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

(a)   myelinated fibres with unmyelinated fibres; and 

Myelinated fibres are small and easily blocked where as unmyelinated are large. 

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

The dorsal nerves are more sensitive to blockade compared to the pressure nerves. 

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

Heart: class 1 anti-arrhythmic drugs. Shortens the action potential. 

Skeletal muscle: weak Blocking effect takes place, Thus there is no clinical application.

Cocaine: it increases mood, affects the central Catecholamines mediated neurotransmission and therefore block the re-uptake of NA. 

• What is the basis for the selection of a LA? 
    Duration of the effect.
    The process followed.  
   The local anaesthetic that is being used. 
• Why are LA solutions sometimes saturated with CO₂?

It is because the CO2 plays as a buffer and thus potentiates and speeds the LA. 

• Which of the LA are typically used for surface anaesthesia?

• Cocaine 
• Benzocaine 
• Oxybuprocaine 

Brand, L. 2021. Local Anesthetics. Study unit 6  [PowerPoint Presentation]. Unpublished lecture notes on eFundi, FKLG312. Potchefstroom: NWU