Local Anesthetics — MCQs

Local Anesthetics Indian Medical PG Practice Questions and MCQs

Question 221: Which local anesthetic is commonly used for spinal anesthesia?

A. Lidocaine
B. Bupivacaine (Correct Answer)
C. Procaine
D. Mepivacaine

Explanation: ***Bupivacaine*** - **Bupivacaine** is frequently used for spinal anesthesia due to its **long duration of action** and high potency. - It provides effective surgical anesthesia and postoperative analgesia with a relatively low risk of systemic toxicity when administered intrathecally. *Lidocaine* - While **lidocaine** can be used for spinal anesthesia, its shorter duration of action limits its utility for longer procedures. - It has also been associated with a higher incidence of **transient neurologic symptoms (TNS)** when used intrathecally, although this is rare with lower concentrations. *Procaine* - **Procaine** is an **ester-type local anesthetic** with a very short duration of action, making it less suitable for most spinal anesthesia applications. - It is rarely used for spinal anesthesia in modern practice due to the availability of longer-acting agents. *Mepivacaine* - **Mepivacaine** is an **amide-type local anesthetic** with an intermediate duration of action. - Although it can be used for spinal anesthesia, it is generally less favored than bupivacaine due to a slightly shorter duration and potential for increased neurotoxicity compared to other long-acting agents.

Question 222: Benzocaine is used in which type of anesthesia?

A. Topical (Correct Answer)
B. Spinal
C. Epidural
D. All of the options

Explanation: ***Topical*** - **Benzocaine** is an **ester-type local anesthetic** that is primarily used for **topical anesthesia** due to its poor water solubility and slow absorption. - It is commonly found in over-the-counter products for pain relief in conditions like **sore throat**, **sunburn**, or to numb the skin before minor procedures. *Spinal* - **Spinal anesthesia** involves injecting local anesthetics into the cerebrospinal fluid in the **subarachnoid space** to block sensory and motor nerves. - Drugs like **bupivacaine**, **lidocaine**, or **tetracaine** are typically used for spinal anesthesia, not benzocaine, which is poorly suited for systemic administration due to its high toxicity profile when absorbed. *Epidural* - **Epidural anesthesia** involves injecting local anesthetics into the **epidural space** to block nerve roots as they exit the spinal cord. - Common drugs used include **bupivacaine**, **lidocaine**, and **ropivacaine**, providing regional pain relief without significant systemic absorption. *All of the options* - This option is incorrect because benzocaine's properties and toxicity profile make it unsuitable for **spinal** and **epidural** anesthesia, limiting its use almost exclusively to topical applications. - While it is a type of anesthetic, its application is highly specific to surface numbing.

Question 223: Which anaesthetic belongs to the ester group?

A. Lignocaine
B. Propofol
C. Procaine (Correct Answer)
D. Benzocaine

Explanation: ***Procaine*** - **Procaine** is a classical **ester-type** local anesthetic, characterized by an ester linkage between the aromatic and amine parts of its chemical structure. - Ester-type local anesthetics are metabolized by **plasma pseudocholinesterase**, leading to a shorter duration of action compared to amides. *Benzocaine* - **Benzocaine** is also an ester local anesthetic, but it is typically used topically due to its poor water solubility and absorption. - While an ester, the question implies a common injectable agent, making procaine a more representative answer for the "ester group" in general anesthetic use. *Lignocaine* - **Lignocaine** (also known as lidocaine) is an **amide-type** local anesthetic, which can be identified by an amide linkage in its chemical structure. - Amide local anesthetics are primarily metabolized in the **liver** and generally have a longer duration of action than esters. *Propofol* - **Propofol** is a **short-acting intravenous general anesthetic** and is not classified as a local anesthetic or belonging to the ester group. - It works by potentiation of **GABA-A receptors** and is used for induction and maintenance of general anesthesia.

Question 224: Cocaine was first used as a local anesthetic by?

A. Holmer Wells
B. Morton
C. Carl Koller (Correct Answer)
D. None of the options

Explanation: ***Carl Koller*** - **Carl Koller** (1857-1944), an Austrian ophthalmologist, is credited with the first clinical use of cocaine as a local anesthetic in 1884. - He demonstrated its efficacy for topical anesthesia in eye surgery, revolutionizing surgical practices. *Holmer Wells* - **Horace Wells** (not Holmer) was an American dentist who pioneered the use of **nitrous oxide** as an anesthetic in dentistry in the 1840s, preceding Koller's work with cocaine. - His contributions were focused on general anesthesia for pain relief during tooth extractions. *Morton* - **William T.G. Morton** was another American dentist who famously demonstrated the use of **ether** as a surgical anesthetic in 1846. - His work popularized surgical anesthesia, but it was not related to cocaine as a local anesthetic. *None of the options* - This option is incorrect because Carl Koller is historically recognized as the pioneer for the clinical use of **cocaine as a local anesthetic**.

Question 225: Which local anesthetic has the highest maximum safe concentration for epidural block?

A. Bupivacaine
B. Lidocaine
C. Ropivacaine
D. Chlorprocaine (Correct Answer)

Explanation: ***Chlorprocaine*** - As an **ester-type** local anesthetic, chlorprocaine is rapidly metabolized by **plasma pseudocholinesterase**, resulting in a very short half-life and lower systemic toxicity. - This rapid metabolism allows for a much higher maximum safe dose compared to amide-type local anesthetics, making it suitable in scenarios where large volumes are needed. *Bupivacaine* - Bupivacaine is an **amide-type** local anesthetic known for its potent **cardiotoxicity** due to its strong binding to cardiac sodium channels and slow dissociation. - Its high lipid solubility contributes to its potency and longer duration of action, but also limits its maximum safe dose to prevent systemic toxicity. *Lidocaine* - Lidocaine is an **amide-type** local anesthetic with intermediate potency and duration of action, but it still has a lower maximum safe dose than chloroprocaine. - While less cardiotoxic than bupivacaine, its systemic absorption can lead to **central nervous system toxicity** at higher doses. *Ropivacaine* - Ropivacaine is an **amide-type** local anesthetic that is an S-enantiomer, designed to have a more favorable **cardiotoxicity profile** compared to bupivacaine. - Although it has reduced cardiotoxicity, its maximum safe dose is still limited due to the risk of systemic toxicity, especially CNS effects, and it's less than that of chlorprocaine.

Question 226: Epidural narcotics are preferred over epidural local anesthetics because they cause –

A. Less respiratory depression
B. Less dose is required
C. No motor paralysis (Correct Answer)
D. No retention of urine

Explanation: **No motor paralysis** - Epidural narcotics (opioids) provide **analgesia** by binding to opioid receptors in the spinal cord, primarily affecting pain sensation pathways. - This selective action allows for pain relief without significantly impacting **motor nerve fibers**, thus avoiding motor paralysis. *Less respiratory depression* - While epidural opioids can cause less systemic respiratory depression compared to intravenous administration, they still carry a **risk of respiratory depression**, especially with higher doses or inadequate monitoring. - This is not a primary reason for preference over local anesthetics, as local anesthetics at appropriate doses have a different mechanism and profile regarding respiratory effects. *Less dose is required* - The dose comparison depends on the specific drug and desired effect; however, the primary advantage of epidural narcotics over local anesthetics is not necessarily that a "lesser" dose is required for a therapeutic effect. - Local anesthetics require higher doses to achieve complete **sensory and motor blockade**, whereas opioids provide targeted analgesia at lower doses. *No retention of urine* - Epidural opioids are known to cause **urinary retention** as a common side effect due to their action on sacral parasympathetic outflow. - This is a significant disadvantage, unlike epidural local anesthetics, which can also cause urinary retention but through a different mechanism (motor block of the bladder).

Question 227: What is the most appropriate anaesthesia technique for microlaryngoscopy?

A. Jet ventilation with TIVA
B. Conventional endotracheal intubation (Correct Answer)
C. Apneic technique with TIVA
D. Laryngeal mask airway with spontaneous ventilation

Explanation: ***Conventional endotracheal intubation*** - While other techniques exist, **conventional endotracheal intubation** remains a widely accepted and often preferred method for microlaryngoscopy due to its ability to provide a secure airway, excellent surgical exposure, and controlled ventilation. - This technique allows for adequate **oxygenation and ventilation** during the procedure, which can be prolonged, and it protects the airway from **blood and secretions**. *Jet ventilation with TIVA* - **Jet ventilation** can provide an unobstructed laryngeal view and may be used, but it carries risks such as barotrauma and aspiration, and can cause difficulty with **CO2 clearance**. - While **total intravenous anesthesia (TIVA)** is suitable, the ventilation technique itself may not be the most appropriate primary choice due to its potential complications. *Apneic technique with TIVA* - The **apneic technique** (apneic oxygenation) may offer an unobstructed surgical field but is limited by the duration an individual can be safely apneic without hypercapnia or desaturation and a lack of control over ventilation for longer procedures. - Although **TIVA** is a good anesthetic choice, relying solely on an apneic period for the whole procedure may not be the safest or most practical method for many microlaryngoscopies. *Laryngeal mask airway with spontaneous ventilation* - A **laryngeal mask airway (LMA)** may provide a good view for some laryngeal procedures but does not offer the same level of airway protection against aspiration as an endotracheal tube. - **Spontaneous ventilation** with an LMA might not provide adequate control over gas exchange, especially if the procedure is prolonged or deep anesthesia is required.

Question 228: Most cardiotoxic local anesthetic is:

A. Procaine
B. Lidocaine
C. Ropivacaine
D. Bupivacaine (Correct Answer)

Explanation: ***Bupivacaine*** - **Bupivacaine** is a **highly potent** local anesthetic known for its cardiotoxic effects due to its **lipophilicity** and strong binding to cardiac sodium channels. - Its **slow dissociation** from cardiac sodium channels at toxic plasma concentrations contributes to prolonged arrhythmias and myocardial depression. *Lidocaine* - **Lidocaine** has a **faster onset** and shorter duration of action compared to bupivacaine, making it less cardiotoxic. - While it can cause cardiac effects at high doses, it generally has a **safer cardiac profile** than bupivacaine and is often used as an antiarrhythmic. *Procaine* - **Procaine** is an **ester-type** local anesthetic, which means it is rapidly metabolized by plasma cholinesterases. - This rapid breakdown gives it a **short duration of action** and a **low potential for systemic toxicity**, including cardiotoxicity. *Ropivacaine* - **Ropivacaine** is a **less lipophilic** analog of bupivacaine, designed to have a reduced cardiotoxicity profile. - While it still has potential for cardiotoxicity at very high doses, it demonstrates a **higher therapeutic index** for cardiac rhythm compared to bupivacaine.

Practice by Chapter

Chemistry and Mechanism of Action

Practice Questions

Pharmacokinetics of Local Anesthetics

Practice Questions

Amide Local Anesthetics

Practice Questions

Ester Local Anesthetics

Practice Questions

Clinical Uses of Local Anesthetics

Practice Questions

Toxicity of Local Anesthetics

Practice Questions

Management of Local Anesthetic Systemic Toxicity

Practice Questions

Adjuvants to Local Anesthetics

Practice Questions

Maximum Safe Doses

Practice Questions

Local Anesthetics in Special Populations

Practice Questions

Allergic Reactions to Local Anesthetics

Practice Questions

Future Developments in Local Anesthetics

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free