• How does the sensitivity for blockade by a LA compare regarding the following types of fibres:
  1. myelinated fibres with unmyelinated fibres; and

- myelinated or smaller fibres are easier blocked and unmyelinated or larger fibres are blocked less easier. Fibres in the middle of a thick nerve bundle is blocked slower than those on the outside of the nerve bundle.

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

- When blocking A-type fibres, this influences the proprioception, touch and pressure fibres. These fibres are often the last type to be blocked by local anesthetics and there is thus a decrease in the sensitivity for local anesthetics.

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

• In the heart, LA are a class one anti-arrhythmic drug
• In the skeletal muscle, LA have weak blocking action and there is no clinical application.
• What is the basis for the selection of a LA?
• Local anesthetics are normally used for smaller surgical procedures or as a spinal anesthetic. It can also be used as autonomic blockade of ischemic states or post-operative analgesia. When used in low concentrations it can also be used as a slow epidural infusion. Thus they are chosen on the type of procedure that needs to be done.
• They are also chosen on the type of tissue that the local anesthetic must work on and the time that the anesthtic effect needs to be used for.
• Why are LA solutions sometimes saturated with CO₂?
• When it is saturated with CO2, CO2 acts as a buffer which can reduces the pain that the injection can cause, it also helps that there is a faster onset of action for the drug
• Which of the LA are typically used for surface anaesthesia?
• Cocaine
• Benzocaine
• Oxybuprocaine