Seven-time Formula One champion Michael Schumacher remained in a medically induced
"We cannot predict the future for Michael Schumacher," said chief anesthesiologist Jean-Francois Payen, who is also in charge of Grenoble University Hospital's intensive-care unit.
He added of Schumacher: "He is in a critical state in terms of cerebral resuscitation," he added. "We are working hour by hour."
Schumacher, who turns 45 on Friday, hit the right side of his head on a rock after falling while skiing with his 14-year-old son Sunday morning in the French Alpine resort of Meribel.
The retired German driver suffered a serious brain injury, even though he was wearing a helmet at the time of the accident, and underwent immediate brain surgery upon arriving at the hospital.
Gerard Saillant, a trauma surgeon who operated on Schumacher's broken leg in 1999, told reporters that the driver's age and fitness could help him recover.
Schumacher has 91 race victories to go with his seven Formula One championships.