**Question:** Which of the following intravenous anaesthetic agents causes a decrease in postoperative nausea and vomiting?

**Core Concept:** Postoperative nausea and vomiting (PONV) is a common complication after surgery, affecting patient comfort and recovery. Anaesthetic agents can have varying degrees of influence on PONV risk.

**Why the Correct Answer is Right:** Propofol (A) is a short-acting intravenous anaesthetic agent that works through the GABA-A receptor-mediated inhibition of the central nervous system. It has been shown to reduce the incidence of PONV compared to other anaesthetic agents due to its faster onset and offset, allowing for a more rapid recovery and reduced time spent in the post-anesthesia care unit (PACU).

**Why Each Wrong Option is Incorrect:**

A. Fentanyl (B) is a potent opioid analgesic used for pain management during surgery. While it provides effective pain relief, it is a strong pro-emetic agent, increasing the risk of PONV.

B. Midazolam (C) is a short-acting benzodiazepine sedative-hypnotic agent. Like fentanyl, it is a potent pro-emetic agent and contributes to higher PONV risk.

C. Thiopentone (D) is a barbiturate anaesthetic agent with a longer duration of action compared to propofol. Similar to the other options, it is a pro-emetic agent and increases the PONV risk.

**Clinical Pearl:** In clinical practice, choosing propofol as the primary anaesthetic agent can significantly reduce the incidence of PONV in patients undergoing surgery, leading to improved patient comfort and recovery.

**Correct Answer:** Propofol (A) is the preferred option for reducing postoperative nausea and vomiting due to its rapid onset and offset, minimizing patient exposure to the PACU and improving overall recovery.