Physiology of Pain & Analgesia

Question 1

What are the 4 concepts of total pain?

Answer 1

Physical
Social
Psychological
Spiritual

Question 2

What’s the difference between acute vs chronic pain ?

Answer 2

Acute pain is a short acting pain that alerts us of injury where as chronic pain is a pain that persist longer than the normal healing time (3 months +)

Question 3

What’s the difference between nociceptive vs neuropathic pain ?

Answer 3

Nociceptive pain is the bodies reaction to painful stimuli caused by damage to the bodies tissue it feels sharp, aching or throbbing and is often caused by external injury such as stabbing your toe. Neuropathic pain is caused by damage or injury to the nerves that transfer injury information between the brain and spinal chord.

Question 4

What’s the difference between somatic vs visceral pain ?

Answer 4

Somatic pain comes from skin, muscles and soft tissues where as visceral pain comes from internal organs.

Question 5

What is a noxious stimuli ?

Answer 5

Is actually or potentially causing damage to tissues and liable to cause pain.

Question 6

What are the 4 steps to nociceptive ? ( The pain pathway)

Answer 6

1- Transduction
2-Transmission
3-Modulation
4- Perception

Question 7

Explain the pain pathway ( Transduction, Transmission, Modulation, Perception)

Answer 7

Transduction - A Noxious stimuli is converted into electrical activity at sensory nerve endings.
Transmission - Signals are sent to the spinothalmic pathway.
Modulation - Once the signals reach the thalamus they are modified to either be enhanced or suppressed.
Perception - Signals are sent to the cortex where you are able to perceive and feel the pain.

Question 8

What’s a A delta fibre ?

Answer 8

Mylenataed fibre.
Produces a quick stabbing pain.
Send a fast signal during Transduction.

Question 9

What’s a c fibre ?

Answer 9

Smaller, non myelinated fibre.
Sends slow signals.
Produces a scull aching pain

Question 10

Name 3 inflammatory mediators

Answer 10

Histamine
Bradykinin
Prostaglandins

Question 11

Explain what arachidonic acid does to the body during inflammatory response.

Answer 11

Arachidonic acid is released after inflammatory response. It stimulates cox 2 enzymes to stimulate the production of prostaglandins which are responsible for pain, fever and inflammation.

Question 12

What are prostaglandins?

Answer 12

A group of lipids that are involved in dealing with injury and illness . They control processes such as inflammation.

Question 13

What are mechanoreceptor ?

Answer 13

Detect stimuli such as touch, pressure, and vibration.

Nociceptors detect pain.

Question 14

What is nociception?

Answer 14

Nociception is the process by which noxious stimuli is transmitted to the brain for processing.

Question 15

When prescribing analgesia what should be followed?

Answer 15

The WHO analgesic ladder

Question 16

Explain the 3 steps to the WHO analgesic ladder

Answer 16

1 - Non opioid (paracetamol, NSAID) +/- Adjuncts

2- Opioid for mild to moderate pain (codeine, tramadol) +/- non opioid, +/- adjunct

3- Opioid for moderate to severe pain (morphine,oxycodone,fentanyl) +/- non opioid, +/- adjunct

Question 17

How would you use the WHO analgesic ladder in an acute or post operative situation ?

Answer 17

Start with step 3 end with step 1

Question 18

Name some adjuncts to use in relationship to the WHO analgesic ladder.

Answer 18

Benzodiazepines - Dizaepam to reduce anxiety
Antiemetic - Reduce sickness
Laxative - Opioids cause constipation
Buscopan- Reduce abdominal cramps
Tricyclics- Antidepressants
Corticosteroids - Steroids to reduce inflammation

Question 19

Which pathway paracetamol inhibit ? Why is this good ?

Answer 19

Cox 2

It does not inhibit cox 1 so avoids many side effects of NSAIDS.

Question 20

How does paracetamol induced hepatoxicity occur ?

Answer 20

2% of paracetamol is metabolised to NAPQI which is very toxic to the liver.

Glutathione metabolises NAPQI into paracetamol mercapturate, a harmless metabolite.

In overdose, glutathione isn’t synthesised and so NAPQI builds up to toxic levels causing rapid liver damage.

Question 21

Explain the brains analgesic system

Answer 21

1 - Neurones descending from the brain stem encounter the ascending nociceptors neurons in the dorsal horn that are trying to Transmit the incoming pain signal.

2- The descending neurons release peptides that are like opioid molecules (enkephalin, endorphins or dymoprhins) these help to block the pain signal that the ascending neurons are trying to transmit.

3- The peptides bind to opioid receptors on the pre- and post- synaptic membrane to inhibit the release of glutamate that would assist transmission of the pain signal.

Question 22

What are some opioid considerations ?

Answer 22

• Nausea and vomiting
• Reduction in GI motility (constipation)
• Dependance and addiction risks.
• Risk of respiratory depression.

Question 23

Explain the Role of the nurse relating to pain management and analgesia.

Answer 23

• The rights of medication
• NMC code (2018)
• Responsibility relating to control drugs
• Pain assessment and continued monitoring
• Reassurance and education
• Non pharmacological pain management interventions

Question 24

What does the cyclogenase pathway produce which is involved in the aggregation of platelets and coagulation ?

Answer 24

Thromboxanes

Question 25

How do opioids stop pain ?

Answer 25

Bind to opioid receptors to have pain relieving effects.

Inhibiting the transmission of pain information to the brain

Question 26

Explain the action of morphine sulphate at the opioid receptor.

Answer 26

Binds to the opioid receptor and blocks transmission of nociceptive pain.