Pain Flashcards
what is pain
unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
what is pain influenced by
biological. social, cultural and emotional factors
what is sensing pain for
protective adaptation
rare genetic mutations in pain-sensing ion channels can cause congenital indifference to pain
what is acute pain
pain that lasts from a few minutes to less than 6 months
what is chronic pain
pain that lasts for more than 3 months
what communicates noxious stimuli to the brain
spinothalamic tract
describe peripheral sensation of pain
specialised nociceptive neurons sit in the epidermis
stimulus causes ion channels to open and depolarisation generates an action potential to pass the signal centrally
sensitisation increases the magnitude of the response to pain when the degree of noxious stimuli remains the same
what contributes to chronic pain
inappropriate sensitisation of ion channels
describe central modulation of pain
when the signal arrives at the thalamus, emotional, cognitive and sensory inputs come together and modulate the perception of pain
what is a possible explanation for why some people are more prone to chronic pain than others
variations in central pain modulation
what occurs after the noxious stimuli has been removed
under normal conditions, there is descending inhibition of pain sensation
emotions or anticipation of pain relief (placebo analgesia) can enhance this downregulatory system
what occurs in the periaqueductal grey matter
serotonin released here travels downwards and triggers endogenous opioid release in dorsal horn spinal cord interneurons
endogenous opioids reduce incoming pain pathway activity via opioid receptors (mu, kappa, delta) on inhibitory neurons
release of inhibition allows onward dopamine signalling, calming the pain stimulus and emotional response to pain
how is acute pain managed
promptly identify and treat underlying cause where possible
start at bottom of pain ladder, and work way up if pain still persists
if pain is very severe clinicians may start at top of pain ladder and work their way down
treat pain ‘around the clock’ with regular prescription, top-up with breakthrough dose as required
think about psychological factors, reassure and relax the patient
what is the pain ladder
bottom - non-opioid medication alone (paracetamol, NSAIDs)
middle - non-opioid medication and weak opioid (codeine) with or without adjuvant analgesic
top - non-opioid medication with strong opioid (morphine), with or without adjuvant analgesic
if starting at bottom review pain burden regularly and step up if pain persists
if starting at top, review response and step down or halt where possible to avoid adverse effects
what are features of neuropathic pain
pain in the absence of stimuli
painful sensation with innocuous stimuli (allodynia)
numbness
tingling (parasthesia)
feeling of insects crawling over the skin (formication)
abnormal sensation in affected areas (dysesthesia)
