Lecture 25 - An Introduction to Pain

Question 1

A major concern is when acute pain becomes…

Answer 1

chronic pain - very difficult to treat

Question 2

What are the different types of pain?

Answer 2

Nocioceptive - pin prick

inflammatory - hammer hit

Neuropathic - pain signal trapped in the nervous system = chronic pain

Question 3

Describe Acute nociceptive pain?

Answer 3

Immediate, short duration, localised

NS is activated

relay, amplification, attenuation

Reflex withdrawal response

Question 4

How is the transient potential receptor subunit (TPRV1) - ion channel pore related to pain?

Answer 4

responds to increases in acidity as well as capsaicin (the hot part of chili) and temperature

These are general nociceptors

Question 5

What is the general tissue response to Acute injury?

Answer 5

cell lysis, acid H+, ATP releae

releae of mediators: seretonin histamine, PROSTAGLANDINS, cytokes

nociceptors activated and sensitised

localised pain hypersensitivity occures

Question 6

What are the early and long term changes to nocioceptors?

Answer 6

early inflammation - amplification via receptor threshold and latency reduction

Long term changes - transcription mediated by cytokines and grwoth factors increase production of receptors, ion channels and neurotransmitters, causes Hyperalgesia (think about sunburn sensitivity)

Question 7

What is allodynia?

Answer 7

“pathological response” e.g excruciating pain with light tough - NS has been over-activated and changed to chronic pain stage

Question 8

What nerve fibres are involved in pain?

Answer 8

A-delta and C fibres - 70-90% of peripheral nerve

a-delta: Fast, sharp, acte, pricking localised pain mechanical and thermal pain

c fibres - slow pain aching, throbbing, burning pain, chemical pain

Question 9

Looking at the doral root horn, what is the main excitatory neurtransmitter and which receptors are responsible for pain

Answer 9

Glutamate is main excitatory NT

GABA - is inhibitory NT

NMDA - when Mg2+ is displaced there is cellular remodelling (protracted nociception)

Question 10

Which drug targets NMDA receptors?

Answer 10

Ketamine

Question 11

What other senses inhibit pain?

Answer 11

Endorphins

Question 12

Opioid receptors have a high concentration in the …

Answer 12

spinal cord

Question 13

What can dampen pain signals going up the spinal cord?

Answer 13

Descending noradrenergic and 5-HT3 fibres

these can inhibit the spinal dorsal horn and dampen incoming signals

Question 14

Amitryptilline simulates what?

Answer 14

The Descending noradrenergic and 5-HT3 fibres

Question 15

Gabapentin act on a ____ channel in the spinal cord

Answer 15

calcium

Question 16

Pain pathways project to ______ _____ and ___-_______ ___ ____

Answer 16

Superior colliculus and peri-acqueductal grey matter (PAG)

stimulation of PAG causes profound anagesia

endogenous opioids activate this area

This forms the basis for deep brain stimulation of intractible pain

Question 17

What happens when a patient has chronic pain?

Answer 17

There is an excessive pain response, leading to abnormal hyper-excitability and structural remodelling = phenotypic change

pain signal EMBEDDED within NS

15-20% can develop chronic neurpathic pan after traumatic injury

Question 18

pain genes can determine pain response

What is the ‘Stargazer gene’ (CACNG2)

Answer 18

a mutation in stargazin protein

mouse had absense seizures and ataxia in addition to susceptibility to neuropathic pain

Question 19

The human CACNG2 is associated with…

Answer 19

chronic pain! same gene as the one in mouse - research underway…

Question 20

How can genetics lead to lack of sensitivity to pain?

Answer 20

mutation in Na, 1,7 receptor gene - one of the key trasnmitters of pain

Question 21

What enzyme allows the conversion of codeine to morphine?

Answer 21

liver enyme CYP2D6

Question 22

What are the types of analgesic medication?

Answer 22

Opioids (mainstay for severe and moderate pain) - morphine

paracetamol

Aspiriin

NSAIDS

others

Question 23

What are opioid side effects?

Answer 23

Ventilatory depression

drowsiness and sedation

nausea and vomiting

Question 24

What are some pain management stragegies?

Answer 24

Multimodal analgesis - use of smaller doses of opioids in combination with other analgesis drugs

Pre-emptive analgesia - prior to surgery (thery: attenduate injury and neuroplastic repsonse

target nerve transmission - local anaesthesia (Lignocaine)

Remove cognition - general anaesthesia

Question 25

Opiods act not only at the spinal cord but..

Answer 25

at the periphery

Question 26

What are the limitations of Analgesic drugs?

Answer 26

individual responses

inadequate pain control

administration routes

dependance, addiction

multiple side effects

Question 27

What is given to a heart attack patient/

Answer 27

aspirin and morphine

Question 28

child with broken will get what from paramedics?

Answer 28

intranasal opioid - fentanyl - rapid analgesia

Question 29

Migrane pateints will get what in addition to Aspirin, ibuprofen?

Answer 29

vasocontrictors - as part of the problem is cerebral vasodilation

Question 30

What is used for Labour pain?

Answer 30

nitroux oxide

opioids can harm the baby so can’t give that..