7 - Anasthetics and stains Flashcards

1
Q

what is a topical anaesthetic

A

POM
- drugs that reversibly block transmission in sensory nerves

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2
Q

indications for use ?

A
  • contact tonometry
  • cl fitting
  • foreign body removal
  • gonioscopy
  • lacrimal procedures
  • ever for release of symotoms
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3
Q

advantages of local anaesthetics

A
  • allow certain procedures to be conducted
  • make px more comfortable
  • makes procedure easier for practitioner
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4
Q

disadvantages of local anaesthetic

A
  • sting (due to pH)
  • delay healing (reduces production of collagen)
  • eye is more susceptible to damage
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5
Q

what is the mode of action of local anaesthetics

A

memorise action potential graph + process

  • action potential passes along nerve
  • successive depolarisations and repolarisations of adjacent areas

topical anaesthetics reversibly block nerve conduction by blocking sodium channels, therefore action potential cannot be generated

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6
Q

what are local anaethetics made of

A

lipid soluble hydrophobic portion
and a readily ionised hydrophillic portion

they can swtich from charged and unchargedh

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7
Q

what does being hydrophobic and lipophillic allow them to to

A

rapidly diffuse across lipid membrane of the epithelial cells and bind to the intracellular portion of sodium channels

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8
Q

what are the different portions separated by

A
  • intermediate alkyl change

which contains either an ester or amide linkage

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9
Q

chemical structure of anesthetics
ESTER LINK

A
  • hydrolysed by cholinesterase
  • short duration
  • oxybuprocaine
  • tetracaine
  • proparacaine
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10
Q

chemical structure of local anaesthetics
AMIDE LINK

A
  • resistant to hydrolysation
  • longer duration

Lignocaine only

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11
Q

which structure are allergic reactions more common in

A

esters

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12
Q

which linkage bond is broke more easily

A

ester

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13
Q

what is the onset of all anaesthetics

A

1 min

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14
Q

15 mins duration

A
  • oxybuprocaine
  • proxymetacaine
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15
Q

20 mins duration

A

tetracaine

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16
Q

30 min duration

17
Q

which anaesthetic is most potent

A

tetracaine hydrochlride (amethocaine)

stings most

  • provides deepest anaesthesia
  • foreign body removal

sensitivity is rare but occurs after repeated doses

  • associated with punctate staining
18
Q

contraindications/caution of tetracaine hcl

A
  • prematue babies
    -known allergy
  • sulphonomides
  • prenancy/lactation
19
Q

preparations of tetracaine hcl

A

0.5% and 1% in minims

  • store below 25 and protect from light
  • hydrolysed by light
  • solutions >1% damage cornea

removal of foregin body after 1 drop

20
Q

which is most commonly used by optoms

A

oxybuprocaine hydrochloride (benoxinate)

  • less stinging and irritation than amethocaine
  • bactericidal properties (disadvantage)
21
Q

what are contraindications/cautions of oxybuprocaine

A
  • known allergy
  • premature babies
  • pregnancy/lactation
  • if px is on any other drops containing chlorohexidine acetate as a preservative are being used
22
Q

preparations of oxybuprocaine hcl

A
  • minims 0.4%
  • store below 25 protect from light

opthalmology
- 3 drops over 5 min interval allows foreign body to be removed

23
Q

which one stings least

A

Proxymetacaine HCL
- ideal for tonometry, minimal punctate corneal staining
- least antibacterial properties

24
Q

contraindications/caution of proxymetacine hcl

A
  • known allergy
  • overactive thyroid
  • heart disease
  • premature babies
  • pregnancy/lactation
25
preparations of proxymetacine hcl
minims 0.5% stored 2-8C, fridge can be used in cataract extraction as vert potent
26
Lidocaine HCL (lignocaine
- stings less than amethocaine -amide link - used if px sensitive to ester link - longer duration contraindications/caution - pregnancy/ lactation - premature babies
27
lidocaine hcl preparations
- minims 4% combined with 0.25% fluoroscien
28
side effects of lidocaine
- transient stinging/bluring - conjunctical hyperaemia - mild superficial epithelial damage - punctate keratitis - repeated use ~ epithelial toxicity ~ serios keratopathy
29
uses + disadvantages of Fluoeoscien
- tonometry - corneal abrasions - CL fitting - TBUT - lacrimal drainage psuedomonas aeruginosa
30
rose bengal uses + disadvantages
- staining od fead and devitalised cells -aids dry eye diagnosis irritates try eyes on instilation stings can stain healthy cells
31
uses and disadv of lissamne green
- stains lipid like structures no disadvantages
32
why is fluoro not a true stain
just colours tear film. epithelial damage means fluoro can gain access to deeper layers
33
contrainidications of fluoro
- known sensitivity - soft CL lenses
34
cautions of fluoro in a multi dose bottle
-contamination problems in hospitals in 1950s - fl used on damaged corneas - psuedomonas has affinity for it progesses rapidly corneal perforation 48h
35
fluoro minims
1 and 2% contains buffer to stabilise solution slighty alkaline