Exam 4 - Local Anesthetics Rescues Flashcards
What is the percentage of lidocaine allergic reactions?
Very Rare, Less than 1%
What is lidocaine allergic reaction attributed to?
Excess plasma levels of lidocaine.
Which class of local anesthetic is more prone to an allergic reaction?
Esters d/t to the PABA metabolite
This preservative in both ester and amide LA can cause an allergic reaction.
Methylparaben
Similar structure to PABA
Is there cross-sensitivity between esters and amides?
No
True LA reactions will exert what symptoms?
- Rash
- Urticaria
- Laryngeal edema w/ or w/o hypotension
- Bronchospasm
- Anaphylaxis attributed to IgE
What does LAST stand for?
What is LAST d/t?
Local Anesthetic Systemic Toxicity
LAST is d/t excess plasma concentration of the drug.
What can cause LAST?
- Entrance of LA to systemic circulation from inactive tissue redistribution and clearance metabolism.
- Accidental direct IV injection
The magnitude of systemic absorption depends on what factors?
- Dose
- Vascularity of site
- Epi use
- Physiochemical properties
Addition of epinephrine can do what to the systemic absorption of LA?
Decrease systemic absorption by 1/3
What are the CNS effects of LAST?
- Drowsiness
- Facial twitch
- Seizures
Plasma venous concentration of lidocaine needs to be monitored when the cumulative epidural dose of lidocaine is greater than ____ mg
900 mgs
Lidocaine at ____ mcg/mL will promote circumoral numbness but no CV effects.
However, high plasma concentrations of LA will block what?
5 mcg/mL
Block cardiac sodium channels
What happens if the cardiac sodium channels are blocked?
Slows conduction of cardiac impulses → prolonged PR interval and QRS widening
What are the effects of accidental IV administration of Bupivacaine?
- Precipitous hypotension
- AV Block
- Cardiac Dysrhythmias
What are predisposing factors to cardiovascular LA Systemic Toxicity?
- Pregnancy (↓plasma esterases)
- Arterial hypoxemia, acidosis, hypercarbia
- β-blockers, Digoxin, CCB (↓ myocardial impulse propagation)
- Epi and phenylephrine (bupivicane inhibits epi production)
What are the top three anesthetics to have LAST CV System Effects?
- Bupivacaine
- Ropivacaine
- Lidocaine
What two factors predispose our OB population to LA toxicity?
A. ↓ Plasma Esterase
B. ↓ Plasma Proteins
C. ↑ Plasma Esterase
D. ↑ Plasma Proteins
A, B
What are the 3 goals for the treatment of LA Systemic Toxicity?
- Prompt airway management
- Circulatory support
- Removal of LA from receptor sites
What are the immediate interventions for LAST?
- 100% O2 in a non-rebreather mask to inhibit hypoxemia and metabolic acidosis.
- Hyperventilation
- Barbiturates/Benzos (prevent LA-induced seizures)
- Epi as an additive (if following ACLS algorithm)
What are treatments for LA-induced seizures?
- Supplemental O2
- Benzo (midazolam, diazepam)
- Propofol: if hemodynamically stable
- Succinylcholine or NMBD
- Intralipid: lipid emulsion
In preparation for anesthetic blocks (epidurals/spinal), what is the standard of care to always have nearby?
Intralipid/ Lipid Emulsions
What is the MOA of Intralipids?
Creates lipid compartment, provides for fat for myocardial metabolism, and encapsulates LA
Intralipid
Bolus Dose:
Infusion Dose:
1st 30 minutes:
Intralipid
Bolus Dose: 1.5 mL/kg of 20% lipid emulsion
Infusion Dose: 0.25/mL/kg/min for at least 10 mins
1st 30 minutes: 10 mL/kg MAX
What are the modified epinephrine doses if cardiac arrest occurs secondary to LAST?
10 to 100 mcg
LAST Treatment: Failure to respond to lipid emulsion and vasopressor therapy should prompt the institution of __________.
Cardiopulmonary Bypass (CPB)
A 60-year-old, 120 lbs female has the following vital signs after the administration of Bupivacaine 0.5% 20 ml through the epidural catheter:
HR: 38 bpm
NIBP: 70/35
RR: 40
SaO2: 92%
How much of the 20% intra-lipid in mg would you bolus?
I. Lbs to Kg
120/2 = 60
10% of 60 = 6
60 - 6 = 54 kg
II. 1.5 mL/kg
1.5 x 54 = 81 mL
III 20% lipid emulsion = 200 mgs
81 x 200 = 16, 200 mg
Neural tissue toxicity secondary from LA complications can be _________ or __________.
Transient; Permanent
What are three categories of Neural Tissue Toxicity from LA?
- Transient Neurological Symptoms (TNS)
- Cauda Equina Syndrome
- Anterior Spinal Artery Syndrome
How do Transient Neurologic Symptoms manifest?
Cause:
Treatment:
Recovery:
Moderate to severe pain in the lower back, butt, and posterior thigh within 6 to 36 hours after an uneventful single-shot subarachnoid block.
Cause: Unknown (but blame lidocaine)
Treatment: Trigger point injections and NSAIDs
Recovery: 1 to 7 days
Describe Cauda Equina Syndrome (CES).
Diffuse injury at lumbosacral plexus → varying degrees of:
* Sensory anesthesia
* Bowel and bladder dysfunction
* Paraplegia
What is Cauda Equina Syndrome associated with?
- Large lumbar disc herniation
- Prolapse or Sequestration with urinary retention
Causes of CES?
- Spinal anesthesia
- High LA concentration
- Compression or ischemia of cauda equina
What is Anterior Artery Spinal Syndrome?
Lower extremity paresis with a variable sensory deficit.
What are the causes of Anterior Artery Spinal Syndrome?
- Thrombosis
- Spasms
- Hypotension
- Vasoconstrictors
- PVD
- Spinal cord compression d/t epidural abscess or hematoma
What is Methemoglobinemia?
Methemoglobinemia can be caused by what LA?
Potentially life-threatening complication d/t ↓ O2 carry capacity (metHb > 15%)
Can be caused by Prilocaine and Benzocaine
What is the treatment for Methemoglobinemia?
How fast can this reversal take place?
Methylene Blue: 1 mg/kg over 5 mins (max 7 to 8 mg/kg)
Fe3+ (Ferric) can be reduced to Fe2+ (Ferrous) within 20 to 60 minutes.
Lidocaine can depress the ventilatory response to arterial hypoxemia. Who are the susceptible patients?
CO2 retainer (COPD)
How can LA cause Hepatotoxicity?
Treatment:
Continuous or intermittent epidural bupivacaine to treat postherpetic neuralgia.
Treatment: Stop infusion → normalize liver transaminase enzyme
What is the most common first intervention when an adverse event is identified?
A. Call for help
B. Administer Antidote
C. Discontinued the causative agent
D. ABC
C
What is the MOA of cocaine?
SNS stimulation blocks presynaptic uptake of NE and Dopamine, leading to ↑ postsynaptic levels.
What are the adverse CV effects of cocaine (can last up to 6 weeks)?
- HTN
- Tachycardia
- Coronary Vasospasm
- MI
- Ventricular Dysrhythmias
What are the adverse parturient effects of cocaine?
↓ Uterine Blood Flow leading to fetal hypoxemia
Cocaine can cause hyperpyrexia (extremely high fever) which can lead to _______.
Seizures
Cocaine-Associated Chest Pain Flow Chart.
Another one to memorize.
Cocaine toxicity treatments?
- Benzos
- NTG
- Avoid BB
