LOCAL ANAESTHETICS

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What is local anaesthesia
Agent that interrupts pain impulses in a specific region of the body without a loss of patient consciousness.
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is it reversible?
yes completely, agent does not produce any residual effect on the nerve fiber
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what do local aesthetics block?
nerve conduction
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how do local anaesthetics block nerve conduction?
by blocking Na channels
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as well as plugging in, how else can it work
lipophillic so it can diffuse and plug in
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why does it take a while to kick in
after absorption, drug is more frequent than ion channels
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what's the drug target of local aesthetics
voltage-dependent sodium channels
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what sodium channel does it block
open and inactive sodium channels
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what does it do to influx of sodium ions into nerve cytoplasm
reduces
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it prevents what of the nerve?
depolarisation
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what does it do to rate of depolarisation
slows down
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what does it do to height of AP
reduce
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what does it do to rate of rise in AP
reduce
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what does it do to axonal conduction
slow
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what does it do to propagation of action potential
prevent
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how does it alter resting membrane potential
it does not
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why does local aesthetic need to be lipophilic?
bc its acting on fatty things e.g myelin sheath
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why is pH a factor affecting local anes
charged (cationic) form binds to receptor site. Uncharged form penetrates membrane ,efficacy of drug can be changed by altering extracellular or intracellular pH
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Effect of protein binding ?
increased binding means increased duration of action
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Effect of diffusibility
increased diffusibility = decreased time of onset
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Effect of vasodilator activity
greater vasodilator activity = decreased potency and decreased duration of action
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which nerve fibres are more susceptible to be blocked by local aesthetics
small nerve fibres
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factors affecting susceptibility of blocking by local anesth (3)
degree of myelination, fibre length, speed of fibre fired
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order of sensory function block (recovery in reverse order)
pain, cold, warmth, touch, deep pressure, motor
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name the subcutaneous local anaesthesia. nerve endings and subcutaneous tissues are blocked by direct contact to local anesth. e.g suturing a cut
local infiltration
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name 3 drugs for local infiltration
lidocaine, benzocaine, tetracaine
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name the anaesthesia applied to skin or mucous membranes to relieve itching, burning, and surface pain (for example, as seen in minor sunburns).
surface anaesthesia
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drugs used for surface anaesthesia
lidocaine, benzocaine, tetracaine
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Anaesthetic agent applied directly to mucous membrane surface (cornea; respiratory tract; oral mucosa) surfaces of organs
topical block
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name drugs used in topical block e.g Used during examination procedures (often in spray form)
lidocaine, tetracaine, benzocaine
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name the longer lasting local anes injected around nerve leading to operative ice usually used in dentistry
nerve block
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name 2 drugs used for nerve block
lidocaine and bupivacaine
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where is epidural anaesthesia administered
above the dura mater in epidural space
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drugs used in epidural anes
lidocaine and bupivacaine
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where is spinal anes administered
subarachnoid space of the spinal cord to act on spinal roots and spinal nerves
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drug used in spinal anaesthesia
lidocaine
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why are vasoconstrictors sometimes combined w LA
due to decreasing blood flow from constriction, diffusion takes longer which means you can operate for a longer period
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what appears to be the best vasoconstrictor
epinephrine
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hypersensitivity caution of LA?
allergic reaction to either amide type or ester type
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Central Nervous System Toxicities to LA?
excessive amounts absorbed can cause CNS excitement and in even higher amounts CNS depression
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CNS excitement symptoms
Tremors, shivering, and convulsions
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CNS depression symptoms
respiratory arrest
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Cardiovascular Toxicities of LA
depression, arteriolar dilation (except cocaine which vasoconstriction), hypotension and abnormal heartbeat, cardiac and respiratory arrest
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Other cards in this set

Card 2

Front

is it reversible?

Back

yes completely, agent does not produce any residual effect on the nerve fiber

Card 3

Front

what do local aesthetics block?

Back

Preview of the front of card 3

Card 4

Front

how do local anaesthetics block nerve conduction?

Back

Preview of the front of card 4

Card 5

Front

as well as plugging in, how else can it work

Back

Preview of the front of card 5
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