Regional Anesthesia — MCQs

Regional Anesthesia Indian Medical PG Practice Questions and MCQs

Question 81: For which surgical area is a supraclavicular block indicated?

A. Shoulder
B. Neck
C. Arm (Correct Answer)
D. Forearm

Explanation: **Explanation:** The **supraclavicular block** is often referred to as the "spinal of the upper limb" because it provides dense, rapid-onset anesthesia for the entire arm. At the level of the supraclavicular fossa, the brachial plexus is most compact, consisting of three divisions. This anatomical arrangement allows for a reliable block of the **arm, elbow, forearm, and hand**. **Why the options are correct/incorrect:** * **Arm (Correct):** The supraclavicular approach targets the plexus where the divisions are tightly bundled, ensuring anesthesia of the musculocutaneous, radial, ulnar, and median nerves. It is the gold standard for surgeries involving the mid-humerus down to the hand. * **Shoulder (Incorrect):** While it can provide some coverage, the **interscalene block** is the preferred choice for shoulder surgery. The supraclavicular block often misses the suprascapular nerve and the cervical plexus branches (C3-C4) required for complete shoulder anesthesia. * **Neck (Incorrect):** The neck is supplied by the **cervical plexus**, not the brachial plexus. * **Forearm (Incorrect):** While the block *does* cover the forearm, the question asks for the primary surgical area indication. In NEET-PG contexts, if "Arm" is an option, it represents the most proximal extent of the block's reliable coverage compared to more distal blocks like the infraclavicular or axillary blocks. **High-Yield Clinical Pearls for NEET-PG:** 1. **Anatomy:** The plexus is located posterior and superior to the **subclavian artery**. 2. **Complications:** The most classic complication is **pneumothorax** (due to the proximity of the cupula of the lung). Other risks include Horner’s syndrome and phrenic nerve palsy (though less common than in interscalene blocks). 3. **Contraindication:** It should be avoided in patients with severe underlying lung disease (COPD) due to the risk of accidental phrenic nerve block or pneumothorax.

Question 82: What is the most commonly used local anesthetic for intravenous regional anesthesia (Bier's block)?

A. Bupivacaine
B. Lignocaine (Correct Answer)
C. Prilocaine
D. Chloroprocaine

Explanation: **Explanation:** **Intravenous Regional Anesthesia (IVRA)**, commonly known as **Bier’s Block**, involves the injection of a local anesthetic into the venous system of an extremity distal to a double-cuffed pneumatic tourniquet. **Why Lignocaine is the Correct Answer:** **Lignocaine (Lidocaine)** is the gold standard and most commonly used agent for Bier’s block globally. It is preferred due to its rapid onset, moderate duration of action, and a relatively high safety profile when the tourniquet is deflated. The standard concentration used is **0.5% preservative-free lignocaine** (without adrenaline). **Analysis of Incorrect Options:** * **Bupivacaine (Option A):** This is **strictly contraindicated** in Bier’s block. Because IVRA involves a large volume of anesthetic, accidental or intentional tourniquet deflation can lead to systemic bolus. Bupivacaine is highly cardiotoxic and can cause fatal refractory arrhythmias. * **Prilocaine (Option C):** While Prilocaine is actually considered the *safest* agent for IVRA due to its high therapeutic index and rapid metabolism, it is not the *most commonly used* (especially in India/USA) due to the risk of **methemoglobinemia** at high doses and limited availability. * **Chloroprocaine (Option D):** This ester-type anesthetic is rarely used for IVRA due to a high incidence of thrombophlebitis and a very short duration of action. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** The anesthetic works by diffusing from the veins into the adjacent peripheral nerves (vaza nervorum). * **Safety Rule:** The tourniquet must remain inflated for at least **20 minutes** to allow for tissue fixation of the drug, preventing a toxic systemic bolus upon release. * **Adjuvants:** Opioids are generally ineffective in IVRA; however, NSAIDs (like Ketorolac) can be added to improve post-deflation analgesia. * **Drug of Choice:** Lignocaine (0.5%). **Safest Drug:** Prilocaine. **Contraindicated Drug:** Bupivacaine.

Question 83: Following injection of local anesthesia for lower molar extraction using a classical inferior alveolar nerve block, which space has the highest chance of infection?

A. Lateral pharyngeal space
B. Pterygomandibular space (Correct Answer)
C. Parapharyngeal space
D. Pretracheal space

Explanation: **Explanation:** The **Pterygomandibular space** is the correct answer because it is the specific anatomical site where the local anesthetic is deposited during a classical inferior alveolar nerve block (IANB). **1. Why Pterygomandibular Space is Correct:** The IANB aims to deposit anesthesia near the mandibular foramen. This foramen is located within the pterygomandibular space, which is bounded laterally by the ramus of the mandible and medially by the medial pterygoid muscle. If the needle is contaminated or if an infection is present at the injection site, the needle can track microorganisms directly into this potential space, leading to a pterygomandibular space abscess. **2. Why Other Options are Incorrect:** * **Lateral pharyngeal / Parapharyngeal space:** These terms are often used interchangeably. While the pterygomandibular space communicates posteriorly with the parapharyngeal space, it is not the primary site of deposition. Infection here is usually a secondary spread from the pterygomandibular space or tonsillar infections. * **Pretracheal space:** This is located in the neck, anterior to the trachea. It is anatomically distant from the site of a dental block and is typically involved in infections originating from the thyroid, esophagus, or trachea. **High-Yield Clinical Pearls for NEET-PG:** * **Boundaries:** Pterygomandibular space contains the Inferior Alveolar Nerve, Artery, and Vein, and the Lingual Nerve. * **Trismus:** A common sign of infection or hematoma in this space is trismus (difficulty opening the mouth) due to irritation of the medial pterygoid muscle. * **Needle Landmark:** The needle passes through the buccinator muscle to reach this space during an IANB.

Question 84: A patient presents with trismus. Which of the following techniques will block the mylohyoid nerve, incisive nerve, and long buccal nerve?

A. Akinosi technique (Correct Answer)
B. Gow-Gates technique
C. V-block technique
D. Conventional inferior alveolar nerve block

Explanation: The correct answer is **Akinosi technique** (Closed-mouth mandibular nerve block). ### **Explanation of the Correct Answer** The **Akinosi technique** is specifically designed for patients with **trismus** (limited mouth opening). It is a "closed-mouth" technique where the needle is advanced into the pterygomandibular space. Because the anesthetic is deposited at a higher level than the conventional block, it diffuses to involve the **inferior alveolar nerve** (and its incisive branch), the **lingual nerve**, the **mylohyoid nerve**, and frequently the **long buccal nerve**. Its ability to block the mylohyoid nerve is a distinct advantage, as this nerve often provides accessory innervation to the mandibular molars, leading to failed anesthesia in other techniques. ### **Analysis of Incorrect Options** * **Gow-Gates technique:** While this is a "true" mandibular nerve block that anesthetizes all branches (including the long buccal), it **requires the patient to open their mouth wide**. This makes it impossible to perform in a patient with trismus. * **V-block technique (Vazirani-Akinosi):** This is actually a synonym for the Akinosi technique. However, in standard MCQ formats, "Akinosi" is the primary eponymous name used. * **Conventional Inferior Alveolar Nerve Block (IANB):** This technique requires the mouth to be open. Furthermore, it frequently fails to block the **long buccal nerve** (which requires a separate injection) and the **mylohyoid nerve**. ### **High-Yield Clinical Pearls for NEET-PG** * **Akinosi Landmark:** The maxillary mucogingival junction at the level of the third molar. * **Gow-Gates Landmark:** The neck of the mandibular condyle (highest success rate but slowest onset). * **Trismus Management:** Akinosi is the gold standard for regional anesthesia when the patient cannot open their mouth due to infection, trauma, or TMJ dysfunction. * **Nerves Blocked in Akinosi:** Inferior alveolar, Lingual, Mylohyoid, Incisive, Mental, and often the Long Buccal nerve.

Question 85: Levo-bupivacaine is administered by which of the following routes?

A. Nasogastric
B. Epidural (Correct Answer)
C. Intravenous
D. All

Explanation: **Explanation:** **Levo-bupivacaine** is the S-enantiomer of the amide local anesthetic bupivacaine. It is primarily used for **regional anesthesia**, specifically via the **epidural route**, spinal anesthesia, and peripheral nerve blocks. **Why Epidural is Correct:** Levo-bupivacaine works by blocking sodium channels in nerve fibers, preventing the propagation of action potentials. It is preferred for epidural administration in obstetrics and major surgeries because it provides excellent sensory blockade with a longer duration of action. Crucially, it has a **lower risk of cardiotoxicity and neurotoxicity** compared to racemic bupivacaine, making it a safer profile for high-volume regional blocks. **Why Other Options are Incorrect:** * **Nasogastric:** Local anesthetics are not administered via NG tubes as they are intended for site-specific nerve blockade, not systemic absorption through the GI tract. * **Intravenous:** Intravenous administration of potent local anesthetics like bupivacaine is strictly avoided (except for specific uses of Lidocaine) because it can lead to **Local Anesthetic Systemic Toxicity (LAST)**, resulting in seizures and fatal cardiac arrhythmias. **High-Yield Clinical Pearls for NEET-PG:** * **Safety Profile:** Levo-bupivacaine and Ropivacaine are "pure isomers" developed to reduce the cardiac side effects associated with the R-isomer of bupivacaine. * **Differential Block:** It provides a better "differential block" (sensory block > motor block), which is ideal for "walking epidurals" in labor analgesia. * **Toxicity Management:** If accidental IV injection occurs leading to toxicity, the antidote of choice is **20% Intralipid (Lipid Emulsion Therapy)**.

Question 86: What is the maximum safe dose of bupivacaine?

A. 1 mg/kg
B. 2 mg/kg (Correct Answer)
C. 3 mg/kg
D. 5 mg/kg

Explanation: **Explanation:** Bupivacaine is a potent, long-acting amide local anesthetic. The maximum safe dose of bupivacaine is **2 mg/kg** (without epinephrine) and up to **2.5–3 mg/kg** (with epinephrine). This limit is strictly observed because bupivacaine is significantly more **cardiotoxic** than other local anesthetics like lidocaine. It binds strongly to sodium channels in the myocardium and dissociates slowly during diastole (the "fast-in, slow-out" phenomenon), leading to refractory ventricular arrhythmias and cardiovascular collapse. **Analysis of Options:** * **Option A (1 mg/kg):** This is an underestimation. While conservative, it is below the established clinical safety threshold for a healthy adult. * **Option B (2 mg/kg):** **Correct.** This is the standard maximum recommended dose for plain bupivacaine to avoid Local Anesthetic Systemic Toxicity (LAST). * **Option C (3 mg/kg):** This dose is generally considered the upper limit only when bupivacaine is combined with **epinephrine**, which slows systemic absorption through vasoconstriction. * **Option D (5 mg/kg):** This is the maximum safe dose for **Lidocaine (plain)**. Using this dose for bupivacaine would almost certainly result in fatal toxicity. **High-Yield Clinical Pearls for NEET-PG:** * **Cardiotoxicity:** Bupivacaine has a low therapeutic index. The CC/CNS ratio (dose required for cardiovascular collapse vs. seizures) is lower for bupivacaine (~2.0) than lidocaine (~7.0). * **Antidote:** In case of LAST, the specific treatment is **20% Intravenous Lipid Emulsion (ILE)** therapy. * **Levobupivacaine & Ropivacaine:** These are S-enantiomers developed to provide similar anesthesia with significantly reduced cardio- and neurotoxicity compared to racemic bupivacaine. * **Maximum Dose of Lidocaine:** 5 mg/kg (plain) and 7 mg/kg (with epinephrine).

Question 87: A 48-year-old male with triple vessel disease and longstanding diabetes developed gangrene in his left lower foot. Which is the best mode of anesthesia?

A. Popliteal block (Correct Answer)
B. Sciatic block
C. Femoral block
D. Saphenous nerve block

Explanation: **Explanation:** The patient presents with significant comorbidities (Triple Vessel Disease and Diabetes Mellitus), making him a high-risk candidate for General Anesthesia. For surgeries involving the foot and ankle, a **Popliteal Sciatic Nerve Block** is the preferred technique [2]. **Why Popliteal Block is Correct:** The popliteal block targets the sciatic nerve in the popliteal fossa, just before it divides into the tibial and common peroneal nerves [1]. It provides complete anesthesia for the foot and ankle (except for a small medial strip supplied by the saphenous nerve). In a patient with severe cardiac disease (TVD), it offers excellent hemodynamic stability by avoiding the sympathetic blockade associated with spinal or epidural anesthesia. **Analysis of Incorrect Options:** * **Sciatic Block:** While a proximal sciatic block (e.g., Labat’s approach) would also anesthetize the foot, it causes motor blockade of the entire lower leg and is technically more uncomfortable for the patient. The popliteal approach is more distal, specific to foot surgery, and allows for easier catheter placement for postoperative analgesia [2]. * **Femoral Block:** This targets the anterior thigh. It provides no anesthesia to the foot (except for the terminal saphenous branch) and is inappropriate for gangrene debridement or amputation [2]. * **Saphenous Nerve Block:** This is a pure sensory block of the medial leg and foot. It is used only as a supplement to a sciatic/popliteal block and cannot provide surgical anesthesia alone. **High-Yield Clinical Pearls for NEET-PG:** * **Indication:** Popliteal block is the "Gold Standard" for foot and ankle surgeries (e.g., Achilles tendon repair, diabetic foot debridement) [2]. * **Sparing:** It spares the hamstrings, allowing the patient to maintain better mobility compared to a high sciatic block. * **The "Ring Block":** For complete foot anesthesia, a popliteal block is often combined with a saphenous nerve block to cover the medial malleolus area. * **Safety:** In TVD patients, regional blocks are preferred to avoid the myocardial depressant effects of general anesthetics [3].

Question 88: The segmental level of spinal anesthesia depends on which of the following factors?

A. Volume of the local anesthetic injected
B. Specific gravity of the local anesthetic solution
C. Posture of the patient
D. All of the above (Correct Answer)

Explanation: The level of a spinal block (the dermatomal spread of local anesthetic within the subarachnoid space) is determined by a complex interplay of drug characteristics, patient factors, and procedural techniques. **Explanation of Factors:** 1. **Specific Gravity (Baricity):** This is the most critical factor. The relationship between the density of the local anesthetic and the density of cerebrospinal fluid (CSF) determines how the drug moves. **Hyperbaric** solutions (denser than CSF, usually containing glucose) sink to dependent areas, while **hypobaric** solutions rise. 2. **Posture of the Patient:** Because of baricity, the patient's position during and immediately after injection dictates the spread. For example, if a hyperbaric drug is injected while the patient is sitting, it will settle toward the sacral fibers (Saddle block). If the patient is placed in the Trendelenburg position, the drug will spread cephalad (toward the head). 3. **Volume and Dose:** While baricity is dominant, the total volume and dose of the local anesthetic also influence the height of the block. A larger volume creates a greater pressure gradient and physical displacement within the fixed space of the spinal canal, typically leading to a higher level. **High-Yield Clinical Pearls for NEET-PG:** * **Most Important Factor:** Baricity (Specific Gravity) is considered the single most important factor for determining spread. * **CSF Volume:** Low CSF volume (seen in obesity, pregnancy, or the elderly) is associated with a higher level of block for a given dose. * **Site of Injection:** Unlike epidural anesthesia, the site of injection (e.g., L3-L4 vs. L4-L5) has a minimal effect on the final level of spinal anesthesia. * **Drug Concentration:** Concentration alone does not affect the level of spread, but it does affect the **quality and duration** of the motor and sensory block.

Question 89: Which was the first local anesthetic used for spinal block?

A. Cocaine (Correct Answer)
B. Procaine
C. Prilocaine
D. Lignocaine

Explanation: **Explanation:** The correct answer is **Cocaine (Option A)**. Cocaine, an alkaloid derived from the coca leaf, was the first local anesthetic discovered. Its journey into spinal anesthesia began after **Carl Koller** first demonstrated its topical analgesic properties in ophthalmology (1884). In **1898, August Bier** performed the first successful clinical spinal anesthetic using intrathecal cocaine, famously testing it on himself and his assistant. **Analysis of Incorrect Options:** * **B. Procaine:** Synthesized by Alfred Einhorn in 1905 (as Novocaine), it was the first synthetic ester local anesthetic. While it replaced cocaine due to lower toxicity and lack of addiction potential, it was not the first used. * **C. Prilocaine:** An amide local anesthetic developed much later (1950s). It is clinically significant for its association with methemoglobinemia but has no role in the history of the first spinal block. * **D. Lignocaine (Lidocaine):** Synthesized by Nils Löfgren in 1943, it is the "gold standard" amide anesthetic. While widely used for spinal anesthesia today, it was developed decades after the initial discovery of spinal blocks. **High-Yield Clinical Pearls for NEET-PG:** * **August Bier** is known as the "Father of Spinal Anesthesia." * **Corning** (1885) is often credited with the first experimental (though likely peridural) injection, but Bier (1898) is credited with the first intentional spinal block. * **Cocaine** is the only naturally occurring local anesthetic and the only one with significant **vasoconstrictive** properties (inhibits norepinephrine reuptake). * **Sequence of discovery:** Cocaine (1884) → Procaine (1905) → Lidocaine (1943) → Bupivacaine (1957).

Question 90: All of the following are signs of successful stellate ganglion block, except:

A. Flushing of face
B. Conjunctival congestion
C. Mydriasis (Correct Answer)
D. Nasal stuffiness

Explanation: **Explanation:** A **Stellate Ganglion Block (SGB)** involves injecting local anesthetic near the stellate ganglion (formed by the fusion of the inferior cervical and first thoracic sympathetic ganglia). This procedure results in a **sympathetic blockade** of the head, neck, and upper extremity. **Why Mydriasis is the Correct Answer:** The sympathetic nervous system is responsible for pupillary dilation (mydriasis). When the stellate ganglion is blocked, sympathetic outflow is interrupted, leading to the dominance of parasympathetic activity. This results in **Miosis** (constriction of the pupil), not mydriasis. Miosis is a hallmark component of **Horner’s Syndrome**, which signifies a successful block. **Analysis of Incorrect Options:** * **Flushing of the face (A):** Sympathetic blockade causes vasodilation of the cutaneous blood vessels in the head and neck, leading to facial flushing and increased skin temperature. * **Conjunctival congestion (B):** Vasodilation of the conjunctival vessels occurs due to the loss of sympathetic vasoconstrictor tone. * **Nasal stuffiness (D):** Also known as **Guttman’s sign**, this occurs due to the engorgement of the nasal mucosa following sympathetic blockade. **High-Yield Clinical Pearls for NEET-PG:** * **Horner’s Syndrome Tetrad:** Miosis (constricted pupil), Ptosis (drooping eyelid), Anhidrosis (lack of sweating), and Enophthalmos (apparent sinking of the eyeball). * **Anatomical Landmark:** The block is typically performed at the level of the **C6 transverse process (Chassaignac’s tubercle)**. * **Complications:** Accidental vertebral artery injection (seizures), phrenic nerve block (diaphragmatic palsy), and recurrent laryngeal nerve block (hoarseness).

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

Practice Questions

Complications of Regional Anesthesia

Practice Questions

Regional Anesthesia in Pediatric Patients

Practice Questions

Regional Anesthesia in Obstetrics

Practice Questions

Continuous Peripheral Nerve Catheters

Practice Questions

Want unlimited practice?

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

Start For Free