Regional Anesthesia — MCQs

Regional Anesthesia Indian Medical PG Practice Questions and MCQs

Question 181: Which nerve fibers are blocked first during spinal anesthesia?

A. Motor
B. Autonomic (Correct Answer)
C. Somatic
D. Sensory

Explanation: ***Autonomic*** - **Autonomic fibers** are typically the **smallest** and **unmyelinated** or lightly myelinated, making them the most susceptible to local anesthetics due to their **high surface area-to-volume ratio**. - Their blockage mediates the observed **vasodilation** and **hypotension** seen early in spinal anesthesia. *Motor* - **Motor fibers** are generally **larger** and **more heavily myelinated** than autonomic fibers, requiring a higher concentration or longer exposure to local anesthetics for blockade. - While eventually blocked, leading to motor paralysis, this occurs after sympathetic blockade has been established. *Somatic* - The term **somatic** is a broad category that includes both **sensory** and **motor fibers**. While sensory fibers (pain and temperature) are blocked relatively early, motor fibers are blocked later. - Autonomic fibers are selectively blocked even before **A-delta** and **C fibers** (which transmit pain and temperature sensations). *Sensory* - Sensory fibers, particularly **A-delta** and **C fibers** responsible for pain and temperature, are blocked relatively early due to their smaller diameter compared to motor fibers. - However, **autonomic fibers** (B fibers), especially those mediating sympathetic outflow, are even smaller and are typically blocked first, leading to a sympathetic block before the full sensory block is established.

Question 182: A patient develops hypotension during spinal anesthesia. What is the first step in management?

A. Elevate the legs
B. Administer atropine
C. Administer intravenous fluids
D. Administer vasopressors (Correct Answer)

Explanation: ***Administer vasopressors*** - **Vasopressors** are the most effective initial treatment for hypotension during spinal anesthesia because they directly counteract the **vasodilation** caused by sympathetic blockade, rapidly increasing **vascular tone** and **blood pressure**. - This approach addresses the underlying physiologic mechanism of hypotension, which is primarily a loss of **systemic vascular resistance (SVR)**, rather than just volumetric depletion. *Administer intravenous fluids* - While fluid administration can help, it is often **insufficient** as the primary solution for the profound **vasodilation** seen with spinal anesthesia and may lead to **fluid overload** without adequately addressing the loss of **vascular tone**. - Significant amounts of fluids would be required to compensate for widespread **vasodilation**, making it a slower and less efficient first-line response compared to vasopressors. *Elevate the legs* - **Leg elevation** can provide a transient increase in central blood volume, but its effect is generally **mild** and **short-lived**, not reliably reversing severe hypotension caused by widespread **sympathetic blockade**. - This maneuver is a temporary measure and does not directly address the systemic **vasodilation** that is the hallmark of spinal-induced hypotension. *Administer atropine* - **Atropine** is primarily used to treat **bradycardia**, not hypotension, as it blocks **parasympathetic activity** to the heart, increasing heart rate. - Hypotension during spinal anesthesia is usually due to **vasodilation** and not primarily to **bradycardia**, unless the bradycardia is severe enough to significantly reduce **cardiac output**.

Question 183: A 55-year-old man with a history of ischemic heart disease is undergoing an elective knee replacement. Which regional anesthesia technique is preferred to minimize cardiovascular stress?

A. Femoral nerve block
B. General anesthesia
C. Spinal anesthesia (Correct Answer)
D. Epidural anesthesia

Explanation: **Spinal anesthesia** - **Spinal anesthesia** provides excellent surgical anesthesia and analgesia with a rapid onset, allowing for a reduction in systemic opioid use and minimizing changes in **hemodynamics** compared to general anesthesia. - It is particularly beneficial in patients with **ischemic heart disease** as it avoids the myocardial depressant effects of general anesthetics and the stress response associated with intubation. *Femoral nerve block* - A **femoral nerve block** primarily provides analgesia to the anterior thigh and knee but does not offer complete surgical anesthesia for a total knee replacement, often requiring supplementation. - It targets a more limited area and would not sufficiently reduce the overall **stress response** of major surgery in a patient with cardiac risk. *General anesthesia* - **General anesthesia** can induce significant hemodynamic fluctuations during induction and emergence, including decreases in blood pressure and increases in heart rate, which can be detrimental in patients with **ischemic heart disease**. - It requires the use of multiple systemic drugs that can have myocardial depressant effects and increase **myocardial oxygen demand**. *Epidural anesthesia* - While **epidural anesthesia** can provide good analgesia and surgical anesthesia, its onset is slower than spinal anesthesia and it typically requires larger doses of local anesthetics, which can lead to more gradual, but sometimes profound, changes in **hemodynamics**. - It also carries a slightly higher risk of complications such as **epidural hematoma** or infection compared to spinal anesthesia, though both are generally safe.

Question 184: A 60-year-old male with a history of obstructive sleep apnea (OSA) is scheduled for a total knee replacement. Which intraoperative management strategy is most appropriate for this patient?

A. Minimizing opioid analgesia
B. Ensuring adequate ventilation during anesthesia
C. Utilizing regional anesthesia for pain control (Correct Answer)
D. Using sedative agents cautiously

Explanation: ***Utilizing regional anesthesia for pain control*** - **Regional anesthesia** (e.g., spinal, epidural, or nerve blocks) is preferred in OSA patients as it reduces the need for systemic sedatives and opioids, thereby minimizing respiratory depression. - This approach helps maintain **airway patency** and respiratory drive, which is crucial given the patient's predisposition to apneic episodes. *Minimizing opioid analgesia* - While important, simply minimizing opioids alone may not be sufficient if other respiratory depressants are heavily used or if the patient's OSA is severe. - The goal is holistic respiratory management, where regional anesthesia offers a more comprehensive solution for pain control with fewer systemic respiratory side effects. *Ensuring adequate ventilation during anesthesia* - This is a fundamental aspect of any anesthetized patient, but for OSA patients, simply ensuring adequate ventilation during anesthesia (e.g., with controlled mechanical ventilation) does not address the risk of **postoperative respiratory depression** once the patient is extubated and in the recovery period. - The primary concern for OSA patients is the potential for airway obstruction and hypoventilation in the spontaneous breathing phase, especially with residual anesthetic effects. *Using sedative agents cautiously* - This is an important consideration as **sedative agents** can exacerbate OSA by relaxing upper airway muscles and depressing the respiratory drive. - However, regional anesthesia offers a more proactive approach by reducing the overall requirement for sedatives by providing effective pain control without systemic depressant effects.

Question 185: Which of the following is a contraindication for neuraxial anesthesia?

A. Severe hypovolemia (Correct Answer)
B. Mild hypertension
C. History of peptic ulcer disease
D. Controlled diabetes mellitus

Explanation: ***Severe hypovolemia*** - Neuraxial anesthesia causes **vasodilation** below the level of the block, which can significantly lower blood pressure. - In a patient with **severe hypovolemia**, this vasodilation can lead to a drastic and dangerous drop in blood pressure, compromising organ perfusion and potentially causing **cardiovascular collapse**. *Mild hypertension* - **Mild hypertension** is generally not a contraindication for neuraxial anesthesia and may even be considered an indication as it can help manage blood pressure. - The controlled decrease in blood pressure through vasodilation can be beneficial in some hypertensive patients. *History of peptic ulcer disease* - A history of **peptic ulcer disease** is not a contraindication for neuraxial anesthesia. - Neuraxial anesthesia primarily affects the nervous system and cardiovascular system, with no direct adverse impact on the gastrointestinal system that would contraindicate its use. *Controlled diabetes mellitus* - **Controlled diabetes mellitus** is not a contraindication for neuraxial anesthesia. - While uncontrolled diabetes can lead to complications such as neuropathy, neuraxial anesthesia can generally be safely performed in patients with well-managed diabetes.

Question 186: A 60-year-old patient undergoing surgery for a hip fracture is at high risk for thromboembolism. Which regional anesthesia technique can help reduce this risk?

A. Epidural anesthesia
B. Spinal anesthesia (Correct Answer)
C. Peripheral nerve block
D. General anesthesia

Explanation: ***Spinal anesthesia*** - **Spinal anesthesia** is associated with a reduced incidence of **postoperative deep vein thrombosis (DVT)** and **pulmonary embolism (PE)** compared to general anesthesia. - This effect is mediated by improved venous flow, reduced sympathetic tone, and modulation of coagulation factors. *Epidural anesthesia* - While epidural anesthesia can also reduce DVT risk compared to general anesthesia, it generally provides a less profound and slower onset of sympathetic block than spinal anesthesia. - The risk reduction in thromboembolism is often more significantly demonstrated with **spinal anesthesia** in hip fracture patients. *Peripheral nerve block* - A **peripheral nerve block** provides excellent analgesia for the surgical site but does not offer the systemic benefits of neuroaxial techniques (like spinal or epidural) in reducing overall thromboembolism risk. - It primarily addresses pain relief and does not significantly impact the hypercoagulable state or venous stasis associated with surgery. *General anesthesia* - **General anesthesia** itself can increase the risk of thromboembolism due to factors like immobility, sympathetic activation, and the inflammatory response to surgery. - It does not offer the protective benefits against thromboembolism that neuroaxial techniques provide.

Question 187: What is the most common side effect of spinal anesthesia?

A. Hypotension (Correct Answer)
B. Hypertension
C. Hyperglycemia
D. Hypoglycemia

Explanation: ***Hypotension*** - Spinal anesthesia blocks the **sympathetic nervous system**, leading to **vasodilation** and a decrease in systemic vascular resistance. - This reduction in vascular tone causes a drop in **blood pressure**, making hypotension the most common side effect. *Hypertension* - This is generally not a direct side effect of spinal anesthesia; in fact, the sympathetic blockade typically leads to the opposite effect. - If hypertension occurs, it often relates to other factors, such as pain or pre-existing conditions, not the anesthetic itself. *Hyperglycemia* - Spinal anesthesia does not directly cause an increase in blood glucose levels. - Stress responses to surgery can elevate glucose, but this is not specific to spinal anesthesia. *Hypoglycemia* - This is an extremely rare and unexpected side effect of spinal anesthesia. - Anesthetic agents generally do not significantly alter glucose metabolism in a way that would lead to hypoglycemia.

Question 188: Which of the following is a common complication associated with central neuraxial blocks?

A. Post-dural puncture headache (Correct Answer)
B. Hypertension
C. Bradycardia
D. Hyperglycemia

Explanation: ***Post-dural puncture headache*** - Is a common complication of **spinal or epidural blocks**, especially when the dural membrane is accidentally punctured. - It is characterized by a **frontal or occipital headache** that worsens in the upright position and improves when lying flat. *Hypertension* - Is generally **not a common complication** of central neuraxial blocks; rather, **hypotension** is a more frequent side effect due to sympathetic blockade. - While some patients may develop hypertension for other reasons, it is not directly attributable to the block itself. *Bradycardia* - Can occur during central neuraxial blocks, particularly with **high spinal blocks** leading to blockade of cardiac accelerator fibers. - While a potential side effect, it is **less common than post-dural puncture headache (PDPH)** and often treated rapidly with vagolytic agents. *Hyperglycemia* - Is **not a direct complication** of central neuraxial blocks. - Surgical stress or pre-existing conditions like diabetes are more likely causes of hyperglycemia in the perioperative period.

Question 189: Which of the following is a common complication of epidural analgesia?

A. Respiratory depression
B. Hypotension (Correct Answer)
C. Bradycardia
D. Urinary retention

Explanation: ***Hypotension*** - **Epidural analgesia** can cause **systemic vasodilation** due to the sympathetic blockade, leading to a decrease in **peripheral vascular resistance** and thus **hypotension**. - This effect is more pronounced with higher epidural levels and can be managed with intravenous fluids and **vasopressors**. *Respiratory depression* - While **opioids** used in epidural analgesia can cause **respiratory depression**, it is often **less common** and less severe when opioids are titrated carefully and combined with local anesthetics in the epidural space. - Significant **respiratory depression** is more commonly associated with systemic opioid administration or accidental intravenous injection during epidural placement. *Bradycardia* - **Bradycardia** is not a common isolated complication of epidural analgesia; however, it can occur in conjunction with profound **hypotension** or as part of a **vasovagal response**. - It is often managed with atropine or other sympathomimetics if clinically significant. *Urinary retention* - **Urinary retention** is a known side effect, particularly with **opioids** and local anesthetics, as they can impair bladder sensation and detrusor muscle function. - Although common, it is usually managed with catheterization and is typically **less acute** or life-threatening than profound hypotension.

Question 190: Which of the following is the MOST significant relative contraindication for neuraxial/regional anesthesia?

A. Hypertension
B. Diabetes
C. Renal disease
D. Sepsis (Correct Answer)

Explanation: ***Sepsis*** - **Sepsis** is the MOST significant relative contraindication for neuraxial/regional anesthesia due to the risk of spreading infection to the central nervous system, potentially leading to **meningitis** or an **epidural abscess**. - Systemic infection can also cause **coagulopathy**, increasing the risk of **spinal hematoma** which can cause permanent neurological deficits. *Hypertension* - While patients with uncontrolled hypertension may experience exaggerated drops in blood pressure with neuraxial blockade, it is not a direct contraindication if managed. - The primary concern is hemodynamic stability, which can often be controlled with appropriate medical management. *Renal disease* - Renal disease itself is not a direct contraindication, though severe renal impairment may affect the metabolism and excretion of local anesthetics, requiring dose adjustments. - Associated conditions like **uremic coagulopathy** in advanced renal failure would be a more significant concern, increasing the risk of bleeding. *Diabetes* - Diabetes is not a contraindication, but severe peripheral neuropathy from diabetes can make accurate assessment of dermatomal block difficult and may increase the risk of nerve injury. - Diabetic patients may also have autonomic neuropathy, making them more susceptible to hypotension following neuraxial anesthesia, but this can be managed.

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

Practice Questions

Continuous Peripheral Nerve Catheters

Practice Questions

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