A woman's voice crackles on a loudspeaker: "Clear the hall, there's a patient coming through."

For a few seconds, as medical attendants whisk past with a patient on a gurney, a pathway is cleared. In their wake, a dozen or so trauma nurses in pink gowns and plastic caps scurry back out from nooks and crannies they've found amid the boxes of supplies and bales of laundry piled along the cluttered corridor.

It's not a scene from "St. Elsewhere" -- it's the shock-trauma unit at the University of Maryland Hospital, one of the most advanced life-saving facilities in the country. Officials there said the rapidly growing unit is bursting at the seams with patients, supplies and equipment.

"We're not pretty, but we're awfully good," said Kathleen Deasy, spokeswoman for the shock-trauma unit, which is located in a small, four-story building in the University of Maryland Hospital complex.

Last week, officials held a ground breaking ceremony for a new, expanded shock-trauma facility. The new building, located in the same block as the existing one, is expected to open in 1988 and cost $35 million.

Maryland's shock-trauma unit was the nation's first such treatment center when it opened in 1969, and its caseload has grown yearly since then. In summer months, when swimming and boating accidents often cause critical injuries, the occupancy rate in the 89-bed facility averages 103 percent, officials said.

The new unit will have space for 138 patients, twice the area for emergency treatment of new admissions, and three more operating rooms, including one especially designed for retrieving human organs that can be rushed to other hospitals for transplant.

The six-story facility will also be immediately adjacent to the rooftop pad where state police helicopters land with 80 percent of the shock-trauma unit's patients. That proximity, Deasy said, is expected to cut by six minutes the amount of time it takes to get critically injured patients to the unit for treatment.

The legislature approved $21 million for the new unit last spring after a skirmish between the House and Senate over how much of the state's capital budget should be devoted to the center.

During that battle, the staff of the shock-trauma unit took out newspaper advertisements warning readers that the existing center is "critically ill" and that the staff "is at the point of frustration and demoralization" because of inadequate space.

An additional $10 million for construction will be sought in the 1986 legislative session, and $3.4 million for the new building is to come from hospital sources.

The shock-trauma unit offers the most intensive care in the state's highly structured emergency medical system, which was set up in 1973 to rush critically injured patients to facilities that can best treat their individual medical problems. The shock-trauma unit is reserved for the most seriously injured -- about 5 percent of the state's trauma victims.

Shock-trauma unit officials said their patients usually have multiple injuries, often the result of automobile or motorcycle accidents. The average patient's age, they said, is 17 to 19. Seventy-five percent are male and 50 percent have been involved in alcohol-related accidents.

"When they're brought here, they're dying," said Deasy. The unit currently treats about 2,100 patients a year, who stay only until they are well enough to be transferred to regular hospital facilities. In 1984, 89 percent of the shock-trauma unit's patients survived.

Nine other hospitals in Maryland have trauma teams, and there are numerous facilities that specialize in areas of emergency care such as treatment of burns or eye injuries.

A recent study conducted at the shock-trauma unit showed that accident victims in Maryland are 2 1/2 times less likely to die before reaching a hospital than are accident victims in the nation as a whole. Shock-trauma officials say the statistics prove the effectiveness of the emergency medical system.