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LAST and Anaphylaxis Overview
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LAST and Anaphylaxis Overview

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Questions and Answers

What are the major symptoms associated with local anesthetic systemic toxicity (LAST)?

  • Dizziness and hyperactivity
  • Nausea and vomiting
  • Abdominal pain and fever
  • Seizures and cardiac arrest (correct)

    • What effect does the addition of vasoconstrictors have on local anesthetics? (select 2)

  • Increases risk of intravascular injection
  • Decreases potency of the anesthetic
  • Prolongs the duration of action and depth of blockade (correct)
  • Decreases systemic absorption by (correct)

    • Which site of administration has the highest rate of systemic absorption for local anesthetics?

  • Epidural site
  • Spinal site
  • Intercostal site (correct)
  • Caudal

    • What factor increases the likelihood of systemic absorption of local anesthetics?

    <p>Larger total dose</p> Signup and view all the answers

    What is the effect of using a local anesthetic with a low pKa?

    <p>Faster onset</p> Signup and view all the answers

    Which of the following patient factors is associated with increased plasma levels of local anesthetics?

    <p>Decreased plasma protein</p> Signup and view all the answers

    What is the primary mechanism by which local anesthetics prevent sensory impulse transmission to the brain?

    <p>Blockade of voltage-gated sodium channels</p> Signup and view all the answers

    What is the purpose of aspirating before injecting local anesthetics?

    <p>To avoid intravascular injection</p> Signup and view all the answers

    What is indicated by an increase in heart rate (+10) and systolic blood pressure (+15) after administering a test dose of a local anesthetic?

    <p>Intravascular injection of vasoconstrictor</p> Signup and view all the answers

    Which of the following is a common additive to local anesthetic solutions used to increase depth and duration?

    <p>Epinephrine</p> Signup and view all the answers

    What should be avoided when injecting local anesthetics with vasoconstrictors? (select 2)

    <p>Injecting into areas without collateral circulation</p> Signup and view all the answers

    Which agent should be avoided in patients at risk for dysrhythmias or systemic hypertension?

    <p>Bupivacaine</p> Signup and view all the answers

    What is the first-line antiarrhythmic treatment for local anesthetic systemic toxicity (LAST)?

    <p>Amiodarone</p> Signup and view all the answers

    In managing anaphylaxis, which of the following is NOT a typical initial management step?

    <p>Administer antihistamines</p> Signup and view all the answers

    What is the maximum recommended dose of lipid emulsion in the treatment of LAST?

    <p>12 mL/kg</p> Signup and view all the answers

    What type of allergic reaction is primarily associated with anaphylaxis?

    <p>Type 1 IgE mediated</p> Signup and view all the answers

    Which pathways activate the complement system?

    <p>Alternative pathway - complement-antigen complex</p> Signup and view all the answers

    Which medication could potentially cause red man syndrome (an anaphylaxis mimic) when administered too rapidly?

    <p>Vancomycin</p> Signup and view all the answers

    What is the purpose of administering a lipid emulsion in cases of LAST?

    <p>To create a binding surface for local anesthetics</p> Signup and view all the answers

    Which agents are considered a common cause of anaphylaxis associated with neuromuscular blocking agents?

    <p>Rocuronium</p> Signup and view all the answers

    What immediate physiological response is mediated by histamine during anaphylaxis?

    <p>Vasodilation</p> Signup and view all the answers

    What is one of the clinical presentations typical of anaphylaxis during surgery?

    <p>Triad of hypotension, tachycardia, and bronchospasm</p> Signup and view all the answers

    Which of the following is NOT commonly associated with increased risk for anaphylaxis in an anesthesia setting?

    <p>History of hypertension</p> Signup and view all the answers

    What are amide local anesthetics metabolized by?

    <p>Liver enzymes</p> Signup and view all the answers

    What are ester local anesthetics metabolized by?

    <p>Plasma butyrylcholinesterase</p> Signup and view all the answers

    Amide LA have 2x"i" in name Ester LA have 1x"i" in name

    <p>True</p> Signup and view all the answers

    Which of the following properties are associated with more toxic local anesthetics? (Select all that apply)

    <p>Lower pKa</p> Signup and view all the answers

    What property of local anesthetics (LA) is associated with increased potency?

    <p>Lipophilicity</p> Signup and view all the answers

    What property of local anesthetics is associated with increased duration of action?

    <p>Increased protein binding - protein acts as a reservoir</p> Signup and view all the answers

    What protein are local anesthetics mostly bound to?

    <p>Alpha-1 acid glycoprotein</p> Signup and view all the answers

    “I Think I Can Push Each Bolus SSlowly For Safety" IV, tracheal, intercostal, caudal, paravertebral, epidural, brachial, spinal, sciatic/femoral, SQ

    <p>True</p> Signup and view all the answers

    What is a characteristic of highly ionized local anesthetics?

    <p>They are less effective in penetrating membranes</p> Signup and view all the answers

    What is the pKa of a drug?

    <p>The pH at which half of the drug is ionized</p> Signup and view all the answers

    Lean body weight is used for dosing local anesthetics

    <p>True</p> Signup and view all the answers

    What effect does decreased plasma protein have on the systemic absorption of local anesthetics?

    <p>Increased plasma levels of local anesthetic</p> Signup and view all the answers

    How does acidosis affect the systemic absorption of local anesthetics?

    <p>It increases systemic absorption due to higher ionization of the LA (weak base) resulting in less absorption in the nerve membrane</p> Signup and view all the answers

    What metabolic conditions result in increased risk of systemic absorption of local anesthetics (LA)?

    <p>Acidosis</p> Signup and view all the answers

    Supplemental oxygen is recommended for peripheral nerve blocks

    <p>True</p> Signup and view all the answers

    Which patients are at an increased risk of LAST (Local Anesthetic Systemic Toxicity) due to increased local anesthetic uptake?

    <p>Both pregnant and uremic patients</p> Signup and view all the answers

    Which patient populations have decreased levels of alpha-1 acid glycoprotein? (Select all that apply)

    <p>Pregnant women</p> Signup and view all the answers

    Which patients have increased sensitivity to the effects of local anesthetics? (select 2)

    <p>Elderly patients</p> Signup and view all the answers

    How should local anesthesia (LA) be administered in terms of dosage and timing between injections?

    <p>In small doses of no more than 5 ml, waiting 30-45 seconds between injections</p> Signup and view all the answers

    In LAST (Local Anesthetic Systemic Toxicity), which symptoms typically appear first?

    <p>Central nervous system (CNS) symptoms</p> Signup and view all the answers

    Which local anesthetic is associated with difficult resuscitation after LAST (Local Anesthetic Systemic Toxicity) cardiac collapse?

    <p>Bupivacaine</p> Signup and view all the answers

    Which of these antiarrhythmics should be avoided in LAST? (Select all that apply)

    <p>Sodium channel blockers</p> Signup and view all the answers

    What type of lipids are used to treat Local Anesthetic Systemic Toxicity (LAST) ?

    <p>20% lipid emulsion</p> Signup and view all the answers

    Lipid emulsion dose for <70 kg 1.5 ml/kg IV bolus then 0.25 ml/kg/min

    <p>True</p> Signup and view all the answers

    Lipid emulsion dose for >70 kg 100 ml IV bolus then 250 ml

    <p>False</p> Signup and view all the answers

    Why does LAST (local anesthetic systemic toxicity) typically present with excitatory symptoms first?

    <p>Blockage of the voltage-gated sodium channels of inhibitory cortical neurons occurs first</p> Signup and view all the answers

    What are early signs of local anesthetic systemic toxicity (LAST)?

    <p>All of the above</p> Signup and view all the answers

    What do local anesthetics preferentially bind to? (select 2)

    <p>Sodium channels in the open state</p> Signup and view all the answers

    What is Exparel?

    <p>A long-acting formulation of bupivacaine that lasts 72 hours</p> Signup and view all the answers

    What is the effect of steroids on local anesthetics?

    <p>Increase duration</p> Signup and view all the answers

    What effect do opioids and alpha-2 agonists have on local anesthetics?

    <p>They synergistically enhance the analgesic effects</p> Signup and view all the answers

    Which local anesthetic adjunct results in a quicker onset?

    <p>Sodium bicarbonate - increases pH so increased number of non-ionized LA to cross membrane</p> Signup and view all the answers

    Which local anesthetics are associated with methemoglobinemia? (Select all that apply)

    <p>Benzocaine</p> Signup and view all the answers

    Study Notes

    Local Anesthetic Systemic Toxicity (LAST)

    • LAST arises from the absorption of local anesthetics (LAs) leading to cardiovascular and neurologic toxicity.
    • Minor symptoms of LAST include tinnitus, periorbital numbness, and a metallic taste.
    • Major symptoms can escalate to seizures and cardiac arrest.
    • Two main classes of LAs:
      • Aminoester: Metabolized by plasma cholinesterase, characterized by an ester link.
      • Aminoamide: Metabolized by hepatic CP450 enzymes, characterized by an amide link.
    • All LAs act as voltage-gated sodium channel blockers, preventing depolarization and sensory impulse transmission to the brain.
    • pKa indicates the ionization level of LAs; lower pKa means higher toxicity due to increased lipophilicity and lower protein binding.
    • LAs mainly bind to alpha-1 glycoprotein; binding decreases in neonates and pregnant individuals.
    • Injection procedures should include aspiration to avoid intravascular injection and administer in small doses (5 mL at a time).

    Factors Affecting Systemic Absorption of LAs

    • Total dose administered; larger doses heighten systemic absorption risk.
    • Injection site vascularity is crucial; more vascular areas like the face allow for greater systemic absorption.
    • Vascularity ranking for systemic absorption: IV > tracheal > intercostal > caudal > paravertebral > epidural > brachial > spinal > sciatic/femoral > SQ.
    • The addition of vasoconstrictors, like epinephrine, can reduce systemic absorption by 20-50% and prolong LA action.
    • Patient factors such as decreased plasma protein, metabolic disturbances, and extremes of age increase systemic absorption risk.
    • LAST has been linked to oral viscous lidocaine and topical applications.

    Prevention and Management of LAST

    • Ensure emergency resuscitation equipment is readily available, including airway management tools and lipid emulsion therapy.
    • Continuous patient monitoring is essential during regional anesthesia.
    • Aspirate before injection, use ideal body weight for dosing, and accommodate patient-specific risk factors.
    • Monitor heart rate (increase of +10) and systolic blood pressure (increase of +15) response to epinephrine or vasoconstrictors post-injection.
    • Maximum allowable doses for various LAs must be known and adhered to.
    • Bupivacaine poses the highest risk for cardiac collapse with challenging resuscitation following toxicity.

    Treatment of LAST

    • Immediate assistance is critical; secure the airway and administer 100% oxygen.
    • Treat seizures with small doses of propofol; muscle relaxants may not prevent seizures.
    • Manage arrhythmias with first-line antiarrhythmic amiodarone, avoiding Na+ channel blockers and certain vasodilators.
    • Lipid emulsion therapy involves administering 1.5 mL/kg and up to 12 mL/kg maximum dosage; mechanisms may include lipid sink and shuttle theories.

    Anaphylaxis in Anesthesia

    • Anaphylactic reactions typically arise in the OR, often from IV drugs within 5 minutes post-administration.
    • The reaction begins localized before spreading systemically; about 60% of reactions are type 1 IgE mediated.
    • Key chemical mediators include histamine (vasodilation) and prostaglandin D2 (bronchoconstriction), leading to severe physiological responses.

    Common Causes and Risk Factors for Anaphylaxis

    • Most common triggers include antibiotics, neuromuscular blocking agents, and chlorhexidine.
    • Penicillin, especially with its beta-lactam group, is notoriously associated with allergic reactions.
    • Neuromuscular blockers like succinylcholine have a history of producing anaphylactic reactions upon second exposure.
    • Risk factors include prior allergic reactions, female sex, mast cell disorders, asthma, and chronic exposure to latex products.

    Management Strategies for Anaphylaxis

    • Immediate cessation of the offending agent and airway management, supplemented with high-flow oxygen.
    • Initiate intravascular volume expansion and administer epinephrine promptly.
    • Secondary treatments encompass antihistamines, corticosteroids, and vasopressin for refractory shock.
    • Continuous monitoring of tryptase levels can help confirm the diagnosis of anaphylaxis within 30 minutes to 1 hour post-reaction.

    Additional Considerations

    • Monitor for bronchospasm; avoid volatile anesthetics as they may worsen myocardial depression.
    • Ensure no needle passes through multi-dose vials with natural rubber stoppers to minimize latex allergy risk.
    • Treat allergic reactions meticulously to prevent severe outcomes, focusing on early recognition and intervention.

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    Description

    This quiz covers the critical aspects of Local Anesthetic Systemic Toxicity (LAST), including its causes, symptoms, and the different classes of local anesthetics. It explores the mechanisms of action of local anesthetics and essential considerations for safe administration. Test your understanding of LAST and its implications for patient safety.

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