Local Anesthetics Practice Questions

Q: An 18 years old woman in the active stage of labour requests an epidural anaesthesia for delivery. Immediately following the epidural injection of 12ml of 2% lidocaine, the patient complains of lip numbness and becomes apprehensive. What is the presumptive diagnosis?

Systemic toxicity to drug administered. ***Systemic toxicity to drug administered*** - **Lip numbness** and apprehension immediately following epidural lidocaine injection are classic signs of **local anesthetic systemic toxicity (LAST)** due to unintended intravascular injection. - The rapid onset of symptoms suggests direct access to the systemic circulation via a blood vessel, leading to high plasma concentrations of lidocaine. *Allergy to drug administered* - Allergic reactions to local anesthetics are rare and typically involve **urticaria**, **bronchospasm**, or **anaphylaxis**, which are not described here. - Symptoms of allergy usually do not include lip numbness and apprehension as the primary manifestations. *Vasovagal shock* - Vasovagal reactions are characterized by **bradycardia**, **hypotension**, and syncope, usually triggered by pain or anxiety. - While apprehension is present, the specific symptom of lip numbness is not typical of a vasovagal response. *Drug entered SA space* - If the drug had entered the subarachnoid (SA) space, the patient would likely experience a **rapid onset of profound motor and sensory block**, potentially leading to **total spinal anesthesia** and respiratory compromise. - Lip numbness and apprehension are not primary indicators of inadvertent subarachnoid injection; rather, they point to systemic absorption.

Q: Which of the following is commonly used as an epidural anesthetic agent?

All of the options. ***All of the options*** - **Bupivacaine**, **chloroprocaine**, and **lidocaine** are all commonly used as epidural anesthetic agents due to their differing onset times, durations of action, and potencies, allowing for tailored anesthetic approaches. - The choice among these agents depends on the surgical procedure, desired duration of action, and patient-specific factors. *Bupivacaine* - **Bupivacaine** is a long-acting amide local anesthetic, frequently chosen for epidural anesthesia when a prolonged duration of action is required, such as in labor analgesia or postoperative pain management. - It is more potent than lidocaine and has a **slower onset** but offers a longer duration of sensory and motor block. *Chloroprocaine* - **Chloroprocaine** is an ester-type local anesthetic known for its very **rapid onset** and short duration of action, primarily used when a quick onset and short-lived block are desired, such as for emergency C-sections or rapid surgical procedures. - It is rapidly metabolized by plasma pseudocholinesterase, leading to a quick offset and lower systemic toxicity compared to amide local anesthetics. *Lidocaine* - **Lidocaine** is an intermediate-acting amide local anesthetic, commonly used for epidural anesthesia when a moderate duration of action is needed, suitable for various surgical procedures. - It offers a **rapid onset** of action and a good balance between motor and sensory block, making it versatile for different clinical scenarios.

Q: Anesthetic agent with vasoconstrictor is contraindicated in

Digital block. ***Digital block*** - **Vasoconstrictors** in local anesthetics can cause severe **vasoconstriction** in tissues with limited collateral circulation, like digits. - This can lead to **ischemia**, **necrosis**, and even **gangrene** of the affected digit, making it a contraindication. *Spinal block* - **Vasoconstrictors** are sometimes added to local anesthetics for spinal blocks to prolong the duration of action and reduce systemic absorption. - While careful monitoring is needed, it is not an absolute contraindication and can be used cautiously. *Regional anesthesia* - In many forms of **regional anesthesia** (e.g., peripheral nerve blocks), vasoconstrictors like epinephrine are commonly added to prolong the block and reduce systemic toxicity. - This is a standard practice and generally safe outside of specific areas like digits. *Epidural block* - Similar to spinal blocks, **vasoconstrictors** are frequently used in **epidural anesthesia** to improve the quality, duration, and reduce systemic absorption of the local anesthetic. - While dose and patient factors must be considered, it is not a contraindication.

Q: The site of action of local anaesthetic in epidural anesthesia is

Spinal nerve root. ***Spinal nerve root*** - Local anesthetics injected into the epidural space primarily act on the **spinal nerve roots** as they exit the spinal cord. - They also affect the **dorsal root ganglia** and the unmyelinated axons within the epidural space. *Anterior root of spinal nerve* - While the **anterior roots containing motor fibers** are affected, the local anesthetic's action isn't limited exclusively to them. - Sensory fibers in the **dorsal roots** are also blocked, contributing significantly to the analgesic effect. *Epidural neural tissue* - "Epidural neural tissue" is a too broad and non-specific term; the primary targets are the **nerve roots** themselves, not just any neural tissue within the epidural space. - This option does not specify which neural structures within the epidural space are the primary site of action. *Spinal cord* - Local anesthetics do not directly act on the **spinal cord parenchyma** in epidural anesthesia, as they do not typically penetrate the meninges to reach the cord in significant concentrations. - The medication exerts its effect outside the dura mater, primarily on the **nerve roots** before they enter the subarachnoid space.

Q: In spinal anesthesia, which local anesthetic has the longest duration of action?

Bupivacaine. ***Bupivacaine*** - **Bupivacaine** is an amide-type local anesthetic known for its **long duration of action** in spinal anesthesia due to its high lipid solubility and protein binding. - Its prolonged effect is particularly useful for surgical procedures requiring extended periods of **analgesia** and motor blockade. *Procaine* - **Procaine** is an ester-type local anesthetic with a **short duration of action** due to rapid hydrolysis by plasma pseudocholinesterase. - It is rarely used for spinal anesthesia today due to its brief effect and potential for **allergic reactions**. *Tetracaine* - **Tetracaine** is an ester local anesthetic that has a relatively **long duration of action** compared to procaine, but generally shorter than bupivacaine. - While it provides good spinal anesthesia, its use has decreased in favor of amide anesthetics like bupivacaine due to similar but often preferred profiles of efficacy and safety. *Lidocaine* - **Lidocaine** is an amide-type local anesthetic with an **intermediate duration of action** in spinal anesthesia. - It is frequently used for surgical procedures of moderate duration, but its effect is significantly shorter than that of bupivacaine.

Q: What is the concentration of adrenaline typically used with local anesthetics?

1:200,000. ***1:200,000*** - This concentration of **adrenaline** (epinephrine) is commonly used with local anesthetics to prolong their duration of action and reduce systemic absorption. - It provides a good balance between efficacy in vasoconstriction and minimizing potential systemic side effects. *1:100,000* - While also used, this concentration provides a higher dose of **adrenaline**, which is often reserved for situations requiring more profound vasoconstriction or when a longer duration of action is critical. - It carries a slightly higher risk of systemic **epinephrine** effects compared to 1:200,000. *1:10,000* - This is a very high concentration of **adrenaline**, typically used for resuscitation in medical emergencies like **cardiac arrest** or **anaphylaxis**, not as an additive to local anesthetics for routine procedures due to significant risk of systemic toxicity. - Using such a high concentration would lead to severe vasoconstriction and a high likelihood of adverse cardiovascular events. *1:20,000* - This concentration is also very high for use with local anesthetics, although less concentrated than 1:10,000. It would still significantly increase the risk of systemic side effects. - It is not a standard concentration for routine local anesthetic admixture.

Q: A 45-year-old man undergoing surgery suddenly becomes unresponsive, and his pulse is unrecordable after receiving regional anesthesia with 0.25% bupivacaine. What is the best immediate management?

CPCR with 20% Intralipid. ***CPCR with 20% Intralipid*** - The sudden unresponsiveness and unrecordable pulse after regional anesthesia with bupivacaine suggest **local anesthetic systemic toxicity (LAST)**. - **20% Intralipid** (lipid emulsion) is the cornerstone of treatment for severe LAST because it acts as a **lipid sink**, binding to lipophilic local anesthetics like bupivacaine and sequestering them from target organs. *CPCR with sodium bicarbonate* - While sodium bicarbonate is used in some resuscitation scenarios, particularly for severe metabolic acidosis or tricyclic antidepressant overdose, it is **not the primary or most effective treatment for bupivacaine-induced cardiac arrest**. - Its use in LAST is supportive, mainly for treating **acidosis** that can worsen local anesthetic toxicity, but it does not directly counteract the systemic effects of the local anesthetic. *CPCR with dobutamine* - **Dobutamine** is an inotropic agent used to increase myocardial contractility and heart rate in cases of cardiac decompensation. - It is **not indicated as a first-line treatment for cardiac arrest** secondary to LAST; direct reversal of the anesthetic's effects is paramount. *CPCR with calcium* - Administering **calcium** is primarily indicated for cardiac arrest caused by **hyperkalemia** or **calcium channel blocker overdose**. - It is **not effective in reversing the cardiotoxic effects of bupivacaine** and is not part of the standard resuscitation protocol for LAST.

Q: Which local anesthetic is associated with the lowest risk of cardiotoxicity?

Ropivacaine. ***Ropivacaine*** - **Ropivacaine** is an **amide-type local anesthetic** known for its **lower cardiotoxicity** compared to bupivacaine. - This is attributed to its **reduced lipid solubility** and **faster dissociation from cardiac sodium channels**, leading to less potent cardiac effects. *Bupivacaine* - **Bupivacaine** is associated with a **higher risk of cardiotoxicity**, particularly **ventricular arrhythmias** and **cardiac arrest**, especially with accidental intravascular injection. - Its **high lipid solubility** and **tight binding to cardiac sodium channels** contribute to its potent cardiodepressant effects, making resuscitation difficult. *Lidocaine* - While generally considered safer than bupivacaine, **lidocaine** can still cause **cardiovascular depression** and **arrhythmias** at high plasma concentrations. - Its shorter duration of action and **less potent cardiotoxicity** make it a common choice, but it is not the local anesthetic with the lowest cardiotoxicity profile among the options. *Mepivacaine* - **Mepivacaine** has a similar cardiotoxicity profile to lidocaine and is considered to have **intermediate cardiotoxicity**. - It is **not the safest** option regarding cardiotoxicity when compared to ropivacaine, especially at higher doses or with accidental intravascular administration.

Question 1

Regarding malignant hyperthermia, which statement about local anesthetics is correct?

Accepted Answer

Local anesthetics are safe to use in malignant hyperthermia-susceptible patients

Answer

Amide local anesthetics can trigger malignant hyperthermia

Answer

Ester local anesthetics are contraindicated in malignant hyperthermia

Answer

Local anesthetics should be avoided in patients with family history of malignant hyperthermia

Question 2

An 18 years old woman in the active stage of labour requests an epidural anaesthesia for delivery. Immediately following the epidural injection of 12ml of 2% lidocaine, the patient complains of lip numbness and becomes apprehensive. What is the presumptive diagnosis?

Accepted Answer

Systemic toxicity to drug administered

Answer

Allergy to drug administered

Answer

Vasovagal shock

Answer

Drug entered SA space

Question 3

Which of the following is commonly used as an epidural anesthetic agent?

Accepted Answer

All of the options

Answer

Bupivacaine

Answer

Chloroprocaine

Answer

Lidocaine

Question 4

Anesthetic agent with vasoconstrictor is contraindicated in

Accepted Answer

Digital block

Answer

Spinal block

Answer

Regional anesthesia

Answer

Epidural block

Question 5

The site of action of local anaesthetic in epidural anesthesia is

Accepted Answer

Spinal nerve root

Answer

Anterior root of spinal nerve

Answer

Epidural neural tissue

Answer

Spinal cord

Question 6

True regarding EMLA is

Accepted Answer

Its mixture of 25 mg/g Lidocaine + 25 mg/g prilocaine used for skin anaesthesia

Answer

used for bilateral nerve block

Answer

used as general anaesthesia in pediatric use

Answer

None of the above

Question 7

In spinal anesthesia, which local anesthetic has the longest duration of action?

Accepted Answer

Bupivacaine

Answer

Procaine

Answer

Tetracaine

Answer

Lidocaine

Question 8

What is the concentration of adrenaline typically used with local anesthetics?

Accepted Answer

1:200,000

Answer

1:100,000

Answer

1:10,000

Answer

1:20,000

Question 9

A 45-year-old man undergoing surgery suddenly becomes unresponsive, and his pulse is unrecordable after receiving regional anesthesia with 0.25% bupivacaine. What is the best immediate management?

Accepted Answer

CPCR with 20% Intralipid

Answer

CPCR with sodium bicarbonate

Answer

CPCR with dobutamine

Answer

CPCR with calcium

Question 10

Which local anesthetic is associated with the lowest risk of cardiotoxicity?

Accepted Answer

Ropivacaine

Answer

Bupivacaine

Answer

Lidocaine

Answer

Mepivacaine

Local Anesthetics — MCQs

Local Anesthetics — MCQs

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