Anaesthetics - pain Flashcards
- Describe the reasons why pain should be treated and the consequences of not doing.
- Describe the differences between the different types of pain that a patient may experience and describe how each may best be managed.
- Give an outline of the different therapies available for the management of pain.
- Describe the practicalities involved in the delivery of pain relief in the clinical setting.
- Discuss the role of scoring systems in the practical delivery of analgesia.
- Understand the differences between acute and chronic pain states.
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Common analgesic drugs and their modes of action.
‘Gate theory’ of pain transmission.
Measuring pain, objective methods and scoring.
Various analgesic strategies will be discussed.
Reasons for treating pain
- physical (3)
- psychological (3)
- family (1)
Better sleep, appetite
Fewer complications
Less suffering, depression, anxiety
Able to keep working and provide for the family
3 types of pain classified by duration
Acute
Chronic (>3 months)
Acute on chronic
Mechanism of pain is usually either … or …
Nociceptive or neuropathic
Differences between nociceptive (4) and neuropathic pain (6)
Nociceptive (obvious tissue injury or illness)
- protective function
- sharp, dull, well localised
Neuropathic (nervous system damage)
- no protective function
- burning, shooting, numb, pins + needles
- not well localised
Describe how pain is transmitted (i.e. describe the pain pathway up to the brain)
- periphery
- spinal cord
- brain
Nociceptors and stimulated and peripheral Aδ or C nerves then carry the signal to the dorsal horn
Aδ or C nerve synapses with 2 second nerve (2nd order neuron) at the point of entry and that nerve then crosses over and travels up the lateral spinothalamic tract
2nd order neuron synapses in the thalamus (sensory relay station) then the 3rd order neurone relays it to primary somatosensory cortex in the post-central gyrus
What is the theory called that describes how pain can be modulated
Gate theory - activity in the larger fibres (Aα/β) [touch, pressure pathway) can excite inhibitory neurons in the final cord which can release endorphins onto the 1st order neurons of the nociceptive pathway, thereby inhibiting the signal from being transmitted to the 2nd order neuron, so ‘CLOSING THE GATE’
(this explains why rubbing the sore area alleviates the pain)
Examples of neuropathic pain
Nerve trauma
Diabetic nerve damage
Fibromyalgia
Tension headache
List the different drug types available for the management of pain
- simple analgesics (2)
- opioids (2)
- others (6)
Simple
- paracetamol
- NSAIDs (ibuprofen, diclofenac)
Opioids
- codeine, dihydrocodeine (mild)
- morphine, oxycodone (strong)
Others
- tramadol
- antidepressants
- anticonvulsants
- ketamine
- LA
- topical agents, e.g. capsaicin
Treatments of pain at periphery
- non-drug (4)
- drug (2)
Non-drug
-rest, ice, compression, elevation (‘RICE’)
Drug
- NSAIDs
- LA
Treatments of pain at spinal cord level
- non-drug (3)
- drug (3)
Non-drug
-acupuncture, massage, TENS
Drug
- LA - infuse into spinal or epidural space
- Opioids
- Ketamine
Treatments of pain at brain level
- non-drug (1)
- drug (4)
Non-drug
-psychotherapy, e.g. CBT
Drug
- paracetamol
- opioids
- amitriptyline (TCA)
- clonidine (antihypertensice/ADHD drug)
Paracetamol is cheap, safe, can be given orally/rectally/IV
Good for mild pain or mod-severe pain (with other drugs)
What is a disadvantage of paracetamol?
Liver damage in overdose (hepatotoxic)
NSAIDs (aspirin, ibuprofen, diclofenac) are cheap, generally safe, good for NOCICEPTIVE pain (best given regularly with paracetamol)
What is a disadvantage/side effect of NSAIDs?
GI - gastric pain, indigestion, gastric ulcers
Headaches + dizziness
Renal impairment
Bronchospasm in sensitive asthmatics
Codeine (a milder opioid) is good for ACUTE nociceptive pain (not good for chronic pain)
What is a disadvantage/side effect?
Constipation
