Pain Flashcards
What is pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Benefits of treating pain
To the patient - improved sleep - better appetite - fewer medical complications - reduced suffering - less depression + anxiety To the family - improved function as a family member e.g. parent - able to keep working For society - Lower health costs (e.g. shorter hosp stay) - able to contribute to the community
Classification of pain
Duration
Cause
Mechanism
Types of duration of pain
Acute
Chronic
Acute on chronic
Types of causes of pain
Cancer
Non-cancer
Types of mechanism of pain
Nociceptive
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
Features of cancer pain
Progressive
May be a mixture of acute and chronic
Features of non cancer pain
May be different causes
Acute or chronic
Features of nociceptive pain
Obvious tissue injury or illness
Protective function
Sharp +/- dull
Well localised
What is nociceptive pain also known as?
Physiological or inflammatory pain
What function does nociceptive pain have?
Protective function
Description of the pain in nociceptive pain
Sharp + / - dull
Well localised
Features of neuropathic pain
Nervous system damage or abnormality Tissue injury may not be obvious Does not have a protective function Burning, shooting + / - numbness, pins and needles Not well localised Abnormal processing of pain signal
Does neuropathic pain have a protective function?
No
Description of the pain in neuropathic pain
Burning, shooting +/- numbness, pins and needles
Not very well localised
4 steps of the pain physiology
Periphery
Spinal cord
Brain
Modulation
What happens in the physiology of pain of the periphery stage?
- tissue injury
- release of chemicals eg. prostaglandins, substance P
- Stimulation of pain receptors (nociceptors)
- Signal travels in A lamda or C nerves to spinal cord
What happens in the physiology of pain in the spinal cord stage?
- Dorsal horn is the first relay station
- A lamba or C nerves synapses (connects) with second nerve
- Second nerve travels up opposite side of spinal cord (spinothalamic tract)
What is the first relay station of the physiology of pain?
Dorsal horn
What happens in the physiology of pain in the brain stage?
Thalamus is the second relay station Connections to many parts of the brain - cortex - limbic system - brainstem Pain perception occurs in the cortex
Where is the second relay station?
Thalamus
Where does pain perception occur?
In the cortex
What happens in the physiology of pain in the modulation stage?
Descending pathway from brain to the dorsal horn
Usually decreases the brain signal
What does the “gate theory” of pain involve?
Noxious (pain) stimulus as well as a distractive stimulus (e.g. rubbing, massaging, application of heat etc)
- the distractive stimulus has larger peripheral nerve fibres than the noxious stimulus (which are small)
Examples of neuropathic pain
Damage - nerve trauma - diabetic pain Dysfunction - fibromyalgia - chronic tension headache
Pathological mechanisms of pain
Increased receptor numbers Abnormal sensation of nerves - peripheral - central Chemical changes in the dorsal horn Loss of normal inhibitory modulation
Drug classifications
Simple analgesics
Opioids
Other analgesics
Examples of simple analgesics
Paracetamol (acetaminophen)
NSAIDs
- diclophenac
- ibuprofen
Examples of Other analgesics used
Tramadol Antidepressants Anticonvulsants Ketamine Local anaesthetics Topical agents e.g. Capsaicin
Treatment of peripheral pain
Non drug - rest - ice - compression - elevation NSAIDs Local anaesthetics
Treatment of spinal cord pain
Non drug - acupuncture - massage - TENS local anaesthetics opioids ketamine
Treatment of brain pain
Non drug - psychological treatment Paracetamol Opioids Amitriptyline Clonidine
Disadvantages of paracetamol
Liver damage on overdose
How can paracetamol be given?
Orally
Rectally
IV
Examples of NSAIDs
Aspirin
ibruprofen
Diclofenac
Disadvantages of NSAIDs
GI and renal side effects plus sensitive asthmatics
Disadvantages of codeine
Constipation
Not good for chronic pain
Disadvantages tramadol
Nausea
Vomiting
How can morphine be given?
oral
IV
IM
SC
Disadvantages of morphine
Constipation
Respiratory depression in high dose
Misunderstandings about addiction
Controlled drug
What is paracetamol good for?
Mild pain (by itself) Mod - severe pain (with other drugs)
What are NSAIDs good for?
Nociceptive pain
- best given regularly with paracetamol (synergism)
What is codeine good for?
Mild - moderate acute nociceptive pain
- best given regularly with paracetamol
What is morphine good for?
Moderate - severe acute nociceptive pain (e.g. post op pain)
Chronic cancer pain
Oral dose of morphine vs other routes
Oral dose is 2-3x IV / IM / SC dose
What is amitriptyline?
A tricyclic antidepressant (TCA)
What is amitriptyline good for?
Neuropathic pain
Depression
Poor sleep
Disadvantages of amitriptyline
Anti-cholinergic side effects (e.g. glaucoma, urinary retention)
Examples of anti convulsant drugs
Carbamazepine
Sodium valproate
Gabapentin
What do anticonvulsant drugs do?
Membrane stabilisers
Reduce abnormal firing of nerves
What are anticonvulsant drugs good for?
Neuropathic pain
Possible delivery routes
Oral Rectal Sublingual Subcutaneous Transdermal Intramuscular Intravenous - boluses
Delivery routes for local anaesthetics
Epidural (+/- opiates) Intrathecal (+/- opiates) Wound catheters Nerve Plexus Catheters Local infiltration of wounds
Pain assessment is done by……
Verbal rating score Numerical rating score Visual Analogue Scale Smiling faces Abbey pain scale (for confused patients)
What type of pain is not responsive to the WHO pain ladder drugs?
Neuropathic pain
WHO analgesic (pain relief) ladder
Step 1 - mild to moderate pain
- non opioids - aspirin, NSAIDs, paracetamol
Step 2 - moderate to severe pain
- mild opioids (e.g. codeine) with or without non-opioids
Step 3 - severe pain
- strong opioids (e.g. morphine) with or without non opioids
Where to prescribe from the WHO ladder in mild pain
Start at the bottom
Where to prescribe from the WHO ladder in moderate pain
Bottom of the ladder plus the middle rung
Where to prescribe from the WHO ladder in severe pain
Bottom of the pain ladder plus the top of the pain ladder
Miss out the middle
As the pain resolves, where do you prescribe from on the pain ladder?
Move down the ladder
As pain subsides, do you stop NSAIDs or paracetamol first and why?
NSAIDs
as more adverse effects with NSAIDs
RAT approach to pain management
Recognise
- does the patient have pain? - ask, look, other people
Assess
- severity
- pain score (at rest, with movement)
- how is the pain affecting the patient ( can patient cough / move / work?)
- type
- physical factors - other illnesses
- anger , anxiety, depression
- lack of social supports
Treatment
What does RICE stand for?
Rest
Ice
Compression
Elevation of injuries
What is done after RAT?
Reassure the patient
- is it working?
- are other treatments needed?
