11a. Drugs used in radiology II: anaesthetics and analgesics

what is the definition of an analgesic

medications and actions that act to relieve pain

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what are the 5 types of analgesia

non pharmacological 
paracetamol
NSAIDS
opiates
adjuvant agents

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what is the definition of anaesthesia

to be without pain

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what are the 3 types of anaesthesia

local
regional
general

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what is local anaesthesia

small area

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what is regional anaesthesia

block nerve and numb a body part

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what is general anaesthesia

go to sleep

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what is the 3 points of general anaesthesia

analgesics
muscle relaxation
hyponosis

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what is the clinical context of anathesia use

ED/ICU/interventional

paeds

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how is anaesthesia involved in radiology

radiological and interventional procedures can cause pain, anxiety, psychological and physical distress

this can be improved with sedation and anaesthesia, good pain relief gives good images

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what is the definition of pain

an unpleasant sensory and emotional experience associated with or resembling that associated with actual or potential tissue damage

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is pain objective

no its subjective

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is pain the same for everyone

no its highly variable

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what are the 2 types of pain

nociceptive pain

neuropathic pain

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what is nociceptive pain

pain from physical damage or potential damage to tissues

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what is neuropathic pain

due to inflammation, irritation compression or damage to nerves and is often associated with chronic pain

pain lasts after the tissue injury has resolved

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what is potential damage in terms of pain

no damage yet but nearly damaged and needs to get away from damage

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what are nocioceptors

specific pain receptors

nerve endings in most body tissues that only respond to damaging or potentially damaging stimuli

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where in the body are there no nociceptors

brain

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what are the 3 types of stimuli that can activate pain receptors

mechanical
heat
chemical

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what is transmission in terms of pain

nociceptive message transmitted from periphery to central nervous system

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what is the nociceptive message transmitted from periphery to central nervous system via

via axon of primary afferent nociceptor

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what is the structure of a neuron

cell body in dorsal root ganglion and long process called the axon that divides and sends one branch out to the periphery and one into spinal cord

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what are the 2 main types of pain fibres

non mylienated C fibres

thinly mylienated fast conducting A fibres

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what do the primary afferent nociceptors activate

second order pain transmission cells that run up the spinothalamic tracts in the spinal cord and transmit message to primary somatosensory region of brain

what type of pain is Cfibres responsible for

slow burning pain

what type of pain is Dfibres responsible for

sharp pinching pain

who is analgesics prescribed and administered by

prescribed by doctor and administered by dr or nurse

what is the WHO ladder in terms of analgesics

Start with non-pharmaceutical then weak opioids then opioids then adjuvant agents

what is multimodal analgesia

Aim to use multimodal analgesics, use lots of diff receptors to manage pain

what is paracetamol's drug type

analgesics/pain killers

can you buy paracetamol over the counter

yes

how effective is paracetamol

surprisingly effective

what are the side effects like for paracetamol

minimal

what is the action of paracetamol thought to be

mainly central action acts via the peroxidase site of COX 2

how is paracetamol similar and different from NSAIDs

similar analgesics and antipyretic effects to NSAIDS lacks anti-inflammatory and anti platelets effects

when can paracetamol be toxic

normal metabolism is overwhelmed and results in increased toxic byproduct produced leading to liver damage

what 4 things can increase risk of paracetamol toxicity

high paracetamol dose chronic alcohol/drug use pre-existing hepatic failure malnutrition

what are NSAIDs

non steroidal anti inflammatory drugs

how does NSAIDS work

work by selective or non selective blockade of COX1/2 enzymes resulting in decreased prostaglandin production

what is broken down into COX 1/2 in terms of NSAIDs

arachidonic acids

what does prostaglandins do

mediate inflammation, transduction of pain signals and fever

what is NSAIDs action thought to be

mainly peripheral

what 2 things does COX 1 affect

gastric protection | platelet function

what 3 things does COX2 affect

pain fever bone formation

what are 3 of NSAIDs uses

analgesia anti-inflammatory anti-pyretic

what are the side effects of COX1 targeted NSAIDs 5 things

``` gastric ulcers increased bleeding tendency decreased renal blood flow bronchoconstriction effects binding of other deugs ```

what are the 3 side effects of COX 2

increased risk of MI or stroke similar renal risks increased anaphylaxis risk

what are opiates

naturally occurring compounds derived from poppy plants

what are 3 examples of opiates

morphine codeine heroin

what are opiods

overarching terms including natural synthetic and semi synthetic drugs

what are 3 examples of opiods

oxycodone fentanyl tramadol

what are opiod receptors

G protein coupled receptors

why do opioids act at multiple levels

they are widespread

what are the 4 levels that opiods work at

peripherally spinal cord central activity activate reward signalling pathway

how do opiods peripheral receptors work

modulate nociceptive transmission in the dorsal horn through descending pathways

how do opiods spinal cord receptors work

inhibit release of substance P from primary sensory neurons

what system does opioids also activate and how is this linked to drug abuse

reward signaling pathways -> addiction

what are the 3 types of classical opioid receptors

M, delta, k

what are common CNS side effects of opioids - 4 things

sedation delirium/confusion dizziness physical dependence and tolerance

what are 4 GIT side effects of opioids

nausea vomiting constipation dry mouth

what are 2 respiratory side effects of opioids

respiratory depression and arrest

what are 2 skin side effects of opioids

itch | sweating

what is tolerance to opioids and what does it result in

needs escalating doses to get same outcome

what are 2 common weak opioids

tramadol and codeine

where does tramadol act

centrally acting partial opioid agonist

what is the potency of tramadol in comparison to morphine

5-10 x less potent

how does tramadol work

inhibits neuronal uptake of noradrenaline and increases serotonin release

what is the respiratory and GI side effects of tramadol like in comparison to morphine

much less resp depression and consitpation

tramadol cant be used for patients with what condition and why

epilepsy tramadol results in a lowered seizure threshold

where does codeine act

centrally acting opioid agonist

what is the potency of codeine in comparison to morphine

10x less potent

how is codeine a prodrug and what does this mean

prodrug that is metabolized to morphine 20mg of codeine -> 1mg morphine

why cant some people not feel effects of codeine

genetic differences cannot metabolize codeine into morphine so get minimal pain relief (codeine itself doesnt provide pain relief - has to be in morphine form)

what is the respiratory side effects of codeine like in comparison to morphine

less resp depression than morphine

what are 3 types of strong opioids

morphine fentanyl oxycodone

what can morphine do in terms of histamine release

can cause histamine release that can cause skin rashes and low BP

how potent is fentanyl compared to morphine

100x more potent

what is the onset and duration of action for fentanyl

fast onset short duration of action

what are the 2 ways that fentanyl can be administered

patches or IV

how potent is oxycodone compared to morphine

mildly stronger than morphine

how long does morphine to set in and how long does it stick around for

5mins to set in | 2hrs duration

why cant you give fentanyl orally

its fully broken down in the stomach

why does oxycodone give high

kicks in faster

what are 3 examples of anticonvulsants

gabapentin pregabalin carbamazepine

how do anticonvulsants work

via central neurotransmitter effects

what are the 4 side effects of anti convulsants

sedation nausea vomiting ataxia

what are 2 examples of antidepressants

TCAs and SSRIs

how do antidepressants work

via noradrenergic and seroternergenic pathways blocking spinal pathways

what are the 3 side effects of antidepressants

sedation dry mouth cardiac toxicity

what is an example of NMDA antagonists

ketamine

how do NMDA antagonists work

noncompetitive inhibitor at NMDA receptor

what are 5 side effects of NMDA antagonists

``` dysphoria increased secretions addiction hallucinations anesthetics at high doses ```

how do GABA agonists work

activates GABA receptors decreasing neurotransmitter release in pain pathways

what are the 4 side effects of GABA agonists

sedation nausea vomiting decreased blood pressure

how do A2 agonists work

decrease central sympathetic nervous activity and inhibits pain transmission peripherally

what are the 3 side effects of A2 agonists

low blood pressure sedation weakness

how are local anesthetics IV given

as IV infusion

how do local anesthetics IV work

blocks sodium channels when used IV it decreases pain transmissions peripherally and centrally

what are the 2 side effects of local anesthetics IV

cardiac and neurological toxicity (LAST)

what is the therapeutic window like for local anesthetics IVs

narrow

how are local anesthetics regional adminsitered

injected around nerves, subcutaneously or into epidural/thecal space

how do local anesthetics regional work

blocks sodium channels -> blocks transmission of pain through nerves

what are the 4 side effects of local anesthetics regional

LAST motor blockade insenate limb local nerve toxicity or damage

11a. Drugs used in radiology II: anaesthetics and analgesics - Analgesics Flashcards

(104 cards)