Maine health-care providers braced for the possible loss of hundreds of skilled workers Wednesday, after President George Bush signed an order calling up as many as 200,000 part-time military personnel to active duty.

While the order authorizes Defense Secretary Richard Cheney to activate any personnel that may be required, medical specialists are expected to be among the first to be called into service. Reservists provide more than two-thirds of the military’s medical support personnel and three-quarters of its medical evacuation crews.

Apparently, no local reservists were ordered to full-time service Wednesday. But four military units based in Maine are among the most likely to be activated. Altogether, the units are believed to have almost 700 personnel, the majority of whom are state residents.

In addition, an uncertain number of Maine residents serve in reserve medical units based out of state.

Capt. Peter Rogers, public affairs officer at the state Army National Guard headquarters in Augusta, said about 305 Maine Guardsmen serve in medical fields.

The 112th Medical Co. in Bangor has 211 members, according to Rogers. An air-ambulance company, it operates UH-1H utility helicopters on medical-evacuation and rescue missions.

Maine also has a ground-ambulance company. Rogers said the 314th Medical Co., with units in Millinocket and Gardiner, has 94 Guardsmen on its roster.

As of late Wednesday, Rogers had no word of any Maine Guardsmen being called to active duty.

In addition to the National Guard companies, the Army Reserve has two medical units in Maine that could be called into full-time service.

Sgt. 1st Class Gerald Cloutier said there are about 260 reservists in the 1125th Army Hospital, which has its headquarters in Auburn and a section in Bangor.

Cloutier, the supervisory staff administrator for the 1125th, said the Army Reserve unit has about 45 doctors from across the country on its roster. About 12 of the physicians live in Maine.

The unit also has about 50 nurses, most of whom are Maine residents, according to Cloutier. In addition, it has more than 150 other medical specialists, from laboratory personnel to emergency medical technicians.

Maine also is home to Section 1 of the 351st General Hospital, an Army Reserve unit based at Hanscom Air Force Base in Massachusetts. Staff Sgt. Gerald Fecteau said the hospital section, located in Saco, has about 115 medical personnel — many of them nurses.

“We still haven’t heard anything (about the possible call-up),” said Fecteau, a personnel administration specialist with the 351st. “Sitting back and not knowing is worse than knowing.”

Many members of the unit had called in recent days to find out how a call-up would affect them, according to Fecteau.

“For some of them, it (the Army Reserve) is their lives,” he said. “They are looking forward to a chance to use their skills. Others are not so happy.”

Neither Cloutier nor Fecteau was aware of any Maine units being called up on Wednesday.

Among the nurses assigned to the 351st General Hospital is 1st Lt. Dorothy Williams of Orrington. A grandmother who joined the Army Reserve two years ago, Williams said she received a letter from the Office of the Surgeon General on Monday inviting her to volunteer for a three- to six-month tour on active duty.

If Williams volunteers, she would be allowed to choose where in the United States she would like to be stationed. If the 351st is activated, however, the hospital is expected to be sent to England for an indefinite period.

Williams had not decided if she would volunteer. She said she was torn between feelings of duty to her country and the financial and personal worries that would come from leaving her job and family.

If called to active duty, however, Williams said she would go.

“I will do my time wherever the tour is,” she said.

Williams is one of at least 24, and perhaps as many as 50, employees of Eastern Maine Medical Center, Bangor, who are members of the reserves. Most of the reservists are nurses, according to Lynn Wood, a hospital spokeswoman.

“We’d certainly have to make some adjustments (if they were called up),” said Wood. “Medical personnel are highly trained. But we really don’t have … a high nursing vacancy rate, so I think the hospital would be OK.”

St. Joseph Hospital, Bangor, has at least six nurses, and an unknown number of doctors and other personnel, who are part-time military personnel. John Supranovich, a spokesman for the hospital, said that St. Joseph was faced with the loss of a seasoned emergency-room nurse and other important staff members.

“We have enough people to handle it,” said Supranovich. “But you’re always going to feel a pinch.”

A call-up of reservists could affect the Veterans Administration hospital at Togus more than any other Maine health-care facility. James Simpson, a public affairs officer at Togus, said the hospital had more than 100 reservists on its 1,100-person staff.

The reservists include five doctors, 12 nurses and 17 other medical specialists, according to Simpson.

“It’s difficult to say what impact a call-up would have,” he said. “It wouldn’t be easy; we’d have to make some adjustments.”