Regional Anesthesia — MCQs

Regional Anesthesia Indian Medical PG Practice Questions and MCQs

Question 51: A 70-kg woman is to undergo nail removal from her right ring finger in the ambulatory surgery clinic. Which of the following is the most appropriate option for local anesthesia?

A. Digital block with 1% lidocaine without epinephrine, maximum dose 4.5 mg/kg (Correct Answer)
B. Digital block with 1% lidocaine with epinephrine, maximum dose 4.5 mg/kg
C. Digital block with 1% lidocaine with epinephrine, maximum dose 7 mg/kg
D. Local injection around the nail bed with 1% lidocaine with epinephrine, maximum dose 4.5 mg/kg

Explanation: ### Explanation **1. Why Option A is Correct:** The primary principle in digital anesthesia is the avoidance of vasoconstrictors. The fingers are supplied by **terminal end-arteries**. Using a local anesthetic with epinephrine can cause prolonged vasoconstriction, leading to ischemia, tissue necrosis, and gangrene of the digit. Therefore, **plain lidocaine (without epinephrine)** is the gold standard for digital blocks. The maximum safe dose for plain lidocaine is **4.5 mg/kg** (for this 70-kg patient, the limit would be 315 mg). **2. Why the Other Options are Incorrect:** * **Options B & C:** These include **epinephrine**. While epinephrine is used in other areas to prolong the duration of action and reduce systemic absorption, it is traditionally contraindicated in "end-organ" appendages (fingers, toes, tip of the nose, ears, and penis) due to the risk of ischemic necrosis. Additionally, the 7 mg/kg dose in Option C is the limit for lidocaine *with* epinephrine, which is inapplicable here. * **Option D:** Local infiltration around the nail bed is often more painful and less effective than a **digital block** at the base of the finger, which provides complete anesthesia to the entire digit by targeting the dorsal and palmar digital nerves. Furthermore, it incorrectly includes epinephrine. **3. Clinical Pearls for NEET-PG:** * **Maximum Doses of Lidocaine:** Plain = 4.5 mg/kg (up to 300 mg); With Epinephrine = 7 mg/kg (up to 500 mg). * **Bupivacaine Doses:** Plain = 2 mg/kg; With Epinephrine = 3 mg/kg. * **Digital Block Technique:** The anesthetic is injected at the base of the proximal phalanx. Avoid high volumes of fluid in the digit to prevent "compartment-like" pressure that can compromise blood flow. * **Toxicity:** Early signs of Local Anesthetic Systemic Toxicity (LAST) include perioral numbness, metallic taste, and tinnitus. Management involves **20% Lipid Emulsion**.

Question 52: The duration of spinal anaesthesia depends on all of the following EXCEPT:

A. The specific local anaesthetic used
B. The concentration of the local anaesthetic used
C. The patient's posture (Correct Answer)
D. Whether adrenaline has been added to the local anaesthetic

Explanation: **Explanation:** The duration of spinal anesthesia is primarily determined by the **pharmacokinetics of the drug** within the subarachnoid space—specifically, how long the local anesthetic remains in contact with nerve roots before being absorbed into the systemic circulation. **Why "Patient Posture" is the correct answer:** Patient positioning (e.g., sitting vs. Trendelenburg) significantly affects the **distribution and level (height)** of the block, especially when using hyperbaric or hypobaric solutions. However, once the drug has "fixed" to the nerve tissues (usually within 10–20 minutes), the posture does not influence how long the drug lasts. Duration is a function of elimination, not initial spread. **Analysis of other options:** * **Specific Local Anesthetic (A):** This is the most important determinant. Short-acting drugs like Lidocaine have a shorter duration than long-acting drugs like Bupivacaine or Ropivacaine due to differences in protein binding. * **Concentration/Total Dose (B):** While the volume affects spread, the total mass (concentration × volume) of the drug influences the density and duration of the block. Higher doses generally lead to a longer clinical effect. * **Addition of Adrenaline (D):** Adrenaline acts as a vasoconstrictor, reducing spinal cord blood flow and slowing the systemic absorption of the local anesthetic. This significantly prolongs the duration of the block. **High-Yield Clinical Pearls for NEET-PG:** * **Baricity:** The most important factor for the **level/height** of the block. * **Drug Lipid Solubility:** Determines the **potency** of the local anesthetic. * **Protein Binding:** Determines the **duration of action**. * **Additives:** Opioids (Fentanyl/Morphine), Alpha-2 agonists (Dexmedetomidine), and Epinephrine are commonly used to prolong spinal anesthesia.

Question 53: What is the recommended concentration of local anesthetic agent for Bier's block?

A. 0.50% (Correct Answer)
B. 1-2%
C. 4%
D. 5%

Explanation: **Explanation:** **Bier’s Block**, also known as Intravenous Regional Anesthesia (IVRA), involves the injection of a local anesthetic into the venous system of an extremity isolated from the systemic circulation by a double-pneumatic tourniquet. **1. Why 0.5% is the Correct Answer:** The primary goal in Bier’s block is to provide adequate surgical anesthesia while minimizing the risk of **Systemic Local Anesthetic Toxicity (LAST)** should the tourniquet fail or be released prematurely. * **Lignocaine (Preservative-free)** is the drug of choice. * The recommended concentration is **0.5%**. * For the upper limb, a volume of 30–50 mL (approx. 3 mg/kg) is used. This concentration provides an ideal balance: it is potent enough to achieve a sensory and motor block within 5–10 minutes but dilute enough to keep the total dose within safe limits. **2. Why the Other Options are Incorrect:** * **1-2% (Option B):** These concentrations are standard for infiltration or nerve blocks (e.g., Brachial Plexus block). In IVRA, using 1-2% would require a very high total dose of lignocaine to fill the vascular bed, significantly increasing the risk of seizures or cardiac arrest upon tourniquet release. * **4% and 5% (Options C & D):** These are hyperbaric or high-concentration formulations used for topical anesthesia (4%) or spinal anesthesia (5%). They are never used intravenously due to extreme toxicity. **Clinical Pearls for NEET-PG:** * **Drug of Choice:** Lignocaine 0.5% (Preservative-free). * **Contraindicated Drug:** **Bupivacaine** is strictly contraindicated in Bier’s block due to its high cardiotoxicity. * **Tourniquet Time:** The tourniquet must remain inflated for at least **20 minutes** to allow the drug to bind to tissues, preventing a massive bolus from entering systemic circulation. * **Prilocaine (0.5%)** is an alternative in some regions due to its lower toxicity, but it carries a risk of methemoglobinemia.

Question 54: Which of the following statements regarding a retrobulbar block is FALSE?

A. It can be administered to patients with bleeding disorders. (Correct Answer)
B. There is a risk of globe perforation.
C. The injection is placed behind the eye within the cone formed by the extraocular muscles.
D. The most common complication is retrobulbar hemorrhage.

Explanation: **Explanation** **1. Why Option A is the Correct (False) Statement:** Retrobulbar blocks are **contraindicated** in patients with bleeding disorders or those on therapeutic anticoagulation. The retrobulbar space is highly vascularized, and the block is performed "blindly" using a sharp needle. If a vessel is punctured, the resulting hemorrhage occurs in a confined space, leading to a rapid increase in intraocular pressure (IOP) which can threaten vision. For such patients, topical anesthesia or sub-Tenon’s blocks are safer alternatives. **2. Analysis of Incorrect Options:** * **Option B (Globe perforation):** This is a known, serious risk, especially in patients with high myopia (longer axial length) or staphyloma, where the sclera is thin. * **Option C (Anatomical placement):** This is the definition of the block. The needle is directed into the **intraconal space** (formed by the four recti muscles) to anesthetize the ciliary nerves, ciliary ganglion, and cranial nerves III, IV, and VI. * **Option D (Retrobulbar hemorrhage):** This is indeed the **most common** significant complication of this technique, occurring due to the accidental puncture of the ophthalmic artery or venous plexus. **Clinical Pearls for NEET-PG:** * **Classic Triad of Retrobulbar Block:** Anesthesia, Akinesia (loss of movement), and Abolition of the oculo-cardiac reflex. * **The "Post-retrobulbar Apnea Syndrome":** Occurs if the local anesthetic is accidentally injected into the dural sheath of the optic nerve, tracking back to the midbrain. * **Comparison:** Unlike retrobulbar blocks, **Peribulbar blocks** are extraconal, generally considered safer, but require a larger volume of anesthetic and have a slower onset.

Question 55: What is the most common complication seen after a Bier block?

A. Bradycardia
B. Hypotension (Correct Answer)
C. Nausea
D. Anxiety

Explanation: **Explanation:** A **Bier block**, or Intravenous Regional Anesthesia (IVRA), involves injecting a large volume of local anesthetic (typically Lidocaine) into a vein of an exsanguinated limb isolated by a pneumatic tourniquet. **Why Hypotension is the correct answer:** The most common systemic complication occurs during **tourniquet release**, which leads to the sudden entry of the local anesthetic bolus and metabolic byproducts (lactate, adenosine) into the systemic circulation. This results in systemic vasodilation and direct myocardial depression, leading to **hypotension**. While CNS toxicity (seizures) is the most feared complication, transient hypotension is the most frequently observed hemodynamic change following the release of the cuff. **Analysis of Incorrect Options:** * **A. Bradycardia:** While local anesthetic toxicity (LAST) can cause cardiac depression, hypotension due to peripheral vasodilation is more frequent. Bradycardia is usually a late sign of severe toxicity. * **C. Nausea:** This is a common side effect of general anesthesia and opioids, but it is not a primary or frequent complication specific to the hemodynamic shifts of a Bier block. * **D. Anxiety:** While patients may feel anxious during any regional procedure, it is a psychological state rather than a physiological complication of the block itself. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** 0.5% Lidocaine (Prilocaine is also used due to low toxicity). * **Contraindicated Drug:** **Bupivacaine** (due to high risk of irreversible cardiotoxicity if the tourniquet fails). * **Minimum Tourniquet Time:** The cuff must remain inflated for at least **20 minutes** to allow for tissue fixation of the drug and prevent a massive systemic bolus. * **Safety Measure:** Use a **double-cuff tourniquet** to prevent "tourniquet pain" and enhance safety.

Question 56: An inferior alveolar nerve block is absolutely contraindicated in patients suffering from which of the following diseases?

A. Thrombocytopenia
B. Hemophilia (Correct Answer)
C. Hypoprothrombinemia
D. Von Willebrand's disease

Explanation: **Explanation:** The **Inferior Alveolar Nerve Block (IANB)** is a deep nerve block that targets the nerve as it enters the mandibular foramen. This area is highly vascular, containing the inferior alveolar artery and vein, and is located within the pterygomandibular space. **Why Hemophilia is the Correct Answer:** In patients with **Hemophilia** (a deficiency of Factor VIII or IX), there is a severe defect in the intrinsic pathway of coagulation. A needle prick in the highly vascular pterygomandibular space can lead to an intramuscular hematoma. Because the tissues in this space are loose, the hematoma can expand rapidly, leading to **airway obstruction** or mediastinal spread of blood. Therefore, IANB is considered **absolutely contraindicated** in hemophiliacs unless they have received factor replacement therapy beforehand. **Analysis of Incorrect Options:** * **Thrombocytopenia (A):** While a low platelet count increases bleeding risk, it is generally considered a relative contraindication. Local infiltration or intraligamentary injections are preferred, but IANB is not "absolutely" contraindicated if the count is above a safe threshold (usually >50,000/mm³). * **Hypoprothrombinemia (C):** This refers to a deficiency in Vitamin K-dependent factors. While it poses a risk, it is often manageable and less likely to cause the rapid, life-threatening deep-space hematomas seen in classic Hemophilia. * **Von Willebrand's disease (D):** This is the most common hereditary coagulation disorder. While it involves both platelet adhesion and Factor VIII, it is often clinically milder than Hemophilia A or B. It is a relative contraindication, and many patients can be managed with desmopressin (DDAVP) prior to dental procedures. **High-Yield Clinical Pearls for NEET-PG:** * **Alternative:** In patients with bleeding diathesis, the **Gow-Gates technique** or **Akinosi block** are sometimes preferred as they are slightly less vascular, but **local infiltration** is the safest choice. * **Safe Zone:** Nerve blocks in non-compressible, deep vascular spaces are the most dangerous in coagulopathic patients. * **Management:** Always consult a hematologist before performing deep blocks in patients with known bleeding disorders. Factor levels should ideally be raised to **30-50%** before an IANB.

Question 57: Which of the following local anesthetics is an amide?

A. Lidocaine (Correct Answer)
B. Procaine
C. Chloroprocaine
D. Cocaine

Explanation: Local anesthetics are chemically classified into two main groups based on the linkage between their aromatic ring and hydrocarbon chain: **Amides** and **Esters**. ### 1. Why Lidocaine is Correct **Lidocaine** is an amide local anesthetic. A high-yield rule of thumb for NEET-PG is the **"i" rule**: Amide local anesthetics have two "i"s in their name (e.g., L**i**doca**i**ne, Pr**i**loca**i**ne, Bup**i**vaca**i**ne, Rop**i**vaca**i**ne). Amides are metabolized primarily in the **liver** by microsomal enzymes (CYP450) and generally have a longer duration of action and a lower risk of allergic reactions compared to esters. ### 2. Why the Other Options are Incorrect Options B, C, and D are all **Esters**. Esters have only one "i" in their name (e.g., Proca**i**ne, Chloroproca**i**ne, Coca**i**ne, Tetraca**i**ne). * **Procaine:** The first synthetic ester; it has a short duration and low potency. * **Chloroprocaine:** Known for its rapid onset and very short half-life due to rapid hydrolysis. * **Cocaine:** The only naturally occurring local anesthetic and the only one that causes **vasoconstriction** (by inhibiting norepinephrine reuptake). ### 3. High-Yield Clinical Pearls for NEET-PG * **Metabolism:** Esters are metabolized by **plasma pseudocholinesterase** to Para-aminobenzoic acid (PABA), which is responsible for the higher incidence of allergic reactions. * **Bupivacaine:** The most cardiotoxic amide; it dissociates slowly from sodium channels ("fast in, slow out"). **Intralipid 20%** is the antidote for toxicity. * **Prilocaine:** Associated with **methemoglobinemia** due to its metabolite, o-toluidine. * **Articaine:** An exception to the naming rule; it contains both an ester and an amide group but is classified as an amide.

Question 58: Regarding neuraxial anesthesia, which of the following statements is true?

A. Aspirin should be stopped 7 days before surgery
B. Unfractionated heparin should be stopped 7 days before surgery
C. Fondaparinux should be stopped 7 days before surgery
D. Clopidogrel should be stopped 7 days before surgery (Correct Answer)

Explanation: The primary concern when performing neuraxial anesthesia (spinal or epidural) in patients on anticoagulants is the risk of a **spinal-epidural hematoma**, which can lead to permanent neurological damage. Management is guided by the **ASRA (American Society of Regional Anesthesia) guidelines**. ### **Explanation of Options** * **Clopidogrel (Correct):** Clopidogrel is a P2Y12 receptor inhibitor that causes irreversible platelet inhibition. To ensure adequate platelet function and minimize the risk of hematoma, it must be discontinued **7 days** prior to neuraxial blockade. * **Aspirin (Incorrect):** According to ASRA guidelines, NSAIDs and Aspirin (monotherapy) do **not** significantly increase the risk of spinal hematoma. Therefore, they do **not** need to be stopped before neuraxial anesthesia. * **Unfractionated Heparin (Incorrect):** For subcutaneous prophylaxis (5000 units BID), there is no contraindication. For intravenous therapeutic heparin, the infusion should be stopped **4–6 hours** before the procedure, and coagulation status (aPTT) should be normalized. It does not require a 7-day window. * **Fondaparinux (Incorrect):** This is a synthetic pentasaccharide (Factor Xa inhibitor). The recommended wait time for neuraxial anesthesia is **36–42 hours** after the last dose, not 7 days. ### **High-Yield Clinical Pearls for NEET-PG** * **Ticlopidine:** Must be stopped **10–14 days** before (longest duration). * **Prasugrel:** Must be stopped **7–10 days** before. * **Ticagrelor:** Must be stopped **5 days** before. * **Warfarin:** Must be stopped **5 days** before (ensure INR < 1.5). * **LMWH (Enoxaparin):** Stop **12 hours** for prophylactic doses and **24 hours** for therapeutic doses. * **Restarting:** Most antiplatelets can be restarted 24 hours post-operatively, provided there is no surgical bleeding.

Question 59: Which local anesthetic was used first historically?

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

Explanation: **Explanation:** The correct answer is **Cocaine**. Historically, cocaine was the first local anesthetic discovered and used in clinical practice. It is a naturally occurring alkaloid derived from the leaves of the *Erythroxylon coca* plant. In **1884**, **Karl Koller**, an Austrian ophthalmologist, first demonstrated its clinical utility for topical anesthesia during eye surgery. Shortly after, William Halsted used it to perform the first nerve block. **Analysis of Incorrect Options:** * **Procaine (Option A):** Synthesized by Alfred Einhorn in 1905, it was the first **synthetic** ester local anesthetic. It was developed as a less toxic alternative to cocaine but is not the "first" historically. * **Lignocaine/Lidocaine (Option B):** Synthesized by Nils Löfgren in 1943, it was the first **amide-linked** local anesthetic. It revolutionized anesthesia due to its rapid onset and stability. * **Bupivacaine (Option C):** An amide anesthetic synthesized in 1957. It is known for its long duration of action and sensory-motor dissociation but was developed much later in the timeline. **High-Yield Clinical Pearls for NEET-PG:** * **Chemical Structure:** Cocaine is an **ester**. All local anesthetics with one "i" in their name are esters (e.g., Procaine, Cocaine), while those with two "i"s are amides (e.g., Lignocaine, Bupivacaine). * **Unique Property:** Cocaine is the only local anesthetic that causes **vasoconstriction** (by inhibiting norepinephrine reuptake). All other local anesthetics are vasodilators. * **Metabolism:** Esters are metabolized by **plasma pseudocholinesterase**, whereas amides are metabolized in the **liver**.

Question 60: All of the following are advantages of epidural anesthesia over spinal anesthesia, except:

A. Dural puncture is avoided
B. Chances of meningitis are very low
C. Post-spinal headache is avoided
D. Its duration of action is very short (Correct Answer)

Explanation: ### Explanation The correct answer is **D. Its duration of action is very short.** In clinical practice, **epidural anesthesia** actually offers a **longer and more flexible duration of action** compared to spinal anesthesia. This is because epidural anesthesia is typically administered via a catheter, allowing for continuous infusion or repeated boluses of local anesthetics. In contrast, spinal anesthesia is usually a "single-shot" technique with a fixed duration determined by the initial dose. #### Analysis of Options: * **Option A & C:** In epidural anesthesia, the needle stops in the epidural space, and the **dura mater is not intentionally punctured**. Since the dura remains intact, the leakage of cerebrospinal fluid (CSF) is prevented, thereby **avoiding Post-Dural Puncture Headache (PDPH)**, a common complication of spinal anesthesia. * **Option B:** Because the subarachnoid space is not entered, the risk of introducing pathogens directly into the CSF is significantly lower in epidural anesthesia compared to spinal anesthesia, making the **incidence of meningitis extremely rare**. * **Option D (Correct):** This statement is false. Epidural anesthesia is preferred for long surgical procedures (e.g., prolonged labor or major abdominal surgeries) precisely because its duration can be extended indefinitely via a catheter. #### High-Yield Clinical Pearls for NEET-PG: * **Site of Action:** Spinal anesthesia acts on the spinal cord/nerve roots; Epidural acts primarily on the **spinal nerve roots** as they exit the intervertebral foramina. * **Drug Volume:** Epidural requires a **much larger volume** of local anesthetic (15–20 mL) compared to spinal (2–4 mL). * **Onset:** Spinal anesthesia has a **rapid onset** (2–5 mins), whereas epidural is **slower** (15–20 mins). * **Segmental Block:** Epidural allows for a "segmental block" (targeting specific dermatomes), which is not possible with standard spinal anesthesia. * **Test Dose:** A test dose (3 mL of 1.5% Lignocaine with 1:200,000 Adrenaline) is used in epidurals to rule out accidental intravascular or subarachnoid injection.

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

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Continuous Peripheral Nerve Catheters

Practice Questions

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