A DOCTOR is facing accusations of killing more than 300 patients to free up hospital beds.

Virginia Soares de Souza is said to have "played God" administering fatal doses of a muscle relaxant or cutting off patients’ life support, the Mirror reported.

De Souza, who worked at Hospital Evangelico in Curitiba, south Brazil, was initially accused over the deaths of seven patients. But the number soared as checks were made on those who had died in her care over the last seven years.

"We are looking at nearly 300 cases," investigator Dr Mario Lobato told Brazil's Fantastico TV program.

"There are 20 cases which have already been closed, and we have nearly 300 cases still open which we are looking at," Lobato said, the Daily Mail reported.

"In each case, the testimony of people who worked inside the hospital confirmed what we have found on the patient records."

One of the deaths de Souza is accused of is that of Ivo Spiitzer, who was on a life support system and died in January this year.

De Souza is accused of reducing the oxygen he was receiving from 45 per cent to the minimum level of 21 per cent, a concentration too low for anyone to survive.

Records show Mr Spitzer died an hour after being given the drug Pavulon, a muscle relaxant.

In the right dosage Pavulon can be used to allow life support machine to control the patient's respiration, but can also be fatal. It is also one of the drugs administered during most lethal injections.

According to Dr Lobato, the reduction of oxygen and the administering of Pavulon was the cause of most of the other suspicious deaths which occured during De Souza's watch.

"All of them have the same modus operando, the same relationship between the drug and death, and the same time between both," Dr Lobato said.

He said some of the patients were conscious and talking moments before they died.

"One was awake, being nebulised but not even connected to a respirator," he said.

"This patient had asked his family to bring his glasses so he could do some reading while he was in the intensive care ward.

'"Another patient had just asked a nurse for a cup of water.

"This nurse testified that one of the things she will never forget is that she didn't manage to give him the cup of water because by the time she returned he had already died."

If De Souza is found guilty of killing 300 patients she would have become the world's worst serial. English GP Harold Shipman reportedly killed between 215 and 260 people before he was convicted in 2000 of killing "15 patients while working in Hyde, Greater Manchester. Shipman hanged himself in 2004.

De Souza's lawyer, Elias Mattar Assad, said she would prove her innocence.