Intro To Anaesthetics

Question 1

Types of anaesthesia

Answer 1

• General: inhalational/volatile or IV
• Local: regional

Question 2

What is conscious sedation

Answer 2

Use of small amounts of anaesthetics or benzodiazepines to produce a sleepy like state

Question 3

Routes of general anaesthesia

Answer 3

Inhalational/volatile
IV

Question 4

Examples of IV general anaesthesia

Answer 4

Propofol
Barbiturates
Etomidate
Ketamine

Question 5

What is anaesthesia a combination of?

Answer 5

• Analgesia
• Hypnosis (loss of consciousness)
• Depression of spinal reflexes
• Muscle relaxation

Question 6

What drug is normally used as premedication anaesthesia?

Answer 6

Hypotonic-benzodiazepine

Question 7

What class of drug is usually used as intra operative analgesia?

Answer 7

Opioid

Question 8

Outline the polypharmacology of anaesthesia

Answer 8

• premedication: benzodiazepine
• induction: IV or inhalational
• intraoperative analgesia: opioid
• intubation: muscle relaxant
• maintenance: IV or inhalational
• reversal of muscle paralysis + recovery: opioid/NSAIDs/paracetaoml
• provision for post op N+V: antiemetic?

Question 9

What is volatile anaesthetic potency described by?

Answer 9

Minimum alveolar concentration

Question 10

Stage 1 Guedel’s signs

Answer 10

Analgesia
Consciousness

Question 11

Stage 2 guedel signs

Answer 11

Unconscious
Breathing erratic but delirium could occur > excitement phase

Question 12

Stage 3 guedel’s signs

Answer 12

Surgical anaesthesia

Question 13

Stage 4 guedel’s signs

Answer 13

Respiratory paralysis + death

Question 14

What is the anatomical substrate for minimum alveolar concentration?

Answer 14

Spinal cord

Question 15

What factors affect induction + recovery + potency?

Answer 15

Partition coefficients (solubility)
- blood:gas partition determines induction + recovery
- oil:gas partition determines potency

Question 16

What does the blood:gas partition determine?

Answer 16

Induction + recovery

Question 17

What does the oil:gas partition determine?

Answer 17

Potency

Question 18

What increases minimum alveolar concentration?

Answer 18

• hyperthermia
• pregnancy
• alcoholism
• central stimulants

Question 19

What decreases minimum alveolar concentration?

Answer 19

• increasing age
• hypothermia
• Other anaesthetics + sedatives
• Opioids

Question 20

Why is nitrous oxide often added to other volatile agents?

Answer 20

To reduce the dosing needed + reduce side effects

Question 21

Relationship between lipid solubility + potency

Answer 21

High potency - high lipid solubility

Question 22

Relationship between potency + GABA_A interaction

Answer 22

High interaction -

Question 23

Examples of volatile anaesthetics

Answer 23

Halothane
Isoflurane
Sevoflurane
Desflurane

Question 24

Describe GABA_A

Answer 24

• ligand gated ion channel
• major inhibitory transmitter
• potentiate GABA activity
• sedation, anaesthesia + anxiolysis

Question 25

What receptors do anaesthetics work on?

Answer 25

GABA_A OR NMDA glutamate receptor

Question 26

What anaesthesia act on NMDA receptors?

Answer 26

Xenon Nitric oxide Ketamine

Question 27

What affect do general anaesthetics have on parts of the CNS

Answer 27

- reduces connectivity between reticular system - hippocampus depressed - brainstem depressed - spinal cord depress dorsal horn + motor neuronal activity

Question 28

What are the uses of IV general anaesthetics?

Answer 28

IV for induction Total IV anaesthesia alone

Question 29

What is the mechanism of action of IV anaesthetics?

Answer 29

- **propofol + barbiturates**: potentiate GABA_A - **ketamine**: inhibits NMDA receptor

Question 30

Uses of local + regional anaesthesia

Answer 30

- dentistry - obstetrics - regional surgery - post op for wound pain - chronic pain management

Question 31

Basic local anaesthetic structure

Answer 31

Aromatic ring + amine Linked by ester or amide link

Question 32

Examples of local anaesthetics

Answer 32

Lidocaine Bupivacaine Ropivacaine Procaine

Question 33

Target site for local anaesthetics

Answer 33

Voltage gated sodium channel

Question 34

What are the adverse drug reactions of general anaesthesia?

Answer 34

Post op N+V Hypotension Post operative cognitive dysfunction Chest infection

Question 35

Mechanism of action of local anaesthetics

Answer 35

Block VGNCs This prevents AP from being produced

Question 36

What are the adverse drug reactions of local anaesthetics?

Answer 36

- Depends on agent used + usually result from systemic spread - Allergic reactions + anaphylaxis - Cardiovascular toxicity due to blockage of VGNC

Question 37

What is minimum alveolar concentration?

Answer 37

The concentration at which 50% of people fail to respond to surgical stimulus

Question 38

Relationship between minimum alveolar concentration and potency

Answer 38

High MAC = lower potency