12.1 anaesthetics

Question 1

what are the classes of anaesthetics?

Answer 1

anaesthetics can be

• general
• local

if they’re local they can be
- regional

if they’re general they can be

• inhaled
• IV

Question 2

what are the main components of anaesthesia?

Answer 2

• analgesia
• hypnosis
• depression of spinal reflexes
• muscle relaxation

Question 3

what is minimum alveolar concentration?

Answer 3

the concentration of a vapour in the alveoli of the lungs that is needed to prevent a motor response in 50% of subjects following a surgical stimulus

Question 4

what factors affect induction and recovery from anaesthetics?

Answer 4

• solubility in blood (low in fast induction and recovery) as well as in fats and oils

Question 5

what affects minimum alveolar concentration?

Answer 5

• age (high in infants low in elderly)
• hyperthermia (increases)
• pregnancy (increases)
• alcoholism (increased)
• central stimulants (increased)
• other anaesthetics and sedatives (decreased)
• opioids (decrease)

Question 6

what is the significance of GABA receptors in anaesthetics?

Answer 6

they’re a critical target of anaesthetics

GABA is a major inhibitory neurotransmitter

anaesthetics potentiate GABA by inhibiting Cl conductance (Cl- goes into the cell to make the inside more negative = creates a membrane potential for activity)

as a result get

• anxiolytics
• sedation
• anaesthesia

and a depression in CNS activity

(with the exception of ketamine (NMDA) they all potentiate GABBA)

Question 7

how do anaesthetics affect the reticular formation?

Answer 7

they depress the reticular formation

Question 8

name some local anaesthetics

Answer 8

lidocaine
bupivacaine
ropivacaine
procaine

Question 9

what are the characteristics of local anaesthetics such as lidocaine?

Answer 9

• highly lipid soluble
• dissociation constant
• protein binding

Question 10

what is the relationship between Pka and time of onset?

Answer 10

Lower Pka = faster onset

Question 11

what is the difference between efficacy and potency ?

Answer 11

potency is a measure of drug required to produce an effect of given intensity.

efficacy is the ability of a drug to achieve its a desired outcome. a gold standard.

Question 12

what can be used to aid regional anaesthetics?

Answer 12

vasoconstrictors to localise a drug to a specific area