Anaesthetics - pain Flashcards
Pain definition
unpleasant sensory and emotional experience
actual or potential tissue damage
Why bother to treat pain?
1 in 4 have persistent pain
QOL, years lost to disability (back pain)
basic human right
Benefits of treating pain - patient
physical: increased sleep and appetite, fewer medical conditions
Psychological: decreased suffering, depression, anxiety
Benefits of treating pain - family
improved functioning as family member, working
Benefits of treating pain - society
lower health costs and contribute to community
Classifying pain - 3 main categories
duration
cause
mechanism
classifying pain - duration
acute, chronic, acute on chronic
Classifying pain - cause
cancer or non-cancer
Classifying pain - mechanism
nociceptive or neuropathic
Acute and chronic pain
acute - recent onset and probable limited duration
chronic more than 3 months
Cancer pain
cancer pain is progressive, acute on chronic
nociceptive pain characteristics
obvious tissue injury or illness
protective function
physiological or inflammatory pain
sharp+/- dull, well localised
Neuropathic pain characteristics
nervous system damage or abnormality
burning, shooting, numb, pins and needles, not well localised
Pain physiology - periphery
tissue damage leads to stimulating nociceptors
A delta and C fibres to spinal cord
1st relay station of pain
dorsal horn
Tract for pain
spinothalamic
2nd relay station
thalamus
What parts of the brain does the thalamus connect to?
cortex
limbic system
brainstem
What part of the brain perceives pain?
cortex
Modulation of pain
descending inhibitory pathways from brain to dorsal horn
Pathology of neuropathic pain and examples
abnormal processing of pain signal
nervous system damage or dysfunction
eg nerve trauma, diabetes, fibromyalgia, chronic tension headache
The biological changes in neuropathic pain
increased receptor number
abnormal sensitisation of nerves
chemical changes in dorsal horn
loss of normal inhibitory modulation
Simple analgesics
paracetamol and NSAIDs
Examples of opioids
morphine, codeine, fentanyl
What class of drug is tramadol?
5HT/NA reuptake inhibitor
Example of an antidepressant
amitriptyline
duloxetine
Gabapentin is what class of drug?
anticonvulsant
Give an example of a topical agent analgesic
capsaicin
Non drug treatments for periphery pain
RICE
Drug treatments for periphery
NSAIDs
LA
Non drug treatment for spinal cord
acupuncture
TENS
massage
Drug treatments for spinal cord
LA
opioids
ketamine
Non drug treatments for the brain
psychological
Drug treatments for the brain
paracetamol
opioids
amitriptyline
clonidine
Advantages of paracetamol
cheap
safe
can be given oral/rectal/IV
What is paracetamol good for?
mild pain by itself
mod-severe pain with other drugs
Disadvantages of paracetamol
Liver damage in overdose
Examples of NSAIDs
aspirin, ibuprofen, diclofenac
Advantages of NSAIDs
cheap
generally safe
good for nociceptive pain
Disadvantage of NSAIDs
GI/Renal side effects
sensitive asthmatics
Advantages of codeine
cheap, safe
mild-mod acute nociceptive pain
Disadvantages of codeine
constipation
nausea, sedation
late respiratory depression
not good for chronic pain
Advantages of tramadol
less respiratory depression
can be used with opioids and simple analgesics
not a controlled drug
Disadvantages of tramadol
nausea and vomiting
Advantages of morphine
cheap, generally safe
oral/IV/IM/SC
effective if given regularly
What pain is morphine good for?
acute nociceptive pain
chronic cancer pain
Disadvantages of morphine
constipation
respiratory depression in high dose
addiction
controlled drug
Oral dose is how many times the IV/IM/SC dose for morphine?
2-3
Amitriptyline class and how it works
TCA
increases descending inhibitory signals
Advantages of amitryptiline
cheap, safe in low dose
good for neuropathic pain
also treats depression, poor sleep
Disadvantages of amitriptyline
anti-cholinergic side effects
eg glaucoma, urinary retention
3 anticonvulsant drugs
sodium valproate
gabapentin
carbamazepine
Anti convulsant drugs how they work and what pain they are good for
membrane stabilisers - reduce abnormal firing of nerves
neuropathic pain
Delivery routes
oral rectal IV IM SC sublingual transdermal
Delivery routes for LA
epidural intrathecal wound catheters nerve plexus catheters local infiltration of wounds
5 ways for pain assessment
verbal rating score numerical rating score visual analogue scale smiling faces abbey pain scale
Who is the abbey pain scale used on?
confused patients
Non drug treatments
RICE
surgery
acupuncture, physio
counselling, reassurance
WHO pain ladder - what pain?
acute nociceptive
step 1 - WHO ladder
non opioids - aspirin, NSAID or paracetamol
Step 2 - WHO ladder
mild opioids eg codeine with or without non-opiates
Step 3 - WHO ladder
strong opioids eg morphine with or without non-opioids
Stop NSAIDs or paracetamol first and why?
NSAIDs as more adverse effects
RAT approach to pain
Recognise
assess
treat
Recognising pain
ask and look
patients family and other healthcare workers know?
Assessing severity of pain
pain score - rest and moving
pain affect patient? eg cough and working
Neuropathic features
burning or shooting pain
phantom limb pain
pins and needles, numb
Assessment of pain
severity
type
other factors
Assessing pain - other factors
physical and psychological
What do we do after RAT?
reassess the patient
