"This is like emergency medicine," says Terry Fitzgerald. "Nothing happens for a while, and then everything happens at once."

At the moment, Fitzgerald is juggling a pair of "guests" on the "Ask-the-Doc" service of AmericasDoctor.com. Vertical boxes carrying their message traffic are open along the top of the screen. Open across the bottom is the guide to the Web site's online medical reference library.

Fitzgerald has been at the computer for nearly eight hours. His long hair is pulled back in a ponytail. His face has the shiny, haggard look of someone nearing the end of an ER shift, which is his normal line of work.

The "Ask-the-Doc" service is founded on two assumptions about how physicians work. The first is the hoary belief that doctors can answer most questions off the top of their heads. The second is the more contemporary notion that a doctor can provide useful information about a person's medical problems without being a doctor in the traditional sense.

It's a tall order -- especially when you have to do it for two people at once.

The guest from Connecticut recently had surgery for uterine polyps. Today, she started bleeding heavily and called her doctor, who prescribed progesterone tablets.

Will it help? she asks.

Yes, this will cause the uterus to clamp down and expel the blood. The tightening of the muscle will also close off the blood vessels that are or might be oozing.

I was to take them for 90 days. What happens after that? she comes back.

Are you sure you are to take them for 90 days? the doctor queries. One moment please.

Fitzgerald clicks on the reference screen, scrolls through a list of titles and clicks on the 1994 textbook "Current Obstetrical and Gynecological Diagnosis." He searches under "menorrhagia," the medical term for excessive uterine bleeding. An entry comes up that mentions that uterine polyps can cause the problem. But there's nothing about the length of progesterone treatment, which is what he's looking for.

He closes the window and moves the cursor to a dialogue box that lists what medical specialties are represented by the dozen doctors working the service with him. He clicks on "ob/gyn" and poses a question: Is 90 days a long time to take progesterone for this problem?

Then it's back to the 35-year-old woman from Mississippi who recently went to the ER for chest pain, and was told there was some "sloping" on her EKG. She wants to know what that is, and he gives her a brief explanation. Then she asks whether a heart murmur could cause the pain.

If there is mitral valve prolapse, it can (in a way we do not understand) cause chest pain, he says. MVP can cause a murmur.

Fitzgerald checks back to see if the gynecologist has answered his question. He hasn't.

I am sorry. I want to check the range of doses. That is the reason for the delay, he messages the woman in Connecticut.

Will esophageal spasms cause my chest to feel as though an elephant has sat on it? the woman from Mississippi asks. Fitzgerald sighs softly.

"One thing, this is not like taking a [medical] history," he says. "I don't have to stay on my topic. It's their topic. It's their questions. Unless there's something they really need to consider."

But that's unlikely to be the case here. Chest pain in 35-year-old women almost never has a life-threatening cause, and there's no dire warning he must give her.

Absolutely, Fitzgerald answers. Can give symptoms very much like heart pain. Sometimes identical to heart pain.

I will have the heart test done in 3 weeks. All of them, the woman writes. I feel so weak most of the time. Is that normal for spasms?

That is hard to say, the doctor tells her. I cannot evaluate, diagnose or give specific recommendations, but if you feel worse, it would be appropriate to be seen again before those 3 weeks.

Okay, thank you. This has answered my questions. I appreciate your time.

Then it's back to the woman with polyps. It has been eight minutes since he posed his question to the gynecologist, who it turns out has just returned from a break and left an explanation of why bleeding can occur. He doesn't have a clear-cut answer to duration of progesterone treatment. But the guest has raised another issue.

My question is putting off a hysterectomy.

It is probably too early to consider that, Fitzgerald replies.

"It's gotten too complicated," he says aloud.

Then what happens after the 90 days? Won't the same happen after each period?

Not necessarily. In fact, it probably will not be the case.

Then I should try this medicine?

The medication will keep you from having [a] period for that time. Hopefully, the uterus will have "settled down by then." I cannot say what you "should" do. I don't know your case well enough. But I hope that the information I have shared will be of help, Fitzgerald says.

Okay, thank you.

In a minute, there are two more cases on the screen.

The "guests" in these stories gave The Post permission to quote their discussions.