07.Jun 2022

Anesthesia: Pain in small and companion animals


Assessing the patient's pain level is often challenging for veterinarians.
In dogs, there are enormous individual and breed-dependent differences in pain (Chihuahua vs. Staffordshire Terrier or small dog vs. large dog).

Cats often express pain and discomfort through aggressive behavior or increased withdrawal in addition to changes in movement patterns.

Basically, deviations from normal behavior can be signs of pain in all animal species!

So, if the owner reports missing (e.g. lack of jumping or grooming) or new (negative) behavior patterns, pain should be considered as a possible cause.

If possible, the pet owner should be part of the assessment, as he or she observes - optimally - his or her pet very closely and can see changes that cannot be detected in the clinical examination → anamnesis!

However, it must be remembered that chronic pain usually creeps in slowly (pain memory!) and behavioral changes do not occur suddenly but over time and are thus often blamed on "old age", for example. In the sense of these patients a pain clarification and if necessary the therapeutic diagnostics with analgesics should always take place.

Assessment of pain

In addition to determining the type of pain (visceral, somatic or neuropathic), the selection and dosage of an effective pain therapy also requires the most adequate possible assessment of pain intensity. Scientifically accepted scales have been evaluated for this purpose:


  • Feline Glasgow Composite Measure Pain Scale
  • Feline Grimace Scale - for acute pain - the cat's "pain face": www.felinegrimacescale.com. Also suitable for the pet owner.

These two are the most commonly used scales for pain assessment in the cat.

As a supplement in addition to the clinical examination, for example in hospitalized patients (trauma, internal medicine...), postoperatively or as a therapy control, these can be used in a supportive way.

Further scales:

  • Feline Acute Pain Scale of the University of Colorado (CSU-FAPS), USA.
  • "Feline Musculoskeletal Pain Index (FMPI)" from the University of North Carolina, USA - for use by the patient owner in chronic joint disease.


  • Glasgow Composite Measure Pain Scale: for assessing acute pain, for example postoperatively (after the effects of general anesthesia have ended). The use of analgesics is recommended starting with a pain score of 5/20 (mobility cannot be assessed) or 6/24 (mobility can be assessed), or even with a lower score if the dog appears clinically painful!

Important for assessing the effect of an analgesic: consider duration of onset of action! This calculation is particularly important for meaningful pain coverage both pre-, intra- and postoperatively.

Other scales:

  • Canine Acute Pain Scale from the University of Colorado, USA.
  • Helsinki chronic pain index: For the assessment of chronic pain, especially in osteoarthritis.
  • Canine Brief Pain Inventory (CBPI): Rating system for the patient owner to assess chronic pain in osteoarthritis and is used to monitor the success of therapy (download: www.vet.upenn.edu/research/clinical-trials-vcic/our-services/pennchart/cbpi-tool).


Grimace Scales have also been developed for mice, rats and rabbits, whose general condition must often be assessed in animal studies. These are available for free download at the following link, among others: nc3rs.org.uk/3rs-resources/grimace-scales.

The ITIS (Initiative tiermedizinische Schmerztherapie - Veterinary Pain Management Initiative) also provides further assistance in classifying the degree of severity. In addition to criteria for dogs and cats, recommendations for the assessment of pain in pets, birds, reptiles and amphibians can also be found there!

Cardiopulmonary, neuroendocrine or other laboratory values are not suitable for the assessment of pain according to current knowledge, because there are too many influencing factors and there is no long-term value, which is actually meaningful.


Bibliography: Upon request

Author of the article:

Veterinarian med. vet. Julia Brüner