1. How does the sensitivity to blockade by an LA of the following types of fibers compare with each other?

• Myelinated fibres with unmyelinated fibres.
• Push / bag nerves with the dorsal nerves that conduct pain impulses.

Nerves:

• • Smaller and myelinated fibers more easily blocked than larger and unmyelinated fibers.
  • Activated pain fibers fire faster, pain sensation selectively blocked by local anesthetics.
  • Fibers in the middle of thick nerve bundle block more slowly than those on the outside of the bundle.

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

• Heart:

Class 1 antiarrhythmic drugs (Lidocaine is class 1 drug that blocks Sodium channels in the heart with the aim of shortening the Action Potential and prolonging the refractory period).

• Skeletal muscle:

Weak blocking effect, no clinical application.

• Cocaine:

Increases mood, affects central catecholamine-mediated neurotransmission (inhibits NA reuptake).

3. What is the choice of an LA based on?

The choice of local anesthetics is based on the following factors:

• The type of procedure or operation performed.
• The type of tissue to which the local anesthetic should act.
• The duration of time that these drugs should have a sedative or narcotic effect.

4. Why are LA solutions sometimes saturated with CO2?

Carbon dioxide acts as a buffer for the local anesthetics and therefore it will potentiate the effects of the local anesthetics.

5. Which of the LAs is typically used for surface anesthesia?

• Benzocaine
• Cocaine
• Oxybuprocaine