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FreakinLOCALanesthesia!!! > Part 1-PharmacoDynamicsONE > Flashcards

Part 1-PharmacoDynamicsONE Flashcards

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
Q

LA that produce nerve blockade = “________” nerve block

A

nondepolarizing

26
Q

LA: Failure to achieve _______ potential level

A

threshold

27
Q

FUN!!! What are the 3 components to the local anesthetic molecule?

A

1.Lipohilic (hydrophobic) Aromatic Ring 2.Intermediate ESTER or AMIDE chain 3.Terminal amINE

28
Q

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.

A

NITROGEN

29
Q

When produced in the lab, ALL LOCAL ANESTHETICS are ________ (base?acid?) and are in what state?

A

WEAK BASES..powdered solids

30
Q

Which component of the LA molecule is soluble in LIPID?

A

the aromatic ring

31
Q

Which property of the LA molecule correlates with POTENCY because a greater portion of the administered dose can enter the neurons?

A

Greater LIPID SOLUBILITY

32
Q

What is an example of potency and lipid solubility?

A

BU-piv-a-caine is more lipid soluble than lidocaine. its prepared as a 0.5% solution vs lido’s 2% solution!

33
Q

Which part of the LA molecule is water soluble?

A

the amino structure

34
Q

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.

A

tertiary (3 bonds)…..quaternary (4 bonds)

35
Q

Which component of the LA molecule is the “on/off” switch allowing it to exist as lipid soluble OR water soluble?

A

the Terminal amINE

36
Q

BOOM! Mode of Biotransformation- ESTERS are hydrolyzed by ______ ________.

A

PLASMA pseudocholinesterase

37
Q

BOOM! Mode of Biotransformation- AMIDES are metabolized in the ______

A

LIVER

38
Q

What is the weak base of the raw LA molecule added to for stability, storage, and delivery?

A

the weak base is added to ACID (usually HCl) to form salt

39
Q

Once the weak base is added to acid to make a salt, the pH can be adjusted. ALL ANESTHETIC SOLUTIONS ARE ______ PRIOR TO INJECTION

A

ACIDIC

40
Q

Salt form of the LA exists in a _______ (tertiary/quaternary), water-soluble state at the time of injection AND WILL NOT _____ the neuron

A

quaternary…penetrate

41
Q

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 ___.

A

tertiary…7.4

42
Q

The __________ (___) for the anesthetic predicts the proportion of molecules that exists in each of the lipid/water soluble states.

A

ionization constant (pKa)

43
Q

INCREASING ____ of the LA solution SPEEDS the onset of action, INCREASES clinical effectiveness and makes the injection more COMFORTABLE!!!

A

INCREASING pH…(ALKALINIZATION)

44
Q

Ability of LA to block nerve impulses is profoundly altered by changes in ________(extra/intracellular) pH

A

Extracellular

45
Q

Local anesthetics without vasoconstrictor (epinephrine) have a pH of approximately ____

A

5.5

46
Q

Those containing epinephrine or other vasoconstrictors are _______ by the manufacturer to inhibit the oxidation of the vasoconstrictor….those containing EPI have a pH of ___

A

ACIDIFIED…3.3

47
Q

What helps explain the “burning” sensation upon injection and SLOWER rate of onset of LA?

A

the LA being ACIDIFIED when used with a vasoconstrictor (EPI)

48
Q

The LA sold as salt solution exists simultaneously as uncharged ______ and positively charged ______

A

uncharged bases….positively charged cations

49
Q

Which form (base/cation) is lipophilic and thus can pass through the membrane?

A

base

50
Q

Once beyond the influence of the extracellular environment, _____ molecules combine with hydrogen ions to form _____ (RNH+), which are hydro_____

A

base…cations…hydrophillic

51
Q

WHICH FORM OF THE LA MOLECULE IS THE ONLY FORM THAT CAN BIND TO THE SODIUM ION CHANNEL???

A

cation (they displace the Ca2+ ions)

52
Q

______ (____) represent the predominant form in LA drug solutions…._____ forms are far less stable

A

Cations (RNH+)…base less stable

53
Q

Dissociation story: As the drug is injected into the tissues, it is predominantly in the ______ form

A

cationic (more stable)

54
Q

Dissociation story: after injection….More _____ molecules typically develop in response to normal tissue pH (7.4)

A

base

55
Q

Dissociation story: Once at the nerve membrane, ______ must convert to ______ in order to pass through

A

cations to base

56
Q

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 _________*

A

base…PENETRATION

57
Q

Dissociation story: Once exposed to axoplasm, the equilibrium shifts again, resulting in formation of ______

A

cations

58
Q

Dissociation story: If adequate numbers of _____ molecules do not penetrate the membrane and convert to ______, profound local anesthesia will not develop

A

base……….cations

59
Q

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!

A

acidification…..pH 5-6….base

60
Q

What determines the direction of the dissociation shift of the LA solution when injected?

A

the pH of the surrounding tissues

FreakinLOCALanesthesia!!! (11 decks)

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