Anesthesia for Neurovascular Procedures — MCQs
Anesthetic agent contraindicated in raised ICT is?
Which is wrong regarding somato sensory evoked potentials (SSEP)?
All of the following decrease cerebral blood flow and intracranial pressure except:
All of the following are indicators of adequacy of pre-operative resuscitation except
Increased ICP is shown by
Which method is commonly used to assess the depth of anesthesia?
Vasopressor of choice in hypotension produced during subarachnoid block is
A patient comes to the casualty with a severe headache. His BP was found to be 160/100 mmHg. CT scan revealed a subarachnoid hemorrhage. What is the next best step in the management of this patient?
Which inhalational agent increases intracranial pressure most significantly?
A 70 kg young athlete was planned for surgery. During anesthesia, vecuronium was not available, so repeated doses of succinylcholine were given intermittently up to 640 mg. During recovery, the patient was not able to spontaneously respire and move limbs. What is the cause?
Anesthesia for Neurovascular Procedures Indian Medical PG Practice Questions and MCQs
Question 1: Anesthetic agent contraindicated in raised ICT is?
- A. Thiopentone
- B. Etomidate
- C. Ketamine (Correct Answer)
- D. Sevoflurane
Explanation: ***Ketamine*** - **Ketamine** is known to increase **cerebral blood flow** and metabolic rate, which can lead to a significant increase in **intracranial pressure (ICP)**. - This effect makes **ketamine** contraindicated in situations of elevated ICP, as it can worsen neurological outcomes. *Thiopentone* - **Thiopentone** is a barbiturate that typically causes a dose-dependent **decrease in cerebral blood flow** and **metabolic rate**, leading to a *reduction* in ICP. - It is often used to *lower* ICP in neurosurgical settings rather than being contraindicated. *Etomidate* - **Etomidate** also causes a **reduction in cerebral blood flow** and **cerebral metabolic rate**, leading to a *decrease* in ICP. - It is considered a relatively **hemodynamically stable** induction agent, making it suitable in many cases with neurological concerns. *Sevoflurane* - **Sevoflurane**, an inhaled anesthetic, can cause **cerebral vasodilation** at higher concentrations, potentially *increasing* ICP. - However, this effect is often *attenuated* by concurrent hyperventilation, and its overall impact on ICP is less pronounced than **ketamine's** and often manageable.
Question 2: Which is wrong regarding somato sensory evoked potentials (SSEP)?
- A. Can be used during spinal cord surgery to detect spinal cord damage
- B. Can be used to monitor CNS during intracranial surgery
- C. Can be used intraoperatively inside OT
- D. Is contraindicated under general anaesthesia (Correct Answer)
Explanation: ***Is contraindicated under general anaesthesia*** - This statement is incorrect because **somatosensory evoked potentials (SSEPs)** are routinely used under **general anesthesia** to monitor neurological function during surgery. - Anesthetic agents can affect SSEP waveforms (e.g., increased latency, decreased amplitude), but techniques exist to adjust for these effects and maintain monitoring utility. *Can be used during spinal cord surgery to detect spinal cord damage* - **SSEPs** are valuable for monitoring the integrity of the **dorsal columns** (sensory pathways) in the spinal cord during procedures that risk spinal cord injury. - A significant change in SSEP amplitude or latency can indicate impending or actual **spinal cord damage**, allowing for timely intervention. *Can be used to monitor CNS during intracranial surgery* - **SSEPs** can be used to monitor the cortical and subcortical sensory pathways during **intracranial surgeries**, especially those involving areas like the **somatosensory cortex** or brainstem. - This helps to detect and prevent iatrogenic injury to these critical sensory pathways. *Can be used intraoperatively inside OT* - **SSEPs** are a common form of **intraoperative neurophysiological monitoring (IONM)**. - They are actively used in the operating room during various surgical procedures to assess the functional integrity of sensory nerves, spinal cord, and brain.
Question 3: All of the following decrease cerebral blood flow and intracranial pressure except:
- A. Ketamine (Correct Answer)
- B. Thiopentone
- C. Propofol
- D. Etomidate
Explanation: ***Ketamine*** - Ketamine is an exception as it is known to **increase cerebral blood flow (CBF)** and **intracranial pressure (ICP)** due to its dissociative anesthetic properties. - It causes cerebral vasodilation and increased cerebral metabolic rate, making it generally avoided in patients with elevated ICP or head trauma. *Thiopentone* - Thiopentone (a barbiturate) is a potent cerebral vasoconstrictor that **decreases cerebral blood flow (CBF)** and **intracranial pressure (ICP)**. - It achieves this by reducing the cerebral metabolic rate of oxygen consumption (CMRO2), thus coupling metabolism and flow. *Propofol* - Propofol significantly **reduces cerebral blood flow (CBF)** and **intracranial pressure (ICP)** by causing widespread cerebral vasoconstriction. - Its rapid onset and offset, along with its neuroprotective properties, make it a favorable agent for neuroanesthesia. *Etomidate* - Etomidate is an imidazole derivative that causes a significant **reduction in cerebral blood flow (CBF)** and **intracranial pressure (ICP)** comparable to barbiturates. - It achieves this by reducing cerebral metabolic rate and causing cerebral vasoconstriction, without significantly altering systemic hemodynamics.
Question 4: All of the following are indicators of adequacy of pre-operative resuscitation except
- A. Hematocrit level
- B. Consciousness level
- C. C-reactive protein level (Correct Answer)
- D. Urine output
Explanation: ***C-reactive protein level*** - **C-reactive protein (CRP)** is an inflammatory marker and is not a direct indicator of the adequacy of pre-operative fluid and hemodynamic resuscitation. An elevated CRP suggests ongoing inflammation or infection, not necessarily a deficit in perfusion or hydration. - While inflammation can coincide with critical illness requiring resuscitation, CRP itself does not provide real-time information about **organ perfusion**, **oxygen delivery**, or **fluid status**. *Hematocrit level* - **Hematocrit** levels are crucial for assessing factors like **blood loss** and **hemoconcentration**, which directly impact the need for and adequacy of resuscitation. An increasing hematocrit can indicate hemoconcentration, while a decreasing hematocrit may suggest blood loss. - It helps guide decisions regarding **blood product transfusions** and overall fluid management. *Consciousness level* - The **level of consciousness** is a vital clinical indicator of **cerebral perfusion** and overall brain oxygenation. Deterioration can signal inadequate resuscitation and poor cerebral blood flow. - Improvements in consciousness level after interventions suggest improved **systemic perfusion** and oxygen delivery to the brain. *Urine output* - **Urine output** is a sensitive and widely used indicator of **renal perfusion** and overall systemic hydration status. Adequate urine output (e.g., >0.5 mL/kg/hr) suggests sufficient renal blood flow. - Low or absent urine output can indicate **hypovolemia**, **poor cardiac output**, or **renal hypoperfusion**, highlighting the need for further resuscitation.
Question 5: Increased ICP is shown by
- A. Reduction in GCS (Correct Answer)
- B. Pupil constriction (Miosis)
- C. Systemic hypotension
- D. Tachycardia
Explanation: ***Reduction in GCS*** - A **decrease in Glasgow Coma Scale (GCS)** score is a primary indicator of increased intracranial pressure (ICP) due to compromised brain function [1], [2]. - Increased ICP can lead to **cerebral ischemia** and neuronal damage, manifesting as altered consciousness and lower GCS scores [1]. *Pupil constriction (Miosis)* - **Miosis**, or pupil constriction, is typically associated with **pontine lesions** or **opioid use**, and rarely directly with increased ICP unless it specifically involves brainstem compression at the pontine level. - Increased ICP more commonly causes **pupil dilation (mydriasis)**, especially unilateral, due to compression of the oculomotor nerve (CN III) [1]. *Systemic hypotension* - **Systemic hypotension** is generally *not* a direct sign of increased ICP; rather, increased ICP often results in **systemic hypertension** as part of Cushing's triad. - Hypotension in the context of brain injury might indicate **spinal shock** or other systemic issues, but generally not directly elevated ICP. *Tachycardia* - **Tachycardia** is also *not* typically associated with increased ICP; instead, **bradycardia** (slow heart rate) is a hallmark sign, forming part of Cushing's triad. - Tachycardia might suggest **hypovolemia**, **pain**, or other systemic stressors, but not directly increased ICP.
Question 6: Which method is commonly used to assess the depth of anesthesia?
- A. Pulse oximeter
- B. End-tidal pCO2
- C. Bispectral index (Correct Answer)
- D. Acid blood gas analysis
Explanation: ***Bispectral index*** - The **Bispectral Index (BIS)** monitor processes electroencephalogram (EEG) signals to produce a numerical value, typically ranging from 0 (cortical silence) to 100 (fully awake). - A **BIS score between 40 and 60** is generally considered the therapeutic range for adequate surgical anesthesia, indicating a low probability of consciousness and recall. *Pulse oximeter* - A **pulse oximeter** measures **oxygen saturation** in the blood and **heart rate**, primarily indicating oxygen delivery to tissues. - It does not provide direct information about the brain's electrical activity or the patient's level of consciousness or anesthesia depth. *End-tidal pCO2* - **End-tidal pCO2 (EtCO2)** monitoring measures the partial pressure of **carbon dioxide** at the end of exhalation. - It reflects the adequacy of **ventilation** and pulmonary circulation but does not directly assess the depth of anesthesia. *Acid blood gas analysis* - **Arterial blood gas (ABG) analysis** provides detailed information about **blood pH**, oxygenation, and ventilation status. - While crucial for managing respiratory and metabolic conditions, it is an **invasive, intermittent test** and does not provide continuous, real-time feedback on anesthesia depth.
Question 7: Vasopressor of choice in hypotension produced during subarachnoid block is
- A. Ephedrine (Correct Answer)
- B. Mephentermine
- C. Epinephrine
- D. Dobutamine
Explanation: ***Ephedrine*** - **Ephedrine** is a sympathomimetic with both direct (on adrenergic receptors) and indirect (releasing norepinephrine) effects, causing vasoconstriction and increased heart rate, making it suitable for treating **hypotension** during **subarachnoid block**. - Its slower onset and longer duration of action compared to direct-acting vasopressors can be beneficial for sustained pressure support in this context. *Mephentermine* - While mephentermine is also an indirect-acting sympathomimetic used for hypotension, it has a **slower onset** and a more prolonged effect compared to ephedrine. - Ephedrine is generally preferred due to its faster action in acute settings like **subarachnoid block-induced hypotension**, where rapid correction is often required. *Epinephrine* - **Epinephrine** is a potent vasopressor with significant alpha and beta-adrenergic effects, leading to strong vasoconstriction and cardiac stimulation. - Its use might lead to **tachycardia** and arrhythmias, which are generally undesirable when milder agents like ephedrine can achieve the desired effect. *Dobutamine* - **Dobutamine** is primarily a beta-1 adrenergic agonist, meaning it mainly increases cardiac contractility and heart rate with minimal effect on systemic vascular resistance. - It is not the agent of choice for hypotension due to **vasodilation** from subarachnoid block, as it does not sufficiently address the primary problem of decreased vascular tone.
Question 8: A patient comes to the casualty with a severe headache. His BP was found to be 160/100 mmHg. CT scan revealed a subarachnoid hemorrhage. What is the next best step in the management of this patient?
- A. Nimodipine
- B. Angiography (Correct Answer)
- C. Surgery
- D. Fibrinolytic therapy
Explanation: ***Angiography*** - Following the diagnosis of **subarachnoid hemorrhage (SAH)** by CT scan, **cerebral angiography** is the next crucial step to identify the source of bleeding. - This procedure helps locate and characterize the **aneurysm** or other vascular malformations, which is essential for planning definitive treatment. *Nimodipine* - **Nimodipine** is a calcium channel blocker used to prevent and treat **vasospasm**, a common complication after SAH. - While important in SAH management, it is typically initiated after the source of bleeding has been identified and secured, or as an adjunct immediately after diagnosis, but not the *next best step* before identifying the source. *Surgery* - **Surgical clipping** or **endovascular coiling** are definitive treatments for ruptured aneurysms after SAH. - However, surgery is performed *after* the aneurysm has been identified and localized through angiography, making angiography the prerequisite next step. *Fibrinolytic therapy* - **Fibrinolytic therapy** is used to dissolve blood clots in conditions like ischemic stroke or myocardial infarction. - It is **contraindicated** in hemorrhagic stroke, including subarachnoid hemorrhage, as it would worsen the bleeding.
Question 9: Which inhalational agent increases intracranial pressure most significantly?
- A. Halothane (Correct Answer)
- B. Sevoflurane
- C. Isoflurane
- D. Desflurane
Explanation: ***Halothane*** - **Halothane** causes a greater increase in **cerebral blood flow** and thus **intracranial pressure (ICP)** compared to newer volatile anesthetics due to its more potent cerebral vasodilation. - Its use has largely declined due to concerns about its effects on ICP and potential for **hepatotoxicity**. *Sevoflurane* - While sevoflurane can cause **cerebral vasodilation** and increase ICP, its effect is generally less pronounced than halothane, especially when normocapnia is maintained. - It is often favored in neuroanesthesia due to its rapid onset and offset, allowing for quicker adjustments in anesthetic depth. *Isoflurane* - Isoflurane causes less cerebral vasodilation and a smaller increase in ICP compared to halothane, particularly at lower concentrations. - It maintains **cerebral vascular autoregulation** better than halothane, helping to preserve a more stable ICP. *Desflurane* - Desflurane also causes cerebral vasodilation and can increase ICP, but its effect is typically less significant than halothane. - Rapid increases in desflurane concentration can lead to sympathetic stimulation and transient increases in blood pressure, which can indirectly affect ICP.
Question 10: A 70 kg young athlete was planned for surgery. During anesthesia, vecuronium was not available, so repeated doses of succinylcholine were given intermittently up to 640 mg. During recovery, the patient was not able to spontaneously respire and move limbs. What is the cause?
- A. Phase II blockade (Correct Answer)
- B. Muscle weakness due to repeated fasciculations
- C. Undiagnosed muscular dystrophy
- D. Pseudocholinesterase deficiency
Explanation: **Phase II blockade** - Prolonged administration of **succinylcholine** (> 30-60 minutes or high cumulative doses) can lead to a shift from Phase I to **Phase II block**. - In Phase II block, the neuromuscular junction exhibits characteristics similar to a **nondepolarizing block**, including fade on train-of-four stimulation and post-tetanic potentiation, leading to prolonged paralysis. *Muscle weakness due to repeated fasciculations* - While succinylcholine initially causes **fasciculations** due to depolarization, prolonged paralysis is not directly explained by muscle weakness from repeated fasciculations alone. - Fasciculations are a transient early effect and do not account for the sustained paralysis seen with high-dose, repeated administration. *Undiagnosed muscular dystrophy* - While certain **neuromuscular disorders** can alter response to muscle relaxants, there is no information in the scenario to suggest pre-existing muscular dystrophy. - Administering a large amount of succinylcholine accounts for the prolonged paralysis without needing to invoke an undiagnosed condition. *Pseudocholinesterase deficiency* - A deficiency in **pseudocholinesterase** would lead to a prolonged initial Phase I block with a typical dose of succinylcholine due to impaired metabolism. - However, the scenario describes **repeated doses** adding up to a very high cumulative amount (640 mg), pushing the patient into a Phase II block even if pseudocholinesterase levels were normal.
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