Neuroanesthesia — MCQs

Q: Which of the following anesthetic agents will produce decreased EEG activity?

N2O. ***N2O*** - **Nitrous oxide (N2O)**, a volatile anesthetic, typically causes an **increase in EEG activity** or amplitude, rather than a decrease, particularly at subanesthetic concentrations, indicating cortical arousal. - It maintains **cerebral metabolic rate of oxygen consumption (CMRO2)** and cerebral blood flow (CBF) and does not typically produce burst suppression. *Propofol* - **Propofol** generally produces a **decrease in EEG activity**, progressing to **burst suppression** and then an isoelectric EEG at higher doses, reflecting its profound cerebral depressant effects. - It significantly **reduces cerebral metabolic rate (CMR)** and **intracranial pressure (ICP)**, making it useful in neurosurgery. *Thiopental* - **Thiopental**, a barbiturate, profoundly **decreases EEG activity**, leading to **burst suppression** and an isoelectric EEG at increasing doses. - It significantly **reduces cerebral metabolic rate of oxygen consumption (CMRO2)**, cerebral blood flow (CBF), and intracranial pressure (ICP), providing **neuroprotection**. *Ketamine* - **Ketamine** is unique in that it causes a dissociation between the limbic system and thalamocortical system, leading to a **dissociative anesthetic state** characterized by **increased EEG activity** and disorganized patterns. - It **increases cerebral metabolic rate (CMR)**, cerebral blood flow (CBF), and intracranial pressure (ICP), which can be a concern in patients with pre-existing neurological conditions.

Q: Which anesthetic agent is known to increase intracranial pressure in patients with head injuries?

Ketamine. ***Ketamine*** - **Ketamine** can cause a direct cerebral vasodilator effect, leading to increased cerebral blood flow and **intracranial pressure (ICP)**. - This effect makes it generally contraindicated in patients with acute head injuries or elevated ICP. *Propofol* - **Propofol** is known to decrease cerebral metabolic rate and cerebral blood flow, leading to a **reduction in ICP**. - It is often favored in neurosurgical settings for its ability to lower ICP and improve cerebral perfusion pressure. *Etomidate* - **Etomidate** is a short-acting hypnotic agent that can also cause a significant **reduction in ICP** due to decreased cerebral blood flow and metabolic rate. - It is commonly used for induction of anesthesia in patients with head injuries due to its hemodynamic stability. *Ether* - **Ether** (diethyl ether) is an older anesthetic agent that has largely been replaced due to its many side effects, including a tendency to **increase ICP**. - While it can increase ICP, its use in modern anesthetic practice is minimal, and ketamine is a more contemporary concern for this effect.

Practice by Chapter

Cerebral Physiology and Pathophysiology

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Anesthetics and Cerebral Blood Flow

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Intracranial Pressure Management

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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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Postoperative Care in Neurosurgical Patients

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