Local Anaesthesia Flashcards
What is Local Anaesthesia?
Anaesthesia applied to a specific region of the body without inducing total hypnosis and loss of arousal but induces analgesia
Local anaesthesia targets specific areas to alleviate pain while allowing the patient to remain conscious.
Name three options for Local Anaesthesia.
- Lignocaine
- Bupivacaine
- Ropivacaine
These agents are commonly used for local anaesthetic procedures.
What is the mechanism of action of Local Anaesthesia?
Blockage of Na+ channels to prevent axonal action potential from propagating further down the neurons
This action leads to a lack of nerve signal transmission in the targeted area.
What physiological effects does Local Anaesthesia have?
- Sympathectomy
- Local venodilation
- Local vasodilation
These effects can lead to reduced venous return and cardiac output.
How does Local Anaesthesia affect the respiratory system?
Local Anaesthesia has no effect on the respiratory system unless injected directly into a vein instead of a tissue
This is a key distinction between local and general anaesthesia.
What is a recent advancement in the practice of Local Anaesthesia?
Ultrasound is used for US-Guided Regional Anaesthesia
This technique reduces the likelihood of IV injection and nerve or vascular injury.
Define Local Anaesthetic Toxicity.
Toxicity associated with the rate by which the LA agent is absorbed from the tissues into the plasma, in addition to the rates of removal (clearance & metabolism) of the agent
Different areas of the body absorb local anaesthetics at varying rates.
Which local anaesthetic agent is the most toxic?
Bupivacaine
The toxicity ranking is: Bupivacaine > Lignocaine > Prilocaine.
List some symptoms of Local Anaesthetic Toxicity.
- Circumoral and lingual numbness
- Light headedness
- Tinnitus
- Visual disturbances
- Muscular twitching
- Drowsiness
- Cardiovascular depression
- Convulsions
- Coma
- Cardiovascular arrest
These symptoms can vary in severity and are critical to monitor.
How do nerve fibre types affect Local Anaesthesia?
Larger nerves are more difficult and take longer to get affected by local anaesthesia
The diameter and myelination of a fibre influence its susceptibility to local anaesthetics.
What is Spinal Anaesthesia?
Injection of a local anaesthetic agent into the CSF surrounding the cord and/or nerve roots in the subarachnoid space
This method requires lower doses compared to epidural anaesthesia.
What is Epidural Anaesthesia?
Injection of a local anaesthetic agent into the epidural space surrounded by a thick fibrous investment
This method requires higher doses than spinal anaesthesia.
Which nerve roots serve inspiration and expiration?
Inspiration is served by higher nerve roots, while expiration is served by lower nerve roots
This anatomical distinction is important for understanding the effects of spinal and epidural blocks.
True or False: Local Anaesthesia affects the entire body.
False
Local Anaesthesia effects are limited to the area covered by the block.
Why do anaesthetists have more control over general anaesthesia than local anaesthesia?
GA affects the whole body, while LA effects are limited and cannot be adjusted once the injection is made
This limits the anaesthetist’s ability to manage potential side effects during a local block.
What caution should be taken when performing epidural anaesthesia?
The dose of the LA agent for the epidural is much higher than for spinal anaesthesia
Care must be taken to avoid injecting the epidural dose into the subarachnoid space to prevent overdose.
