How does the sensitivity for the blockade of local anaesthetics compare regarding:

1. Myelinated and unmyelinated fibres

• Myelinated fibres are easier blocked than unmyelinated fibres. The myelinated fibres are thus more sensitive to the LA than the unmyelinated fibres

2. Pressure/touch nerves compared to dorsal nerves that transmit pain impulses

• The dorsal nerves that transmit pain impulses are much more sensitive for the LA’s than the pressure/touch nerves in the body

What are the effects of LA’s on other tissues?

• Heart: These drugs act like class 1 anti-arrhythmic drugs
• Skeletal muscle: The drugs have weak action on the muscles

What is the basis for selecting local anaesthetics?

• It is used for smaller surgical procedures, typically spinal anaesthesia
• It is used for autonomic blockade in ischaemic states and pain
• It is also used for postoperative analgesia

Why are local anaesthetic solutions saturated with CO2?

• CO2 helps with the diffusion of the drug across the membranes and maintain the pH

Which drugs are typically used as surface anaesthetics:

• Oxybuprocaine
• Cocaine
• Benzocaine