Pain Management Flashcards by Kerry Hendrie

Behaviour and vital signs (blood pressure, pulse) are reliable indicators of pain. True/False?

False

Neither sensitive nor specific - self-reporting is much more reliable

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What is allodynia?

Pain from a stimulus that is not normally painful

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What is hyperalgesia?

Pain that is beyond what is expected from a painful stimulus

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Which drugs form the WHO ladder for treating pain?

Non-opiods: paracetamol
Non-opiods: NSAIDs
Weak opiods: tramadol, codeine
Strong opiods: morphine, oxycodone, hydromorphine, heroin, fentanyl

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List some topical analgesics

Capsaicin
NSAIDs (diclofenac, naproxen, ibuprofen)
Rubefacients
Levomenthol
Lidocaine 5% plaster

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How do non-selective NSAIDs fight pain? What effect does this have?

Inhibit COX1 and COX2 enzymes that convert arachidonic acid into endoperoxides, which reduces prostaglandin synthesis
Reduces nociceptor sensitisation in inflammation

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How does paracetamol work? List a side effect

Inhibits prostaglandin synthesis

Risk of liver toxicity

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How do opioids work?

Activate descending inhibitory controls to reduce pain perception and suppress transmission of nociceptive signals in dorsal horn of spinal cord

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Anti-depressants can be used for neuropathic pain. How do they work? Give some examples and list some side effects

Inhibit noradrenaline and 5-HT uptake
TCAs (amitryptiline), SSRIs (duloxetine)
Constipation, dry mouth, arrhythmias, insomnia, somnolence

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List the two main subtypes of pain

Nociceptive: an appropriate physiologic response to painful stimulus via an intact nervous system
Neuropathic: an inappropriate response caused by a dysfunction in the CNS

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How is pain rated typically in Ninewells?

Verbal rating

0: no pain
1: mild
2: moderate
3: severe

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Outline the two activation routes that neurotransmitters can take to the brain

These neurotransmitters activate lamina 1 NK receptors which travel to the amygdala hypothalamus triggering an affective response.
The also activate lamina V NK receptors which travel to the thalamus and somatosensory cortex triggering a sensory response

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What type of fibres are activated by nociceptive stimulus on the skin? Where do they synapse?

Painful stimulus on the skin triggers Adelta and C fibres which synapse in the spinal cord, and low threshold mechanoreceptors (LTMs, ABeta fibres)

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What neurotransmitters are released when A delta and C gibres synapse?

Substance P and glutamate

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How is neuropathic pain typically described?

Burning, shooting, tingling, sensitivity

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List the aetiology of neuropathic pain

Shingles, post-herpatic neuralgia
Surgery
Trauma
Diabetic neuropathy
Amputation

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The brain is a fixed structure that does not evolve in the prescence of pain. True/ False?

False

The brain exhibits neuroplasticity

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What is the mechanism of action of topical analgesics? List some side effects

Reduce pain impulses transmitted by Adelta/ C fibres (do not affect the brain)
Rash, pruritis, erythema

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Anti-convulsants can be used for neuropathic pain. Give some examples and list some side effects

Carbamazepine, gabapentin, pregabalin

Sedation, dizziness, vomiting, ataxia, oedema, weight gain

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List types of complementary therapy used in the secondary management of pain

PHYSICAL: massage, aromatherapy, acupuncture, TENS, nerve block, spinal cord stimulation
MIND: relaxation, breathing, stress, sleep, hypnosis
PSYCHOLOGICAL: CBT, solution based

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Pain perception is consistent for each individual. True/ False?

False

Perception is variable depending on degree of nociceptor activity, level of sensory input and behavioural context

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List the brainstem regions involved in modifying afferent input, which are excited by electrical stimulation

Periaqueductal grey
Nucleus raphe magnus
Locus coeruleus

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The nucleus raphe magnus is involved in projecting what type of neurones?

Serotonergic neurones (5HT)

The locus coeruleus is involved in projecting what type of neurones?

Noradrenergic neurones (NA)

Where do afferent axons project to, to cause inhibition of nociceptive transmission in the dorsal cord?

Dorsolateral funiculus

Name the type of receptor which mediates the action of opiods

G protein coupled opiod receptor (Gi/o)

List the parts of the neurotransmission pathway inhibited by opiod action, and what subtype of Gi/o receptor they are mediated by

``` Voltage-gated calcium channel (reduces NT release): By subunit Potassium channel (reduce excitation of projection neurones): By subunit Adenylate cyclase: a subunit ```

List the three classification of opiod receptors, starting with the one that provides most analgesia

mu receptor delta receptor kappa receptor

List the main respiratory side effect of opiods, and the mechanism for which it occurs

Apnoea | Blunting of medullary respiratory centre to CO2

List the main CV side effect of opiods, and the mechanism for which it occurs

Orthostatic hypotension | Reduce sympathetic tone, bradycardia, histamin-evoked vasodilatation

List the main GI side effects of opiods, and the mechanism for which they occur

Nausea, vomiting, constipation, increased intrabiliary pressure Act on CTZ centre outside BBB, increase SM tone, reduce motility via enteric neurones

List the main CNS side effects of opiods

``` Confusion Euphoria Dysphonia Hallucinations Dizziness Myoclonus Hyperalgesia ```

What class of receptor to opiod agonists act on to prolong activation time? List some examples of opiod agonists

Mu receptors | Morphine, diamorphine, codeine, fentanyl, pethidine, tramadol, methadone

Where is morphine metabolised and excreted?

In the liver via gluconoridation into M3G (inactive) and M6G (retains analgesia and excreted by kidneys)

What is the clinical indication for diamorphine (heroin)?

Used in severe post-operative pain as it enters the CNS rapidly

Where is codeine metabolised?

Hepatic metabolism by demethylation to morphine by CYP2D6 and CYP3A4

Name two semi-synthetic derivatives of codeine with a higher potency

Oxycodone | Hydroxycodone

Fentanyl has an ____ potency than morphine

Higher

What is the clinical indication for pethidine?

Acute pain during labour

What class of drugs must not be used with pethidine and why?

MAO inhibitors | Causes hyperthermia, convulsions, excitement

What opiod is a partial agonist and can be used in patient-controlled injection systems?

Buprenophine

Outline the mechanism of action of tramadol

Potentation of descending serotonergic and adrenergic pathways

Tramadol is contraindicated in...

Epilepsy

Drugs with longer half lives are more addictive than drugs with shorter half lives. True/ False

True

What is the clinical indication for methadone?

Chronic cancer pain | Withdrawal from strong opiods

List some opiod antagonists

Naloxone Naltrexone Alvomopan, methylnatrexone

What is the clinical indication for naloxone?

Reverse opiod toxicity (respiratory or neurological depression) with strong opiod overdose Newborn babies with opiod toxicity due to pethidine use in labour

Naloxone is contraindicated in...

Opiod addicts or patients who receive high dose opiods regularly

It is preferential to inhibit COX2 enzyme as it has greater therapeutic benefit. How can this be achieved?

Using selective COX2 inhibitors 'coxibs'

List the to main long-term side effects of NSAID use, and the mechanism behind them

``` GI irritation (PGE2 protects again acid environment and is produced by COX1) Nephrotoxicity (COX2 produced by kidney) ```

What is the mechanism of action of gabapentin and pregabalin?

Reduce cell surface expression of a2delta subunit of voltage-gated calcium channels which are upregulated in damaged sensory neurones Reduces the production of neurotransmitters from the central terminal of nociceptive neurones

What s the mechanism of action of TCADs? Give some examples

Act centrally by reducing uptake of NA | Amytryptiline, nortrypitline, desipramine

What is the mechanism of action of SSRIs? Give some examples

Reduce uptake of NA Reduce reuptake of 5HT but have no analgesic effect Duloxetine, venlofaxine

Outline the machanism of action of carbamazepine

Block voltage-gated sodium channels that are upregulated in damaged nerve cells

Name the main clinical indication for carbamazepine

Trigeminal neuralgia