Gradually, as more time passed, the cold penetrated deeper and her brain stopped sending impulses to tell her lungs to keep breathing. Finally, all the tiny chemical factories were at a standstill. By this time, Brittany had no pulse and was lying in the snow with her eyes closed. When cells are up and running, they constantly draw in the chemicals they need and push out the ones that are harmful. But when cells shut down, this careful chemical balance is ruined.
Calcium compounds come flooding in, triggering toxic reactions.
Sodium also seeps in, bringing water with it, which makes the cells start to swell. The condition that triggers these changes is known as ischemia, and it's often fatal. Eventually, ischemic injury occurs, meaning that cells are literally poisoned from the inside. But in Brittany's case, the low temperature protected her. Ischemic injury still developed, but much more slowly.