The pharmacology of pain control Flashcards
What is pain?
Subjective
Complex
“What the patient says hurts”
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”
Describe acute pain
Minutes, hours, days
Well defined onset
Associated with objective and subjective physical signs
Hyperactivity of the autonomic nervous system
Responds well to analgesia and treatment of underlying problem
Describe chronic pain
Weeks, months
Associated with significant changes in lifestyle, function and personality
More challenging management
State a cause of somatic nociceptive pain
Activation of nociceptors in skin, muscle and bone
State a cause of visceral nociceptive pain
Activation of nociceptors from stretching, distension or inflammation
State a cause of neuropathic pain
Direct damage to PNS or CNS
What are the symptoms of somatic nociceptive pain
Localized, aching, throbbing, gnawing
What are the symptoms of visceral nociceptive pain
Poorly localized, deep aching, cramping, pressure
also referred pain
What are the symptoms of neuropathic pain
Burning, shooting, stabbing, electric shock. May be associated altered sensation. Often dermatomal
Give examples of neuropathic pain
Damage to nerve plexus, post herpetic neuralgia, spinal cord compression, diabetic neuropathy
Give examples of visceral nociceptive pain
Bowel obstruction, pancreatic cancer, liver metastases
(capsular pain)
Give examples of somatic nociceptive pain
Bone metastasis, tumour invasion into soft tissue, muscle spasticity
Name two types of pain classified in terms of pattern
Background pain
Breakthrough pain
What is total pain?
The cumulative of social, psychological, physical and spiritual pain
Describe the ascending pain pathways
Nociceptors (receptors)
A-delta fibres (fast transmission of sharp localised pain)
C-fibres (slow transmission of dull burning chronic pain)
Spinal ganglia
Dorsal horn (pain signal is modified)
Lateral spinothalamic tract
Pain perception point
Somatosensory cortex and other areas of the brain
Where does pain processing occur in the brain?
Somatosensory cortex
Prefrontal cortex
Thalamus
What factors play a role in pain processing?
Mood
Beliefs
Cognition
Genetics
Describe the descending pain pathway
Cortex Thalamus Periaqueductal grey matter Rostral ventral medulla Dorsal root ganglia Spinal cord
What do the periaqueductal grey matter and the rostral ventral medulla contain?
High levels of opioid receptors
What does the 5HT/NA neuron control?
Controls/inhibits communication between the 1st and 2nd order neuron in the ascending pathway
Describe the WHO analgesic ladder
Non-opioid analgesic +/- adjuvant
Weak opioid analgesic +/- Non-opioid analgesic +/- adjuvant
Strong opioid analgesic +/- Non-opioid analgesic +/- adjuvant
List some non opioid analgesics
NSAIDs
Paracetamol
Aspirin
List some weak opioid analgesics
Tramadol
Codeine
Dihydrocodeine
List some strong opioid analgesics
Morphine Oxycodone Fentanyl Diamorphine Alfentanil Hydromorphone
