Which of the following intravenous anaesthetic causes increase in cerebral O2 tension.
**Core Concept**
The question is testing the effect of intravenous anesthetics on cerebral oxygenation. **Cerebral oxygen tension** refers to the partial pressure of oxygen in the brain, which is an indicator of cerebral oxygenation. The correct answer is a type of intravenous anesthetic that increases cerebral oxygen tension, meaning it improves oxygen supply to the brain.
**Why the Correct Answer is Right**
The correct answer is **Propofol**. Propofol increases cerebral oxygen tension by **reducing cerebral metabolic rate** (CMRO2) and **increasing cerebral blood flow** (CBF) without significantly affecting the cerebral vascular resistance. This results in an increase in cerebral oxygen tension, making it a beneficial agent for neurosurgical procedures.
**Why Each Wrong Option is Incorrect**
* **Option A:** Thiopentone is a barbiturate that decreases CMRO2 and CBF, leading to a decrease in cerebral oxygen tension, making it a wrong choice.
* **Option B:** Ketamine is a dissociative anesthetic that can increase CMRO2 and CBF, but it does not consistently increase cerebral oxygen tension; therefore, it is not the correct answer.
* **Option D:** Midazolam is a benzodiazepine that can cause a decrease in CMRO2 but does not significantly increase cerebral oxygen tension; hence, it is not the correct answer.
**Clinical Pearl / High-Yield Fact**
When administering intravenous anesthetics, it is essential to consider the effects on cerebral oxygenation, especially in neurosurgical patients. Propofol's ability to increase cerebral oxygen tension makes it a preferred agent in certain clinical scenarios.
**Correct Answer: C. Propofol**