Pain Flashcards
What is pain?
An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage
What are the 3 dimensions of pain?
Sensory - discriminative (location, intensity, quality, duration)
Motivational - affective (how the pain makes you feel)
Cognitive - evaluative (influences behaviour)
What are the risks of uncontrolled post-op pain?
Discomfort
Suffering
Delayed healing
Increased morbidity
Risk of developing chronic persistent pain
What are the adverse effects of unrelieved pain?
Neuroendocrine e.g., hypoglycaemia, weight loss, slower wound healing
Cardiovascular - fatigue
Respiratory - decreased lung volume
GIT + urinary - decreased bowel motility => constipation, urinary retention
MSK - decreased muscle function
Psychological - poor sleep, PTSD
Give examples of pain assessment tools
Physiological measurements/exam
SDS (simple descriptive scale)
NRS (numeric rating scale)
VAS (visual analogue score)
DIVAS (Dynamic, interactive visual analogue scale)
Composite scales
Pain faces
Acute vs chronic pain scales
Quality of life (QoL) scales
Analgesiometry & accelerometers
Gait analysis
Pressure sensitive walkways, platforms
What are the disadvantages of SDS, NRS and VAS pain scoring?
Only consider intensity of pain - not sensory or affective qualities of pain
What are the challenges of pain scoring?
Difficult, subjective, other drugs can affect the evaluation
Environment/owner/caregiver can affect the animal
Species variation
Interspecies variation
Domestication, hierarchy, feeding, aggression
What is the most commonly used acute pain scale?
Glasgow Composite Measure Pain Scale (CMPS-SF)
Describe the process of the Glasgow Composite Measure Pain Scale (CMPS-SF)
Evaluate the dog once it has recovered sufficiently from anaesthesia (as scores can be affected by the hangover effect of sedative and anaesthetic drugs)
If pain scores are greater than 5/20 or 6/24, consider giving analgesia
Allow the analgesic to take effect and reassess after an hour; if the score has decreased to below the intervention level, reassess in 2 hours. If not consider additional analgesia
Then assess every 3-4 hours or earlier as appropriate (depending on the severity of the surgical procedure and the class/route of administration/expected duration of analgesic administered) and after each analgesic administration
The scale is intended to be an adjunct to clinical judgment, and no animal should be denied analgesia on the basis of the scores alone
Describe the use of the Glasgow Feline Composite Measure Pain Scale (CMPS-Feline)
clinical decision making tool for use in cats in acute pain
the recommended analgesic intervention level is 5/20.
What are features of grimace/pain faces?
- Ear Changes : fold, curl and angle forwards or outwards, pointed shape
- Orbital Tightening: narrowing of the orbital area,partial or complete eye closure orsqueezing
- Nose/Cheek Flattening: with eventual absence of thecrease between the cheek and whisker pads
- Whisker Change:move forward away from face
- Head position
What factors can be used to assess cattle pain evaluation?
Tense stare/withdrawn
Tension of muscles above eyes
‘lines’ above nostrils
Strained nostrils
Increased tone of lips
Tension of facial muscles
Tense ears pointed backwards
What signs of pain can be seen in pigs
Wrinkling of snout
Ears held backwards
How can ear position be used to assess pain?
How can orbital tightening be used to assess pain?
How can muzzle tension be used to assess pain?
How can whisker change be used to assessed pain?
How can head position be used to assess pain?
Describe facial features of equine pain
Distance between ears becomes larger
Muscles around eyes are stretched - sclera becomes more evident in medial canthus
Withdrawn stare
Dilated nostrils (side-to-side)
Tense facial muscles
Increased tonus of lips and tension of chin
Give examples of ways to treat acute pain
Opioids, NSAIDs, local anaesthetics
Ketamine and alpha 2 agonists
Cold therapy
Good tissue handling
Nursing care (bandages, massage, IV lines, monitoring, ROM, ensuring sleep)
Other therapies (limited evidence) e.g. Laser, TRPV1 agonists, pulsed EMF
How does the inflammatory pathway work?
After a cell is damaged, an enzyme called cyclooxygenase (COX) is activated. COX then stimulates the cell to produce substances called prostaglandins, which contribute to signs of inflammation such as pain, redness, warmth, swelling, and fever.
What are the most commonly used small animal NSAIDs?
Meloxicam, Carprofen, Robenacoxib, Firocoxib
When are NSAIDs contraindicated?
In patients with:
Renal or hepatic insufficiency
Hypovolaemia
Congestive heart failure & pulmonary disease
Coagulopathies, active haemorrhage
Spinal injuries
Gastric ulceration
Concurrent use of steroids
Shock, trauma
Pregnancy
What are the most common equine NSAIDs?
Phenylbutazone (suxibuzone), Flunixin meglumine, Meloxicam
What are the most common cattle NSAIDs
Meloxicam, Ketoprofen
Describe the mode of action of grapiprant
Galliprant is an NSAID that does not block COX. It works lower down the inflammatory pathway by blocking some activity of a specific prostaglandin (EP4 receptor)
What is the benefit of grapiprant over other NSAIDs?
targets canine pain and inflammation while reducing the impact on GI, kidney and liver homeostasis
Describe the licensing of paracetemol
Used IV in dogs & horses (no licence)
Pardale-V (paracetamol & codeine) has licence in dogs
Licensed in pigs
NEVER USE IN CATS
Give examples of opioids
Morphine
methadone
pethidine
fentanyl
buprenorphine
butorphanol
tramadol
What opioid receptor gives an analgesic response
Mu receptor
What are the effects of activation of mu opioid receptors?
What is the effect of activation of K opioid receptors
What is the effect of activation of beta opioid receptors?
Why should you always draw back when giving local anaesthetics?
To ensure you are not injecting into the blood supply
What is the risk of local anaesthetics?
Narrow therapeutic index (easy to overdose)
Where is the target of local anaesthetics?
located within the pore of the Na+ channel close to the cytoplasm and only the ionized, charged form of the local anaesthetic can interact with this receptor.
What are the effects of alpha 2 agonists (a and b receptors)?
Sedation (a)
Decrease MAC
Analgesia (somatic & visceral) (a & b)
Hyper (b) then hypotension (a)
Decreased CO & HR, increased SVR
Respiratory depression
Increased urine production
Decreased GI motility
Decreased surgical stress response
Hyperglycaemia, GH enhanced,
Thermoregulation affected
Sweating
how can alpha 2 agonists be antagonised?
atipamezole
What receptors do alpha 2 agonists act on?
a adrenergic receptors (presynaptic)
b adrenergic receptors (post-synaptic)
What are the uses of ketamine?
induction agent (dissociative anaesthesia)
perioperative analgesic
restraint of fractious cats (sprayed in mouth)
Combined with other drugs for sedation (IM or IV)
What is the mechanism of action of ketamine?
NMDA receptor antagonist on inhibitory neurons => glutamate release
What can be found in tier 1 of chronic pain management?
COX-inhibiting and non-COX-inhibiting (EP4 receptor antagonist) NSAIDs
Non-drug treatments: omega-3 fatty acids, encourage activity, environmental modification, weight management, surgery
What can be found in tier 2 of chronic pain management?
Adjunctive drugs to tier 1
Steroids (cats and dogs) or acetaminophen (dogs only) - broad analgesics
Intra-articular steroids
Disease-specific drugs
Therapeutic therapies - acupuncture, laser therapy etc.
Describe tier 3 of chronic pain management
Intra-articular antibiotics
Tramadol (lack of efficacy in dogs, cats have a strong aversion to its taste)
Nutritional supplements
localised surgical denervation
What can be used as adjunctive to analgesia in chronic pain management?
Hydrotherapy & physiotherapy
Chondroprotectives
Exercise management
Weight control & diet
Joint replacement/salvage
Anti NGF Ab (Librela, Solensia)
Irap (Interleukin-1 Receptor Antagonist Protein)
Accupuncture
Other drugs: garlic & fenugreek, sodium hyaluronate (Hyonate), prednoleucotropin (PLT), steroids, paracetamol (not cats)
Stem cell therapies (MCS)
What is mode of action of mesenchymal STEM cells in chronic pain management?
(adipose tissue-derived medicinal signalling cells)
exerted primarily through their secreted factors, including extracellular vesicles and bioactive molecules such as chemokines, cytokines and growth factors
These paracrine factors have a range of immunomodulatory, anti-inflammatory, angiogenic and anti-apoptotic properties
What is the effect of cannabinoids?
act on peripheral, spinal & supra-spinal sites to exert antinociceptive and antihyperalgesic effects (not licensed in UK)
