Doctors used a defibrillator twice on Hosni Mubarak when they could not find a pulse, security officials said, in the latest crisis for the ousted Egyptian president since he was sentenced to life and moved to a prison hospital nine days ago.
Officials said the 84-year-old Mubarak was slipping in and out of consciousness and was being fed liquids intravenously.
Mubarak also reportedly lost consciousness several times on Sunday and officials have said he is suffering from high blood pressure, depression and breathing difficulties.
The former strongman has been held in the intensive care ward of Torah prison hospital south of Cairo since he was convicted and sentenced on June 2 of failing to prevent the killing of protesters during the uprising that forced him out of office in February 2011.
His two sons, former heir apparent Gamal and wealthy businessman Alaa, were by his side, the officials said on condition of anonymity because they were not authorized to speak to the media.
The sons are being held at the same prison awaiting trial on insider trading charges, after they and their father were acquitted on June 2 of corruption charges.
Mubarak's wife, Suzanne, visited him on Sunday and, according to the officials, demanded that he be transferred to a better-equipped hospital outside the penal system.
The officials said such a transfer was likely unless Mubarak's health improves.
In his last public appearance at his sentencing on June 2, the bedridden Mubarak sat stoned-faced in the metal defendant's cage in the courtroom, his eyes hidden behind dark glasses.
However, officials said that he broke into tears when he learned that he was being transferred to a prison. It took officials hours to convince Mubarak to leave the helicopter that ferried him from the courthouse to the prison.
Media reports quoted Mubarak at the time as saying the military council who took over after his ouster had deceived him.
"Egypt has sold me out," he reportedly said. "They want me to die here."