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

1. myelinated fibres with unmyelinated fibres;

Smaller myelinated fibres are easier blocked than larger unmyelinated fibre because of the diameter of the nerve plays a very large role in the distribution of LA

While unmyelinated fibres are blocked faster than myelinated fibres (both fibres have the same diameter) because of the Myelin sheath that surrounds the fibre (lipid barrier)

2.  pressure/touch nerves with the dorsal nerves that transmit pain impulses?

(Dorsal nerve is larger the ventral motor nerve)

Because the dorsal nerve that transmits pressure and touch impulses is an active pain fibre nerve, then blockage of this nerve will be relatively fast, thus its sensitivity will be high to LA blockage.

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

Most LA has a vasodilatory effect on the circulation system.

LA has a CNS depression effect.

What is the basis for the selection of a LA?

The pH should be taken in consideration before deciding on a LA because pH interferes with ionized and unionized forms of the agents. Unionized agents crosses lipid membranes but ionized agents blocks the sodium channel more effective.

The total duration of action should be considered before selecting a LA, Esters has a shorter duration of action than Amides.

Why are LA solutions sometimes saturated with CO₂?

Some can reached with CO₂ and be exhaled in that form, and may even be re-inhaled in to the body,

Which of the LA are typically used for surface anaesthesia?

Benzocaine, cocaine and Oxybuprocaine is used as surface anaesthesia.