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BVetMed - Animal Welfare > Pain > Flashcards

Pain Flashcards

1
Q

How do nociception and pain differ?

A

Pain is the subjective experience associated with nociception but also arising without a stimulus
Nociception is a neurophysiological term denoting a specific activity in neural pathways

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2
Q

What are nociceptors? What different types exist?

A

Afferent fibres and free nerve endings
Respond to force, heat, cold, chemicals - only above a certain higher than normal threshold when tissue damage is occurring.
May be polymodal or specific
- Alpha delta - myelinated, fast pain, some temperature specific, used for reflex responses
- C fibres - unmyelinated, slow pain, usually polymodal
- Alpha beta - non-nociceptive but will carry nociceptive signals sometimes, conduct most quickly

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3
Q

How may drugs affect nociceptors?

A

Different drugs act more potently on different fibres hence why some drug are better at alleviating some types of pain
eg. Opioids block C fibres, therefore are not good at blocking temperature.

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4
Q

Which tracts are responsible for different aspects of pain?

A

Spinothalamic -> thalamus, brainstem, cortex = mociception

Spinoreticular = emotional aspect

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5
Q

How are the neurone structured within the spinal cord?

A

In the dorsal horn reed laminae (layers I-V)
All spinothalamic and spinoreticular tracts decussate upon entry to the spinal cord
This organisation is maintained into the somatosensory cortex allowing for localisation of pain

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6
Q

Where is the first site of pain modulation?

A

Spinal cord

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7
Q

Which nerve pathways are more widely studied?

A

Cutaneous rather than visceral - easier to study

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8
Q

How is pain adaptive?

A

Evolutionary advantage to avoiding dangerous stimuli

- more relevant to acute than chronic pain

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9
Q

Give examples of research in different species attempting to elucidate whether pain is felt

A

Sneddon - rainbow trout will move away from a noxious stimulus but how can we know if this is high order cognition or just a reflex?
Robert Elwood - Hermit crabs will tolerate higher pain thresholds if only a worse shell is on offer to move to - suggesting not a reflex but more cognitive

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10
Q

How may age affect pain processing?

A

David Mellor - steroid levels in neonatal lambs -> lack of “consciousness” up to 6 hours
Craig Johnson - age/pain responses
> foetus surgery/abortion - analgesia?
> Precocious v altricial species

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11
Q

Outline two theories of pain modulation?

A

> Gate control theory - non painful/noxious stimuli close the gate (PRESYNAPTIC INHIBITION) and stop noxious stimuli getting through eg. rubbing after bumping yourself or TENS machine
Descending inhibition - PAG (periaquiductal grey) in the midbrain and RVM (rostral ventromedial medulla) conain high number of ovoid receptors and endogenous opioids.
- descending pathways project to the dorsal horn and are monoaminergic, utilising NA and 5HT as NTs.
- Nucleus raphe magnus also important

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12
Q

What does MNT stand for?

A

Mechanical nociceptive threshold

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13
Q

Which area of the brain is associated with pain?

A

Not one single part - the pain matrix
Multiple parts of the brain shown on fMRI to play a role
- disputed because similar patterns are observed for loud/bright/otherwise salient stimuli as well as noxious, swell as watching others in pain
> more likely to be a “threat matrix” or saliency matrix indicating saliency or threat of harm

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14
Q

Is the cerebral cortex necessary for feeling pain?

A

Not necessarily - may be other areas involved n other species

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15
Q

What does injury lead to?

A
  • release of inflammatory mediators -> hyperalgesia, allodynia
  • descending (usually antinociceptive) pathways may become pronociceptive
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16
Q

What are the three types of pain?

A

Physiological/nociceptive - Useful! Pinkprick pain, protects from damaging stimuli. Stops when stimulus removed
Inflammatory and neuropathic = clinical pain

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17
Q

What is the most common form of chronic pain noted in animals?

A

Chronic pain noted more commonly in humans, but..

Osteoarthritis commonest

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18
Q

Which psychological factors play a role in chronic pain issues?

A

Catastrophising - expecting the worst, learned helplessness and inactivity, depression - perpetuates physical mechanisms of chronic pain
Fear of pain - avoiding activities that cause the pain, leads to ^ pain perception when event occurs
- illness behaviour and social culture also play a role

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19
Q

What are the risk factors for development of CPSP?

A

Chronic post surgical pain

  • Younger people ^ risk
  • Anxiety/depression problems
  • Pre-op pain - upregulating pain pathways and making it harder to control pain peri- and post-op
20
Q

What are the 7 options for pin management in animals?

A 
Systemic analgesia eg. NSAIDS, opioids
Local analgesia
Change of practice - don't cause pain!
Rest
Physiotherapy 
Euthanasia
21
Q

Is it always possible to give an analgesic?

A

Companion animal - yes
Farm animal - potentially not - pet/commercial/hobby farm?
> strict legislation due to drug residue/food chain issues
> PETS aswel as commercial
> drugs must have known maximum residue limit and withdrawal period
> zero tolerance list that they are not allowed at all
> Must be recorded in a book
[-> WELFARE IMPLICATIONS!]

22
Q

When may change in practice be best effective?

A

Eg. keel bone fractures in laying hens - not practical to pharmacologically treat pain in individuals

23
Q

Give an example of withdrawal periods that may put the farmer off of giving analgesia?

A

Analgesia -> milk withdrawal

24
Q

Are horses a food producing animal?

A

YES unless passport signed to say they will never enter the food chain
- but equine passport system not robustly controlled

25
Q

What factors affect practicalities of analgesic administration?

A

Acute v long tern dosing
Ease of admin (owner compliance, no. tablets, palatability)
Cost
Tolerability (and side effects)
- involve owner in pain monitoring to encourage compliance

26
Q

How may drug effects differ between species?

A

May not even be analgesic! eg. opioids in birds
Doses cannot be extrapolated
- Requires specie specicifc research

27
Q

What are the problems associated with lab animal analgesia?

A 
Large numbers of animals 
Housed in groups 
how to administer 
Handling stressfull
Drugs may confound results (but then so may pain!)
28
Q

Give a study looking at analgesics in lab animals

A

Flecknell 1999 - use of oral buprenorphine for post-op analgesia in rats
- less weight loss
- increased food and water intake
Flecknell 1999 - sub cut requires lower doses than oral analgesia
Richardson and Flecknell 2005 - review anaesthesia and post-op analgesia in lab rodents
Has increased since 1990s but still very low
Change in typical anaesthetic combinations

29
Q

When should peri-operative analgesia first be given?

A

Preventitively - aim to attenuate effects of nociceptive barrage to CNA switching on pro-nocicpetive pathways

30
Q

What is multi-modal analgesia?

A

Concurrently combining different classes of drugs
eg. Opioids working on brain, + Local opioids working on dorsal horn spinal column, + local neasthetic to the peripheral nerves, + local analgesia to the peripheral noiceptors
+ NSAIDS

31
Q

Give some examples of analgesic drugs

A

Opioids, NSAIDs, keetamine, a2 ag, non-traditional analgesics eg. tramadol, local anaesthetic

32
Q

What is a typical analgesic combo?

A

Opiods and NSAIDs

33
Q

Outline different routes of administration of drugs

A

IV (opioids, ketamine, NSADs) - rapid onset, not painful if catheterised, predictable effect
IM/SC - repeated injections painful, volume of drug. SC - unreliable absorption, delay in onset, slightly less painful than IM
Epidural
Transdermal (fentanyl, lidocaine) - fentanyl licenced in dogs - 96 hours analgesia after single dose
Local infiltration
Topical (EMLA)

34
Q

How may opiods be classified?

A

delta/kappa/mue receptor agonists
M associated with analgesia
Agonist/partial agonist/antagonist
Duration of action

35
Q

What side effects may oioids have?

A

Motor side effects in horses -> box walking
Post-operative colic (but pain also -> gut stasis)
Decreased recovery quality

36
Q

What are NSADS indicated for?

A

Acute pain
Single shot analgesia - side effects preclude exceeding total daily dose
Useful for multi-modal
NSAIDs available have similar analgesic efficacy

37
Q

What are the side effects of NSAIDs?

A 
GI [most common and important - difficult to detect early. 16000 people die due to NSAID related gut issues]
Renal 
Liver
Blood clotting 
CNS
38
Q

How should analgesics be decide?

A

Individual basis

39
Q

What is necessary for correct NSAID administration?

A

Owner compliance - administered at home

Reliance on owners to detect side effects

40
Q

What ethically should be considered re. analgesia?

A

Should owners be legally blighted to pay for analgesia for their animal? - common to ask owners whether they want post-op analgesia after neutering

41
Q

What are effective treatments for chronic pain?

A

Largely elusive!

42
Q

Define pain according to IASP

A

Pain is an unpleasant sensory and emotional experience, unique to every individuals and associated with actual or potential tissue damage

43
Q

Where is the “seat of pain perception” said to be in mammals?

A

Cerebral cortex

44
Q

What are the two pain pathways and how do they differ?

A

Lateral - discriminitve nociceptive pathway - thalamus -> SI, SII
Medial - emotional and affective properties - thalamus -> SI, SII, limbic system

45
Q

What are the three “layers” of the pain experience?

A

Biological nociception
Pyschological emotions, distress
SOcial cutler and illness behaviour - animals lack this

BVetMed - Animal Welfare (19 decks)

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