Perioperative anaesthesia

Question 1

What is general anaesthesia?

Answer 1

A reversible state of unconsciousness

Question 2

Name the 3 stages of general anaesthesia

Answer 2

Induction
Maintenance
Emergence

Question 3

What is local anaesthesia?

Answer 3

A nerve block causing revisable absence of pain sensation

Question 4

Name the 4 techniques used in local anaesthesia

Answer 4

Local anaesthetic field block
Peripheral nerve block
Nerve plexus block
Central neuraxial block - e.g. spinal or epidural

Question 5

State the characteristics of a subarachnoid (spinal) central neuraxial block

Answer 5

Injection through dura into CSF
Low volume (up to 3ml)
High concentration local anaesthetic - 0.5% bupivicaine
Rapid onset dense sensorimotor block
Profound vasodilation ➔ haemodynamic instability

Question 6

State the characteristics of an epidural central neuraxial block

Answer 6

Catheterisation of potential space outside dura
High volume (>10ml)
Variable concentration local anaesthetic - analgesia 0.1% bupivicaine, anaesthesia up to 2% lignocaine
Gradual titration of block density, may have motor sparing
Gradual titration ➔ less haemodynamic instability

Question 7

State one benefit of epidural central neuraxial block over subarachnoid (spinal) central neuraxial block

Answer 7

Epidural block causes less haemodynamic instability

Question 8

What is the triad of anaesthesia?

Answer 8

Hypnotic agent
Analgesic
Muscle relaxant

Question 9

Define the induction stage of general anaesthesia

Answer 9

Transition from an awake state to an anaesthetised state

Question 10

Name 3 IV induction agents used for general anaesthesia

Answer 10

Propofol (rapid)
Barbiturates (rapid)
Ketamine (slower)
Benzodiazepines
Dexmedetomidine (no risk of resp depression)

Question 11

What is the benefit of using opioids during induction of general anaesthesia?

Answer 11

Reduces the dose of induction agent needed

Smooths the induction process

Question 12

Name 3 factors cause delays in inducing anaesthesia

Answer 12

Slow arm-brain circulation time: e.g. elderly, cardiovascular disease
Patient anxiety
Recreational drug use
Extravastion (leakage of IV fluid into extravascular tissue)

Question 13

Name the 2 types of induction agents used in general anaesthesia

Answer 13

IV induction*

Inhalational induction

Question 14

Name 2 inhalation induction agents used for general anaesthesia?

Answer 14

Sevoflurane*
Desflurane
Isoflurane
Halothane
Sevoflurane
Nitrous oxide

Question 15

What are the indications for inhalational induction?

Answer 15

Paediatric practice
Cases of difficult airway
Difficult venous access
Inhaled foreign body

Question 16

What is rapid sequence induction/intubation?

Answer 16

An airway management technique that induces immediate unresponsiveness and muscle relaxation.

Fastest and most effective means of controlling the emergency airway.

Minimises the risk of regurgitation and aspiration.

Question 17

Which scenarios in particular benefit from rapid sequence induction/intubation?

Answer 17

Intact gag reflex
Unfasted stomach
Life-threatening injury or illness requiring immediate airway control

Question 18

Outline the mechanism of action of general anaesthetic agents such as Propofol

Answer 18

Majority act via GABA-A receptors -> Cl- ion movement depresses the CNS

Question 19

Outline the mechanism of action of Xe, Nitrous oxide, and Ketamine as anaesthetic agents

Answer 19

Inhibit NMDA (excitatory glutamate) receptors

Question 20

What are the effects of CNS depression?

Answer 20

Sedation and reduced anxiety
Lack of awareness and amnesia
Skeletal muscle relaxation
Suppression of undesired reflexes
Analgesia

Question 21

What is the indication for muscle relaxants whilst inducing anaesthesia?

Answer 21

Requirement for intubation

Question 22

What muscle relaxants can be used during intubation?

Answer 22

Depolarising: Suxamethonium

Non-depolarising: Atracurium

Question 23

Define the maintenance stage of general anaethesia

Answer 23

Keeping a patient unconscious

Question 24

Name the 2 types of maintenance agents used in general anaesthesia

Answer 24

Inhaled volatile agents*

Continuous IV infusion

Question 25

How is the potency of inhalation anaesthesia assessed?

Answer 25

Minimum alveolar concentration (MAC)

Question 26

Define minimum alveolar concentration (MAC)

Answer 26

Alveolar concentration of a volatile agent needed to eliminate movement in 50% of population in response to a standard incision.

Question 27

What is the benefit of Nitrous oxide when used in addition to inhaled volatile agents?

Answer 27

Reduces the required dose of other inhalations needed to achieve MAC.

Question 28

Define the recovery/emergence stage of general anaesthesia

Answer 28

Transition from an anaesthetised state to an awake state

Question 29

What determines full recovery from general anaesthesia?

Answer 29

Return of consciousness and protective reflexes

Question 30

What medication should be given prior to emergence from general anaesthesia?

Answer 30

Adequate analgesia

Anti-emesis

Question 31

Outline the important considerations of perioperative care

Answer 31

Warming - susceptible to hypothermia due to mass vasodilation
Fluid balance
Positioning - prevent nerve and pressure injuries
Patient awareness
Drug interactions
Analgesia
Safety - WHO surgical checklist

Question 32

What are the 4 stages of Guedal’s classification?

Answer 32

1: Analgesia and consciousness
2: Excitement, unconscious, breathing erratic
3: Surgical anaesthesia
4: Respiratory paralysis and death