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Surgery sara > anaesthetics > Flashcards

anaesthetics Flashcards

1
Q

what are the different levels of anaesthesia?

A

local - one area sensation is loss
regional e.g. central nerve block (spinal or epidural)
sedation
general anaesthesia

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2
Q

what agents can be used for local anaesthetics?

A

lidocaine
procaine
bupivacaine

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3
Q

what does general anaesthesia involve?

A 
analgesia 
hypnosis 
relaxation - reduced reflexes and muscle relaxation 
amnesia
anxiolysis
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4
Q

Chloroform can achieve hypnosis, analgesia and paralysis alone so why don’t we just use this?

A

It is better to use multiple agents at a lower dose than one agent at a high dose. less side effects.

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5
Q

list some IV drugs that can be used to induce anaesthesia.

A

propofol - most common - rapid sedation induction
ketamine
midazolam
etomidate

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6
Q

list some inhaled agents used for induction of anaesthesia.

A

Desflurane
isoflurane
halothane

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7
Q

Briefly outline the steps taken when undergoing general anesthetics

A 
pre-assessment 
premedication
induction 
maintenance - usually switch to a volatile anaesthetic agent at this point. need to be continuously monitoring and adjusting e.g. phenylephrine to treat hypotension 
emergence 
recovery
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8
Q

during the induction phase of anaesthetics. what happens?

A 
check monitors are all working 
pre-oxygenate
IV induction usually with propofol 
analgesic - opioid
muscle relaxation to aid intubation/reduce movement - usually tubocurarine 
intubate
tape over eyes to protect them 
position to prevent sores/ how surgeon wants
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9
Q

what type of induction is mainly used and when do we use the other type of induction?

A

usually IV by propofol

but can use gas via airways instead if phobia of needles, non compliant child, poor vein access

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10
Q

what agent is mainly used for induction of anaesthetics?

A

propofol

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11
Q

why do we pre-oxygenate a patient before inducing anaesthesia?

A

allows more time to intubate and establish an airway.
normal air is 21% O2 so a patient will desaturate after 2 mins but if we give them 100% O2 before this extends the time frame to 10 mins

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12
Q

what agents are often used for muscle paralysis during anaesthesia? how do these work?

A

Tubocurarine - blocks nACHr

Succinylcholine - depolarising blocker of nACHr - accommodation

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13
Q

name 2 NMDA receptor antagonists

A

ketamine

N2O

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14
Q

how does propofol work?

A

increases GABAa chloride channel current by increasing sensitivity to GABA
positive allosteric modulation

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15
Q

what monitoring do we use throughout general anaesthesia?

A 
capnography  and airway gas's - most important
pulse oximetry
ECG
agent analyser 
BP
temperature  - malignant hyperpyrexia 
airway pressure

depending on surgery other things e.g. Doppler in carotid endartectomy

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16
Q

why is N20 a useful agent?

A

low potency but can be used in conjugation with other gents to lower the MAC of other agents. Therefore less side effects

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17
Q

How do you stop general anaesthesia?

A

withdraw anaesthetic agents / reverse them.
continue analgesics and anti-emetics
establish sustainable spontaneous respiration with good gas exchange
transfer to recovery

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18
Q

what agents can be used to reverse neuromuscular block?

A

Neostigmine - reverses neuromuscular blockage
however can lead to reduced HR and bronchoconstriction
therefore mix it with glycopyroate which counters these effects but does not cross BBB so neostigmine reverses the effects required.

19
Q

what are the stages of anaesthesia?

A
  1. analgesia and conscious
  2. unconscious, excitement, delirium, weird breathing
  3. surgical anaesthesia - reduced resp and CNS activity, muscle tone and reflexes
  4. severe medullary depression - resp and CNS depression - cardiac arrest and death.
20
Q

what are the advantages and disadvantages of total intravenous anaesthesia?

A

advantages - better recovery, better for neurosurgery, problems of N20 avoided

disadvantages - need secure IV access, may cause profound hypotension.

21
Q

what is the MAC?

A

minimum alveolar concentration…
the % of inhaled anaesthetic agent that 50% of patients will not respond to surgical incision

i.e. the lower it is, the more potent an anaesthetic

22
Q

what MAC value is usually used in practice?

A

very variable depending on individual and the surgery and the different anaesthetic agents used.

23
Q

what factors affect MAC?

A

use of multiple agents e.g. N20, opioids
elderly - lower MAC
infants - higher MAC
hypotension, hypothermia and hypothyroid - lower MAC
hyperthyroid, hyperthermia - increase MAC
stimulants alcohol and smoking - increase MAC
pregnancy - increases MAC

24
Q

1 MAC of sevoflurarane is 2.2 % what does this mean? how many MAC would you use?

A

at a concentration of 2.2% , 50% of people will not be responsive to surgical incision.

you would want to use 1.2-1.5 MAC to ensure all patients are not responsive. therefore would use 3%

however take into account individual and other agents which will agent adjust the MAC

if only old patients were tested 1 MAC of this agent may instead be 1.8% because elderly lowers MAC i.e. drug becomes more potent.

25
Q

what alters the speed of conduction of an anaesthetic agent?

A

how well it dissolves in blood or lipid. if it leaves blood to tissues it will induce anaesthesia fast. i.e. the better soluble in lipid the faster acting.

also the more lipid soluble the more potent because the more will leave into nerve cells across myelin and work.

26
Q

what are common post op complications related to anaesthesia?

A

PONV, sorethroat,

Pain: headache, itching, aches, bruising, soreness

confusion, shivering
chest infection, bladder problems.

less common: damage to lips, teeth, allergy, breathing difficulties, damage to eyes, nerve damage, death

27
Q

what are the main risks of anaesthesia?

A

reduced CO and low BP - shock

reduced resp rate

28
Q

list some common problems of fluranes

A

resp and CVS depression (reduced medulla activity)

arrhythmias and hypotension - due to reduced vascular resistance by direct effect on arterial smooth muscle

increased cerebral flow and therefore increased ICP due to vasodilation

malignant hyperthermia

isofluranes and desflurane are airway irritants and can lead to laryngospasm

29
Q

list the common problems of propofol

A

CVS and resp depression
propofol infusion syndrome (RARE) - impaired mitochondrial resp leading to metabolic acidosis, hyperkalaemia, rhabdomyolysis - can lead to cardiac arrest

30
Q

list the ADRs of N20

A

expansion of airway cavities - sinuses, middle ear, bowel

dangerous in pneumothorax

diffuses rapidly out of blood and rises in alveoli and therefore become temporarily hypoxic (problem if there is already resp problem)

31
Q

state an ADR of benzodiazepines

A

resp depression

32
Q

state an ADR of neuromuscular blockers

A

Apnoea therefore hypoxia

33
Q

list the roles of Anaesthetists

A 
I - intensive care
T - theatre 
A - anaesthetics
P - pain
S - sleep

including epidurals in obs and gynae

34
Q

state symptoms and signs of an allergy

A

symptoms: itching,sneezing, wheezing, tightness, swelling of face/airways, eyes watering, N and V and D, tingling, rash
signs: hypotension , pale and sweaty, tachypnoea , tachycardia

35
Q

what happens in the stress response to surgery? what factor can increase this response?

A

ADH and cortisol are secreted
ADH: fluid retention
Cortisol and aldosterone: sodium and fluid retention, potassium loss.

results in dehydration and electrolyte imbalances

Pain

36
Q

what are the indications for lignocaine/lidocaine and what are the contraindications?

A

indication: local anaesthetic, arrhythmias,
contraindications: heart block, WPW

37
Q

how does lignocaine/ lidocaine/ bupivacaine work?

A

blocks fast acting VG na channels in neuronal cell membrane preventing depolarisation of post synaptic neuron therefore no pain transmission.

in heart it can also do this making heart less likely to conduct early AP and thus prevents arrhythmias

all act on internal side of these channels.

38
Q

why is levobupivacaine often used over lidocaine?

A

levobupivacaine last longer

39
Q

what happens if local anaesthetic agent gets into blood in high concentrations? how is it treated?

A

can lead to seizures/arrhythmias - i.e. avoid vessels when giving local anaesthetic
Can give intralipid to mop this up

40
Q

what type of block is used for

a) shoulder
b) arm/elbow
c) hand

A

a) intrascalene
b) supraclavicular
c) axillary

41
Q

for intrascalene block, what structure do we need to be careful of?

A

phrenic nerve

42
Q

what are the indications for ITU?

A

patient needs close monitoring
needs support of more than one of their body functions e.g. ventilation and dialysis
large amount of blood loss in surgery etc

43
Q

when is ITU not indicated?

A

An individual is unlikely to gain much out of intensity of care e.g. incurable cancer. in this case palliative care is more appropriate

Surgery sara (10 decks)

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