Lecture 18 (Exam 4) - Local Anesthetics Pt. 3 (Toxicities)

Question 1

Neural Tissue Toxicity a.k.a Neurotoxicity with LA use.

This can either be transient or _______.

List the three neurotox categories LA use can cause.

Answer 1

permanent 😔

1. Transient Neurological Symptoms (TNS)
2. Cauda Equina Syndrome (CES)
3. Anterior Spinal Artery Syndrome

Slide 21

Question 2

Transient Neurological Symptoms (TNS)

How do these symptoms manifest? and within what time frame?

Answer 2

Moderate to severe pain within 6-36 hours post an uneventful single-shot SAB (spinal anesthesia block) in the back, buttocks & posterior thighs…

Slide 22

Question 3

Transient Neurological Symptoms (TNS)

What is the cause(s), aside from your LA?
Which LA is the main culprit?

What is the treatment?

Answer 3

Cause: unknown; could be positioning or vasoconstrictor use. (impedes blood flow)
Most commonly seen with Lidocaine

Treat: trigger point injections and NSAIDs - can last from 1-7 days 🥲

Slide 22

Question 4

Cauda Equina Syndrome (CES)

What are the manifestations?
What are things that could be associated with CES?

Answer 4

This is a diffuse injury in the lumbosacral plexus - you may see bowel and bladder sphincter dysfunction and/or PARAPLEGIA.

Associated with a possible lumbar disc herniation, prolapse or sequestration of the bladder with urinary retention.

Slide 23

Question 5

What are some causes of CES (cauda equina syndrome) post LA?

Answer 5

Causes: unknown but speculated to be from continuous Lidocaine use or the needle (usually 25 gauge)

Seems like there is a lot we don’t know…😅

Slide 23

Question 6

True or False:
Allergic reactions to local anesthetics are rare and occur < 1% of the time.

Answer 6

True
Slide 6

Question 7

What symptoms attributed to excess plasma levels of local anesthetics were mentioned by Dr. Castillo?

Answer 7

Metallic Taste
Ringing Ears
Seizures
Cardiac Arrest
Slide 6

Question 8

What preservative in both esters and amides are related to allergic reactions?

Answer 8

Methylparaben
Slide 6

Question 9

Esters have a higher incidence of allergic reactions due to what component?

Answer 9

PABA
Slide 6

Question 10

True or False:
There is no cross sensitivity between esters and amides

Answer 10

True
Slide 6

Question 11

Anaphylaxis related to local anesthetic administration is mediated by ______

Answer 11

IgE
Slide 6

Question 12

The acronym LAST stands for what?

Answer 12

Local Anesthetic Systemic Toxicity
Slide 7

Question 13

Systemic toxicity is primarily due to excess __________ concentration of the drug.

Answer 13

Plasma
Slide 7

Question 14

Besides direct IV injection, what are other factors that can lead to systemic toxicity?

Answer 14

Patient Co-Morbidities
Medications
Location and technique of block
Local anesthetic used
Dose

Slide 7

Question 15

1. What is the standard of care for treating systemic toxicity of local anesthetics?
2. What is the MOA of the treatment?

Answer 15

1. Intralipid ~ Lipid Emulsion!
2. MOA: creates lipid compartment where it encapsulates the drug! Also, the emulsion provides fat for myocardial metabolism! Yum!

(Slide 16)

Question 16

When doing a lipid rescue, you do a bolus and then an infusion. What are the dosages of the bolus and infusion?

Answer 16

Bolus: 1.5 mL/kg of 20% lipid emulsion (Up to 2 boluses)
Then Infusion: 0.25 mL/kg/minute for at least 10 minutes

1st 30 minutes: 3.8 mL/kg (1.2 to 6 mL/kg) MAX

(Slide 16)

Question 17

1. Why do we want to give epinephrine when doing a lipid rescue?
2. What is the dose?
3. What happens if the patient does not respond to our interventions?

Answer 17

1. We will give epinephrine during a lipid rescue because more than likely they are trying to go see Jesus and you will be running the code.
2. Epinephrine dose: 10 to 100 µg
3. No response: Cardiopulmonary Bypass (CPB)

(Slide 16)

Question 18

If your patient codes because of a LA toxicity, would you ever stop the code?

Answer 18

You keep going until they have received all the lipids and hopefully they recover.

(Slide 17)

Question 19

What are the management recommendations for local anesthetic systemic toxicity provided by the American Society of Regional Anesthesia and Pain Medicine ?

Answer 19

(Slide 18)

Question 20

What is the Local Anesthetic Systemic Toxicity algorithm Castillo wants us to know?

Answer 20

(Slide 19)

Question 21

Answer 21

Question 22

What is the MOA in Cocaine toxicity?

Answer 22

Caused by SNS stimulation by blocking presynaptic uptake of NE and dopamine- which in return increased postsynaptic levels.

(slide 27)

Question 23

What are the adverse effects of Cocaine toxicity and how long can they last?

Answer 23

CV: HTN, tachycardia, coronary vasospasm, MI (infarction & ischemia), ventricular dysrhythmias (including Vfib).
Parturient: decreased UBF (uterine blood flow)- which can lead to fetal hypoxemia
Hyperpyrexia (fever)- can lead to seizures

6 weeks

(slide 27)

Question 24

What are symptoms of anterior spinal artery syndrome?

Answer 24

For whatever reason the anterior spinal artery did not get enough perfusion, which means the spinal cord did not receive enough blood flow and now we got issues.

Issues we might see is lower extremity paresis with a variable sensory deficit.

Paresis = muscle weakness, partial paralysis.
(Slide 24)

Question 25

What are some causes for anterior spinal artery syndrome?

Answer 25

Thrombosis, artery spasm, hypotension, vasoconstrictive drugs, PVD, epidural abscess or hematoma.
(Slide 24)

Question 26

What is methemoglobinemia?

Answer 26

This is a life-threatening condition in which methemoglobin levels are greater than 15%. This causes a decrease in O2 carrying capacity in the blood. (Slide 25)

Question 27

Which local anesthetics are likely to cause methemoglobinemia?

Answer 27

Prilocaine and benzocaine will more likely cause this.

Lidocaine, nitroglycerin, phenytoin, and sulfonamides can also cause methemoglobinemia but not as much as prilocaine or benzocaine could. (Slide 25)

Question 28

What is the treatment for methemoglobinemia? How long will it take for methemoglobin to change back to regular hemoglobin?

Answer 28

Trt: methylene blue 1mg/kg over 5 min, max of 7 - 8 mg/kg. This drug can take 20 - 60 min for it to convert methemoglobin to hemoglobin. (Slide 25)

Question 29

Lidocaine will do what to your ventilatory response to hypoxemia?

Answer 29

Lido will decrease ventilatory response to hypoxemia.

Watch out for those COPDers or CO2 retainers, as they are more affected by this. (Slide 26)

Question 30

Hepatotoxicity can occur with what epidural local anesthetic?

Answer 30

Epidural bupivacaine (gtt or intermittent) can cause hepatoxicity, especially when used for trt of postherpetic neuralgia.

Stop the gtt to get your liver back to normal.
(Slide 26)

Question 31

Name the 3 main goals of Systemic Toxicity Treatment:

Answer 31

1. Prompt airway management
2. Circulatory support
3. Removal of LA from receptor sites

(slide 13)

Question 32

What should you do in the event of CNS toxicity secondary to systemic toxicity of LA’s?

(2 respiratory interventions, 2 meds, and 1 additive med)

Answer 32

100% O2 via NRB or closed circuit
- this inhibits hypoxemia and metabolic acidosis

hyperventilation

barbiturates

Benzodiazepines

Epinephrine as an additive

(slide 14)

Question 33

You start your shift being told that you are responsible for relieving Arthur the hasty CRNA. F**k. You enter the OR and get report from Arthur. Arthur says “don’t know why this hoe is wildin’. I gave her a Wombo block and now she’s seizing. Good luck brah”

The pt is indeed seizing and Arthur vanishes from the OR. What are your 1 intervention and 4 meds that you do?

Answer 33

1. Supplemental O2
2. Benzo (midazolam or diazepam)
3. Propofol (if hemodynamically stable)
4. Muscle relaxant (Succ’s or NDMA)
5. intralipid: lipid emulsion

(slide 15)

Question 34

What kind of side effects do you see with lidocaine at 5mcg/ml?

Answer 34

Circumoral numbness but no CV effects.
Slide 10

Question 35

What cardiac side effects do you expect to see with high plasma concentration of lidocaine?

Answer 35

Slow conduction of cardiac impulse →prolonged PR interval and QRS widening due to cardiac Na channels blockade.
Slide 10
(automaticity is depressed)

Question 36

Accidental IV Bupivacaine could cause:

Answer 36

Precipitous hypotension, AV block, and cardiac dysrhythmias (SVTs, ST- T wave changes, PVCs, widening of QRS, V-tach)

Slide 10
( they can go to asystole)

Question 37

What are predisposing factors for LA systemic toxicity on cardiovascular system effects?

Answer 37

1. Pregnancy → ↓ plasma esterases and ↓ circulating plasma proteins
2. Arterial hypoxemia, acidosis, or hypercarbia (shown in animals)
3. Beta blockers, Digitalis preparations, Ca+ channel blockers → These drugs inhibit myocardial impulse propagation and affect inotropy. This effect is aggravated when LA becomes systemic or toxic.
4. Epinephrine and Phenylephrine –> Epinephrine and phenylephrine may increase bupivacaine cardiotoxicity, reflecting bupivacaine-induced inhibition of catecholamine stimulated production of cAMP. (from the book)
   Slide 11

Question 38

Among Bupivacaine, Ropivacaine, and Lidocaine, which one has the highest cardiovascular system effect and which one has the least?

Answer 38

Bupivacaine > Ropivacaine > Lidocaine
Slide 11

Question 39

What two factors predispose our OB population to local anesthetic toxicity? (select two correct answers)
A. Decrease plasma esterases
B. Decrease plasma proteins
C. Increased plasma esterases
D. Increased plasma proteins

Answer 39

A and B

Question 40

From highest to lowest concentrations, list the routes of local anesthetic administration.

Answer 40

Intravenous
Tracheal
Caudal
Paracervical
Epidural
Brachial
Sciatic
Subcutaneous

Slide 8

Question 41

Magnitude of systemic absorption of LA depends on

Answer 41

Dose
Vascularity of site
Epinephrine use
Physiochemical properties

Slide 8

Question 42

What are the CNS effects/considerations with LA systemic toxicity?

Answer 42

Drowsiness, facial twitch prior to seizure.

Monitor plasma levels with epidural lidocaine > 900mg’s

Hyperkalemia promotes seizures with LA’s (Lower seizure threshold)

Slide 9

Question 43

In the US in 2010 how many people suffered from Cocaine Toxicity?

Answer 43

1.5 Million

(slide 27)