Drugs

Question 1

What IV induction agents are used in anaesthetics?

Answer 1

-Propofol
-Thiopentine
-Etomidate
-Ketamine

Question 2

What are the main and positive features of propofol?

Answer 2

-Most commonly used inducted agent
-Lipid-based, white
-Excellent at SUPPRESSING AIRWAY REFLEXES
-Decreases incidence of PONV

Question 3

What are the negative effects of propofol?

Answer 3

-Causes a marked drop in BP and HR
-Can cause involuntary movements

Question 4

What are the main features of thiopentine?

Answer 4

-A barbiturate
-Has a faster onset of action than propofol
-Used mainly in RAPID SEQUENCE INDUCTION
-Has anti-epileptic properties and PROTECTS THE BRAIN

Question 5

What are some negative effects of thiopentine?

Answer 5

-Drops BP but increases HR
-Can cause a rash / bronchospasm
-Contraindicated in prophyria

Question 6

What are the main features of etomidate?

Answer 6

-Rapid onset
-LOWEST INCIDENCE OF HYPERSENSITIVITY REACTION

Question 7

What are some negative effects of etomidate?

Answer 7

-Spontaneous movements
-High incidence of PONV

Question 8

What are the main features of ketamine?

Answer 8

-Causes DISSOCIATIVE ANAESTHESIA (anterograde amnesia + profound analgesia)
-Slow onset (90 seconds)

Question 9

What are the negative effects of ketamine?

Answer 9

-Rise in HR and BP
-N+V
-Vivid dreams, hallucinations

Question 10

What are the dose ranges for IV induction agents?

Answer 10

-Etomidate = 0.2-0.3mg/kg
-Ketamine = 1-1.5mg/kg
-Propofol = 1.5-2.5mg/kg
-Thiopentine = 4-5mg/kg

Question 11

What inhalational anaesthetics are there?

Answer 11

-Sevoflurane
-Desflurane
-Isoflurane

Question 12

What are the main features of each inhalational agent?

Answer 12

-Sevoflurane = sweet smelling
-Desflurane = low lipid solubility, rapid onset and offset, good for long operations
-Isoflurane = least effect on organ blood flow

Question 13

What is the difference between depolarising and non-depolarising neuromuscular blockers?

Answer 13

DEPOLARISING = act on nicotinic receptors and are very slowly hydrolysed by acetylcholinesterase, causing muscle to contract, then fatigue and relax
NON-DEPOLARISING = block the nicotinic receptors, causing the muscle to relax

Question 14

What are examples of procedures where neuromuscular blockers would be used?

Answer 14

-Mid-line laparotomy (paralysis of abdominal muscles)
-ENT operations (relaxation of vocal cords)

Question 15

What are the features of depolarising NMBs?

Answer 15

-SUXAMETHONIUM is main one
-Has a rapid onset and offset
-Used in rapid sequence induction
-Adverse features = muscle pains, fasciculations, malignant hyperthermia, suxamethonium apnoea

Question 16

What are the features of non-depolarising NMBs?

Answer 16

-Slow onset and variable duration
-Less SEs
-Compete with ACh for receptors
-Reversal by geostimine and glycopyrrolate

Question 17

What are examples of non-depolarising NBMs and how are they categorised?

Answer 17

-Short-acting = atracurium, mivacurium
-Intermediate-acting = vecuronium, rocuronium
-Long-acting = pancuronium

Question 18

What is neostigmine and how does it work?

Answer 18

-Reversal agent
-An anti-cholinesterase, prevents breakdown of ACh
-Combined with anti-muscarinic agent glycopyrrolate

Question 19

What anti-emetics are commonly used in anaesthesia?

Answer 19

-Ondansetron (most commonly used) = 5HT3 blocker
-Cyclizine = antihistamine
-Dexamethasone = steroid
-Metaclopramide, haloperidol = anti-dopaminergic

Question 20

What analgesics are used in anaesthetics?

Answer 20

-Opioids
-Morphine
-Paracetamol

Question 21

What is the process of general anaesthesia?

Answer 21

1. Arrival
2. Monitoring
3. IV access
4. Induction of anaesthesia –> analgesia, muscle relaxation
5. Maintenance of amnesia, analgesia, muscle relaxation and replacement of fluid / blood
6. Reverse muscle relaxation but maintain post-op analgesia
7. Transfer to recovery

Question 22

What are ephedrine, phenylephrine and metaraminol and how do they work?

Answer 22

-Vaso-active drugs causing rise in BP
-EPHEDRINE = rise in HR and heart contractility causing a rise in BP
-Phenylephrine = vasoconstriction causes rise in BP and drop in HR
-Metaraminol = vasoconstriction causes rise in BP

Question 23

Where can you do a spinal block?

Answer 23

-Aiming for subarachnoid space but avoiding spinal cord
-Between L2 and S2
(spinal cord ends in lower border of L1, subarachnoid space ends at S1)

Question 24

Where can you do an epidural injection?

Answer 24

-Aiming for epidural space but want to minimise risk of damage to spinal cord
-Below L1 reduces risk
-For labour analgesia = done at same level as spinal
-For laparotomy = done at thoracic level

Question 25

Why are neuraxial blocks preferred over opioids?

Answer 25

-Better for those with respiratory disease - painful wounds may cause reduced lung expansion and increased risk of post-op respiratory depression
-IV analgesics are less desirable for those with obstructive sleep apnoea and PONV

Question 26

What safe doses of local anaesthetic are used?

Answer 26

-Lignocaine (0.5 and 1%) without adrenaline = 3mg/kg
-Lignocaine with adrenaline = 7mg/kg
-Bupivicaine (0.25 and 0.5%) = 2mg/kg

Question 27

How do you calculate a maximum dose in ml for a patient?

Answer 27

-Recommended dose x weight / concx10
-Eg lignocaine without adrenaline 0.5% for a 65kg man = 3x65 / 0.5x10

Question 28

What are the signs and symptoms of local anaesthetic toxicity?

Answer 28

-Numbness around the mouth, tongue paraesthesia
-Dizziness
-Restlessness and agitation –> CNS depression
-Muscle twitching
-Respiratory arrest
-Cardiac arrhythmias