Pain Management Flashcards
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
What is allodynia?
Pain from a stimulus that is not normally painful
What is hyperalgesia?
Pain that is beyond what is expected from a painful stimulus
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
List some topical analgesics
Capsaicin NSAIDs (diclofenac, naproxen, ibuprofen) Rubefacients Levomenthol Lidocaine 5% plaster
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
How does paracetamol work? List a side effect
Inhibits prostaglandin synthesis
Risk of liver toxicity
How do opioids work?
Activate descending inhibitory controls to reduce pain perception and suppress transmission of nociceptive signals in dorsal horn of spinal cord
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
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
How is pain rated typically in Ninewells?
Verbal rating
0: no pain
1: mild
2: moderate
3: severe
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
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)
What neurotransmitters are released when A delta and C gibres synapse?
Substance P and glutamate
How is neuropathic pain typically described?
Burning, shooting, tingling, sensitivity
List the aetiology of neuropathic pain
Shingles, post-herpatic neuralgia Surgery Trauma Diabetic neuropathy Amputation
The brain is a fixed structure that does not evolve in the prescence of pain. True/ False?
False
The brain exhibits neuroplasticity
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
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
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
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
List the brainstem regions involved in modifying afferent input, which are excited by electrical stimulation
Periaqueductal grey
Nucleus raphe magnus
Locus coeruleus
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
