Local Anesthetics III (Exam IV)

Question 1

How rare are local anesthetic reactions?

Answer 1

< 1% occurrence

-Mild to IgE anaphylaxis.

Question 2

What local anesthetic class is responsible for more allergic reactions?

Answer 2

Esters (PABA metabolite) > amides.

Question 3

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

Answer 3

Methylparaben - preservative to both esters & amides.

(similar in structure to PABA)

Question 4

Is there a cross-sensitivity between esters and amides?

Answer 4

No

Question 5

How can one be tested for local anesthetic allergy?

Answer 5

Intradermal testing using preservative free LA

Question 6

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

Answer 6

IgE anaphylaxis

Question 7

Clinical manifestations of an allergic reaction?

Time course of allergic reaction?

Answer 7

rash, urticaria, and laryngeal edema with or without hypotension & bronchospasm.

immediate vs. delayed.

Question 8

Management of allergic reaction?

Answer 8

stop administration
supportive care (airway, O2, fluids)
epinephrine, antihistamine, corticosteroids

Question 9

What is LAST?

Answer 9

Local Anesthetic Systemic Toxicity

Question 10

What causes LAST syndrome?

Answer 10

Excess plasma concentration of LA from:
- Accidental direct IV injection
- Systemic absorption from tissue redistribution and clearance metabolism.

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Trachea has higher chance of systemic absorption.

Question 13

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

Answer 13

Question 14

What serum electrolyte condition will exacerbate local anesthetic toxicity?
Why?

Answer 14

Hyperkalemia (lowers seizure threshold) - so it promotes seizures.

Question 15

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

Answer 15

Drowsiness and facial twitching

Question 16

LAST: CNS effects seen:

Answer 16

Early agitation & 1-10 mcg/mL

Question 17

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

Answer 17

Analgesia

Question 18

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

Answer 18

• Mouth numbness
• Tinnitus
• Muscle twitching
• ↓BP
• Myocardial depression

Question 19

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

Answer 19

• Seizures
• Unconsciousness

Question 20

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

Answer 20

• Apnea
• Coma

Question 21

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

Answer 21

Cardiovascular Depression

Question 23

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

Answer 23

• Prolongation of PR interval and QRS widening.
• Blockade of Na⁺ channels

Question 24

What can occur if Bupivacaine is given intravenously?

Answer 24

• Significant ↓BP
• AV block
• Cardiac Dysrhythmias (SVT, ST-T wave changes, PVCs, widening QRS, V-tach –> cardiac arrest)

Question 25

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

Answer 25

- β-blockers, CCBs, digoxin - Epi and Phenylephrine

Question 26

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

Answer 26

Pregnancy = ↓ plasma cholinesterases

Question 27

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

Answer 27

- ↓ plasma esterases - ↓ plasma proteins

Question 28

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

Answer 28

Bupivacaine > Ropivacaine > Lidocaine

Question 29

Prediposing factors: Acid/base balance?

Answer 29

Arterial hypoxemia, acidosis, or hypercarbia (in animals)

Question 30

LAST treatment?

Answer 30

1. Stop LA immediately 2. call for help 3. 100% O2 4. Hyperventilation 5. Sedation: barb or propofol 6. Epinephrine as an additive

Question 31

Why is 100% O₂ given for LA toxicity?

Answer 31

To inhibit hypoxemia and metabolic acidosis

Question 32

What drugs are used to treat LA induced seizures?

Answer 32

- Benzodiazepines - Propofol (if BP is okay) - Muscle relaxants (suxx or NDMB) - Epinephrine - Intralipid

Question 33

How does Lipid Emulsion rescue work?

Answer 33

Creates a lipid compartment; *fat for myocardial metabolism*.

Question 34

What is the bolus dose of Lipid Emulsion?

Answer 34

1.5 mL/kg of 20% lipid emulsion

Question 35

What is the infusion dose of lipid emulsion? How long should it be given?

Answer 35

0.25 mL/kg/minute for at least 10 minutes

Question 36

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

Answer 36

10 mL/kg

Question 37

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

Answer 37

3.8 mL/kg (1.2 to 6 mL/kg) *Answer is from a study in the book*.

Question 38

What is the epinephrine dose for lipid emulsion?

Answer 38

10 to 100 mcg

Question 39

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

Answer 39

Cardiopulmonary Bypass (CPB)

Question 40

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

Answer 40

No

Question 41

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

Answer 41

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

Question 42

**This card is here just to view the LAST algorithm**.

Answer 42

Question 43

(0.5% = 5mg/mL x 20 mL)

Answer 43

120 lbs =54.5 kg so 1.5mLs x 54.5 kg = 81.75 mLs 20% infusion = 200mgs / 1mL 81.75 mLs x 200mgs = **16,350mgs** administered

Question 44

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

Answer 44

- Transient Neurological Symptoms - Cauda Equina Syndrome - Anterior Spinal Artery Syndrome

Question 45

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

Answer 45

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

Question 46

What LA is most often the cause of TNS?

Answer 46

Lidocaine

Question 47

What is the treatment for TNS?

Answer 47

- Trigger point injections - NSAIDs

Question 48

How long is the recovery from Transient neurologic symptoms (TNS)?

Answer 48

1-7 days

Question 49

What is Cauda Equina Syndrome (CES) ?

Answer 49

Diffuse injury @ lumbosacral plexus

Question 50

What causes CES?

Answer 50

spinal anesthesia & high concentration, compression, or ischemia of cauda equina.

Question 51

What are the s/s of CES?

Answer 51

- Varying degrees of sensory anesthesia - Bowel & bladder dysfunction sphincter dysfunction - weakness -paraplegia

Question 52

What conditions are associated with CES?

Answer 52

- Lumbar disc herniation, prolapse or sequestration w/ urinary retention

Question 53

What is the cause of Anterior Spinal Artery Syndrome?

Answer 53

- Thrombosis and/or vasospasm of the anterior spinal artery - ↓BP or vasoconstrictor drugs; PVD, Spinal cord compression d/t epidural abscess or hematoma.

Question 54

What are the s/s Anterior Spinal Artery Syndrome?

Answer 54

Lower extremity paresis w/ variable sensory deficit (no pain/temperature, yes proprioception)

Question 55

What is Methemoglobinemia?

Answer 55

Life-threatening condition where O₂ carrying capacity is decreased due to MetHgb > 15% this causes cyanosis d/t the FE^3+ cannot bind to oxygen.

Question 56

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

Answer 56

- Prilocaine & Benzocaine > lidocaine, nitroglycerine, phenytoin, & sulfonamides.

Question 57

What is the treatment for methemoglobinemia?

Answer 57

Methylene blue 1mg/kg over 5min

Question 58

What is the max dosage of methylene blue?

Answer 58

7 to 8 mg/kg

Question 59

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

Answer 59

20 - 60 min

Question 60

Lidocaine _________ the ventilatory response to arterial hypoxemia. What patient population is most susceptible to this?

Answer 60

depresses CO₂ retaining patients (COPD)

Question 61

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

Answer 61

Hepatic toxicity *Stopping bupivacaine infusion normalizes liver transaminase enzymes*

Question 62

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

Answer 62

A. Call for help then D, C, and B last

Question 63

What is Cocaine's MOA?

Answer 63

Blocks presynaptic reuptake of NorEpi and Dopamine → Increases postsynaptic levels of NorEpi and dopamine.

Question 64

CV adverse effects with cocaine toxicity? how long can adverse effect last?

Answer 64

- HTN, tachycardia, coronary vasospasm, MI ( infarction & ischemia), ventricular dysrhythmias (VFIB) - Adverse effects can last up to 6 weeks

Question 65

What does parturient mean?

Answer 65

Woman in labor

Question 66

What can cocaine do to a parturient patient?

Answer 66

↓ uterus blood flow = fetal hypoxia

Question 67

What is the algorithm for cocaine-associated chest pain?

Answer 67

Question 68

Treatment for cocaine toxicity? What medications would be avoid?

Answer 68

benzodiazepines, nitroglycerin Avoid beta-blockers.