Anaesthetics

Question 1

Types of local anaesthetics

Answer 1

Amide; lidocaine
Ester; cocaine
Lipid soluble; benzocaine

Question 2

Methods of administration of local anaesthetics

Answer 2

• Surface
• infiltration
• IV
• nerve block
• spinal (intrathecal)
• epidural

Question 3

Adrenaline is often co injected with local anaesthetics when injected into tissues?

Answer 3

Affects sensory nerve terminals

Vasoconstriction limits systemic toxicity by confine the LA to the site

Question 4

Why do we not inject adrenaline with LAs In the extremities

Answer 4

Could cause ischaemic damage

Question 5

How is IV local anaesthetic given

Answer 5

IV distal to pressure cuff
Often in limb surgery

Note there can be systemic toxicity if the pressure cuff is released

Question 6

What is nerve block anaesthesia

Answer 6

LA given close to nerve trunks eg dental nerves

Low doses, slow onset

Question 7

Why is glucose added to spinal anaesthetics

Answer 7

To increase specific gravity so patient can be tilted to move LA to specific area of spinal cord

Question 8

What is spinal anaesthesia for?

Answer 8

Abdominal
Pelvic
Lower limb surgery

Question 9

Side effects of spinal anaesthesia

Answer 9

Low normal dose (CSF)causes:

• headaches
• decreased BP as sympathetic neurones also blocked

Question 10

What is bupivacaine

Answer 10

6hr duration of action epidural anaesthetic

Question 11

Side effects of Lidocaine

Answer 11

CNS (Paradoxical inhibition of GABA?):

• Stimulation
• restlessness
• tremor

CVS (Na+ channel blockade):

• myocardial depression
• lower BP
• vasodilation

Question 12

Side effects of cocaine

Answer 12

CNS (monoamine reuptake block):
- euphoria
- excitation 
CVS (sympathomimetic): 
- increased cardiac output 
- vasoconstriction 
- increased BP

Question 13

Types of general anaesthetic

Answer 13

• gaseous/ inhalational

- IV

Question 14

Types of IV GA

Answer 14

propofol

Etomidate

Question 15

Types of inhalational general Anaesthetic

Answer 15

• diethyl ether
• nitrous oxide
• halothane
• enflurane

Question 16

Broad mechanisms of action of general anaesthetic

Answer 16

• reduced neuronal excitability

- altered synaptic function

Question 17

Molecular targets for IV GAs like propofol and etomidate

Answer 17

• increased GABA activity
• beta 3 subunit action causes suppression of reflexes
• alpha 5 subunit action causes amnesia

Question 18

How do halogenated inhalational agents cause altered synaptic function?

Answer 18

• GABAaR or
• glycineR (mostly found in spinal cord and brainstem for suppression of reflexes via alpha 1 subunit)
• inhibit CNS nAchRs (analgesic effect)

Question 19

How does nitrous oxide cause altered synaptic function?

Answer 19

• Blocks NMDA glutamate receptors

- inhibits muscular nAchRs hence muscle relaxation

Question 20

How do halogenated inhalational agents reduce neuronal excitability

Answer 20

Increases TREK potassium channel leakage hence increases the duration of hyperpolarisation

This regulates CONSCIOUSNESS

Question 21

Advantages of inhalational anaesthetics

Answer 21

• rapidly eliminated

- rapid control of depth of anaesthesia

Question 22

Advantages of IV GAs

Answer 22

• rapid induction of anaesthesia
• less coughing/excitatory phenomena
• metabolised and cleared by liver hence little control

Question 23

What would you endure and maintain anaesthesia with?

Answer 23

Induce with propfol

Maintain and control depth with enflurane