The Actions and Uses of Local Anaesthetics Flashcards
What is nocioception?
Ability to detect harmful things happening to the body
How do local anaesthetics prevent nocioception?
Block voltage-gated Na+ channels
3 components of the common structure of a local anaesthetic
Aromatic ring - linkage - basic amine group
What property does the aromatic ring provide?
Lipid solubility/water insolubility
What property does the basic amine group provide?
Can be ionised to a cation
What 2 groups can the linkage be?
- Amide
- Ester
Mechanism of action of a local anaesthetic
- Unionised molecules formed by continuous ionisation and deionisation in equilibrium
- Unionised can cross membrane
- Equilibrium established again and ionised molecules formed
- Ionised block Na+ channels - no AP
How inflammation or infection affects local anaesthetic effectiveness
- Makes conditions acidic
- More ionised molecules
- Less molecules cross membrane and block channels
What administration does topical anaesthesia have?
Put it on surface (diffusion)
What administration does infiltration anaesthesia have?
Multiple injections into tissue
What administration does nerve block anaesthesia have?
Injection into whole nerve
What administration does epidural anaesthesia have?
Small plastic tube inserted via needle supplies area near spinal cord
What administration does spinal anaesthesia have?
Injection into spinal cord (intrathecal/subarachnoid space)
What can cause side effects when using local anaesthetics?
- Hypersensitivity reaction
- High dose
- Injected into wrong vessel
CNS side effects of local anaesthetics
- Tremor
- Convulsions
- Respiratory failure
