Which intravenous anesthetic agent is known for providing a rapid onset of action?

Ketamine hydrochloride is recognized for its rapid onset of action due to its unique pharmacological properties. When administered intravenously, ketamine quickly enters the systemic circulation and crossed the blood-brain barrier, which allows it to induce anesthesia within minutes. This rapid action is particularly beneficial in emergency and procedural settings where the fast induction of anesthesia is critical.

Midazolam, while also an effective anesthetic and sedative agent, has a slower onset in comparison to ketamine. It typically requires more time to achieve significant sedation, especially in the context of anesthesia induction.

Fentanyl, primarily an opioid analgesic, does have a rapid onset for pain relief, but it does not induce general anesthesia like ketamine does. It is often used in conjunction with other agents for anesthesia rather than as a standalone anesthetic.

Etomidate is another intravenous anesthetic with a rapid onset; however, its use is more often associated with its hemodynamic stability and minimal cardiovascular effects rather than a primary choice for rapid induction.

Thus, ketamine is especially notable for its quick action in inducing anesthesia, making it the correct answer to the question regarding which intravenous anesthetic agent is known for providing a rapid onset of action.