Week 8 - Local Anaesthetics Flashcards
How do local anaesthetics work?
- lipophilic compound enters plasma membrane
- blocks Na channels
- target nociceptors due to no myelin sheath
What some local anaesthetics uses?
- relieve itching (topically)
- Minor surgical procedures
- Epidural anaesthesia
- Intrathecal anaesthesia (spinal)
Where is the site of injection for Minor surgical procedures?
Intradermally
Subcutaneously
Where is the site of injection for Epidural anaesthesia?
epidural space (above the dura mater)
Where is the site of injection for Intrathecal anaesthesia?
subarachnoid cerebrospinal fluid
What are the pharmacokinetics of local anaesthetics?
- usually administered at site required
- absorpotion and distribution not important
- metabolised in the liver
What are the toxicity effects of local anaesthetics?
- affect other tissues
- electrical conduction system in the heart and CNS neurons
How can toxicity be avoided?
Adrenaline
Heavy emulsions
How can Adrenaline avoid toxicity?
- Injected with
- Vasoconstrict (α1 receptors)
- Prevents distribution
- decreases bleeding
How can Heavy emulsions avoid toxicity?
- Intrathecal injection solution is dense
- Prevents spread to other areas of CNS
What are some types of local anaesthetics?
- Lignocaine
- Benzocaine
- Bupivacaine
What are the characteristics of Lignocaine?
- common
- injection or cream
- used in dental surgery
What are the characteristics of Benzocaine?
used topically
used for sunborns, sore throats
What are the characteristics of Bupivacaine?
- toxic
- injected to peripheral circulation (binds to albumin)
- good long term spinal block
- Doesnt cross placenta
- slow onset of action
