**Question:** Which of the following anaesthetic agents leads to increase in ICT?

A. Propofol
B. Ketamine
C. Thiopentone
D. Sevoflurane

**Core Concept:** Intracranial pressure (ICP) is a measure of the force exerted by the contents of the skull on its walls. Increased ICP can lead to brain damage or herniation if not managed appropriately. Anaesthetic agents can affect the central nervous system (CNS) and influence ICP.

**Why the Correct Answer is Right:** Propofol is a short-acting intravenous anaesthetic agent that primarily acts on the GABAA receptors in the cortex. It increases the threshold for the generation of action potentials, leading to a reduction in neuronal activity and CNS depression. This decrease in CNS activity results in a decrease in ICP.

**Why Each Wrong Option is Incorrect:**

B. Ketamine: Ketamine is a dissociative anaesthetic agent that acts on N-methyl-D-aspartate (NMDA) receptors, leading to a complex effect on the CNS. In high doses, it can increase ICP due to its effect on NMDA receptors and the resulting increase in neuronal activity.

C. Thiopentone: Thiopentone is an intravenous anaesthetic agent that primarily acts on the GABAA receptors in the CNS. It also has some effect on the GABAB receptors and NMDA receptors. Its primary effect is also a decrease in CNS activity, leading to a decrease in ICP.

D. Sevoflurane: Sevoflurane is a volatile anaesthetic agent that primarily acts on the GABAA receptors in the CNS. Like propofol, sevoflurane also decreases neuronal activity, which results in a decrease in ICP.

**Clinical Pearl:** When managing patients with increased ICP, choosing an anaesthetic agent that primarily targets GABAA receptors, like propofol and sevoflurane, is crucial to decrease CNS activity and subsequently reduce ICP. Avoiding agents like ketamine, which can increase ICP due to its effect on NMDA receptors, is also essential.

**Explanation:**

Propofol is a short-acting intravenous anaesthetic agent that primarily acts on GABAA receptors in the cortex, leading to a decrease in neuronal activity. By reducing the excitability of neurons, propofol causes a decrease in intracranial pressure (ICP).

The other options, namely thiopentone, ketamine, and sevoflurane, all have effects on GABAA receptors, which also leads to a decrease in neuronal activity and subsequently a decrease in ICP.

**Why Each Wrong Option is Incorrect:**

Ketamine is a dissociative anesthetic agent that acts on NMDA receptors, which are involved in learning, memory, and sensory perception. By stimulating NMDA receptors, ketamine increases neuronal activity and thus, can lead to an increase in ICP.

Thiopentone is an intravenous anesthetic agent that targets GABAA receptors, leading to a decrease in neuronal activity and subsequently a decrease in ICP.

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