Anaesthetics Pain management Flashcards
What characteristics do we use to categorise pain?
Duration
Cause
Mechanism
When does acute pain become chronic?
IF it lasts for >3 months, after normal healing and/or has no identifiable cause
Pain can also be acute-on-chronic
What are the mechanisms of pain?
Nociceptive:
- Obvious injury
- Sharp or dull
- well localised
Neuropathic:
- Nerve damage or NS dysfunction
- Burning, shooting, numbess or Pins/needles
- Not well localised
What types of analgesics do we have?
Simple analgesics (PCM &NSAIDS)
Opiods
Others
What are the pros and cons of paracetamol /NSAIDs
- Cheap and safe.
- PCM can be given orally, rectally or IV
- PCM can lead to liver damage if overdose is given
- NSAIDs are synergistic with PCM but come with GI, renal and asthmatic side effects
Give an example of mild and strong opioids?
Mild - Codeine or Dihydrocodeine
Strong - Morphine/ hydrocodone
Opioids can be compined with PCM and are mostly cheap and safe. What are their cons?
Constipation
Respiratory depression (mostly stronger ones)
Not good for chronic pain
Strong opioids are controlled so can be practically more difficult to deliver
What’s included in the “Other analgesics” category?
- Tramadol
- TriCyclic Antidepressant e.g. Amitriptyline
- Anti-convulsants e.g. Gabapentin or NaValproate
- Ketamine
- LA
- Topical agents e.g. Capsaicin cream
How do TCAs help with pain?
Increase modulatory effect of desc inhibitory pathways.
This makes them good for neuropathic pain
They also help with sleep problems and depression
How do Anti-convulsants help with pain?
Reduce abnormal firing of nerves which is good for neuropathic pain
How do we treat pain non-pharmacologically?
RICE
Acupuncture & massage
TENS
Explanantion, reassurance and counselling can make a huge amount of difference, patients knowing the pain is expected, normal and where applicable temporary can handle it much better
How do we treat nociceptive pain?
Follow the WHO analgesic ladder:
Mild - Simple analgesics
Moderate - Mild opioids + Simple analgesics
Severe - Strong opioids + simple analgesics
How do we wean people off analgesics?
Go back down the WHO analgesic ladder in steps.
Stop PCM last (as it has the least side effects)
How do we treat neuropathic pain?
Start non-pharmacologically
Then try alternative analgesics such as Amitriptyline, Gabapentin and duloxetine
What is the RAT approach to pain relief?
Recognize
Assess (severity, cause, type and other factors)
Treat
How do we assess the severity of pain?
1) verbal rating (mild –> severe)
2) Numerical scale (1 –> 10)
3) Visual analogue scale
4) Faces
5) Abbey pain scale
How does a visual analogue scale work?
Draw a line and ask patients to mark along the line where their pain sits
What is an abbey pain scale for?
Confused patients
what is noci-receptive pain also known as?
- Physiological
- Inflammatory
examples of neuropathic pain?
nerve trauma, diabetic pain (damage)
Fibromyalgia, chronic tension headache (dysfunction)
4 steps in pain
– Periphery
– Spinal cord
– Brain
– Modulation
peripheral pain
- Tissue injury
- Release of chemicals e.g. Prostaglandins, Substance P
- Stimulation of pain receptors (nociceptors)
- Signal travels in Aδ or C nerve to spinal cord
Spinal cord pain
- 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
Brain pain
•Thalamus is the second relay station •Connections to many parts of the brain o Cortex o Limbic system o Brainstem •Pain perception occurs in the cortex
