Term
| How do local anesthetics work? |
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Definition
They interrupt irritation & propagation of impulses in axons by blocking Na+ conduction into cell either physically or causing a conformational chnage
blockade is conc-dep and reversible
cell integrity/fxn is unaffected |
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Term
| What are the physical properties of anesthetics? |
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Definition
weak bases/poorly H20 soluble
synthetic: derived from cocaine
hydrophilic and lipophilic ends joined by an ester or amide
aqueous solutions of HCl salts of tertiary amines |
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Term
| What type of fibers are affected first by anesthetics? |
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Definition
small or unmyelinated (B&C)
- large myelinated (A fibers-motor) require larger amounts to be blocked |
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Term
| What is the difference in metabolism between ester and amide anesthetics? |
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Definition
esters: hydrolysis by psuedocholinestserase
amides: metabolized by liver enzyme |
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Term
| How does pKA affect the onset of anesthetics? |
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Definition
anesthetic must be in un-ionized form for nerve penetration; the cation form delays onset of action
high pKA= slow onset |
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Term
| What are the symptoms of anesthetic toxicity? |
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Definition
initially: light headedness, dizziness, visual/aud disturbances, disorientation, drowsiness
higher doses: muscle twitching, convulsions, unconsciousness, coma, resp deperssion & arrest, CV depression & collapse
cardiac: myocardial depression, cardiac arrythmias, cardiotoxicity in pregnancy, negative inotrope (hypotension)
periph: vasoconstriction at low doses, vasodilation at high doses
methemoglobinemia
muscle necrosis (spont reversed in ~ 2 wks)
allergic rxns |
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Term
| How is anesthetic toxicity treated? |
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Definition
| stop injection, open airway/O2, seizures: benzodiazepene, CPR, intralipid (for bupivicane assoc cardiac arrest), methylene blue for methemoglobulinemia |
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Term
|
Definition
naturally occurring anesthetic
vasoconstriction (blocks catech reuptake)
onset: 4-5min
AE: abuse |
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Term
procaine
tetracaine
2-cholorporcaine
benzocaine |
|
Definition
esters
procaine: excreted by kidneys
tetracaine: high pKa/slow onset, long duration,excellent topical
2-cholor: 45-60 min duration but AE: thrombophlebitis, safest toxicity
benzocaine: effective only in high conc, used mostly in mucus membranes AE: methemoglobinemia |
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Term
| which ester anesthetic has the safest toxicity? |
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Definition
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Term
| Which ester anesthetic is good for topical use? |
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Definition
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Term
| Which ester anesthetic has an AE of methemoglobinemia? |
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Definition
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Term
|
Definition
| an amide; metab in liver and excreted by kidneys |
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Term
|
Definition
an amide
high potency/toixicity; inhibits plasma cholinesterase
topical use only |
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Term
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Definition
similar to lidocaine but less vasodilation
useful in epidural, spinal, periph nerve blocks, local infiltration
AE: potential for accumulation, so unsuitable for prolonged epidural infusion |
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Term
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Definition
greater potency/duration, but slow onset
good for spinal anesthesia as isobaric or hyperbaric solution
significant frequency-dependent block
AE: cardiac toxicity |
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Term
| Which anesthestics are good for spinal anesthesia? |
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Definition
|
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Term
| Which anesthetics cause frequency-dependent block? |
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Definition
| bupivicaine and ropivicaine |
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Term
| What anesthetics cause methemoglobinemia? |
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Definition
| benzocaine and prilocaine |
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Term
| How do epinephrine and bicarbonate affect anesthetics? |
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Definition
epi: decreases absorption (via local vasoconstriction) and prolongs duration
bicarbonate: increases pH of solution and accelerates the onset, but may decrease duration; may precipitate ropivicaine and bupivacaine |
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Term
| What local anesthetics are used topically? |
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Definition
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Term
| What drug is used for epidural, spinal and peripheral nerve block, and what are it's risks? |
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Definition
mepivocaine
risk of accumulation, so it is unsuitable for epidural infusion |
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Term
| Which local anesthetics can cause methemoglobinemia? |
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Definition
| benzocaine and prilocaine |
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Term
| Which local anesthetic is cardiotoxic? |
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Definition
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Term
| Which local anesthetic can cause thrombophlebitis? |
|
Definition
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