Administrators at Charles County's only hospital closed down their newest 28-bed unit, laid off 16 nursing aides, clerks, dietitians and engineers and shortened hours for about 40 other workers last week in what was described as a cost-saving plan to stave off a potential $1.2 million loss during the current fiscal year.

Officials of the 131-bed Physicans Memorial Hospital here also instituted a hiring freeze and said additional layoffs have not been ruled out at the 21-year-old facility.

No full-time nurses were laid off and, despite the job cutbacks, the present staff-to-bed ratio of 4-to-28 is still better than the statewide average of 3-to-65, hospital spokesman Mary Stevens Haag said. "The quality of care has not deteriorated," she said.

The cost-saving measures followed several months of declining admissions; administrators said they had calculated that hospital losses were going to greatly exceed the $280,000 predicted earlier for fiscal year 1985.

"Our bed census was nowhere near what we'd projected," Haag said.

The hospital had planned its 1985 operating budget based on an average daily occupancy rate of 91 patients, she said.

But occupancy fell short of that mark. In the quarter ended last September, the hospital operated with an average of 64 patients a day. That is less than half its capacity, said Dennis Phelps, an analyst with the Health Services Cost Review Commission, the state agency that sets hospital room and board rates.

Since that period, more patients have used the facility but not enough to make it cost-effective to keep all beds open, administrators said.

The decision to close the 29-bed wing came just a year after its dedication. The new L-shaped wing was more costly to staff and run than the older circular wings built around central nursing stations, Haag said.

But while staff cuts are being made, the hospital is applying for a $1 million computerized tomography scanner that it says it needs to better serve trauma victims in the heavily traveled Rte. 301 corridor.

Administrators say that without the sophisticated equipment, which makes images of tissues and organs and is used to diagnose spinal, abdominal and brain injuries, the hospital cannot compete with Southern Maryland General Hospital in Prince George's County or Calvert Memorial Hospital in Prince Frederick, Md., the nearest hospitals with the equipment.

"It would increase patient revenues because right now we have to refer patients elsewhere," Haag said.

"We see many many trauma victims from accidents on the treacherous 301 corridor and we have to put some patients in ambulances with a nurse and send them 20 miles up the road."