A 24-year-old registered nurse was indicted on four counts of first-degree murder yesterday in the mysterious deaths over the last two years of four patients in the intensive care unit of Maryland General Hospital in Baltimore.

The Baltimore grand jury indictment of Mary Rose Robacznski capped a four-month investigation into the deaths, which were apparently caused by someone turning off respirators that were sustaining the patients, who were all in their 40s.

Robacznski, who was indicted under her maiden name, Mary Rose Kaisler, was released on personal recognizance pending a preliminary hearing Sept. 6.

According to George Helinski, Robacznski's attorney, the nurse "resigned in March of this year shortly after the hospital said there was an investigation."

A 1975 graduate of Maryland General's school of nursing, Robacznski at one time worked in the hospital's intensive care unit," Helinski said.

According to Baltimore State's Attorney William A. Swisher, Robacznski has not worked as a nurse since leaving her position at the 365-bed private, nonprofit hospital.

Swisher said yesterday the investigation was begun after Maryland General officials reported the series of "suspicious deaths" to his office.

The prosecutor and the hospital refused to release any information about the nature of the victims' illnesses, their chances of recovery prior to their deaths or the manner in which they died.

At the time the investigation was begun, however, hospital officials said the deaths involved the shutting off or disconnecting of respirators. Helsinski said yesterday he knows "that's what the investigation involved. Whether they're alleging these are the same patients, I don't know."

Yesterday's indictment did not specify the cause of death, Helinski said, but alleges only that his client "willfully and with malice" murdered Markene Smith, 45, Catherine Womack, 40, Louvenia Reed, 49, and Harry Gessner, 48, all of Baltimore.

Swisher, at a press conference, said "we know many things, but we can't tell them in public . . . We have That will have to be proven at trial." a motive, but we can't discuss that.

He said the body of one of the four was exhumed for an autopsy within the past two or three weeks, but would not say which one.

According to Swisher, the most recent victim was Gessner, who died March 8 of this year. He said Smith died Dec. 26, 1977, Womack died Jan. 5, 1978 and Reed died nine days after that.

Asked if the cases involved "mercy killing," Swisher would only say that "we don't have a crime called 'mercy killing.' Our crime is murder."

Helinski said his client maintains she is innocent and intends to go to trial rather than plea bargain.

The case is the third nationally within 13 months involving a series of deaths in a hospital.

Last July two nurses were found guilty of conspiring to poison hospitalized veterans at a VA hospital in Ann Arbor, MIch. Their conviction was later overturned by a federal judge who cited "numerous improprieties" by the prosecutor, and the government then dropped the charges.

The other case is that of Dr. Mario Jascalevich, who is now on trial accused of murdering three patients at a New Jersey hospital in 1965 and 1966.