Pain Flashcards by Catherine Wright

What is pain?

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

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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

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Classification of pain

Duration
Cause
Mechanism

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Types of duration of pain

Acute
Chronic
Acute on chronic

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Types of causes of pain

Cancer

Non-cancer

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Types of mechanism of pain

Nociceptive

Neuropathic

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What is acute pain?

Pain of recent onset and probable limited duration

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What is chronic pain?

Pain lasting for more than 3 months
Pain lasting after normal healing
Often no identifiable cause

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Features of cancer pain

Progressive

May be a mixture of acute and chronic

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Features of non cancer pain

May be different causes

Acute or chronic

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Features of nociceptive pain

Obvious tissue injury or illness
Protective function
Sharp +/- dull
Well localised

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What is nociceptive pain also known as?

Physiological or inflammatory pain

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What function does nociceptive pain have?

Protective function

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Description of the pain in nociceptive pain

Sharp + / - dull

Well localised

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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

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Does neuropathic pain have a protective function?

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Description of the pain in neuropathic pain

Burning, shooting +/- numbness, pins and needles

Not very well localised

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4 steps of the pain physiology

Periphery
Spinal cord
Brain
Modulation

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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

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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)

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What is the first relay station of the physiology of pain?

Dorsal horn

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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

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Where is the second relay station?

Thalamus

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Where does pain perception occur?

In the cortex

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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?