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Anesthesia Pharm (Spring '24) - A > Local Anesthetics III (Exam IV) > Flashcards

Local Anesthetics III (Exam IV) Flashcards

1
Q

How rare are local anesthetic reactions?

A

< 1% occurrence

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2
Q

What class of local anesthetics is responsible for more allergic reactions?

A

Esters (due to PABA (para-aminobenzoic acid) metabolite)

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3
Q

What preservative commonly used for esters and amide local anesthetics is usually responsible for allergies?

A

Methylparaben (broken down into PABA)

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4
Q

Is there a cross-sensitivity between esters and amides?

A

No

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5
Q

How can one be tested for local anesthetic allergy?

A

Intradermal testing using preservative free LA

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6
Q

What is the most serious complication of allergies to local anesthetics?

A

IgE anaphylaxis

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7
Q

What is LAST?

A

Local Anesthetic Systemic Toxicity

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8
Q

What causes LAST syndrome?

A

Excess plasma concentration of LA from:

  • Accidental IV injection
  • Systemic absorption from tissue redistribution and clearance metabolism.
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9
Q

What factors affect the magnitude of systemic absorption of local anesthetic?

A
  • Dose
  • Vascularity of site
  • Concurrent Epi use
  • Properties of the drug itself
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10
Q

Would local anesthetic administered via the trachea have a higher or lower chance of systemic absorption than local anesthetic delivered brachially?

A

Trachea has higher chance of systemic absorption.

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11
Q

Compare and contrast the different areas of local anesthetic administration based on resultant blood concentrations.

A
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12
Q

What serum electrolyte condition will exacerbate local anesthetic toxicity leading to seizures?
Why?

A

Hyperkalemia (lowers seizure threshold)

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13
Q

What CNS s/s will forebode local anesthetic induced seizures?

A

Drowsiness and facial twitching

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14
Q

What s/s would be seen with a plasma lidocaine concentration of 1-5 mcg/ml?

A

Analgesia

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15
Q

What s/s would be seen with a plasma lidocaine concentration of 5-10 mcg/ml?

A
  • Mouth numbness
  • Tinnitus
  • Muscle twitching
  • ↓BP
  • Myocardial depression
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16
Q

What s/s would be seen with a plasma lidocaine concentration of 10-15 mcg/ml?

A
  • Seizures
  • Unconsciousness
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17
Q

What s/s would be seen with a plasma lidocaine concentration of 15-25 mcg/ml?

A
  • Apnea
  • Coma
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18
Q

What s/s would be seen with a plasma lidocaine concentration of >25 mcg/ml?

A

Cardiovascular Depression

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19
Q

How does lidocaine affect EKGs?
How does it do this?

A
  • Prolongation of PR interval and QRS widening -

Slows conduction of impulses:
- Blockade of Na⁺ channels

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20
Q

What can occur if Bupivacaine is given intravenously?

A
  • Significant ↓BP
  • Cardiac Dysrhythmias: ST-Twave changes, widening of QRS, PVCs, SVTs, V-tach
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21
Q

What drugs will predispose patients to cardiovascular effects of LA systemic toxicity?

A
  • β-blockers, CCBs, digoxin
  • Epi and Phenylephrine
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22
Q

Why does pregnancy predispose one to cardiovascular toxicity from LA’s?

A

Pregnancy = ↓ plasma cholinesterases

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23
Q

Which two factors predispose our OB population to local anesthetic toxicity?

A
  • ↓ plasma esterases
  • ↓ plasma proteins
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24
Q

Which three drugs are most responsible for cardiac adverse effects when reaching toxic levels systemically?

A

Bupivacaine > Ropivacaine > Lidocaine

(Amides)

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25
Q

Should a local anesthetic toxicity patient be hyperventilated or hypoventilated?

A

Hyperventilation = ↓ CO₂ = ↓ acidosis

26
Q

Why is 100% O₂ given for LA toxicity?

A

To inhibit hypoxemia and metabolic acidosis

27
Q

What drugs are used to treat LA induced seizures?

A
  • Benzodiazepines
  • Propofol (if BP is okay)
  • Muscle relaxants
  • Epinephrine
  • Lipid Rescue
28
Q

How does Lipid Emulsion rescue work?

A

Lipids encapsulate the local anesthetic and transport it away from cardiac and CNS tissue.

Also provides fat for myocardial metabolism.

29
Q

What are the 3 types dose rates for Lipid Emulsion?

A

Bolus: 1.5 mL/kg of 20% lipid emulsion

IV: 0.25 mL/kg/minute for at least 10 minutes

1st 30 min should have received: 3.8 mL/kg (1.2-1.6 mg/kg)

30
Q

What is the max dose for lipid emulsion that should be given?

A

8 mL/kg

31
Q

What is the dose for lipid emulsion that should be given in the 1st 30 minutes?

A

3.8 mL/kg

Answer is from a study in the book.

32
Q

What would be the last resort therapy for a patient with severe LAST syndrome in which lipid rescue and ACLS have failed?

A

Cardiopulmonary Bypass

33
Q

Can propofol be used as a substitute for a lipid emulsion?

A

No

34
Q

If cardiac arrest occurs with LAST syndrome, how should our epinephrine dosing change?

A

Small doses (10mcg - 100mcg boluses) are preferred with LAST ACLS.

35
Q

How much vasopressin should be given if a patient is suffering from hypotension from LAST syndrome?

A

Trick question. Vasopression should not be given with LAST syndrome.

36
Q

This card is here just to view the LAST algorithm.

A
37
Q
A

56kg so 1.5mLs x 56kg = 84mLs

20% infusion = 200mgs / 1mL

84mLs x 200mgs = 16,800mgs administered

38
Q

What are the three categories of neural tissue toxicity associated with LA toxicity?

A
  • Transient Neurological Symptoms
  • Cauda Equina Syndrome
  • Anterior Spinal Artery Syndrome
39
Q

What are the s/s of Transient Neurological Symptoms (TNS) ?

A

Moderate to severe pain in the lower back, buttocks, or posterior thighs within 6 - 36 hours post uneventful spinal block.

40
Q

What LA is most often the cause of TNS?

A

Lidocaine

41
Q

What is the treatment for TNS?

A
  • Trigger point injections
  • NSAIDs
42
Q

How long does TNS typically last?

A

1-7 days

43
Q

What is Cauda Equina Syndrome (CES) ?

A

Diffuse injury @ lumbosacral plexus

44
Q

What are the s/s of CES?

A
  • Varying degrees of sensory anesthesia
  • Bowel & bladder sphincter dysfunction
  • Paraplegia
45
Q

What conditions are associated with CES?

A
  • Lumbar disc herniation
  • Bladder prolapse or sequestration w/ urinary retention
46
Q

What is the cause of Anterior Spinal Artery Syndrome?

A
  • Thrombosis and/or spasm of the bilateral anterior spinal artery
  • ↓BP
  • Vasoconstrictors
  • PVD
  • Spinal cord compression (hematoma/abscess)
47
Q

What are the s/s Anterior Spinal Artery Syndrome?

A

Lower extremity paresis w/ variable sensory deficit

48
Q

What is Methemoglobinemia?

A

Life-threatening condition where O₂ carrying capacity is decreased due to MetHgb > 15% (Hb has ferric iron instead of ferrous)

49
Q

Which two LA’s are most often the culprits of methemoglobinemia?

A
  • Prilocaine
  • Benzocaine

Others: greater than lidocaine

50
Q

What is the treatment for methemoglobinemia?

A

Methylene blue 1mg/kg over 5min

51
Q

What is the max dosage of methylene blue?

A

8 mg/kg

52
Q

How long does the reversal from MetHgb (Fe⁺⁺⁺) to Hgb (Fe⁺⁺) typically take?

A

20 - 60 min

53
Q

Lidocaine _________ the ventilatory response to arterial hypoxemia.

What patient population is most susceptible to this?

A

depresses

CO₂ retaining patients (COPD)

54
Q

Continuous or intermittent epidural bupivacaine to treat post-herpetic neuralgia can cause what?

A

Hepatic toxicity

Stopping bupivacaine infusion normalizes LFTs quickly.

55
Q

The most common first intervention when an adverse event is identified is for the anesthesia provider to…

A. Call for help.
B. Administer the antidote
C. Discontinue the causative agent
D. Airway, Breathing, Circulation

A

A. Call for help

then D, C, and B last

56
Q

What is Cocaine’s MOA?

A

Blocks presynaptic re-uptake of NE and Dopamine → Increases postsynaptic levels and ↑SNS.

57
Q

What does parturient mean?

“Parturienta” in Spanish, but sounds really tacky.

A

Woman in labor

58
Q

What can cocaine do to a parturient patient?

A

↓ uterus blood flow = fetal hypoxia

59
Q

What is the algorithm for cocaine-associated chest pain?

A
60
Q

What drug is best for cocaine toxicity?

A

Nitroprusside

Anesthesia Pharm (Spring '24) - A (20 decks)

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