Spinal Anesthesia — MCQs

10 questions

The duration of spinal anaesthesia is based directly on:

False statement about post-dural puncture headache (PDPH):

A resident at the emergency department is preparing for a lumbar puncture in a 26 years old female with suspected subarachnoid bleeding. Although she presented with altered sensorium, CT brain was found to be normal. During LP, which structure is pierced after the spinal needle crosses interspinous ligament?

All of the following are complications of epidural anaesthesia, EXCEPT:

All are pierced in Lumbar Puncture except:

A patient undergoing a minor surgical procedure is given lignocaine injection. Assertion: Local anaesthetics act by blocking nerve conduction. Reason: Small fibers and non-myelinated fibers are blocked more easily than large myelinated fibers.

In spinal anesthesia, the drug is deposited between

All are absolute contraindication of neuraxial anaesthesia except:

Which is false regarding post dural puncture headache?

Q10

The following position of the patient is maintained during \qquad anaesthesia:

Spinal Anesthesia Indian Medical PG Practice Questions and MCQs

Question 1: The duration of spinal anaesthesia is based directly on:

A. Height
B. Total body fat
C. Dose (Correct Answer)
D. Age

Explanation: ***Dose*** - The **total mass** (dose) of the local anesthetic administered directly influences the number of nerve fibers blocked and the duration of block. - A higher dose of a given local anesthetic generally leads to a **longer duration** of action in spinal anesthesia. *Height* - While patient height can influence the **spread** of spinal anesthesia due to differences in spinal column length, it does not directly determine the **duration** of the block. - The **volume** of the injectate, rather than the patient's height alone, affects the cranial spread of the anesthetic. *Total body fat* - Total body fat has **minimal direct impact** on the duration of spinal anesthesia since local anesthetics are injected directly into the cerebrospinal fluid, largely bypassing systemic fat distribution initially. - **Lipid solubility** of the drug affects its potency and duration within the neuraxis, not external body fat. *Age* - **Age** can influence the **spread** and **onset** of spinal anesthesia due to changes in cerebrospinal fluid volume and spinal cord compliance, but it is not the primary determinant of **duration**. - Older patients may experience a greater spread for a given dose, but the primary factor for duration remains the total drug dose.

Question 2: False statement about post-dural puncture headache (PDPH):

A. Commonly occipito-frontal in location
B. Onset of headache is usually 12-72 hours following procedure
C. Breach of dura
D. Headache is relieved in sitting standing position (Correct Answer)

Explanation: ***Headache is relieved in sitting standing position*** - This statement is **false** because a cardinal feature of PDPH is that the headache is **worse in the upright position** (sitting or standing) and **relieved by lying flat**. - The postural nature of the headache is due to the continued leakage of CSF, leading to reduced intracranial pressure, which is exacerbated by gravity when upright. *Commonly occipito-frontal in location* - PDPH typically presents as a headache that can be **holocranial**, **occipital**, or **frontal**, often radiating to the neck. - The location is due to changes in **intracranial pressure** affecting pain-sensitive structures like blood vessels and meninges. *Onset of headache is usually 12-72 hours following procedure* - The onset of PDPH is typically **delayed**, occurring in the vast majority of cases between **12 to 72 hours** after the dural puncture. - Although it can occur immediately or up to five days later, this delayed presentation is characteristic. *Breach of dura* - PDPH is a direct consequence of the intentional or accidental **breach of the dura mater** during procedures like spinal anesthesia or lumbar puncture. - This breach allows for continuous leakage of **cerebrospinal fluid (CSF)**, leading to a reduction in intracranial pressure, which causes the headache.

Question 3: A resident at the emergency department is preparing for a lumbar puncture in a 26 years old female with suspected subarachnoid bleeding. Although she presented with altered sensorium, CT brain was found to be normal. During LP, which structure is pierced after the spinal needle crosses interspinous ligament?

A. Supra/inter spinous ligament
B. Skin
C. Sub cutaneous fascia
D. Dura mater
E. Arachnoid mater
F. Ligamentum flava (Correct Answer)

Explanation: The enriched explanation is the original text provided because none of the references were sufficiently relevant to the anatomy of a lumbar puncture. Ligamentum flava - After passing the interspinous ligament, the next significant structure pierced by the spinal needle during a lumbar puncture is the ligamentum flava. - This ligament is crucial for stabilizing the vertebral column and is located anterior to the interspinous ligament, connecting the laminae of adjacent vertebrae. *Supra/inter spinous ligament* - The question explicitly states that the needle has already crossed the interspinous ligament, making this an incorrect choice for the next structure. - The supraspinous ligament lies superficial to the interspinous ligament, both of which are encountered before the ligamentum flava. *Skin* - The skin is the very first layer pierced when performing a lumbar puncture. - The question is asking what is pierced after the interspinous ligament, not what is pierced first. *Sub cutaneous fascia* - The subcutaneous fascia is located directly beneath the skin and is encountered very early in the lumbar puncture procedure. - It lies superficial to all ligaments of the vertebral column, including the interspinous ligament. *Dura mater* - The dura mater is pierced after the ligamentum flava. - It is the outermost meningeal layer, which, once penetrated, indicates entry into the epidural space, followed by the subarachnoid space. *Arachnoid mater* - The arachnoid mater is a thin, delicate membrane that lies immediately deep to the dura mater. - It is pierced almost simultaneously with the dura mater, and its penetration allows entry into the subarachnoid space where CSF is collected. *Return of CSF* - The return of CSF is the result of successfully traversing all necessary layers and entering the subarachnoid space. - It is not an anatomical structure that is pierced itself, but rather the clinical endpoint of the procedure.

Question 4: All of the following are complications of epidural anaesthesia, EXCEPT:

A. Urinary retention
B. Total spinal analgesia
C. Hypopnoea
D. Hypertension (Correct Answer)

Explanation: ***Hypertension*** - Epidural anesthesia commonly causes **vasodilation** and a subsequent drop in **blood pressure** (hypotension), not hypertension, due to sympathetic blockade. - While hypertension can occur due to pain or anxiety during the procedure, it is not a direct physiological complication of the epidural anesthetic itself. *Urinary retention* - Epidural anesthesia can affect the nerves controlling the **bladder**, leading to temporary **urinary retention**. - This is a common complication, often requiring catheterization until the epidural wears off. *Total spinal analgesia* - This occurs if the epidural needle inadvertently punctures the **dura** and a large dose of local anesthetic is injected into the **subarachnoid space**. - It results in widespread **sensory and motor blockade**, potentially leading to respiratory arrest and hemodynamic collapse. *Hypopnoea* - High epidural blocks or accidental **intrathecal administration** can cause paralysis of **intercostal muscles** and the diaphragm. - This can lead to **respiratory depression** (hypopnoea) or even apnea, necessitating ventilatory support.

Question 5: All are pierced in Lumbar Puncture except:

A. Interspinous Ligament
B. Ligamentum Flavum
C. Supraspinous ligament
D. Posterior longitudinal ligament (Correct Answer)

Explanation: ***Posterior longitudinal ligament*** - The **posterior longitudinal ligament** runs along the **posterior surface of the vertebral bodies**, forming the **anterior wall of the spinal canal**. - A lumbar puncture needle **does not reach this ligament** as it enters from the **posterior aspect** of the spinal canal. *Interspinous Ligament* - The **interspinous ligament** is located between the **spinous processes of adjacent vertebrae**. - It is **pierced** during a lumbar puncture as the needle advances through the posterior elements to reach the spinal canal. *Ligamentum Flavum* - The **ligamentum flavum** connects the **laminae of adjacent vertebrae**. - This ligament is **pierced** by the needle just before it enters the epidural space and then the subarachnoid space during a lumbar puncture. *Supraspinous ligament* - The **supraspinous ligament** runs along the tips of the **spinous processes**. - It is the **first ligament pierced** by the needle as it enters the skin and subcutaneous tissue during a lumbar puncture.

Question 6: A patient undergoing a minor surgical procedure is given lignocaine injection. Assertion: Local anaesthetics act by blocking nerve conduction. Reason: Small fibers and non-myelinated fibers are blocked more easily than large myelinated fibers.

A. Assertion is false, but Reason is true
B. Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion (Correct Answer)
C. Both Assertion and Reason are true, and Reason is the correct explanation for Assertion
D. Assertion is true, but Reason is false

Explanation: ***Both Assertion and Reason are true, and Reason is NOT the correct explanation for Assertion*** - The **Assertion** is true: Local anesthetics (like lignocaine) block nerve conduction by inhibiting **voltage-gated sodium channels**, preventing the depolarization necessary for action potential propagation - The **Reason** is also true: Small diameter and non-myelinated fibers (like C and Aδ pain fibers) are blocked more easily than large myelinated fibers (like Aα motor fibers), which explains the **differential blockade** pattern seen clinically - However, the **Reason does NOT explain WHY** local anesthetics block nerve conduction—it describes **WHICH** nerve fibers are blocked preferentially. The mechanism of blocking conduction is sodium channel inhibition, not fiber size selectivity - The differential sensitivity is a consequence of fiber characteristics (surface area-to-volume ratio, number of nodes of Ranvier), not the explanation for the blocking mechanism itself *Both Assertion and Reason are true, and Reason is the correct explanation for Assertion* - While both statements are individually true, the Reason does not explain the **mechanism** by which local anesthetics block nerve conduction - The Reason addresses fiber **selectivity**, which is a separate pharmacological property from the **mechanism of action** (sodium channel blockade) *Assertion is true, but Reason is false* - The Assertion is demonstrably true—local anesthetics block nerve conduction - The Reason is also true—this is well-established pharmacology: autonomic (small) > sensory (medium) > motor (large) fiber blockade sequence *Assertion is false, but Reason is true* - The Assertion is fundamentally correct and represents the primary pharmacological action of local anesthetics - Blocking nerve conduction is the therapeutic goal of local anesthetic administration

Question 7: In spinal anesthesia, the drug is deposited between

A. Dura and arachnoid
B. Pia and arachnoid (Correct Answer)
C. Dura and vertebra
D. Into the cord substance

Explanation: ***Pia and arachnoid*** - Spinal anesthesia involves injecting anesthetic into the **subarachnoid space**, which is the anatomical region located between the pia mater and the arachnoid mater. - This space contains **cerebrospinal fluid (CSF)**, allowing the anesthetic to mix and spread, blocking nerve impulses at the spinal cord roots. *Dura and arachnoid* - The space between the dura mater and arachnoid mater is the **subdural space**, and it is typically a potential space rather than an actual one for anesthetic injection. - Injecting here would lead to a **subdural block**, which is distinct from spinal anesthesia and has different characteristics and risks. *Dura and vertebra* - The space between the dura mater and the vertebral canal is the **epidural space**. - **Epidural anesthesia** involves injecting anesthetic into this space, but it is distinct from spinal anesthesia as the drug does not mix directly with CSF and requires a larger dose. *Into the cord substance* - Injecting anesthetic directly into the **spinal cord substance** (intrathecal injection into the cord) would be highly dangerous and cause severe neurological damage. - Anesthetic drugs exert their effect by blocking nerve roots as they exit the spinal cord, not by acting directly on the cord parenchyma.

Question 8: All are absolute contraindication of neuraxial anaesthesia except:

A. Spinal deformity (Correct Answer)
B. Local infection of site
C. Raised Intracranial pressure
D. Coagulopathy

Explanation: ***Spinal deformity*** - While a **spinal deformity** can make neuraxial anesthesia technically challenging, it is generally considered a **relative contraindication**, not an absolute one. - The procedure can still be performed by an experienced anesthetist, potentially with imaging guidance, if the benefits outweigh the risks. *Local infection of site* - A **local infection** at the needle insertion site is an **absolute contraindication** due to the high risk of spreading infection into the central nervous system, leading to potentially life-threatening conditions such as **meningitis** or **epidural abscess**. - Introducing bacteria into the cerebrospinal fluid or epidural space is a severe complication to avoid. *Raised Intracranial pressure* - **Raised intracranial pressure (ICP)** is an **absolute contraindication** because puncturing the dura mater can lead to a rapid decrease in cerebrospinal fluid (CSF) pressure, resulting in brain herniation. - This sudden pressure gradient can cause devastating neurological injury or death. *Coagulopathy* - **Coagulopathy**, whether intrinsic (e.g., hemophilia) or iatrogenic (e.g., anticoagulation), is an **absolute contraindication** to neuraxial anesthesia. - The primary concern is the formation of an **epidural or spinal hematoma**, which can compress the spinal cord and lead to permanent neurological damage, including paralysis.

Question 9: Which is false regarding post dural puncture headache?

A. Definitive cure is obtained with epidural blood patch
B. Head ache is aggravated by sitting and relieved by lying down
C. Incidence is reduced by pencil point spinal needles
D. Longer the duration anesthesia , greater will be the chance of developing PDPH (Correct Answer)

Explanation: ***Longer the duration anesthesia , greater will be the chance of developing PDPH*** - This statement is **false** because the duration of epidural or spinal anesthesia does **not directly correlate** with the incidence of post-dural puncture headache (PDPH). - PDPH is primarily caused by **cerebrospinal fluid (CSF) leakage** through the dural puncture site, which is related to needle size, type, and technique, rather than the length of time anesthetic drugs are administered. *Definitive cure is obtained with epidural blood patch* - An **epidural blood patch** is considered the most effective and often definitive treatment, providing relief in over 90% of cases. - It works by injecting autologous blood into the epidural space, which then clots and seals the CSF leak. *Head ache is aggravated by sitting and relieved by lying down* - This is a **classic symptom** of PDPH, as CSF pressure decreases in the upright position, causing traction on pain-sensitive structures like blood vessels and nerves. - Lying flat reduces this traction, leading to symptomatic relief. *Incidence is reduced by pencil point spinal needles* - **Pencil-point needles** (e.g., Sprotte or Whitacre) push aside dural fibers rather than cutting them, leading to a smaller and more self-sealing dural defect. - This design significantly **reduces the risk** of CSF leakage and subsequent PDPH compared to cutting-tip needles (e.g., Quincke).

Question 10: The following position of the patient is maintained during \qquad anaesthesia:

A. Spinal anaesthesia (Correct Answer)
B. Bier's block
C. Caudal anaesthesia
D. Stellate block

Explanation: ***Spinal anaesthesia*** - The image depicts the **lateral decubitus position** with the patient's back arched, which is a common position for administering **spinal anesthesia**. - This position helps to open the intervertebral spaces, making it easier to insert the needle into the **subarachnoid space** for drug delivery. *Bier's block* - A Bier's block (intravenous regional anesthesia) involves isolating the blood flow to a limb with a **tourniquet** and injecting local anesthetic directly into a peripheral vein. - The patient typically lies supine, and the limb to be anesthetized is elevated to exsanguinate it before tourniquet inflation. *Caudal anaesthesia* - Caudal anesthesia involves injecting local anesthetic into the **caudal epidural space** via the sacral hiatus. - Patients are usually positioned in the **prone** position or **lateral decubitus** with hips flexed to facilitate access to the sacral hiatus. *Stellate block* - A stellate ganglion block is performed to block the sympathetic nerves in the neck, typically for conditions affecting the head, neck, or upper extremities. - The patient is typically positioned **supine** with the neck slightly extended, allowing access to the anterior cervical spine area.

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