Neuroanesthesia Practice Questions

Q: 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?

Venous air embolism. ***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.

Q: 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

1, 2 and 3. ***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.

Q: Anesthetic agent contraindicated in raised ICT is?

Ketamine. ***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.

Q: Which of the following is the best cerebroprotective drug?

Thiopentone. ***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.

Q: Thiopentone has cerebroprotective effect because of –

Decrease cerebral metabolism. ***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**.

Q: All of the following decrease cerebral blood flow and intracranial pressure except:

Ketamine. ***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.

Q: Increased intracranial pressure occurs with:

Succinylcholine. ***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.

Q: Which of the following anaesthetic agents causes a rise in the Intracranial pressure:

Sevoflurane.. ***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.

Q: Which of the following anesthetic agents may have cerebroprotective effect:

All show cerebroprotective effect. ***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**.

Q: Which of the following drugs is contraindicated in a patient with raised intracranial pressure ?

Ketamine. ***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.

Question 1

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?

Accepted Answer

Venous air embolism

Answer

Trauma to respiratory center

Answer

Dislodgement of endotracheal tube

Answer

Wearing off effect of inhalation anesthesia

Question 2

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

Accepted Answer

1, 2 and 3

Answer

2, 3 and 4

Answer

1, 2 and 4

Answer

1, 3 and 4

Question 3

Anesthetic agent contraindicated in raised ICT is?

Accepted Answer

Ketamine

Answer

Thiopentone

Answer

Etomidate

Answer

Sevoflurane

Question 4

Which of the following is the best cerebroprotective drug?

Accepted Answer

Thiopentone

Answer

Propofol

Answer

Etomidate

Answer

Ketamine

Question 5

Thiopentone has cerebroprotective effect because of –

Accepted Answer

Decrease cerebral metabolism

Answer

Calcium channel blockage

Answer

Reduction of vasospasm

Answer

Free radical removal

Question 6

All of the following decrease cerebral blood flow and intracranial pressure except:

Accepted Answer

Ketamine

Answer

Thiopentone

Answer

Propofol

Answer

Etomidate

Question 7

Increased intracranial pressure occurs with:

Accepted Answer

Succinylcholine

Answer

None of the options

Answer

Rocuronium

Answer

Vecuronium

Question 8

Which of the following anaesthetic agents causes a rise in the Intracranial pressure:

Accepted Answer

Sevoflurane.

Answer

Propofol.

Answer

Thiopentone sodium.

Answer

Lignocaine.

Question 9

Which of the following anesthetic agents may have cerebroprotective effect:

Accepted Answer

All show cerebroprotective effect

Answer

Ketamine

Answer

Etomidate

Answer

Barbiturates

Question 10

Which of the following drugs is contraindicated in a patient with raised intracranial pressure ?

Accepted Answer

Ketamine

Answer

Midazolam

Answer

Propofol

Answer

Thiopentone

Neuroanesthesia — MCQs

Neuroanesthesia — MCQs

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