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37 Cards in this Set
- Front
- Back
Channels in _____ (negative potentials) have _____ for L.A. than channels in open (positive potential) or _____.
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resting state
lower affinity inactivated states |
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In _____, more channels are open or inactivated at any given time, therefore, the effect of L.A. is more pronounced
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rapidly firing axons
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What are the effects of time dependence with regards to local anesthetics?
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Sodium channels recover 100x slower than normal
Refractory period is increased Nerves conduct fewer impulses |
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With the application of increased local anesthetic what are the effects?
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1. Threshold increases
2. Impulse conduction slows 3. Rate of rise of AP declines 4. AP amplitude decreases 5. Ability to generate AP is gone |
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What other factors can increase or decrease susceptibility to nerve blockade?
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1. Myelination (more sensitive)
2. Nerve fiber diameter 3. Firing Frequency 4. pH |
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How many nodes must be exposed before conduction halts?
_____ fibers have shorter critical length (fail to conduct) than _____ diameter axons |
3
Small, large |
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What are the sequential loss of sensations from LA?
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Pain > cold > warmth > touch > deep pressure > motor
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What form crosses the neuronal membrane?
What form blocks the sodium channels? So what is going to increase blockage? |
Non-protonated form
Cationic form (BH+) Solutions saturated with CO2 (Intracellular Acidosis) |
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What does inflammation do to LA Onset?
So what's the solution? |
Inflammation lowers pH making Cationic form more abundant and can't cross neuronal membrane.
Add Bicarbonate and this raises pH and non-protonated form |
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Proximity of site of injection to nervous tissues can influence _____, _____, _____ serum levels.
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onset, duration and peak
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_____ binding correlates with affinity of the L.A. for the receptor site in the sodium channel
What does this do to the duration of effect? |
Plasma protein
Increases |
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Potential for _____ increase w/ increase plasma
Why? |
toxicity
because drug is not metabolized and sticks around longer |
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_____ decrease as the pH decrease
What is this called? _____ chance for toxicity by _____ free [active drug] |
% Bound drug
Acidotic state Increase, increase |
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What helps improve diffusion through the neuronal membrane?
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Lipids
(Less dosage required) |
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Vasoconstrictors...
_____ duration of action (and local effect) by retarding removal from site of injection _____ Rate of absorption into bloodstream _____ chance of systemic toxicity by _____ levels in blood |
Increase
Decrease Decrease, decrease |
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What are the three common vasoconstrictors?
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Epi, levonordephrine, phenylephrine
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What vasoconstrictor decreases peripheral resistance, increases heart rate and stroke volume?
What kinds of complications can arise from this? |
Epi
Higher dose - increase BP, heart palpitations, chest pain |
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What vasoconstrictor is a pure α-agonist?
What are its side effects? |
Phenylephrine
No increased HR, but may increase BP and decrease HR |
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What vasoconstrictor has no β2 actions?
What are its side effects? |
Nordefrin and NE
Can increase BP and decrease HR |
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What are the two classes of LA's?
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Esters and Amides
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How are esters inactivated?
How is it used? |
Hydrolysis by plasma esterases
Benzocaine - mainly topical, no longer packaged in carps |
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How are amides metabolized?
Regular dosing may produce adverse reactions in patients with _____, as drug half-life is _____. |
Liver - some metabolites are active (Lido)
liver disease, increased |
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What are adverse effects that are seen with low dosages of LA's?
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Sleepiness
Light-headedness Visual & auditory disturbances Restlessness Tongue numbness Metallic taste |
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What are the adverse effects that are seen with Medium dosages of LA's?
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Nystagmus
Muscle Twitching |
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What are the adverse effects that are seen with the High dosages of LA's?
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Siezures and then CV collapse due to tonic-clonic convulsions
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How do you help prevent adverse effects from high dosage of used LA's?
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Pre-medicating with i.v. Diazepam
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Cardiovascular effects of LA's ...
Direct actions on _____ Indirect actions on _____ L.A. directly _____ pacemaker activity, excitability, conduction and strength of contraction Cause arteriolar dilation which leads to ... _____ |
Cardiac and smooth muscle
autonomic nerves decrease hypotension |
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What is the most cardiotoxic LA?
What is the rarest form of toxicity? |
Bupivacaine
Local tissue toxicity |
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Accumulation of metabolite of _____ from regional administration can cause methemoglobinemia; pt appears ...
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Prilocaine
cyanotic and blood appears brown (dose>400 mg) |
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What LA's have hypersensitivity issues?
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Methylparaben
Metabisulfites |
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What is the most commonly used LA?
What is it's duration of action? |
Lidocaine
1-3 Hrs. (increased with vasoconstrictor) |
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What are the adverse side effects of Lidocaine?
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drowsiness
dizziness heart block arrhythmias hypotension |
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Topical anesthetics have a greater chance for toxicity when...
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The skin is abraided
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What are the most commonly used topical anesthetics in dentistry?
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Lidocaine
Prilocaine Benzocaine |
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What topical uses Lidocaine (2.5%) + prilocaine (2.5%)
Apply 5 min before procedures such as palatal injection and gingival sulcus probing |
EMLA Topical anesthetic cream
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What local anesthetic is applied to gingival sulcus for anesthesia for periodontal scaling and root planing?
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Oraqix
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What are the different types of Blocks?
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Infiltration Block
Field Block Nerve Block |