Regional Anesthesia — MCQs

Regional Anesthesia Indian Medical PG Practice Questions and MCQs

Question 161: Which of the following are theories of regional anesthesia

A. Specificity Theory & Membrane Expansion Theory
B. Specific Receptor Theory & Membrane Expansion Theory (Correct Answer)
C. Specificity Theory & Gate Control Theory
D. Specific Receptor Theory & Gate Control Theory

Explanation: ***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.

Question 162: Interscalene approach to brachial plexus block does not provide optimal surgical anaesthesia in the area of distribution of which of the following nerve?

A. Median
B. Musculocutaneous
C. Radial
D. Ulnar (Correct Answer)

Explanation: ***Ulnar*** - The **ulnar nerve** (C8-T1) emerges from the lower trunk of the brachial plexus. During an **interscalene block**, the local anesthetic is typically deposited at the level of the roots and trunks (C5-C7), which is superior to the origin of the lower trunk that gives rise to the ulnar nerve. - Due to the **cephalad spread** of the local anesthetic from an interscalene block, the **C8 and T1** nerve roots (and thus the ulnar nerve) are often not adequately blocked, leading to suboptimal anesthesia in its distribution. *Median* - The **median nerve** (C5-T1) originates from the lateral and medial cords, which are typically well-covered by the spread of local anesthetic in an interscalene block due to its formation from the middle and upper trunks. - Optimal anesthesia in the distribution of the median nerve is generally achieved with an interscalene block, as its nerve roots are within the targeted antegrade spread. *Musculocutaneous* - The **musculocutaneous nerve** (C5-C7) arises from the lateral cord, which is formed by the upper and middle trunks. These structures are reliably blocked during an interscalene approach. - Sensory and motor functions of the musculocutaneous nerve, such as **biceps contraction** and lateral forearm sensation, are usually well anesthetized. *Radial* - The **radial nerve** (C5-T1) is a branch of the posterior cord, which receives fibers from all three trunks. Its upper and middle trunk components are generally well-blocked by an interscalene approach. - While complete anesthesia of the entire brachial plexus can be variable, the radial nerve is more consistently affected by an interscalene block than the ulnar nerve due to its more extensive proximal root contributions which are within the typical spread.

Question 163: All are absolute contraindication of neuraxial anaesthesia except:

A. Spinal deformity (Correct Answer)
B. Local infection of site
C. Raised Intracranial pressure
D. Coagulopathy

Explanation: ***Spinal deformity*** - While a **spinal deformity** can make neuraxial anesthesia technically challenging, it is generally considered a **relative contraindication**, not an absolute one. - The procedure can still be performed by an experienced anesthetist, potentially with imaging guidance, if the benefits outweigh the risks. *Local infection of site* - A **local infection** at the needle insertion site is an **absolute contraindication** due to the high risk of spreading infection into the central nervous system, leading to potentially life-threatening conditions such as **meningitis** or **epidural abscess**. - Introducing bacteria into the cerebrospinal fluid or epidural space is a severe complication to avoid. *Raised Intracranial pressure* - **Raised intracranial pressure (ICP)** is an **absolute contraindication** because puncturing the dura mater can lead to a rapid decrease in cerebrospinal fluid (CSF) pressure, resulting in brain herniation. - This sudden pressure gradient can cause devastating neurological injury or death. *Coagulopathy* - **Coagulopathy**, whether intrinsic (e.g., hemophilia) or iatrogenic (e.g., anticoagulation), is an **absolute contraindication** to neuraxial anesthesia. - The primary concern is the formation of an **epidural or spinal hematoma**, which can compress the spinal cord and lead to permanent neurological damage, including paralysis.

Question 164: All of the following are complications of epidural anaesthesia, EXCEPT:

A. Urinary retention
B. Total spinal analgesia
C. Hypopnoea
D. Hypertension (Correct Answer)

Explanation: ***Hypertension*** - Epidural anesthesia commonly causes **vasodilation** and a subsequent drop in **blood pressure** (hypotension), not hypertension, due to sympathetic blockade. - While hypertension can occur due to pain or anxiety during the procedure, it is not a direct physiological complication of the epidural anesthetic itself. *Urinary retention* - Epidural anesthesia can affect the nerves controlling the **bladder**, leading to temporary **urinary retention**. - This is a common complication, often requiring catheterization until the epidural wears off. *Total spinal analgesia* - This occurs if the epidural needle inadvertently punctures the **dura** and a large dose of local anesthetic is injected into the **subarachnoid space**. - It results in widespread **sensory and motor blockade**, potentially leading to respiratory arrest and hemodynamic collapse. *Hypopnoea* - High epidural blocks or accidental **intrathecal administration** can cause paralysis of **intercostal muscles** and the diaphragm. - This can lead to **respiratory depression** (hypopnoea) or even apnea, necessitating ventilatory support.

Question 165: In all of the following conditions, neuraxial blockade is absolutely contraindicated, except:

A. Patient refusal
B. Severe hypovolemia
C. Pre-existing neurological deficits (Correct Answer)
D. Coagulopathy

Explanation: ***Pre-existing neurological deficits*** - While careful consideration is needed, pre-existing neurological deficits are generally a **relative contraindication** rather than an absolute one for neuraxial blockade. - The decision depends on the nature and stability of the deficit, potential for worsening, and the benefits of neuraxial anesthesia versus the risks. *Patient refusal* - **Patient refusal** is always an absolute contraindication for any medical procedure, including neuraxial blockade. - Informed consent requires the patient's voluntary agreement, and a refusal must be respected. *Severe hypovolemia* - **Severe hypovolemia** is an absolute contraindication for neuraxial blockade due to the risk of profound hypotension. - Neuraxial blockade causes sympathetic blockade, leading to vasodilation and reduced venous return, which can be catastrophic in an already hypovolemic patient. *Coagulopathy* - **Coagulopathy**, whether intrinsic or iatrogenic, is an absolute contraindication due to the high risk of **epidural hematoma** or **spinal hematoma**. - These hematomas can cause nerve compression, leading to devastating neurological complications like paraplegia.

Question 166: The most common complication of interscalene block:-

A. Pneumothorax
B. Phrenic block (Correct Answer)
C. Hypotension
D. Horner syndrome

Explanation: ***Phrenic block*** - The **phrenic nerve** runs anterior to the anterior scalene muscle within the **interscalene groove**, making it highly susceptible to local anesthetic spread during an interscalene block. - This complication is very common, occurring in nearly all patients, and can lead to **hemidiaphragmatic paresis**, causing a decrease in pulmonary function. *Pneumothorax* - While a serious complication of interscalene block, **pneumothorax** is relatively rare because the pleura is not typically in the needle's path with proper technique. - It usually occurs due to an accidental puncture of the **pleural membrane**, leading to air accumulation in the pleural space. *Hypotension* - **Hypotension** is not a primary or most common complication of an interscalene block, which primarily targets nerves supplying the shoulder and arm. - Significant hypotension would more likely be associated with systemic absorption of local anesthetic or a central neuraxial block. *Horner syndrome* - **Horner syndrome** can occur when the **stellate ganglion** (part of the sympathetic chain) is blocked due to the spread of local anesthetic from the interscalene groove to the paravertebral space. - Although it is a recognized complication, it is less common than phrenic nerve block and typically resolves spontaneously.

Question 167: "Triangle of Petit" is a landmark for which block?

A. Epidural block
B. TAP block (Correct Answer)
C. Spinal block
D. Bier's block

Explanation: **TAP block** - The **Triangle of Petit** (or lumbar triangle) is an important anatomical landmark used to approximate the location for a **transversus abdominis plane (TAP) block**. - This triangle is formed by the **latissimus dorsi muscle** posteriorly, the **external oblique muscle** anteriorly, and the **iliac crest** inferiorly. *Epidural block* - An epidural block involves injecting local anesthetic into the **epidural space** surrounding the spinal cord. - Its landmarks are typically based on vertebral palpable structures, not the Triangle of Petit. *Spinal block* - A spinal block (or subarachnoid block) involves injecting local anesthetic into the **subarachnral space**, directly into the cerebrospinal fluid. - Access is gained through the dura and arachnoid membranes, with landmarks again being specific vertebral levels. *Bier's block* - Bier's block, or **intravenous regional anesthesia**, involves isolated limb anesthesia by injecting local anesthetic intravenously after exsanguination and tourniquet application. - It does not involve any specific anatomical surface landmarks like the Triangle of Petit.

Question 168: Spinal anesthesia is given at which of the following levels?

A. L2-4 (Correct Answer)
B. Below L5 (caudal)
C. L1-2
D. Midline of thorax

Explanation: **L2-4** - Spinal anesthesia is typically administered below the **termination of the spinal cord (conus medullaris)**, which usually ends around the L1-L2 vertebral level in adults. - The **L2-4 interspaces** are generally safe and commonly chosen to avoid accidental spinal cord injury while providing effective regional anesthesia. *Below L5 (caudal)* - Administering anesthesia "below L5" typically refers to a **caudal block**, which targets the sacral hiatus and is used for anesthesia of the perineum and lower extremities but is not considered spinal anesthesia. - While technically below the spinal cord, inserting a needle at this level doesn't directly access the **subarachnoid space** for spinal anesthesia and carries different indications and risks. *L1-2* - This level is generally avoided for routine spinal anesthesia, as the **spinal cord (conus medullaris)** can extend down to L2 in some adults. - Puncturing at this level carries a higher risk of **direct spinal cord trauma**, which can lead to neurological deficits. *Midline of thorax* - Administering spinal anesthesia in the **thoracic region** is extremely risky and not routinely performed for typical spinal blocks. - This area contains the **spinal cord throughout**, and accidental puncture or drug administration can cause severe neurological damage or high spinal block with cardiorespiratory compromise.

Question 169: Which of the following is not a contraindication for neuraxial block?

A. Patient on clopidogrel
B. Patient on antihypertensive medication (Correct Answer)
C. Local infection
D. Platelet count < 50,000

Explanation: ***Patient on antihypertensive medication*** - Antihypertensive medications are generally **not a contraindication** for neuraxial block; however, careful management of **blood pressure** especially following the sympathetic block is essential. - The primary concern is **hypotension** due to the sympathetic blockade, which can be managed with fluids and vasopressors, not an absolute contraindication. *Patient on clopidogrel* - **Clopidogrel** is an **antiplatelet agent** that increases the risk of **spinal hematoma** if a neuraxial block is performed. - This medication should typically be discontinued for a specific period before neuraxial procedures to minimize bleeding risk. *Local infection* - Performing a neuraxial block through an infected area increases the risk of introducing **pathogens into the subarachnial space**, leading to severe complications like **meningitis** or an **epidural abscess**. - This is an **absolute contraindication** to protect against central nervous system infection. *Platelet count < 50,000* - A **low platelet count** indicates impaired hemostasis, significantly increasing the risk of **bleeding** and the formation of a **spinal hematoma** following neuraxial puncture. - While exact thresholds vary, a platelet count below 50,000 is generally considered an **absolute contraindication** for neuraxial anesthesia.

Question 170: What is the maximum concentration allowed for epidural block?

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

Explanation: ***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.

Practice by Chapter

Neuraxial Anatomy

Practice Questions

Spinal Anesthesia

Practice Questions

Epidural Anesthesia

Practice Questions

Combined Spinal-Epidural Anesthesia

Practice Questions

Peripheral Nerve Blocks: Upper Extremity

Practice Questions

Peripheral Nerve Blocks: Lower Extremity

Practice Questions

Truncal Blocks

Practice Questions

Ultrasound-Guided Regional Anesthesia

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Complications of Regional Anesthesia

Practice Questions

Regional Anesthesia in Pediatric Patients

Practice Questions

Regional Anesthesia in Obstetrics

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Continuous Peripheral Nerve Catheters

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