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FreakinLOCALanesthesia!!! > Part 1-PharmacoDynamicsONE > Flashcards

Part 1-PharmacoDynamicsONE Flashcards

(60 cards)

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1
Q

LA is loss of sensation in a circumscribed area of the body caused by: a depression of excitation of ________, or an inhibition of the conduction process in __________

A

FREE NERVE ENDINGS….peripheral nerves

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2
Q

Some injected anesthetics are ineffective _______

A

topically

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3
Q

________ of action is a major consideration when choosing an anesthetic agent

A

*Duration of action

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4
Q

Is there a local anesthetic that meets ALL the desirable properties? (potency, stability,sterility,onset, duration, etc.)

A

NO! of course not!

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5
Q

How do LA’s work?? Prevent both the _______ and _______ of a nerve impulse

A

generation and conduction

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6
Q

KEYPrimary action of LA in producing conduction block is to DO WHAT???

A

to decrease the permeability of ion channels to SODIUM ions

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7
Q

LA Prevents sodium channels from assuming an _____ or “_____” state

A

active or “open”

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8
Q

Primary effects of LA occur during WHICH phase of an action potential??

A

DEPOLARIZATION

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9
Q

What is the name for the nerve membrane?

A

Neurolemma

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10
Q

________ neurons = thin or single layers of

Schwann cells covering them….What is the relative amount of Na2+ channels?

A

Nonmyelinated…Relatively FEW sodium channels in unmyelinated nerves

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11
Q

What is the outer layer of a neuron underlying its sheath?

A

AXOLEMMA

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12
Q

Hmm DID you know?? Myelin sheath insulates axon both electrically AND ___________*

A

pharmacologically!

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13
Q

What is the ONLY site where molecules of LA have access to the nerve membrane??

A

Nodes of Ranvier

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14
Q

Necessary for at least HOW MANY nodes immediately adjacent to anesthetic solution to be blocked to ensure effective anesthesia (about ___-___mm in coverage)

A

2 to 3 nodes….8-10mm in coverage

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15
Q

What is the main target for LA: sensory or motor nerves?

A

SENSORY

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16
Q

What is faster: an axon with a large diameter or an axon with a small diameter?

A

LARGE = Faster

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17
Q

What is the Fastest type of afferent axon? Slowest?

A

Fastest: A-alpha….Slowest: C

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18
Q

COOL! ______ nerve fibers carry information related to proprioception (muscle sense).

A

A-Alpha (fastest of 4)

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19
Q

COOL! _____ nerve fibers carry information related to touch.

A

A-beta (2nd fastest of 4)

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20
Q

COOL! ______ nerve fibers carry information related to pain and temperature. (sharp pain, pain related to temperature e.g. “ouch” cold or “ouch” hot)

A

A-delta (3rd fastest of 4)

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21
Q

COOL! ____ nerve fibers carry information related to pain, temperature and itch. (dull, aching pain) = easier for LA to affect _________ of these type of fibers!!

A

C-nerve (slowest of 4)…UNMYELINATED

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22
Q

Which ion is the REGULATOR of movement for sodium ions across the nerve membrane?

A

CALCIUM

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23
Q

Release of bound Ca++ ions from ion channel receptor (increases/decreases) sodium permeability of nerve membrane

A

INCREASES

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24
Q

LA molecules may act by _______ _______ with calcium for a site on the nerve membrane*

A

competitive antagonism

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25
LA that produce nerve blockade = "________" nerve block
nondepolarizing
26
LA: Failure to achieve _______ potential level
threshold
27
FUN!!! What are the 3 components to the local anesthetic molecule?
1.Lipohilic (hydrophobic) Aromatic Ring 2.Intermediate ESTER or AMIDE chain 3.Terminal amINE
28
When compared to the ester linkage in the LA molecule, the amide linkage contains an extra _______ to the left of the C=O (carboxyl) group.
NITROGEN
29
When produced in the lab, ALL LOCAL ANESTHETICS are ________ (base?acid?) and are in what state?
WEAK BASES..powdered solids
30
Which component of the LA molecule is soluble in LIPID?
the aromatic ring
31
Which property of the LA molecule correlates with POTENCY because a greater portion of the administered dose can enter the neurons?
Greater LIPID SOLUBILITY
32
What is an example of potency and lipid solubility?
BU-piv-a-caine is more lipid soluble than lidocaine. its prepared as a 0.5% solution vs lido's 2% solution!
33
Which part of the LA molecule is water soluble?
the amino structure
34
INTERESTING!!! The terminal amine in the LA molecule may exist in a _______ form (__ bonds) that is LIPID soluble or as a ________ form (__ bonds) that is positively charged and renders the molecule WATER soluble.
tertiary (3 bonds).....quaternary (4 bonds)
35
Which component of the LA molecule is the "on/off" switch allowing it to exist as lipid soluble OR water soluble?
the Terminal amINE
36
BOOM! Mode of Biotransformation- ESTERS are hydrolyzed by ______ ________.
PLASMA pseudocholinesterase
37
BOOM! Mode of Biotransformation- AMIDES are metabolized in the ______
LIVER
38
What is the weak base of the raw LA molecule added to for stability, storage, and delivery?
the weak base is added to ACID (usually HCl) to form salt
39
Once the weak base is added to acid to make a salt, the pH can be adjusted. ALL ANESTHETIC SOLUTIONS ARE ______ PRIOR TO INJECTION
ACIDIC
40
Salt form of the LA exists in a _______ (tertiary/quaternary), water-soluble state at the time of injection AND WILL NOT _____ the neuron
quaternary...penetrate
41
The time for onset of local anesthesia is therefore predicated on the proportion of molecules that convert to the ______ (tertiary/quaternary), lipid-soluble structure when exposed to physiologic pH of ___.
tertiary...7.4
42
The __________ (___) for the anesthetic predicts the proportion of molecules that exists in each of the lipid/water soluble states.
ionization constant (pKa)
43
INCREASING ____ of the LA solution SPEEDS the onset of action, INCREASES clinical effectiveness and makes the injection more COMFORTABLE!!!
INCREASING pH...(ALKALINIZATION)
44
Ability of LA to block nerve impulses is profoundly altered by changes in ________(extra/intracellular) pH
Extracellular
45
Local anesthetics without vasoconstrictor (epinephrine) have a pH of approximately ____
5.5
46
Those containing epinephrine or other vasoconstrictors are _______ by the manufacturer to inhibit the oxidation of the vasoconstrictor....those containing EPI have a pH of ___
ACIDIFIED...3.3
47
What helps explain the "burning" sensation upon injection and SLOWER rate of onset of LA?
the LA being ACIDIFIED when used with a vasoconstrictor (EPI)
48
The LA sold as salt solution exists simultaneously as uncharged ______ and positively charged ______
uncharged bases....positively charged cations
49
Which form (base/cation) is lipophilic and thus can pass through the membrane?
base
50
Once beyond the influence of the extracellular environment, _____ molecules combine with hydrogen ions to form _____ (RNH+), which are hydro_____
base...cations...hydrophillic
51
WHICH FORM OF THE LA MOLECULE IS THE ONLY FORM THAT CAN BIND TO THE SODIUM ION CHANNEL???
cation (they displace the Ca2+ ions)
52
______ (____) represent the predominant form in LA drug solutions...._____ forms are far less stable
Cations (RNH+)...base less stable
53
Dissociation story: As the drug is injected into the tissues, it is predominantly in the ______ form
cationic (more stable)
54
Dissociation story: after injection....More _____ molecules typically develop in response to normal tissue pH (7.4)
base
55
Dissociation story: Once at the nerve membrane, ______ must convert to ______ in order to pass through
cations to base
56
Dissociation story: Once at the nerve membrane (still outside), in normal tissue pH, equation shifts to favor increase in ____ molecule production, so now more are available for membrane _________*
base...PENETRATION
57
Dissociation story: Once exposed to axoplasm, the equilibrium shifts again, resulting in formation of ______
cations
58
Dissociation story: If adequate numbers of _____ molecules do not penetrate the membrane and convert to ______, profound local anesthesia will not develop
base..........cations
59
Dissociation story: ________ of tissues decreases local anesthetic effectiveness....example inflamed tissue has a pH of ___ to ___ and therefore insufficient numbers of _____ molecules can penetrate the nerve!
acidification.....pH 5-6....base
60
What determines the direction of the dissociation shift of the LA solution when injected?
the pH of the surrounding tissues

FreakinLOCALanesthesia!!! (11 decks)

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