GI mc 2 Flashcards
hyperalgesia
increased sensitivity to stimuli
allodynia
misperception of pain to non-noxious stimuli
peripheral pain receptors and prolonged pain
can become sensitised
transmission of incoming nociceptive impulses is modulated by…
dorsal horn
where is pain transmitted
dorsal horn of the spinal cord
what do pain impulses do in the dorsal horn
decussate
where do pain impulses go when they have decussated
ascend via the spinothalamic tract to the reticular activating system (RAS) and thalamus
hyperalgesia
increased sensitivity to stimuli
allodynia
misperception of pain to non-noxious stimuli
what does dorsal horn recieve impulses from
peripheral touch receptors and from descending pathways that involve the limbic cortical systems
limbic cortical systems examples
orbital frontal cortex, amygdala, and hypothalamus
after morphine is given what is released
histamine
what does histamine do
flushing, tachycardia, hypotension, pruritus and bronchospasm
common side effects of opiods
constipation, nausea, confusion, hallucinations, flushing, dry mouth, difficulty peeing, hypotension
rare side effects of opiods
urinary retention, pruritus, delerium, myoclonus, hyperalgesia, resp depression, sexual dysfunction, biliary spasm and visual disturbance
what to give for opiod toxicity
naloxone
what is naloxone
opioid competitive antagonist
who has a longer half life opiod or naloxone
opiods
what does naloxone decrease
ED50
what is a common long term complication of opoids
constipation
what to give with opiods to avoid side effects
large bowel stimulant
what laxatives not to give with opiods
bulk forming laxatives
describe methylnaltrexone
opioid antagonist that does not cross the blood-brain barrier
how do you give methylnaltrexone
comes as infection only
whats good about methylnaltrexone
diminish the peripherally mediated side effects of opioids while maintaining central analgesic effects
who is methylnaltrexone approved in
OIC in patients with chronic pain
patients with advanced illness receiving palliative care who have had an inadequate response to traditional laxatives and here it can be used as an adjunct
Pain receptor activity can be directly blocked by
lidocaine
how can NSAIDs work for post op pain
diminish local hormonal response
neurotransmitter targets for analgesia
substance P, calcitonin gene-related peptide, aspartate, glutamate and GABA
how does paracetamol result in analgesia
action on spinal receptors through NAPQI acting on the TPRA1 receptor blocking pain signal transmission
what is Bupivacaine
local anaesthetic
Bupivacaine binds to
sodium channels makes them inactive so that no depolarisation can occur
2 sites of action of opiods
presynaptic= inhibit neurotransmitter release postsynaptic= inhibitory
morphine acts on what receptors
m
what does action on m receptors do
inhibits release of several different neurotransmitters incl NE, acetylcholine, substance P
where is vomitting controlled
vom centre in the brain stem
where do afferent stimuli arrive at the CTZ from
chemoreceptors and pressure receptors in the gut and CNS, as well as peripheral pain receptors
Ondansetron
selective serotonin receptor (5-HT3) antagonist
good about ondasteron
not sleepy
can give IV
Hyoscine
anticholinergic
cyclizine
antihistamine, H1 receptor antagonist
if an antihistamine cant cross BBB how does it work as an antiemetic
it cant
dexamethasone
glucocorticoid
what is dexamethasone used for
chemo N and V
prochlorperazine
antipsychotic, also antiemetic
Metoclopramide
dopamine receptor antagonist
Metoclopramide and prochlorperazine side efefcts
extrapyramidal
does domperidone cross BBB
no
how to treat dystonic reaction
procyclidine
how long does Procyclidine take to work
5-20 mins
Aprepitant
really bad chemotherapy treatment -needs to be given before nausea develops
Opioids have 3 potentially emetogenic mechanisms:
a direct effect on chemoreceptor trigger zone
enhanced vestibular sensitivity
delayed gastric emptying
nausea and opiods
tollerance builds quickly
chronic nausea and opiod use..
dopamine antagonist such as prochlorperazine or metoclopramide
metoclopramide affect on the bowel
prokinetic
what might you use haliperidol for
effective in opiate induced vomiting
Ondansetron and opiate nausea
can help as opiods work on the CTZ
can cause constipation
how often to give oramorph and why
every 4 hours - lasts 4-6 hours avoid break through pain
what is the rescue dose of oraporph
⅙ of the total 34 hour dose
