Pain Flashcards by Ciaran Gallagher

Define pain

An unpleasant sensory + emotional experience associated with actual or potential tissue damage

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Benefits of treating pain

Physical

Improved sleep, better appetite
Fewer medical complications (e.g. MI, pneumonia)

Psychological

Reduced suffering
Less depression + anxiety

For Society

Lower health costs(e.g. shorter hospital stay
Able to contribute to community
Able to work

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3 ways of classifying pain

Duration
Cause
Mechanism

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3 ways of classifying pain duration

Acute
Chronic
Acute on chronic

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2 ways of classifying the cause of pain

Cancer

- Non-cancer

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2 ways of classifying the mechanism of pain

Nociceptive

- Neuropathic

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Define acute and chronic pain

Acute
-Pain of recent onset + probable limited duration

Chronic

Pain lasting > 3 months
Pain lasting after normal healing
Often no identifiable cause

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Describe cancer and non-cancer pain

Cancer

Progressive
May be a mix of acute + chronic

Non-cancer

Many different causes
Acute or chronic

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Define nociceptive pain

-Obvious tissue injury or illness
-Protective function
-Description
Sharp +/- dull
Well localised
-Also called physiological or inflammatory pain

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Define neuropathic pain

-Nervous system damage/abnormality
-No protective function
-Description
Burning, shooting +/- numbness, pins and needles
Not well localised
-Tissue injury may not be obvious

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4 steps in pain physiology

Periphery
Spinal cord
Brain
Modulation

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What’s involved in the periphery step of pain

Tissue injury
Release of chemicals (prostaglandins, substance P)
Stimulation of nociceptors
Signal travels in A-delta or C nerve fibres to spinal cord

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What’s involved in the spinal cord step of pain

Dorsal horn in the 1st relay station
A-delta or C nerve fibre synapses with 2nd nerve
2nd nerve travels up OPPOSITE side of spinal cord

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What’s involved in the brain step of pain

-Thalamus is the secondary relay station
-Connections to many parts of brain
Cortex
Limbic system
Brainstem
-Pain perception occurs in cortex

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What’s involved in the modulation step of pain

Descending pathway from brain to dorsal horn

- Usually decreases pain signal

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Describe the gate control theory

Non-painful input closes the “gates” to painful input
Which prevents pain sensation from traveling to the central nervous system
Therefore, stimulation by non-noxious input is able to suppress pain (hit head then rubbing the spot you hit)

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4 examples of neuropathic pain

Nerve trauma
Diabetic neuropathy
Fibromyalgia
Chronic tension headache

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4 pathological mechanisms of neuropathic pain

Increased receptor numbers
Abnormal sensitisation of nerves (peripheral + central)
Chemical changes in dorsal horn
Loss of normal inhibitory modulation

2 broad categories of analgesics

Simple analgesics

- Opioids

3 simple analgesics

Paracetamol
Ibuprofen (NSAID)
Diclofenac (NSAID)

5 opioids

Codeine
Dihydrocodeine
Morphine
Oxycodone
Fentanyl

5 other analgesics

Tramadol (mixed opiate + 5HT/NA reuptake inhibitor)
Amitriptyline. Duloxetine (antidepressant)
Gabapentin (anticonvulsant)
Ketamine (NMDA receptor antagonist)
Capsaicin (topical agent)

+ Local anaesthetics

3 treatments for pain affecting the periphery step

Non-drug treatment (rest, ice, compression, elevation)
NSAID
Local anaesthetics

4 treatments for pain affecting the spinal cord step

-Non-drug treatment 
Massage, TENS "acupuncture"
-Opioids 
-Ketamine 
-Local anaesthetics

4 treatments for pain affecting the brain step

``` -Non-drug Psychological -Paracetamol -Opioids -Amitriptyline ```

Pros + cons of paracetamol

Pros - Cheap + safe - Can be give orally, rectally or IV - Good for Mild pain (by itself) + mod-severe pain (with other drugs) Cons -Liver damage in overdose

3 types of NSAIDs

- Aspirin - Ibuprofen - Diclofenac

Pros + cons of NSAIDs

Pros - Cheap, generally safe - Good for nociceptive pain (best given regularly with paracetamol [synergism] ) Cons -GI + renal SE + sensitive asthmatics

Pro + cons of codeine

Pros - Cheap, safe - Good for mild-severe acute nociceptive pain (best given regularly with paracetamol) Cons - Constipation - Not good for chronic pain

Pros + cons of Tramadol

- Less resp. depression - Can be used with opioids + simple analgesics - Not a controlled drug Cons -Nausea + vomiting

Pros + cons of morphine

``` Pros -Cheap, generally safe -Can be given orally, IV, IM, SC -Effective if given regularly -Good for: Mod-severe acute nociceptive pain (e.g. post-op) -Chronic cancer pain ``` Cons - Constipation - Resp. depression in high dose - Controlled dose - Misunderstanding about addiction

Pros + cons of amitriptyline

Pros - Cheap, safe in low dose - Good neuropathic pain - Also treats depression, poor sleep Disadvantage -Anti-cholinergic side effects (e.g. glaucoma, urinary retention)

3 examples of anticonvulsant drugs used to treat pain and their advantage

- Carbamazepine - Sodium valproate - Gabapentin

5 delivery routes of local analgesia

- Epidural (+/- opiates) - Intrathecal (+/- opiates) - Wound catheters - Nerve plexus catheters - Local infiltration of wounds

5 methods of pain assessment

- Verbal rating score - Numerical rating score - Visual analogue scale - Smiling faces - Abbey pain scale (for confused patients)

Non-drug treatment of pain

Physical - RICE - Surgery - Massage, physiotherapy, "acupuncture" Psychological - Explanation - Reassurance - Counselling

How to treat acute and neuropathic pain

- Acute, Use WHO analgesic ladder | - Neuropathic, use alternative analgesics and/or non-drug treatments

Describe the WHO analgesic ladder

``` Step 1 (mild-moderate pain) -Non-opioids (NSAIDs + Paracetamol) ``` ``` Step 2 (moderate to severe pain) -Mild opiates (e.g. codeine with/without non-opioids ``` ``` Step 3 (severe pain) -Strong opioids (e.g. morphine) with/without non-opioids ```

What to do when 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 effects with NSAIDs

Describe the RAT approach to pain management

-Recognise -Assess Severity Type Other factors (other illnesses, anger, anxiety, depression, lack of support) -Treat (drug/non-drug)

How to asses severity of pain

-Pain score (at rest + moving) -How is it affecting the patient Can they move, cough, work?

How to assess pain type

-Acute/chronic (time) -Cancer/non-cancer -Nociceptive/neuropathic Burning, shooting, numbness, pin + needles, phantom limb all = neuropathic

How to treat mild, moderate and severe pain

- Mild = Paracetamol (+/- NSAIDs) - Moderate = Codeine/alternative + Paracetamol (+/- NSAIDs) - Severe = Morphine + Paracetamol (+/- NSAIDs)