Anaesthesia

Question 1

Name 4 Drugs given IV for general anaesthesia

Answer 1

Propofol
Ketamine
Barbiturates
Etomidate

Question 2

Name 5 inhaled anaesthetics used for general anaesthesia

Answer 2

Sevoflurane
Desflurane 
Isoflurane
Xenon
Nitrous oxide

Question 3

What is concious sedation?

Answer 3

Where a small amount of anaesthetic/benzodiazepines are used to create a sleepy state where the patient is concious but comfortable.

Question 4

Name the two ways general anaesthetics work

Answer 4

By enhancing inhibitory signals (activating GABA)

By inhibiting excitatory signals (inhibiting glutamate/NMDA)

Question 5

List 2 general anaesthetic that works by activating GABA

Answer 5

Propofol

Barbiturates

Question 6

List 3 general anaesthetics that work by inhibiting glutamate/NMDA

Answer 6

Ketamine
Nitrous Oxide
Xenon

Question 7

What are the 5 steps in anaesthesia, excluding end of procedure anaesthesia?

Answer 7

1) pre medication- (send you to sleep) usually benzo eg Lorazepam
2) induction (usually IV)
3) intra-operative analgesia (usually opioid)
4) muscle paralysis (allows to intubation)
5) maintenance (IV or inhalation)

Question 8

What two steps of anaesthesia are at the end of a procedure?

Answer 8

1) reversal of muscle paralysis

2) provision for post op N+V and analgesia

Question 9

What is MAC? (Minimum alveolar concentration)?

Answer 9

Alveolar concentration at which 50% of patients fail to move to stimuli (where [alveolar] = [spinal cord])

Question 10

List 7 things that can affect MAC and their effect

Answer 10

Age (infants have higher MAC, elderly have lower)
Temperature (hyper increases, hypo decreases)
Alcohol (increases MAC)
Pregnancy (increases MAC)
Central Stimulants (increases MAC)
Other anaesthetics/sedatives (decrease MAC)
Opioids (increase MAC)

Question 11

What can you use to decrease MAC? (Meaning you can use lower doses of anaesthetic)

Answer 11

Using N2O instead of O2 allows MAC to decrease

Question 12

What brain circuits are being targeted by general anaesthesia?

Answer 12

Reticular formation
Brainstem (therefore decreases resp and cvs drive)
Analgesia depresses anterior horn and motor neuronal activity

Question 13

What are the 4 levels of anaesthesia? (Guedes sign)

Answer 13

1) analgesia- normal muscle tone, analgesia but concious
2) excitement is a short phase, not always seen. Muscle tone is normal or increased, breathing can be erratic.
3) surgical anaesthesia (has 4 levels from slightly relaxed to markedly with weak breathing and no eye movements)
4) respiratory paralysis- flaccid and no breathing or eye movements

Question 14

What level of anaesthesia is regularly not seen? Why? And what are the features?

Answer 14

Excitement phase (2nd)
Usually too quick to be seen
Erratic breathing, normal to increased muscle tone.

Question 15

Name 5 local anaesthetics

Answer 15

Amide- lignocaine, bupivicaine, prilocaine, procaine

Ester- cocaine, amethocaine

Question 16

Why are amide anaesthetics better than Ester?

Answer 16

They have a stronger bond and are heat stable and so more stable and so last longer.
Also Ester anaesthetics when metabolised result in PABA production, which can cause allergy.

Question 17

In what state can local anaesthetics cross the cell membrane?

Answer 17

Unionised

Question 18

In which state, acidosis or alkalosis, does the local anaesthetic last longer?

Answer 18

Alkalosis

If patient is more acidotic, LA becomes ionised very quickly and therefore ineffective

Question 19

Why are local anaesthetics given with adrenaline?

Answer 19

Many LAs have vasodilator effects which therefore increases systemic absorption (rather than local).
Adrenaline is a vasoconstrictor.

Question 20

Where shouldn’t you deliver local anaesthetics with adrenaline?

Answer 20

Small digits due to risk of ischaemic necrosis due to vasoconstrictor effects of adrenaline.
Need to aspirate first to check not in vein/artery.

Question 21

How are local anaesthetic metabolised?

Answer 21

Esters: metabolised quickly by plasma esterases
Amides: metabolised in liver

Question 22

Why does bupivicaine have a longer duration of action?

Answer 22

It is more proteinbound therefore has a longer duration of action as drug is made available for metabolism more slowly.