GA Flashcards
what is the triad of GA use
hypnosis, amnesia and analgesia
what are the 3 components of balanced anaesthesia
pain relief, unconsciousness, inhibition of reflex
what is the most commonly used class of drug for analgesia
opioid and NO
what is the most commonly used class of drug for induction of anaesthesia
short acting barbiturates
what is the most commonly used class of drug for muscle relaxation
NM blockigjn agents
inhalant GA: the ____ the solubility, the slower the onset
higher
what is the proposed MOA for inhalation GA
enhance neurotransmission at inhibitory synapses via allosterically increasing GABA receptor sensitivity to GABA
depress neurotransmission at excitatory synapses via blocking glutamate neurotransmitter acting on NMDA receptor–> prevent NMDA receptor activation
low MAC = ____ anaesthetic potency
high
what is MAC
minimum conc of drug in air needed to produce immobility in 50% of patients exposed to painful stimulus
MAC values alter with…
age, condition, conçoivent administration of other drug
to produce therapeutic effect, inhalation anaesthetic has to reach CNS concentration enough to suppress
neuronal excitability
3 factors affecting rate of inhalation GA uptake into the blood
blood flow to the lungs
solubility of GA
conc of anaesthetic in the air
elimination of inhaled GA is through
lungs
minimal hepatic metabolism
which inhalation GA have nephrotoxic metabolites
isoflurane, enflurane
does halothane have analgesia before unconsciousness
no
does halothane have respiratory depression
yes; dose dependent
Halothane ____ BP due to depression of cardiac output
decreases
halothane: ____ and ____ may also occur –> hypotension and dysrhythmia
bradycardia and arrhythmia
halothane relaxes ____ muscles and potentiates _____
skeletal
potentiates skeletal muscle relaxants
halothane: may lead to ___________
halothane associated hepatitis
isoflurane has a ____ smell
pungent
isoflurane has a ____ rate of onset and recovery
medium
What is the advantage of isoflurane vs halothane
less hypotension and arrhythmia
how does isoflurane decrease BP
decrease in systemic vascular resistance
sevoflurane has a ____ rate of onset and recovery
rapid
seveflurane is metabolised in the ___ ti release _____________- which is nephrotoxic
liver
inorganic fluoride
sevoflurane is unstable when exposed to _____ in anaesthetic machines –> metabolite is potentially _______
CO2 absorbants
nephrotoxic
NO gives ___ and _____ but not complete ____ or surgical anaesthesia
analgesia and amnesia
unconsciousness
what is the function of NO
supplement the analgesic effect of primary anaesthetic
what is the major concern of NO
post op nausea and vomiting
name 5 IV GA
thiopentone 4-7mg.kg etomidate 0.2-0.3mg/kg propofol 2-4mg/kg ketamine 1.5mg/kg midazolam 0.02mg/kg
what are IV GA agents used for
induce unconsciousness
what is the caution with IV GA
depress respiration
advantages of inhaled + IV anaesthetics
- permit dosage of the inhalation agent to be reduced
2. produce effects that cannot be achieved with an inhalation alone
Class of thiopentone
barbiturate
thiopentone has ________ lipid solubility
extremely high
thiopentone enters the brain _________
onset of action _________
easily and rapidly
rapid (10-20 s after IV)
single dose of thiopentone redistributes to _______ tissue in ______ duration of action
less vascularised
ultra-short
patients wake up in 10 min
multiple doses/infusionsof thiopentone: duration of action depends on __
clearance
thiopentone has a ____ elimination, ____ Vd, ____ metabolite (______)
slow, large, active, pentobarbital
thiopentone: liver cirrhosis can result in _________
prolongation of clinical action
thiopentone is extensive bound to ______
plasma protein
thiopentone MOA
CNS depression by potentiating the action of GABA on the GABAa receptor-gated chloride ion channels
does propofol need to be reconstituted
no
induction rate of propofol is ____ to thiopentone and recovery is ____
similar, more rapid
what is propofol used for
induction and maintenance
onset of propofol
rapid (unconsciousness within 60 seconds)
duration of action of propofol
short (3-5min)
propofol most used in _______
day surgery
propofol needs _______ for extended effect
continuous, low dose infusion
advantage of propofol
reduced post op vomiting
disadvantage of propofol
significant CV effect during induction (decrease bp and negative inotropic)
caution when using propofol
caution in elderly patients, patients with compromised cardiac function, hypovolemic patients
ketamine exists as a __________ preparation
racemic
katmine produces a state known as _________
dissociative anaesthesia
ketamine can cause (4)
sedation, immobility, analgesia and amnesia
ketamine has ____ induction
rapid
ketamine is metabolised in ___ to _____________ metabolite, excreted in ________________
liver, less active metabolite
urine and bile
ketamine has ___ Vd, ___ clearance –> suitable for _______________ without the lengthening in duration of action
large Vd, rapid clearance, continuous infusion
SE of ketamine
unpleasant psychologic reactions (hallucination, disturbing dreams, delirium) during recovery
risk of psychologic adverse reactions –> may be reduced with premedication of diazepam or midazolam
does ketamine possess analgesia?
yes
name 4 classes of anaesthetic adjuncts / post op care
benzo, alpha adrenergic agonist, analgesics, NM blocking agents
name the benzodiazepine used for GA
midazolam IV
what is midazolam used for in GA
anxiolytics, amnesia and sedation prior to induction of anaesthesia or used for sedation during procedures not requiring GA
midazolam onsent
rapid
unconsciousness in 80s
peak 2 min
midazolam duration of action
sedates about 30 min when used by itself
midazolam metabolism
liver
elderly more sensitive slower recovery
midazolam TI high or low
high
why is midazolam TI high
less CV and resp depressing effect compared to other IV anaesthetics
midazolam SE compounded by………..
concurrent use of other agents
midazolam ADR can be minimised by……
injecting slowly over 2 or more minutes, waiting 2 minutes then doing it again
alpha 2 adrenergic example drug
dexmedetomidine
dexmedetomidine selective?
yes
dexmedetomidine duration of sedation
short term <24h
what effects does dexmedetomidine have
sedation and analgesia
does not produce reliable GA even at max doses
dexmedetomidine resp depression?
little
dexmedetomidine effect on bp and hr?
tolerable decrease
dexmedetomidine ADR
nausea
dry mouth
hypotension
bradycardia
what class of drugs is used for analgesia in GA
NSAIDs and opioids
when are NSAIDs used in GA
minor surgical procedures
which types of NSAIDs are used
COX-2 inhibitors and paracetamol
when are opioids used
perioperative period
opioids site of action for GA
mu
which drug has a relative potency of 1000x compared to morphine
duration of action
sufentanil
~15min
which drug has a relative potency of 300x compared to morphine
duration of action
remifentanil
~10 min
which drug has a relative potency of 80x compared to morphine
duration of action
fentanyl
~30min
which drug has a relative potency of 15x compared to morphine
duration of action
alfentanil
~20min
analgesics in GA metabolised through….. except _______
liver
remifentanil –> hydrolysed by tissue and plasma esterase’s
analgesics excretion
urine, bile
name a depolarising NM blocker
succinylcholine
name a non-depolarising NM blocker
vecuronium
when are NM blockers used
induction of anaesthesia to relax muscles of jaw, neck and airway –> facilitate laryngoscopy and endotracheal intubation
advantage of NM blockers
aids surgical procedures and additional insurance of immobility
precaution for NM blockers and barbiturates
ppt when mixed –> clear from IV line first
