Regional Anesthesia Practice Questions

Q: The Macintosh indicator is used for what purpose?

Localization of the extradural space. The **Macintosh indicator** (also known as the Macintosh balloon) is a classic device used for the **localization of the extradural (epidural) space**. ### 1. Why the correct answer is right The identification of the epidural space relies on the principle of **"Loss of Resistance" (LOR)**. The epidural space has a sub-atmospheric (negative) pressure. The Macintosh indicator consists of a small, sensitive rubber balloon attached to the hub of an epidural needle. * The balloon is inflated with a small amount of air while the needle is in the ligamentum flavum (high resistance). * As the needle enters the epidural space, the negative pressure and the lack of resistance cause the balloon to **abruptly deflate**, signaling correct placement. ### 2. Why the other options are wrong * **Option A:** Neuromuscular blockade is assessed using a **Peripheral Nerve Stimulator** (e.g., Train-of-Four monitoring). * **Option C:** The level/depth of general anesthesia is monitored using clinical signs or processed EEG monitors like **BIS (Bispectral Index)** or Entropy. * **Option D:** Respiratory depression is monitored via **Capnography (EtCO2)** and Pulse Oximetry (SpO2). ### 3. High-Yield Clinical Pearls for NEET-PG * **Other LOR Devices:** Apart from the Macintosh balloon, the **Odom’s indicator** (a glass capillary tube with a bubble) and the **Zander’s modified syringe** are also used for epidural localization. * **Gold Standard:** The most common clinical method remains the **Loss of Resistance to Saline** (preferred over air to avoid the risk of air embolism or patchy block). * **Distance:** In an average adult, the distance from the skin to the epidural space is approximately **4–6 cm**. * **Ligamentum Flavum:** This is the thickest ligament the needle pierces before entering the epidural space; it provides the "gritty" sensation and high resistance.

Q: A 24-year-old female is examined by an obstetrician in a delivery room. The obstetrician injects lidocaine near the tip of the ischial spine. Which nerve is blocked by the drug?

Pudendal nerve. ### Explanation **Correct Answer: B. Pudendal Nerve** The **pudendal nerve (S2–S4)** is the primary nerve blocked during a pudendal nerve block, a common procedure used in the second stage of labor for vaginal deliveries or minor perineal surgeries. **Anatomical Basis:** The pudendal nerve exits the pelvis through the greater sciatic foramen, passes behind the **sacrospinous ligament**, and re-enters through the lesser sciatic foramen. The **ischial spine** serves as the key clinical landmark for this block. When an anesthetic (like lidocaine) is injected transvaginally or transperineally near the tip of the ischial spine, it anesthetizes the nerve as it crosses the sacrospinous ligament. This provides sensory loss to the perineum and the lower third of the vagina. --- ### Analysis of Incorrect Options: * **A. Genitofemoral nerve (L1, L2):** Its femoral branch provides sensation to the upper anterior thigh, while the genital branch supplies the labia majora/scrotum and the cremasteric muscle. It does not pass near the ischial spine. * **C. Obturator nerve (L2–L4):** This nerve passes through the obturator canal to supply the adductor muscles of the thigh and the skin of the medial thigh. * **D. Iliohypogastric nerve (T12, L1):** This nerve supplies the skin over the hypogastric region and the lateral gluteal area. --- ### High-Yield Clinical Pearls for NEET-PG: 1. **Landmark:** The **ischial spine** is the most important palpable landmark for a pudendal block. 2. **Nerve Roots:** Pudendal nerve originates from the anterior rami of **S2, S3, and S4**. 3. **Limitations:** A pudendal block provides perineal anesthesia but **does not** abolish the pain of uterine contractions (which is mediated by T10–L1 sympathetic fibers). 4. **Complication:** Accidental intravascular injection into the **internal pudendal artery** (which runs adjacent to the nerve) is a potential risk.

Q: Following spinal subarachnoid block, a patient develops hypotension. Which of the following measures is NOT used for its management?

Lowering the head end. **Explanation:** Hypotension following spinal anesthesia is primarily caused by a **sympathetic blockade**, leading to venous pooling (decreased preload) and arterial vasodilation (decreased systemic vascular resistance). **Why "Lowering the head end" is the correct answer (NOT used):** While Trendelenburg (head-down) position was historically used to increase venous return, it is **avoided** immediately after a spinal block using hyperbaric local anesthetics. Lowering the head end can cause the anesthetic drug to spread cephalad (upward) due to gravity, potentially leading to a **"High Spinal"** or **"Total Spinal."** This can cause respiratory paralysis by blocking the phrenic nerve (C3-C5) and severe bradycardia by blocking cardioaccelerator fibers (T1-T4). **Analysis of other options:** * **Option B (Preloading):** Administering 500–1000 ml of crystalloids (like Ringer's Lactate) before the block expands intravascular volume to compensate for the impending vasodilation. * **Option C (Vasopressors):** Drugs like Phenylephrine or Methoxamine (alpha-1 agonists) cause vasoconstriction, directly counteracting the sympathetic block. * **Option D (Inotropes):** Dopamine or Ephedrine are used if hypotension is accompanied by bradycardia, as they provide both vasoconstriction and positive inotropic/chronotropic effects. **High-Yield Clinical Pearls for NEET-PG:** * **Level of Block:** Sympathetic denervation usually extends **2–3 segments higher** than the sensory block. * **Bezold-Jarisch Reflex:** Severe hypotension and bradycardia after spinal anesthesia can occur due to this reflex (triggered by low ventricular volume). * **Drug of Choice:** **Phenylephrine** is currently preferred for managing spinal-induced hypotension in obstetric patients as it maintains fetal pH better than ephedrine. * **Co-loading:** Administering fluids *at the same time* as the block is initiated is now considered more effective than pre-loading.

Q: Peribulbar injection is given in which space?

Periorbital space. **Explanation:** The correct answer is **C. Periorbital space**. In ophthalmic regional anesthesia, the goal is to deposit local anesthetic around the globe to achieve sensory block and akinesia. The **peribulbar block** involves injecting the anesthetic into the space **outside the muscle cone** (extraconal space) but within the orbit. This space is anatomically referred to as the **periorbital space**. The anesthetic then diffuses into the muscle cone and across the lids to provide the desired effect. **Analysis of Options:** * **A. Subtenon space:** This refers to the space between the Tenon’s capsule and the sclera. A Sub-Tenon block involves a blunt cannula injection directly into this potential space, providing rapid anesthesia with a lower risk of globe perforation. * **B. Muscle cone:** This is the target for a **Retrobulbar block**. In this technique, the needle penetrates the muscle cone (intraconal space) to deposit anesthetic near the ciliary nerves and ganglion. While effective, it carries a higher risk of optic nerve injury and brainstem anesthesia. * **D. Subperiorbital space:** This is a potential space between the periorbita (periosteum of the orbit) and the bony orbital wall, typically not the target for routine ophthalmic blocks. **High-Yield Clinical Pearls for NEET-PG:** * **Peribulbar vs. Retrobulbar:** Peribulbar is generally considered safer because the needle remains **extraconal**, reducing the risk of retrobulbar hemorrhage and optic nerve trauma. * **Volume:** Peribulbar blocks require a larger volume of anesthetic (6–10 mL) compared to retrobulbar blocks (2–4 mL). * **Hyaluronidase:** Often added to the local anesthetic mix to promote tissue diffusion, improving the success rate of the peribulbar block. * **Complication:** The most serious (though rare) complication of orbital blocks is **"Post-retrobulbar apnea syndrome"** due to accidental injection into the CNS via the optic nerve sheath.

Q: Which ester local anesthetic undergoes significant liver metabolism?

Cocaine. **Explanation:** Local anesthetics (LAs) are classified into two groups based on their chemical linkage: **Esters** and **Amides**. The primary metabolic pathway for most ester LAs is rapid hydrolysis by **pseudocholinesterase** (plasma cholinesterase) in the blood. **Why Cocaine is the Correct Answer:** Cocaine is a unique ester local anesthetic. Unlike other esters that are metabolized almost exclusively in the plasma, **Cocaine undergoes significant metabolism in the liver** via carboxylesterase enzymes. While some of it is hydrolyzed by plasma cholinesterase, the hepatic pathway is a major route for its transformation into metabolites like benzoylecgonine (which is excreted in the urine). **Analysis of Incorrect Options:** * **Procaine & Chloroprocaine:** These are classic esters with very short half-lives. They are rapidly and completely hydrolyzed by plasma pseudocholinesterase. Chloroprocaine is the shortest-acting LA due to this rapid metabolism. * **Tetracaine:** A long-acting ester, it is also metabolized by plasma pseudocholinesterase, though at a slower rate than procaine. **NEET-PG High-Yield Pearls:** 1. **Metabolism Rule:** Remember the "i" rule. Am**i**des (Lidocaine, Bupivacaine, Ropivacaine) have two "i"s in their name and are metabolized in the **Liver**. Esters (one "i") are metabolized in the **Plasma**. Cocaine is the notable exception. 2. **Vasoconstriction:** Cocaine is the only local anesthetic that causes **vasoconstriction** by blocking the reuptake of norepinephrine. All other LAs (except to some extent Ropivacaine/Levobupivacaine) are vasodilators. 3. **PABA:** Metabolism of ester LAs produces **para-aminobenzoic acid (PABA)**, which is responsible for the higher incidence of allergic reactions compared to amides.

Q: All of the following are absolute contraindications for neuraxial anesthesia, EXCEPT:

Bowel perforation. **Explanation:** Neuraxial anesthesia (Spinal/Epidural) involves blocking sympathetic outflow, leading to significant physiological changes. Understanding the distinction between absolute and relative contraindications is high-yield for NEET-PG. **Why Bowel Perforation is the Correct Answer:** Bowel perforation is **not** a contraindication for neuraxial anesthesia; in fact, it is often considered a **relative indication**. Spinal anesthesia causes a "contracted, quiet bowel" due to the blockade of sympathetic fibers (T5–L2) while leaving parasympathetic (vagal) tone unopposed. This improves surgical exposure and reduces the risk of aspiration compared to general anesthesia in a "full stomach" emergency. **Analysis of Incorrect Options (Absolute Contraindications):** * **Patient on Anticoagulants:** This is an absolute contraindication due to the high risk of **spinal/epidural hematoma**, which can lead to permanent neurological deficits or paraplegia. * **Fixed Output State:** Conditions like severe aortic or mitral stenosis are absolute contraindications. Neuraxial blocks cause peripheral vasodilation and a drop in systemic vascular resistance (SVR). Patients with fixed cardiac output cannot increase their stroke volume to compensate, leading to catastrophic hypotension and cardiac arrest. * **Hypovolemic Shock:** Severe hypovolemia is an absolute contraindication. The sympathetic blockade causes massive vasodilation, which, in the absence of adequate intravascular volume, leads to profound, irreversible circulatory collapse. **High-Yield Clinical Pearls:** * **Absolute Contraindications:** Patient refusal (most important), infection at the site, raised ICP (risk of herniation), and severe coagulopathy. * **Relative Contraindications:** Sepsis, neurological disorders (e.g., Multiple Sclerosis), and minor skeletal deformities. * **Sympathetic Blockade:** Usually extends 2–6 segments higher than the sensory block.

Question 1

In an ankle block, which of the following nerves is typically NOT blocked?

Accepted Answer

Common peroneal nerve

Answer

Superficial peroneal nerve

Answer

Deep peroneal nerve

Answer

Saphenous nerve

Question 2

Which of the following techniques of local anesthesia requires extraoral landmarks?

Accepted Answer

Gowgates

Answer

High tuberosity approach

Answer

Fischer 123

Answer

Vazirani-Akinosi

Question 3

The Macintosh indicator is used for what purpose?

Accepted Answer

Localization of the extradural space

Answer

Assessing the degree of neuromuscular blockade

Answer

Assessing the level of general anesthesia

Answer

Monitoring respiratory depression

Question 4

A 24-year-old female is examined by an obstetrician in a delivery room. The obstetrician injects lidocaine near the tip of the ischial spine. Which nerve is blocked by the drug?

Accepted Answer

Pudendal nerve

Answer

Genitofemoral nerve

Answer

Obturator nerve

Answer

Iliohypogastric nerve

Question 5

What is the anesthesia modality of choice for a 65-year-old male patient with a history of coronary artery disease diagnosed with hemorrhoids undergoing hemorrhoidectomy?

Accepted Answer

Saddle anesthesia

Answer

Spinal anesthesia

Answer

General anesthesia

Answer

Caudal anesthesia

Question 6

Following spinal subarachnoid block, a patient develops hypotension. Which of the following measures is NOT used for its management?

Accepted Answer

Lowering the head end

Answer

Administration of 1000 ml of Ringer's lactate before the block

Answer

Administration of a vasopressor drug like methoxamine

Answer

Administration of an ionotrope like dopamine

Question 7

Peribulbar injection is given in which space?

Accepted Answer

Periorbital space

Answer

Subtenon space

Answer

Muscle cone

Answer

Subperiorbital space

Question 8

Which ester local anesthetic undergoes significant liver metabolism?

Accepted Answer

Cocaine

Answer

Tetracaine

Answer

Procaine

Answer

Chloroprocaine

Question 9

All of the following are absolute contraindications for neuraxial anesthesia, EXCEPT:

Accepted Answer

Bowel perforation

Answer

Patient on anticoagulants

Answer

Fixed output state

Answer

Hypovolemic shock

Question 10

Neuraxial blocks as a primary anesthetic technique can be used for which of the following surgeries?

Accepted Answer

Upper abdominal surgery

Answer

Lower abdominal surgery

Answer

Urogenital Surgery

Answer

Lower extremity surgery

Regional Anesthesia — MCQs

Regional Anesthesia — MCQs

On this page

Practice by Chapter

Want unlimited practice?