Inga Schweitzer, lay on her back on the operating room table, eyes taped shut, tubes and monitor lines crisscrossing her pale body.

With her wild, fuzz of red hair, she looked like an abandoned Raggedy Ann doll, dwarfed by the adults adjusting gauges and inserting needles into her floppy limbs.

Three months after she was born, Inga Schweitzer was undergoing open heart surgery.

As recently as five years ago, children like Inga -- who was born with a hole between the right and left lower chambers of her heart -- usually had to wait for surgery until they were about 4 years old. That wait often caused permanent damage to overworked heart and lungs.

But Inga's operation Wednesday was the 100th such repair procedure performed at Children's 'hospital National Medical Center since 1974, and the 32nd on a child younger than a year.

Open heart surgery is being performed on younger children all the time said Dr. Frank M. Midgley, "as we've found out we can do it safely. He said that as doctors were forced into doing something at a little higher risk, and you realize you can do it," they begin doing it routinely.

Such advances come about, said Midgley, the hospital's chief of heart surgery, because surgeons take a chance and operate on children whose only other choice is death.

In this way, they learn what can and can't be done for such young children.

Because Inga's heart had a hole between its right and left ventricles, oxygenated blood returning from the lungs was simply being pumped back to the lungs without circulating through the body.

Her condition, Midgley said, is like "having a window open in room you're trying to heat with a furnace. The furnace has to keep running to warm the room because the heat's going out the window."

The heart, meanwhile, has to work at four times its normal rate to pump enough blood with oxygen through the body. At the same time, the blood vessels in the lungs swell in size because of their added load.

Before operations like Inga's doctors had a number of ways to treat the condition -- which kills about half its victims before the age of 35 if they go untreated.

Doctors could put a band on the major artery that leads to the lungs, which reduced the load on the lungs; but, as Midgley said, "didn't help the heart."

More recently, children like Inga have been treated with drugs to help the heart work and to reduce the level of fluids in the body until the children were old enough to undergo surgery. But that, too, failed to reduce the strain on their hearts.

And thus on Wednesday, at 9:02 a.m., Inga Schweitzer lay on the table in Operating Room 2 as Frank Midgley walked into the room, his dripping wet hands clasped in front of his chest.

After being helped into his surgical gloves and gown, Midgley stepped up to the table and, with Dr. Phil Guzzetts, his senior resident, began painting Inga from her neck to her pelvis with an orange-red antiseptic solution.

His surgical light hooked up and shining in the middle of his forehead like a Cyclops eye, Midgley picked up a scalpel at 9:13 and asked, "Ready to start?"

Within five minutes, Inga-s tiny chest was opened, the halves of her rib cage held apart with spreaders that looked like a muskrat trap, like a toy compared to those used for adult patients.

As a three-man readied the heart-lung machine, referred to simply as "the pump," Midgley inserted the tubes that would carry Inga's blood from her body to the machine, where it would be cooled and pumped back, bypassing the heart.

By 9:35 Inga's heart lay fully exposed, the pulmonary artery as big as a large adult thumb, about three to four times its normal size. It dwarfed her aorta, which usually is about the same size as the pulmonary artery.

The surgeon then used a needle-like probe to measure the pressure in the chamber of Inga's heart. The pressure in the right ventricle was 63, and in the ventricle 77. If the operation was success, the pressure on the left side would be about twice that on the right.

It took Midgley and the pump team another 23 minutes to prepare both Inga and the pump for the actual procedure. "We're going on bypass," announced Midgley, and Inga's tiny body was turned over entirely to the machines.

"Fire away with cardioplegia," Midgley told the pump operator.

"Giving it now," replied team leader John O'Connell as he started the flow of an ice cold solution, high in potassium, that would quickly chill Inga's heart and stop all electrical activity there. At 10:09 the tiny heart lay still, its temperature reduced to about 61 degrees. The chemicals in the solution, and the temperature, store energy in and preserve the heart.

The procedure itself was anti-climatic taking only 23 minutes.

Midgley sliced through the pulmonary artery, without damaging any heart muscle, and then entered the heart through the artery. He found what he was looking for -- an oval hole about the size of a dime.

Because the hole wasn't round, Midgley did not have to use a patch to close it. Instead he managed to sew the edges together, using tiny bits of white Teflon material to fill the gaps. By 10:32 he could pump some clear fluid into the opposite chamber and announce, "Look at that! Not a drop is coming out. Fantastic!"

The process of rewarming Inga's blood and taking her off the pump took another 20 minutes. "Well," Midgley said to his team as he inserted the pressure probes a second time, "now we get our marks."

The pressure in Inga's right ventricle registered 55, the left 105 -- close to what it should be.

"I'm going to go see my patients now," said Dr. Frank Galioto, Inga's cardiologist, who had been watching the operation.

Seven minutes before noon, the operation was over. What had been a gaping hole in Inga's chest was a thin line crossed by 15 small pieces of tape -- instead of a final layer of stitches.The tape, Midgley said, "will come off in the bath in about two weeks."

"Hello baby," the surgeon said to the sleeping infant as a doctor removed the pale blue and green cloths that had covered her. He stroked her foot and murmured, "Little frog."

About 20 minutes later, after explaining the opration to Eric and Toni Schweitzer, Inga's parents, Midgley told them, "There's nothing I'd change if I had anything to change right now. Everything went as it should." c

Wednesday's ordeal was not the first one for the Schweitzers. When Inga was only a month old, Midgley had removed a build-up of tissue in her aorta, but without having to put her on a heart-lung machine.

"When we realized she had to go through this second operation I was looking forward to it," said her mother. "I knew she wouldn't prosper without it. On one hand, I was dreading it with every fiber, but on the other I was looking forward to having it over with."

The mortality rate at Children's for operations like Inga's is about 10 percent, Midgley said, but the Schweitzers viewed the surgery as a way to end their daughter's suffering, her sweating, her labored breathing, her irritability. She had gained only seven ounces since birth because her malfunctioning heart had sapped all her energy.

"I wasn't dreading the surgery so much as I am seeing her now," said Toni Schweitzer, shortly before going to the Intensive Care Unit to see her daughter. "I know she's going to be in a great deal of discomfort for a while."

But by the end of this week Inga was off the respirator and breathing on her own. She was a hospital spokeswoman said recovering from surgery as expected.