Local Anesthetics Practice Questions

Q: The composition of the given anesthetic product is:

5 % lignocaine and 5 % prilocaine. ***5 % lignocaine and 5 % prilocaine*** - The image clearly displays "emla 5 g cream". **EMLA (Eutectic Mixture of Local Anesthetics)** cream is a widely recognized topical anesthetic preparation. - EMLA cream is composed of a **eutectic mixture of 2.5% lidocaine (lignocaine) and 2.5% prilocaine**, which is typically presented as a 5% cream (meaning 5 g of cream contains 2.5 g of lidocaine and 2.5 g of prilocaine, effectively 5% of each active ingredient when referring to the total concentration of local anesthetics). *5 % lignocaine and 5 % benzocaine* - While lignocaine is a common local anesthetic, **benzocaine** is also a local anesthetic but it's not a primary component of EMLA cream. - The combination of 5% lignocaine and 5% benzocaine is not the standard formulation for the product shown in the image. *5 % benzocaine and 5 % tetracaine* - **Benzocaine** and **tetracaine** are both local anesthetics, but this combination is incorrect for EMLA cream. - This pairing would constitute a different topical anesthetic product, not the one identified in the image. *5 % benzocaine and 5 % cocaine* - **Cocaine** is a local anesthetic, but it is also a powerful stimulant and has high abuse potential, making it unsuitable for general topical anesthetic creams due to its severe side effects and regulatory restrictions. - This combination is not found in common medical topical anesthetic preparations like EMLA cream.

Q: A young male was administered regional anesthesia with 0.25% bupivacaine. The patient became unresponsive, and the pulse became unrecordable. What is the best management in this situation?

ECPR with 20% intralipid. ***ECPR with 20% intralipid*** - The scenario describes **Local Anesthetic Systemic Toxicity (LAST)**, likely due to bupivacaine, leading to cardiovascular collapse. - **Intralipid 20%** is the first-line treatment for LAST-induced cardiovascular toxicity, as it acts as a lipid sink for the lipophilic local anesthetic. *ECPR with calcium* - While calcium may be used in certain cardiac arrest scenarios, it is **not the primary treatment for bupivacaine-induced cardiovascular collapse** and LAST. - Calcium might offer some cardiac support but does not directly neutralize the local anesthetic's toxic effects. *ECPR with dobutamine* - **Dobutamine is an inotropic agent** used to improve cardiac contractility but is not indicated as a primary rescue therapy for severe LAST. - It would not address the underlying toxicity caused by bupivacaine and could potentially worsen the situation by increasing myocardial oxygen demand without reversing toxin effects. *ECPR with sodium bicarbonate* - **Sodium bicarbonate** is used to treat metabolic acidosis and can be beneficial in certain drug overdoses to enhance excretion or stabilize cardiac membranes. - However, it is **not the primary or most effective treatment for bupivacaine-induced LAST** and cardiovascular collapse compared to lipid emulsion therapy.

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: Which of the following are theories of regional anesthesia

Specific Receptor Theory & Membrane Expansion Theory. ***Specific Receptor Theory & Membrane Expansion Theory*** - The **Specific Receptor Theory** proposes that local anesthetics bind to specific receptors on the **sodium channels**, preventing sodium influx and thus blocking nerve impulse conduction. - The **Membrane Expansion Theory** suggests that local anesthetics incorporate into the nerve cell membrane, causing it to expand and **alter the conformation** of sodium channels, thereby impairing their function. *Specificity Theory & Membrane Expansion Theory* - **Specificity Theory** is not a recognized theory for the mechanism of action of regional anesthesia. - While **Membrane Expansion Theory** is a recognized theory, it is paired with an incorrect option. *Specificity Theory & Gate Control Theory* - Neither **Specificity Theory** nor **Gate Control Theory** are primary mechanisms explaining the action of regional anesthetics. - **Gate Control Theory** primarily addresses the modulation of pain signals in the dorsal horn of the spinal cord, not the direct nerve blocking action of local anesthetics. *Specific Receptor Theory & Gate Control Theory* - Although **Specific Receptor Theory** is a correct theory for regional anesthesia, it is incorrectly paired with the **Gate Control Theory**. - **Gate Control Theory** explains how non-noxious stimuli can reduce pain perception, rather than the chemical blockade of nerve impulses.

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: Which of the following local anesthetics has the highest maximum concentration allowed for epidural block?

Chlorprocaine. ***Chlorprocaine*** - **Chlorprocaine** is an ester-type local anesthetic that can be safely used in higher concentrations for epidural blocks up to **3%**, due to its rapid hydrolysis by plasma pseudocholinesterase, leading to a very short half-life and reduced systemic toxicity. - Its rapid metabolism minimizes the risk of accumulation and systemic toxicity, making it a suitable choice when a dense block is needed and a short duration of action is acceptable. *Lidocaine* - **Lidocaine** is an amide-type local anesthetic commonly used in epidural blocks, but its maximum concentration for this application is typically limited to **2%** to avoid systemic toxicity. - Higher concentrations of lidocaine are associated with an increased risk of neurological and cardiovascular adverse effects. *Ropivacaine* - **Ropivacaine** is an amide-type local anesthetic that is less cardiotoxic than bupivacaine, with common concentrations for epidural use ranging from **0.2% to 1%**. - Its maximum concentration is significantly lower than chlorprocaine due to its longer duration of action and potential for systemic toxicity at higher doses. *Bupivacaine* - **Bupivacaine** is a potent amide-type local anesthetic with a high risk of cardiotoxicity, and its maximum concentration for epidural use is generally restricted to **0.5%** or even less for continuous infusions. - Using concentrations above this limit significantly increases the risk of severe cardiovascular complications, including arrhythmias and cardiac arrest.

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.

Question 1

The composition of the given anesthetic product is:

Accepted Answer

5 % lignocaine and 5 % prilocaine

Answer

5 % lignocaine and 5 % benzocaine

Answer

5 % benzocaine and 5 % tetracaine

Answer

5 % benzocaine and 5 % cocaine

Question 2

A young male was administered regional anesthesia with 0.25% bupivacaine. The patient became unresponsive, and the pulse became unrecordable. What is the best management in this situation?

Accepted Answer

ECPR with 20% intralipid

Answer

ECPR with calcium

Answer

ECPR with dobutamine

Answer

ECPR with sodium bicarbonate

Question 3

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 4

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 5

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 6

Which of the following are theories of regional anesthesia

Accepted Answer

Specific Receptor Theory & Membrane Expansion Theory

Answer

Specificity Theory & Membrane Expansion Theory

Answer

Specificity Theory & Gate Control Theory

Answer

Specific Receptor Theory & Gate Control Theory

Question 7

Anesthetic agent with vasoconstrictor is contraindicated in

Accepted Answer

Digital block

Answer

Spinal block

Answer

Regional anesthesia

Answer

Epidural block

Question 8

Which of the following local anesthetics has the highest maximum concentration allowed for epidural block?

Accepted Answer

Chlorprocaine

Answer

Lidocaine

Answer

Ropivacaine

Answer

Bupivacaine

Question 9

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 10

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

Accepted Answer

Bupivacaine

Answer

Procaine

Answer

Tetracaine

Answer

Lidocaine

Local Anesthetics — MCQs

Local Anesthetics — MCQs

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