1. Myelinated and unmyelinated fibres:
   1. Unmyelinated fibres and smaller myelinated fibres are blocked more efficiently by local anaesthetics than larger myelinated fibres. Thus, unmyelinated fibres are more sensitive to the effects of local anaesthetics.
   2. when a-type fibres are blocked, proprioception, touch, pressure, and motor fibres are influenced. These are the final type of fibres to be blocked by local anaesthetics, these fibres are therefore not that sensitive to local anaesthetics.
2. Local anaesthetics affect the cardiovascular tissue by causing cardiac depression. It also affects the central nervous system by producing light-headedness, visual and auditory disturbances.
3. A local anaesthetic is chosen for the type of procedure that is being done, the type of tissue that the local anaesthetic must be used on and the duration of the numbing effect that is needed.
4. Carbon dioxide acts as a buffer to the local anaesthetic. This reduces the pain of the injection and gives a faster onset of action. It also raises the effective concentration of the nonionized form of the local anaesthetic, this is beneficial as only the nonionized form can cross the plasma membrane to have an effect. Thus, the onset time of the regional block will be shortened.

Local anaesthetics used for surface anaesthesia include: oxybuprocaine, benzocaine and cocaine