Capitol Hill Hospital's owners last night closed the facility's emergency room to ambulance patients, despite a court order issued this week aimed at keeping the entire hospital open.

A spokesman for Medlantic Healthcare Group, the owner of the hospital, said yesterday afternoon that it would have to stop accepting ambulance patients at midnight because its emergency room medical staff is insufficient.

When that time came, a physician staffing the emergency room telephoned the city's ambulance dispatcher, as instructed, and asked that ambulances not bring patients to the hospital because of a staff shortage, according to Valerie Gonzalez, a Capitol Hill Hospital nurse and the president of the D.C. Nurses Association.

Two doctors and four nurses were on duty at the time, and medical personnel said six patients were in the emergency room as of midnight. The staffers said the treatment of the six was not affected, and walk-in patients would still be accepted.

Gonzalez said she telephoned the ambulance service immediately after the physician's call and told the dispatcher that there was no staffing problem. But a dispatcher said early this morning that no ambulances would be sent to the hospital until 4 a.m., when the staffing level would be reviewed by Georges L. Benjamin, the city's commissioner of public health.

In the hallway outside the emergency room, about a dozen people gathered to protest the action by Medlantic. Rudy Arredondo, an official with the D.C. Public Health Commission, said the company was showing "contempt for the whole community."

Philip Schneider, a spokesman for Medlantic, said officials of the health care group had reviewed Tuesday's court decision ordering the D.C. health planning agency to require Medlantic to obtain agency approval before terminating its medical-surgical services.

"We believe the ruling is wrong," Schneider said, "and we will aggressively pursue an immediate legal remedy."

The loss of Capitol Hill Hospital's emergency room could put further strain on the District's troubled health care system and may hamper the city's ability to provide medical services to the needy, hospital officials said.

Changes at Capitol Hill, at Seventh Street and Massachusetts Avenue NE, have a ripple effect on the city's hospitals, the officials said.

Capitol Hill has served overflow ambulance patients from the emergency room at D.C. General, the city's public hospital, near Robert F. Kennedy Stadium. Ambulances that cannot deliver patients to Capitol Hill have to go elsewhere, such as Howard University Hospital or Washington Hospital Center, both in Northwest Washington.

Capitol Hill Hospital serves an estimated 400 ambulance patients each month, Schneider said. Although many of them are suffering from routine illnesses, many are victims of accidents and medical emergencies.

Public health commissioner Benjamin learned late yesterday of the hospital plan to stop accepting ambulance patients as of midnight. He was notified in a letter sent by telephone facsimile machine to his office by Medlantic officials.

"If they need to go on ambulance diversion because of concerns about {Capitol Hill's ability to care for} patients, we will put them on diversion," Benjamin said yesterday afternoon. "But that is to get us through the night, until we can sort out the administrative and legal issues."

The letter to Benjamin came at the end of a day in which he visited Capitol Hill Hospital and told officials that they should continue providing full medical and surgical services, including emergency room services, under D.C. Superior Court Judge Gladys Kessler's court order.

The commissioner said he will recommend legal action to require the hospital to comply with the court order.

"We are not supporting the closing of the hospital," Benjamin said. "As the commissioner of public health . . . . I have to deal with the public safety aspects of this. As a government official, I have to assure compliance with the court order."

Carolyn Graham, director of the D.C. State Health Planning and Development Agency, said yesterday that her agency had notified Medlantic that it must secure a certificate of need before it closes any medical-surgical services, as required by the court order.

Medlantic, which says it is losing money on the hospital and wants to convert it to a nursing home with geriatric and psychiatric services, has argued that it already has applied for a certificate of need for the conversion. A decision on that is pending. The corporation contends that a second certificate for the closing of medical and surgical services is unnecessary, but the court ruled that it is necessary under city regulations.

Workers at Capitol Hill Hospital, who viewed the court ruling as a victory that would extend their jobs for at least four months, could be laid off beginning Jan. 12, Schneider said yesterday.