Pain Management

Question 1

What are the 3 main questions to ask when classifying pain?

Answer 1

How long has the patient had pain? Acute, chronic or acute on chronic

What is the cause? Cancer or non-cancer

What is the pain mechanism? Nociceptive (physiological) or neuropathic (pathological)

Question 2

Distinguish between acute and chronic pain

Answer 2

Acute: pain of recent onset and probable limited duration

Chronic: pain persisting beyond healing of injury, often no identifiable cause, lasting >3/12

Question 3

Distinguish between cancer and non-cancer pain

Answer 3

Cancer pain: progressive, may be mixture of acute and chronic

Non-cancer pain: many different causes, can be acute or chronic

Question 4

What is the mechanism of nociceptive pain and how can it be further classified?

Answer 4

Obvious tissue injury or illness (“physiological pain”)

Can be further classified into superficial somatic, deep somatic or visceral

Question 5

Give a clinical description of nociceptive pain

Answer 5

Can be sharp, aching, dull, throbbing, cramping, pressure, etc

Question 6

What is the mechanism of neuropathic pain?

Answer 6

Nervous system damage or abnormality (“pathological pain”); tissue injury may not be obvious

Question 7

Give a clinical description of neuropathic pain

Answer 7

Burning, shooting +/- numbness, parasthesia

Not well localised

Question 9

What are the 4 steps in the physiology of pain?

Answer 9

Periphery: tissue injury results in release of chemicals which stimulate nociceptors and result in propagation of signal in A-delta or C nerve to spinal cord

Spinal cord: dorsal horn is the “first relay station” where the A-delta or C nerve synapses (connects) with the second nerve, and the second nerve travels up the opposite side of the spinal cord

Brain: thalamus is the “second relay station” with connections to many parts of the brain including the cortex, limbic system and brainstem (pain perception occurs in the cortex)

Modulation: descending pathway from brain to dorsal horn, typically decreases the pain signal

Question 10

Where is the abnormality in neuropathic pain?

Answer 10

Peripheral nerves

Spinal cord or brain

Question 11

What peripheral or central changes can result in neuropathic pain?

Answer 11

Peripheral: damaged nerves (e.g. trauma, DM), abnormal firing of nerves

Central: changes in “wiring”, abnormal firing, loss of modulation

Sensitisation can occur in peripheral and central nervous system; persistent central sensitisation is a possibe mechanism for some chronic pain conditions

Question 12

What is the mechanism of action of paracetamol (acetaminophen)?

Answer 12

Unclear but acts in CNS

Inhibits peripheral prostaglandin synthesis

Analgesic and antipyretic

Question 13

What are the indications for paracetamol?

Answer 13

Analgesia either alone or in combination

Question 14

What is the main AE of paracetamol?

Answer 14

Hepatic necrosis

Question 16

Describe important drug interactions of paracetamol with other pain medications

Answer 16

Effects are additive with NSAIDs

Question 17

What monitoring is indicated for paracetamol?

Question 19

What is the mechanism of action of NSAIDs?

Answer 19

Non-specific inhibition of COX1 and COX2 to inhibit PG synthesis

Analgesic, antipyretic, anti-inflammatory

Question 20

What is the indication for NSAIDs?

Answer 20

Analgesia alone or in combination

Question 21

List 5 adverse effects of NSAIDs

Answer 21

Peptic ulceration

Renal impairment

Anti-platelet action

Bronchospasm in asthmatics

Exacerbation of CCF

Question 22

Name one drug interaction of NSAIDs with other analgesics

Answer 22

Reduce opioid requirements by 20-40%

Question 23

What monitoring considerations are important with NSAIDs?

Answer 23

Care with renal impairment or hypovolaemia

Question 24

What is the mechanism of action of opioids?

Question 25

What are the indications for opioids?

Answer 25

Severe pain

Question 26

List 8 AEs of opioids

Answer 26

Sedation Respiratory depression Nausea Euphoria Miosis Bradycardia Postural hypotension Urinary retention

Question 27

What drug interactions occur with the use of opioids for analgesia?

Answer 27

Interacts with other sedative agents

Question 28

What kind of monitoring is important with use of opioid analgesics?

Answer 28

Sedation, CV and respiratory

Question 29

What is the mechanism of action of tramadol?

Answer 29

Weak opioid effect plus inhibitor of serotonin and noradrenaline reuptake (modulation)

Question 30

List 3 advantages and one disadvantage of tramadol

Answer 30

Advantages: less respiratory depression, can be used with opioids and simple analgesics, not a controlled drug Disadvantages: N+V

Question 31

What is the mechanism of action of amitriptyline as an analgesic?

Answer 31

Increases descending inhibitory signals (tricyclic antidepressant)

Question 32

Outline 3 advantages and one disadvantage of amitriptyline for analgesia

Answer 32

Advantages: cheap, safe in low dose, good for neuropathic pain, also treats depression and poor sleep Disadvantages: anti-cholinergic side effects (glaucoma, urinary retention)

Question 33

What drugs can be used for neuropathic pain Mx?

Answer 33

Amitriptyline Anti-epileptics: carbamazepine, sodium valproate, gabapentin/pregabalin

Question 34

Tegretol

Answer 34

Carbamazepine

Question 35

Epilim

Answer 35

Sodium valproate

Question 36

What is the mechanism of anti-epileptics as analgesics?

Answer 36

"Membrane stabilisers"; reduce abnormal firing of nerves

Question 37

Summarise commonly used analgesics and the types of pain they are best for

Answer 37

Question 38

What is the RAT approach to pain?

Answer 38

Recognise Assess Treat

Question 39

What methods are commonly used for pain measurement?

Answer 39

Verbal (e.g. mild, moderate, severe) Numerical (0 to 10) Visual (VAS, "faces" pain scale)

Question 40

What non-drug treatments can be used to manage pain?

Answer 40

RICE Nursing care, physiotherapy Surgery, acupuncture, massage, TENS Psychological (explanation and reassurance, input from SW/pastor, relaxation, imagery, distraction, coping strategies)

Question 41

Describe the types of drug treatments commonly used for mild, moderate and severe nociceptive pain

Answer 41

Mild: paracetamol (+/- NSAID) Moderate: paracetamol (+/- NSAID) + codeine/oxycodone/tramadol Severe: paracetamol (+/- NSAID) + morphine/oxycodone, regional anaesthesia, adjuvants (alpha 2 agonists, NMDA agonists)

Question 42

How should neuropathic pain be treated?

Answer 42

Traditional drugs may not be as useful Use other drugs early: amitriptyline, carbamazepine, gabapentinoids Don't forget non-drug treatments!