Week 4 - G - Management of chronic pain

Question 1

What is the IASP (International Association for the Study of Pain) definition of pain?

Answer 1

An unpleasant sensory and emotional experience, associated with actual tissue damage or described in terms of such damage

Question 2

Pain can be thought of as acute or chronic Does acute or chronic pain serve a protective function? ie as an alarm system for sensing tissue damage

Answer 2

Acute pain serves a protective function to alert the person to tissue damage Chronic pain no longer has this protective function

Question 3

Patients can be asked to estimate a measure of their pain Ie verbal rating scale - mild, moderate, severe Number rating scale ie 0-10 Is estimating a measure of pain accurate for the intensity?

Answer 3

As pain is subjective to the person, estimating the level of pain may not always prove most accurate

Question 4

What are the two types of nerve fibre that carry the pain sensation?

Answer 4

Aδ fibres and C fibres (unmyelinated)

Question 5

What is the difference between nociceptive and neuropathic pain?

Answer 5

Nociceptive pain is a physiological response to a painful stimuli via an intact nervous system Neyropathic pain - an inappropriate response caused by a dysfunction in the nerves

Question 6

What are the symptoms of nociceptive vs neuropathic pain described as?

Answer 6

Nociceptive pain - sharp, sabbing, Neuropathic pain - chronic pain which can also be associated with numbness, burning and shooting pain also

Question 7

As said neuropathic pain can present as a burning, shooting or increased sensitivity What are the following symptoms known as: pain from a stimulus that is not normally painful, eg. Cotton wool ? more pain than expected from a painful stimulus, eg. Pin prick ?

Answer 7

Allodynia - pain from a stimulus that is not normally painful, eg. Cotton wool Hyperalgesia -more pain than expected from a painful stimulus, eg. Pin prick Both of thse are symptoms of neuropathic and not nociceptive pain

Question 8

What are common causes of neuropathic pain?

Answer 8

Shingles - post herpetic neuralgia Diabetic nuropathy Surgery Neurological diseases eg multiple sclerosis

Question 9

What is WHOs analgesic ladder for pain in cancer patients - also widely used for non cancer patients as well Describe all three steps

Answer 9

Step 1 - Non-opioid (eg paracetamol or aspirin or NSAID) +/- adjuvant Step 2 - Weak opioid (eg codeine) +/- Non opioid, +/- Aduvant Step 3 - Strong opioid (eg morphine) +/- non-opioid, +/- Adjuvant

Question 10

Give examples of adjuvants used in the WHO analgesic ladder (eg for antidepressants, anticonvulsants and topical analgesics)

Answer 10

Antidepressants - tricyclics eg amitriptyine or SNRIs (serotonin-noradrenaline reuptake inhibitors - eg duloxetine) Anticonvulsants - gabapentin and pregablin Topical analgesics - capsaicin and lidocaine

Question 11

How to the NSAIDs work? Name 2? What type of pain are they mainly used in? What are some side effects?

Answer 11

They inhibit the cyclooxygenase (COX) enzyme preventing prostoglandin synthesis Aspirin and ibuprofen Mainly used in nociceptive pain They cause : GI bleeding Renal toxicity & Cardiovascular side effects also - must be used with caution in older patients with impaired renal function and heart failure1

Question 12

Which non-opioid is hepatotoxic at high doses? It is an aniline derivative and widely used as an analgesic and antipyretic What does this drug inhibit?

Answer 12

This is paracetamol - aniline derivative It works by centrally inhibiting the prostoglandin pathways although the full mechanism of action is not completely understood Mainly in nociceptive pain

Question 13

What is used to treat the side effects of an overdose of paracetamol?

Answer 13

N-acetylcysteine - meant to be 100% effective if prescribed within 8 hours of the patient overdosing on paracetamol - after this the efficacy greatly decreases

Question 14

Opioids act mainly on the central nervous system. They are predominantly agonists of morphine (mu) receptors, which are present in the brain and spinal cord. What type of pain are they used in mainly? What are the side effects?

Answer 14

Mainly used in nociceptive pain Can cause vomiting, constipation, sedation, dry skin

Question 15

What type of pain are anti-depressants typically used in?

Answer 15

Ani depressants are typically used in neuropathic pain and not nociceptive pain

Question 16

Name three types of drugs that can be used to treat neuropathic pain? (ie 2antidepressant groups and one other type of drug)

Answer 16

Tricylic antidepressants, Serotonin-noradrenaline reuptake inhibitors (SNRIs) Anti-convulsants

Question 17

What do trcicylics inhibt the reuptake off? What are side effects associated with tricylics?

Answer 17

They inhibit the neuronal uptake of noradrenaline and serotonin (5HT) Side effects include, drowsiness, constipation, dry mouth , increased appetite

Question 18

SNRIs are better tolerated than TCAs but may only have moderate efficacy in pain management Name two SNRIs?

Answer 18

Duloxetine and venlafaxine

Question 19

Name 3 anticonvulsants? Which type of pain are they first line in?

Answer 19

Carbamezapine Pregablin Gabapentin Carbamezapine is first line in trigeminal pain Offer a choice of amitriptyline, duloxetine, gabapentin or pregabalin as initial treatment for neuropathic pain (except trigeminal neuralgia)

Question 20

The side effects of anti-convulsants include sedation, nausea, ataxia and weight gain How do gabapentin, pregablin and carbamezapine work?

Answer 20

Gabapentin - binds to presynaptic voltage gated calcium channels reducing release of transmitters Pregabalin - interacts with special N-type calcium channels Carbamezapine - Blocks sodium and calcium channels

Question 21

Run through how the three anti-convulsants work again? Which is assoictaed with the most side effects?

Answer 21

Gabapentin - Binds to the presynaptic voltage activated calcium channels Pregabalin - Interacts with special N-type calcium channels Carbamezapine - Blocks sodium and calcium channels Carbamezapine is associated with most side effects out of the three drugs

Question 22

Topical analgesics reduce pain impulses transmitted by which nerve fibres?

Answer 22

They reduce the pain impulses transmitted by Adelta and C fibres

Question 23

What are the usual side effects of topical analgesics??

Answer 23

Rash, pruritus and erythema local to the site of application are the main side effects

Question 24

What is the definition of pain by the IASP?

Answer 24

An unpleasant sensory and emotional response associated with actual tissue damage or described in terms of such damage

Question 25

The fact that the administration of placebos significantly reduces pain by up to 20% shows that the psychic constitution has a great effect on pain perception. What is a psychological treatment for pain?

Answer 25

This would be cognitive behavioural therapy (CBT)

Question 26

Chronic pain is multifaceted and involves the interaction of physical, psychological and social factors The biopsychosocial model of pain acknowledges the interplay of these factors and is an important model to guide understanding, assessment and management of chronic pain What artery supplies the sensory innervation to legss? WHich supplies sensory innervation to hands and face?

Answer 26

Anterior cerebral artery supplies the legs and trunk Middle cerebral artery supplies the hands + face

Question 27

In a hand amputee, does the area for the sensory innervation of the hand go silent?

Answer 27

No instead, the face utilises the region left by the missing hand and that is why when the face is touched, stimulation is often felt in the hand in an amputee