The experience of pain

Question 1

Definition of pain

general takeaway messages about pain

Answer 1

“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.

Question 2

nociception

Answer 2

is the neural processes of encoding and processing noxious stimuli

Question 3

Pain has 2 dimensions to it what are they

Answer 3

1. discriminative- allowing us to locate tissue damage
2. affective/ aversive- unpleasant and emotional

Question 4

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

Answer 4

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.

Question 5

What nerve fibre endings do nociceptors end in?

nociceptor fibres are polymodal; they respond to a variety of which kind of stimuli?

Answer 5

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

Question 6

visceral nociceptors

Answer 6

similar to Adelta and C found in periphery but respond to distension and ischaemia

Question 7

What are the rexed laminae

Answer 7

10 layers of gray matter identidfied in the dorsal horn

Question 8

Which parts of the spinothalamic tract does

• a) touch
• b) pain (fast + slow) and temperature

ascend in

Question 9

types of pain

Answer 9

acute/ chronic

nociceptive

nociplastic

neuropathic

referred

Question 10

nociceptive pain

Answer 10

pain that arises from actual or threatened damage to non-neural tissue and is detected by the activation of nociceptors

Question 11

Neuropathic pain

Answer 11

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

Question 12

nociplastic pain

Answer 12

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

Question 13

measurement systems of acute pain (3)

Answer 13

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)

Question 14

visual analogue scale

Answer 14

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

Question 15

Numerical rating scale

Answer 15

uses an 11 point scale

0- no pain

10- worst pain

Question 16

verbal rating scale

Answer 16

uses words to describe the magnitude of pain

none, mildm moderate, severe

less precise and less sensitive

language can be a barrier

Question 17

Wong baler FACES pain rating scale

Question 18

FLACC behavioural pain scale

Answer 18

grades response to pain 1-3 by looking at 5 different areas:

1. face
2. legs
3. activity
4. cry
5. 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

Question 19

mulitdimensional pain scales (1)

Answer 19

McGill pain quiestionnaire

brief pain inventory

Question 20

Screening tools for neuropathic pain

Answer 20

painDETECT

NPS- neuropathic pain score

and many more

Question 21

treatment of pain

Answer 21

• important to identify patients who are likely tp experience difficult pain postop
• education important- adhere to treatment
• wherever possible use regional or local anaesthetic

Question 22

name some adjuvants to anaesthetic

Answer 22

NMDA antagonists

Gabapentinoids

Clonidine

Dexamethasone

Question 23

the opiod system has 4 types of receptors:

which one is mainly used to eilicit analgesia

Answer 23

• u (MOP)
• delta (DOP)
• k-opioid
• nociceptin (NOP)

nociception mainly from u receptors

Question 24

Mechanism of action of opiates

Answer 24

• 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

Question 25

NSAID mOA

Answer 25

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

Question 26

Congenital insensitivity to pain

Answer 26

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