Anaesthetic agents & analgesia Flashcards
Give two definitions of anaesthesia
what order do they work in the brain?
1) reversible drug induced absence of sensation and awareness
2) any lipid soluble agent that causes depression of the brain in a predictable order
cortex > midbrain > spinal cord > medulla
ETHANOL as an example
i) what is the first stage after a few drinks?
ii) what does this lead to?
iii) what happens before sedation
iv) what happens after sedation?
v) what happens after anaesthesia
i) tranquilisation
ii) leads to relaxation
iii) before sedation there is dysarthria and ataxia
v) after sedation there is anaesthesia
v) after anaesthesia there is coma, medullary depression and death
who perfomed the first recognised used on anaesthesia for an operation?
wiliam squire
how do anaesthetics work in relation to inhibitory and excitatory receptors?
give two examples of each of these
stimulate inhibitory receptors (GABA and glycine)
inhibit excitatory receptors (nicotinic, serotonergic and NMDA)
what interaction does an anaesthetic have on its target ion channel?
what does this cause?
interacs with the cell membrane gate which causes a conformational change
this causes an influx of chloride ions causing hyperpolarisation
INHALATIONAL AGENTS
i) how are they stored?
ii) are they flammable in storage?
iii) are they easy to vaporuise?
i) in a gas cyclinder
ii) not flammable
iii) easy to vapourise
NO
i) is it stored at high or low pressure?
ii) what is it mainly used for?
iii) is it used in anaesthesia? why?
iv) is it a cardiorespiratory depressant?
i) high pressure
ii) mainly used for analgesia
iii) not used in anaesthesia as min conc needed is 105% (MAC) and max you can give is 80%
iv) not a cardioresp depressant
what are the side effects of these older inhaled agents
i) ether
ii) chloroform
iii) cyclopropane
iv) methoxyflurane
v) halothane
vi) enflurane
i) sickness is main side effects
ii) caused dysrhythmias and death
iii) very effective but very explosive
iv) pre disposes to fits
v) toxic metabolites (hepatitis)
vi) pre disposed to fits
ISOFLURANE
i) give three advantages of this
ii) why is it not very good for gas induction?
iii) what are the side effects?
i) cheap, non flammable, easy to vapourise
ii) not good for gas induction as it is an irritant to the airway
iii) side effects are cardioresp depression
SEVOFLURANE
i) why is this relevant?
ii) is it good for gas induction?
iii) are the metabolites toxic?
iv) does it cause cardioresp depression?
v) what phenomena may occur after use?
i) the most commonly used inhaled agent
ii) non irritable so good for gas induction
iii) non toxic metabolites
iv) does cause cardioresp depression but less so than isoflurane
v) may cause emergence phenomena (wake up agitated)
DESFLURANE
i) give two advantages
ii) what is the main disadvantage?
iii) give two other disadvantages
i) quick on and offset and low side effects
ii) main disadv is that it is environmentally damaging
iii) other disadv are need a special vapouriser and can be in irritant
IV AGENTS
i) have they been around for a longer or shorter time than inhalational agents?
ii) what drug may they be given with?
iii) how quickly are you asleep?
iv) are they long or short acting? what causes this?
v) do they cause cardioresp depression?
i) shorter
ii) may be given with an opiate
iii) fall asleep v quickly 5-10 seconds
iv) short acting due to redistribution around the body
v) yes they cause cardioresp depression
THIOPENTONE
i) is it used now?
ii) what can it also be used for?
iii) give two negative things it can cause?
iv) what happens if its injected into an artery?
v) how long is the half life? what does this mean?
i) not really
ii) can also be used as an antiepileptic
iii) can cause anaphylaxis and cardioresp depress
iv) injected into an artery will cause it to crystallise and cut off the blood supply
v) 10 hours half life - hangs around in the body for a while
PROPOFOL
i) how commonly used is it?
ii) how long is the redistribution half life? what does this mean?
iii) how lipid soluble is it?
iv) what situation may it be used in?
v) name two other things it can be used for
vi) what are the side effects (4)
vii) which population of people may it not be suitable for? why?
i) most commonly used
ii) redist half life of 4 mins so you wake up quicklu
iii) very lipid soluble
iv) may be used in TIVA - maintaining patients on anaes on ITU
v) may also be used as an anti-emetic and anti-epileptic
vi) SEs - can be painful to inject (decreased by using a carrier agent or lignocaine alongside), abnormal movements when falling asleep, cardioresp depression, big drop in BP may occur
vii) may not be suitable for elderly due to it causing big drop in BP
what type of agent are ketamine, etomidate and midazolam?
IV agents
MUSCLE RELAXANTS
i) what do these cause?
ii) what may they be used to facilitate? (2)
iii) what are the two classes? give an example of each and how they act?
i) cause muscle paralysis
ii) may be used to facilitate intubation or paralysis during surgery
iii) two classes are depolarising and non depolarising
- depolarising act like Ach (mimic ach and block the receptor) eg suxamethonium
- non depol compete with Ach at the receptor eg rocuronium or benzylqunilinium
are depolarising or non depolarising muscle relaxants most commonly used now?
which type has a quicker on and offset?
which type mimicks Ach? which type competes with it?
non depolarising are mostly used now
depolarising have quicker on and offset
depol mimic ach and non depol compete with ach
PAIN LADDER
i) what is the first line pain relief normally given? give two examples
ii) what two agents are given second line? give an example of each
iii) what is the last line of treatment given? give three examples
iv) is tramadol weak or strong?
i) NSAIDs (ibuprofen) or paracetamol
ii) weak opiate (codeine) or local anaes (lidocaine)
iii) strong opiates (morphine, oxycodone, fentanyl)
iv) in the middle of strong and weak
OPIOIDS
give an example of
i) naturally occuring
ii) semi synthetic
iii) synthetic
iv) what antagonises these drugs?
i) morphine and codeine
ii) diamorphine
iii) fentanyl
iv) naloxone antagonises
what are the main side effects of morphine? (5)
constipation, resp depression, nausea and vom, pruritis (itching), miosis (excess pupil constric)
KETAMINE
i) what receptors does it work at? what action does it have here?
ii) what can it be used for?
iii) give one side effect
i) works on NMDA receptors - antagonist
ii) used for analgesia, anaesthetic and sedation
iii) side effect = emergence phenomena
NSAIDS
i) how do they work?
ii) what can they be used for?
iii) give three side effects
iv) what effect do they have on platelets? which drug does this?
i) inhibit COX1 and COX 2
ii) used for analgesia, antipyrexia and anti-inflammation
iii) side effects are gastric irritation, bronchospasm, renal impairment, cardiac issues
iv) inhibit plat aggregation - aspirin
what syndrome may arise when aspirin is given to children? what happens here?
Reyes syndrome - makes metabolic rate go very high which can cause renal failure
PARACETAMOL
i) what is its mechanism of action?
ii) what is the made side effect?
iii) what can be given to counteract an overdose?
i) unknown - probably central and on prostaglandins
ii) overdose is main side effects - hepatotoxicity
iii) treat with N acetylcysteine which binds paracetamol
name five types of analgesia (not NSAID/paracet)
anxiolysis (anxiety can make pain worse)
local anaes
anti depressants
acupunctire
inhaled NO (can make a pneumothorax bigger)
tramadol
SEDATION
i) are you still concious?
ii) does the patient respond to commands?
iii) do they respond to glabellar tap/shouting?
i) yes still concious
ii) yes responds to commands
iii) yes responds to glabellar tap (tap forehead and should see blinking)
BENZODIAZEPENES
i) what are they mainly used for?
ii) give two examples
iii) what receptor do they bind and what action do they have?
iv) give three side effects
v) what can be used to reverse the effects?
i) mainly used for sedation
ii) midazolam and diazepam
iii) agonise GABA receptors (cause inhibition)
iv) over sedation, loss of airway and resp depress
v) flumazanyl (use with caution)
LOCAL ANAESTHETICS
i) give three examples
ii) how do they work? (which channel do they work on) what does this cause?
iii) give three possible toxicities
i) lignocaine, prilocaine and cocaine
ii) Na+ channel blockers - blocks the action potentia
iii) CV - dysrhytmias and cardiac depress
CNS - fitting, anx, loss of conc
