Regional Anesthesia Practice Questions

Q: What is the vasopressor of choice in hypotension produced during subarachnoid block?

Ephedrine. **Explanation:** Hypotension during **Subarachnoid Block (SAB)** is primarily caused by a sympathetic blockade, leading to venous pooling (decreased preload) and arterial vasodilation (decreased systemic vascular resistance). **Why Ephedrine is the Correct Choice:** Ephedrine is traditionally considered the drug of choice because it is a **mixed-acting sympathomimetic** (direct and indirect action on $\alpha$ and $\beta$ receptors). 1. **$\beta_1$ activity:** Increases heart rate and cardiac contractility. 2. **$\alpha_1$ activity:** Causes peripheral vasoconstriction. Crucially, in obstetric anesthesia, Ephedrine is preferred because it maintains **uteroplacental blood flow** better than pure alpha-agonists, although recent trends are shifting toward Phenylephrine in specific maternal contexts. **Analysis of Incorrect Options:** * **Mephenteramine:** Similar to Ephedrine but less potent. While commonly used in Indian clinical practice, Ephedrine remains the standard textbook answer for exams. * **Adrenaline:** A potent catecholamine used for cardiac arrest or anaphylaxis. It is too potent for routine post-spinal hypotension and can cause dangerous tachycardia and arrhythmias. * **Dopamine:** Requires infusion and is typically reserved for cardiogenic or septic shock; its onset is too slow for the acute management of spinal-induced hypotension. **High-Yield Clinical Pearls for NEET-PG:** * **Phenylephrine** is now often considered the "gold standard" for spinal hypotension in **obstetric patients** to avoid fetal acidosis, but **Ephedrine** remains the classic "choice" in general surgical scenarios and standard MCQ patterns. * The first-line management for post-spinal hypotension is **fluid pre-loading or co-loading** (crystalloids/colloids). * If hypotension is accompanied by **bradycardia** (due to block of T1-T4 cardioaccelerator fibers), Ephedrine or Atropine is mandatory.

Q: Regarding lidocaine, which of the following statements is false?

It is an ester-type local anesthetic.. ### Explanation **1. Why Option C is the correct (false) statement:** Local anesthetics are classified into two groups based on their chemical linkage: **Amides** and **Esters**. Lidocaine (Lignocaine) is an **Amide-type** local anesthetic, not an ester. * **High-Yield Rule:** Amide 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). Ester anesthetics have only one "i" (e.g., Coca**i**ne, Proca**i**ne, Benzoca**i**ne, Tetraca**i**ne). Amides are metabolized in the liver, whereas esters are metabolized by plasma pseudocholinesterase. **2. Analysis of other options:** * **Option A (True):** Lidocaine is the most widely used local anesthetic due to its rapid onset and intermediate duration of action. It works by blocking voltage-gated sodium channels. * **Option B (True):** Lidocaine is a **Class IB anti-arrhythmic**. It is used intravenously to treat ventricular arrhythmias, particularly those associated with acute myocardial infarction or cardiac surgery. * **Option D (True):** Lidocaine has excellent penetrative properties and is effective on mucous membranes. It is commonly used as a topical spray (10%) for airway anesthesia or as a jelly (2%) for urethral lubrication and anesthesia. **3. Clinical Pearls for NEET-PG:** * **Maximum Dose:** The maximum dose of plain lidocaine is **4 mg/kg**, and with adrenaline, it is **7 mg/kg**. * **Toxicity:** Early signs of LAST (Local Anesthetic Systemic Toxicity) include perioral numbness, metallic taste, and tinnitus. * **Metabolism:** Since lidocaine is metabolized by hepatic microsomal enzymes (CYP1A2), its clearance is reduced in patients with liver disease or congestive heart failure. * **EMLA Cream:** A eutectic mixture of Lidocaine (2.5%) and Prilocaine (2.5%) used for topical skin anesthesia.

Q: EMLA cream is effective in relieving pain of which procedures?

All of the above. **Explanation:** **EMLA (Eutectic Mixture of Local Anesthetics)** is a topical anesthetic consisting of a 1:1 mixture of **2.5% Lidocaine and 2.5% Prilocaine**. The term "eutectic" refers to the fact that the combination has a melting point lower than either drug individually, allowing it to exist as an oil at room temperature. This property enhances its penetration through intact skin to reach the underlying dermis. **Why "All of the Above" is correct:** EMLA cream is specifically designed to provide surface anesthesia for procedures involving skin penetration. * **Venipuncture & Arterial Cannulation:** It effectively numbs the skin and subcutaneous tissue, significantly reducing the pain associated with needle insertion into vessels. * **Lumbar Puncture:** While it does not provide deep anesthesia for the spinal ligaments, it effectively numbs the initial skin puncture site, which is often the most distressing part of the procedure for pediatric or anxious patients. **High-Yield Clinical Pearls for NEET-PG:** 1. **Application Time:** For optimal effect, EMLA must be applied under an **occlusive dressing** for at least **45–60 minutes**. Maximum depth of penetration (approx. 5 mm) is achieved after 120 minutes. 2. **Contraindications:** It should **not** be used on broken skin, mucous membranes, or in patients with a known allergy to amide-type local anesthetics. 3. **Methemoglobinemia:** Due to the presence of Prilocaine (which metabolizes to o-toluidine), EMLA should be used with caution in infants under 3 months of age or those taking other methemoglobin-inducing drugs. 4. **Vasoconstriction/Vasodilation:** It initially causes vasoconstriction followed by vasodilation, which may occasionally make small vein cannulation slightly more challenging.

Q: Local anesthetic toxicity is maximally seen with which of the following routes of administration?

Intercostal space block. The systemic absorption of local anesthetics (LA) depends primarily on the **vascularity** of the injection site. The higher the blood flow to the area, the faster the drug enters the systemic circulation, increasing the peak plasma concentration and the risk of Local Anesthetic Systemic Toxicity (LAST). **Why Intercostal Space Block is Correct:** The intercostal space is highly vascular. When LA is injected here, it is rapidly absorbed into the systemic circulation due to the proximity of the intercostal vessels. This route consistently produces the **highest peak plasma levels** of local anesthetics compared to any other regional technique. **Analysis of Other Options:** * **Caudal and Epidural Blocks:** While these areas are vascular (epidural venous plexus), the absorption rate is lower than the intercostal route. Caudal blocks generally have slightly higher absorption rates than lumbar epidurals but remain lower than intercostal blocks. * **Sciatic-Femoral Nerve Block:** These are peripheral nerve blocks involving large tissue areas with relatively lower vascularity compared to the trunk or airway mucosa, resulting in slower systemic absorption. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Rate of Absorption (Highest to Lowest):** **"I** **I**nhailed **E**very **C**onfusing **B**it of **S**ubcutaneous **S**tuff" **I**ntercostal > **I**nguinal/Caudal > **E**pidural > **C**ervical Plexus > **B**rachial Plexus > **S**ciatic/Femoral > **S**ubcutaneous. * **Most Toxic LA:** Bupivacaine (due to high cardiotoxicity). * **Treatment of Choice for LAST:** 20% Intralipid emulsion (Lipid Rescue). * **Early Sign of Toxicity:** Perioral numbness, metallic taste, or tinnitus.

Q: What is the order of absorption routes for local anesthetics, from fastest to slowest?

Tracheal > Intercostal block > Lumbar epidural > Subcutaneous. **Explanation:** The rate of systemic absorption of local anesthetics (LA) is primarily determined by the **vascularity** of the injection site. Higher blood flow leads to faster absorption into the systemic circulation, increasing the risk of Local Anesthetic Systemic Toxicity (LAST). 1. **Tracheal:** The tracheal mucosa is highly vascular, leading to the most rapid absorption (comparable to an intravenous injection). 2. **Intercostal:** The intercostal space contains a high density of vessels, making it the fastest peripheral nerve block site for absorption. 3. **Lumbar Epidural:** While vascular, the epidural space contains fat and a lower density of vessels compared to the intercostal or tracheal routes. 4. **Subcutaneous:** This area has relatively poor perfusion, resulting in the slowest absorption rate. **Analysis of Options:** * **Option B (Correct):** Correctly follows the vascularity gradient: **T**racheal > **I**ntercostal > **C**audal > **E**pidural > **B**rachial plexus > **S**ciatic/Femoral > **S**ubcutaneous. * **Option A:** Incorrectly places Lumbar epidural before Intercostal. Intercostal blocks always result in higher peak plasma levels than epidural blocks. * **Option C:** This is the reverse order; subcutaneous is the slowest, not the fastest. * **Option D:** Incorrectly places Lumbar epidural as the fastest route. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Remember **"BICEPS"** or **"TI CEBSS"** (**T**racheal, **I**ntercostal, **C**audal, **E**pidural, **B**rachial plexus, **S**ciatic, **S**ubcutaneous). * **LAST Risk:** The site of injection is the most important patient-independent factor for predicting systemic toxicity. * **Vasoconstrictors:** Adding Epinephrine (1:200,000) reduces the rate of absorption, especially in highly vascular areas like the intercostal space.

Q: Which of the following is NOT true about post-spinal headache?

Old age is a risk factor.. **Explanation:** Post-Dural Puncture Headache (PDPH) occurs due to the leakage of cerebrospinal fluid (CSF) through a dural hole, leading to low CSF pressure and compensatory cerebral vasodilation. **Why Option D is the Correct Answer (The False Statement):** Contrary to the option, **old age is a protective factor**, not a risk factor. PDPH is most common in young adults (20–40 years), particularly pregnant women. In the elderly, the dura is less elastic and the epidural space is more fibrotic, which helps the dural puncture site seal more quickly, reducing the incidence of headache. **Analysis of Other Options:** * **Option A:** PDPH is characteristically **positional**. It worsens within seconds of sitting or standing and is significantly relieved by lying flat (supine). * **Option B:** The pain is typically bilateral and most commonly felt in the **frontal or occipital** regions, sometimes radiating to the neck and shoulders. * **Option C:** Using a **small-bore needle** (e.g., 25G–27G) and non-cutting "pencil-point" needles (e.g., Sprotte or Whitacre) significantly reduces the risk by creating a smaller, more easily healed dural defect. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Treatment:** Epidural Blood Patch (EBP) is the most effective treatment for persistent PDPH. * **Needle Type:** Pencil-point needles (Whitacre/Sprotte) have a lower incidence of PDPH compared to cutting-tip needles (Quincke). * **Orientation:** If using a cutting needle, the bevel should be kept parallel to the longitudinal fibers of the dura to minimize damage. * **Conservative Management:** Includes bed rest, aggressive hydration, and oral/IV caffeine (which causes cerebral vasoconstriction).

Q: The block shown in the diagram is going to affect all of the following nerves EXCEPT?

Buccal nerve. ***Buccal nerve*** - The **buccal nerve** is a branch of the **anterior division of mandibular nerve (V3)** and is NOT blocked by the inferior alveolar nerve block (IANB). - It requires a **separate buccal nerve block** as it has a different anatomical pathway and injection site. *Inferior alveolar nerve* - This nerve is the **primary target** of the IANB and is completely anesthetized during the procedure. - It provides sensation to the **mandibular teeth** and **lower lip** on the injected side. *Lingual nerve* - The **lingual nerve** runs close to the inferior alveolar nerve and is routinely blocked during IANB. - It provides sensation to the **anterior two-thirds of the tongue** and **floor of the mouth**. *Mental nerve* - The **mental nerve** is the terminal branch of the inferior alveolar nerve that exits through the **mental foramen**. - It is blocked as part of the IANB since it's a continuation of the inferior alveolar nerve pathway.

Question 1

What is the vasopressor of choice in hypotension produced during subarachnoid block?

Accepted Answer

Ephedrine

Answer

Mephenteramine

Answer

Adrenaline

Answer

Dopamine

Question 2

For which of the following is continuous epidural anaesthesia used?

Accepted Answer

Postoperative analgesia

Answer

Extending the duration of surgery

Answer

General anaesthesia

Answer

Use in children

Question 3

Regarding lidocaine, which of the following statements is false?

Accepted Answer

It is an ester-type local anesthetic.

Answer

It is a local anesthetic.

Answer

It is used to treat cardiac arrhythmias.

Answer

It acts on mucous membranes.

Question 4

EMLA cream is effective in relieving pain of which procedures?

Accepted Answer

All of the above

Answer

Venipuncture

Answer

Arterial cannulation

Answer

Lumbar puncture

Question 5

What is true regarding a bilateral mandibular block?

Accepted Answer

It is not contraindicated.

Answer

It is dangerous because the patient may swallow their tongue.

Answer

It will lead to a space infection.

Answer

It should rarely be performed.

Question 6

Local anesthetic toxicity is maximally seen with which of the following routes of administration?

Accepted Answer

Intercostal space block

Answer

Epidural

Answer

Caudal space block

Answer

Sciatic-femoral nerve block

Question 7

What is the order of absorption routes for local anesthetics, from fastest to slowest?

Accepted Answer

Tracheal > Intercostal block > Lumbar epidural > Subcutaneous

Answer

Tracheal > Lumbar epidural > Intercostal block > Subcutaneous

Answer

Subcutaneous > Intercostal block > Lumbar epidural > Tracheal

Answer

Lumbar epidural > Intercostal block > Tracheal > Subcutaneous

Question 8

Which of the following is NOT true about post-spinal headache?

Accepted Answer

Old age is a risk factor.

Answer

It is relieved by lying down.

Answer

It is typically frontal or occipital.

Answer

It can be prevented by using a small bore needle.

Question 9

The topical use of which of the following local anesthetics is not recommended?

Accepted Answer

Bupivacaine

Answer

Lidocaine

Answer

Cocaine

Answer

Dibucaine

Question 10

The block shown in the diagram is going to affect all of the following nerves EXCEPT?

Accepted Answer

Buccal nerve

Answer

Inferior alveolar nerve

Answer

Lingual nerve

Answer

Mental nerve

Regional Anesthesia — MCQs

Regional Anesthesia — MCQs

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