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23 Cards in this Set
- Front
- Back
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What is the goal of local anasthetics?
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Block neural transmission
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What is the mechanism of L.A.?
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block sodium (Na) channels in axons by inhibiting potential propagation. Closes in initial phase and causes reversible action.
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What are effects of L.A.?
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With the alpha-1 receptor agonist, it reduces local blood flow and prevents system absorption.
It increases local concentration. |
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With alpha-1 receptor agonist, L.A. gets CNS stimulation called what?
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deinhibition
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Progression of Differential nerve block effective nerve fibers
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Small diameters are most sensitive (Type C and post-ganglionic sympathetic)
Then larger fibers affected such as Type A temperature. Finally Large Type A motor neurons affected. |
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What ways can differential nerve block be administered?
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electrical, US, infiltration, along a prospective incision line.
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Where is a peripheral nerve block done at?
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near trunk
common for dental |
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Central nerve block location
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epidural so between the bone and the dura mater.
Can lead to postural headaches. Have a risk for a hematoma if Heparin is given. |
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Spinal nerve block location
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subarachnoid space (intrathecal).
Effective but dangerous |
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Indication and location for Sympathetic block location
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complex regional pain syndrome. Done in central nerual block, but can be done surrounding nerve chain ganglia.
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Descriptions of the Lipophillic group
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All are weak bases
Often used in combo with vasoconstrictor CNS stimulation then depression Cardiac depression |
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Mechanisms of Esters: Procaine (Novocain)
Tetracaine, Cocaine |
-Rapidly metabolized by blood cholinesterase to an allergen
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Indications of Esters: Procaine (Novocain)
Tetracaine, Cocaine |
-Intermediate onset, short duration
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Advantages of Esters: Procaine (Novocain)
Tetracaine, Cocaine |
Anasetitizes the area.
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Disadvantages of Esters: Procaine (Novocain)
Tetracaine, Cocaine |
Allergic reactions occur.
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Mechanism of Amides: Bupivacaine (Marcaine)
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Metabolized by P450 enzymes in the liver.
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Indications of Amides: Bupivacaine (Marcaine)
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Slow to intermediate onset, long duration of action
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Advantages of Amides: Bupivacaine (Marcaine)
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Good alternative for patients allergic to esters
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Disadvantages of Amides: Bupivacaine (Marcaine)
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Duration prolonged if liver funciton is impaired.
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Mechanism of Lidocaine (Xylocaine)
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Lipophilic group. An amide.
Metabolized by enzyme P450. Weak base. Uncharged species corsses neuronal membrane and charged species binds to sodium channels. |
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Indications of Lidocaine (Xylocaine)
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Can be used on a transdermal patch.
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Advantages of Lidocaine (Xylocaine)
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Rapid onset
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Disadvantages of Lidocaine (Xylocaine)
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Repeated injections may reduce pH so there is decreased penetration of the drug.
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