MISC - Pain management

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”.

Question 2

(3) types of Classification of Pain

Answer 2

1. Duration
   - Acute
   - Chronic
   - Acute on chronic
2. Cause
   - Cancer (progressive)
   - Non cancer
3. Mechanism
   - Nociceptive (physiological)
   - Neuropathic (pathological)

Question 3

What is a chronic pain?

Answer 3

– Pain persisting beyond healing of injury

– Often no identifiable cause

– (Pain lasting for more than 3 months)

Question 4

Describe nociceptive pain

Answer 4

• Obvious tissue injury or illness
• “Physiological pain”

• Can be further classified into
– Superficial somatic
– Deep somatic
– Visceral

• Descriptions include sharp, aching, dull, throbbing, cramping and pressure

Question 5

Describe neuropathic pain

Answer 5

• Nervous system damage or abnormality
• “Pathological pain”
• Tissue injury may not be obvious

• Description
– Burning, shooting ± numbness, pins and needles
– Not well localised

Question 6

How is nociception not the same as pain?

Answer 6

Pain is multifactorial not only injury based.

Factors include: beliefs/concerns, psychological factors (anxiety, depression, anger), cultural issues, other illnesses, coping strategies, social factors.

Question 7

What are the 4 steps of pain physiology (sequence)?

Answer 7

– Periphery

– Spinal cord

– Brain

– Modulation

Question 8

What happens at the periphery as one of the 4 steps of pain physiology?

Answer 8

• Tissue injury
• Release of chemicals
• Stimulation of pain receptors (nociceptors)
• Signal travels in Aδ or C nerve to spinal cord

Question 9

What happens at the spinal cord as one of the 4 steps of pain physiology?

Answer 9

• Dorsal horn is the “first relay station”
• Aδ or C nerve synapses (connects) with second nerve
• Second nerve travels up OPPOSITE side of spinal cord (decussate at the level of spinal cord)

Question 10

What happens at the brain as one of the 4 steps of pain physiology?

Answer 10

• Thalamus is the “second relay station”

• Connections to many parts of the brain
– Cortex
– Limbic system
– Brainstem

• Pain perception occurs in the cortex

Question 11

What happens during modulation as one of the 4 steps of pain physiology?

Answer 11

• Descending pathway from brain to dorsal horn

* Usually decreases pain signal

Question 12

What is the “second relay station” for pain?

Answer 12

Thalamus

Question 13

What is the “first relay station” for pain?

Answer 13

Dorsal horn

Question 14

Compare peripheral vs. central neuropathic pain

Answer 14

• Peripheral
– Damaged nerves (e.g. trauma, diabetes)
– Abnormal firing of nerves

• Central
– Changes in “wiring”
– Abnormal firing
– Loss of modulation

Question 15

List (6) medications used for analgesia

Answer 15

Paracetamol (Acetaminophen)
NSAIDs
Opioids
Tramadol
Amitriptyline
Anti-epileptic drugs

Question 16

Describe paracetamol as an analgesic

• mechanism of action
• indications
• SE
• drug interactions
• monitoring

Answer 16

• Mechanism of action
– Unclear but acts in CNS
– Inhibits peripheral prostaglandin synthesis
– Analgesic and antipyretic

• Indications
– Analgesia either alone or in combination

• Adverse effects
– Hepatic necrosis

• Drug interactions
– Effects are additive with NSAIDs

• Monitoring
– Safe dose is up to 4 g per day in adult

Question 17

Describe NSAID as an analgesic

• mechanism of action
• indications
• SE
• drug interactions
• monitoring

Answer 17

• Mechanism of action
– Non specific inhibition of COX1 & 2 to inhibit PG synthesis
– Analgesic, antipyretic, anti-inflammatory

• Indications
– Analgesia alone or in combinations

• Adverse effects 
– Peptic ulceration
– Renal impairment
– Anti platelet action
– Bronchospasm in asthmatics
– Exacerbation of CCF

• Drug interactions
– Reduce opioid requirements by 20-40%

• Monitoring
– Care with renal impairment or hypvolaemia

Question 18

Describe opioids as an analgesic

• mechanism of action
• indications
• SE
• drug interactions
• monitoring

Answer 18

• Mechanism of action
– Mu opioid receptors to produce analgesia
– Site of action is the peripheral nociceptors, dorsal horn, cerebral cortex and descending tracts

• Indications
– Severe pain

• Adverse effects
– Sedation, respiratory depression
– Nausea, euphoria, miosis, bradycardia, postural hypotension, urinary retention

• Drug interactions
– Other sedative agents

• Monitoring
– Sedation, CV and respiratory

Question 19

Describe tramadol as an analgesic

• mechanism of action
• (+)
• (-)

Answer 19

• Weak opioid effect plus inhibitor of serotonin and noradrenaline reuptake (modulation) -> hence do NOT use with SSRI/SNRI.

• Advantages
– Less respiratory depression
– Can be used with opioids and simple analgesics
– Not a controlled drug

• Disadvantages
– Nausea and vomiting

Question 20

Describe amitriptyline as an analgesic

• mechanism of action
• (+)
• (-)

Answer 20

• Increases descending inhibitory signals

• Advantages
– Cheap, safe in low dose
– Good for neuropathic pain
– Also treats depression, poor sleep

• Disadvantages
– Anti-cholinergic side effects (glaucoma, urinary retention)

Question 21

Describe anti-epileptic drugs as an analgesic

• examples
• mechanism of action
• indications

Answer 21

• Carbamazepine (Tegretol)
• Sodium valproate (Epilim)
• Gabapentin/Pregabalin

• “Membrane stabilisers”
– Reduce abnormal firing of nerves

• Good for neuropathic pain

Question 22

What is The RAT Approach to Pain Management?

Answer 22

• Recognize (does the pt have pain?)
• Assess
• Treat (non pharm & pharm)

Question 23

How do you assess pain?

Answer 23

• Measure the severity
– What is the pain score?
• At rest
• With movement

– How is the pain affecting the patient?
• Can the patient move, cough?
• Can the patient work?

Measurement of severity: verbal (mild, moderate, severe), numerical, visual

Question 24

How do you treat pain non-pharmacologically?

Answer 24

Non-Drug Treatments
– RICE:  Rest, ice, compression, elevation of injuries – Nursing care, physiotherapy
– Surgery, acupuncture, massage, TENS 
– Psychological
• Explanation and reassurance
• Input from social worker / pastor
• Relaxation, imagery, distraction
• Coping strategies

Question 25

How do you treat mild nociceptive pain pharmacologically?

Answer 25

• Paracetamol (± NSAID)

Question 26

How do you treat moderate nociceptive pain pharmacologically?

Answer 26

• Paracetamol (± NSAID) + codeine/oxycodone/tramadol

Question 27

How do you treat severe nociceptive pain pharmacologically?

Answer 27

* Paracetamol (± NSAID) + morphine/oxycodone * Regional anaesthesia * Adjuvants (alpha 2 agonists, NMDA antagoinists)

Question 28

How do you treat neuropathic pain pharmacologically?

Answer 28

``` – Traditional drugs may not be as useful – Use other drugs early • Amitriptyline • Carbamazepine • Gabapentinoids ``` Don’t forget non-drug treatments

Question 29

Which sites are you targeting in multimodal drug treatment?

Answer 29

Peripheral nociceptors Peripheral nerves (A-delta, C) Dorsal root ganglia Dorsal Horn Ascending tracts Cortex Descending inhibitory modulation