Neuroanesthesia

Neuroanesthesia Indian Medical PG Question 1: In which clinical scenario would you find a patient requiring the vital signs assessment technique shown in the image?

• A. Pulse absent, breath present
• B. Pulse and breath both not present
• C. Pulse and breath present
• D. Pulse present, breath absent (Correct Answer)

Neuroanesthesia Explanation: ***Pulse present, breath absent*** - The image depicts a **mouth-to-mouth resuscitation** technique, specifically rescue breaths being administered by one person to another. - This technique is applied when a person has a **detectable pulse** but is **not breathing** or is only gasping, indicating respiratory arrest while the heart is still circulating blood. *Pulse absent, breath present* - This scenario would represent **cardiac arrest** where the heart has stopped, but the person is still attempting to breathe. This is a rare, transient state. - In such a case, the primary intervention would be **chest compressions**, not just rescue breathing, as circulation is the immediate priority. *Pulse and breath both not present* - This describes **cardiopulmonary arrest (CPA)**, where both the heart and lungs have ceased functioning. - The appropriate intervention is **cardiopulmonary resuscitation (CPR)**, which involves a combination of **chest compressions and rescue breaths (30:2 ratio)**, not just rescue breaths alone. *Pulse and breath present* - If both vital signs are present, the person is **conscious and breathing adequately**, or unconscious but breathing normally. - No advanced respiratory intervention like mouth-to-mouth resuscitation is needed; the priority would be maintaining their airway and monitoring their condition.

Neuroanesthesia Indian Medical PG Question 2: Increase in ICP is due to:

• A. Procaine
• B. Ketamine (Correct Answer)
• C. Prilocaine
• D. Bupivacaine

Neuroanesthesia Explanation: ***Ketamine*** - **Ketamine** is known to increase **cerebral blood flow** and metabolic rate, which can lead to an increase in **intracranial pressure (ICP)**. - This effect makes ketamine generally contraindicated in patients with pre-existing elevated ICP or neurotrauma. *Prilocaine* - **Prilocaine** is a **local anesthetic** that does not directly cause increases in ICP. - Its metabolism can produce **o-toluidine**, which can cause **methemoglobinemia**, a side effect unrelated to ICP. *Procaine* - **Procaine** is an **ester-type local anesthetic** that primarily functions by blocking nerve impulses. - It does not have a direct mechanism that would lead to increased **intracranial pressure**. *Bupivacaine* - **Bupivacaine** is a **long-acting local anesthetic** commonly used for regional anesthesia. - While it can cause **cardiovascular depression** and **CNS toxicity** in high doses, it does not typically increase **intracranial pressure**.

Neuroanesthesia Indian Medical PG Question 3: Cerebral blood flow is regulated by all, EXCEPT:

• A. Intracranial pressure
• B. Cerebral metabolic rate
• C. Potassium ions (Correct Answer)
• D. Arterial PCO2

Neuroanesthesia Explanation: ***Potassium ions*** - While potassium ions play a crucial role in neuronal excitability and membrane potential, they are **not a primary direct regulator** of cerebral blood flow (CBF) in the same way as other factors listed. - Changes in extracellular potassium can affect vascular smooth muscle, but their direct impact on CBF auto-regulation is less pronounced compared to metabolic or pressure-related factors. *Intracranial pressure* - **Increased intracranial pressure (ICP)** can significantly decrease cerebral blood flow due to the **Monro-Kellie doctrine**, which states that an increase in ICP reduces the cerebral perfusion pressure (CPP). - A sustained and significant elevation in ICP can lead to **cerebral ischemia** as it opposes the arterial pressure driving blood into the brain. *Arterial PCO2* - **Arterial PCO2** is a potent regulator of cerebral blood flow, with **hypercapnia (high PCO2)** causing **vasodilation** and increased CBF. - Conversely, **hypocapnia (low PCO2)** leads to **vasoconstriction** and decreased CBF, which is a key mechanism in the management of cerebral edema. *Cerebral metabolic rate* - **Cerebral metabolic rate (CMR)** is directly coupled to cerebral blood flow, meaning that regions of the brain with higher metabolic activity receive increased blood flow. - This **neurovascular coupling** ensures adequate supply of oxygen and nutrients to meet the brain's metabolic demands.

Neuroanesthesia Indian Medical PG Question 4: Air embolism in neural surgery maximum in which position:

• A. Left lateral
• B. Sitting (Correct Answer)
• C. Supine
• D. Trendelenburg

Neuroanesthesia Explanation: ***Sitting*** - In the **sitting position** for neural surgery, the surgical field, particularly the head, is often elevated above the heart. This creates a **negative pressure gradient** in the venous system, increasing the risk of air entrainment if a vein is opened and air is allowed to enter. - The **higher elevation of the operative site** relative to the right atrium significantly increases the likelihood of air being sucked into open veins. *Left lateral* - While air embolism can occur in any position, the **left lateral position** does not inherently create the same significant negative pressure gradient as the sitting position in the surgical field relative to the heart. - The patient's body is positioned on its side, which can help in certain surgical approaches but typically does not elevate the head as dramatically as the sitting position. *Supine* - In the **supine position**, the patient is lying on their back, and the operative field (head or spine) is generally at or below the level of the heart, reducing the pressure gradient that favors air entrainment. - This position typically offers a **lower risk of air embolism** compared to the sitting position due to less negative pressure in exposed veins. *Trendelenburg* - The **Trendelenburg position** involves placing the patient head-down and feet-up, which increases venous pressure in the upper body and head. - This position actively works against the negative pressure gradient, thereby **reducing the risk of air entrainment** into open veins through increased venous pressure.

Neuroanesthesia Indian Medical PG Question 5: Which inhalational agent increases intracranial pressure most significantly?

• A. Halothane (Correct Answer)
• B. Sevoflurane
• C. Isoflurane
• D. Desflurane

Neuroanesthesia 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.

Neuroanesthesia Flashcard 1 of 5

Question: What is the inhalational anesthetic of choice in neurosurgery?_____

Answer: Sevoflurane

Neuroanesthesia Flashcard 2 of 5

Question: What is the anesthetic induction agent of choice for reducing ICP while maintaining cerebral or coronary perfusion pressure?_____

Answer: Etomidate

Neuroanesthesia Flashcard 3 of 5

Question: Robin Hood or reverse steal phenomenon is the redistribution of blood from normal to ischemic areas in the brain, seen with _____

Answer: thiopentone (IV anesthetic)

Neuroanesthesia Flashcard 4 of 5

Question: _____ is safe to use in head trauma as it is not associated with rise in ICP

Answer: Etomidate::Anaesthetic

Neuroanesthesia Flashcard 5 of 5

Question: In a case of venous air embolism (VAE) during craniotomy, the immediate next step of management is to _____ to limit air entry to chest circulation.

Answer: compress the jugular vein