Regional Anesthesia — MCQs

Regional Anesthesia Indian Medical PG Practice Questions and MCQs

Question 61: Which of the following is NOT a contraindication for combined spinal and epidural anesthesia?

A. Platelet count < 50,000
B. Patient on clopidogrel
C. Local infection
D. Patient on antihypertensive medication (Correct Answer)

Explanation: **Explanation:** Combined Spinal-Epidural (CSE) anesthesia involves puncturing the dural sac and placing an epidural catheter. The primary contraindications for neuraxial blocks are categorized into absolute (e.g., patient refusal, infection at the site, severe hypovolemia) and relative (e.g., coagulopathy). **Why Option D is Correct:** **Patients on antihypertensive medications** (such as ACE inhibitors, Beta-blockers, or Calcium channel blockers) are **not contraindicated** for neuraxial anesthesia. In fact, most antihypertensives are continued until the morning of surgery to maintain hemodynamic stability. While neuraxial blocks cause sympathetic blockade and potential hypotension, this is managed with fluid loading and vasopressors, not by avoiding the technique. **Why Incorrect Options are Wrong:** * **Platelet count < 50,000 (Option A):** This is a **relative/absolute contraindication**. A low platelet count significantly increases the risk of an **epidural hematoma**, which can cause permanent neurological damage due to cord compression. Generally, a count >80,000–100,000 is preferred for CSE. * **Patient on Clopidogrel (Option B):** Antiplatelet agents like Clopidogrel must be stopped **5–7 days** prior to neuraxial blockade to prevent hematoma formation. * **Local Infection (Option C):** Infection at the needle insertion site is an **absolute contraindication** as it risks introducing bacteria into the subarachnoid or epidural space, leading to meningitis or an epidural abscess. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindications:** Patient refusal, raised intracranial pressure (risk of herniation), and severe uncorrected hypovolemia. * **ASRA Guidelines:** For patients on **Warfarin**, the INR must be **<1.5** before performing neuraxial blocks. * **Aspirin:** Unlike Clopidogrel, NSAIDs or low-dose Aspirin alone are generally *not* contraindications for neuraxial anesthesia if used as monotherapy.

Question 62: For which of the following conditions is epidural analgesia considered suitable?

A. Rib fracture
B. Lower abdominal surgery
C. Thoracotomy
D. All of the above (Correct Answer)

Explanation: **Explanation:** Epidural analgesia is a versatile regional anesthesia technique involving the injection of local anesthetics and/or opioids into the epidural space. Its primary utility lies in its ability to provide **segmental analgesia**, making it suitable for a wide range of clinical scenarios depending on the level of catheter insertion (cervical, thoracic, or lumbar). * **Rib Fractures (Option A):** Thoracic epidural analgesia is the "gold standard" for managing multiple rib fractures. By providing superior pain relief, it prevents splinting, improves tidal volume, and facilitates effective coughing, thereby significantly reducing the risk of pulmonary complications like pneumonia. * **Lower Abdominal Surgery (Option B):** Lumbar or low-thoracic epidural catheters are routinely used for surgeries such as hysterectomies or colorectal procedures. They provide excellent intraoperative anesthesia (when combined with GA) and prolonged postoperative pain relief. * **Thoracotomy (Option C):** Thoracic epidural analgesia (TEA) is highly effective for the intense post-thoracotomy pain. It helps in early mobilization and reduces the incidence of chronic post-surgical pain. Since epidural blocks can be tailored to specific dermatomes (Thoracic for chest/upper abdomen and Lumbar for lower abdomen/limbs), **Option D (All of the above)** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Action:** The primary site of action for local anesthetics in an epidural is the **spinal nerve roots** as they traverse the epidural space. * **Identification of Space:** The most common technique used is the **"Loss of Resistance" (LOR)** to saline or air. * **Contraindications:** Absolute contraindications include patient refusal, local infection at the site, uncorrected hypovolemia, and **coagulopathy** (due to the risk of epidural hematoma). * **Test Dose:** A standard test dose (3 mL of 1.5% Lignocaine with 1:200,000 Adrenaline) is used to rule out accidental intravascular or intrathecal injection.

Question 63: Alkalization of local anesthetic solutions by the addition of sodium bicarbonate has the following benefits, except:

A. Speeds the onset
B. Improves quality
C. Decreases systemic toxicity (Correct Answer)
D. Decreases pain at the injection site

Explanation: **Explanation:** The addition of sodium bicarbonate (alkalization) to local anesthetics (LAs) is a common clinical practice based on the pH-dependent behavior of these drugs. Local anesthetics are weak bases, usually prepared as acidic solutions (pH 4–6) to maintain stability and solubility. **Why "Decreases systemic toxicity" is the correct answer:** Alkalization **does not** decrease systemic toxicity. In fact, by increasing the concentration of the non-ionized (lipid-soluble) form of the drug, alkalization can lead to faster systemic absorption into the bloodstream. Systemic toxicity (LAST) is primarily determined by the total dose administered, the vascularity of the injection site, and the use of vasoconstrictors like adrenaline, rather than the pH of the solution. **Analysis of other options:** * **Speeds the onset:** LAs exist in equilibrium between ionized (charged) and non-ionized (uncharged) forms. Only the non-ionized form can cross the lipid nerve membrane. Adding bicarbonate increases the pH, shifting the equilibrium toward the non-ionized form, allowing faster penetration of the nerve sheath and quicker onset of block. * **Improves quality:** By increasing the amount of base available to diffuse into the nerve, alkalization can result in a more profound and dense sensory/motor blockade. * **Decreases pain at injection site:** The acidic nature of commercial LA solutions (especially those containing epinephrine) causes a "stinging" sensation upon injection. Neutralizing the pH with bicarbonate significantly reduces this discomfort. **High-Yield NEET-PG Pearls:** * **Standard Ratio:** Usually 1 mL of 8.4% Sodium Bicarbonate is added to 10 mL of Lidocaine. * **Bupivacaine Caution:** Alkalization of Bupivacaine is limited because it tends to precipitate at a pH above 6.5–7.0. * **Infected Tissues:** LAs work poorly in infected (acidic) tissues because the acidic environment ionizes the drug, preventing it from crossing the nerve membrane.

Question 64: A 24-year-old woman presents for labor and delivery. Caudal anesthesia is administered to block spinal nerves in the epidural space. Local anesthetic agents are most likely injected through which of the following openings?

A. Intervertebral Foramen
B. Sacral Hiatus (Correct Answer)
C. Vertebral canal
D. Dorsal Sacral Foramen

Explanation: **Explanation:** **Correct Answer: B. Sacral Hiatus** **Concept:** Caudal anesthesia is a type of epidural anesthesia where local anesthetic is injected into the **sacral canal** via the **sacral hiatus**. The sacral hiatus is a U-shaped or V-shaped opening at the distal end of the sacrum, formed by the failure of the fifth sacral laminae to fuse in the midline. It is covered by the sacrococcygeal ligament. This route provides access to the epidural space containing the sacral and coccygeal nerve roots. It is commonly used in pediatric surgery and for obstetric procedures (labor and delivery) to provide analgesia for the "saddle area" (S2–S4). **Analysis of Incorrect Options:** * **A. Intervertebral Foramen:** These are lateral openings between adjacent vertebrae through which spinal nerves exit. They are not the primary site of injection for regional blocks. * **C. Vertebral Canal:** This is the general longitudinal space containing the spinal cord and its coverings. While the sacral canal is a continuation of the vertebral canal, the specific "opening" used for needle entry in caudal blocks is the hiatus. * **D. Dorsal Sacral Foramen:** These are the four pairs of openings on the posterior surface of the sacrum through which the posterior rami of sacral nerves exit. They are used for transsacral nerve blocks but not for caudal epidural anesthesia. **High-Yield NEET-PG Pearls:** * **Landmarks:** The sacral hiatus is located between the **sacral cornua** (bony prominences representing the inferior articular processes of S5). * **Dural Sac:** In adults, the dural sac ends at the level of **S2**. In infants, it ends lower (around S3-S4), increasing the risk of accidental dural puncture during caudal blocks. * **Clinical Use:** Caudal blocks are the most common regional technique in **pediatric anesthesia** for infra-umbilical surgeries.

Question 65: In epidural anesthesia, where is the local anesthetic drug deposited?

A. Intrathecal space
B. Extradural space (Correct Answer)
C. Paraspinal space
D. Intervertebral space

Explanation: **Explanation:** **1. Why Option B is Correct:** Epidural anesthesia involves the injection of local anesthetic into the **extradural space** (also known as the epidural space). This potential space lies between the **dural mater** (the outermost layer of the meninges) and the **ligamentum flavum**, which lines the vertebral canal. The drug acts primarily on the spinal nerve roots as they exit the dura and pass through the intervertebral foramina. **2. Why Other Options are Incorrect:** * **Option A (Intrathecal space):** This is the subarachnoid space (between the arachnoid and pia mater) containing CSF. Depositing drugs here results in **Spinal Anesthesia**, which requires a much smaller volume of anesthetic compared to epidural anesthesia. * **Option C (Paraspinal space):** This refers to the area alongside the spinal column. While used for paravertebral blocks, it is not the site for central neuraxial blockade like epidural anesthesia. * **Option D (Intervertebral space):** This is an anatomical landmark (the gap between vertebrae) used as a point of entry for the needle, but it is not the physiological space where the drug is deposited to achieve anesthesia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Loss of Resistance (LOR) Technique:** The most common method to identify the epidural space (using air or saline). * **Hanging Drop Method:** Utilizes the negative pressure of the epidural space to identify correct needle placement. * **Site of Action:** The primary site of action is the **spinal nerve roots**; a secondary site is the paravertebral nerves. * **Test Dose:** A small dose of local anesthetic with adrenaline (e.g., 3ml of 1.5% Lignocaine with 1:200,000 adrenaline) is used to rule out accidental intravascular or intrathecal injection. * **Segmental Block:** Unlike spinal anesthesia, epidural anesthesia allows for a "segmental block," where only specific dermatomes are anesthetized.

Question 66: In epidural analgesia, morphine acts by acting on which structure?

A. Substantia gelatinosa (Correct Answer)
B. Axons
C. Ventral horn
D. Sensory nerve

Explanation: **Explanation:** The correct answer is **Substantia gelatinosa (Option A)**. **Mechanism of Action:** When morphine is administered into the epidural space, it crosses the dura mater and enters the cerebrospinal fluid (CSF) to reach the spinal cord. Its primary site of action is the **Substantia Gelatinosa (Rexed Lamina II)** located in the **dorsal horn** of the spinal cord. Morphine binds to pre-synaptic and post-synaptic **mu (μ) opioid receptors** here, inhibiting the release of excitatory neurotransmitters (like Substance P and Glutamate) from primary afferent nociceptors. This modulates and suppresses the transmission of pain signals before they ascend to the brain. **Analysis of Incorrect Options:** * **B. Axons:** Morphine does not possess local anesthetic properties; it does not block sodium channels or interfere with axonal conduction. * **C. Ventral horn:** The ventral horn is primarily responsible for motor output. Opioids act on the sensory processing areas (dorsal horn), which is why they provide analgesia without causing motor blockade. * **D. Sensory nerve:** While opioids can have minor peripheral effects, the clinical efficacy of epidural morphine is specifically due to its central action on the spinal cord receptors, not the peripheral sensory nerve fibers. **High-Yield Facts for NEET-PG:** * **Lipid Solubility:** Morphine has **low lipid solubility** (hydrophilic). This results in a slow onset, long duration of action, and a risk of **delayed respiratory depression** (6–24 hours) due to the cephalad (upward) spread of the drug in the CSF. * **Site of Action:** Always remember: **Opioids = Dorsal Horn (Substantia Gelatinosa)**; **Local Anesthetics = Nerve Roots/Axons.** * **Side Effects:** Common side effects of neuraxial morphine include pruritus (most common), urinary retention, and nausea.

Question 67: Sciatic nerve blockade provides sensory loss of which area?

A. Anterior and lateral thigh
B. Posterior thigh and majority of the leg below the knee (Correct Answer)
C. Medial and posterior thigh
D. Medial leg below the knee

Explanation: **Explanation:** The **Sciatic Nerve (L4–S3)** is the largest nerve in the human body. It provides motor innervation to the posterior thigh muscles (hamstrings) and all muscles below the knee. Sensorially, it supplies the **posterior thigh** (via the posterior cutaneous nerve of the thigh, which often travels with it) and the **entire leg below the knee**, with the notable exception of the medial strip. * **Why Option B is correct:** After leaving the pelvis, the sciatic nerve descends the posterior thigh. At the popliteal fossa, it divides into the tibial and common peroneal nerves. Together, these branches provide sensory coverage to the skin of the posterior thigh, the lateral leg, and the entire foot (except the medial arch). * **Why Option A is incorrect:** The **Anterior and Lateral thigh** are supplied by the **Femoral nerve** and the **Lateral Femoral Cutaneous nerve**, respectively (branches of the Lumbar Plexus). * **Why Option C is incorrect:** While the sciatic nerve covers the posterior thigh, the **Medial thigh** is supplied by the **Obturator nerve**. * **Why Option D is incorrect:** The **Medial leg below the knee** (and the medial foot) is supplied by the **Saphenous nerve**, which is the terminal sensory branch of the **Femoral nerve**. This is a classic "trap" in exams. **High-Yield Clinical Pearls for NEET-PG:** 1. **Complete Leg Block:** To achieve complete anesthesia below the knee, a Sciatic nerve block must be combined with a **Saphenous nerve block** to cover the medial leg. 2. **Anatomical Landmark:** The sciatic nerve is most commonly blocked using the **Labat approach** (Classic posterior approach), identifying the greater trochanter and the posterior superior iliac spine (PSIS). 3. **Foot Surgery:** For surgeries involving the foot and ankle, the Sciatic nerve block is the gold standard.

Question 68: Which of the following local anesthetics should be avoided in spinal anesthesia?

A. Mepivacaine
B. Prilocaine
C. Bupivacaine
D. Chlorprocaine (Correct Answer)

Explanation: **Explanation:** The correct answer is **Chlorprocaine**. Historically, Chlorprocaine was avoided in spinal anesthesia due to reports of permanent neurological deficits (Cauda Equina Syndrome). This neurotoxicity was primarily attributed to the preservative **sodium bisulfite** and the low pH of the formulation used in the 1980s, rather than the drug itself. While preservative-free formulations are now available and used for short procedures, for the purpose of standard examinations like NEET-PG, Chlorprocaine remains the classic answer for a local anesthetic traditionally avoided/associated with neurotoxicity in the subarachnoid space. **Analysis of Options:** * **Mepivacaine (A):** An intermediate-acting amide used for spinal anesthesia. While it has a higher incidence of Transient Neurological Symptoms (TNS) compared to bupivacaine, it is not contraindicated. * **Prilocaine (B):** Frequently used for short-duration spinal anesthesia in Europe. Its main systemic side effect is methemoglobinemia, but it is safe for spinal use. * **Bupivacaine (C):** The **gold standard** and most commonly used local anesthetic for spinal anesthesia due to its potency, long duration, and minimal sensory-motor dissociation. **High-Yield Clinical Pearls for NEET-PG:** * **Toxicity:** The neurotoxicity of older Chlorprocaine was due to **Sodium Bisulfite**. * **Hyperbaric Solutions:** Most spinal anesthetics (like Bupivacaine 0.5%) are made "heavy" by adding **Dextrose** to control the spread via gravity. * **TNS Risk:** Lidocaine has the highest association with Transient Neurological Symptoms (TNS) after spinal anesthesia. * **Potency:** Bupivacaine > Lidocaine > Procaine.

Question 69: Intravenous regional anesthesia (IVRA) is contraindicated in which of the following conditions?

A. Cancer of the hematogenous system
B. Sickle cell disease
C. Coagulopathy (Correct Answer)
D. Hypertension

Explanation: **Explanation:** Intravenous Regional Anesthesia (IVRA), also known as a **Bier Block**, involves the administration of local anesthetics into a vein of a limb that has been exsanguinated and isolated from the systemic circulation using a pneumatic tourniquet. **Why Coagulopathy is the Correct Answer:** The primary contraindication among the choices is **Coagulopathy**. IVRA requires the placement of an intravenous cannula in the distal part of the limb. In patients with severe bleeding disorders or those on potent anticoagulants, the risk of hematoma formation at the puncture site is high. More importantly, if the tourniquet fails or is released prematurely, the systemic bolus of local anesthetic (and potentially any adjunctive drugs) cannot be easily managed if there is a risk of internal hemorrhage or uncontrollable bleeding from the procedure site. **Analysis of Incorrect Options:** * **Sickle Cell Disease:** While some older texts listed this as a relative contraindication due to concerns about stasis and acidosis under the tourniquet triggering a sickling crisis, modern practice allows IVRA with meticulous exsanguination and limited tourniquet time. It is not an absolute contraindication compared to coagulopathy. * **Cancer of the hematogenous system:** This is not a standard contraindication for IVRA unless it results in severe thrombocytopenia (leading back to coagulopathy). * **Hypertension:** While uncontrolled hypertension is a precaution (as it may require higher tourniquet pressures to occlude arterial flow), it is not a contraindication. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Prilocaine (0.5%) is preferred due to its high therapeutic index. **Bupivacaine is strictly contraindicated** due to cardiotoxicity. * **Tourniquet Time:** Minimum 20 minutes (to prevent systemic toxicity) and maximum 90–120 minutes (to prevent nerve injury/ischemia). * **Mechanism of Action:** Local anesthetic diffuses from the vascular bed into the adjacent nerve trunks and endings. * **Absolute Contraindications:** Patient refusal, allergy to local anesthetics, and severe crush injuries (where vascular integrity is compromised).

Question 70: Transient Bell's palsy during mandibular nerve block after injection of local anesthesia occurs due to needle piercing into which structure?

A. Maxillary artery
B. Buccinator muscle
C. Temporalis muscle
D. Parotid gland (Correct Answer)

Explanation: **Explanation:** The occurrence of transient Bell’s palsy (facial nerve paralysis) following an inferior alveolar nerve block (mandibular nerve block) is a known complication caused by the **accidental deposition of local anesthetic into the capsule of the parotid gland.** **Why the Parotid Gland is the Correct Answer:** The parotid gland is situated posteriorly to the ramus of the mandible. If the needle is inserted too far posteriorly or if the bony contact with the medial aspect of the ramus is not maintained, the needle can pierce the parotid capsule. The **Facial Nerve (CN VII)** traverses through the substance of the parotid gland. Local anesthetic deposited here diffuses and blocks the motor branches of the facial nerve, leading to temporary ipsilateral facial drooping and inability to close the eyelid. **Analysis of Incorrect Options:** * **Maxillary Artery:** Piercing this would lead to a hematoma or intravascular injection (systemic toxicity), not motor nerve paralysis. * **Buccinator Muscle:** This muscle is pierced during the initial phase of the block; however, it does not contain the facial nerve trunk. * **Temporalis Muscle:** The tendon of the temporalis is a landmark for the injection (coronoid notch), but it is not related to the path of the facial nerve. **Clinical Pearls for NEET-PG:** * **Prevention:** Always ensure the needle tip makes **contact with bone** (medial ramus) before injecting to ensure you are anterior to the parotid gland. * **Management:** The palsy is **transient** and resolves as the anesthetic wears off (usually 1–3 hours). The most critical management step is **eye protection** (patching or manual closure) to prevent corneal drying/abrasion since the patient cannot blink. * **Differential:** If the palsy is permanent or delayed, it may be due to viral reactivation or trauma, rather than simple anesthetic diffusion.

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

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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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