anesthetic, anaesthetic, an aesthetic, an esthetic

Anesthetic or anesthetic ( one word, sometimes spelled anaesthetic ) means a substance used to produce physical insensibility or insensitivity, such as ether, choloroform, or narcotics--
He fought the anesthetic stubbornly, but he lost consciousness anyway.
The dentist uses a topical anesthetic before injecting novocaine.

Anesthetic may also describe the state of being physically insensible or insensitive, or something that causes this state--
It may take several minutes to produce an anesthetic state.
His dentist uses an anesthetic gas, and it hasn't worn off yet.

An aesthetic or an aesthetic ( two words, sometimes spelled an esthetic ) describes something that relates to the sense of the beautiful, or characterized by a love of beauty--
These curtains offend my aesthetic sensibilities. Let's get rid of them.
He is attending a lecture that promises to help him develop an aesthetic sensibility in general, and an appreciation of modern art in particular.

An aesthetic may also mean a philosophical theory of the beautiful, especially what is accepted as beautiful in a particular place, or at a particular time--
He is working on defining an aesthetic for the modern age.
The student wrote an aesthetic for the digital age, and it was published in one of the journals.

Now that you know that, you can say--
"As the anesthetic began to work, he was sure he felt an aesthetic appreciation of the ceiling tiles in the operating room--or maybe it was only the gas."