anaesthetics

Question 1

what are the different levels of anaesthesia?

Answer 1

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

Question 2

what agents can be used for local anaesthetics?

Answer 2

lidocaine
procaine
bupivacaine

Question 3

what does general anaesthesia involve?

Answer 3

analgesia 
hypnosis 
relaxation - reduced reflexes and muscle relaxation 
amnesia
anxiolysis

Question 4

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

Answer 4

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

Question 5

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

Answer 5

propofol - most common - rapid sedation induction
ketamine
midazolam
etomidate

Question 6

list some inhaled agents used for induction of anaesthesia.

Answer 6

Desflurane
isoflurane
halothane

Question 7

Briefly outline the steps taken when undergoing general anesthetics

Answer 7

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

Question 8

during the induction phase of anaesthetics. what happens?

Answer 8

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

Question 9

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

Answer 9

usually IV by propofol

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

Question 10

what agent is mainly used for induction of anaesthetics?

Answer 10

propofol

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Tubocurarine - blocks nACHr

Succinylcholine - depolarising blocker of nACHr - accommodation

Question 13

name 2 NMDA receptor antagonists

Answer 13

ketamine

N2O

Question 14

how does propofol work?

Answer 14

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

Question 15

what monitoring do we use throughout general anaesthesia?

Answer 15

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

Question 16

why is N20 a useful agent?

Answer 16

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

Question 17

How do you stop general anaesthesia?

Answer 17

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

Question 18

what agents can be used to reverse neuromuscular block?

Answer 18

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.

Question 19

what are the stages of anaesthesia?

Answer 19

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.

Question 20

what are the advantages and disadvantages of total intravenous anaesthesia?

Answer 20

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

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

Question 21

what is the MAC?

Answer 21

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

Question 22

what MAC value is usually used in practice?

Answer 22

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

Question 23

what factors affect MAC?

Answer 23

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

Question 24

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

Answer 24

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.

Question 25

what alters the speed of conduction of an anaesthetic agent?

Answer 25

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.

Question 26

what are common post op complications related to anaesthesia?

Answer 26

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

Question 27

what are the main risks of anaesthesia?

Answer 27

reduced CO and low BP - shock | reduced resp rate

Question 28

list some common problems of fluranes

Answer 28

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

Question 29

list the common problems of propofol

Answer 29

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

Question 30

list the ADRs of N20

Answer 30

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)

Question 31

state an ADR of benzodiazepines

Answer 31

resp depression

Question 32

state an ADR of neuromuscular blockers

Answer 32

Apnoea therefore hypoxia

Question 33

list the roles of Anaesthetists

Answer 33

``` I - intensive care T - theatre A - anaesthetics P - pain S - sleep ``` including epidurals in obs and gynae

Question 34

state symptoms and signs of an allergy

Answer 34

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

Question 35

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

Answer 35

ADH and cortisol are secreted ADH: fluid retention Cortisol and aldosterone: sodium and fluid retention, potassium loss. results in dehydration and electrolyte imbalances Pain

Question 36

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

Answer 36

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

Question 37

how does lignocaine/ lidocaine/ bupivacaine work?

Answer 37

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.

Question 38

why is levobupivacaine often used over lidocaine?

Answer 38

levobupivacaine last longer

Question 39

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

Answer 39

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

Question 40

what type of block is used for a) shoulder b) arm/elbow c) hand

Answer 40

a) intrascalene b) supraclavicular c) axillary

Question 41

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

Answer 41

phrenic nerve

Question 42

what are the indications for ITU?

Answer 42

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

Question 43

when is ITU not indicated?

Answer 43

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