SS25 Local Anesthetics III (Exam 4) Flashcards
1
Q
LA routes of administration:
A
- Peripheral Nerve Blocks
- Neuroaxial: Spinal/Epidural
- Local/Regional
We are NOT talking about IV Lido induction
2
Q
How rare are local anesthetic reactions?
- Range of severity?
A
- < 1% occurrence
- Mild to IgE Anaphylaxis
3
Q
LA drug classes? (2)
A
- Esters
- Amides
4
Q
What local anesthetic class is responsible for more allergic reactions?
- Why?
A
- Esters
- due to PABA preservative
PABA: para-aminobenzoic acid
5
Q
What other preservative is used for both esters & amides?
- Can it cause allergic responses?
A
- Methylparaben
- Yes, similar structure to PABA
6
Q
Is there a cross-sensitivity between esters and amides?
A
No
- So, if they’re allergic to PABA, that does not mean they are automatiicaly allergic to Methylparaben.
7
Q
T/F: LA do not have a perservative free formula?
A
False; if concern for severe allergy risk, use preservative free LA
8
Q
Clinical manifestations of LA Allergic reaction:
A
- rash
- urticaria
- laryngeal edema w/ or w/o hypotension & bronchospasm
9
Q
How can one be tested for local anesthetic allergy?
A
Skin (Intradermal) testing using preservative free LA
10
Q
What is the most serious complication of allergies to local anesthetics?
A
IgE anaphylaxis
11
Q
Management of LA Allergic reaction:
A
- Stop administration
- Supporttive care: Airway, O2,fluids
- Epinephrine, Antihistamine (Benadryl + Decadron), Cortiocosteroid (sol-Medrol), Vasopressin
- Allergy testing: Skin test with preservative-free LA
Dilute Epi or Vaso, Benadryl 50 mg, Decadrom 4,8, or 12 mg
12
Q
What is LAST?
- What does the abbreviation stand for?
A
Local Anesthetic Systemic Toxicity
- Excess plasma concentration of the LA in systemic circulation
13
Q
What causes LAST syndrome?
A
- Accidental direct IV injection
- Entrance into systemic circulation from inactive tissue redistribution and clearance metabolism
- Co-morbidities
- Coughing (increases cephalad movement)
- Medications
- LA used, dose, location, & block technique
14
Q
What factors affect the magnitude of systemic absorption of local anesthetic?
A
- Dose
- Vascularity of site
- Concurrent Epi use
- Physiochemical properties
15
Q
Would LA administered via the trachea have a higher or lower chance of systemic absorption than LA delivered brachially?
A
Trachea has higher chance of systemic absorption.
16
Q
Place the blood concentrations of LA in order from high to low based off region.
A
- IV
- Tracheal
- Caudal
- Paracervical
- Epidural
- Brachial
- Sciatic
- Subcutaneous
17
Q
What electrolyte imbalance will exacerbate local anesthetic toxicity?
- How?
A
- Hyperkalemia
- Lowers seizure threshold by facilitating depolarization
18
Q
What is an early sign of LAST?
- Dose range that this can occur? (include units)
A
- Early agitation
- 1 - 10 mcg/ml
19
Q
What effect would be seen with a plasma lidocaine concentration of 1-5 mcg/ml?
A
Analgesia
20
Q
What effect(s) would be seen with a plasma lidocaine concentration of 5-10 mcg/ml?
A
- Circumoral numbness
- Tinnitus
- Skeletal Muscle twitching
- Systemic hypotension
- Myocardial depression
21
Q
What effect(s) would be seen with a plasma lidocaine concentration of 10-15 mcg/ml?
A
- Seizures
- Unconsciousness
22
Q
What CNS s/s will occur prior to LA-induced seizures?
A
- Drowsiness and facial twitching
23
Q
What effect(s) would be seen with a plasma lidocaine concentration of 15-25 mcg/ml?
A
- Apnea
- Coma
24
Q
What effect(s) would be seen with a plasma lidocaine concentration of >25 mcg/ml?
A
Cardiovascular Depression
25
At what level is it recommended to monitor plasma lidocaine concentration?
- When the accumlative epidural dose of Lido > 900 mg
26
The accumulation of ______________ decreases the seizure threshold of Lidocaine and prolongs sz duration.
Serotonin
27
Risk factors for LAST CV system effects.
- Pregnancy
- Hepatic & Liver dx
- Arterial hypoxia, Acidosis, Hypercarbia (in animals)
- BBlockers, Digitalis preps, CaC Blockers
- Epi & Phenylephrine use
28
What effects does high plasma Lidocaine levels have on the conduction system?
- What EKG changes do you expect to see?
- What dose can this occur cardiac collapse occur?
- Conduction delays
- **Blockade of Na⁺ channels**
- **Prolonged PR interval & wide QRS**; Negative inotropy
- **@ 5 mcg/mL with severe hypotension**
29
What can occur if you accidently inject Bupivacaine intravenously?
- Significant ↓BP
- EKG changes: ST-T wave changes, wide QRS, PVCs
- Cardiac dysrhythmias: SVT, AV block, VTach, Cardiac arrest
30
What drugs and drug classes will predispose patients to cardiovascular effects for LA systemic toxicity (LAST)?
- β-blockers, CCBs, digoxin
- Epi and Phenylephrine
31
Which two factors predispose our OB population to local anesthetic toxicity?
- ↓ plasma esterases
- ↓ plasma proteins
32
Which LA is safest for expecting mother? Bupivacaine or Ropivacaine.
- Why?
- Ropivacaine
- Increased cardiotoxicity seen in pregos with Bupivacaine use
33
Which three drugs are most responsible for **cardiac adverse effects** when reaching toxic levels systemically?
**Bupivacaine > Ropivacaine > Lidocaine**
34
Goals for LAST treatment:
1. STAT Airway management
2. Circulatory support
3. Removal of LA from receptor sites
35
LAST Treatment includes:
1. STOP LA
2. Call for help
3. 100% O₂
4. Hyperventilation
5. Sedation if stable (Barbs or Prop)
6. Epinephrine (cautious)
36
Explain the efficacy of Epinephrine with LAST.
- Epinephrine may not work if block is at receptor level
- Ex: **Bupivacaine may limit effectiveness of Epinephrine during resuscitative measures**
- Have to dissaccociate the LA binding at Na channel
37
How does hyperventilation therapy help LAST?
- Hyperventilation = ↓ CO₂ = ↓ acidosis
38
Why is 100% O₂ given for LA toxicity?
To inhibit hypoxemia and metabolic acidosis
39
LAST seizure control treatment includes:
- Supplemental O₂
- Benzodiazepines (Midazolam or Diazepam)
- Propofol (if stable)
- **Muscle relaxants** (Succs or other NMBA)
- **Intralipid: Lipid emulsion Rescue**
40
What is the standard of care for LAST?
- MOA?
- Intralipids (aka Rescue lipis; Lipid Emulsion)
- MOA: **Creates lipid compartement and provides fat for myocardial metabolism**
41
What is the **bolus** dose of Lipid Emulsion?
**1.5 mL/kg of 20% lipid emulsion**
42
What is the **infusion** dose of lipid emulsion?
How long should it be given?
**0.25 mL/kg/minute** for at least 10 minutes
43
What is the max dose for lipid emulsion that **should be given over the 1st 30 minutes**?
**10 mL/kg**
## Footnote
**Standard dose given to patients (regardless of weight per Dr. Castillo) Typically dose for patients that are 70 kg or more**
44
Can propofol be used as a substitute for a lipid emulsion?
No
45
Epinephrine dose for cardiac arrest with LAST?
- **Smaller doses**
- **10mcg - 100mcg boluses** are preferred with LAST ACLS.
46
How much vasopressin should be given if a patient is suffering from hypotension from LAST syndrome?
Trick question. Vasopression should **not** be given with LAST syndrome.
47
What would be the last resort therapy for a patient with severe LAST syndrome in which lipid rescue and ACLS have failed?
Cardiopulmonary Bypass
48
**This card is here just to view the LAST algorithm**.
49
1. Convert 120 lbs to kg = 54.5 kg
2. Multiply by bolus dose: 54.5 kg x 1.5 mL = 81.75 mL
3. Convert lipid concentration: 20% = 200 mg / 1 mL
4. 81.75ml x 200 mg = 16,350 mg
## Footnote
Dr. Castillo's math didn't round
50
What is Neural Tissue Toxicity?
- Main Cause?
- Direct neurotoxic effects on neurons that can lead to transient or permant neurological injury
51
What can cause Neural Tissue Toxicity?
- High concentrations and/or prolonged exposure
- LA directly injected into nerve = bad
## Footnote
LA should soak nerve not be directly injected; important ot dilute LA to prevent this
52
What are the three categories of neural tissue toxicity associated with LA toxicity?
1. Transient Neurological Symptoms (TNS)
2. Cauda Equina Syndrome
3. Anterior Spinal Artery Syndrome
53
What are the s/s of Transient Neurological Symptoms (TNS) ?
- Moderate to severe pain in the lower back, buttocks, or posterior thighs within 6 - 36 hours post uneventful single-shot subarachnoid block (SAB)
54
What causes of TNS?
- Cause is unknown
-Theories: Positioning, vasoconstrictors, the LA itself
55
What LA seems to have more incidences of TNS?
- Lidocaine > other LAs
56
What is the treatment for TNS?
- Trigger point injections
- NSAIDs
57
How long does TNS typically last?
1-7 days
58
What is Cauda Equina Syndrome (CES) ?
- Causes?
- **Diffuse injury @ lumbosacral plexus**
- Possibly spinal anesthesia, high concentrations, compression or ischemia of cauda equina
59
What are the s/s of CES?
- Varying degrees of sensory anesthesia
- Bowel & bladder sphincter dysfunction
- Weakness or paraplegia
60
What conditions are associated with CES?
- Lumbar disc herniation, prolapse or sequestration w/ urinary retention
61
What is the cause of Anterior Spinal Artery Syndrome?
- **Thrombosis or vasospasm** of the bilat. anterior spinal artery
- **Hypotension**
- **Vasoconstrictors**
- PVD
- Spinal cord compression d/t epidural hematoma / abscess
62
What are the s/s Anterior Spinal Artery Syndrome?
- Lower extremity paresis w/ variable sensory deficit
- No pain below infarct
- Absent temperature
- Proprioception & motor intact
63
Management of Anterior Spinal Artery Syndrome:
1. Dilute LA / use lower concentration
2. Caution with diabetics d/t neuro complications
3. Neuro consult
4. Consider imaging/ labs
64
What is Methemoglobinemia?
- Life-threatening complication d/t decreased O₂ carrying capacity
- **MetHgb > 15%**
65
Which 3 LAs are common causes of methemoglobinemia?
- place in order from high to low
1. Prilocaine
2. Benzocaine
3. Lidocaine
66
What other drugs can cause methemoglobinemia?
- NTG
- Phenytoin
- Sulfonamides
67
What is the treatment for methemoglobinemia?
- Include therapeutic dose
- **Methylene blue 1mg/kg over 5 mins**
68
What is the max dosage of Methylene blue?
- **Max: 7 - 8 mg/kg**
69
How long does the reversal from MetHgb (Fe³+) to Hgb (Fe²+) typically take?
- **20 - 60 mins**
70
Lidocaine _________ the ventilatory response to arterial hypoxemia.
What patient population is most susceptible to this?
- Depresses
- CO₂ retainers (COPD)
71
Continuous or intermittent epidural bupivacaine to treat post-herpetic neuralgia can cause what?
- Hepatotoxicity
*Stopping bupivacaine infusion normalizes LFTs quickly*.
72
Management for Hepatotoxicity includes:
- Stop infusion STAT
- Normalize liver transaminase enzymes
73
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. Call for help
then D, C, and B last
74
What is MOA with Cocaine Toxicity?
- SNS stimulation by blocking presynaptic uptake of NE and Dopamine → Increases postsynaptic levels and ↑SNS.
75
What are the adverse effects of Cocaine Toxicity?
- CV: HTN, Tachy, coronary vasospams, MIs, ventricular dysrhythmias (like Vfib)
- **Parturient: decreased Urine blood flow (UBF) = fetal hypoxemia**
- Hyperpyrexia: Seizures
76
What is the first intervention with AE with Cocaine is indentified?
- Stop / discontinue agent
77
Other treatment modalities are available for Cocaine Toxicity?
- Benzos, NTG
- AVOID BBlockers
78
What does parturient mean?
Woman in labor
79
What can cocaine do to a parturient patient?
↓ uterus blood flow = fetal hypoxia
80
What is the algorithm for cocaine-associated chest pain?
81
What drug is best for cocaine toxicity?
Nitroprusside
