Pain and Pain Relief Flashcards
What is pain, according to the International Association for the Study of Pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
What fraction of people live with persistent pain?
1 in 4
What percentage of people attending A&E seeking help for pain will have made around 3 visits to their health care practitioner in the preceding weeks?
66%
What is the number 1 disease for years lost to disability worldwide?
Low back pain
What are the benefits of treating pain for the patient?
Physical - improved sleep, better appetite - fewer medical complications Psychological - reduced suffering - less depression and anxiety
What are the benefits of treating pain for the family?
Improved functioning as a family member
Able to keep working
What are the benefits of treating pain for society?
Lower health costs
Able to contribute to the community
How is pain classified?
By;
Duration
Cause
Mechanism
How is pain classified according to duration?
Acute
Chronic
Acute on chronic
How is pain classified according to cause?
Cancer
Non-cancer
How is pain classified according to mechanism?
Nociceptive
Neuropathic
What is the difference between acute and chronic pain?
Acute pain is pain of recent onset and probable limited duration
Chronic pain is;
- pain lasting for more than 3 months
- pain lasting after normal healing
- often no identifiable cause
What is the difference between cancer and non-cancer pain
Cancer pain
- progressive
- may be a mixture of acute and chronic
Non-cancer pain
- many different causes
- acute or chronic
This classification is more about the context in which pain occurs and how this influences management
What are the features of nociceptive pain?
Obvious tissue injury or illness
Also known as physiological or inflammatory pain
Protective function
Sharp/dull, well-localised
What are the features of neuropathic pain?
Nervous system damage or abnormality - neuropathic dysfunction
Tissue injury may not be obvious
Does not have a protective function
Burning, shooting, numbness, pins and needles, not well-localised
What are the 4 steps of pain physiology?
Periphery
Spinal cord
Brain
Modulation
What is the mechanism of pain physiology in the periphery?
Nociceptors in the periphery
Tissue injury - results in release of chemicals e.g. prostaglandins
Signal travels in Aδ or C fibres to spinal cord
What is the mechanism of pain physiology in the spinal cord?
Dorsal horn is the first relay station
Aδ or C nerve synapses with second nerve
Second nerve travels up the opposite side of the spinal cord
What is the mechanism of pain physiology in the brain?
Thalamus is the second relay station
Connects to many parts of the brain - cortex, limbic system, brainstem
Pain perception occurs in the cortex
What is the mechanism of pain modulation?
Descending pathway from brain to dorsal horn
Usually decreases pain signal
What is the gate theory?
When transmission cell is stimulated, pain signal is transmitted to the brain
The inhibitor neurone switches off anything stimulating the transmission cell so signals that stimulate the inhibitor neurone will reduce pain transmission and pain sensation
Light touch and pressure turn on the inhibitor neurone
Noxious stimuli inhibit the inhibitor neurone
Why does neuropathic pain occur?
Abnormal processing of pain signal
Nervous system damage or dysfunction
e.g. nerve trauma, diabetic pain, fibromyalgia
What are the pathological mechanisms of neuropathic pain?
Increased receptor numbers
Abnormal sensitisation of nerves - peripheral or central
Chemical changes in dorsal horn
Loss of normal inhibitory modulation
What are the simple analgesics?
Paracetamol
NSAIDs
What are the opioids used?
Mild - codeine, dihydrocodeine
Strong - morphine, oxycodone, fentanyl
What are other drugs used as analgesics?
Tramadol Anti-depressants e.g. amitriptyline Anti-convulsants e.g. gabapentin Ketamine Local anaesthetics Topical agents e.g. capsaicin
What are the non-drug treatments for peripheral pathologies causing pain?
Rest
Ice
Compression
Elevation
What are the drug treatments for peripheral pathologies causing pain?
NSAIDs
Local anaesthetics
What are the non-drug treatments for spinal cord pathologies causing pain?
Acupuncture
Massage
TENS
What are the drug treatments for spinal cord pathologies causing pain?
Local anaesthetics Spinal anaesthetics Epidural Opioids Ketamine
What are the non-drug treatments for brain pathologies causing pain?
Psychological treatment
What are the drug treatments for brain pathologies causing pain?
Paracetamol (most effective when used in adjunct with other pain treatments)
Opioids
Amitriptyline
Clonidine
What are the advantages of paracetamol?
Cheap, safe
Can be given orally, rectally or intravenously
Good for mild pain when used alone, and moderate-severe pain when used with other drugs
What are the disadvantages of paracetamol?
Liver damage in overdose
What are the commonly used NSAIDs?
Aspirin
Ibuprofen
Diclofenac
What are the advantages of NSAIDs?
Cheap
Generally safe
Good for nociceptive pain (works best when given regularly with paracetamol)
What are the disadvantages of paracetamol?
Gastrointestinal and renal side effects
Can aggravate asthma
What are the advantages of codeine?
Cheap
Safe
Good for mild-moderate acute nociceptive pain
Works best when given regularly with paracetamol
What are the disadvantages of codeine?
Constipation
Not good for chronic pain
How does tramadol work?
Weak opioid effect plus inhibitor of serotonin and noradrenaline reuptake
What are the advantages of tramadol?
Less respiratory depression
Can be used with opioids and simple analgesics
Not a controlled drug
What are the disadvantages of tramadol?
Nausea
Vomiting
What are the advantages of morphine?
Cheap Generally safe Can be given orally, IV, IM or SC Effective if given regularly Good for moderate-severe acute nociceptive pain e.g. post-op, chronic cancer pain
What are the disadvantages of morphine?
Constipation
Respiratory depression in high dose
Misunderstanding about addiction
Controlled drug
What is the safest way to administer morphine? Why?
Titration is generally the safest way to administer it as safety is dose-dependent
How does amitriptyline work?
Tricyclic antidepressant, increases descending inhibitory signals
What are the advantages of amitriptyline?
Cheap
Safe in low doses
Good for neuropathic pain
Also treats depression and poor sleep
What are the disadvantages of amitriptyline?
Anti-cholinergic side effects
Many other side effects
What are some anti-convulsant drugs?
Carbamazepine
Sodium valproate
Gabapentin
How do anti-convulsants work?
Reduce abnormal firing of nerves (membrane stabilisers) - good for neuropathic pain
What are the possible delivery routes for analgesia?
Oral Rectal Sublingual Subcutaneous Transdermal Intramuscular Intravenous
What are the possible delivery routes for local anaesthetics?
Epidural Intrathecal Wound catheters Nerve plexus catheters Local infiltration of wounds
What can be used for pain assessment?
Verbal rating score Numerical rating score Visual analogue scale Smiling faces Abbey pain scale
What are the non-drug treatments that can be offered for pain?
Physical
- rest, ice, compression, elevation (RICE)
- surgery
- acupuncture, massage, physiotherapy
Psychological
- explanation
- reassurance
- counselling
What type of pain is not responsive to the WHO pain ladder drugs?
Neuropathic
How does the WHO pain ladder link assessment to prescribing for acute nociceptive pain?
Mild pain - start at bottom of ladder
Moderate pain - bottom of ladder plus middle rung
Severe pain - bottom of ladder plus top of ladder, miss out middle
As pain resolves, move down the ladder, passing the middle rung first, continue bottom rung drugs at all times
Lastly, stop NSAIDs then paracetamol
What is the RAT approach to pain management?
Recognise
- does the patient have pain
- do other people know the patient has pain (family etc.)
Assess
- severity (pain score)
- type i.e. acute or chronic, cancer or non-cancer, nociceptive or neuropathic
- other factors e.g. how it is affecting the patient
Treat
- non-drug treatments
- drug treatment
What features should you look for when assessing a patient’s pain?
Neuropathic features
- burning or shooting pain
- phantom limb pain
- pins and needles, numbness
What other factors might affect a patient’s pain?
Physical factors e.g. other illnesses
Psychological and social factors e.g. anger, anxiety, depression, lack of social support
What are the drug treatments advised on WHO pain ladder?
Mild - paracetamol (+/- NSAID)
Moderate - paracetamol + codeine/alternative (+/- NSAID)
Severe - paracetamol + morphine (+/- NSAID)
What drugs (not on WHO pain ladder) should be used early in neuropathic pain treatment?
Amitriptyline
Gabapentin
Duloxetine
