Oh, well... let the expert answer this one. I worked in a drug testing laboratory as a lab tech. A "genius" decided that Drano would clean him out so that we could not detect his THC addiction. In short, he did just what you said.

Here is what happened:

He began with gagging. (The strong base was neutralizing his stomach acid with amazing speed.) He then began vomiting blood... not that fluid liquid blood, but chunky near black blood with chunks of his stomach inside. (The stomach lining quickly breaks down and the stomach goes into spontaneous contractions to prevent irreversible damage to the intestines.) Now, his eyes were blood-shot and leaking blood. (This is due to the force at which he was vomiting. He hemorraged his eyes.) He then began an uncontrollable nose bleed. (Unfortunately, in this case, the nose and mouth are actually connected.) The EMT's pushed me out of the way at this point. Therefore, no more first hand story. (Oh, he lived.)

OK, here is what you will see/feel. Your stomach will begin to dissolve and you will vomit without control. This will go on for several minutes. Blood will come out of your mouth, nose, and eyes. You will also spend a few weeks in the hospital if you survive the initial encounter.

Permanent Damage (if you survived):

1. Ulcer medication for the rest of your life (if the damage is not allowed to continue for long).

2. IV fluids and nutrients for the rest of your life (if the damage is allowed to continue for long).

3. Surgical shortening of the small intestine (if it gets into the small intestine).

4. Inability to smell for the rest of your life.

5. Blindness if the back splash gets into your eyes.

6. Blindness due to the hemorraging.

In the case of the example, numbers 1, 3, and 4 happened.