16. Local anesthetics Flashcards
Action of local anaesthetics
Blocking conduction in nerves without LOC / depressed CNS activity
Effect of local anaesthetics
Produce loss of sensation & muscle paralysis
- Depends on the type of fibre involved and the route of application
How do local anaesthetics work physiologically?
Block action potential generation by blocking Na+ channels
Local anaesthetics act in what form?
In their cationic form (have to be weak bases)
Give the order of neuron function loss
- Pain
- Warmth
- Touch
- Deep pressure
- Motor function
Give the two chemical types of local anaesthetic
- Esters
- Amides
Esters
Procaine, Benzocaine, Tetracaine
Primarily hydrolysed by plasma esterase & degraded by hepatic metabolism
Amides
Lidocaine, Prilocaine
- Largely degraded by hepatic inactivation
- Metabolites are excreted by the kidney
Local anaesthetic side effects
Relatively free from side effects
- Allergy
- Asthmatic seizure
- Local tissue irritation
Topical anaesthesia
On cornea, mucous membranes, skin
- Cause loss of sensation by paralysing sensory nerve endings
- Ophthalmology, examinations, burns, inflammation of ear
Local infiltration
Numerous SC injections
- Minor surgery
- Dentistry
- Castration
Perineural injection
- Peripheral nerve block
- Minor surgery
- Dentistry
Intraarticular anaesthetic
For diagnosis of lameness
Indication: Operation of affected joint
Intravenous regional anaesthesia (IVRA)
Local anaesthetic injected IV distally (prilocaine)
- Frequently used in operations of digits in cattle
Epidural & spinal block
Injection into the epidural space
- Surgery of perineal region
- Anal/perianal region
- Obstetric operations
- Urology
- Dog: Lumbosacral space
Lidocaine, xylazine, ketamine, opioids
