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LA1 Flashcards

1
Q

LA ———-(continue/cease) to provide their clinical effect when they are absorbed into the circulation.

A

LA cease to provide their clinical effect when they are absorbed into the circulation.

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2
Q

Classification of Local Anesthetics

A
  1. Esters
  2. Amides
  3. Quinolines
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3
Q

Esters:

A 
Butacaine
Cocaine
Benzocaine
Hexilcaine
Piperocaine
Tetracaine
Chloroprocaine
Procaine
Propoxicaine
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4
Q

Amides

A 
Articaine
●Bupivacaine
●Dibucaine
●Etidocaine
●Lidocaine
●Mepivacaine
●Prilocaine
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5
Q

Quinoline

A

Centbucridine

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6
Q

———- is the most potent vasodilator

A

Procaine

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7
Q

———— is the only LA that produces vasoconstriction

A

Cocaine is the only LA that produces vasoconstriction

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8
Q

All local anesthetics posses a degree of vasoactivity, most producing ———— (vasodilatation/vasoconstriction)

A

vasodilatation

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9
Q

With the exception of ———-, local anesthetic drugs are absorbed poorly from the ———- following oral administration.

A

cocaine, gastrointestinal tract

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10
Q

First Pass Effect of LA

A

50 to 90% of the absorbed drug is metabolized on the first pass through the liver

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11
Q

———-, uptake of LA is almost as rapid as IV administration.

A

Tracheal mucosa

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12
Q

when applied to intact skin, they ——(have/do not have) an anesthetic action

A

intact skin, they do NOT have an anesthetic action

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13
Q

———has been developed to provide surface anesthesia for intact skin

A

Eutectic mixture of local anesthetics(EMLA)

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14
Q

The rate of absorption after parenteral administration is related to both the ———- of the injection site and the ——- of the drug

A

vascularity and the vasoactivity

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15
Q

——-administration provides the most rapid elevation of blood levels of LA

A

IV

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16
Q

IV administration of LA is used in the primary treatment of ventricular dysrhythmias.Why.

A

IV administration provides the most rapid elevation of blood levels

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17
Q

All LA cross the blood brain barrier and the placenta. T/F

A

T.

All LA cross the blood brain barrier and the placenta

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18
Q

Blood level of LA depends on:

A

–rate of absorption into CVS
–rate of distribution
–elimination of the drug

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19
Q

Ester local anesthetics are hydrolyzed in the ——- by the enzyme ————.

A

plasma, enzyme pseudocholinesterase.

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20
Q

————- Causes an inability to hydrolyze ester local anesthetics

A

Atypical Pseudocholinesterase

Incidence: 1 out of every 2800 persons

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21
Q

Toxicity depends on:

A

rate of absorption into the bloodstream at the site of injection
–rate of removal from the blood through the processes of tissue uptake and metabolism

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22
Q

The primary site of biotransformation of amide drugs is the liver.

A

liver

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23
Q

During bio transformation, ——- (Amides/ Esters) are usually present as the parent compound in greater percentage than ——- (Amides/ Esters).

A

Amides are usually present as the parent compound in greater percentage than esters.

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24
Q

Slower than normal biotransformation rate leads to _______anesthetic blood levels and potentially ___ toxicity

A

increased and potentially increases toxicity

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25
Q

Slower than normal biotransformation rate effects on systems:

A

-Hypotension
-Congestive heart failure (CHF)
-Poor liver function:
Cirrhosis

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26
Q

It usually takes____ half lives to eliminate a drug from the system

A

6

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27
Q

One half-life =

A

50% reduction

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28
Q

Two half-lives =

A

75% reduction

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29
Q

Three half-lives =

A

87.5% reduction

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30
Q

Four half-lives =

A

94% reduction

31
Q

Five half-lives =

A

97% reduction

32
Q

Six half-lives =

A

98.5% reduction

33
Q

The ____ are the primary excretory organ for both the local anesthetics and its metabolites.

A

kidneys

34
Q

T/F:

A percentage of a given dose of local anesthetic drug will be excreted unchanged in the urine

A

T

35
Q

Pure localanesthetics are basic compounds that are__(soluble/poorly soluble) in water

A

poorly soluble

36
Q

pKa values of pure LA where they have no clinical value

A

Pure LA: pKa values range

7.5 to10

37
Q

Why are local anesthetics used for injection are dispensed as acid salts

A
  • localanesthetics are basic compounds that arepoorly soluble in water
  • because they are weakly basic, they combine readily with acids to form local anesthetic salts, in which form they are quite soluble in water and comparatively stable.
38
Q

Most common salt in which LAs are dispensed

A

hydrochloride salt (e.g., lidocaine HCl, articaine HCl), dissolved in sterile water or saline.

39
Q

The local anesthetic salt, (both water soluble and stable,)is dissolved in ____

A

sterile water or saline

40
Q

Local anesthetic salt, exists simultaneously as uncharged molecules (RN), also called the __,and positively charged molecules(RNH+), called the____.

A

Unchanged: base

+ : cation

41
Q

The relative proportion of eachionic form of LA salt in the solution varies with _____

A

the pHof the solution or surrounding tissues.

42
Q

In the presence of a highconcentration of hydrogen ions (low pH), the equilibrium shifts to the left, and most of the anesthetic solution exists in ___ form

A

cationic

43
Q

As hydrogen ion concentration decreases (higher pH), the equilibrium shifts toward the ___ form

A

free base

44
Q

_____is a measure of the affinity of amolecule for hydrogen ions (H+).

A

pKa

45
Q

The relative proportion of ionic forms also depends on the _____ of the specific local anesthetic.

A

pKa, or dissociation constant,

46
Q

When the__of the solution has the same value as the ____of the local anesthetic, exactly50% of the drug exists in the RNH+form and 50% in the RN form

A

pH, pKa

47
Q

The percentage of drug existing in either form can be determined from the _____ equation

A

Henderson-Hasselbalch equation

48
Q

pHof a ____ , as well as thepH of ____ greatly influences its nerve-blocking action

A

local anesthetic solution

pH of the tissue injected

49
Q

_____ of tissue decreaseslocal anesthetic effectiveness

A

Acidification

50
Q

Inadequate anesthesia results when local anesthetics areinjected into _____ or ____ areas

A

inflamed or infected areas

51
Q

Most systemic reactions are related to the ____ level of the local anesthetic

A

plasma level

52
Q

Systemic Actions of LA on CNS

A
  1. Anticonvulsant properties (0.5-4 µg/ml).: raise the seizure threshold
  2. Preconvulsive Phase (4.5-7µg/ml): Direct depressant action of the local anesthetic on the CNS
  3. Convulsive Phase (>7.5 µg/ml): Further elevation of the local anesthetic blood level produces clinical signs and symptoms consistent with a generalized tonic-clonic convulsive episode (>7.5 µg/ml)
  4. Final Stage:
    Both inhibitory and facilitory impulses are totally depressed, producing general CNS depression
53
Q

Preconvulsive Phase due to LA

A
  1. 5-7µg/ml).
    - Slurred speech
    - shivering
    - muscular twitching
    - tremor in muscle of face and distal extremities
54
Q

Systemic Actions of LA on CVS

A

Cardiovascular System
Local anesthetic drug action
-decreases electrical excitability of the myocardium,

  • decreases conduction rate, and
  • decreases the force of contraction.
55
Q

Sequence of LA – Induced Actions on the CVS

A
  1. At nonoverdose levels, a slight increase to no change in BP
  2. At levels approaching yet still below overdose, a mild degree of hypotension is noted;
  3. At overdose levels, profound hypotension is caused by decreased myocardial contractility, cardiac output, and peripheral resistance
  4. At lethal levels, cardiovascular collapse is noted.
56
Q

At nonoverdose levels, why does a slight increase to no change in BP occur?

A

because of increased CO and HR as a result of enhanced sympathetic activity: direct vasoconstriction of certain peripheral vascular beds is noted

57
Q

At levels approaching yet still below overdose, why is a mild degree of hypotension is noted?

A

direct relaxant action on the vascular smooth muscle

58
Q

At overdose levels, why is there profound hypotension ?

A

due to decreased myocardial contractility, cardiac output, and peripheral resistance

59
Q

Certain local anesthetics such as _____ may precipitate potentially fatal ventricular fibrillation

A

bupivacaine (and to a lesser degree ropivacaine and etiodocaine)

60
Q

_____ muscles are more sensitive to the local irritant properties of local anesthetics

A

Skeletal muscle

61
Q

_____ (longer-acting/shorter-acting) local anesthetics cause more localized skeletal muscle damage than (longer-acting/shorter-acting) LAs

A

longer-acting local anesthetics&raquo_space; more skeletal muscle damage

than shorter-acting drugs

62
Q

The skeletal muscle LA changes are reversible, with muscle regeneration being complete within __ (time)

A

2 weeks

63
Q

Effect of LA at non-overdose levels, on respiratory system

A

direct relaxant action on bronchial smooth muscle

64
Q

Effect of LA at overdose levels, on respiratory system

A

respiratory arrest as a result of generalized CNS depression.

65
Q

T/F: In general, respiratory function is unaffected by local anesthetics until near-overdose levels are achieved

A

T

66
Q

CNS depressants (e.g., opioids, antianxietydrugs, phenothiazines, barbiturates), when administered in conjunction with local anesthetics, lead to___of the CNS-depressant actions of the local anesthetic

A

CNS depressants&raquo_space;>potentiation&raquo_space;>more depression

67
Q

Both ester local anesthetics and the depolarizing muscle relaxant succinylcholine require plasma _____ for hydrolysis.

A

pseudocholinesterase

68
Q

Prolonged _____may result from concomitant use of CNS depressants

A

apnea

69
Q

Drugs that induce the production ofhepatic microsomal enzymes (e.g., barbiturates) may alter therate at which ____ (amide/ester) local anesthetics are metabolized.

A

Amide

70
Q

Increased/Decreased)_____ hepatic microsomal enzyme induction increases the rate of metabolism of the local anesthetic

A

Increased

71
Q

Malignant Hyperthermia: Acute clinical manifestations include:

A

tachycardia, tachypnea, unstable bloodpressure, cyanosis, respiratory and metabolic acidosis, fever (as high as 42° C [108° F] ormore), muscle rigidity, and death

72
Q

Factors in Selection of Local Anesthetic

A
  1. Length of time that pain control is required
  2. Potential for discomfort in the post- treatment period
  3. Requirement for hemostasis during treatment
  4. Medical status of the patient
73
Q

Duration of Anesthesia

A
  • Individual patient variation
  • Accuracy in administration
  • Anatomical variation
  • Type of injection administered

Pain (3 decks)

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