How does the sensitivity for blockade by a LA compare regarding the following types of fibres:

(a) myelinated fibres with unmyelinated fibres; and

(b) pressure/touch nerves with the dorsal nerves that transmit pain impulses?

1. Unmyelinated fibres and smaller myelinated fibres are easier to block than larger myelinated fibres, thus they are more sensitive to the effects of local anaesthetics.
2. When type A fibres are blocked it influences the proprioception, touch, pressure, muscles, pain, and temperature functions. This fibre has high frequency pain transmission; thus blockade will be done with lower concentration of local anaesthetic. And does not appear to have high sensitivity for local anaesthetics.

Make a list of the effects of LA on other tissues.

CVS: cardiac depression

CNS: sedation, light-headedness, visual and auditory disturbances, restlessness, and CNS depression.

Skeletal muscle: it has a weak blocking action thus no clinical applications.

What is the basis for the selection of a LA?

• It depends on how long the LA will be used.

• What the LA will be used for, its clinical use.

• How long the LA lasts.

Why are LA solutions sometimes saturated with CO2?

It potentiates the LA, which therefore means the LA are accelerated.

Which of the LA are typically used for surface anaesthesia?

• Cocaine

• Benzocaine

• Oxybuprocaine