Neuroanesthesia — MCQs
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A patient is scheduled for neurosurgery for posterior fossa tumor. During the surgery the BP crashes and Et CO2 suddenly decreases to zero. What is the most likely diagnosis?
A comatose patient after sustaining severe head injury has been admitted to the neurosurgical ICU. Which of the following parameters should ideally be maintained in this patient? 1. pCO2 = 4.5 - 5.0 kPa (33-38 mm Hg) 2. MAP = 80 - 90 mm of Hg 3. pO2 > 11 kPa (> 80 mm Hg) 4. Na+ < 130 meq/L
Anesthetic agent contraindicated in raised ICT is?
Which of the following is the best cerebroprotective drug?
Thiopentone has cerebroprotective effect because of –
All of the following decrease cerebral blood flow and intracranial pressure except:
Increased intracranial pressure occurs with:
Which of the following anaesthetic agents causes a rise in the Intracranial pressure:
Which of the following anesthetic agents may have cerebroprotective effect:
Which of the following drugs is contraindicated in a patient with raised intracranial pressure ?
Neuroanesthesia Indian Medical PG Practice Questions and MCQs
Question 21: A patient is scheduled for neurosurgery for posterior fossa tumor. During the surgery the BP crashes and Et CO2 suddenly decreases to zero. What is the most likely diagnosis?
- A. Venous air embolism (Correct Answer)
- B. Trauma to respiratory center
- C. Dislodgement of endotracheal tube
- D. Wearing off effect of inhalation anesthesia
Explanation: ***Venous air embolism*** - Neurosurgery in the **posterior fossa** often involves the **sitting position**, which creates a hydrostatic gradient favoring air entrainment into open veins from the surgical field, leading to **venous air embolism (VAE)**. - VAE classically presents with a sudden decrease in **end-tidal CO2 (EtCO2)** due to increased dead space, along with **hypotension** (BP crash) from cardiovascular collapse. *Trauma to respiratory center* - While trauma to the brainstem's respiratory center could cause respiratory arrest, it would primarily lead to **cessation of respiration**, not a sudden drop to zero in EtCO2 with accompanying hypotension, unless combined with severe cardiovascular compromise. - The sudden onset of both **BP crash** and **zero EtCO2** is more indicative of an acute circulatory or pulmonary event. *Dislodgement of endotracheal tube* - A dislodged endotracheal tube would lead to a sudden decrease (**or absence**) of EtCO2, but primarily due to **ventilation failure**. - While it could cause some degree of hypotension from hypoxia, a complete **BP crash** to zero is less likely to be the primary and immediate result compared to the profound cardiovascular effects of a large air embolism. *Wearing off effect of inhalation anesthesia* - The "wearing off effect" of inhalation anesthesia would typically lead to the patient **waking up and becoming more responsive**, with an **increase in blood pressure and heart rate**, not a sudden drop to zero in EtCO2 and a BP crash. - This scenario describes a **catastrophic complication**, not a normal physiological response to anesthetic metabolism.
Question 22: A comatose patient after sustaining severe head injury has been admitted to the neurosurgical ICU. Which of the following parameters should ideally be maintained in this patient? 1. pCO2 = 4.5 - 5.0 kPa (33-38 mm Hg) 2. MAP = 80 - 90 mm of Hg 3. pO2 > 11 kPa (> 80 mm Hg) 4. Na+ < 130 meq/L
- A. 2, 3 and 4
- B. 1, 2 and 4
- C. 1, 3 and 4
- D. 1, 2 and 3 (Correct Answer)
Explanation: ***1, 2 and 3*** - Maintaining **pCO2 between 4.5-5.0 kPa (33-38 mmHg)** helps optimize cerebral blood flow; values outside this range can cause vasoconstriction or vasodilation, affecting intracranial pressure (ICP). - A **mean arterial pressure (MAP) of 80-90 mmHg** ensures adequate cerebral perfusion pressure (CPP) and minimizes the risk of secondary brain injury from ischemia. - An **arterial partial pressure of oxygen (pO2) above 11 kPa (>80 mmHg)** is crucial to prevent cerebral hypoxia, which can exacerbate brain damage in severely injured patients. *2, 3 and 4* - This option correctly identifies the importance of maintaining adequate MAP and pO2 but incorrectly suggests a low sodium level. - A low **serum sodium (Na+) below 130 mEq/L (hyponatremia)** should be avoided in severe head injury as it can worsen cerebral edema and increase ICP. *1, 2 and 4* - While maintaining pCO2 and MAP within target ranges is essential, a **sodium level below 130 mEq/L (hyponatremia)** is detrimental and not an ideal parameter to maintain. - Hyponatremia can lead to further **brain swelling** and increased intracranial pressure. *1, 3 and 4* - This combination correctly identifies ideal pCO2 and pO2 targets but incorrectly includes **hyponatremia (Na+ < 130 mEq/L)** as a desirable parameter. - Severe hyponatremia can cause significant neurological complications including **seizures** and worsening cerebral edema.
Question 23: 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 24: Which of the following is the best cerebroprotective drug?
- A. Propofol
- B. Thiopentone (Correct Answer)
- C. Etomidate
- D. Ketamine
Explanation: ***Thiopentone*** - **Thiopentone** is a barbiturate that can significantly reduce cerebral metabolic rate for oxygen (**CMRO2**) and cerebral blood flow (**CBF**), leading to a reduction in intracranial pressure (**ICP**). - It achieves neuroprotection by decreasing brain metabolism, scavenging free radicals, and stabilizing neuronal membranes. *Propofol* - **Propofol** also reduces **CMRO2** and **CBF**, thus decreasing **ICP**, but its neuroprotective effects are less profound and consistent compared to barbiturates like thiopentone. - While it has some neuroprotective properties, such as antioxidant effects, it is not considered the **best** cerebroprotective agent, especially in severe cases where maximum cerebral protection is needed. *Etomidate* - **Etomidate** is known for its minimal cardiovascular effects and its ability to reduce **CMRO2** and **CBF**, which can lower **ICP**. - However, its use is limited by its potential to cause adrenal suppression with prolonged or repeated administration, making it less suitable for continuous cerebroprotection. *Ketamine* - **Ketamine** typically increases **CBF** and **CMRO2**, which can lead to an increase in **ICP**, making it generally unsuitable as a cerebroprotective agent in patients with elevated ICP or acute cerebral injury. - While it has analgesic and dissociative properties, its impact on cerebral hemodynamics often contraindicates its use in situations requiring brain protection.
Question 25: Thiopentone has cerebroprotective effect because of –
- A. Decrease cerebral metabolism (Correct Answer)
- B. Calcium channel blockage
- C. Reduction of vasospasm
- D. Free radical removal
Explanation: ***Decrease cerebral metabolism*** - Thiopentone significantly **reduces cerebral metabolic rate** of oxygen consumption (CMRO2) by depressing neuronal activity. - This reduction in metabolic demand makes the brain more resilient to **ischemic injury**, offering a cerebroprotective effect. *Calcium channel blockage* - While some anesthetic agents have calcium channel blocking properties, this is not the primary mechanism behind thiopentone's **cerebroprotective effects**. - Calcium channel blockers are more commonly used for conditions like **hypertension** or certain arrhythmias. *Reduction of vasospasm* - Thiopentone does not primarily act as a **vasodilator** or antispasmodic agent to directly reduce cerebral vasospasm. - Vasospasm reduction is often targeted by therapies like **nimodipine** in specific conditions like subarachnoid hemorrhage. *Free radical removal* - Although **barbiturates** may have some antioxidant properties, free radical scavenging is not the main mechanism for thiopentone's significant cerebroprotection. - The cerebroprotective effect is predominantly due to its **metabolic suppression**.
Question 26: 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 27: Increased intracranial pressure occurs with:
- A. Succinylcholine (Correct Answer)
- B. None of the options
- C. Rocuronium
- D. Vecuronium
Explanation: ***Succinylcholine*** - **Succinylcholine** is known to cause a transient increase in **intracranial pressure (ICP)** due to its fasciculations, which can increase cerebral blood flow and metabolic demand. - This effect is particularly relevant in patients with pre-existing elevated ICP or those at risk of brain herniation. *None of the options* - This option is incorrect because **succinylcholine** does indeed cause an increase in ICP, making one of the listed drugs relevant. *Rocuronium* - **Rocuronium** is a **nondepolarizing neuromuscular blocker** and typically does not significantly increase ICP; it is often considered safe for use in patients with intracranial pathology. - Its mechanism of action does not involve muscle fasciculations, which are the primary reason for ICP elevation with succinylcholine. *Vecuronium* - **Vecuronium** is also a **nondepolarizing neuromuscular blocker** and, like rocuronium, does not typically cause a significant increase in ICP. - It works by blocking acetylcholine receptors at the neuromuscular junction without stimulating them, thus avoiding the fasciculations seen with succinylcholine.
Question 28: Which of the following anaesthetic agents causes a rise in the Intracranial pressure:
- A. Propofol.
- B. Thiopentone sodium.
- C. Lignocaine.
- D. Sevoflurane. (Correct Answer)
Explanation: ***Sevoflurane*** - **Sevoflurane** is an inhaled anesthetic that causes cerebral vasodilation, leading to an increase in **cerebral blood flow** and consequently, a rise in **intracranial pressure (ICP)**. - This effect is dose-dependent and can be attenuated by maintaining normocapnia or mild hypocapnia to cause cerebral vasoconstriction. *Propofol* - **Propofol** is an intravenous anesthetic that typically causes a dose-dependent decrease in **cerebral metabolic rate** and **cerebral blood flow**, leading to a reduction in **intracranial pressure (ICP)**. - It is often used for induction and maintenance of anesthesia in critically ill patients with elevated ICP due to its favorable cerebral effects. *Thiopentone sodium* - **Thiopentone sodium** (thiopental) is a barbiturate that significantly reduces **cerebral metabolic rate** and **cerebral blood flow**, thereby **decreasing intracranial pressure (ICP)**. - It is used in neuroanesthesia to protect the brain and lower ICP, particularly in cases of head injury or intracranial hemorrhage. *Lignocaine* - **Lignocaine** (lidocaine) is a local anesthetic that, when administered intravenously, can decrease **cerebral metabolic rate** and **cerebral blood flow**, leading to a **reduction in intracranial pressure (ICP)**. - It is sometimes used as an adjunct in neuroanesthesia for its cerebral protective effects and to blunt airway reflexes, which can otherwise transiently increase ICP.
Question 29: Which of the following anesthetic agents may have cerebroprotective effect:
- A. Ketamine
- B. Etomidate
- C. Barbiturates
- D. All show cerebroprotective effect (Correct Answer)
Explanation: ***All show cerebroprotective effect*** - **Barbiturates**, such as **thiopental**, are known for their profound **cerebroprotective effects** by significantly reducing **cerebral metabolic rate** and **intracranial pressure (ICP)**, particularly beneficial during neurological insults. - **Ketamine** can maintain **cerebral blood flow (CBF)** and **metabolic activity**, potentially offering protection against **ischemic damage** in certain contexts. - **Etomidate** is a short-acting hypnotic agent that can effectively lower **cerebral metabolic rate for oxygen (CMRO2)** and ICP, making it useful for neurosurgical procedures. *Ketamine* - While it can be considered **cerebroprotective** in some situations, particularly by maintaining **cerebral blood flow** and thus oxygen delivery, it is typically associated with increased **cerebral blood flow** and **intracranial pressure** which can be detrimental in cases of head injury or space-occupying lesions. - Its effects on **cerebral metabolism** are complex; while it can decrease overall **metabolic demand**, it can paradoxically increase CMRO2 in certain brain regions. *Etomidate* - **Etomidate** is excellent at reducing **cerebral metabolic rate** and **intracranial pressure**, thus offering protection against **ischemic damage**. - Its **cerebroprotective** properties are primarily linked to its ability to decrease global brain metabolic activity without significantly changing **cerebral blood flow**. *Barbiturates* - **Barbiturates** induce a **dose-dependent reduction** in **cerebral metabolic rate of oxygen (CMRO2)** and **cerebral blood flow (CBF)**, leading to a significant decrease in **intracranial pressure (ICP)**. - This property makes them highly valuable for **cerebroprotection** in conditions like **traumatic brain injury** or **ischemic stroke**.
Question 30: Which of the following drugs is contraindicated in a patient with raised intracranial pressure ?
- A. Ketamine (Correct Answer)
- B. Midazolam
- C. Propofol
- D. Thiopentone
Explanation: ***Ketamine*** - **Ketamine** typically causes an increase in **cerebral blood flow** and **intracranial pressure (ICP)**, making it contraindicated in patients with raised ICP. - This effect is due to its action as a **dissociative anesthetic** which can lead to cerebral vasodilation. *Midazolam* - **Midazolam**, a benzodiazepine, can decrease **cerebral metabolic rate** and **cerebral blood flow**, thereby reducing ICP, making it a suitable option for sedation in patients with raised ICP. - It provides **sedation** and **anxiolysis** without significantly increasing ICP. *Propofol* - **Propofol** is a common choice for sedation in patients with raised ICP because it significantly reduces **cerebral blood flow**, **cerebral metabolic rate**, and thus **intracranial pressure**. - Its rapid onset and offset allow for precise control of depth of sedation and neurological assessment. *Thiopentone* - **Thiopentone**, a barbiturate, effectively reduces **cerebral blood flow** and **cerebral metabolic rate**, leading to a decrease in **intracranial pressure**. - It is often used for inducing anesthesia and as a neuroprotective agent in situations with acute brain injury.
Practice by Chapter
Cerebral Physiology and Pathophysiology
Practice Questions
Anesthetics and Cerebral Blood Flow
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Intracranial Pressure Management
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Anesthesia for Supratentorial Craniotomy
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Anesthesia for Infratentorial Craniotomy
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Anesthesia for Traumatic Brain Injury
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Neuromonitoring Techniques
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Anesthesia for Spine Surgery
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Anesthesia for Neurovascular Procedures
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Awake Craniotomy
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Neuromuscular Disorders
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Postoperative Care in Neurosurgical Patients
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