Term
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Definition
Block nerve conduction when applied at appropriate concentrations.
Block voltage dependent Na channel and therefore inward Na flow in order to block action potential. |
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Term
Local anesthetic mechanism of action
****he wants us to know this**** |
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Definition
| Cationic form interacts with open Na channels on the inner surface of the axonal membrane (must cross axonal membrane in order to be effective). This causes a dose dependent decrease in impulse conduction. |
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Term
| In general smaller nerve fibers are ____ susceptible than larger, heavily myelinated fibers |
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Definition
More
Type B and C fibers: * Postganglionic sympathetic, dorsal root pain fibers and preganglionic autonomic are much more effected than
Type A: delta (pain/temp), gamma (mm spindles), beta (touch and pressure), alpha (proprioception, motor).
With alpha being the least affected |
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Term
| Which form of local anesthetics can cross axonal membrane |
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Definition
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Term
| Mode of transport of local anesthetics |
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Definition
| Local anesthetics are weak bases, the are injected as ionized drug, they become a free base prior to crossing the membrane. Once in the membrane they convert to the ionized form which binds to the sodium channel. |
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Term
| Types of local anesthetics |
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Definition
Esters (procaine)
Amides (lidocaine) |
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Term
| Common structure of all local anesthetics |
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Definition
Aromatic ring
Teritary amine
Alkyl chain |
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Term
| Determinants of Blockade of local anesthetics |
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Definition
Potency (dependent on lipid solubility, the more lipid soluble the better effect)
Duration (protein binding capacity)
Onset
Effect on blood vessels |
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Term
| Potency of bupivacaine and etidocaine compared to procaine |
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Definition
B: 10* more potent
E: 40* more potent |
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Term
| Bupivacaine has a _____ degree of protein binding than procaine and thus a _____ duration of block |
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Definition
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Term
| Factors that increase local anesthetic binding protein |
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Definition
| Trauma, surgery, tobacco smoking, chronic inflammation, chronic pain, uremia, CANCER |
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Term
| Factors that decrease local anesthetic protein binding |
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Definition
| Pregnancy, OCP, newborn status |
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Term
| The _____ the pKa (the pH at which 50% of the agent exists in the ionic and 50% in the non-ionic form) the _____ basic the local anesthetic and the _____ it will be to get into membrane--> _______ onset |
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Definition
Higher
More
Harder
Longer
pka is generally between 7.7-9 (which is higher than the body) |
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Term
| Vasodilation _____ the duration of action of local anesthetic and ______ the onset time. Which local anesthetic is not a vasodilator? |
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Definition
Decreases
Prolongs
Cocaine |
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Term
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Definition
| Plasma and blood concentrations, total concentration, free concentration (determined by protein binding and ionization, the ionized form is toxic to CNS), lipid solubility, site of injection |
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Term
Most common vasoconstrictors added to local anesthetics
Adverse effects of adding these |
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Definition
Epinephrine, ephedrine, phenylephrine
HTN, tachycardia, cardiac arrhythmia, ischemia
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Term
| Anesthetic cardiac toxicity |
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Definition
| Decreased HR--> decreased CO--> ectopic foci--> MI or possibly fatal arrhythmia |
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Term
| Why are bupivacaine and etidocaine so toxic to the heart? |
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Definition
| Specific binding to cardiac conduction system |
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Term
| Side effect of Prilocaine |
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Definition
Methemoglobinemia
Prilocaine oxidizes ferrous Hgb--> Ferric making it harder to transport Oxygen
Lead to a cyanotic color that in most cases is benign.
DO NOT GIVE PRILOCAINE TO NEWBORNS |
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Term
| All local anesthetic have a _____ therapeutic index |
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Definition
Narrow
At high concentration they are toxic to nerve cells and to tissue |
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Term
| The majority of allergies to anesthetics are _____ agents |
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Definition
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Term
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Definition
| Rare, related to methylparaben (added as preservative) |
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Term
| Metabolism of ester anesthetics |
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Definition
| Hydrolyzed by cholinesterases in plasma--> short half life. |
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Term
| Metabolism of amide anesthetics |
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Definition
Liver: N-dealkylation and hydrolysis
Decreased in patients with liver disease or decreased hepatic flow |
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Term
| Resting nerves are ______ sensitive to local anesthetics |
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Definition
| Less. They have closed Na channels. The nerve must open the channel for local anesthetic to work |
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Term
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Definition
Surface anesthesia
Infiltration
Field Block
Nerve Block
IV regional
Spinal
Epidural: Bupivacaine, Mepivacaine |
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Term
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Definition
| Procaine, Cocaine, Tetracaine, chloroprocaine, benzocaine |
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Term
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Definition
| Lidocaine, mepivacaine, bupivaciane, prilocaine, etidocaine, dubicaine, ropivacaine |
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