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?
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.
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