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ANAESTHESIA > 6. Pain and Analgesia > Flashcards

6. Pain and Analgesia Flashcards

1
Q

What is pain?

A

assessing pain is part of EVERY exam
Pain = suffering
Prevention of pain is part of 5 freedoms
1. Freedom from hunger and thirst,
2. Discomfort
3. disease, injury pain
4. Distresss
5. Express normal behaviour

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2
Q
A
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3
Q

WHat are some of the most common causes of chronic pain?

A

osteoarthritis, dental dz, cancer, otitis media, cystitis, pancreatitis, trauma (fracture, muscle injury)

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4
Q

What are the consequences of untreated pain?

A
  1. Catabolic state - cachexia
  2. Immune suppression - inc risk of infection, longer hospital stays; longer healing times
  3. Inc anes risk - higher doses of anes req to maintain a proper plane of anes
  4. Patient suffering and stress - affects outlook, behaviour, ability to perform basic functions (mobility, eating, drinking, urinating/defecating, sleep)
  5. Client suffering and stress
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5
Q

How can we predict pain?

A

Pain can interfere w/ PE
Pre-exam analgesia is indicated in some situations - analgesia should not mask the clinical signs
Certain procedures/conditions are painful - sx, hip rads on arthritic animal, PE on animal w/ back pain, colic, otoscope exam if severe otitis
Examining a patient presenting for trauma (ex. HBC)

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6
Q

What are some indicators of more acute pain?

A

sympathetic signs like inc HR, RR, BP
Shallow/exaggerated/abdominal breathing; panting (dogs); open mouth breathing (cats)
Pale MM (peripheral vasoconstriction), dilated pupils
Change in temp, sweating
Acute abdomen, colic (rolling, weight shifting), arch back

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7
Q

What are some more chronic signs of pain?

A

lameness, stiffness, weight shifting, exercise intolerance, refusing to sit, postural change
Change in sleep patterns, lack of grooming, vocalization-species dependent, decreased appetite, weight loss
change in behaviour: refuse to move, aggressive; protecting painful parts of body, cats hide, dogs seek attention, horse/cattle separate from herd

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8
Q

How can we monitor for pain?

A

symptom; not a dx
Sx patients - assess every hour for pain
Acute pain needs to be monitored more frequently; chronic pain is monitored less frequent
Clients can be helpful in assessing pain - they know their pet’s normal behaviour
Stress can mask pain
Varies btw species and breed
Cats do not show pain well, must be very painful
Exotics and birds hide pain - often emerg by time of noticing

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9
Q

Assessing response to therapy

A

if analgesia plan is working, clin signs and behaviours associated with pain will dec
HR, RR, body position/posture will return to normal
improved mobility, appetite, grooming
interaction with people, socializing
Pain score will dec
Can use empirical tx too (treat symptoms as they occur)

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10
Q

What is analgesia

A

relief of pain w/o loss of consciousnness

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11
Q

What is an analgesic

A

drugs that relieve pain

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12
Q

What is nociception?

A

perception of a painful stimuli by the nervous sstem

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13
Q

What is a nociceptor?

A

pain receptor: may be specific for detection of chemical stimulus, thermal stimulus or mechanical

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14
Q

What is pysiological pain?

A

protective sensation
conscious pain w/ minimal to no tissue injury
teaches us to avoid things that are potentially harmful
ex. touching a hot surface

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15
Q

What is pathological pain?

A

pain due to tissue injury
Describes as follows
A. Acute or chronic
B. Mild > Mod >Severe
C. Cause: traumatic, inflam, psychological
d. Origin: visceral vs somatic

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16
Q

What is visceral pain?

A

pain originating from the organs - colic, spay, renal pain, pancreatitis

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17
Q

What is somatic pain

A

pain originating from the musculoskeletal system
superficial somatic pain - originates from nociceptors in the skin
Deep somatic pain - originates from nociceptors in the muscle, bone, joints

18
Q

What is the 4 steps of the pain pathway?

A
  1. transduction
  2. transmission
  3. modulation
  4. conscious perception
19
Q

What is transduction?

A

physical stimulus - thermal, chemical or mechanical will turn on the nociceptor. signal is converted to an electrical signal

20
Q

What is transmission

A

electrical signal is relayed along the peripheral nerve, to spinal cord and the brain
3

21
Q

What is modulation

A

signal is suppressed or amplified as it passes along the spinal cord or in the brain

22
Q

What is the conscious perception of pain?

A

electrical signal is processed in the brain; individual becomes aware of the painful stimulus

23
Q

What is pain modulation?

A

same painful stimulus can be perceived differently (more painful or less) depending on individual
signal can be altered - either heightened or dampened - as it passes from the periphery to the brain - pain modulation
Most common types: peripheral hyperalgesia
Central hyperalgesia (Aka wind-up pain)

24
Q

What is peripheral hyperalgesia?

A

Primary hyperalgesia, local hyperalgesia
inc sensation to pain
due to inflam @ site where pain occurred - tissue damage causes inflam = release of inflam mediators like prostaglandins and substance P. These chemicals act on nociceptors @ orig site and dec activation threshold (easier to turn on)
In other words, area is hypersensitive to further stimulus
NSAIDS and steroids effective at blocking inflam pathway

25
Q

What is central hyperalgesia?

A

aka. 2nd hyperalgesia “wind-up pain”
occurs w/ chronic pain
Can reduce by providing pre-emptive analgesia
Constant transmission of pain signals along spinal cord causes pain fibers to become hyper excitable
Pain fibers more readily activated by stimuli originating anywhere in body. In other words, there is inc perception of pain originating from anywhere in body
Harder to tx and persists longer

26
Q

What is allodynia?

A

a type of hyperalgesia where pain is prod by a stimulus that would not normally cause pain ex. a feather stroking the skin
Vs. hyperalgesia is an inc sense of pain to something that would typically cause lower levels of pain
Responses are associated w/ neuropathic pain

27
Q

What is multi-modal pain thereapy?

A

using multiple drugs with each a diff mechanism of action. ex. each drugs target a different part of the pain pathway
Advantages:
1. reduce dose of individual nalgesic drugs
2. when used peri-operatively, can reduce dose of anesthetic required
3. dec dose means fewer risks and s/e for each individual drug

28
Q

What is perioperative analgesia?

A
  1. pre-sx = pre-emptive analgesia as part of premed
  2. intra-operative analgesia - main method of pain control is general anesthesia, GA stops conscious perception of pain, GA does not block steps 1-3 of the pain pathway, can add local anesthetic blocks
  3. Post-operative analgesia
    I. immediately post-operative (in-hospital)
    ii. medication TGH, may be req for chronic use
29
Q

What is pre-emptive analgesia?

A

admin b4 pain occurs
ex. analgesic as part of premed
Ideally, drugs used for pre-emptive analgesia should also provide or enhance sedation like opioids - excellent analgesia, A2 agonists - block nociceptors and substance P, ketamine - moderate somatic analgesia
Pre-emptive analgesic that do not enhance sedation include NSAIDS and blocks w/ local anesthetics
Avoid steroid use pre-op as may impair healing

30
Q

What are the benefits of pre-emptive analgesia

A
  1. Reduces overall req for anesthetic drug(s) - less CNS depression, fewer GA-related drug adverse effects, faster recovery
  2. Reduces overall requirement for post-op analgesia - dec dose AND duration of post-op analgesia
  3. Less pain = less stress; dec psychological costs associated w/ pain
  4. most effective method of preventing windup
31
Q

What are the different classes of analgesics?

A

opioids - injectable opioids (morphine, hydromorphone, meperidine, butorphanol, buprenorphine, methadone), tramadol, fentanyl patch, gabapentin
Monoclonal Ab therapy (solensia)
Local anesthetics
Ketamine
A2 agonists
Anti-inflammatories - NSAIDS, steroids

32
Q

What are some injectable in-hospital and TGH?

A

injectable: hydromorphone, fentanyl, oxymorphone, morphine, meperidine, butorphanol, buprenorphine, methadone
TGH: butorphanol, buprenorphine, tramadol, fentanyl patch

33
Q

How can opioids act as analgesics?

A

drugs vary in potency, duration of action, s/e
Pure mu agonists are best choice for analgesia
Kappa-agonist can treat mild to mod pain
Better analgesia if combined with NSAIDS
major s/e = sedation, resp depression, GI stasis

34
Q

What is methadone?

A

comfortan
Comes as 10mg/ml injectable in a 5ml vial
For premed and for post-op pain w/ Ovariohysterectomy and castration in CATS - IM injection
MOA: mu agonist opioid - binds and activates the mu opioid receptors

35
Q

What is the pharmacokinetics of methadone?

A

absorption: good absorption following IM injection - if accidental SQ injection, absorption is slower/unreliable
Distribution: very large volume of distribution- drug likes to accumulate intracellularly in tissues
Metabolism: primarily metabolized in the liver
Excretion: via the kidneys - altho most of drug is metabolized in the liver prior to excretion, a sm amount is not metabolized and is excreted in its active form

36
Q

What is the effects and adverse effects of methadone?

A

potent analgesic via activation of mu receptors
adverse effects are similar to all other mu agonists - resp depression, hyperactivity, occasional hyperthermia
Contraindications - resp or cardiac failure, liver/renal dysfunction, known cases of hypersensitivity

37
Q

What is fentanyl

A
  • Pure mu-agonist (no kappa activity)
  • 50 – 100X morphine
  • REALLY short acting (20 min if given systemic)
  • Can give as an epidural
  • Can give as CRI for sustained analgesia
  • Can use at higher dose with benzodiazepines or alpha-2
    agonists for induction and maintenance
  • Can also SEND HOME in the form of a sustained slow-
    release patch
  • Continuously releases small amounts of drug to maintain therapeutic
    levels
  • Side-effects same as for all mu-agonists
38
Q

What is the fentanyl patch?

A

transdermal delivery system
Perioperative analgesia for excellent pain control
patches come in set sizes/doses

39
Q

How to apply a fentanyl patch?

A
  1. loc: thorax, inguinal, base of tail (D), neck (H)
  2. prepare application site - close clip, 1cm clear margins (do NOT apply to skin that is broken), wipe skin w/ damp cloth (water only)
  3. press firmly w/ hand for 2-3m
  4. Coper patch with bandage
  5. label cover (drug name, dose, time + date of application)
  6. make sure anim cannot eat patch (cover well or e-collar)
  7. remove when no longer effective - gloves optional, return to clinic to dispose; may be residual drug present
40
Q

What is the pharmacokinetics of the fentanyl patch?

A

time to reach therapeutic lvls varies
Dog: 12-24h
Cat: 6-12h
H: 12+h
Duration (at therapeutic lvl)
Dog: 3d
Cat: 5d
H: 2d

41
Q

What are some fentanyl patch cautions?

A
  1. Never cut patch, cover half w/ water proof membrane
  2. make sure anim cannot eat it
  3. Make sure O do not have opioid sensitivities
  4. Do NOT use if fever - do NOT place heat source next to patch (water bottle). will inc absorption and risk OD
  5. Some patients develop skin reactions where patch is applied
  6. Caution w/ children: bring back for taking off and disposal
42
Q
A

ANAESTHESIA (8 decks)

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