Anaesthetic Drugs

Question 1

Propofol

• drug type
• dose
• uses

Answer 1

IV induction agent

1.5-2.5mg/kg

Question 2

Propofol pros and cons

Answer 2

Pros;

• suppresses airway reflexes well (prevents laryngospasm)
• low PONV

Cons:

• drop in HR/BP
• pain on injection
• involuntary movements

Question 3

Thiopentone

• drug type
• dose
• uses

Answer 3

IV induction agent

4-5mg/kg

Quick acting, used for rapid-sequence induction

Question 4

Thiopentone pros and cons

Answer 4

Pros;

• Protects brain by reducing O2 demand (anti-epileptic properties)
• rapid acting

Cons;

• hypotension
• apnoea
• myoclonus
• rash, bronchospasm

Question 5

Ketamine

• drug type
• dose
• uses

Answer 5

IV induction agent

1-1.5mg/kg

Dissosicative anaesthesia, producing anterograde amnesia

Question 6

Ketamine pros and cons

Answer 6

Pros

• amnesia = good for short procedures
• good if haemodynamically unstable as sympathetic stimulation causes rise in HR and BP

Cons

• slower onset (90 seconds)
• emergence phenomenon (hallucinations)

Question 7

Etomidate

• drug type
• dose
• uses

Answer 7

IV induction agent

0./3mg/kg

Question 8

Etomidate pros and cons

Answer 8

Pros:

• rapid onset
• keeps BP/HR stable

Cons

• pain on injection
• spontaneous movement
• PONV
• adreno-corticol suppression for 7 hours

Question 9

MAC definition

Answer 9

1 MAC = concentration of vapour which prevents reaction to a standard surgical stimulus in 50% of subjects

100% amnesia

Lower the MAC = more potent agent

Question 10

Isoflurane

Answer 10

Inhalation/maintenance anaesthetic

Least effect on organ blood flow, so used for organ transplants

Question 11

Sevoflurane

Answer 11

Used for inhalation induction if IV access not possible (e.g. children)

Sweet smelling

Question 12

Desflurane

Answer 12

Inhalation/maintenance anaesthetic

Used on longer operations as less accumulates in the fat.

Rapid onset and offset

Question 13

Depolarising muscle relaxant MOA

Answer 13

Ach agonist
- bind to nicotinic receptors on post-synaptic cleft and cause muscle contraction

SLOWLY hydrolysed by acetylcholinesterase
- muscle contraction THEN fatigue and relaxation

Question 14

Suxamethonium

• drug type
• dose
• use

Answer 14

Depolarising muscle relaxant

1-1.5mg/kg

Rapid sequence induction (rapid onset and offset)
- lasts 4-10 mins

Question 15

Cons of suxamethonium

Answer 15

• muscle pain
• fasciculations
• hyperkalaemia (due to breakdown of muscle fibres)

MALIGNANT HYPERTHERMIA = fever, HTN, muscle spasm, acidosis and arrhythmias

SUZAMETHONIUM APNOEA = prolonged effects due to inability to break down drug

IRREVERSIBLE

Question 16

Non-depolarising muscle relaxant MOA

pros and cons

Answer 16

Nicotinic receptor antagonist

• prevent Ach binding at post-synaptic cleft
• prevents muscle contraction

pros = less side effects

cons = slow onset, variable duration

Question 17

Examples of non-depolarising muscle relaxant

Answer 17

• Short acting (15 mins) = mivacurium
• Medium acting (20-60 mins) = vecuronium, rocuronium, atracurium
• Long acting (60 mins) = pancuronium

Question 18

Neostigmine + glycopyrolate

Answer 18

REVERSAL OF NON-DEPOLARIISNG MUSCLE RELAXANT

Neostigmine = anti-cholinesterase, so increases Ach at neuromuscular junction, returning muscle function

Glycopyrolate = anti-muscarinic to be given alongside to reverse muscarinic effects of Ach

Question 19

Sugammadex

Answer 19

REVERSAL OF NON-DEPOLARISING MUSCLE RELAXANT

Reduced concentration of non-depolarising relaxant by forming water soluble complex with it.

Question 20

Inotropes indications in anaesthesia

• MOA
• example

Answer 20

Hypotension

Increase HR and contractility, so increase BP

e.g. edhedrine

Question 21

Local anaesthetic MOA

Answer 21

Inhibits voltage gated Na+ channels

Prevents propagation of action potential along nerve axon

Sensory information does not reach the brain

Question 22

Esters

Answer 22

Local anaesthetics more likely to cause allergic reaction.
They are less stable and less commonly used

ONE i in name
- e.g. cocaine, procaine, benzocaine

Question 23

Amides

Answer 23

Local anaesthetics more commonly used

TWO i’s in name
- e.g. bupivacaine, lignocaine

Question 24

Local anaesthetic doses with/without adrenaline

• lignocaine
• bupivacaine
• prilocaine

Answer 24

WITHOUT:

• Lignocaine = 3mg/kg
• Bupivacaine = 2mg/kg
• Prilocaine = 6mg/kg

WITH:

• Lignocaine = 7mg/kg
• Bupivacaine = 2mg/kg (same)
• Prilocaine = 9mg/kg

Question 25

Management of anaesthesia induced N+V

Answer 25

Prophylaxis = ondansetron

Peri-operative = dexamethasone

Post-operative = ensure one is prescribed during handover (e.g. cyclizine)

Question 26

Stop COCP how long before anaesthetics

Answer 26

4 weeks + for 2 weeks after

Question 27

Stop warfarin how long before anaesthetics

Answer 27

5 days

Replace with heparin for up to 4 hours before

Question 28

stop DOACs how long before anaesthetics

Answer 28

24-48 hours

Question 29

stop ACEi how long before anaesthetics

Answer 29

avoid on morning of

DO NOT NEED TO AVOID BB

Question 30

Stop aspirin/clopidogrel how long before anaesthetics

Answer 30

7 days

Question 31

Eating and drinking rules before anaesthetics

Answer 31

Food/milk containing drinks = 6 hours before

Breast milk = 4 hours before

Clear fluids = 2 hours before (1 hour for children)

Alcohol = 24 hours before

Advise to avoid boiled sweets/gum