Pain Flashcards
Why is pain important to a veterinarian?
Animal welfare - prevent suffering, ethical and professional responsibility
Behavioural consequences - anxiety, fear, sleep deprivation, self-trauma and aggression
Physiological consequences - stimulate the sympathetic nervous system, decreased immunity, impaired wound healing, gut stasis, anorexia, immobility and muscle atrophy, increased blood viscosity and platelet aggregation
Pain Pathway - Transduction
begins at the sensory receptors and they trigger electrochemical signals that are transmitted to the brain
Mechano = physical distortion such as pressure and stretch
Thermo = warmth/cold receptors
Chemo = chemical alterations such as electrolytes and pH
Nociceptors = extremes of pressure, temp and chemical (warning)
Pain Pathway - Transmission
stimulus transmitted to the dorsal root ganglia via A𝛿 and C fibres, synapsing with other neutrons, amplifying or inhibiting the pain impulse
Aβ = sense light touch and movement, primarily on the skin
A𝛿 = sharp, localised first pain on the skin
C fibres = poorly localised, dull, intense, burning pain that is common in the viscera
Pain Pathway - Projection
Spinothalamic tract = superficial pain and touch
Spinoreticular tract = deep pain and visceral sensations
Pain Pathway - Perception
Recognition and processing of information to product an integrated response
Pain Pathway - Modulation
Results in an increase or decrease in the nociceptive signal
Downregulations:
Segmental inhibition = activation of low-threshold mechano receptors that reduce pain sensation such as rubbing an injured area, apply heat or ice
Upregulation:
Hyperalgesia = increased response to noxious stimulus, lowering the pain threshold
Allodynia = painful response to a stimulus that does not normally provoke pain
Acute Pain
Hypersensitizes the area around the wound to maintain preservation for healing
E.g. soft tissue trauma and inflammation
Chronic Pain
Pain lasting longer then 3-6 months
Provides no useful biological function and can effect QOL
E.g. cancer pain, osteoarthritis, phantom limb pain
Incisional or superficial/cutaneous pain
Acute and short duration sharp pain that is carried by A𝛿 fibres
Inflammatory pain
Pain persists after initial stimulus
Hyperalgesia occurs
E.g. after tissue injury
Visceral pain
Nociceptive arising from organs due to distension, torsion, inflammation, ischemia etc.
Impulses are carried by C fibres
Neuropathic pain
Disease or dysfunction of the PNS or CNS resulting in burning or excruciating pain
E.g. spinal cord injuries, IVDD, discospondylitis
Opioids
Full Mu agonists - moderate to severe pain = morphine, methadone, fentanyl and remifentanil
Partial Mu agonist - mild to moderate pain = bruprenorphine
Kappa agonist - mild pain and sedation = butorphanol
Good for acute pain, premed, intra-operative and post-op analgesia
Reversible and good efficacy with little cardiovascular side effects
Tramadol
Mild to moderate musculoskeletal, orthopaedic and neurogenic based pain
NSAIDs
Block COX and inhibit prostaglandin synthesis
Only to be used in patients that are cardiovascularly stable and hydrated with normal renal function
Cannot be used with NSAIDs or corticosteroids
Can be used with Tramadol or Gabapentin
