Anaesthesia and anaesthetics

Question 1

How is regional and general anaesthetic administered

Answer 1

regional - intrathecal

general - inhilation / iv

Question 2

what does local/regional anaesthetic target?

what does general anaesthetic target?

Answer 2

L/R = afferent sensory reflex 
G =  central neural processing

Question 3

when would you use local anaesthetic

Answer 3

1. hand/foot/gum - suturing / dental procedures

Question 4

describe the mechanism for local anaesthetic

Answer 4

Weak bases - cross the membrane uncharged then ionise and block the channel
Lipid soluble/ uncharged - dissolves in the membrane and blocks the channel from within

Question 5

Lidocaine, Benzocaine, Tetracaine.. what type are they

Answer 5

lido = weak acid
benzo uncharged
tetra lipid sol

Question 6

Name the two types of regional anaesthetic and when you would use them

Answer 6

spinal - c section/ bladder surgery (subarachnoid)

epidural - child birth (epidural)

Question 7

What would you give if a patient is nervous for general anaesthetic and why would they be

Answer 7

patient stays awake - benzodiazepine

Question 8

what is bupivicaine and how would you administer it? how long would it last?

Answer 8

into epidural space at L4 - lasts 2-3 hours

Question 9

IV general anaesthetic describe the mode of action

1. Propofol, etomidate, thiopental (barb)
2. Ketamine

describe the 2 main types

Answer 9

1. at gaba receptor
2. blocks NMDA glutamate receptor

barbiturates ad non barbiturates

Question 10

inhilation GA - mechanism of action?

1. halothane isoflurane
2. nitrous oxide

Answer 10

1. volatile liquide - act on gaba receptor

2. inorganic gases - unclear

Question 11

Difference between

1. anaesthetic
2. hypnotic
3. tranquilliser

Answer 11

1. loss of consciousness, amnesia, inhib sensory reflexes, skm relax
2. induces sleep
3. eases anxiety WITHout causing sleep

Question 12

when would you want to put a patient in a medically induced coma

Answer 12

used to protect the brain following major neurosurgey

decreases E requirements of the brain and allows for healing and swelling to go down

Question 13

what is used to control a medically induced coma

Answer 13

barbiturates / propofol

Question 14

List the 5 main stages of anaesthesia

Answer 14

induction

1. analgesia
2. excitation
3. surgical anaethesia
4. medullary depression

Question 15

anaesthesia - induction ?

Answer 15

autonomic reflexes progressively depressed

control the airway, 02 levels, vent, and circilation

Question 16

anaesthesia - stage 1 ?

Answer 16

consciousness NOT lost - thoughts blurred
reflexes present
smell and pain lost by the end

Question 17

which stage of anaesthesia is child birth limited to ?

Answer 17

stage 1

Question 18

anaesthesia - stage 2?

Answer 18

become unconscious
comiting, temp control lost, EEG desynchronised, resp irreg, increased muscle tone, incoherent speech
DANGEROUS

Question 19

anaesthesia - stage 3?

Answer 19

slow synchronised EEG , reg slow breathing, reflexes lost, pupils dilates,

Question 20

anaesthesia - stage 4?

Answer 20

resp arrest, CV collapse, EEG small/ lost

death

Question 21

what is boyles apparatus used for?

Answer 21

inhilation anaesthesia

mixes 02 anaesthetic and ambient air

Question 22

pros of inhilation anaesthesia

Answer 22

Levels are easily controlled
Rapid elimination from body
Doesn’t cause post op resp depression
Few drug interactions

Question 23

why isnt halothane used?

Answer 23

toxic to liver

Question 24

what is MAC? what decreases MAC?

Answer 24

the minimum alveolar concentration - potency of inhailed anaesthetic
mix air with N20 and decreases MAC therefor need to use less anaesthetic

Question 25

Name 3 factors that alter MAC

Answer 25

n20
age
pregnancy (alcohol abuse, some drugs)

Question 26

describe the uptake of inhalation anaesthetics

Answer 26

lipid soluble molecules rapidly absorbed across pul memb, pass into blood into tissue, BBB freely permeable to GAs

Question 27

describe the elimination of inhalation anaesthetics

Answer 27

diffuses out of the brain into muscles and fat
inert therefor undergos little metabolism
eliminated via lungs
rate mirrors uptake

Question 28

problem with some inhalation anaesthetics during elimination

Answer 28

some are metabolised by liver and some metabolites are toxic

Question 29

how do inhaled anaesthetics cause anaesthesia

Answer 29

uncharged molecules conc in lipid membrants causing effects on the structure - membrane expansion! effects membrane spanning proteins e.g. ion channels

Question 30

how are inhilation anaesthesia reversed?

Answer 30

decompression chamber 200 ATM

Question 31

How long do iv anaesthetics last for?

Answer 31

20 minutes - short acting

Question 32

when is the ideal time to use IV anaesthetics in anaesthetics

Answer 32

induction - then maintain with GA

Question 33

negatives and 1 +ve to barbiturates

Answer 33

enter brain quickly,

no analgesia, small therapeutic window ,short lasting, slow metabolism, irritant , resp depression

Question 34

example of barbiturates

Answer 34

thiopentone

Question 35

1. examples of 2 non barbiturates used for GA

2. which causes neausea

Answer 35

ketamine and propofol

ketamine causes nausea on recovery

Question 36

2 main sites of action of general anaesthetics and why they target these areas

Answer 36

RAS - reticular activating system ( medullary area involved in sleep and wake)
hippocampus (inhibit Ach release - amnesic effects)

Question 37

what is the lipid theory in general anaesthesia

Answer 37

GAs potency directly correlates with lipid solubility (proposed)

Question 38

How to GAs work..

Answer 38

increased fluidity of membrane..
decrease NT release pre synaptically
decrease excitability post synaptically

Question 39

Name some side effects of GAs

Answer 39

vomiting
resp depression
drug interactions 
CV effects
renal failure
hepatotoxicity
malignant hyperpyrexia (release ca from skn, rigidity acidosis )