Regional Anesthesia — MCQs
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In the Gow-Gates technique, what is the target area?
Intravenous regional anaesthesia is contraindicated in which of the following conditions?
What is the duration of action of lidocaine with adrenaline?
Which of the following is NOT true about cocaine?
Which of the following is not a sign of successful stellate ganglion block?
All of the following are true regarding superior laryngeal nerve block, except:
What is the best method to prevent hypotension during spinal anesthesia?
What is the recommended maximum dose of Lignocaine with adrenaline for peripheral nerve block?
A patient in the ICU was on invasive monitoring with intra-arterial cannulation through the right radial artery for the last 3 days. The patient later developed swelling and discoloration of the right hand. What is the next line of management?
In spinal anesthesia, which nerve fibers are affected earliest?
Regional Anesthesia Indian Medical PG Practice Questions and MCQs
Question 1: In the Gow-Gates technique, what is the target area?
- A. Neck of the condyle (Correct Answer)
- B. Head of the condyle
- C. Medial side of the ramus
- D. Lateral side of the condyle
Explanation: ### Explanation The **Gow-Gates technique** is a true mandibular nerve block that anesthetizes almost the entire distribution of the mandibular nerve (V3). **1. Why the Correct Answer is Right:** The target area for the Gow-Gates technique is the **lateral aspect of the neck of the condyle**, just below the insertion of the external pterygoid muscle. By depositing local anesthetic at this high point, the clinician targets the mandibular nerve trunk before it branches into the inferior alveolar, lingual, and buccal nerves. This results in a higher success rate (approx. 95%) compared to the traditional Inferior Alveolar Nerve Block (IANB). **2. Why Incorrect Options are Wrong:** * **Head of the condyle:** This is too superior. Aiming for the head increases the risk of entering the temporomandibular joint (TMJ) capsule or causing trauma to the articular disc. * **Medial side of the ramus:** This is the target for the **traditional Inferior Alveolar Nerve Block (IANB)** at the level of the mandibular foramen. * **Lateral side of the condyle:** While the target is on the lateral aspect of the *neck*, "lateral side of the condyle" usually refers to the bony prominence of the head, which is not the specific site for deposition. **3. High-Yield Clinical Pearls for NEET-PG:** * **Nerves Blocked:** Inferior alveolar, lingual, mylohyoid, mental, incisive, auriculotemporal, and buccal nerves. * **Landmarks:** The needle is aimed toward the **intertragic notch** of the ear, with the barrel of the syringe usually resting on the contralateral mandibular premolars. * **Advantage:** Lower aspiration rate (1.9%) compared to IANB (10-15%) and successful anesthesia in cases of accessory innervation (e.g., bifid inferior alveolar nerve). * **Disadvantage:** Slower onset of action (5-7 minutes) due to the larger diameter of the nerve trunk at this level.
Question 2: Intravenous regional anaesthesia is contraindicated in which of the following conditions?
- A. Sickle cell disease (Correct Answer)
- B. Thalassemia
- C. Hereditary spherocytosis
- D. G6PD deficiency
Explanation: **Explanation:** **Intravenous Regional Anesthesia (IVRA)**, also known as a **Bier Block**, involves the use of a pneumatic tourniquet to isolate a limb from systemic circulation while injecting local anesthetic (usually Lidocaine) intravenously. **Why Sickle Cell Disease (SCD) is the Correct Answer:** The primary contraindication for IVRA in patients with Sickle Cell Disease is the mandatory use of a **tourniquet**. The tourniquet induces: 1. **Stasis:** Slowing of blood flow. 2. **Hypoxia and Acidosis:** Due to tissue ischemia distal to the cuff. These conditions are the classic triggers for **sickling of red blood cells**. Massive sickling within the limb can lead to microvascular occlusion, severe tissue ischemia, and potentially a systemic sickle cell crisis upon tourniquet release. **Why the Other Options are Incorrect:** * **Thalassemia (B):** This is a quantitative defect in hemoglobin synthesis. While patients may be anemic, their RBCs do not sickle in response to stasis or hypoxia, making IVRA relatively safe. * **Hereditary Spherocytosis (C):** This is a membrane defect causing spherical RBCs. While these cells are prone to hemolysis in the spleen, they do not pose an immediate risk of vaso-occlusion under tourniquet-induced hypoxia. * **G6PD Deficiency (D):** This is an enzyme defect making cells sensitive to oxidative stress. IVRA does not typically trigger hemolysis in these patients unless oxidative drugs (like Prilocaine, which can cause methemoglobinemia) are used, but it is not an absolute contraindication like SCD. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for IVRA:** 0.5% Lidocaine (Preservative-free). * **Drug to Avoid:** Bupivacaine (high risk of cardiotoxicity if the tourniquet fails). * **Tourniquet Time:** Minimum 20 minutes (to prevent toxic bolus) and maximum 90 minutes. * **Other Contraindications:** Raynaud’s disease, Buerger’s disease, severe peripheral vascular disease, and local skin infections.
Question 3: What is the duration of action of lidocaine with adrenaline?
- A. 15-30 minutes
- B. 30-60 minutes
- C. 2-3 hours (Correct Answer)
- D. 3-6 hours
Explanation: **Explanation:** Lidocaine is an intermediate-acting amide local anesthetic. Its duration of action is primarily determined by its lipid solubility and the rate of vascular absorption from the site of injection. **1. Why Option C is Correct:** Plain lidocaine typically provides anesthesia for **30–60 minutes**. However, the addition of **adrenaline (epinephrine)**, usually in a concentration of 1:200,000, causes local vasoconstriction. This reduces the rate of systemic absorption, allowing the drug to remain at the nerve membrane for a longer period. This effectively doubles or triples the duration of action, extending it to approximately **120–180 minutes (2–3 hours)**. **2. Why Other Options are Incorrect:** * **Option A (15-30 mins):** This is too short for lidocaine and may represent the duration of ultra-short-acting agents or very low concentrations used for infiltration. * **Option B (30-60 mins):** This is the duration of **plain lidocaine** without a vasoconstrictor. * **Option D (3-6 hours):** This duration is characteristic of long-acting amide anesthetics like **Bupivacaine or Ropivacaine**. **3. NEET-PG High-Yield Pearls:** * **Maximum Dose:** Plain Lidocaine = **3 mg/kg**; Lidocaine with Adrenaline = **7 mg/kg**. * **Adrenaline Benefits:** It increases the duration of block, decreases systemic toxicity (by slowing absorption), and provides a bloodless surgical field. * **Contraindication:** Adrenaline-containing local anesthetics must **never** be used in areas supplied by end-arteries (e.g., fingers, toes, penis, nose, pinna) due to the risk of ischemia and gangrene. * **Mechanism:** Local anesthetics work by blocking **voltage-gated sodium channels** in the inactivated state.
Question 4: Which of the following is NOT true about cocaine?
- A. It is an amide local anesthetic. (Correct Answer)
- B. It can produce sympathetic stimulation.
- C. It is metabolized by the liver.
- D. It blocks the presynaptic uptake of norepinephrine and dopamine.
Explanation: **Explanation:** **1. Why Option A is the Correct Answer (The "NOT" True Statement):** Local anesthetics are classified into two groups: **Esters** and **Amides**. Cocaine is an **ester-linked** local anesthetic, not an amide. A simple mnemonic to distinguish them is that amide local anesthetics (like Lidocaine, Bupivacaine, Prilocaine) always contain the letter **"i"** twice in their name (e.g., L**i**doca**i**ne), whereas esters (Cocaine, Procaine, Tetracaine) contain it only once. **2. Analysis of Other Options:** * **Option B & D:** Cocaine is unique among local anesthetics because it is a potent **inhibitor of the presynaptic reuptake** of catecholamines (Norepinephrine and Dopamine). This leads to an accumulation of these neurotransmitters in the synaptic cleft, resulting in intense **sympathetic stimulation** (tachycardia, hypertension, and mydriasis). * **Option C:** While most esters are primarily metabolized by plasma pseudocholinesterase, Cocaine is unique as it undergoes significant metabolism by **liver carboxylesterases** in addition to plasma cholinesterase. **Clinical Pearls for NEET-PG:** * **Vasoconstriction:** Cocaine is the **only** local anesthetic that naturally causes vasoconstriction; all others (except ropivacaine/levobupivacaine at low doses) are vasodilators. * **Clinical Use:** Due to its vasoconstrictive and anesthetic properties, it is used topically in ENT surgeries (e.g., dacryocystorhinostomy) to reduce bleeding. * **Toxicity:** Overdose causes CNS stimulation followed by seizures and fatal cardiac arrhythmias. **Beta-blockers are contraindicated** in cocaine toxicity as they lead to unopposed alpha-adrenergic stimulation.
Question 5: Which of the following is not a sign of successful stellate ganglion block?
- A. Nasal stuffness
- B. Guttman sign
- C. Horner's syndrome
- D. Bradycardia (Correct Answer)
Explanation: The **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), located anterior to the transverse process of the C7 vertebra. It is primarily used to treat sympathetically mediated pain in the upper extremities and head. ### **Explanation of Options** * **Why Bradycardia is the Correct Answer:** The stellate ganglion provides sympathetic innervation to the upper limb and face, but **cardiac sympathetic fibers** (which increase heart rate) primarily arise from the **T1-T4 thoracic sympathetic chain**. While a block can theoretically involve these fibers, **Bradycardia** is not a standard or reliable sign of a successful SGB. In fact, if the block is performed correctly at the C6/C7 level, significant hemodynamic changes like bradycardia are rare. * **Why the other options are signs of success:** * **Horner’s Syndrome (Option C):** This is the classic "gold standard" sign of a successful block. It consists of the triad of **Miosis** (constricted pupil), **Ptosis** (drooping eyelid), and **Anhidrosis** (lack of sweating) on the ipsilateral side. * **Nasal Stuffiness (Option A):** Also known as **Gutzmer’s sign**, this occurs due to vasodilation of the nasal mucosa following sympathetic blockade. * **Guttman Sign (Option B):** This refers to the **absence of sweating** (anhidrosis) in the red area of the face/neck, confirming the interruption of sympathetic sudomotor fibers. ### **High-Yield Clinical Pearls for NEET-PG** * **Chassaignac’s Tubercle:** The block is traditionally performed at the level of the **C6 transverse process** (easiest to palpate) to avoid the vertebral artery and lung pleura, though the ganglion itself lies at C7. * **Complications:** The most common "side effect" is **Hoarseness** (due to Recurrent Laryngeal Nerve block). The most feared complication is **Intra-arterial injection** into the vertebral artery, leading to immediate seizures. * **Other signs:** Conjunctival injection (bloodshot eye) and increased skin temperature of the ipsilateral arm.
Question 6: All of the following are true regarding superior laryngeal nerve block, except:
- A. Needle pierces through the thyrohyoid membrane.
- B. Sensory loss below the level of the vocal cords occurs. (Correct Answer)
- C. The internal laryngeal nerve is anesthetized.
- D. The thyroid notch is used as a landmark.
Explanation: To master airway anesthesia, it is crucial to understand the sensory innervation of the larynx, which is divided into two zones by the vocal cords. ### **Explanation of the Correct Answer** **Option B is the correct answer (the false statement)** because the Superior Laryngeal Nerve (SLN) provides sensory innervation only to the laryngeal mucosa **above** the level of the vocal cords. Sensory innervation **below** the level of the vocal cords is provided by the **Recurrent Laryngeal Nerve (RLN)**. Therefore, an SLN block will not result in sensory loss below the cords. ### **Analysis of Other Options** * **Option A & D:** To perform the block, the **thyroid notch** is palpated, and the needle is walked off the greater cornu of the hyoid bone to pierce the **thyrohyoid membrane**. This is the anatomical site where the nerve enters the larynx. * **Option C:** The SLN divides into internal and external branches. The **internal laryngeal nerve** is the specific branch that pierces the thyrohyoid membrane to provide sensation to the supraglottic region; thus, it is the primary target of this block. ### **High-Yield Clinical Pearls for NEET-PG** * **Sensory Innervation Summary:** * **Above Vocal Cords:** Internal Laryngeal Nerve (branch of SLN). * **Below Vocal Cords:** Recurrent Laryngeal Nerve. * **Motor Innervation:** All intrinsic muscles of the larynx are supplied by the **RLN**, *except* the **Cricothyroid muscle**, which is supplied by the **External Laryngeal Nerve** (branch of SLN). * **Glossopharyngeal Nerve (CN IX):** Provides sensory innervation to the posterior third of the tongue, vallecula, and the anterior surface of the epiglottis (the "gag reflex" afferent). * **Clinical Use:** The SLN block is frequently used for **awake fiberoptic intubation** to abolish the swallowing reflex.
Question 7: What is the best method to prevent hypotension during spinal anesthesia?
- A. Preloading with crystalloids (Correct Answer)
- B. Mephentermine
- C. Dopamine
- D. Trendelenburg position
Explanation: **Explanation:** Spinal anesthesia induces a rapid **sympathetic blockade**, leading to venous and arterial vasodilation. This results in venous pooling, decreased venous return (preload), and a subsequent drop in cardiac output, manifesting as hypotension. **Why Preloading is the Best Preventive Method:** The primary goal in preventing spinal-induced hypotension is to optimize intravascular volume before the blockade occurs. **Preloading with crystalloids** (typically 10–20 ml/kg of Ringer’s Lactate) increases the effective circulating volume, compensating for the expanded vascular capacity caused by vasodilation. While "co-loading" (administering fluids rapidly at the time of injection) is also widely practiced, preloading remains the classic foundational step in anesthetic management to maintain hemodynamic stability. **Analysis of Incorrect Options:** * **B & C (Mephentermine/Dopamine):** These are **vasopressors** used for the *treatment* of hypotension once it occurs. While effective as rescue drugs, they are generally not the first-line "preventative" method compared to fluid optimization. * **D (Trendelenburg Position):** While head-down positioning can increase venous return, it is risky during the initial stages of spinal anesthesia as it may cause the local anesthetic (if hyperbaric) to cephalad, leading to a **high spinal** and respiratory paralysis. **High-Yield Clinical Pearls for NEET-PG:** * **Fluid of Choice:** Ringer’s Lactate is preferred over Normal Saline to avoid hyperchloremic metabolic acidosis. * **Vasopressor of Choice:** **Phenylephrine** is currently considered the gold standard for managing spinal-induced hypotension (especially in obstetric anesthesia) because it causes less fetal acidosis compared to Ephedrine. * **Bezold-Jarisch Reflex:** This triad of hypotension, bradycardia, and cardiovascular collapse can occur during spinal anesthesia due to decreased ventricular volume.
Question 8: What is the recommended maximum dose of Lignocaine with adrenaline for peripheral nerve block?
- A. 7 mg/kg body weight (Correct Answer)
- B. 4.5 mg/kg body weight
- C. 2 mg/kg body weight
- D. 3 mg/kg body weight
Explanation: **Explanation:** The maximum recommended dose of local anesthetics is determined by the risk of **Local Anesthetic Systemic Toxicity (LAST)**. Lignocaine (Lidocaine) is an amide-linked local anesthetic that acts by blocking voltage-gated sodium channels. **Why 7 mg/kg is correct:** When Lignocaine is administered with **Adrenaline (Epinephrine)**, the vasoconstrictive properties of adrenaline decrease the rate of systemic absorption from the injection site. This slower absorption allows for a higher safe dose to be administered, extending the limit to **7 mg/kg**. Without adrenaline (plain Lignocaine), the maximum dose is lower (**4.5 mg/kg**) because the drug enters the bloodstream more rapidly. **Analysis of Incorrect Options:** * **Option B (4.5 mg/kg):** This is the maximum recommended dose for **plain Lignocaine** (without adrenaline). * **Option C (2 mg/kg):** This is the approximate maximum dose for **Bupivacaine** (plain), which is significantly more potent and cardiotoxic than Lignocaine. * **Option D (3 mg/kg):** This is the maximum dose for **Bupivacaine with adrenaline** (though some texts cite up to 2.5–3 mg/kg). **High-Yield Clinical Pearls for NEET-PG:** * **Adrenaline Concentration:** Usually added in a **1:200,000** concentration (5 µg/mL). * **Toxic Symptoms:** Initial signs of toxicity include perioral numbness, metallic taste, and tinnitus, progressing to seizures and cardiovascular collapse. * **Antidote for LAST:** Intravenous **20% Lipid Emulsion (Intralipid)** is the specific treatment for systemic toxicity. * **Maximum Absolute Dose:** Regardless of weight, the total dose of Lignocaine with adrenaline should generally not exceed **500 mg** in an adult.
Question 9: A patient in the ICU was on invasive monitoring with intra-arterial cannulation through the right radial artery for the last 3 days. The patient later developed swelling and discoloration of the right hand. What is the next line of management?
- A. Stellate ganglion block (Correct Answer)
- B. Brachial block
- C. Radial nerve block
- D. Celiac plexus block
Explanation: ### Explanation **Correct Answer: A. Stellate ganglion block** **Why it is correct:** The clinical presentation of swelling and discoloration following prolonged intra-arterial cannulation suggests **accidental intra-arterial injection or arterial vasospasm/thrombosis**, leading to acute limb ischemia. The **Stellate Ganglion Block (SGB)** is the treatment of choice because it interrupts the sympathetic supply to the upper extremity (C7-T1). By blocking the sympathetic chain, it causes **vasodilation**, increases collateral blood flow, and relieves pain, thereby potentially salvaging the ischemic limb. **Why incorrect options are wrong:** * **B. Brachial block:** While it can provide some sympathetic blockade, its primary purpose is sensory and motor anesthesia for surgery. It is not the gold standard for treating acute sympathetic-mediated ischemia. * **C. Radial nerve block:** This is a peripheral nerve block providing only sensory/motor coverage to a specific distribution. it has no effect on the global sympathetic outflow to the hand. * **D. Celiac plexus block:** This is used for managing chronic abdominal pain (e.g., pancreatic cancer) and has no anatomical relevance to the upper limb. **High-Yield Clinical Pearls for NEET-PG:** * **Anatomy:** The Stellate ganglion is formed by the fusion of the **inferior cervical and first thoracic ganglion**. It is located anterior to the transverse process of **C7**. * **Horner’s Syndrome:** A successful SGB is confirmed by the presence of Horner’s syndrome (Ptosis, Miosis, Anhydrosis, Enophthalmos, and Conjunctival congestion). * **Indications:** Apart from arterial insufficiency, SGB is used for Complex Regional Pain Syndrome (CRPS) Type I & II, Raynaud’s disease, and refractory ventricular arrhythmias. * **Complication:** Accidental vertebral artery injection (leading to seizures) is a feared complication.
Question 10: In spinal anesthesia, which nerve fibers are affected earliest?
- A. Sensory fibers
- B. Motor fibers
- C. Sympathetic preganglionic fibers (Correct Answer)
- D. Vibration sense fibers
Explanation: In spinal anesthesia, the sequence of blockade is determined by the diameter of the nerve fibers and their degree of myelination. **Why Sympathetic Preganglionic Fibers are correct:** The sensitivity of nerve fibers to local anesthetics is generally inversely proportional to their diameter. **Sympathetic preganglionic fibers (B-fibers)** are small, lightly myelinated fibers. Due to their small size and high surface-area-to-volume ratio, they are the most sensitive to local anesthetic penetration and are blocked first. This explains why hypotension (due to vasodilation) is often the earliest clinical sign of a successful spinal block. **Analysis of Incorrect Options:** * **Sensory fibers (A):** These include **A-delta** (fast pain/temperature) and **C-fibers** (slow pain). While C-fibers are small, B-fibers are blocked even earlier. Sensory loss occurs after sympathetic blockade but before motor loss. * **Motor fibers (B):** These are **A-alpha** fibers. They are large, heavily myelinated, and the most resistant to local anesthetics, making them the last to be blocked and the first to recover. * **Vibration sense fibers (D):** These are **A-beta** fibers (large, myelinated). They are blocked after sympathetic and pain fibers but before motor fibers. **High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Blockade:** Sympathetic (B) > Pain/Temperature (A-delta, C) > Touch/Pressure (A-beta) > Motor (A-alpha). * **Differential Block:** The level of sympathetic block is typically **2 to 6 segments higher** than the sensory block, which is in turn **2 segments higher** than the motor block. * **Recovery Sequence:** The order of recovery is the exact reverse of the blockade (Motor recovers first, Sympathetic last).
Practice by Chapter
Neuraxial Anatomy
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Spinal Anesthesia
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Epidural Anesthesia
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Combined Spinal-Epidural Anesthesia
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Peripheral Nerve Blocks: Upper Extremity
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Peripheral Nerve Blocks: Lower Extremity
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Truncal Blocks
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Ultrasound-Guided Regional Anesthesia
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Complications of Regional Anesthesia
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Regional Anesthesia in Pediatric Patients
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Regional Anesthesia in Obstetrics
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Continuous Peripheral Nerve Catheters
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