Newcastle University
- Ridden Horse Pain Ethogram, Sue Dyson
NON VALIDATED:
- Equine Comfort Assessment, Colorado State University
Lupine (Rabbit) & Rodents
VALIDATED:
- Rabbit Grimace Scale, Newcastle University
- Rat Grimace Scale, NC3Rs
- Mouse Grimace Scale, NC3Rs
- Ferret Grimace Scale, Animal Research Centre
LET’S TAKE A CLOSER LOOK….
CSU PAIN SCALES FOR DOGS & CATS
The Colorado State University (CSU) Pain Scale is a widely used system for assessing pain in cats and dogs.
- Uses 0-4 scoring with ¼ marks and color-coded visual aids.
- Incorporates body tension, posture, and reaction to palpation.
- Not yet validated, so inter-user variability exists.
Key Features
- Assesses psychological, behavioural, and physical signs of pain.
- Uses body tension as a key evaluation tool, which is unique among pain scales.
- Includes guidance for assessing resting patients, recognising the importance of delaying evaluation in sleeping animals.
- Provides species-specific scales for dogs and cats with clear behavioural descriptors, reducing observer variability.
📌 Limitations
- Not yet validated through clinical studies.
- Lacks specific instructions for completing the pain score, which may lead to inconsistent use.
- The 0-4 scale may be too narrow for precise differentiation in practice.
- Primarily designed for acute pain assessment
NOTE: The Feline CSU Acute Pain Scale has been preliminarily assessed for reliability but does not yet meet full validation standards (Shipley et al., 2019). Despite moderate to good inter-rater reliability, further studies are required to confirm its effectiveness compared to other feline pain scales. Nonetheless, it remains a valuable clinical tool in veterinary practice.
Grimace Scales (Feline, Equine, Rabbit, etc)
Grimace scales exist for cats, ferrets, horses, piglets, rabbits and sheep.
- Assess facial expressions associated with pain (e.g., whisker position, ear orientation, eye tightness).
- Validated for multiple species, making it a reliable tool.
Feline Grimace Scale (FGS)
Developed by The University of Montreal in Canada this is probably the most useful tool for assessing pain in cats. Their website has excellent resources, instruction manuals and guided applications where you can test your use of the tool!
GLASGOW COMPOSITE MEASURE PAIN SCALES (CMPS)
These tools assess several behavioural parameters of pain in dogs and cats. Each species has its own short form for rapid use in clinic. Canine Glasgow short form composite measure pain score is a validated CMI for dogs that has been adapted for convenient use in practice. It is a validated system that assesses the patient for vocalisation, attention to the wound or painful area, response to palpation, posture and movement, and the overall patient demeanour.
- Validated tool for both dogs and cats.
- Uses a numerical score out of 24 (dogs) or 20 (cats).
- Includes vocalisation, posture, wound attention, and response to palpation and overall demeanour
📌 Limitations
- Does not consider physiological parameters like heart rate or blood pressure.
- Requires direct interaction, which may cause stress responses misinterpreted as pain
DOGS
Key Features
- Validated for dogs (short-form version) and adapted for practical use.
- Assesses vocalisation, attention to wounds, response to palpation, posture, movement, and overall demeanour.
- Uses a behavioural response scale, reducing observer bias and improving accuracy.
- Includes specified behaviours rather than leaving them open to interpretation.
- Numeric scale allows for evaluation and comparison over time.
- Contains 30 assessment points across 6 questions, leading to a numerical score out of 6/24 or 5/20 if non ambulatory.
CATS
Key Features
- Designed for cats experiencing acute pain.
- Uses psychometric techniques with facial expressions and animated reference images.
- Assesses vocalisation, behaviour, posture, physical responses, wound palpation, and overall demeanour.
- Contains 22 assessment points across 6 questions, leading to a numerical score out of 20.
- Treatment is recommended for scores over 5, making it a straightforward tool for clinical use.
UNESP-Botucatu Multidimensional Pain Scale (Cats)
Validated for post operative pain in cats, this system might be a perfect option for clinics that do a lot of elective surgery, or feline only services. The easy-to-follow tool has specific clear descriptions of each assessment area but lacks images to support interpretations.
- Specifically for post-op feline pain assessment.
- Focuses on behavioural changes, facial expressions, and body posture.
Final Thoughts
As veterinary nurses, we are advocates for our patients. Accurate pain assessment allows for better treatment, improved patient comfort, and enhanced welfare.
Take Action!
✔ Familiarise yourself with different pain scales.
✔ Ensure consistency in your clinic’s pain assessment approach.
✔ Advocate for using validated tools where possible.
🐾 What pain scale does your clinic use? If you want to update your approach, download the scales above and enrol into the ACVN Pain Management Short Course today!
want to learn more?
Pain management
SHORT COURSE
Analgesia knowledge and the ability to recognise pain is vital in so many aspects of veterinary nursing. This subject will teach students about the nervous system, pain pathways, and the drugs we use to control pain. It will look at recognising pain and pain scoring, as well as alternative methods of controlling pain in our patients including nursing interventions we can provide.
Check it out