Anaesthetics: Essential Pain Management Flashcards
What is pain?
an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
What are the physical benefits for the patient if we treat pain?
- improved sleep
- better appetite
- fewer medical complications (e.g. heart attack, pneumonia)
What are the psychological benefits for the patient if we treat pain?
- reduced suffering
- less depression, anxiety
What are the benefits for the family if we treat pain?
- improved functioning as a family member (e.g. as a father or mother)
- able to keep working
What are the benefits for society if we treat pain?
- lower health costs (e.g. hospital stay)
- able to contribute to the community
How can pain be classified?
duration: acute or chronic
cause: cancer or non-cancer
mechanism: nociceptive or neuropathic
What is acute pain?
pain of recent onset and probable limited duration
What is chronic pain?
- pain lasting for more than 3 months
- pain lasting after normal healing
- often no identifiable cause
Describe pain from cancer vs non cancer
cancer: progressive, a mixture of acute and chronic
non cancer: acute or chronic
Describe nociceptive vs neuropathic pain
nociceptive: sharp +/- dull, well localised
neuropathic: burning, shooting +/- numbness, pins and needles, not well localised
when does nociceptive & neuropathic pain occur?
nociceptive: obvious tissue injury or illness
neuropathic: nervous system damage or abnormality
What does nociceptive pain function as?
protective function
also referred to as inflammatory pain
What are the 4 steps in the physiology of pain?
- periphery
- spinal cord
- brain
- modulation
What physiology occurs in the periphery during the pain response?
- 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
What physiology occurs in the spinal cord during the pain response?
- 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
What physiology occurs in the brain during the pain response?
- thalamus is the second relay station
- connections to many parts of the brain: cortex, limbic system and brainstem
- pain perception occurs in the cortex
What physiology occurs during modulation in the pain response?
- descending pathway from brain to dorsal horn
- usually decreases pain signal
What is the gate theory?
stimulation by non-noxious input is able to suppress pain by closing the ‘gate’ to painful input preventing pain sensation from travelling to the cortex
Give examples of neuropathic pain
- nerve trauma, diabetic pain (damage)
- fibromyalgia, chronic tension headache (dysfunction)
What is the pathology behind neuropathic pain?
- increased receptor numbers
- abnormal sensitisation of nerves (peripheral and central)
- chemical changes in the dorsal horn
- loss of normal inhibitory modulation
What types of drugs can be used for the treatment of pain?
- simple analgesics
- opioids
- other analgesics
Give examples of simple analgesics.
- paracetamol (acetaminophen)
- non-steroidal anti-inflammatory drugs (diclofenac, ibuprofen)
Give examples of opioid drugs
weak: codeine, dihydrocodeine, tramadol
strong: morphine, oxycodone, fentanyl
Other than simple analgesics and opioids, what other drugs can be used for pain?
- tramadol (mixed opiate and 5HT/NA reuptake inhibitor)
- antidepressants (e.g. amitriptyline, duloxetine)
- anticonvulsants (e.g. gabapentin)
- ketamine (NMDA receptor antagonist)
- local anaesthetics
- topical agents (e.g. Capsaicin)
What non-drug treatments can be used to act at the periphery?
- rest
- ice
- compression
- elevation
What drugs can be used to act at the periphery?
- NSAIDs
- local anaesthetics
What non-drug treatments can be used to act at the spinal cord?
- acupuncture
- massage
- TENS
What drugs can be used to act at the spinal cord?
- local anaesthetics
- opioids
- ketamine
What non-drug treatment can be used to act at the brain?
psychological therapies
What drugs can be used to act on the brain?
- paracetamol
- opioids
- amitriptyline
- clonidine
What route of drug delivery is preferred?
Oral
What are the advantages of paracetamol?
- cheap, safe
- can be given orally, rectally or intravenously
What is the disadvantage of paracetamol?
liver damage in overdose
What is paracetamol good for?
mild pain (by itself) or moderate- severe pain (with other drugs)
Give examples of NSAIDs
- aspirin
- ibuprofen
- diclofenac
What are the advantages of NSAIDs?
- cheap
- generally safe
What is the disadvantage of NSAIDs?
- GI and renal side effects
- sensitive for asthmatics
What are NSAIDs good for?
nociceptive pain
best given regularly with paracetamol (synergism)
What are the advantages of codeine?
- cheap
- safe
What is codeine good for?
mild to moderate acute nociceptive pain
What are the disadvantages of codeine?
- can cause constipation
- not good for chronic pain
What is tramadol?
painkiller with a weak opioid effect plus inhibitor of serotonin and noradrenaline reuptake (modulation)
What are the advantages of tramadol?
- less respiratory depression
- can be used with opioids and simple analgesics
- less constipating than other opioids
What are the disadvantages of tramadol?
nausea and vomiting
What are the advantages of morphine?
- cheap, generally safe
- can be given IV, IM, SC, intrathecally
- effective if given regularly
What is morphine good for?
- moderate to severe nociceptive pain (i.e. post-op pain)
- chronic cancer pain
not advised for neuropathic pain
What are the disadvantages of morphine?
- constipation
- respiratory depression in high dose
- avoidance due to fear of addiction
- controlled drug
How does the oral dose of morphine differ from the IV/IM/SC dose?
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?
tricyclic antidepressant
How does amitriptyline work?
increases descending inhibitory signals
What are the advantages of amitriptyline?
- cheap, safe in low dose
- good for neuropathic pain
- also treats depression and poor sleep
What are the disadvantages of amitriptyline?
anti-cholinergic side effects (i.e. glaucoma, urinary retention)
long term use might be linked with cognitive decline and dementia
Give examples of anticonvulsants that can be used for pain.
- carbamazepine (tegretol)
- sodium valproate (epilim)
- gabapentin (neurotonin)
Why are anticonvulsants also known as membrane stabilisers?
reduce abnormal firing of nerves
What are anticonvulsants good for?
neuropathic pain
How should neuropathic pain be managed?
Use alternative analgesics and/or psychological and non-drug treatments
What are the steps in the WHO pain ladder?
Step 1
- paracetamol +/- NSAIDs
Step 2
- paracetamol (+/- NSAIDs) + Codeine/alternative
Step 3
- paracetamol (+/-NSAID) + Morphine
How should the pain ladder be used for mild pain?
start at bottom of the pain ladder
How should the pain ladder be used for moderate pain?
bottom of pain ladder plus the middle ring
How should the pain ladder be used for sever pain?
- bottom of pain ladder plus top of ladder; miss out the middle
- okay to start at the top of the ladder for severe/unbearable pain
How should the pain ladder be used as pain resolves?
- move from top to middle of WHO ladder
- continue bottom rung drugs at all times
- lastly stop NSAIDs, then paracetamol as more adverse side effects with NSAIDs
What is the RAT approach?
- recognise
- assess
- treat
How do you recognise that a patient is in pain?
does the patient have pain?
- ask
- look (frowning, moving easily, sweating?)
do other people know the patient has pain?
- other health workers
- patient’s family
How do you assess a patient’s pain?
severity
- pain score at rest
- with movement
how does the pain affect the patient?
- can the patient move, cough?
- can the patient work?
what is the pain type
- nociceptive or neuropathic
What neuropathic features may pain have?
- burning or shooting pain
- phantom limb pain
- other features (pins and needles, numbness)
What other factors can influence the severity of a patient’s pain?
Physical factors
- other illnesses
Psychological and social factors
- anger, anxiety, depression
- lack of social support
What drugs are used in neuropathic pain?
- amitriptyline
- gabapentin
- duloxetine
What should be done after using the RAT algorithm?
Reassess the patient to see if the treatment is working and if any other treatments are required
What is RICE?
- Rest
- Ice
- Compression
- Elevation
