Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
13 Cards in this Set
- Front
- Back
Commonly used LAs
|
Oxybuprocaine hydrochloride 0.4%
Proxymetacaine hydrochloride 0.5% Amethocaine 0.5/1% Lignocaine (4%) + fluorescein (0.25%) |
|
LA mechanism of action
|
Prevent nerve impulse conduction/generation
Affect pain nerves first - smallest nerves Act @ cell membrane to prevent action potentials Reversible |
|
LA types
|
Synthetic - cocaine
Esters - all others; plasma metabolism Amides - lignocaine; liver metabolism |
|
LA chemistry
|
Contact w/ more alkaline solution --> non-ionised/lipid soluble form released
|
|
Max effective conc.
|
Conc beyond which no further activity increase occurs
|
|
Proxymetacaine
|
Most comfortable - toxic effects very rare
Less intrinsic antibacterial action --> scraping use |
|
Oxybuprocaine
|
Most intrinsic antibacterial action --> no scraping use
Very safe - toxic effects very rare |
|
Amethocaine
|
Least comfortable/significant irritation
Affected by light |
|
Lignocaine
|
Contact tonometry use w/ fluorescein
Amide - alternative in ester allergy |
|
LA desquamation
|
Epithelial cell loss/sloughing
Greater in older Px/dry eyes Measured via cell irrigation |
|
LA hypersensitivity reactions
|
Local reaction - conjunctival hyperaemia/chemosis, lid oedema, lacrimation
5 - 10 mins post instillation Tx - anti-histamine, cold packs + topical decongestant Delayed reaction possible - 6 to 12 hrs later |
|
LA toxic overuse
|
Epithelium loss + inhibited epithelial defect healing
Tear film instability + decreased blink rate w/ hypoaesthesia Chronic non-healing epithelial defect --> corneal scarring Tx - LA cessation, atropine, pressure patching + antibiotics |
|
LA precautions
|
Poor epithelial integrity
CL wear - wait 30 mins before wearing High doses w/ pupil dilation/cycloplegia Pregnancy + lactation - safe to use |