Local Anaesthetic Systemic Toxicity Overview

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Questions and Answers

What initial symptoms can be caused by LA blockage in the brain?

Confusion and agitation (correct)

Increased heart rate

Decreased respiratory rate

Enhanced social interaction

What is the consequence of LA preventing oxidative phosphorylation?

Decreased ATP production (correct)

Increased ATP production

Increased O2 utilization

Increased bicarbonate production

What happens to the heart due to ion channel blockages caused by LAs?

Increase in refractory periods

Enhanced myocardial contractility

Normal cardiac function

Conduction defects (correct)

What is a potential result of LAs leading to anaerobic metabolism?

Cell death and organ failure (B) Signup and view all the answers

Which function is primarily affected by the lack of ATP due to LAs?

Systemic vascular resistance (A) Signup and view all the answers

What critical balance does sodium maintain in relation to calcium during the cardiac cycle?

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

How does LA affect the calcium levels in cardiac tissues?

Increases calcium availability (C) Signup and view all the answers

What results from the blockade of sodium channels in relation to potassium and calcium?

Calcium becomes more involved in contraction (C) Signup and view all the answers

What is the main organ system affected by local anaesthetic toxicity?

Heart and central nervous system (D) Signup and view all the answers

Why does the duration of action for bupivacaine present a greater risk of toxicity?

It binds well to plasma, leading to higher concentrations in blood. (A) Signup and view all the answers

What is a primary initial treatment for local anaesthetic systemic toxicity (LAST)?

Discontinue the local anaesthetic if possible (A) Signup and view all the answers

What happens to the level of free drug in the systemic circulation after plasma saturation with local anaesthetic?

It rises rapidly. (C) Signup and view all the answers

What role does lipid emulsion play in treating LAST?

It separates sodium ions from the tissue to reduce toxicity (A) Signup and view all the answers

What is required for the metabolism of local anaesthetics in the body?

Adenosine triphosphate (ATP) (C) Signup and view all the answers

What major problem arises when mitochondrial function is compromised during local anaesthetic toxicity?

Inability to metabolise local anaesthetics (B) Signup and view all the answers

What immediate action is necessary to ensure adequate oxygenation in a patient with LAST?

Provide 100% oxygen and ensure adequate ventilation (A) Signup and view all the answers

What happens to cardiac output during prolonged PR interval due to toxic levels of local anaesthetics?

It decreases significantly without intervention (B) Signup and view all the answers

How does local anaesthetic affect nerve impulses being sent to the brain?

It blocks sodium channels. (B) Signup and view all the answers

What is one of the direct effects of local anaesthetic toxicity on the cardiac system?

Life-threatening seizures (B) Signup and view all the answers

Which of these is a complication of inadequate conduction in the heart due to LAST?

Tachycardia and arrhythmias (D) Signup and view all the answers

Which of the following best describes a consequence of sodium channel inhibition by local anaesthetics?

Bradycardia and hypotension (A) Signup and view all the answers

Which factor does NOT influence the rate of absorption of local anaesthetics into systemic circulation?

The age of the individual (A) Signup and view all the answers

What is indicated if a patient with LAST shows a decline in consciousness level?

Tracheal intubation is indicated (B) Signup and view all the answers

How does lipid emulsion improve cardiac function in LAST?

By providing substrate for energy delivery to the myocardium (D) Signup and view all the answers

What is the main reason why local anesthetics are given?

To relieve pain in a specific area. (C) Signup and view all the answers

What is the chemical characteristic of local anesthetics that allows them to cross cell membranes?

They are lipophilic, meaning they dissolve in fats. (A) Signup and view all the answers

What is the primary mechanism of action for local anesthetics?

Blocking sodium channels, preventing nerve impulses. (A) Signup and view all the answers

What is the main reason for local anesthetic systemic toxicity?

All of these options contribute. (B) Signup and view all the answers

What is the typical timeframe for the development of symptoms after local anesthetic administration?

Within 10 minutes to 1 hour. (C) Signup and view all the answers

Which of the following statements is true regarding local anesthetics and their lipid solubility?

Local anesthetics that are less lipid soluble are easier to remove from the system. (D) Signup and view all the answers

What is the role of sodium in muscle contraction and nerve transmission?

Sodium is involved in the generation of action potentials. (A) Signup and view all the answers

How does local anesthetic systemic toxicity affect the heart?

All of the above. (D) Signup and view all the answers

What primary metabolic disturbance is often observed in burn patients due to abnormal glucose production and insulin resistance?

Hyperglycemia (B) Signup and view all the answers

Which of the following best describes the recommendation for blood analysis in burn patients?

Arterial lines and CVP lines should be considered for blood sampling. (D) Signup and view all the answers

If a burn patient's consciousness level is declining, what should be a primary concern for healthcare providers?

The patient is not receiving adequate oxygen to the brain. (B) Signup and view all the answers

What percentage of the body's total oxygen consumption does the brain require?

20% (A) Signup and view all the answers

During the 'exposure' phase of burn patient assessment, what actions are typically performed?

Full assessment and documentation of the burn injuries (A) Signup and view all the answers

What is the primary goal of burns resuscitation?

To increase tissue perfusion (C) Signup and view all the answers

Which zone of a burn is characterized by increased tissue perfusion?

Zone of hyperaemia (C) Signup and view all the answers

What can cause a zone of stasis to contribute to a deeper wound?

Tissue loss (C) Signup and view all the answers

At what percentage of total body surface area (TBSA) does a burn typically begin to cause a systemic response?

30% (A) Signup and view all the answers

What is the effect of burns on capillary permeability?

Increased permeability (C) Signup and view all the answers

Which of the following is NOT a primary cause of burns?

Infection (C) Signup and view all the answers

Which of the following is a typical systemic cardiovascular response to a significant burn?

Systemic hypotension (D) Signup and view all the answers

What is the result of peripheral and splanchnic vasoconstriction following a significant burn?

Blood pulled from the peripheries to supply main organs (C) Signup and view all the answers

Which layer of the skin is primarily responsible for thermoregulation?

Dermis (B) Signup and view all the answers

What is a possible cause of decreased myocardial contractility, following a significant burn?

Release of tumour necrosis factor α (C) Signup and view all the answers

What is the primary characteristic of a first-degree burn?

Superficial epidermal damage (B) Signup and view all the answers

Which type of burn is characterized by blisters, red skin, and blanching with capillary refill?

Superficial dermal burn (D) Signup and view all the answers

What is a key feature of a third-degree burn?

Painless, black, leathery, waxy skin (A) Signup and view all the answers

Which zone of a burn injury is characterized by tissue damage due to protein coagulation?

Zone of coagulation (D) Signup and view all the answers

What is a main characteristic of the zone of stasis?

Decreased tissue perfusion (B) Signup and view all the answers

Which skin layer is responsible for regenerating the epidermis?

Dermis (C) Signup and view all the answers

What is the primary reason for decreased blood flow to organs following severe burns?

Increased fluid demand at the burn site (A) Signup and view all the answers

How do inflammatory mediators primarily affect the respiratory system in burn patients?

They cause bronchoconstriction and difficulty breathing. (B) Signup and view all the answers

What is the typical change in basal metabolic rate following severe burns?

It increases up to three times its original rate. (A) Signup and view all the answers

Why is early and increased feeding necessary for burn patients?

To decrease the body's catabolism. (C) Signup and view all the answers

What condition develops in burn patients due to increased glucose production and insulin resistance?

Hyperglycemia (D) Signup and view all the answers

Which of the following physiological responses occurs to compensate for reduced stroke volume in burn patients?

Increased heart rate (B) Signup and view all the answers

What is the first step in managing a burn patient?

Determining the location and extent of burns. (A) Signup and view all the answers

What does the absence of blanching during a capillary refill test (CRT) indicate about a burn?

The burn affects the deep dermis. (C) Signup and view all the answers

What is a key indication for considering Rapid Sequence Intubation (RSI) with an endotracheal tube in a burn patient?

Stridor, wheeze, audible sounds and low oxygen saturation levels. (C) Signup and view all the answers

Why might a patient with severe burns around the chest experience dyspnoea?

Inability of the chest wall to expand fully, causing a build of CO2. (B) Signup and view all the answers

Which physiological response does the body initiate to conserve fluid in a patient with severe burns?

Peripheral vasoconstriction. (A) Signup and view all the answers

What is the primary reason for hypothermia in a patient with a third-degree burn?

Loss of the dermis and its homeostatic role for thermoregulation. (B) Signup and view all the answers

The 'lethal triad' in burn patients consists of hypothermia, coagulopathy, and:

Metabolic Acidosis. (B) Signup and view all the answers

What is the primary reason for increased heart rate in burn patients when the blood pressure remains stable?

Loss of stroke volume resulting in increased heart rate to maintain cardiac output. (B) Signup and view all the answers

Why is it critical to control the room temperature for a patient with third-degree burns?

To prevent hypothermia due to loss of the dermis. (A) Signup and view all the answers

What is the significance of 'vascular permeability' in the context of burn injuries?

It causes fluid maldistribution and oedema. (A) Signup and view all the answers

Which of the following rhythm disturbances is considered a 'shockable' cardiac rhythm?

Ventricular Fibrillation (VF) (C) Signup and view all the answers

Which cardiac rhythm is characterized by the absence of electrical activity and requires interventions other than defibrillation?

Asystole (A) Signup and view all the answers

What is the initial step according to the content, when confronted with a patient exhibiting a possible Pulseless Ventricular Tachycardia (PVT) rhythm?

Check the patient's pulse. (A) Signup and view all the answers

Which of the following best describes Pulseless Electrical Activity (PEA)?

Electrical activity seen on the ECG with no palpable pulse. (D) Signup and view all the answers

If a patient's ECG shows Ventricular Fibrillation (VF), what is the MOST appropriate initial intervention?

Attempt defibrillation. (B) Signup and view all the answers

If a patient's blood analysis shows a pH of 7.2 with a reduced bicarbonate level but normal CO2, which condition is most likely present?

Metabolic acidosis (B) Signup and view all the answers

What does a Base Excess (BE) of +3 mmol/L typically indicate about a patient's acid-base balance?

The patient has a metabolic alkalosis. (C) Signup and view all the answers

Why is it crucial to obtain an arterial blood sample promptly after drawing it?

To prevent the sample from metabolizing and clotting. (D) Signup and view all the answers

What is the significance of checking a patient's temperature when interpreting blood gas analysis results?

To determine the metabolic rate affecting PH level. (D) Signup and view all the answers

Elevated levels of which electrolyte would be most concerning in relation to cardiac arrest, as indicated in the text?

Potassium (B) Signup and view all the answers

In arterial blood gas analysis, what does the partial pressure of a gas (Pa) directly indicate?

The concentration of the gas in the blood (D) Signup and view all the answers

When the kidneys fail to produce enough bicarbonate, what specific condition is likely to occur in the patient?

Severe metabolic acidosis (B) Signup and view all the answers

A patient has a PaCO2 level of 7.0 kPa and normal bicarbonate levels. What does this likely indicate?

Respiratory acidosis (C) Signup and view all the answers

If a patient is receiving 50% oxygen, what is the expected PaO2 value, assuming no underlying respiratory issue?

40 kPa (B) Signup and view all the answers

Which of the following best describes the function of bicarbonate (HCO3) in the body?

Buffers excess hydrogen ions leading to a higher pH (B) Signup and view all the answers

What is the primary physiological response of the lungs when attempting to correct acidosis?

Increasing rate and depth of breaths to expel more CO2 (B) Signup and view all the answers

What is the normal range for arterial blood pH, indicating a healthy balance?

7.35 to 7.45 (A) Signup and view all the answers

What is the normal range for bicarbonate (HCO3) in arterial blood gas analysis, indicating optimal kidney function?

22 - 26 mmol (C) Signup and view all the answers

What is the primary metabolic disturbance observed in burn patients due to abnormal glucose production and insulin resistance?

Hyperglycemia (A) Signup and view all the answers

Which of the following is a recommended blood analysis for burn patients?

All of the above (D) Signup and view all the answers

What primarily causes burns?

Heat and radiation (D) Signup and view all the answers

Which layer of the skin is mainly involved in thermoregulation?

Dermis (B) Signup and view all the answers

What characterizes a second-degree superficial burn?

Red and blistered skin with pain (C) Signup and view all the answers

What happens to the tissue in the zone of stasis?

It is characterized by decreased tissue perfusion. (C) Signup and view all the answers

Which type of burn is painless due to nerve damage?

Third-degree burn (A) Signup and view all the answers

What is the primary feature of a first-degree burn?

No damage to dermis (D) Signup and view all the answers

What is the zone of coagulation in burn injuries?

The site of maximum damage (C) Signup and view all the answers

What characterizes a second-degree deep dermal burn?

Dry, mottled skin with no blanching (D) Signup and view all the answers

What causes goosebumps in response to cold temperatures?

Piloerection in dermis (C) Signup and view all the answers

What is the main aim of burns resuscitation?

To increase tissue perfusion and prevent irreversible damage (A) Signup and view all the answers

What is the status of tissue in the zone of hyperaemia?

Tissue recovery is likely unless severe sepsis occurs (D) Signup and view all the answers

What occurs when the zone of stasis is damaged?

The wound will deepen and widen (C) Signup and view all the answers

Which systemic response is triggered once a burn reaches 30% of total body surface area?

Fluid leakage from blood vessels (A) Signup and view all the answers

What happens to myocardial contractility in response to burn injuries?

It decreases due to inflammatory mediators (B) Signup and view all the answers

What effect does prolonged hypotension have on burn injuries?

Can convert zones of stasis into areas of complete tissue loss (C) Signup and view all the answers

What is a consequence of increased capillary permeability following significant burns?

Reduced blood volume within vessels (B) Signup and view all the answers

What is a likely result of vasoconstriction occurring after a significant burn?

Diverting blood to the main organs (B) Signup and view all the answers

What is one of the impacts of the release of cytokines at the burn site?

It has a systemic effect when a burn exceeds 30% TBSA (B) Signup and view all the answers

What can cause a burn wound to deepen and widen?

Infection in the zone of stasis (A) Signup and view all the answers

What is the primary cause of hyperglycemia in burn patients?

Enhanced gluconeogenesis and glycogenolysis (B) Signup and view all the answers

Which metabolic change occurs in burn patients?

Increased metabolic rate by up to three times (A) Signup and view all the answers

What physiological change might occur in a burn patient within the first 24-72 hours?

Hypoperfusion of organs (A) Signup and view all the answers

Which respiratory issue is commonly associated with severe burns?

Bronchoconstriction similar to asthma (C) Signup and view all the answers

What kind of management is crucial if a burn affects the airway areas?

Airway management (D) Signup and view all the answers

What hormone primarily contributes to the metabolic effects seen in burn patients?

Cortisol (D) Signup and view all the answers

What typical response may occur in the cardiovascular system following significant burns?

Systemic hypotension (D) Signup and view all the answers

What is a significant nutritional consideration for burn patients?

Early and increased feeding to maintain gut integrity (C) Signup and view all the answers

What effect does reduced blood flow to the splanchnic region have on burn patients?

Increased resistance to insulin (B) Signup and view all the answers

What type of burn is characterized by pain and blisters, but can blanch with capillary refill?

Second-degree burn (D) Signup and view all the answers

What is a significant consideration when performing rapid sequence intubation (RSI) in an emergency situation?

Employ rapid acting drugs due to potential fasting issues. (C) Signup and view all the answers

What occurs in patients with severe burns that impacts their ability to breathe effectively?

Tight and leathery layers of skin restrict chest expansion. (C) Signup and view all the answers

What is the result of increased vascular permeability in burn patients?

Fluid maldistribution and edema formation. (B) Signup and view all the answers

How does hypothermia occur in burn patients?

Loss of dermal layers impairs thermoregulation. (A) Signup and view all the answers

What physiological response occurs to maintain blood pressure following a significant burn?

Increased heart rate due to loss of stroke volume. (A) Signup and view all the answers

What is the lethal triad associated with severe burns?

Hypothermia, coagulopathy, metabolic acidosis. (A) Signup and view all the answers

How does rapid breathing occur in burn patients experiencing respiratory acidosis?

To expel excess carbon dioxide buildup. (C) Signup and view all the answers

What is a notable clinical sign of third-degree burns?

Leathery black appearance and non-elasticity. (C) Signup and view all the answers

What happens to the patient's body temperature in cases of severe burns despite peripheral vasoconstriction?

Hypothermia is likely due to fluid loss. (B) Signup and view all the answers

What triggers the urge to breathe in patients with impaired respiratory function?

Build-up of carbon dioxide. (A) Signup and view all the answers

Study Notes

Local Anaesthetic Systemic Toxicity (LAST)

LAST is a life-threatening adverse event that can occur after local anesthetic administration via various routes.
Symptoms typically develop within 10 minutes but can occur within an hour.
Local anesthetics are water-soluble salts of lipid-soluble alkaloids. This allows them to dissolve in both water and fat, enabling them to cross cell membranes.
Local anesthetics target voltage-gated sodium channels, blocking sodium channels and impacting signal transmission to the brain.
They also affect cardiac conduction, significantly impacting rapid early depolarization.
Different anesthetics have varying lipid solubility. Those that are more lipid-soluble (like bupivacaine) can cause faster toxicity.
Awareness of the cumulative nature of local anesthetic agents, especially when multiple doses or agents are administered by different members of the perioperative team, is crucial for preventing LAST.
Intravascular injection of anesthetics is a significant risk factor for the development of LAST.
Intravascular markers are recommended if the doses needing administration are potentially toxic.
Intravascular injection of epinephrine is a potentially life-saving measure, increasing systolic blood pressure by at least 15 mmHg.
Proper technique, including incremental administration and aspiration before injection, is essential for reducing the risk of intravascular injection.

Systemic Toxicity Mechanism

Local anesthetics are absorbed into the systemic circulation.
Absorption rate depends on the administered dose and the vascularity of the surrounding tissue.
Local anesthetics bind to plasma.
Saturation leads to increased free drug concentration in the systemic circulation.
This can trigger organ-specific toxicity, primarily to organs highly perfused with blood, like the brain and heart.
Brain toxicity manifests as initial excitation (nervousness, confusion, etc.), followed by CNS depression and potentially seizures and respiratory arrest.
Cardiac toxicity includes ion channel blockade, oxidative phosphorylation inhibition (leading to a lower ATP production), and potential arrhythmias and cardiac arrest.
Local anesthetics may also cause hypotension, and/or cardiac arrest, and dysrhythmias.
The rate of absorption depends on the amount of anesthetic administered and the vascularity of the structures around the area.
Different local anesthetics bind to plasma differently, with some (e.g., bupivacaine) having a high percentage of plasma binding, leading to longer durations of action and higher toxicity risk.
When plasma is saturated, free drug levels in the systemic circulation rise rapidly, leading to rapid toxicity.

Treatment for LAST

First priority is discontinuation of the local anesthetic.
Emergency measures include:
- High-flow oxygen administration to prevent hypoxia and maintain adequate ventilation.
- Establishing intravenous access for rapid treatment with lipid emulsion (20% Intralipid). This is a critical component to remove the free local anesthetic from tissues and into lipids, effectively removing them from the system.
- Intubation and mechanical ventilation if necessary (to correct pH imbalances).
- In cases of circulatory arrest, CPR is the immediate action.
Administering lipid emulsion (20% Intralipid) is critical for removing free local anesthetic from the tissues and into the lipids, ultimately removing them from the body.
Use of appropriate medications (like benzodiazepines) to manage seizures, hypotension, or arrhythmias. Use appropriate doses.
Monitoring of vital signs, including blood pressure, cardiac rhythm, and oxygen saturation, is required throughout treatment and recovery.
If no circulatory arrest, treat hypotension and arrhythmias with benzodiazepines, avoiding high doses of adrenaline for patients with circulatory arrest.

Prevention of LAST

Using ultrasound guidance during infiltration of local anesthetics to ensure accurate injection placement, thus limiting intravascular administration.
Calculate and administer appropriate doses based on the lowest effective dose.
Incremental administration of doses (e.g., 3-5 mL aliquots, pausing after each administration) to help prevent rapid absorption to reduce systemic absorption.
Gentle aspiration and check for intravascular leakage before injection.
Awareness of cumulative nature of local anesthetic agents, and administering doses by different members of the surgical team, is crucial to prevent LAST
intravascular markers are recommended when the doses requiring administration are potentially toxic.
Intravascular injection of epinephrine is a potentially life-saving measure, increasing systolic blood pressure by at least 15 mmHg.
Awareness of the cumulative nature of local anesthetic administration. Specific consideration to the duration of action of individual local anesthetics is also crucial.

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Description

This quiz delves into Local Anaesthetic Systemic Toxicity (LAST), a critical condition arising from local anesthetic administration. Learn about symptoms, mechanisms, and the role of lipid solubility in toxicity. Test your knowledge of the factors influencing LAST and its cardiac implications.