Management of Chronic Pain Flashcards
(45 cards)
What is pain?
An unpleasant sensory and emotional experience, associated with actual tissue damage, or described in terms of such damage
It is a construction of our brains and is not a physiological parameter; there is no single entity of pain
How does pain affect an individual?
Sensory - discriminative
Cognitive - evaluative
Affective - emotional
What factors influence the variable relationship that exists between input and experience of pain?
3 main categories:
• Biological variables
• Psychological variables
• Sociocultural variables
Examples of these are below:
Genetics, demographics
Emotional context and psychological state
Previous damage and dysfunction
Characteristics of acute pain?
Usually there is obvious tissue damage and the pain is a consequences of protective functions
Increased NS activity
Pain resolves upon healing
Characteristics of chronic pain?
Pain extends beyond the period of healing and thus no longer has a useful purpose; it degrades health and function
Individuals have changes in pain signalling and detection
NOTE - chronic pain can be broadly divided into:
• Chronic cancer pain
• Chronic non-cancer pain
How can pain be measured?
Verbal rating scale - no pain (0), mild (1), moderate (2), severe (3)
Numeric rating scale - 0-10 with 0 being no pain and 10 being the worst pain imaginable
Visual analogue scale (uses emoticon faces)
Behavioural observations of a patient in pain?
Grimacing, frowning, crying
Rigid body posture
Limping
Physiological responses to pain?
Increased HR and BP; these are not sensitive or specific as indications of pain
NOTE - behavioural observations and physiological responses should not be used instead of self-reporting on a pain scale
How does pain become an emotion?
A painful stimulation on the skin passes, via Aδ-fibre and C-fibres, to the spinal cord (lamina I)
From here, the signal passes to the parabrachial nucleus and then to the amygdala hypothalamus; this is processed in the brain and attention is given to the stimulus
How is pain interpreted as a sensation?
A painful stimulation on the skin passes, via Aδ-fibre and C-fibres, to the spinal cord (lamina I)
From here, the signal passes to lamina V in the spinal cord; this is followed by the thalamus and primary somatosensory cortex
2 types of pain?
Nociceptive pain - appropriate physiologic response to painful stimuli, via an intact NS
Neuropathic pain - inappropriate response caused by a dysfunction in the NS
Description of neuropathic pain?
Burning, shooting, tingling, sensitivity
Examination of neuropathic pain?
Allodynia - pain from a stimulus that is not normally painful, e.g: cotton wool
Hyperalgesia - more pain than expected from a painful stimulus, e.g: pinprick
Common causes of neuropathic pain?
Shingles and post-herpetic neuralgia
Surgery
Trauma
Diabetic neuropathy
Amputation
Many types of neuropathic pain have unknown origin
At which locations does the NS change?
At the periphery, the nerve axons, spinal cord and brain
This is referred to as neuroplasticity
Importance of early and effective treatment of pain?
Assoc. with better outcomes:
• A lower degree of chronicity relates to a better therapy result, i.e: not treating adequately at an early stage is assoc. with pain becoming more difficult to treat
• Chronic pain assoc. with morphological change in the CNS
• Once present, pain is often persistent and seldom totally resolves, even with treatment
• Chronic pain causes a lot of suffering and marked -ve effects on wellbeing and QoL
WHO ladder for pain Mx?
ADD IMAGE
Non-opioid analgesics, e.g: NSAIDs, paracetamol
Opioid analgesics, e.g: tramadol, codeine, morphine and oxycodone
Adjuvants:
• Anti-depressants, e,g: amitriptyline, dyloxetine
• Anti-convulsants, e.g: gabapentin, pregabalin
• Topical analgesics, e.g: capsaicin, lidocaine 5% plaster
Local anaesthesia (peripheral nerve or nerve plexus)
Efficacy and mode of action of NSAIDs (non-opioid analgesics), e.g: aspirin, ibuprofen?
Mainly act on nociceptive pain:
• Inhibit COX
• PG synthesis decreases
Side effects of NSAIDs?
GI irritation / bleeding
Renal toxicity
Potential drug-drug interactions
CV side effects
Efficacy and mode of action of paracetamol (non-opioid analgesics), e.g: panadol?
Has analgesic and anti-pyretic effects:
• Inhibit CENTRAL PG synthesis (complete mode of action is unclear); it differs from NSAIDs due to its predominantly central action
Does not possess any anti-inflammatory action
Side effects of paracetamol?
Risk of toxic liver damage (at high doses)
Efficacy of opioid analgesics e.g:
• Tramadol and codeine (weak opioids)
• Morphine and oxycodone (strong opioids)
Mainly effective in nociceptive pain and only partially effective in neuropathic pain
Less effective in chronic states
Mode of action of opioid analgesics?
Activate the endogenous analgesic system:
• Stimulate receptors in the limbic system to eliminate the subjective feeling of pain
• Affect descending pathways that modulate pain perception
• Reduce ascending pain signal transmission in the spinal cord
Side effects of opioid analgesics?
N&V
Constipation
Dizziness or vertigo
Somnolence
Dry skin and pruritus
