The experience of pain Flashcards
Definition of pain
general takeaway messages about pain
“An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.”
- pain is always a personal experience that is influenced to varying degrees by biological, psychological and social factors.
- Pain and nociception are different phenomena. Pain cannot be inferred solely from activity in sensory neurones.
- Through life experiences, people learn the concept of pain.
- A person’s report of an experience as pain should be respected.
- Although pain usually serves an adaptive role, it may have adverse effects on function and psychosocial wellbeing
- Verbal description is only one of several behaviours to express pain- inability to communicate does not negate the possibility that a human exeperiences pain.
nociception
is the neural processes of encoding and processing noxious stimuli
Pain has 2 dimensions to it what are they
- discriminative- allowing us to locate tissue damage
- affective/ aversive- unpleasant and emotional
pain is part of what system?
it conveys info about physical stimuli from the periphery to the brain, which modalities are included
what is the common neural pathway from the periphery to the brain
somatosensory
it includes modalities of touch, temperature, proprioception and pain
peripheral receptor– 1st order– 2nd order– 3rd order neurone
1* neurone is the primary afferent. Cell body found in the dorsal root ganglion. Axon projects into the dorsal horn.
What nerve fibre endings do nociceptors end in?
nociceptor fibres are polymodal; they respond to a variety of which kind of stimuli?
Adelta
- fast pain, fast withdrawal reflex
C fibres
- slow, dull throbbing pain associated with inflammation
mechanical, thermal and chemical
nociceptors have a HIGH threshold for mechanical and thermal stimulation
visceral nociceptors
similar to Adelta and C found in periphery but respond to distension and ischaemia
What are the rexed laminae
10 layers of gray matter identidfied in the dorsal horn
Which parts of the spinothalamic tract does
- a) touch
- b) pain (fast + slow) and temperature
ascend in
types of pain
acute/ chronic
nociceptive
nociplastic
neuropathic
referred
nociceptive pain
pain that arises from actual or threatened damage to non-neural tissue and is detected by the activation of nociceptors
Neuropathic pain
pain caused by a lesion or disease of the somatosensory nervous system
can be split into central or peripheral by which part of the nervous system is affected
nociplastic pain
pain that arises from no clear evidence of actual or threatened tissuse damage causing the activaation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing pain
measurement systems of acute pain (3)
unidimensaional and designed for the assessment of pain intensity and degree of pain relief
- visual analogue scale (VAS)
- numeric rating scale (NRS)
- Categorical verbal rating scale (VRS)
visual analogue scale
considered gold standard
100mm unmarked line with stardadised wording at each end “no pain” and “worst pain imaginable”
does not give instant rating
requires explanation to patient
Numerical rating scale
uses an 11 point scale
0- no pain
10- worst pain
verbal rating scale
uses words to describe the magnitude of pain
none, mildm moderate, severe
less precise and less sensitive
language can be a barrier
Wong baler FACES pain rating scale
FLACC behavioural pain scale
grades response to pain 1-3 by looking at 5 different areas:
- face
- legs
- activity
- cry
- consolabilty
Higher score is bad
if they are awake, observe for at elast 2-5 mins, if asleep at least 5 mins
0- relaxed and comfortable
1-3= mild discomfort
4-6= moderate pain
7-10= severe discomfort
mulitdimensional pain scales (1)
McGill pain quiestionnaire
brief pain inventory
Screening tools for neuropathic pain
painDETECT
NPS- neuropathic pain score
and many more
treatment of pain
- important to identify patients who are likely tp experience difficult pain postop
- education important- adhere to treatment
- wherever possible use regional or local anaesthetic
name some adjuvants to anaesthetic
NMDA antagonists
Gabapentinoids
Clonidine
Dexamethasone
the opiod system has 4 types of receptors:
which one is mainly used to eilicit analgesia
- u (MOP)
- delta (DOP)
- k-opioid
- nociceptin (NOP)
nociception mainly from u receptors
Mechanism of action of opiates
- Mimic the actions of endogenous opiod peptides by interacting with u, delta or K opioid receptors.
- receptors are coupled to Gi proteins and the actions are mainly inhibitory
- presynaptically they close N type voltage gated calcium channels (influx) inhibiting the release of nociceptive NTs like substance P and glutamate
- postsynaptically open potassium channels (efflux) which hyperpolarises the cell, decreasing neuronal excitabillity
- they also decrease intracellular cAMP by inhibiting adenylyl cyclase which modulates the release of nociceptive NTs like substance P
NSAID mOA
reversibly (paracetamol) or irreversibly (warfarin) inhibit the action of the COX enzymes needed for prostaglandin synthesis
(fatty acids– membrane phospholipids (phospholipase)– arachidonic acid (COX)– prostaglandin H2– prostacyclin, prostaglandins, thromboxane A2
Congenital insensitivity to pain
patient lacks to ability to perceive physical pain
can sense the difference between sharp/ dull hot/ cold but can’t tell a hot drink is burning their tongue
caused by a mutation in SCN9A gene- normally encodes for the alpha subunit of the NaV1.7 sodium channel responsible for Na+ transport
