38 – Chronic Pain

Question 1

What behaviour changes do associate with chronic pain?

Answer 1

• Aggression/reactivity
• Attention seeking
• Sleep pattern changes
• Loss of normal behaviours
• Change in navigation in environment
• Depression
• Licking/chewing/biting painful areas
• Anxiety and fear
• *PRESENTS IN MANY WAYS, AND OFTEN MISSED!
  o Masked by STRESS

Question 2

What is chronic pain?

Answer 2

• Any pain lasting more than 3 months
• Slow onset
• Some acute pain stats can present chronically (ex. root tooth abscess)
• Avoidance behaviour masks pain ID
• Vet assessment is challenging
• Behaviour problems are a common sequela

Question 3

Pain and behaviour

Answer 3

• up to 82% of dog and cat behaviour cases have a PAIN component
• Ex. hip, stifle, dental, allergies

Question 4

Chronic pain prevalence in dogs and cats

Answer 4

• Dogs: 56% (NOT just an old age problem)
• Cats: ranges from 60% DJD, by 12 years old 90%

Question 5

Chronic pain and anxiety

Answer 5

• **chronic pain includes the MENTAL HEALTH of the animal
• Share behavioural responses due to sharing same neural pathways
  o Ask yourself why? Is there a pain component?
• Ex. allergies in people + dogs: chronic itch=chronic pain

Question 6

How should chronic pain be assessed?

Answer 6

• Physical exam: not great
• Clinic observation: not great
• Wound palpation
• **home videos and photos!
  o Sleep: dogs need 14-16 hrs (cats need more)
  o Poke animal on back if safe
• Share infographic with owner

Question 7

What are the 3 types of chronic pain?

Answer 7

1. Somatic inflammatory pain
2. Visceral
3. Neuropathic
   *can occur concurrently

Question 8

C-fibers and pain

Answer 8

• Think chronic
• Unmyelinated: travels slower
• Pain perception:
  o Dull, poorly localized, persistent

Question 9

A-delta fibers and pain

Answer 9

• Think acute
• Myelinated
• Pain perception:
  o Sharp, well localized

Question 10

Chronic inflammatory pain (somatic) (ex. OA, burns, trauma, surgery)

Answer 10

• A-delta : C ratio = 1:2
• Dermal, articular or musculoskeletal
• *easier to localize (but not always)
• Inflammatory mediators (persistent inflammatory pain can lead to other types of pain, ex. neuropathic pain)

Question 11

How do you treat somatic pain?

Answer 11

• NSAIDs: mostly dealing with an inflammatory process
  o Deal with PRIMARY problem
• NGF monoclonal antibody (Solensia/Librela): osteoarthritis component
• Platelet rich plasma therapy: more expensive
• Ancillary treatments
  o *need to think what we are going to do LONG TERM
  o Mitigate some ongoing trauma (ex. ramps)
• Nutraceuticals
• MULTIMODAL therapy chronically
• Allergy treatment

Question 12

Chronic visceral pain (ex. peritonitis, gastric ulceration, IBD, cancer)

Answer 12

• A-delta : C ratio = 1:10
• Visceral afferent fibers travel with PS nerves (Ex. vagus nerve)
  o Large overlapping receptor fields
  o *difficult to localize
• Gnawing, squeezing, cramping

Question 13

How do you treat chronic visceral pain?

Answer 13

• Treat the inciting cause
• Dietary change may help (low CHO, high protein and fat)
  o Lower fermentation that creates GAS
  o Especially with food allergies
• Omega-3 FAs
• Antispasmodic agents
• Opioid agonist-antagonists or partial agonists
• NSAIDs, TCAs, SSRIs

Question 14

Neuropathic pain (ex. cancer, chronic inflammatory diseases (OA), interstitial cystitis)

Answer 14

• Pain initiated or caused by primary lesion or dysfunction in peripheral or central NS
• Present in many conditions
• Difficult to diagnose in animals (go with ‘gut feeling’)
• Ex. phantom limb pain (shooting, burning, electric-like sensation, tingling, stabbing)
• *hyperalgesia and allodynia

Question 15

How do you treat neuropathic pain?

Answer 15

• Generally start with NSAID trial
  o Add analgesic adjuvants (TCAs, serotonin-NE reuptake inhibitors, anti-convulsant, tramadol)
• Opioids in some situations: partial effectiveness
• *multimodal approach more effective than single therapy

Question 16

What are some other medications to consider for neuropathic pain?

Answer 16

• Gabapentin/pregabalin
• Amantadine
• SNRI
• Galaprant (Grapiprant)
• Cartrophen
• Carprofen

Question 17

Placebo effect of treatment

Answer 17

• Clients want the treatment to work and please you
• “better care” effect: I have taken them to the vet and spent money=they will get better
• *CAREFUL
• Chronic pain ‘waxes and wains’
  o Distraction can ‘help’

Question 18

Quality of life

Answer 18

• Emotional response to pain can increase fear and anxiety, but also reduce capacity for pleasure
• used as a synonym for welfare
• *chronic pain and quality of life are LINKED
• Many scales available!

Question 19

Quality of life assessment

Answer 19

• Difficult
• Make ‘best guess’ (subjective)
• *focus on how the animal is doing from the animals point of view
• Multiple scales: choose one that works for you and owner
• *Recognize limitations
• Include scale to assess owner’s anxiety