Week 10: Pain Flashcards
What is pain?
- an unpleasant sensory AND emotional experience associated with actual or potential tissue damage or described in terms of such damage
- measurement is subjective
What is the area that lights up as you imagine pain?
the insula cortex (behind the lateral sulcus)
What are the components of the pain matrix?
Sensory/discriminative:
- thalamus
- somatosensory cortex
Affective:
- brain stem
- limbic system
- amygdala
- hippocampus
- basal ganglia
- pre frontal cortex
- insula
Associative:
-posterior parietal cortex
Which area in the brain is responsible for the visceral nature of pain?
the brainstem as it controls autonomic functions of the body e.g heart rate, GI
Which pathway is pain transmitted through?
the lateral spinothalamic tract
How is excessive pain disproportionate to injury?
- pain is worse if patient is tired/ anxious
- suggestion that something is going to be very painful makes it painful
What is a nocebo?
delivering negative information when given treatment e.g saying a LA cream will increase pain when it won’t
How is pain modulated?
You can become more or less sensitive to pain:
- gate control theory of pain or descending inhibitory pain fibres
- these fibres come down from the brain and act to inhibit pain
What type of fibres do nocioceptors send?
Ad and C fibres
What happens when inhibitory interneurons are activated?
this releases opoids at the synapse to reduce the chance of any depolarisation at the synapse to reduce the C fibre input
Which fibres modulate pain?
Descending pain modulating fibres
Where do pain fibres synapse?
substantia gelatinosa
What is the main neurotransmitter in the descending inhibitory pathway
serotonin and noradrenaline
What are the two important classifications of pain?
- Nociceptive vs neuropathic
2. acute vs chronic
What is nociceptive pain?
Pain due to tissue damage and inflammation
What is neuropathic pain?
- Pain initiated or caused by a primary lesion or dysfunction in the CNS or PNS (damage to nerve fibres)
- intense continuos pain that can be accompanied with pins and needles, hyperalgesia, numbness, loss of co-ordination
- often constant, not reduced by rest
- associated with severe co morbidity and poor quality of life
What are some conditions that can cause neuropathic pain?
- post herpetic neuralgia
- painful diabetic neuropathy
- trigeminal neuralgia
- phantom pain
What is allodynia?
brushing of the skin causes intense pain
How do we treat noiceptive pain?
- rest
- exercise
- allow repair
- normal WHO ladder - paracetmol, NSAIDs, weak opioids (usually responds to pain killers)
How do we treat neuropathic pain?
- neuropathic pain killers - gabapentin, amitriptyline
- spinal cord stimulation
- often doesn’t respond to pain killers
What is acute pain?
- associated with trauma or injury
- usually nociceptive
- proportional to magnitude of injury
- evolutionary protective function
- assists with wound healing
- resolves with healing
What is chronic pain?
- pain that persists past normal duration of tissue healing
- 3 months but arbitrary
- may be dissociated from tissue damage
- no obvious protective function
- causes distress and suffering
Explain the WHO analgesia ladder from bottom to top:
- Non-opoid
- paracetmol
- NSAIDs - Opoid (in increasing severity)
- tramadol
- dihydrocodeine
- codeine
- fentanyl
- morphine
What type of pain is the WHO analgesia ladder for and why?
acute pain
should NOT apply in chronic pain due to the addictive effects of opoids
When should opioids not be used?
In chronic pain:
- when the risk of harm from opioids increases with increased dose but there is no increased benefit
- if a patient is using opioids but is still in pain, the opioids are not effective and should be discontinued
How do we measure pain?
Pain = noiceptive input + biopsychosocial phenomena
What is the VAS scale?
- 0-10 VAS numeric pain distress scale
- ask patients where they are on the scale
Why might pain killers not work?
- biopsychosocial factors
- tolerance
- misdiagnosis
- incorrect dose
- aren’t tolerated
- they aren’t very effective
What are the four dimensions of pain conceptualized by Loeser?
- Nociception
- Pain
- Suffering
- Pain behaviours
What is lumbar radiofrequency?
- burning nerves at joints
- to reduce back pain
What is spinal cord stimulation?
- reduces nerve pain by stimulating dorsal columns
- involves the delivery of energy to the spinal cord through electrodes in the epidural space
- works by delivering small electrical pulses to the pain sensing pathways of the spinal cord, effectively altering the pain signals travelling to the brain
What is the celiac plexus block most commonly used for?
pancreatic carcinoma and upper abdominal neoplasia
