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28 Cards in this Set
- Front
- Back
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LA mechanism of action |
interact w/nerve membranes, inhibit crossing of sodium ions- nerves cant depolarize, conduction of impulses blocked Sodium influx necessary for depolarization, propagation of nerve impulse Action (blockade) is reversible- LA carried away by circulation and metabolized |
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1st fibers to be blocked by LA |
sensory and autonomic nerves (C fibers) pain fibers can be blocked w/o altering skeletal muscle function (diaphragm) |
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Last nerves to be blocked |
motor nerves that supply skeletal muscle (A fibers) large fibers w/thick myelin coverings |
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LA |
Weak bases, travel in body as either uncharged, positively charged molecules Uncharged more lipid soluble- can cross into neuronal membrane (lipid matrix), gain access to sodium ion channel receptor. Sodium ion channel is more water soluble. LA returns to charged (+) form, binds w/receptor
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What influences duration of LA nerve block? |
intensity of receptor binding |
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Examples of ester LA |
benzocaine- topical Cocaine- topical Procaine (Novocaine)- injection Tetracaine (Pontocaine)- injection applied topically to skin, mucous membranes |
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Examples Amide LA |
Bupivacaine (marcaine)- injection Dibucaine (Nupercainal)- topical lidocaine (Xylocaine- injection, Lidoderm- topical) Prilocaine (Citanest)- injection
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Ester LA definition |
anesthetic class, includes procaine, cocaine (only naturally occurring drug), benzocaine, tetracaine (only ester w/very long duration action, 3-5 hrs) metabolism primarily by plasma cholinesterases Cocaine Sch II drug- recognized use, restricted. |
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Amide LA definition |
Moderate to long duration of action because metabolism occurs in liver EX: lidocaine bupivicaine mepivicaine administered primarily via injection |
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Potency |
potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity.
EPI often given with LA to keep LA at site of action longer (when site highly vascularized) |
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surface anesthesia |
topical application of LA |
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epidural or caudal blockade |
when LA administered extradurally |
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perineural, paravertebral blockade |
injections around peripheral nerves |
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Spinal blockade |
injection into subarachnoid space (CS fluid) |
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LA preparations that contain EPI |
should not be used for nerve block in areas of fingers , toes, ears, nose, penis may produce intense vasoconstriction, leading to ischemia, gangrene |
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infiltration anesthesia |
Injection of LA directly into tissue extent of anesthesia determined by depth of tissue penetrated lidocaine most commonly used LA used in combination w/EPI can double duration of action |
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regional nerve block |
aka nerve block injection LA near nerve root allow smaller amount Anesthetic to be used, larger area anesthetized, risk of system toxicity reduced Amides (usually 2% lidocaine) most often used |
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La adverse effects |
can be absorbed into blood away from site of administration and affect tissues and organs along the way adjunct medications (EPI) can cause vasoconstriction, HT |
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Cocaine |
produces intense vasoconstriction all other LA used currently produce vasodilation; toxic levels can lead to CV collapse |
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Cardiac effects of LA |
produce negative Chronotropic (rate) ionotropic (contraction) effect on heart lidocaine, procainamide at therapeutic (non-toxic) doses can protect cardiac function (arrhythmias)
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Most frequently used LA for infiltration, peripheral nerve block, caudal/lumbar block |
Bupivicaine Chloroprocaine etidodaine lidocaine mepivacaine ropivacaine |
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Most frequently used LA in dental procedures |
articaine bupivicaine chloroprocaine lidocaine prilocaine |
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La cautions/contraindications |
histamine may be released from mast cells at injection site hypersensitivity (esp ester if used frequently) drug should be stopped immediately in case of rash or edema topical preperations should never be used for prolonged periods |
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precautions in parenteral administration |
CV, respiratory Vital signs should be checked after each injection early signs of CNS toxicity- restlessness, dizziness, blurred vision, slurred speech injection should be slow to avoid systemic reactions If vasoconstrictor included, extreme caution for patients w/HT, cerebral vascular insuffiency, heart block, thyrotoxicosis, diabetes |
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topical applications resulting in convulsions |
acute emergency no antidote keep clear airway, assist ventilation w/oxygen |
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Procaine can inhibit action of what? |
sulfonamide antibiotics |
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LA interactions |
may enhance hypotension that occurs w/antihypertensive drugs, muscle relaxants may increase histamine release, worsening allergic condition
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FDA pregnancy categories? |
B and C |
