Local Anesthetics III (Exam IV)

Question 1

How rare are local anesthetic reactions?

Answer 1

< 1% occurrence

Attributed to manifestations of excess plasma levels

S6

Question 2

What local anesthetic class is responsible for more allergic reactions?

Answer 2

Esters (due to PABA metabolite)

S6

Question 3

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

Answer 3

Methylparaben (broken down into PABA)

Use preservative free

S6

Question 4

Is there a cross-sensitivity between esters and amides?

Answer 4

No

S6

Question 5

How can one be tested for local anesthetic allergy?

Answer 5

Intradermal testing using preservative free LA

S6

Question 6

What are presentations of allergic reactions to local anesthetics?

Answer 6

• Rash
• urticaria
• laryngeal edema w/ or w/o hypotension & bronchospasm

S6

Question 7

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

Answer 7

IgE anaphylaxis

S6

Question 8

What is LAST?

Answer 8

Local Anesthetic Systemic Toxicity

S8

Question 9

What causes LAST syndrome?

Answer 9

Excess plasma concentration of LA from:

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

S8

Question 10

What are other factors that can affect systemic toxicity?

Answer 10

• Patient co-morbidities
• medications
• location & technique of block
• type of LA used & dose

S8

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

S9

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.

S9

Question 13

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

Answer 13

S9

Question 14

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

Answer 14

Hyperkalemia (lowers seizure threshold)

S10

Question 15

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

Answer 15

Drowsiness and facial twitching

S10

Question 16

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

Answer 16

Analgesia

S10

Question 17

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

Answer 17

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

Question 18

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

Answer 18

• Seizures
• Unconsciousness

Question 19

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

Answer 19

• Apnea
• Coma

Question 20

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

Answer 20

Cardiovascular Depression

S11S12

Question 21

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

Answer 21

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

S11

Question 22

What can occur if Bupivacaine is given intravenously?

Answer 22

• Significant ↓BP
• Cardiac Dysrhythmias

Answer 23

Arterial hypoxemia, acidosis, or hypercarbia (in animals

S12

Question 24

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

Answer 24

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

S12

Question 25

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

Answer 25

Pregnancy = ↓ plasma cholinesterases ## Footnote S12

Question 26

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

Answer 26

Bupivacaine > Ropivacaine > Lidocaine ## Footnote S12

Question 27

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

Answer 27

- ↓ plasma esterases - ↓ plasma proteins ## Footnote S12

Question 28

Slide 14

Answer 28

## Footnote S14

Question 29

Slide 15

Question 30

Should a local anesthetic toxicity patient be hyperventilated or hypoventilated?

Answer 30

Hyperventilation = ↓ CO₂ = ↓ acidosis ## Footnote S15

Question 31

Why is 100% O₂ given for LA toxicity?

Answer 31

To inhibit hypoxemia and metabolic acidosis ## Footnote S15

Question 32

What drugs are used to treat LA induced seizures?

Answer 32

* Supplemental oxygen * Benzodiazepine * Propofol * Muscle relaxant * Intralipid: lipid emulsion ## Footnote S16

Question 33

How does Lipid Emulsion rescue work?

Answer 33

**Lipid creates lipid compartment** (encapsulate the local anesthetic and transport it away from cardiac and CNS tissue) ***Also provides fat for myocardial metabolism*.** ## Footnote S17

Question 34

What is the bolus dose of Lipid Emulsion?

Answer 34

1.5 mL/kg of 20% lipid emulsion ## Footnote S17

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 ## Footnote S17

Question 36

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

Answer 36

8 mL/kg ## Footnote ???

Question 37

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

Answer 37

3.8 mL/kg ## Footnote S17

Question 38

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

Answer 38

Cardiopulmonary Bypass ## Footnote S17

Question 39

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

Answer 39

No ## Footnote S17

Question 40

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

Answer 40

Small doses (**10mcg - 100mcg boluses**) are preferred with LAST ACLS. ## Footnote S17

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

Answer 43

56kg so 1.5mLs x 56kg = 84mLs 20% infusion = 200mgs / 1mL 84mLs x 200mgs = **16,800mgs** administered ## Footnote S22

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 ## Footnote S24

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. ## Footnote S25

Question 46

What LA is most often the cause of TNS?

Answer 46

Lidocaine or addition of vasoconstrictor? the patho is still unknown ## Footnote S25

Question 47

What is the treatment for TNS?

Answer 47

- Trigger point injections - NSAIDs | give pain medications!!! ## Footnote S25

Question 48

How long does TNS typically last?

Answer 48

1-7 days ## Footnote S25

Question 49

What is Cauda Equina Syndrome (CES) ?

Answer 49

Diffuse injury @ *lumbosacral plexus* ## Footnote S26

Question 50

What are the s/s of CES?

Answer 50

- Varying degrees of sensory anesthesia - Bowel & bladder dysfunction - Urinary retention ## Footnote S26

Question 51

What conditions are associated with CES?

Answer 51

- Lumbar disc herniation - prolapse or sequestration w/ urinary retention ## Footnote S26

Question 52

What is the cause of Anterior Spinal Artery Syndrome?

Answer 52

- **Thrombosis and/or spasm of the bilateral anterior spinal artery** - **↓BP** - **Vasoconstrictors** - PVD - Spinal cord compression (hematoma/abscess) | most common sydrome ## Footnote S27

Question 53

What are the s/s Anterior Spinal Artery Syndrome?

Answer 53

Lower extremity paresis w/ variable sensory deficit ## Footnote S27

Question 54

What is Methemoglobinemia?

Answer 54

Life-threatening condition where O₂ carrying capacity is decreased due to MetHgb > 15% ## Footnote S28

Question 55

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

Answer 55

- Prilocaine - Benzocaine ## Footnote S28

Question 56

What is the treatment for methemoglobinemia?

Answer 56

Methylene blue 1mg/kg over 5min ## Footnote S28

Question 57

What is the max dosage of methylene blue?

Answer 57

8 mg/kg ## Footnote S28

Question 58

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

Answer 58

20 - 60 min ## Footnote S28

Question 59

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

Answer 59

depresses CO₂ retaining patients (COPD) ## Footnote S29

Question 60

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

Answer 60

Hepatic toxicity *Stopping bupivacaine infusion normalizes LFTs quickly*. ## Footnote S29

Question 61

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 61

C first then A, D, B ## Footnote S30

Question 62

What is Cocaine's MOA?

Answer 62

Blocks presynaptic re-uptake of NE and Dopamine → Increases postsynaptic levels and ↑SNS. ## Footnote S31

Question 63

What are CV adverse effects of Cocaine toxicity?

Answer 63

HTN, tachycardia, coronary vasospasm, MI (infarction & ischemia), ventricular dysrhythmias (including Vfib). ## Footnote S31

Question 64

What does parturient mean?

Answer 64

Woman in labor ## Footnote S31

Question 65

What can cocaine do to a parturient patient?

Answer 65

↓ uterus blood flow = fetal hypoxia ## Footnote S31

Question 66

What can hyperpyrexia lead to?

Answer 66

seizures ## Footnote S31

Question 67

What is the algorithm for cocaine-associated chest pain?

Answer 67

## Footnote S32

Question 68

What drug is best for cocaine toxicity?

Answer 68

Nitroprusside