230 Pain Flashcards
What is the definition of chronic pain?
Pain which persists longer than normal healing times
What are the 4 components of the IMMPACT guidelines for chronic pain?
- Pain intensity
- Physical function
- Emotional function
- Participant rating of improvement
Which hereditary condition is due to mutations in the voltage gates Na channels?
Congenital insensitivity to pain
What is the TRPV-1 receptor?
Capsaicin receptor which is activated with heat or cold
Pain when >43 degrees
What are A-delta fibres?
Myelinated nociceptors - quick, unimodal
What are C-fibres?
Unmyelinated nociceptors
What are A-beta fibres?
Nerves which detect pressure and tactile sensation - can inhibit nociception
Name 3 endogenous opioids
Endorphins
Enkephalins
Dynorphins
Through which part of the spinal cord do 1st order spinothalamic neurones ascend 1-2 levels in the spinal cord before decussating?
Lissauer’s fasciculus
Where in the grey matter do 1st order neurones synapse with 2nd order neurones in the spinothalamic tract?
Substantia gelatinosa
Name 3 parts of the brainstem which receive fibres from the spinothalamic tract
Periaqueductal grey
Locus coeruleus
Raphe nucleus
What do the descending tracts from the brainstem stimulate spinal interneurones to release in the feedback system?
Enkephalins
What 2 things do the enkephalins released from the spinal interneurones cause to ‘dampen down’ pain APs?
- Inhibits NT release from the presynaptic neurone
2. Hyperpolarises the post-synaptic membrane
Which opioid receptors do endorphins have the highest affinity for?
Miu
Which opioid receptors do enkephalins have the highest affinity for?
Delta
Which opioid receptors do dynorphins have the highest affinity for?
Kappa
Which inflammatory factors activate/sensitise nociceptors during inflammation?
(4 listed)
ATP
PGs
Bradykinin
Histamine
What is the action of substance P in nociception?
Stimulates release of histamine
Dilates blood vessels
What is primary hyperalgesia?
Increased pain sensitivity immediately following tissue injury
What is the treatment for trigeminal neuralgia?
Carbamazepine
Which NSAID has the lowest thrombotic risk?
Naproxen
Name 2 weak opioids
3 listed
Codeine
Dihydrocodeine
Tramadol
What is the treatment for opioid O/D?
Naloxone
Name 3 strong opioids
5 listed
Fentanyl Morphine Oxycodone Methadone Pethidine
Which strong opioid is strongest against kappa and delta opioid receptors?
Oxycodone
Name 2 common opioid S/E
5 listed
N&V Drowsiness Unsteadiness Delerium Constipation
What is the MOA of ketamine?
NMDA receptor antagonist
What is the intensive theory of pain?
Pain = emotional state caused by intense stimuli
What is Descartes theory of pain?
Single wire theory - pain has its own apparatus independent of other senses
What is the gate theory of pain?
Pain is not just related to extent of tissue damage - can have things which ‘open’ and ‘close’ pain gate.
Name 2 things which open the ‘pain gate’
5 listed
Negative thoughts Pain watching Anxiety and panic Sedentary lifestyle Fear of pain
Name 2 things which close the ‘pain gate’
5 listed
Distraction Happiness and laughter Relaxation and calm Excercise Reassurance
What is dolorimetry?
Measuring pain threshold
What is the MOA of tramadol?
Inhibits reuptake of NA
Stimulates serotonin release
What are celecoxib and etoricoxib?
COX2 inhibitors
What is the precursor for COX enzymes?
Arachidonic acid
What does COX 1 stimulate?
3 listed
Thromboxane A2 for platelet aggregation
PGs in upper GIT - gastroprotective
PGs in kidneys - renal perfusion
What is the peak-end rule?
Theory that the last pain you felt of e.g. a procedure in the one you remember despite the intensity of the pain prior to the end pain.
