10. Local Anaesthetics Flashcards

1
Q

Local anaesthetics

A

-substances reversibly produce blockade of sensitive neurons in certain part of body
-local analgesics - blocks perception of pain in certain part of the body

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2
Q

mechanism of action of LA

A

-gradual block of Na+ voltage gated channels in neurons -> decrease or block of axonal conduction in neurons

-drug must penetrate neuron to evoke its effect

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3
Q

PK of LA

A

-absorption and distribution influence duration of effect and toxicity of LA
-absorption from administration site depends on blood perfusion

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4
Q

How are LA classified ?

A
  • Esters
    -Amides
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5
Q

PK of ester LAs

A

short bio half life
lower protein binding
metabolised by plasma esterases

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6
Q

pk of amide LAs

A

strong plasma protein binding
metabolised in the liver

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7
Q

what are the factors influencing effects of LA

A

-physical-chemical properties
-type of neuronal fibres (vegetative, sensitive (hot, cold, pain),motor fibres(

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8
Q

what are the adverse effects of LA

A

-cardiovascular toxicity
-allergy
-neurotoxicity
-methemoglobinaemia

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9
Q

cardiovascular toxicity involves

A

-bupivacaine- most cardiotoxic
-bradycardia
-vasodilation, hypotension, syncope
-cardiovascular collapse

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10
Q

what is the therapy for cv toxicity?

A

cardiopulmonary support + sympathomimmetic therapy with adrenaline and atropine, lipid emulsions

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11
Q

methemoglobinaemia

A

mostly in prilocaine -due to its metabolites
therapy: iv. methylene blue 1% +o2

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12
Q

allergy

A

mostly with ESTERS - caused by their metabolites
-exanthem, edema, asthma attack, anaphylaxis

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13
Q

what are some other adverse effects of LA

A

injury of nerve during administration
malignant hyperthermia

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14
Q

what are the vasoconstringent adverse effects

A

ischemia/necrosis
tachycardia, palpitation
increased BP
arrythmia
do not co administer with MAO inhibitors

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15
Q

what are the ester local anaesthetics ?

A

-procaine
-benzocaine
-tetracaine
-cocaine
-oxybuprocaine

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16
Q

what are the amide local anaesthetics

A

Mesocaine
articaine
mepivacaine
bupivacaine
ropivacaine
-prilocaine
cinchocaine

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17
Q

procaine

A

slow onset of action
short duration of effect
poorly absorbbed from skin and mucosa

18
Q

tetracaine

A

highly potent but with high toxicity
only used for topical anaesthesia

19
Q

benzocaine

A

only for topical anaesthesia
oral use for sore throat

20
Q

cocaine

A

first known LA
comes from the coca plant
vasoconstrictor effect , highly addictive
only for surface anaesthesia

21
Q

mesocaine

A

two drugs sold under the brand name
LIDOCAINE- fast onset and intermediate duration
TRIMECAINE-long onset , intermediate duration

22
Q

Articaine

A

fast onset long effect
used in dentistry - ADRENALINE REQUIRED

23
Q

Mepivacaine

A

vasoconstrictor- no need for adrenaline
used in dentistry

24
Q

Bupivacaine

A

CARDIOTOXIC
-local and infiltration anesthesia
-continual infusion to epidural space to treat acute pain

25
Q

Ropivacaine

A

-all types of anesthesia EXCEPT SUBARACHNOID
never into a liquor space

26
Q

Prilocaine

A

surface anaesthesia (EMLA)
spinal anaesthesia for short surgical procedures
AE : METHAEMOGLOBINEMIA

27
Q

cinchocaine

A

topical anaesthesia
HIGHLY TOXIC

28
Q

procaine

A

oldest synthetic LA
slow onset slow duration
infiltration and conduction anaesthesia

29
Q

benzocaine

A

topical anaesthesia fir ear, throat , oral cavity

30
Q

tetracaine

A

fast onset
topical anaesthesia of oral cavity and throat
HIGHLY SYSTEMIC TOXICITY

31
Q

what are the types of LA

A

-topical surface anaesthesia
-infiltration anaesthesia
-conduction anaesthesia

32
Q

Topical surface anaesthesia

A

transdermal penetration of LA in the form of solutionn, spray, gel
-used on mucosa, cornea , oesophagus , GUT catheterisation
-EMLA

33
Q

EMLA -eutectic mix of LA

A

-EMLA- lidocaine and prilocaine (euctectic mixture of LA)
-used on intact skin, in peds procedures
melts better has a better absorption compared to a single LA

34
Q

Infiltration anaesthesia

A

subcutaneous, submucosal, intramuscular, intraarticular
-blocks nerve conduction near site of admin
-used in minor procedures, dentists

35
Q

Conduction anaesthesia involves ?

A

-peripheral nerve block
-regional anaesthesia
-central conduction anaesthesia

36
Q

Peripheral nerve block- conduction anaesthesia

A

-blocks nerve trunks and individual nerves

37
Q

Regional anaesthesia -conduction anaesthesia

A

IV regional anaesthesia (Bier block)
-common- TRIMECAINE or LIDOCAINE -quick onset and quick inhibition of motor functions
-no toxic LA !! NO BUPIVACAINE
-requires exsanguination of limbs so only short procedures

38
Q

Central conduction anaesthesia

A

-epidural
-subarachnoid

39
Q

epidural ->central conduction anaesthesia

A

-perioperative and obstetric anaesthesia
-requires stopping anticoagulants and antiplatelet agents

40
Q

subarachnoid -> central conduction anaesthesia

A

-intrathecal admin of LA into interveertebral space