Local Anaesthetic Systemic Toxicity Overview

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Questions and Answers

Local anaesthetic systemic toxicity is a life-threatening adverse event that typically occurs within what timeframe after administration?

Within 30 minutes

After a few hours

Within the first 10 minutes but possibly up to an hour (correct)

Immediately upon administration

What is the primary characteristic of local anaesthetic drugs regarding their solubility?

Water-soluble salts of lipid-soluble alkaloids (correct)

Exclusively lipid-soluble

Exclusively water-soluble

Insoluble in both water and lipids

How do local anaesthetics primarily inhibit pain signals in the body?

By increasing muscle contraction

By enhancing potassium channel activity

By stimulating nerve cell transmission

By blocking sodium channels (correct)

Why does the lipid solubility of a local anaesthetic affect its removal and toxicity?

Higher lipid solubility facilitates easier removal but can also lead to faster toxicity (B) Signup and view all the answers

Besides the nervous system, which other major organ system is significantly affected by local anaesthetic toxicity due to sodium channel interference?

The heart (A) Signup and view all the answers

What role does sodium play in the body that is relevant to local anaesthetic toxicity?

It carries an electrical charge, facilitating muscle contraction and nerve cell transmission (A) Signup and view all the answers

How does local anaesthetic systemic toxicity progress from mild to severe?

From progressive inhibition to life-threatening seizures and cardiac arrest (C) Signup and view all the answers

At what level do local anaesthetics cause systemic toxicity in the body?

When the concentration affects organs dependent on sodium channel conduction (A) Signup and view all the answers

What primarily determines the rate of absorption of a local anesthetic into systemic circulation after perineural administration?

The volume of anesthetic administered and the vascularity of the surrounding tissues. (A) Signup and view all the answers

Why does bupivacaine have a longer duration of action compared to some other local anesthetics?

It has a high percentage of binding to plasma. (D) Signup and view all the answers

What is the primary risk associated with a local anesthetic that binds very well to plasma?

A rapid rise in free drug concentration in systemic circulation leading to severe toxicity. (D) Signup and view all the answers

Which of the following body systems are MOST likely to be severely affected by local anaesthetic toxicity due to perfusion?

Heart, brain and liver. (A) Signup and view all the answers

Why can impaired plasma enzyme function lead to increased local anaesthetic toxicity?

It slows down the metabolism of the local anesthetic. (B) Signup and view all the answers

What is the underlying mechanism of LAST when considered from a metabolic point of view?

Inability of the mitochondria to generate sufficient ATP. (B) Signup and view all the answers

How do local anaesthetics interfere with nerve impulses in the brain?

By blocking sodium channels in the nerve cell plasma membrane. (B) Signup and view all the answers

What is one of the primary ways local anesthetics (LAs) affect cardiac tissue at a biochemical level?

Blocking ion channels (A) Signup and view all the answers

What process in the mitochondria is inhibited by local anesthetics?

Oxidative phosphorylation (A) Signup and view all the answers

What is often the initial symptom of CNS toxicity caused by local anaesthetics?

An initial excitation of the nervous system, such as nervousness and agitation. (B) Signup and view all the answers

Inhibition of ATP production due to local anesthetics can directly cause?

Reduced myocardial contractility (B) Signup and view all the answers

What effect do local anesthetics have on the refractory period of cardiac tissue?

Shortened refractory period (A) Signup and view all the answers

What is the role of sodium channels in relation to calcium in the cardiac cycle, according to the text?

Sodium balances calcium levels (B) Signup and view all the answers

What is a common initial cardiovascular sign associated with local anesthetic toxicity?

Hypotension (B) Signup and view all the answers

How does the accumulation of hydrogen ions (H+) occur due to local anesthetic toxicity, according to the text?

Due to a lack of energy to move them out (C) Signup and view all the answers

What is often the progression of cardiovascular issues related to local anesthetic toxicity?

Hypotension, tachycardia, arrhythmia to bradycardia and cardiac arrest (B) Signup and view all the answers

What is the primary purpose of using ultrasound guidance when administering a peripheral nerve block?

To improve the precision of needle placement during the procedure (B) Signup and view all the answers

Why is it recommended to administer local anaesthetic agents in small aliquots?

To allow for immediate detection of intravascular injection. (D) Signup and view all the answers

During local anesthetic administration, what does aspiration immediately prior to injection aim to verify?

The absence of blood vessel entry (C) Signup and view all the answers

What does the term 'cumulative nature' refer to, in the context of local anaesthetic agents?

The increasing risk of toxicity as successive doses are given. (A) Signup and view all the answers

In the treatment of local anesthetic systemic toxicity (LAST), what is the primary reason for administering 100% oxygen?

To help prevent hypoxia and ensuing organ damage. (C) Signup and view all the answers

What is the immediate action clinicians should undertake for management of LAST?

Discontinue Local anaesthetic administration, and call for help (D) Signup and view all the answers

What is the role of lipid emulsion (e.g., Intralipid) in treating local anesthetic systemic toxicity (LAST)?

To scavenge free local anaesthetic agents from tissues. (A) Signup and view all the answers

What is the recommended initial bolus of 20% Intralipid/lipid emulsion in the treatment of LAST?

1mL/kg (D) Signup and view all the answers

Study Notes

Local Anaesthetic Systemic Toxicity (LAST)

LAST is a life-threatening adverse event occurring after local anesthetic administration.
Symptoms typically present within 10 minutes to an hour.

Causes of Local Anaesthetics

Local anesthetics are water-soluble salts of lipid-soluble alkaloids.
They dissolve in both water and fats (lipophilic).
This allows them to easily cross cell membranes.
Different local anesthetics have varying lipid solubility, affecting toxicity potential.

Mechanism of Action

Local anesthetics target voltage-gated sodium channels.
Blocking these channels disrupts nerve impulse transmission.
This prevents pain signals from reaching the brain.
Importantly, sodium channels are also crucial for cardiac function.
Anesthetic blockage can disrupt normal heart function.

Systemic Toxicity

When local anesthetics are absorbed into the bloodstream, they reach the brain and other organs.
High concentrations can lead to toxic effects.
Local anesthetics bind to plasma proteins, altering their availability for function.
Some tissues have higher blood flow (brain, heart). These tissues are affected more rapidly.

Treatment

Discontinue the local anesthetic.
Request a lipid rescue pack (emergency treatment).
Administer 100% oxygen.
Ensure adequate ventilation.
Establish an intravenous (IV) line.
Administer 20% Intralipid.
Treat hypotension and/or arrhythmias.
For seizures, consider benzodiazepines.
If circulatory arrest, initiate CPR, but avoid high doses of epinephrine at this stage.

Prevention

Utilize ultrasound guidance for precise injections.
Administer the lowest effective dose.
Aspirate before injection.
Administer medications incrementally.
Use intravascular markers to monitor drug levels.
Adjust doses for children and adults.

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Description

This quiz covers the essential aspects of Local Anaesthetic Systemic Toxicity (LAST), including its causes, mechanism of action, and systemic effects. Understanding LAST is crucial for medical professionals and those studying anesthesiology to prevent life-threatening situations associated with local anaesthetics.