**Core Concept**
Ketamine has a unique pharmacological profile that makes it an ideal choice for patients with hypotension, as it can increase blood pressure and cardiac output through its sympathomimetic effects.

**Why the Correct Answer is Right**
Ketamine works by blocking NMDA receptors in the central nervous system, which leads to an increase in the release of excitatory neurotransmitters such as glutamate and aspartate. This causes an increase in sympathetic tone, resulting in an increase in heart rate, cardiac output, and blood pressure. Additionally, ketamine has a direct vasoconstrictive effect on blood vessels, further contributing to its hypertensive effects. This makes it a preferred choice for patients with hypotension, as it can help to stabilize vital signs and maintain adequate perfusion of vital organs.

**Why Each Wrong Option is Incorrect**
**Option A:** Propofol is a potent hypnotic agent that can cause significant vasodilation and hypotension, making it contraindicated in patients with hypotension.
**Option C:** Thiopentone is a barbiturate that can also cause vasodilation and hypotension, making it a poor choice for patients with hypotension.
**Option D:** This option is incorrect because ketamine is indeed used for anesthesia in hypotensive patients, making it the correct choice.

**Clinical Pearl / High-Yield Fact**
In critically ill patients, ketamine can be used as a first-line anesthetic agent due to its ability to maintain or increase blood pressure, making it an essential drug to remember in high-stakes anesthesia situations.

✓ Correct Answer: B. Ketamine