Regional Anesthesia — MCQs

Regional Anesthesia Indian Medical PG Practice Questions and MCQs

Question 111: What is the extra-oral landmark for the Gowgates technique of mandibular nerve block?

A. Corner of the mouth
B. Intertragic notch
C. Both of the above (Correct Answer)
D. None of the above

Explanation: The **Gow-Gates technique** is a "true" mandibular nerve block because it anesthetizes the mandibular nerve (V3) near its exit from the foramen ovale, before it branches. This results in a wider area of anesthesia compared to the traditional Inferior Alveolar Nerve Block (IANB). ### **Explanation of the Correct Answer** The technique relies on a specific line of sight using both intra-oral and extra-oral landmarks to ensure the needle reaches the neck of the mandibular condyle. * **Intertragic Notch:** The needle is aimed toward the intertragic notch of the ear on the side being injected. This provides the vertical orientation. * **Corner of the Mouth:** The barrel of the syringe typically rests at the corner of the mouth on the contralateral side (opposite side), while the alignment follows a line from the corner of the mouth to the intertragic notch on the ipsilateral side. Because the technique requires aligning the needle along a plane defined by the **intertragic notch** and the **corner of the mouth**, both are essential extra-oral landmarks. ### **Why Other Options are Incorrect** * **Options A & B:** These are partially correct but incomplete. Selecting only one would ignore the dual-landmark alignment necessary for the high success rate (approx. 95-98%) of this block. ### **High-Yield Clinical Pearls for NEET-PG** * **Target:** The lateral aspect of the neck of the condyle, just below the insertion of the lateral pterygoid muscle. * **Nerves Blocked:** Inferior alveolar, lingual, mylohyoid, mental, incisive, auriculotemporal, and buccal nerves (virtually the entire V3 distribution). * **Advantage:** Lower aspiration rate (1.9%) compared to IANB (10-15%) and higher success rate in patients with accessory innervation. * **Patient Positioning:** The patient must keep their **mouth wide open** during the procedure to bring the condyle into an anterior position.

Question 112: Which route offers the fastest absorption of a local anesthetic?

A. Intercostal (Correct Answer)
B. Epidural
C. Brachial
D. Caudal

Explanation: The rate of absorption of a local anesthetic (LA) into the systemic circulation is primarily determined by the **vascularity** of the injection site. ### Why Intercostal is the Correct Answer The **intercostal space** is highly vascular. When an LA is injected here, it is rapidly absorbed into the systemic circulation due to the dense network of blood vessels. This results in the highest peak plasma concentration ($C_{max}$) of the drug compared to any other regional technique. ### Analysis of Incorrect Options * **Epidural:** While the epidural space contains a rich venous plexus (Batson’s plexus), the absorption rate is slower than the intercostal route because the drug must first diffuse through fatty tissue and the dural cuff. * **Caudal:** This is a form of epidural anesthesia. While vascular, the absorption is generally slower than intercostal and similar to or slightly slower than lumbar epidural. * **Brachial (Plexus):** The brachial plexus is surrounded by a fascial sheath and has lower vascularity compared to the intercostal vessels, leading to slower systemic absorption. ### NEET-PG High-Yield Pearls: "BICEPS" Mnemonic To remember the order of systemic absorption from highest to lowest (fastest to slowest), use the mnemonic **BICEPS**: 1. **B** – Blood (Intravenous/Intra-arterial) – *Fastest* 2. **I** – **Intercostal** 3. **C** – Caudal 4. **E** – Epidural 5. **P** – Plexus (Brachial) 6. **S** – Sciatic/Subcutaneous – *Slowest* **Clinical Note:** Because intercostal blocks have the fastest absorption, they carry the **highest risk of Local Anesthetic Systemic Toxicity (LAST)**. Always aspirate before injecting and monitor for early signs of toxicity (e.g., perioral numbness, metallic taste).

Question 113: In the extraoral technique for a maxillary nerve block, into which anatomical space is the needle directed?

A. Foramen ovale
B. Pterygopalatine fossa (Correct Answer)
C. Stylomastoid foramen
D. Posterior to the lateral pterygoid plate

Explanation: **Explanation:** The **Maxillary Nerve (V2)** is the second division of the trigeminal nerve. After exiting the cranium via the foramen rotundum, it enters the **pterygopalatine fossa**. In the extraoral approach for a maxillary nerve block, the needle is advanced through the sigmoid notch of the mandible and directed superiorly and medially into this fossa to bathe the nerve in local anesthetic before it branches into the infraorbital and palatine nerves. **Analysis of Options:** * **Pterygopalatine Fossa (Correct):** This is the anatomical "hub" where the maxillary nerve resides after leaving the skull. Blocking it here provides complete anesthesia to the maxillary teeth, palate, and mid-face. * **Foramen Ovale:** This is the exit point for the **Mandibular Nerve (V3)**. A block here would affect the lower jaw, not the maxilla. * **Stylomastoid Foramen:** This is the exit point for the **Facial Nerve (CN VII)**. Blocking this would result in facial muscle paralysis (motor) rather than sensory anesthesia of the maxilla. * **Posterior to the lateral pterygoid plate:** This area is associated with the mandibular nerve and the maxillary artery. For a maxillary block, the needle must be directed **anterior** to the pterygoid plates to reach the pterygopalatine fossa. **High-Yield Clinical Pearls:** * **Indications:** Extensive maxillary surgeries, trigeminal neuralgia (V2), or when local infection precludes an intraoral approach. * **Landmark:** The needle passes through the **sigmoid notch** (between the coronoid and condylar processes of the mandible). * **Complication:** The most common complication is a **hematoma** due to the proximity of the pterygoid venous plexus and the maxillary artery.

Question 114: What are the physiological effects of spinal anesthesia primarily due to the blockage of?

A. Sympathetic nerve roots (Correct Answer)
B. Afferent motor nerves
C. Sensory fibres
D. Efferent motor nerves

Explanation: The physiological changes observed during spinal anesthesia—most notably hypotension and bradycardia—are primarily driven by the blockade of the **sympathetic nerve roots** (preganglionic sympathetic fibers). ### Why Sympathetic Nerve Roots is Correct: Spinal anesthesia involves the injection of local anesthetics into the subarachnoid space, which blocks nerve roots as they exit the spinal cord. The sympathetic outflow (T1 to L2) is highly sensitive to local anesthetics. * **Vasodilation:** Blockade of sympathetic fibers causes venous and arterial dilation, leading to a decrease in systemic vascular resistance and venous return (preload), resulting in **hypotension**. * **Bradycardia:** If the block reaches the **T1–T4 levels** (cardioaccelerator fibers), the compensatory tachycardia is lost, leading to profound bradycardia. ### Why Other Options are Incorrect: * **B & D (Motor Nerves):** Blockade of efferent motor nerves causes muscle relaxation (desirable for surgery) and potentially respiratory muscle weakness if the block is too high, but it does not mediate the primary cardiovascular physiological shifts. * **C (Sensory Fibers):** Blockade of sensory fibers (afferent) provides analgesia and anesthesia. While this prevents the surgical stress response, it is not the mechanism behind the systemic physiological changes like hypotension. ### High-Yield Clinical Pearls for NEET-PG: 1. **Order of Blockade:** Autonomic (Sympathetic) > Pain/Temperature (Sensory) > Touch/Pressure > Motor. 2. **Differential Block:** The sympathetic block is typically **2–6 segments higher** than the sensory block, which is in turn 2 segments higher than the motor block. 3. **Bezold-Jarisch Reflex:** This triad of hypotension, bradycardia, and peripheral vasodilation can occur during spinal anesthesia due to decreased ventricular volume. 4. **Treatment of Choice:** For hypotension due to spinal anesthesia, **Phenylephrine** (vasoconstrictor) or **Ephedrine** (if bradycardia is present) are used alongside IV fluids.

Question 115: Which of the following is NOT a sign of stellate ganglion block?

A. Miosis
B. Exophthalmos (Correct Answer)
C. Nasal congestion
D. Conjunctival redness

Explanation: ### Explanation The **Stellate Ganglion Block** involves the injection of local anesthetic into the cervical sympathetic chain (formed by the fusion of the inferior cervical and first thoracic ganglia). The goal is to interrupt sympathetic innervation to the head, neck, and upper extremities. #### Why Exophthalmos is the Correct Answer: A successful stellate ganglion block results in **Horner’s Syndrome** due to the paralysis of sympathetic fibers. Horner’s Syndrome is characterized by the classic triad of Miosis, Ptosis, and **Enophthalmos** (the backward displacement of the eyeball). **Exophthalmos** (protrusion of the eyeball) is the opposite of what occurs and is typically seen in conditions like hyperthyroidism (Graves' disease). #### Analysis of Incorrect Options: * **Miosis (A):** Sympathetic fibers normally cause pupillary dilation (mydriasis). Blocking them leads to pupillary constriction (miosis) due to unopposed parasympathetic action. * **Nasal Congestion (C):** Sympathetic nerves cause vasoconstriction in the nasal mucosa. A block leads to vasodilation, resulting in nasal stuffiness (known as **Guttman’s sign**). * **Conjunctival Redness (D):** The loss of sympathetic tone causes vasodilation of the blood vessels in the conjunctiva, leading to redness/injection. --- ### High-Yield Clinical Pearls for NEET-PG: * **Horner’s Syndrome Components:** Miosis, Partial Ptosis, Enophthalmos, and **Anhidrosis** (lack of sweating) on the ipsilateral side of the face. * **Anatomical Landmark:** The block is performed at the level of the **C6 transverse process (Chassaignac’s tubercle)** to avoid the pleura, which is higher at C7. * **Indications:** Complex Regional Pain Syndrome (CRPS) Type I & II of the upper limb, Raynaud’s disease, and refractory cardiac arrhythmias. * **Complication to Watch:** Accidental vertebral artery injection (can cause immediate seizures) or phrenic nerve block (causing hemidiaphragmatic paralysis).

Question 116: Increased risk of cardiotoxicity associated with local anesthetics requires a dose reduction in all of the following, except:

A. Pregnancy
B. Acidosis
C. Pediatric patients
D. Increased cardiac output (Correct Answer)

Explanation: Local anesthetic (LA) toxicity is primarily determined by the concentration of the free drug in the plasma. Factors that increase the sensitivity of cardiac tissue or accelerate the systemic absorption of the drug necessitate a dose reduction. **Explanation of the Correct Option:** **D. Increased cardiac output:** This is the correct answer because an increase in cardiac output actually **decreases** the risk of systemic toxicity. Higher cardiac output leads to a more rapid redistribution of the local anesthetic from the central compartment (blood/heart/brain) to peripheral tissues (muscle/fat), thereby lowering the peak plasma concentration. Conversely, low cardiac output states (like heart failure) slow redistribution and increase toxicity risk. **Why the other options are incorrect (Factors requiring dose reduction):** * **Pregnancy:** Hormonal changes (progesterone) increase the sensitivity of neural and cardiac tissues to LAs. Additionally, mechanical factors like IVC compression lead to engorgement of epidural veins, reducing the effective volume of the space and increasing the risk of accidental intravascular injection. * **Acidosis:** Hypercapnia and acidosis decrease the seizure threshold and increase the fraction of the free (unbound) drug. Acidosis also promotes "ion trapping" within cardiac cells, worsening cardiotoxicity. * **Pediatric patients:** Children have lower levels of alpha-1 acid glycoprotein (the primary binding protein for LAs), leading to higher levels of free drug. They also have higher weight-based cardiac output, which can lead to faster systemic absorption from the injection site. **High-Yield NEET-PG Pearls:** 1. **Bupivacaine** is the most cardiotoxic LA due to its "fast-in, slow-out" kinetics at cardiac sodium channels. 2. **Lipid Emulsion (20% Intralipid)** is the specific antidote for systemic LA toxicity (LAST). 3. **Order of Toxicity:** CNS symptoms (tinnitus, metallic taste, seizures) usually precede Cardiac symptoms (arrhythmias, arrest), except with Bupivacaine where they may occur simultaneously.

Question 117: What is the recommended dose of local anesthesia for spinal anesthesia?

A. Lignocaine - 1%
B. Lignocaine - 2.5%
C. Lignocaine - 5% (Correct Answer)
D. Bupivacaine - 0.5%

Explanation: **Explanation:** In spinal anesthesia (subarachnoid block), the goal is to achieve a dense sensory and motor block using a small volume of a high-concentration local anesthetic. **Why Lignocaine 5% is the correct answer:** Historically, **5% Hyperbaric Lignocaine** (Lignocaine 5% in 7.5% Dextrose) was the standard preparation for spinal anesthesia. It provides a rapid onset and a predictable duration of action (approx. 60–90 minutes). While its use has declined in some regions due to the risk of Transient Neurological Symptoms (TNS), it remains the classic textbook answer for the "recommended dose/concentration" of Lignocaine in spinal anesthesia for exam purposes. **Analysis of Incorrect Options:** * **Lignocaine 1% & 2%:** These concentrations are primarily used for **local infiltration**, field blocks, or intravenous regional anesthesia (Bier's block). They do not provide the necessary baricity or potency required for a reliable spinal block in standard small volumes. * **Bupivacaine 0.5%:** While 0.5% Bupivacaine (Heavy) is currently the **most commonly used** drug for spinal anesthesia in clinical practice due to its longer duration and lower neurotoxicity, the question specifically asks for the recommended concentration of Lignocaine. If the question asked for the "drug of choice" today, Bupivacaine 0.5% would be the answer. **High-Yield Clinical Pearls for NEET-PG:** * **Hyperbaric solutions:** Created by adding **Dextrose**. This makes the drug heavier than CSF, allowing the clinician to control the level of the block via patient positioning. * **Transient Neurological Symptoms (TNS):** Most commonly associated with **Lignocaine 5%**. It presents as back pain radiating to the buttocks/legs after recovery. * **Specific Gravity of CSF:** 1.003–1.008. * **Order of Nerve Block:** B-fibers (Autonomic) > A-delta & C-fibers (Pain/Temp) > A-gamma (Muscle spindle) > A-beta (Touch/Pressure) > A-alpha (Motor).

Question 118: Systemic toxicity is more common with which type of regional anesthesia?

A. Spinal anesthesia
B. Epidural anesthesia (Correct Answer)
C. Both spinal and epidural anesthesia
D. Neither spinal nor epidural anesthesia

Explanation: **Explanation:** The primary factor determining **Local Anesthetic Systemic Toxicity (LAST)** is the total dose (mass) of the drug administered and the vascularity of the site. **Why Epidural Anesthesia is the correct answer:** Epidural anesthesia requires a significantly **higher volume and concentration** of local anesthetic (e.g., 15–20 mL) compared to spinal anesthesia (e.g., 2–3 mL) to achieve an adequate block. Furthermore, the epidural space contains an extensive network of **Batson’s venous plexuses**. The combination of a large drug mass and high vascularity increases the risk of accidental intravascular injection or rapid systemic absorption, leading to toxicity. **Why other options are incorrect:** * **Spinal Anesthesia:** This involves injecting a very small dose of drug directly into the subarachnoid space. The total drug mass is too low to cause systemic toxicity, even if it were absorbed into the bloodstream. The primary risk here is "Total Spinal" (respiratory arrest due to high block), not systemic toxicity. * **Both/Neither:** These are incorrect because the risk profile is distinctly different between the two techniques based on the pharmacological dose used. **High-Yield Clinical Pearls for NEET-PG:** * **Order of Systemic Absorption (Highest to Lowest):** Intravenous > Tracheal > Intercostal > Caudal > Epidural > Brachial Plexus > Sciatic/Femoral > Subcutaneous. (Mnemonic: **I** **T**hink **I** **C**an **E**at **B**ig **S**ubway **S**andwiches). * **Early signs of LAST:** Perioral numbness, metallic taste, tinnitus, and lightheadedness. * **Management:** The antidote of choice for LAST is **20% Lipid Emulsion (Intralipid).** * **Bupivacaine** is the most cardiotoxic local anesthetic.

Question 119: In general, which is the last muscle to be rendered akinetic with a retrobulbar anesthetic block?

A. Superior rectus
B. Superior oblique (Correct Answer)
C. Inferior oblique
D. Levator palpebrae superioris

Explanation: **Explanation:** The goal of a retrobulbar block is to achieve anesthesia and akinesia of the globe by injecting local anesthetic into the muscle cone. The **Superior Oblique** is typically the last muscle to be rendered akinetic because of its unique anatomical position. **Why Superior Oblique is the correct answer:** The retrobulbar block targets the nerves within the retrobulbar cone (ciliary nerves and Cranial Nerves III and VI). However, the **Trochlear nerve (CN IV)**, which supplies the Superior Oblique, is the only motor nerve to the extraocular muscles that remains **outside the muscle cone**. Because the local anesthetic must diffuse from the intraconal space to the extraconal space to reach CN IV, the Superior Oblique is the last to be paralyzed. **Analysis of Incorrect Options:** * **Superior Rectus & Inferior Oblique:** These are supplied by the Superior and Inferior divisions of the Oculomotor nerve (CN III), respectively. Since CN III enters the orbit through the tendinous ring *inside* the muscle cone, these muscles are blocked rapidly. * **Levator palpebrae superioris:** Also supplied by the Superior division of CN III within the cone. While it is responsible for ptosis after a block, it is not the last muscle affected. **High-Yield Clinical Pearls for NEET-PG:** * **The "Classic" Retrobulbar Block:** Provides excellent anesthesia and akinesia but carries risks like retrobulbar hemorrhage or optic nerve injury. * **Nerves outside the cone:** Trochlear (IV), Lacrimal, Frontal, and Nasociliary (though Nasociliary eventually enters). * **Safety Note:** If a patient can still look "down and in" after a block, the Superior Oblique (CN IV) is still functioning. * **Alternative:** Peribulbar blocks are safer as the needle remains extraconal, though they require a larger volume of anesthetic and have a slower onset.

Question 120: What is the concentration of Xylocaine heavy in the subarachnoid space?

A. 1%
B. 2%
C. 3%
D. 5% (Correct Answer)

Explanation: **Explanation:** The correct answer is **5% (Option D)**. In spinal anesthesia (subarachnoid block), the baricity of the local anesthetic determines its spread within the cerebrospinal fluid (CSF). **Xylocaine Heavy** (Lignocaine/Lidocaine) is formulated as a **5% concentration** mixed with **7.5% Dextrose**. The addition of dextrose increases the specific gravity of the solution (making it "heavy" or hyperbaric) relative to the CSF (specific gravity ~1.003–1.008). This allows the clinician to control the level of the block using gravity by tilting the patient. **Analysis of Options:** * **A (1%):** This concentration is commonly used for local infiltration or minor nerve blocks, but it is too dilute for a standard hyperbaric spinal block. * **B (2%):** This is the standard concentration for **Epidural Anesthesia** and peripheral nerve blocks. It provides excellent sensory and motor blockade in the epidural space but is not the standard "heavy" preparation for spinal use. * **C (3%):** This is not a standard commercial concentration for Xylocaine in regional anesthesia. * **D (5%):** This is the gold-standard concentration for hyperbaric Lignocaine used in the subarachnoid space. **High-Yield Clinical Pearls for NEET-PG:** * **Transient Neurological Symptoms (TNS):** 5% Lignocaine has fallen out of favor in many centers due to a high incidence of TNS (radicular pain/dysesthesia post-operatively), especially when used for spinal anesthesia in the lithotomy position. * **Bupivacaine (Sensorcaine/Marcaine):** Currently the most common drug for spinal anesthesia, used as a **0.5% heavy** solution (with 8% dextrose). * **Specific Gravity:** Hyperbaric solutions have a specific gravity >1.008; Isobaric = 1.008; Hypobaric < 1.008. * **Lignocaine Metabolism:** It is an amide-linked local anesthetic metabolized in the liver by cytochrome P450 enzymes.

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