Local Anesthetics III (Exam IV) Flashcards
How rare are local anesthetic reactions?
< 1% occurrence
Attributed to manifestations of excess plasma levels
S6
What local anesthetic class is responsible for more allergic reactions?
Esters (due to PABA metabolite)
S6
What preservative commonly used for amide local anesthetics is usually responsible for allergies?
Methylparaben (broken down into PABA)
Use preservative free
S6
Is there a cross-sensitivity between esters and amides?
No
S6
How can one be tested for local anesthetic allergy?
Intradermal testing using preservative free LA
S6
What are presentations of allergic reactions to local anesthetics?
- Rash
- urticaria
- laryngeal edema w/ or w/o hypotension & bronchospasm
S6
What is the most serious complication of allergies to local anesthetics?
IgE anaphylaxis
S6
What is LAST?
Local Anesthetic Systemic Toxicity
S8
What causes LAST syndrome?
Excess plasma concentration of LA from:
- Accidental IV injection
- Systemic absorption from tissue redistribution and clearance metabolism.
S8
What are other factors that can affect systemic toxicity?
- Patient co-morbidities
- medications
- location & technique of block
- type of LA used & dose
S8
What factors affect the magnitude of systemic absorption of local anesthetic?
- Dose
- Vascularity of site
- Concurrent Epi use
- Properties of the drug itself
S9
Would local anesthetic administered via the trachea have a higher or lower chance of systemic absorption than local anesthetic delivered brachially?
Trachea has higher chance of systemic absorption.
S9
Compare and contrast the different areas of local anesthetic administration based on resultant blood concentrations.
S9
What serum electrolyte condition will exacerbate local anesthetic toxicity?
Why?
Hyperkalemia (lowers seizure threshold)
S10
What CNS s/s will forebode local anesthetic induced seizures?
Drowsiness and facial twitching
S10
What s/s would be seen with a plasma lidocaine concentration of 1-5 mcg/ml?
Analgesia
S10
What s/s would be seen with a plasma lidocaine concentration of 5-10 mcg/ml?
- Mouth numbness
- Tinnitus
- Muscle twitching
- ↓BP
- Myocardial depression
What s/s would be seen with a plasma lidocaine concentration of 10-15 mcg/ml?
- Seizures
- Unconsciousness
What s/s would be seen with a plasma lidocaine concentration of 15-25 mcg/ml?
- Apnea
- Coma
What s/s would be seen with a plasma lidocaine concentration of >25 mcg/ml?
Cardiovascular Depression
S11S12
How does lidocaine affect EKGs?
How does it do this?
- Prolongation of PR interval and QRS widening.
- Blockade of Na⁺ channels
S11
What can occur if Bupivacaine is given intravenously?
- Significant ↓BP
- Cardiac Dysrhythmias
Arterial hypoxemia, acidosis, or hypercarbia (in animals
S12
What drugs will predispose patients to cardiovascular effects for LA systemic toxicity?
- β-blockers, CCBs, digoxin
- Epi and Phenylephrine
S12
Why does pregnancy predispose one to cardiovascular toxicity from LA’s?
Pregnancy = ↓ plasma cholinesterases
S12
Which three drugs are most responsible for cardiac adverse effects when reaching toxic levels systemically?
Bupivacaine > Ropivacaine > Lidocaine
S12
Which two factors predispose our OB population to local anesthetic toxicity?
- ↓ plasma esterases
- ↓ plasma proteins
S12
Slide 14
S14
Slide 15
Should a local anesthetic toxicity patient be hyperventilated or hypoventilated?
Hyperventilation = ↓ CO₂ = ↓ acidosis
S15
Why is 100% O₂ given for LA toxicity?
To inhibit hypoxemia and metabolic acidosis
S15
What drugs are used to treat LA induced seizures?
- Supplemental oxygen
- Benzodiazepine
- Propofol
- Muscle relaxant
- Intralipid: lipid emulsion
S16
How does Lipid Emulsion rescue work?
Lipid creates lipid compartment
(encapsulate the local anesthetic and transport it away from cardiac and CNS tissue)
Also provides fat for myocardial metabolism.
S17
What is the bolus dose of Lipid Emulsion?
1.5 mL/kg of 20% lipid emulsion
S17
What is the infusion dose of lipid emulsion?
How long should it be given?
0.25 mL/kg/minute for at least 10 minutes
S17
What is the max dose for lipid emulsion that should be given?
8 mL/kg
???
What is the dose for lipid emulsion that should be given in the 1st 30 minutes?
3.8 mL/kg
S17
What would be the last resort therapy for a patient with severe LAST syndrome in which lipid rescue and ACLS have failed?
Cardiopulmonary Bypass
S17
Can propofol be used as a substitute for a lipid emulsion?
No
S17
If cardiac arrest occurs with LAST syndrome, how should our epinephrine dosing change?
Small doses (10mcg - 100mcg boluses) are preferred with LAST ACLS.
S17
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.
This card is here just to view the LAST algorithm.
56kg so 1.5mLs x 56kg = 84mLs
20% infusion = 200mgs / 1mL
84mLs x 200mgs = 16,800mgs administered
S22
What are the three categories of neural tissue toxicity associated with LA toxicity?
- Transient Neurological Symptoms
- Cauda Equina Syndrome
- Anterior Spinal Artery Syndrome
S24
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 spinal block.
S25
What LA is most often the cause of TNS?
Lidocaine or addition of vasoconstrictor?
the patho is still unknown
S25
What is the treatment for TNS?
- Trigger point injections
- NSAIDs
give pain medications!!!
S25
How long does TNS typically last?
1-7 days
S25
What is Cauda Equina Syndrome (CES) ?
Diffuse injury @ lumbosacral plexus
S26
What are the s/s of CES?
- Varying degrees of sensory anesthesia
- Bowel & bladder dysfunction
- Urinary retention
S26
What conditions are associated with CES?
- Lumbar disc herniation
- prolapse or sequestration w/ urinary retention
S26
What is the cause of Anterior Spinal Artery Syndrome?
- Thrombosis and/or spasm of the bilateral anterior spinal artery
- ↓BP
- Vasoconstrictors
- PVD
- Spinal cord compression (hematoma/abscess)
most common sydrome
S27
What are the s/s Anterior Spinal Artery Syndrome?
Lower extremity paresis w/ variable sensory deficit
S27
What is Methemoglobinemia?
Life-threatening condition where O₂ carrying capacity is decreased due to MetHgb > 15%
S28
Which two LA’s are most often the culprits of methemoglobinemia?
- Prilocaine
- Benzocaine
S28
What is the treatment for methemoglobinemia?
Methylene blue 1mg/kg over 5min
S28
What is the max dosage of methylene blue?
8 mg/kg
S28
How long does the reversal from MetHgb (Fe⁺⁺⁺) to Hgb (Fe⁺⁺) typically take?
20 - 60 min
S28
Lidocaine _________ the ventilatory response to arterial hypoxemia.
What patient population is most susceptible to this?
depresses
CO₂ retaining patients (COPD)
S29
Continuous or intermittent epidural bupivacaine to treat post-herpetic neuralgia can cause what?
Hepatic toxicity
Stopping bupivacaine infusion normalizes LFTs quickly.
S29
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
C first
then A, D, B
S30
What is Cocaine’s MOA?
Blocks presynaptic re-uptake of NE and Dopamine → Increases postsynaptic levels and ↑SNS.
S31
What are CV adverse effects of Cocaine toxicity?
HTN, tachycardia, coronary vasospasm, MI (infarction & ischemia), ventricular dysrhythmias (including Vfib).
S31
What does parturient mean?
Woman in labor
S31
What can cocaine do to a parturient patient?
↓ uterus blood flow = fetal hypoxia
S31
What can hyperpyrexia lead to?
seizures
S31
What is the algorithm for cocaine-associated chest pain?
S32
What drug is best for cocaine toxicity?
Nitroprusside
