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Pharm > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

Three chemical elements to be a LA

A 
Benzene ring (lipophilic)
Intermediate Chain (ester or amide)
Quaternary Amine (hydrophilic)
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2
Q

Metabolism by plasma and tissue cholinesterase via hydrolysis making them shorter acting

A

Esters

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3
Q

Higher allergy potential and should avoid all if allergy to one

A

Esters

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4
Q

Metabolized in the liver, significant blood level may develop with rapid absorption (lasts longer)

A

Amides

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5
Q

Allergy is rare, no cross allergy among or between class

A

Amides

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6
Q

Longer acting d/t being more lipophilic and protein bound

A

Amides

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7
Q

Have oxygen

A

Esters

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8
Q

Have hydrogen

A

Amides

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9
Q

Which nerves are harder to block

A

Heavy myelination and large diameter

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10
Q

MOA of LA

A

LA is injected into tissue around nerve. Equilibrium is reached outside the nerve and non ionized portion (lipid soluble) enters the nerve.
Once inside the axoplasm the drug reequilibrates and the ionized fraction (hydrophilic) attaches to the LA receptor on the inside of the Na channel blocking Na entry and depolarization.

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11
Q

What is LA distribution

A

Some LA will partake in nonspecific tissue binding in which it diffuses off into tissues (some taken up in bloodstream), is then uptaken and removed.

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12
Q

PKa importance in LA

A

Lower pKa (closer to 7.4) the faster the onset, larger amount of non-ionized

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13
Q

Protein binding significance with LA

A

More protein bound, longer duration of action. If it binds strongly to proteins it is probably binding more to tissues, nerves, and the Na channel and takes longer to be removed from system

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14
Q

What do vasoconstrictors do when given with LA

A

Constrict blood flow to area that you are injecting LA, that way it is not removed as quickly, lasts longer, and causes less bleeding. Decrease rate of vascular absorption

I.e. epinephrine.

Slower onset (stays more local)
Higher degree of motor, sensory blockade
Longer duration
Larger area of blockade
Lower peak plasma concentration (unlike with increased dosing which increases ppc)
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15
Q

MOA of vasoconstrictors in LA

A

Alpha adrenergic receptors in spinal cord are known to activate endogenous analgesic mechanisms

Vasoconstrictive activity

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16
Q

Ion Trapping Causes

A

LA overdose

Respiratory depression leading to hypoxia and acidosis

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17
Q

Ion Trapping MOA

A

acidosis increases ionized fraction of LA. Unable to pass out of BBB so stuck in bracing, prolonging CNS toxicity

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18
Q

What is a risk with LA and a fetus

A

Ion trapping d/t fetal pH being lower than maternal pH. May lead to high levels of LA in fetus

19
Q

What happens when LA is injected into acidotic or infected tissue

A

Rendered ineffective d/t loss of lipid solubility from acidotic environment. Unable to penetrate nerve.

20
Q

Effect of addition of carbonation in LA

A

Speeds onset and intensity of action. CO2 passes through nerve readily and makes inside of nerve more acidotic, increasing ionized fraction of LA in nerve at Na channel

21
Q

Effect of addition of bicarbonate to LA

A

More rapid onset of action by increases pH of solution, increasing non-ionized form of drug, passes through nerve more readily.

Also takes away sting of injection

22
Q

Potency is correlated with

A

Lipid solubility.

Increase lipid solubility, increase amount that diffuses through nerve allowing lower dose needed

23
Q

Time of onset is correlated with…

A

PKa (dissociation constant). Agents with lower pKa/closer to 7.4 are more non-ionized and thus pass more readily

24
Q

Metabolism is correlated with…

A

Chemical linkage

I.e. ester (plasma cholinesterases) or amide (Liver)

25
Q

Duration is correlated with…

A

Protein binding.
Increase protein binding corresponds to higher affinity for Na channel and tissues, prolonging presence of anesthetic in system and at site of action

26
Q

LAST

A

Local Anesthetic Systemic Toxicity

27
Q

Characteristics of LAST

A

Excitation of CNS followed by severe depression (putting nerves in the brain to sleep)

Light headed, tinnitus, tongue numb, metallic taste in mouth—>visual disturbances—>muscular twitching—>convulsions (self limiting)—>unconsciousness—>Coma—>respiratory arrest—>CVS depression

28
Q

Which drug binds preferentially to the heart than to any other tissue in the body making it harder to be released causing cardiac toxicity (doesn’t go through CNS first). Cardiac arrest is first

A

Bupivicaine—>sometimes have to resuscitate for hours or put on bypass

29
Q

Majority of CNS sign in LAST

A

Seizure

30
Q

Majority of CV sign in LAST

A

Bradycardia/Asystole

31
Q

How soon after injection does LAST typically occur?

A

RIGHT AWAY! (Less than 1 minute)

Make sure to have IV in before LA and have emergency equipment available

32
Q

What do you do for seizure from LAST

A

Give benzo (but will add to CNS depression)—>give small amounts of propofol (but will add to respiratory depression)—>give succ (doesn’t stop seizure, but they are self limiting anyways)

33
Q

Ways to prevent LAST

A

Lowest effective dose
Incremental injection
Aspirate prior to each injection
US guidance

34
Q

Treatment of LAST

A 
Airway management in order to prevent hypoxia and acidosis!!!!!!
Seizure management 
Amiodarone if arrhythmia develops
Avoid blockers
Lipid emulsion therapy
35
Q

Lipid emulsion for treatment of LAST

A
  • 1.5 mL/kg 20% lipid bolus
  • Infusion 0.25 ml/kg/min for at least 10 min after CV stability attained
  • CV instability continues?—> 0.5 ml/kg/min
  • up to 10 ml/kg over 30 min for upper limit
36
Q

What is used in order to create faster onset with a longer duration of action and you need to cut the toxic doses in half

A

Mixtures of local anesthetics

37
Q

What happens with LA in pregnancy

A

Enhanced effects of LA, use smaller dose d/t hormones and dilated epidural veins

38
Q

Anesthesia technique that uses up to 35-55 mg/kg of highly diluted lidocaine

A

Tumescent Anesthesia especially used with plastic surgery and liposuction

(No lipophilic—>28ml/kg safe dose)

39
Q

EMLA

A

Eutectic mixture of lidocaine and prolicaine

40
Q

LET

A

Lidocaine-epi-tetracaine

41
Q

TAC

A

Tetracaine-epi-cocaine

42
Q

What to watch out for with topical anesthetics

A

Mucous membrane/non intact skin absorption can lead to toxicity

43
Q

What are Hyaluronidases and adverse effects

A

Drugs that break down hyaluronic acids to help LA spread to father area

Works faster because it spreads farther
Duration is shorter because it is absorbed quicker
Higher chance of toxicity

I.e. vitrase, amphadase, hydrase, hylenex

44
Q

Unique properties of Cocaine

A 
Naturally occurring
Stimulant
Toxic when injected (strictly topical)
Most you can give 200 mg
Blocks erupted of NE into presynaptic membrane

Pharm (24 decks)

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