What is pain and why should we treat it? Classification of pain

Question 1

What is pain?

Answer 1

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Unpleasant. Emotions are important. The cause is not always visible.
Pain is what the patient says hurts.

Question 2

What are the benefits of treating pain for the patient?

Answer 2

Physical: improved sleep, better appetite; fewer medical complications, e.g. heart attack, pneumonia.
Psychological: reduced suffering; less depression, anxiety.

Question 3

What are the benefits of treating pain for the family?

Answer 3

Improved functioning as a family member, e.g. as a father or mother.
Able to keep working.

Question 4

What are the benefits of treating pain for society?

Answer 4

Lower health costs, e.g. shorter hospital stay.

Able to contribute to the community.

Question 5

How is pain classified?

Answer 5

Duration: acute, chronic, acute or chronic.
Cause: cancer, non-cancer.
Mechanism: nociceptive, neuropathic.

Question 6

Acute vs. chronic pain.

Answer 6

Acute: pain of recent onset and probable limited duration.
Chronic: pain lasting for more than 3 months; pain lasting after normal healing; often no identifiable cause.

Question 7

Cancer vs. non-cancer pain.

Answer 7

Cancer pain: progressive, may be mixture of acute and chronic.
Non-cancer pain: many different causes, acute or chronic.

Question 8

What is nociceptive pain?

Answer 8

Obvious tissue injury or illness.
Also called physiological or inflammatory pain.
Protective function.
Description: sharp ± dull, well localised.

Question 9

What is neuropathic pain?

Answer 9

Nervous system damage or abnormality.
Tissue injury may not be obvious.
Does not have a protective function.
Description: burning, shooting ± numbness, pins and needles, not well localised.

Question 10

What is acute non-cancer pain?

Answer 10

e.g. due to fracture, appendicitis.
Symptom of tissue injury or illness.
Usually nociceptive.
Occasionally neuropathic (e.g. sciatica).

Question 11

What is chronic non-cancer pain?

Answer 11

e.g. chronic back pain, arthritis.
Injury may not be obvious.
Complex, may be mixed nociceptive and neuropathic.
Does not respond to usual drug treatment.

Question 12

What is cancer pain?

Answer 12

e.g. uterine cervical cancer, breast cancer.
Features of acute and chronic pain.
Often mixed nociceptive and neuropathic pain.
Usually gets worse over time if untreated.

Question 13

Hyperalgesia:

a) is associated with normal function of nociceptors
b) is increased pain from a stimulus that normally provokes pain
c) is pain due to a stimulus that does not normally provoke pain
d) is a characteristic feature of nociceptive pain
e) abnormally painful reaction to repetitive stimulus and increased threshold.

Answer 13

Is increased pain from a stimulus that normally provokes pain.

Question 14

What should be the medical professional’s approach to pain?

Answer 14

Recognise: does the patient have pain? do other people know the patient has pain?
Assess: how severe is the pain? what type of pain is it? are there other factors?
Treat: what non-drug treatments can I use? what drug treatments can I use?

Question 15

What is nociception?

Answer 15

How signals get from the site of injury to the brain. Nociception is not the same as pain.

Question 16

What is pain perception?

Answer 16

How we ‘feel’ pain.

Question 17

What factors influence pain perception?

Answer 17

Beliefs/concerns about pain.
Psychological factors: anxiety, anger, depression.
Cultural issues: language, expectations.
Other illnesses.
Coping strategies.
Social factors, e.g. family, work.

Question 18

What are the 4 steps in the physiology of pain?

Answer 18

Periphery: tissue injury; release of chemicals; stimulation of pain receptors (nociceptors); signal travels in A delta or C nerve to spinal cord.
Spinal cord: dorsal horn is the first relay station; A delta or C nerve synapses with second nerve; second nerve travels up opposite side of spinal cord.
Brain: thalamus is the second relay station; connections to many parts of the brain (cortex, limbic system, brainstem); pain perception occurs in the cortex.
Modulation: descending pathway from brain to dorsal horn; usually decreases pain signal.

Question 19

Why is pain physiology important?

Answer 19

Many factors affect how we ‘feel’ pain: psychological factors are very important.
Different treatments work on different parts of the pathway: more than 1 treatment may be needed.

Question 20

What is pain pathology?

Answer 20

Abnormal processing of pain signal.
Nervous system damage or dysfunction.
Needs to be treated differently.
e.g. nerve trauma, diabetic pain (damage); fibromyalgia, chronic tension headache (dysfunction).

Question 21

What are the pathological mechanisms of pain?

Answer 21

Increased receptor numbers.
Abnormal sensitisation of nerves: peripheral or central.
Chemical changes in the dorsal horn.
Loss of normal inhibitory modulation.

Question 22

What are the non-drug treatments for pain?

Answer 22

Physical: rest, ice, compression, elevation; surgery; acupuncture, massage, physiotherapy.
Psychological: explanation; reassurance; counselling.

Question 23

How are pain drugs classified?

Answer 23

Simple analgesics: paracetamol (acetaminophen); anti-inflammatory medicines (diclofenac, ibuprofen).
Opioids: mild (e.g. codeine); strong (e.g. morphine, pethidine, oxycodone).
Tramadol.
TCAs (e.g. amitriptyline). 
Anticonvulsants (e.g. gabapentin).
Ketamine.
Local anaesthetics.
Clonidine.

Question 24

What are the treatments for pain targeting the periphery?

Answer 24

Non-drug treatments: rest, ice, compression, elevation.
Anti-inflammatory medicines.
Local anaesthetics.

Question 25

What are the treatments for pain targeting the spinal cord?

Answer 25

Non-drug treatments: acupuncture, massage.
Local anaesthetics.
Opioids.
Ketamine.

Question 26

What are the treatments for pain targeting the brain?

Answer 26

Non-drug treatments: psychological.

Drug treatments: paracetamol; opioids; amitriptyline; clonidine.

Question 27

What are the advantages and disadvantages of paracetamol (acetaminophen) in treating pain?

Answer 27

Cheap, safe.
Can be given orally, rectally, or IV.
Good for mild pain (by itself) and moderate to severe pain (with other drugs).

Liver damage in overdose.

Question 28

What are the advantages and disadvantages of anti-inflammatory medicines in treating pain?

Answer 28

e.g. aspirin, ibuprofen, diclofenac.
Cheap, generally safe.
Good for nociceptive pain, best given regularly with paracetamol.

GI and renal side effects.

Question 29

What are the advantages and disadvantages of codeine in treating pain?

Answer 29

Cheap, safe.
Good for mild to moderate acute nociceptive pain, best given regularly with paracetamol.

Constipation.
Not good for chronic pain.
Misunderstandings about addiction.

Question 30

What are the advantages and disadvantages of morphine in treating pain?

Answer 30

Cheap, generally safe.
Can be given orally, IV, IM, SC.
Effective if given regularly.
Good for moderate to severe acute nociceptive pain (e.g. post-op pain), and chronic cancer pain.

Constipation.
Respiratory depression in high dose.
Misunderstandings about addiction.
Controlled drug.

Question 31

What are the advantages and disadvantages of pethidine in treating pain?

Answer 31

Can be good for severe acute nociceptive pain, but has more disadvantages than morphine.

Also a controlled drug.
Must be given more frequently than morphine.
Breakdown product (norpethidine) can cause convulsions.
Not good for chronic pain.

Question 32

What are the advantages and disadvantages of tramadol in treating pain?

Answer 32

Weak opioid effect plus inhibitor of serotonin and noradrenaline reuptake (modulation).
Less respiratory depression.
Can be used with opioids and simple analgesics.
Not a controlled drug.

Nausea and vomiting.

Question 33

What are the advantages and disadvantages of amitriptyline in treating pain?

Answer 33

TCA.
Increases descending inhibitory signals.
Cheap, safe in low dose.
Good for neuropathic pain.
Also treats depression, poor sleep.

Anti-cholinergic side effects, e.g. glaucoma, urinary retention.

Question 34

What are the advantages and disadvantages of anticonvulsant drugs in treating pain?

Answer 34

e.g. carbamazepine (tegretol), sodium valproate (epilim), gabapentin (neurontin).
Also called membrane stabilisers: reduce abnormal firing of nerves.
Good for neuropathic pain.

Question 35

Nociceptors may respond to:

a) noxious stimuli
b) pressure
c) heat
d) cold
e) all are true

Answer 35

All are true.

Question 36

Morphine dosage:

a) 400mg every 8hrs for severe pain
b) 1000mg every 4-8hrs
c) max daily dose is 500mg
d) 10mg every 1-2hrs in moderate to severe pain
e) elderly patients may require higher doses

Answer 36

10mg every 1-2hrs in moderate to severe pain.

Question 37

With regards to the WHO pain relief ladder:

a) it is specific for the management of acute pain
b) paracetamol and codeine are first line
c) useful for the management of chronic non-cancer pain
d) morphine is reserved as a second line treatment
e) all are false

Answer 37

All are false.

Question 38

Side effects for NSAIDS:

a) gastric ulcers
b) reduced renal perfusion
c) exacerbation of asthma
d) coagulation impairment
e) all are true

Answer 38

All are true.

Question 39

Nociception:

a) signals travel via A delta or C fibres
b) low threshold is required for activation
c) the stimulus terminates in the spinal cord
d) is a response to a non-noxious stimulus
e) typically involves a single neurotransmitter

Answer 39

Signals travel via A delta or C fibres.

Question 40

Pain and temperature pathways cross over in the:

a) medulla
b) thalamus
c) spinal cord
d) ventrobasal complex
e) all are false

Answer 40

Spinal cord.

Question 41

Which area is involved in pain perception?

a) brainstem
b) somatosensory cortex
c) limbic system
d) insula
e) all are true

Answer 41

All are true.

Question 42

Descending modulation:

a) the process is always active
b) the brainstem is a key structure
c) usually decreases the pain signal
d) loss of inhibition may result in hypersensitivity
e) all are true

Answer 42

All are true.

Question 43

Neuropathic pain is typically characterised by:

a) less peripheral nociceptors
b) peripheral or central sensitisation
c) more descending inhibition acting on the spinal cord
d) hypoalgesia
e) all are true

Answer 43

Peripheral or central sensitisation.

Question 44

The following pains are typically neuropathic:

a) phantom limb pain
b) complex regional pain syndrome
c) pain with diabetic neuropathy
d) radicular lower back pain
e) all are true

Answer 44

All are true.

Question 45

For acute back pain, GPs should:

a) refer to a pain management unit
b) refer to a physiotherapist
c) refer to a spinal surgeon
d) reassure the patient and advise bed rest
e) follow the WHO ladder approach

Answer 45

Refer to a physiotherapist.

Question 46

Allodynia is:

a) diminished pain in response to a normally painful stimulus
b) increased pain from a stimulus that normally provokes pain
c) pain due to a stimulus that does not normally provoke pain
d) abnormal sensation, whether spontaneous or provoked
e) all are false

Answer 46

Pain due to a stimulus that does not normally provoke pain.