Essential pain management Flashcards
What is pain?
Pain is “an unpleasant sensory and emotional experience associated with or resembling that associated with actual or potential tissue damage, or described in terms of such damage”
or something
What are the benefits of treatment to patients with pain?
Improved sleep
Better appetite
Fewer medical complications - eg MI, pneumonia
Also psychological factors - reduced suffering can improve/eliminate anxiety, depression
What are the different ways we can classify pain?
by Duration:
- acute
- chronic
- acute on chronic
by Cause:
- cancer
- non-cancer
by Mechanism (most useful):
- nociceptive
- neuropathic
What is the difference between nociceptive and neuropathic pain?
Nociceptive pain typically changes with movement, position, and load. Neuropathic pain arises from damage to the nervous system itself, central or peripheral, either from disease, injury, or pinching
What is the difference between acute and chronic pain?
Acute - pain of recent onset and probable limited duration
Chronic - pain >3 months & pain lasting after normal healing
What is nociceptive pain?
Pain due to obvious tissue injury or illness
Also called physiological or inflammatory pain
Nociceptive pain serves a protective function and gives well localised pain that can be described easily (sharp or dull)
Describe the features of neuropathic pain?
Due to nervous system damage / abnormality
Does not serve a protective function
Neuropathic pain is often described as:
- Burning, shooting +/- numbness, pins & needles etc
- Not well localised
What are the 4 physiological stages in our perception of pain?
Periphery
Spinal cord
Brain
Modulation (descending pathway)
What happens peripherally when a painful thingy happens?
Tissue injury causes local release of chemicals such as:
- Prostaglandins
- Substance P
These chemicals stimulate nociceptive afferents (pain receptors)
Signals from this travel up in A’delta’ and C fibres into spinal cord via dorsal root ganglion & horn
Following a tissue injury, how do nociceptive signals enter the spinal cord?
What do they do once they have reached it?
Pain signals on A’delta’ and C fibres enter via dorsal horn
The dorsal horn serves as the first relay station - as this is where they synapse with the 2nd nerve which goes up the spinal cord (usually in the Spinothalamic tract) on the opposite side
What happens once a pain signal has reached the brain?
Afferent travelling up the spinothalamic tract (or other ascending pathway) witll then synapse in the thalamus
The thalamus serves as the 2nd relay station for pain signals
The thalamus communicates with many areas (cortex, limbic system, brainstem) - however - perception of pain happens in the cortex
What is modulation?
Modulation involves inhibitory signals sent from the brainstem to the dorsal horn (a descending pathway)
This acts to decrease the pain signal coming from the site of tissue injury
What is gate theory of pain?
To do with modulation
Basically - rubbing, heating a site of tissue injury stimulates production of inhibitory neurones that basically reduces the pain signal that goes to the brain
Describe the pathological mechanisms behind neuropathic pain
Increased receptor numbers
Abnormal sensitisation of nerves - both peripherally and centrally
Chemical changes in the dorsal horn
*^all the above serve to enhance pain signals^*
Loss of normal inhibitory modulation
What are the groups of analgesics used for the treatment of pain?
Simple analgesics:
- Paracetamol, NSAIDs etc
Opioids:
- WEAK - codeine, dihydrocodeine, tramadol
- STRONG - morphine, oxycodone, fentanyl
Others (next slide)
Aside from simple analgesics and opioids - what other analgesics are there?
Tramadol - mixed opiate & 5HT/NA reuptake inhibitor
Antidepressants - eg amitriptyline, duloxetine
Anticonvulsants - eg gabapentin
Ketamine - “nice”
Local anaesthetics
Topicals - eg capsaicin
Give some examples of NSAIDs
What are their advantages?
” disadvantages?
Ibuprofen, aspirin, diclofenac (Voltaren)
Advantages:
- Cheap, generally safe
- Good for nociceptive pain
- Work well alongside paracetamol (synergism)
Disadvantages:
- GI & renal side effects (reduces renal blood flow)
- contraindications^
- Bronchospasm in asthmatic patients
What are the advantages and siadvantages of codeine?
Advantages:
- Cheap, safe
- Good for mild/moderate acute nociceptive pain
- best given regularly with paracetamol
Disadvantages:
- Constipation
- Not good for neuropathic pain
What is Tramadol and what are its advantages & disadvantages?
Weak opioid effect plus inhibitor of serotonin and noradrenaline reuptake (modulation)
Advantages:
- Less respiratory depression
- Less constipating than other opioids
- Can be used w/ other opioids & analgesics
Disadvantages:
- Often causes N&V, esp at high doses
- Controlled drug so bloody difficult to prescribe
What are the uses, advantages and disadvantages of morphine?
Morphine is effective for:
- cancer pain (nociceptive)
- mod/severe nociceptive pain - eg post op
- esp if given regularly
Advantages of morphine:
- cheap, generally safe
- can be given via pretty much any route
Disadvantages of morphine:
- constipation
- respiratory depression in high doses
- addiction!
- controlled drug
If a patient is on IV/IM morphine but you/they wish to change to oral route - how is dosing affected?
WHAY?
Oral dose needs to be increased if changing from IV/ IM or S/C routes as third pass metabolism reduces the amount of morphine available
What is amitriptyline and how does it work?
Tricyclic antidepressant (TCA)
Increases descending inhibitory signals (modulation)
What are the advantages and disadvantages of amitriptyline
Advantages:
- cheap, safe in low doses
- good for neuropathic pain
- also treats depression, improves sleep
Disadvantages:
- anti-cholinergic side effects
- glaucoma
- urinary retention
- long term use may be linked to cognitive decline and dementia
What are some examples of anti-convulsants?
How do they work?
What type of pain are they good for?
Carbamazepine
Sodium valproate
Gabapentin
Anticonvulsants work by reducing the abnormal firing of nerves (theyre aka membrane stabilisers)
Good for neuropathic pain
In what different ways can pain be assessed?
Verbal rating score
Numerical rating score
Visual analogue scale
Smiling faces
Abbey pain scale (for confused patients, dementia)
Functional assessments
What are some non-drug ways of treating the physical and psychological aspects of pain?
Physical:
- rest, ice, elevation
- surgery
- acupuncture, massage, physiotherapy
Psychological:
- explanation
- reassurance
- counselling
How do we treat nociceptive pain?
(what resource determines this?)
Refer to WHO pain ladder
Mild pain:
- simple analgesics; paracetamol, NSAIDs
Moderate pain:
- mild opioids (eg codeine) +/- simple analgesics
Severe pain:
- strong opioids (eg morphine) +/- simple analgesics
For very severe & unbearable pain - it is okay to start at the top of the ladder (severe treatment)
What is the approach to changing/stopping analgesia as a patient’s pain resolves?
(for a patient receiving treatment for severe pain)
Move from top to middle of WHO ladder
Continue Bottom Rung drugs at all times
When stopping bottom rung drugs - stop NSAIDs first and then paracetamol as NSAIDs have the more adverse effects when stopped
What is the RAT approach to managing pain?
Recognize, Assess, Treat
Recognize
Assess:
- severity?
- type?
- other factors? - eg are they already on analgesics
Treat:
- drug / non-drug treatment based on assessment^
How would you treat patients with neuropathic pain?
WHO pain ladder not applicable (usually)
Use other drugs early (that are good for neuropathic pain:
- amitriptyline
- gabapentin
- duloxetine
Non-drug treatment is also very important for neuropathic pain
