Drugs Used for the Induction of Anaesthesia

Question 1

What are the aims of anaesthetics?

Answer 1

Amnesia
Analgesia
+/- muscle relaxation

Question 2

What are the phases of general anaesthesia?

Answer 2

Induction
Maintenance
Emergence

Question 3

What apparatus is used in spontaneous ventilation?

Answer 3

Laryngeal mask airway (LMA)

Question 4

In which patients is spontaneous ventilation used?

Answer 4

Those with minimal aspiration risk

Question 5

What apparatus is used in intermittent positive pressure ventilation (IPPV)?

Answer 5

Endotracheal tube (ETT)

Question 6

In which patients is IPPV used?

Answer 6

Those with minimal aspiration risk, and

• Muscle relaxant needed for surgery
• Intra-abdominal pathology
• Obesity
• Shared airway
• Prone position
• Long procedure

Question 7

For whom is rapid sequence induction used?

Answer 7

Those at high risk of gastric aspiration; eg:

• Pregnancy
• Unfasted patients (SBO)

Question 8

What is the most common agent used to induce general anaesthesia?

Answer 8

Propofol

Question 9

What is the onset and offset of propofol?

Answer 9

Short

Question 10

What is the post-anaesthesia effect of propofol?

Answer 10

Smooth wake-up

No hangover effect

Question 11

What is the mechanism of action of propofol?

Answer 11

Potentiates action of GABA receptors > inhibits neurotransmission

Question 12

What is the metabolism of propofol?

Answer 12

Mostly hepatic metabolism

- Liver dysfunction doesn’t change dose

Question 13

What are the central nervous system effects of propofol?

Answer 13

Sedation
Induces general anaesthesia
No analgesia

Question 14

What are the cardiovascular effects of propofol?

Answer 14

Decreases MAP

Question 15

What are the respiratory effects of propofol?

Answer 15

Dose dependent ventilation depression
Apnoea in 25-30%
Decreased response to hypoxia
Decreased laryngeal and pharyngeal reflexes

Question 16

What are the other effects of propofol?

Answer 16

Anticonvulsant (potential)
Anti-emetic
Antipruritic
Pain on injection

Question 17

What is the mechanism of action of ketamine?

Answer 17

NMDA receptor antagonists

Question 18

What is the metabolism of ketamine?

Answer 18

Hepatic

Question 19

What is the excretion of ketamine?

Answer 19

Renal

Question 20

What are the central nervous system effects of ketamine?

Answer 20

Dissociative amnesia
Disconnects cortical and limbic system
Intense analgesia
Emergence delirium
Cerebral vasodilator
- Don't use in head injury because increases ICP

Question 21

What are the cardiovascular effects of ketamine?

Answer 21

Increases

• MAP
• HR
• CO

Question 22

What are the respiratory effects of ketamine?

Answer 22

No airway depression

Airway irritant > increased secretions and salivation

Question 23

What are the analgesic uses of ketamine?

Answer 23

Chronic pain management

Question 24

In which patients is ketamine useful for in the induction of anaesthesia?

Answer 24

Haemodynamically unstable patients

Question 25

What is the drug class of fentanyl?

Answer 25

Synthetic opioid

Question 26

What is the metabolism of fentanyl?

Answer 26

Hepatic

Question 27

What are the central nervous system effects of fentanyl?

Answer 27

Analgesia
Euphoria/dysphoria
Sedation

Question 28

What are the respiratory effects of fentanyl?

Answer 28

Respiratory depression
Depressed airway reflexes
Reduces response to hypercapnia/hypoxia

Question 29

What are the cardiovascular effects of fentanyl?

Answer 29

Decreased HR

Question 30

What are the other effects of fentanyl?

Answer 30

Itch

Constipation

Question 31

What are the five actions of benzodiazepines?

Answer 31

Anxiolysis
Sedation
Retrograde amnesia
Anticonvulsant activity
Muscle relaxant

Question 32

What is the drug class of midazolam?

Answer 32

Benzodiazepine

Question 33

When is midazolam used?

Answer 33

Anxiolysis prior to induction of anaesthesia

Can be used as adjunct to opioids and propanol for sedation