Local Anaesthetics
1. Regarding local anaesthetics
a. Adrenaline increases systemic absorption – decreases 30%
b. Maximal blood level is independent of site of administration - dependent
c. Blockade of Ca2+ channels augments effects – is seen in cardiac tox
d. Bupivacaine has a short duration of action - long
e. None of the above are true <=
2. Local anaesthetics:
a. May cause blockage of motor nerves before sensory nerves in large mixed nerves <=
b. Preferentially block larger fibres – small myelinated rapidly firing
c. Preferentially block unmyelinated nerves
d. Will block A-a fibres before A-d and C fibres
e. Have no cardiac effects
3. Which local anasthetic causes methaemoglobinaemia?
a. Lignocaine
b. Tetracaine
c. Bupivacaine
d. Procaine
e. Prilocaine <=
4. Which is an ester local anaesthetic?
a. Tetracaine <=
b. Lignocaine
c. Bupivacaine
d. Etidocaine
e. Prilocaine
5. The local anaesthetic agent prilocaine:
a. Is metabolized by butyrylcholinesterase
b. Has a very short duration of action
c. Has the same intermediate chain as procaine
d. Is more likely to cause toxicity in patients with liver disease <=
e. Should not be used in patients with a known hypersensitiviy to p-aminobenzoic acid – ester Las
metabolised to PABA
6. With regard to susceptibility to block by local anaesthetic agents, which is NOT true?
a. Dorsal root pain fibres are more sensitive than proprioceptive fibres
b. They preferentially block small fibres
c. Myelinated nerve fibres tend to be blocked before non-myelinated ones of the same size
d. Motor fibres may be blocked before pain fibres in the brachial plexus
e. Block starts at the distal parts supplied by the nerve and proceeds proximally <= outer fibers are
from proximal area, so block is proximal to distal
7. Lignocaine
a. Penetrates the axon in its charged form
b. Is more potent than bupivacaine
c. Has a higher affinity for activated than resting sodium channels <= higher affinity for open or
inactive c.f. resting
d. Is a weak acid
e. Blocks voltage gated sodium channels at their extracellular end
8. Concerning lignocaine toxicity:
a. Lignocaine is highly cardiotoxic compared to other local anaesthetics
b. Lignocaine exacerbates ventricular arrythmias in abobut 10% of patients <= ?
c. Neurological effects are less common
d. Hypotension is most common
e. Side effects are not dose related
9. The half life of lignocaine is
a. 1 minute
b. 5 minutes
c. 10 minutes
d. 30 minutes
e. 120 minutes <=, bupivicaine is 4-5hr
10. All of the following are amide local anaesthetics EXCEPT:
a. Lignocaine
b. Bupivacaine
c. Benzocaine <=
d. Prilocaine
e. Etidocaine
11. Local anaesthetics
a. Act on the most rapidly firing neurons <=
b. ?
c. ?
d. have an increased effect on large fiber diameter
e. ?