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67 Cards in this Set
- Front
- Back
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What 3 factors influence the degree of inhibition conduction of electrical impulses along nerve fibers?
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Anatomy of the nerve being blocked, Local tissue conditions, and physicochemical properties of the LA agent
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How does size of fiber influence onset of block?
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Smaller nerve fibers are more vulnerable to blockade in lower concentrations of local anesthetics. As concentrations are increased, larger nerve fibers are blocked. (LA lecture slide 10)
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Which nerve fibers get blocked first: myelinated or unmyelinated?
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myelinated nerve fibers get blocked faster than unmyelinated nerves
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Which gets blocked first: sensory or motor fibers?
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Sensory fibers are blocked first; Motor fibers are the last to get blocked
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What is the effect of tissue pH on Cm (minimum concentration)?
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increased tissue pH can decrease the Cm, the minimum concentration of local anesthetic necessary to produce conduction blockade of nerve impulses
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At normal physiologic pH, which will have a faster onset: a LA with a pKa of 7.6 or a LA with a pKa of 8?
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the LA with a pKa of 7.6, because it is closer to the physiologic pH, and thus more molecules are unionized
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Which form of the LA (ionized or unionized) crosses the lipid bilayer of the nerve?
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the unionized form
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What is the pKa of chloroprocaine?
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9.0
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What is the pKa of tetracaine?
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8.2
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What is the pKa of bupivacaine (Marcaine)?
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8.1
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What is the pKa of Lidocaine (Xylocaine)?
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7.8
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What is the pKa of mepivacaine (Carbocaine)?
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7.6
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What is the pKa of ropivacaine (Naropin)?
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8.1
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Acid drugs become more _____ (ionized/non-ionized) in acidic pH?
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more non-ionized
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Basic drugs become more _____ (ionized/non-ionized) in alkaline/basic pH?
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more non-ionized
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What three factors determine whether a drug is majority lipophilic or hydrophilic in form?
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(1) Whether the drug is an acid drug or a base drug
(2) the pKa of the drug (3) the pH into which the drug is going to be placed |
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Name 5 ester local anesthetics
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Esters: CCPT:
chloroprocaine (aka 2-chloroprocaine) cocaine procaine tetracaine americaine |
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Name 7 amide local anesthetics
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Amides (two i):
bupivacaine dibucaine etidocaine lidocaine mepivacaine prilocaine ropivacaine |
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Trade name of chloroprocaine?
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Nesacaine
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Trade name of bupivacaine?
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Marcaine
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Trade name of Lidocaine?
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Xylocaine
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Trade name of mepivacaine?
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Carbocaine
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Trade name of ropivacaine?
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Naropin
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Trade name of dibucaine?
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Nupercaine
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Trade name of etidocaine?
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Duranest
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Trade name of prilocaine?
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Citanest
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generic for Marcaine?
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bupivacaine
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generic for Nesacaine?
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chloroprocaine
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generic for Nupercaine?
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dibucaine
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generic for Duranest?
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etidocaine
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generic for Xylocaine?
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lidocaine
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generic for Carbocaine?
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mepivacaine
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generic for Citanest?
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prilocaine
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generic for Naropin?
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ropivacaine
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Name two LA for which adding bicarbonate would not be useful
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bupivacaine (Marcaine) and ropivacaine (Naropin)
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What is normal cerebral metabolic rate (CMR)?
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3-4 ml/100g/min
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What is normal cerebral glucose utilization?
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5 mg/100g/min
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What is average CBF for an adult?
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750 ml/min
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What CBF typically produces a flat EEG?
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15-20 ml/100g/min
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What is the formula for CPP?
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CPP = MAP – ICP (or MAP – RAP, if RAP>ICP)
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What is normal CPP?
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80-100 mmHg
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What three factors are involved in regulation of CBF?
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(1)CPP
(2) Autoregulation (3)Extrinsic mechanisms |
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Because of autoregulation, what is the range of normal cerebral pressure?
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60-160 mmHg
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CBF is proportionate to PaCO2 as long as PaCO2 is in what range?
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20-80 mmHg PaCO2
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How much does blood flow change for every mmHg change in PaCO2?
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1-2 ml/100g/min
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How long does it take to reach equilibrium after acute changes in PaCO2?
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24-48 hours
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Name four extrinsic mechanisms used to adjust CBF.
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(1) Respiratory gases (PaCO2 gas tension is most important)
(2)Temperature (hypothermia decr CMRO2 and thus decreases CBF) (3)Viscosity (a decr in Hct can decr viscosity and incr CBF (4)Autonomic influences (variable input) |
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Which four characteristics govern the movement of substances across the BBB?
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size, charge, lipid solubility and protein binding
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What is the major role of CSF?
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To protect the CNS from trauma
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Where is most CSF formed?
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In the choroid plexus of the lateral ventricles
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What is total CSF volume in the normal adult CNS?
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150 ml
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What is normal CSF production rate per hour? Per day?
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21 ml/hr; 500 ml/day
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What is the relationship between absorption of CSF and ICP?
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Absorption of CSF is proportionate to ICP
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What are the three contents of the cranium and their relative percentages?
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Brain (80%)
Blood (12%) CSF (8%) |
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What is normal ICP in the supratentorium?
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10 mmHg
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What is seen with Cushing’s triad?
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Bradycardia, Hypertension, and irregular or hypo-ventilation
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What does each number represent?
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1. anterior communicating artery
2. anterior cerebral artery 3. carotid 4. posterior communicating artery 5. posterior cerebral artery 6. basilar 7. vertebral |
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pKa determines:
a. potency b. duration c. onset d. toxicity |
c. onset
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protein binding determines:
a. potency b. duration c. onset d. toxicity |
b. duration
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lipid solubility determines:
a. potency b. duration c. onset d. toxicity |
a. potency
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potency is determined by:
a. lipid solubility b. protein binding c. water solubility d. hydrophilic group |
a. lipid solubility
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T/F: all local anesthetics are metabolized by the liver
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false
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local anesthetics:
a. are weak bases b. are water soluble c. block cellular K+ d. are highly toxic |
a. are weak bases
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nerve conduction is blocked:
a. core to mantle b. mantle to core c. distal to proximal d. randomly |
b. mantle to core
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A surgeon asks you how many ml he can use to infiltrate the wound of an 80 kg pt. He has 2% Xylocaine in 1:200,000 epi.
a. 20 ml b. 28 ml c. 8 ml d. as much as needed |
b. 28 ml
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The first clinical manifestation of LA toxicity is?
a. tinnitus b. muscle twitching c. sedation d. seizure |
a. tinnitus
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The unionized local anesthetic molecule:
a. crosses nerve membranes b. blocks K+ efflux c. closes the gating mechanism of the nerve d. determines duration of block |
a. crosses nerve membranes
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