None of the three could have been in any doubt about the seriousness of the situation. Anna was trapped; her clothes soaked with ice-cold water; the stream carrying heat away from her body. Even in those first minutes her core temperature was beginning to plunge. Torvind called for help on his mobile phone, explaining the life-and-death predicament to the dispatcher.

As doctors, Torvind, Anna, and Marie had many friends and colleagues in the rescue services—the dispatcher among them. Firm in the faith that they would make every effort to expedite an emergency rescue helicopter or a mountain rescue team, Torvind returned to help keep Anna from slipping under the ice.

Forty minutes after first becoming trapped, Anna’s desperate thrashing stopped and her body went limp. The hypothermia, now profound enough to anaesthetise her brain, would soon stop her heart. Another forty minutes passed before rescuers from the bottom of the mountain arrived, carrying with them a more substantial shovel, with a pointed tip that was finally able to break through the covering of ice.

Eighty minutes had passed since Anna had first fallen into the water and her body was pulled clear of the stream limp and blue. She had stopped breathing and was without a pulse.

We call what follows 'downtime'—the period from the moment of cardiac arrest until the point at which spontaneous circulation and breathing can be restored. In that interval, the process of dying begins. Before that comes the 'crash'. If your physiology has crashed, the processes that keep you alive have stopped working.

As the resuscitation effort began on Anna’s body in the shadow of those Norwegian mountains, the challenge she faced looked insurmountable. She had been without a pulse for a long time and her core temperature was perhaps more than 20 degrees lower than it should have been. Torvind insisted that they continue their resuscitation attempts. Just before 8:00 p.m., more than an hour and a half after first falling into the stream, Anna was winched onto a helicopter. The struggle to save her life became a desperate scramble.

When the crew touched down at Tromso University Hospital, Anna’s heart had not beaten for at least two hours. Her core temperature was measured at 56.7 degrees Fahrenheit—42 degrees below her normal core, and lower at that point than any surviving patient in recorded medical history. This was genuine terra incognita. Any attempt to resuscitate Anna further could only proceed in the knowledge that in similar situations past medical teams had always failed.

But the team at Tromso decided to continue. Despite the amount of time that had passed since Anna’s heart had first stopped, there was still the glimmer of a hope that the terrible cold might also have protected and preserved her brain.

Mads Gilbert, the anesthetist leading the resuscitation effort, moved Anna directly to the operating theater. He knew that raising her temperature at this point was going to be a massive challenge. Raising the whole body through those 42 missing degrees would take an enormous amount of energy—equivalent to the boiling of dozens of kettles of water.